Photonic crystals with dynamic switching properties have tremendous potential applications in tunable lasers, biological/chemical sensors, and optical devices. As a building block, poly(N-isopropylacrylamide)(pNiPAm) hydrogel nanoparticles are particularly interesting due to their tunability in volume and size with response to temperature change. However, the use of pNiPAm nanoparticles as a building block has been strictly limited because the crystalline structures are easily destroyed by enhanced thermal fluctuations around their volume phase transition temperature. To circumvent this problem, two stepwise approaches have been proposed in previous studies; polymerization of monomers that are infiltrated through colloidal crystal templates; chemical interlocking of residual surface monomers between colloidal building blocks in crystal lattices. Both methods require several templating techniques followed by post chemical treatments. In this presentation we propose a direct method to assemble thermosensitive pNiPAm nanoparticles into a robust thermoresponsive photonic crystal. We use depletion forces to assemble colloidal particles under high ionic strength condition. The crystals forms spontaneously in the presence of non-adsorbing polymers, which stabilize the crystals against dissociation above the lower critical solution temperature (LCST) of the pNiPAm building blocks. The resulting photonic crystal displays dynamic switching of structural colors across full visible spectrum with temperature change.

During the last decade, as nanotechnology has built up excessively, a branch of it have been investigating reasons behind the coloration effects in biological sources such as pigments and structural coloring both of which currently have equal importance for the production of colored structures. However, beyond essence of this coloration for livings, physical phenomena responsible for them have attracted greater attention. Comprehensively, while pigments function by absorption and emission of specific visible wavelengths, mechanisms accounted for structural coloring observed in nature are associated with optical effects such as interference, scattering and photonic crystals or their combinations. Especially photonic crystals in living systems generally exhibit iridescence and brilliant coloring features, which exist not only for aesthetic beauty but also for camouflage, communication, sensing, and reasons that may still remain unexplored. Biomimicking of these nanostructures provides unmatched opportunities in nano-optics area and promotes design of novel photonic configurations. However, current fabrication methods could not provide mimicking of architectural complexity together with control, ease and economy as observed in nature and required for bio-inspired nano-featured macro-devices. This also accounts for even though there are successful biomimicking examples of 1D and 3D photonic crystals obtained by self-assembly or deposition techniques, more intricate one, 2D photonic crystals observed in nature cannot be replicated yet.
Here we investigate and perform successful nanobiomimicry of rare 2D photonic scheme observed on neck feathers of mallard drake. Our imitation is not limited with optical properties only but material features and architectural complexity are also taken into account. Home-built top-down approach called “Iterative size reduction” [1] is used for biomimicking since it supplies great advantages in terms of fabrication cost, speed and permit to control of final nanofeatured structure fabrication from macroscale. This work also demonstrates first all-polymer 2D solid core photonic crystal works at optical frequencies. Further engineering of photonic crystal fibers result with band-gap tunable coloration which cover whole visible spectrum in single fabrication process. In addition, superhydrophobicity observed on mallard feather is also imitated regarding hierarchical structures made up of aligned photonic crystal fibers.
[1] M. Yaman, Mehmet Bayindir, et al., Nature Materials 10, 494 (2011).

We are working with polymer nanomaterial composites. The materials we work with are inspired by human skin to incorporate functionalities, such as stretchability and self-healing in addition to being mechanically flexible. These materials not only allow the fabrication and demonstration of new types of devices, but also enable more robust performance and durability. I will discuss about these materials and their applications.

Stretchable electronics is a burgeoning field due to potential impactful applications such as sensor skins for robotics and prosthetics and wearable electronics for health monitoring and diagnosis. Effective multiplexing of stretchable sensor arrays can be facilitated by transistor-based active matrices. We have developed stretchable transistors that accommodate large strains (>150%) and are based on elastic components such as carbon nanotube (CNT) electrodes, elastomeric dielectrics, and organic semiconductors. Cost-effective solution processing methods, such as spincoating and spraycoating, have been utilized to suggest the potential for large-scale implementation. Bottom contact electrodes are patterned by spraycoating CNTs through a shadow mask onto a Si substrate and subsequently embedded in an elastomer. The semiconductor is transferred onto the electrodes, followed by spincoating an elastomeric dielectric. Performance characteristics for devices based on poly(3-hexylthiophene) (P3HT) include mobilities above 0.03 cm^2/Vs and an on/off ratio ~10^3. The substrate viscoelastic properties play an important role in determining the time-dependent characteristics of the device, and changes in device performance with cycling is dominated by the viscous relaxation of the substrate. The influence of each component (substrate, electrodes, dielectric, and semiconductor) on the device performance will be discussed.

Cephalopods are known as the chameleons of the sea - they can alter their skin&’s coloration, pattern, texture, and reflectivity to blend into the surrounding environment. Despite much research effort, there are few known strategies (natural or artificial) for emulating the unique dynamic reflectivity and coloration of cephalopods. We have drawn inspiration from self-assembled structures found in cephalopods to fabricate tunable biomimetic camouflage coatings. The reflectance of these coatings can be dynamically modulated between the visible and infrared regions of the electromagnetic spectrum in situ. Our studies represent a crucial step towards reconfigurable and disposable infrared camouflage for stealth applications.

Carbon nanomaterials, such as carbon nanotubes and graphene, constitute a relatively new class of materials exhibiting exceptional mechanical and electronic properties, and are also promising candidates as innovative materials for composites, electronic, sensing, and biomedical applications.
In the last few years, we have been working on the functionalization of nanotubes and graphene, with the scope of making these materials more biocompatible and to make them dispersible in solvents, including physiological solutions, and easier to manipulate.
We will therefore discuss our most recent results on the interaction of carbon-modified surfaces with biological/nonbiological matters, in attempts to offer new solutions to old problems.

Transformative nanomanufacturing routes is used to create single layer crumpled graphene nanoparticles through innovative electrohydromechanical concepts that capitalize on the salient mechanical features, rich surface chemistry and compelling colloidal properties of graphene in a multiscale and synergistic fashion to transcend the boundary for achieving high power density electrochemical capacitive energy storage. The proposed experimental strategies conceptually mimic the nano-emulsions at interfaces to confine the dimensional transitions of 2-D planar graphene into 3-D crumpled nanoparticles and their assembly into unprecedented superstructures, establishing a paradigm shift in synthesis and processing of crumpled graphene structures at nanoscale. Specifically, the work presented here enables the experimental isolation of single-layer crumpled graphene nanoparticles that first and foremost yield access to fully explore of exceptional “intrinsic material properties”, especially those pertinent to energy applications such as specific surface area, packing density, intrinsic capacitance, porosity, and ionic permeability.

Conjugated polymers are widely used in organic photovoltaics, biomedical interfaces, and chemical sensors for their reasonably high conductivity and relatively “soft” mechanical properties. Here we examined several polythiophene systems, including poly(3-hexylthiophene-2,5-diyl) (P3HT) and side group functionalized poly(3,4-propylenedioxythiophene) (PProDOT) derivatives by fabricating them into highly ordered polymer nanofibers via electrospinning. To facilitate the solution processing of the otherwise dilute and low viscosity conducting polymers, another relatively easy-to-process supporting polymer was introduced into the fabrication by either blending together with conjugated polymers or using a coaxial electrospinning setup. Macroscopically-aligned fibers were collected on substrates with an air gap of controlled geometry. Morphological results from electron microscopy confirmed that conjugated polymer nanofibers were obtained after solvent removal of the supporting polymer. Molecular orientation studies revealed the existence of preferred orientation between molecular backbones and the nanofiber axes, depending on specific electrospinning system. The electrical and mechanical properties of the conjugated polymer nanofibers were also investigated both macroscopically and microscopically.

Nowadays, the printed circuit boards (PCBs) are widely used in every electronic device as numerous kinds of forms with variety in their shapes, sizes and materials. As the next-generation flexible electronic devices, the flexible PCB systems have been researched and developed in various ways by designing flexible PCB itself or having unibody structure composed of both flexible inter-connectors and PCBs. We present a cost-effective stretchable inter-connection that can be readily used for PCBs fabricated by existing manufacturing process. We introduce a stretchable PCB inter-connection allowed by highly flexible silver nanowires (AgNWs) electrode on polydopamine-treated PDMS substrate[1, 2]. Optimized meander structure keeps silver nanowire&’s percolation for maintaining high conductivity during stretching experiment. The application of inter-connection on PCBs do not require sophisticated methods but only the non-soldering simple attachment and the promising stretchable capability of the inter-connection will broaden the applications of inter-connection with PCBs such as wearable PCBs.


[1] T. Rai, P. Dantes, B. Bahreyni and W.S. Kim*, “Stretchable RF Antenna with Silver Nanowires” IEEE Electron Device Letters 34, pp.544-546 (2013).
[2] T. Aktar, and W.S. Kim*, “Reversibly Stretchable Transparent Conductive Coatings of Spray-deposited Silver Nanowires” ACS Applied Materials & Interfaces, 4, pp.1855-1859 (2012).

Nature fascinates scientists with remarkable livings and creatures. Insect eyes, gecko foots, or lotus leaves inspire science with their multi-functional surfaces and a number of lithography techniques have been developed to fabricate these bio-inspired architecture; paraboloid, triangular, cylindrical, or conic structures on behalf of use in optical and electronic applications.
In this study, we produced biomimetic nanostructures. Proposed facile method for large-area production, utilizes reusable silicon molds and drop casting at ambient conditions to overcome complex environment requirements and multistep fabrication processes. Anodized aluminum oxide (AAO) membranes are used as mask during plasma etching and tapered nanopores are formed at desired lengths with high packing density on silicon molds. Polymer nanostructures are produced by drop casting of polymer solution directly on the silicon molds. Polycarbonate (PC) is chosen due to its high-transmittance, biocompatibility, durability, high impact resistance, and wide usage in electronic components. The fabricated polymer films demonstrate promising qualities in terms of antireflective, hydrophobic and surface enhanced Raman spectroscopy (SERS) features. In order to obtain maximum antireflection performance, design parameters of the 3D nanostructures are simulated using FDTD method prior to fabrication process. Inductively coupled plasma (ICP) etch conditions (i. e. process duration and pressure) are optimized for obtaining desired lengths and structure profile. We achieved up to 92% transmission from single-side nanostructured polymer films by implementing optimized nanostructure parameters. Besides the antireflection feature, produced tapered structures exhibit highly hydrophobic properties (145° water contact angle). We also demonstrated our nanostructured polymer surfaces as stand-free SERS substrate and observed 4.9 x 10⁶ enhancement factor in average SERS experiments.¹ A prominent feature of our facile fabrication method is its versatile nature that it can allow the production biomimetic nanostructures from different kinds of polymers and other moldable materials.
[1] J. Mater. Chem. C, 2013, DOI: 10.1039/C3TC31616E

Protein based polymers (PBPs) are valuable for biological research because of their intrinsic biocompatibility. Additionally, they can be designed and customized as needed to contain functional groups to interact with organic as well as inorganic materials. In this work, we utilize elastin-like polypeptides (ELPs) to create stimuli responsive hydrogels. ELPs, derived from natural elastin, are able to undergo coacervation based on conditions such as temperature, pH, and salt similar to tropoelastin in addition to being highly elastic. We also genetically engineered ELPs with an aromatic amino acid containing sequence, previously found in our lab to bind carbon nanotubes, to enable ELP to physically bind reduced graphene oxide (rGO) nanosheets. The rGO nanosheets act as photothermal heaters absorbing near infrared (nIR) light to produce heat. Using rGO nanosheets and ELP, we have designed fast and controllable light-responsive composite hydrogels.
These composite hydrogels heat up upon exposure to nIR light causing ELP chains to collapse. Anisotropic structure of the gels with porous and solid layers allows for different swelling/deswelling ratios for across the gel and causes them to ‘flex&’. The focus of our work has been to characterize the structure and function of these gels with varying compositions of rGO, ELP and the crosslinking agent. We use atomic force microscopy to observe the hydrogel micro-structure and characterize surface mechanics. Additionally, we characterize the bending of gels by measuring forces generated as the gels are stimulated by laser. Such hydrogel actuators have applications in drug delivery, biophysics, and soft robotics.

The mechanical properties of biomaterials at the micro-scale have become increasingly important in the investigation of cellular behavior at the cell-substrate interface [1]. At this interface, biomaterials exposed to physiological environments immediately adsorb protein before cellular adhesion can occur through a complex process in which cells exert force on the biomaterial to probe the surface [2,3]. This interaction is one of many reasons why understanding mechanical properties is important in the design of biomaterials. While the influence of the elastic component of mechanical properties on cells has been investigated previously, it has been difficult to detect the influence the viscous component of a biomaterial has on cellular activity.
Microgels are colloidally stable, hydrogel nano- or microparticles that have previously been used in biomaterial applications due to their tunable mechanical and chemical properties. In this work, we employ microgels composed of the monomer N-isopropylacrylamide, the co-monomer acrylic acid, and the cross-linker N,N&’-methylenebisacrylamide or poly(ethylene glycol) diacrylate. Microgel films have been constructed from anionic microgels and polycations such as poly(diallyldimethylammonium chloride) and polyethyleneimine, using a layer-by-layer method.
Using these microgel-based films, we demonstrate the ability to modulate the viscoelastic mechanical behavior of film assemblies by means of chemical cross-linking [4]. We have interrogated the films&’ macro-scale mechanical properties, such as self-healing, via the application of controlled, uniaxial stress and subsequent exposure to water. While uncross-linked films are able to self-heal, exhibiting plastic deformation, cross-linked films do not self-heal, exhibiting brittle cracking. We have also interrogated micro-scale mechanical properties of films via atomic force microscopy nano-indentation. Upon cross-linking, films exhibit an order of magnitude increase in Young&’s modulus.
Protein adsorption studies show that fibronectin adsorption increases with layer number and cross-linking; all films except for those made of poly(ethylene glycol) diacrylate exhibit relatively high protein adsorption. However, fibroblast adhesion studies reveal that cell number and cell spreading are not commensurate with protein adsorption. Monolayers and cross-linked films exhibit increased cell numbers and cell spreading in comparison to other films. These data indicate that the non-adherent properties of microgel films cannot be attributed to a typical non-fouling mechanism and we instead attribute these non-cell-adherent properties of microgel films to their viscoelastic behavior.
1. Bechtle, S. et al. Biomaterials, 2010, 31, 6378-6385.
2. Schakenraad, J. M. et al. Colloid Surface, 1989, 42, 331-343.
3. Rahmany, M. B. et al. Acta Biomater, 2013, 9, 5431-5437.
4. Saxena, S. et al. 2013. Manuscript submitted for publication.

Carbon nanotubes have unprecedented mechanical properties as defect-free nanoscale building blocks for high performance composites, but their potential has not been fully realized in composite materials due to weakness at the interfaces and the poor load-transfer efficiency. Here, we want to demonstrate that through load-transfer-favoring three-dimensional architecture and efficient nanotube interconnects, true potential of CNTs can be realized in composites as initially envisioned. Composite thin membranes with reticulate nanotube architectures show large improvement in strength compared to randomly dispersed short CNT reinforced composites reported before. By further increasing the number of nanotube-nanotube and nanotube-matrix interconnections through ion irradiation, very high mechanical strength (~900 MPa) and elasticity modulus (~25 GPa) were demonstrated in 300-nm thin film composites of in-plane randomly oriented CNTs.
This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

The controlled actuation of soft objects with functional nanocomponents in aqueous environments offers opportunities for stretchable electronics and complex assembled super-structures with unusual mechanical properties. We firstly demonstrate that the symmetry of the surface tension for a Galinstan liquid metal droplet can be broken by continuous electrowetting (CEW) effect when an external potential is applied to the surrounding solution, leading to high speed actuation of the liquid metal droplet in both basic and acidic electrolytes. Later, we coat liquid metal droplets with semiconducting nanoparticles to form so-called “liquid metal marbles”. These liquid metal marbles possess multi-facetted characteristics, as both liquid metal cores and nanoparticle coatings can be independently affected by an electric field. The nanoparticles can readily migrate along the surface of the liquid metal droplet when an external potential is applied; this allows us to study the change of surface tension on the surface of the marble. More importantly, we demonstrate that nanoparticle coating of these marbles offers an extra dimension for affecting the surface tension induced actuation. The coating alters the behaviour of the electrical double layer (EDL) on the surface of the marble, inducing surface tension in a highly asymmetric fashion, thus creating new avenues for inducing asymmetry and actuation behaviours. This significant novel phenomenon, combined with unique properties of liquid metal marbles, represents an exciting possibility for the assembly of multi-functional electro-mechanical superstructures.

Nanosized micelles self-assembled from amphihilic block copolymers are promising carriers for delivery of anticancer drugs. Most anti-cancer drugs have limited water solubility, and short blood circulation in the body systems, leading to frequent administrations. The core-shell nanostructure of micelles allows hydrophobic anti-cancer drugs to be encapsulated in the core, providing increased water solubility, prolonged blood circulation, reduced protein adsorption and recognition by the mononuclear phagocytic system. Nanosize gives rise to accumulation of micelles in tumor tissues based on the enhanced permeability and retention (EPR) effect.
In this study, biodegradable block copolymers of urea- and acid-functionalized aliphatic polycarbonate and polyethylene glycol (PEG) were synthesized and employed to encapsulate anticancer drugs into micelles. The non-covalent interactions formed between the urea/acid groups and drug molecules provided high drug loading levels, nanosize and excellent stability in the blood stream. The micelles were not toxic. They were observed to accumulate in tumor tissues in a mouse breast cancer model. As an example, thioridazine (THZ), which kills cancer stem cells responsible for tumor metastasis and relapse, and an anticancer drug (doxorubicin, DOX) were loaded into the micelles. The drug-loaded micelles were used to target both cancer cells and cancer stem cells via a co-delivery therapy. An increased cancer stem cell population in BT-474 human breast cancer cells was observed after treated with DOX-loaded micelles. However, the presence of THZ-loaded micelles reduced the cancer stem cell population, and enhanced anticancer efficacy of DOX-loaded micelles. In BT-474 xenografts in nude mice, the co-delivery of DOX-loaded micelles and THZ-loaded micelles produced significantly stronger antitumor efficacy than DOX-loaded micelles or THZ-loaded micelles alone. Importantly, the combination therapy reduced the number of cancer stem cells in the tumors. These functional micelles can be used to deliver a variety of anticancer drugs containing amine groups.

For quantified understanding of biological events at a single cell or subcellular level, direct insertion of a nano-scale probe has been attempted for electrical or electrochemical analysis. To minimize cell damage during probe insertion into cells, nanoprobes with high aspect ratio and ultra-sharp tip end is required. Although silicon or metal nanowires are widely used for cell insertion, their fabrication processes are expensive and time-consuming. In this study, we introduce a rapid prototyping method based on silk screen printing and thermal drawing to fabricate vertically-aligned polymer nanoprobe arrays. A parametric study was performed to understand the relationship between the nanoprobe shape and operation parameters such as drawing speed, temperatures, contact time, and dipping depth. Using silk screen printing, a fluorescent dye-mixed polymer nanoprobe array was fabricated on a transparent substrate. First, a 3x3 circular pattern was bored through a polyimide film with laser machining and used as a silk screening mask. After the polyimide film was fixed on a glass substrate, SU-8 2150 mixed with Rhodamine B was poured on the polyimide mask and doctor bladed with a razor blade. Afterwards, the polymer pattern array was soft baked for solvent removal and the film mask was detached. This created 3x3 array of circular patterns of SU-8 2150 on the glass substrate. Thereafter, a tungsten pillar was heated above the glass transition temperature (Tg) of SU-8 2150, and glass substrates were heated just below the Tg. The heated micro pillar was dipped in the heated SU-8 pattern and vertically drawn to desired height. Finally, through the breakage of liquid bridge between the pillar and substrate, polymer nanoprobe structure with high aspect-ratio was fabricated. This resulted in 3x3 array of vertically-alligned nanoprobes with 400 nm in diameter and 20 mu;m height. Multiple nanoprobe insertion into single cells was achieved using algal cells, Chlamydomonas reinhardtii, and their confocal fluorescent images confirmed the nanoprobe insertion into the cells.

Liposomes are tiny spherical capsules with a lipid bilayer shell and an aqueous core and have been used in many applications including gene and drug delivery. Liposomes can be prepared in the size scale of cells with lipid and protein compositions similar to that of natural cell membranes. These liposomes are referred to as giant proteoliposomes and closely mimic cellular membranes. They are, therefore, excellent model systems for studying complex cell surface processes such as the molecular events during the entry of pathogens and drugs into cells. Preparation of giant proteoliposomes with controlled size and composition is, however, challenging and typically requires rather sophisticated instruments.
Here we present a unique and versatile approach for the preparation of uniformly sized giant proteoliposomes without any specialized equipment. In this simple approach, hydrogel stamps first pattern lipids/proteins onto a conductive substrate. The patterned lipids/proteins are then applied for electroformation (hydration and exposure to an AC electric field) of giant (>10 µm) vesicles. Combining the commonly used technique of electroformation with the versatile technique of hydrogel stamping makes it possible to: (i) control the size of the resulting vesicles through adjusting the size of patterned lipid/protein patches, and (ii) incorporate functional membrane proteins in the membrane of giant vesicles.
We demonstrated the capability of the present method to produce vesicles populations with relatively narrow size distribution (38.8 ± 6.72 (mean ± S.D.) mu;m). We applied this technique to prepare giant liposomes from variety of lipid and protein compositions and further confirmed the bioactivity of the integral membrane proteins in these vesicles. The resulting liposomes are attached to the surface in an array format and can be used for the rapid and easy data collection for statistical analysis of membrane processes. Alternatively, these liposomes can be easily detached from the surface in order to produce a large number of giant vesicles with functional proteins. In the detached form, the liposomes can effectively encapsulate materials and provide an excellent tool for studying transport phenomenon across membranes. In addition, the use of adsorbent hydrogel stamps enables rapid production of multiple copies (>30) of a liposome array using minute amounts of lipids/proteins, making this technique attractive for high-throughput applications.
This approach may further be applicable to produce giant polymerosomes that offer increased stability compared to liposomes. This method of production of giant liposomes can, hence, be useful in biomaterials, biotechnology, and biosensing applications as well as in the biophysical fundamental studies.

The development of intelligent materials that can respond to the application of an external stimulus is of major interest for the fabrication of artificial sensing devices able to sense and transmit information about the physical, chemical and/or biological changes produced in our environment. Conducting crystalline organic solids exhibit a variety of interesting chemical and physical properties that could be used for developing such smart materials. However, these organic solids are generally obtained as small and fragile crystals precluding their use in practical devices. If these crystalline organic materials can be deposited or integrated on flexible and transparent substrates and processed employing low-cost techniques their appeal is greatly increased.[1]
Here, it will be shown that by using organic bi-layered thin films, composed of a polymeric matrix with a top-layer formed by a nanocrystalline network of a conducting crystalline molecular charge-transfer salt, is possible to translate the properties of single crystals onto the films yielding flexible, transparent, and thin materials with ultra sensitive piezoresistive properties showing durable, fast and completely reversible responses.[2] These bi-layered films can also be translated into different materials keeping their functionality intact. [3-4] In some cases the sensitivity (response) of such materials are one order of magnitude larger (faster) than most of commercial materials arising from the almost mass-less and composite nature of the thin film that combine the properties of the nanocrystals and the polymer. It is also possible to add to this kind of materials other properties like pyroresistivity and/or hygroresistivity making them real multifunctional materials.[5]
During this presentation a few proof-of-concept experiments with simple prototypes based on such soft nanocomposite polymeric materials will be discussed.
References
[1] M. Mas-Torrent et al., J. Mater. Chem. 2006, 16, 543
[2] R. Pfattner et al, Adv. Mater., 2010, 22 4198-4203
[3] L. Ferreras et al., J. Mater. Chem . 2011, 21, 637
[4] E. Steven et al, submitted, 2013
[5] V. Lebedev et al., J. Mater. Chem. C, DOI: 10.1039/C3TC31513D, 2013

Patterning functional materials is a central challenge across many fields of science. Despite the fact that there are hundreds of commercially available photoresists, the functional diversity amongst these materials is severely limited. In most applications, the photoresist serves the sole purpose of a sacrificial mask or mold; very rarely is the resist material incorporated as a structural element or chemically functional interface. The ability to generate new kinds of chemically functional materials directly via photolithography would enable a host of new applications, for example in microelectromechanical systems (MEMS), microfluidics, patterned biomaterials and artificial optical materials. We recently reported a negative tone photoresist using a photoactivated olefin metathesis catalyst, which can be quickly prepared in a one-pot synthesis from commercially available starting materials.
Olefin metathesis is a robust synthetic methodology that has led to new polymeric materials with many applications, such as drug delivery, organic electronics, and photonic crystals. We recently developed a method of patterning using a ruthenium photocatalyst, PhotoLithographic Olefin Metathesis Polymerization (PLOMP). In this procedure, a latent metathesis catalyst is activated by light to react with the olefins in the surrounding environment. We demonstrate a negative tone resist by using the photocatalyst to crosslink a difunctional ROMP monomer within a matrix of linear polymer. The versatility of ruthenium-mediated olefin metathesis can now be utilized to photopattern a variety of functional materials via PLOMP, advancing the field of photoinitiated olefin metathesis from a curiosity to materials science applicable to mass microfabrication.
These olefin-rich solutions are competent UV photoresists, at both 254 nm and 352 nm. Under 254 nm irradiation, we were able to cure 1-2 micron thick films in 60 to 90 seconds using a benchtop 8-watt lamp. Functional diversity has been incorporated into PLOMP resists in a number of ways, including copolymerization of functional monomers into the linear polymer, and through the introduction of additives into the resist solution. We have successfully incorporated a variety of functional groups into the resist material, including esters, acids, ethers, amines and isocyanates. As well, we have demonstrated direct write lithography to generate 3D nanostructures with unique chemical functionality. We anticipate that PLOMP will enable the development of directly patterned micro- and nanostructures with chemical, mechanical and optical functionality not currently available with existing fabrication techniques.
1) Weitekamp, R.A., Atwater, H.A., Grubbs, R.H. JACS (ASAP) 2013

Recent research in flexible and stretchable electronics has shown remarkable advances along with their increasing applications in the wearable computer and bio-implantable electronics. Among various design strategies for stretchable electronics, positioning mechanical neutral plane and forming curved/serpentine interconnection enabled a stretching of the whole device over 50% via minimizing the strain applied to the active device area. In order to guarantee the mechanical stability, the whole device as well as the interconnections was additionally encapsulated with a thin polymer film.
In this work, we propose a novel design concept of stretchable devices with embedded interconnections in the soft elastomer substrate to reduce the local strain in the active device area. The new 3-dimensional (3D) stretchable substrate consists of relatively rigid island arrays (PDMS with young`s modulus of 615 kPa) for active devices on the both sides of the soft thin film (mixture of PDMS and Ecoflex with young`s modulus of 122 kPa), where the active devices are connected by 3D embedded liquid metal (EGaIn) interconnection. Such design of both-sided integration also increases the density of active devices by two.
Array of four different devices including CNT homo-junction diode, micro-supercapacitor, SnO2 nanowire UV sensor, and micro-LED array, was transferred onto the rigid islands via dry transfer process to form an integrated circuit on the newly fabricated 3D stretchable substrate. Upon stretching of the whole devices up-to 50%, the change of the individual device performance was not noticeable. It is attributed to the relatively small strain applied to the active device area: according to the finite element method (FEM), the local strain of less than 7% in the active device island was estimated while the whole 3D stretchable device was stretched to 50%. Furthermore, bending and twisting did not deteriorate the device performance.
This work demonstrates that our new 3D stretchable electronics design would contribute to the future wearable computer technology and the high density stretchable device application.

Availability of potable water in many parts of the world is becoming increasingly scarce due to many pollutants entering the water supply. The objective of this study was to prepare hybrid PVA-gluten hybrid nanofiber, which is a non-toxic and biodegradable for investigating the extractions of pollutants from water. Electrospinning was used to prepare the fiber mats and TEM, SEM, EDS and FTIR were used to investigate the morphology, elemental composition and functional groups on the surface. Influence of experimental pH, time and concentration of the nanoparticles towards extraction of nanoparticles from water were quantified using UV-Vis spectroscopy. The kinetic and equilibrium adsorption data were interpreted using Freundlich and Langmuir isotherms and adsorption mechanism was investigated to understand the adsorption process. Nanofiber mats with high surface area provided an efficient adsorption for nanoparticle removal from water. Nanofiber mats with 5wt% gluten exhibited a high extraction efficiency of 99% towards citrate capped silver (Ag) and gold (Au) nanoparticles with a maximum adsorptive capacity of 41.5 mg/g for citrate capped Ag nanoparticles and 23.3 mg/g for citrate capped Au nanoparticles. Our results indicate that the prepared PVA-Gluten nanofibers can be utilized as efficient low-cost nano-absorbents for removal and recovery of metal nanoparticles from aqueous environment.
Keywords: PVA, Gluten, Nanofiber, Nanoparticle, Environmental.
Acknowledgement: The authors acknowledge funding support from the National University of Singapore (NUS) and Singapore-Peking-Oxford Research Enterprise, COY-15-EWI-RCFSA/N197-1. Technical support from Department of Chemistry and NUS Environmental Research Institute is also acknowledged.

We report novel cell co-culture platforms based on transparent, nanoporous, and transferable (TNT) polymeric membranes, allowing for controlling interaction types (i.e., paracrine or gap junction signaling) as well as the degree of signaling between co-cultivated cells. Since the TNT polymer membranes were prepared by the non-solvent induced phase separation of cellulose acetate (CA) solutions, pore size and film thickness of the TNT membranes can be easily adjusted, at the sub-micrometer scale, by controlling solvent type as well as solution concentration. The TNT membranes with controlled pore size and film thickness enable us to design precise in vitro analysis platforms to study different types of cell-cell communications. Based on the TNT membranes, we have investigated the behavior of metastatic cancer cells when they were subject to co-culture with three different stromal cell lines (i.e., fibroblasts, myoblasts, and human mesenchymal stem cells) by tracking cytokine-based paracrine signals with different stromal cell type. Furthermore, high flexibility in stacking and destacking of the TNT membranes allowed us to address many issues of conventional cell co-culture methods that lack in identifying the routes for efficient cell-cell signaling or to separate each cell line for further analysis and applications.

The diphenylalanine (FF) motif plays an important role in causing the Alzheimer&’s Aβ polypeptide to self-assemble into fibrils in vivo. These fibrils aggregate to become plaques, which are present in the brains of Alzheimer&’s patients. It is believed that the soluble pre-fibrillar aggregates are toxic rather than the final plaque products. Gazit et al. have shown that FF, when dissolved in water, will self-assemble into peptide nanotubes [1]. These nanotubes are attractive for applications in nanotechnology because they are inherently biocompatible, and have high chemical and thermal stability [2]. It is important to understand the FF self-assembly process in order to help inform strategies for treating Alzheimer&’s disease, and to obtain precise control over the assembly of these nanostructures.
The kinetics of the formation of these structures was studied experimentally while at the same time a multi-scale theoretical approach was followed to describe the assembly and growth of the nanotubes. To this aim, linear dichroism (LD) was used to produce time course data for the formation of these nanotubes. It was shown that 40 °C is a critical temperature in the onset of the assembly. Right-angle light scattering was used to confirm the LD results. Also, structural studies were done with scanning electron microscopy (SEM). These images clearly demonstrated the hexagonal, sometimes hollow nature of the fibres. SEM measurements also allowed us to quantify the fibre size distribution and to determine its dependence on different preparation methods. Finally, molecular dynamics (MD) simulations were employed to determine the origin of the very high aspect ratio of the fibres. The results showed that interactions within hexagonally ordered peptide planes are much less relevant than interactions perpendicular to these planes and thus parallel to the long axis of the fibres. The next step is to move from a thermodynamic explanation to a kinetic model which will be able to describe the experimentally observed growth curves.
References
[1] M. Reches and E. Gazit, (2006) &’Molecular Self-Assembly of Peptide Nanostructures: Mechanism of Association and Potential Uses&’, Current Nanoscience, vol. 2, pp. 105-111.
[2] N. Kol, D. Barlam, R.Z. Shneck, E. Gazit and I. Rousso, (2005) &’Self- Assembled Peptide Nanotubes Are Uniquely Rigid Bioinspired Supramolecular Structures&’, Nano Letters, vol. 5, pp. 1343-1346.

Self collapsing gels are a new type of gels that collapse due to formation of nanoparticles [1]. The formation of the gel is due to electrostatic attraction between Au(III) ions and chitosan. As the ions get reduced and become nanoparticles, the gels collapse due to breakage of bond between neighboring chitosan molecules. They have potential applications in drug delivery. In this research chitosan-gold self collapsing gels were made by adding HAuCl4.3H2O to 1 wt% chitosan solution containing 1.5 wt% acetic acid and then carbon nanotubes (CNTs) were added to the solution. It was observed that the stability of the gel depended upon the concentration of CNTs added. It was also observed that the electrical characteristics of the gel depended upon the concentration of CNTs added. FTIR showed that chitosan-gold-CNTs nanocomposites form. TEM showed that some gold nanoparticles also was found to stick to CNTs. The size of the gold nanoparticles formed on the CNTs was greater than that formed in the solution. This result indicates that CNTs affect the interaction between gold ions and chitosan molecules in the gels. The interaction between CNTs and the self collapsing gels were characterized using FTIR, TEM, rheometer and dielectric spectroscopy. A model is proposed for the formation of these self collapsing gels. It is hoped that this research will advance the applications of self collapsing gels in biomedical engineering and in batteries.
KEY WORDS: CNT, Gold, Self collapsing gels.
References and Notes
1. Radha Perumal Ramasamy, Shihabudheen M. Maliyekkal. New J. Chem., 2013, Advance Article DOI: 10.1039/C3NJ00603D.

We measure the adsorption of sodium dodecyl sulfate (SDS) onto functionalized graphene sheets (FGSs) in an aqueous system at broad SDS and FGS concentration ranges using conductometric surfactant titration. We find that, on FGSs with carbon-to-oxygen ratio of ~18, an adsorbed monolayer reaches full coverage by a bulk SDS concentration of ~12 mu;M. Additionally, the critical surface aggregation concentration (csac) for surface micelle formation is measured to be ~1.5 mM SDS. Using optical microscopy and UV-Vis absorbance measurements along with a simple interaction energy model, we demonstrate the influence of SDS adsorption on the aggregation of FGSs that have been ultrasonically dispersed in aqueous solutions of different SDS concentrations. We find that FGS aggregate morphology depends strongly on the SDS concentration: In the absence of the surfactant, due to the lack of electrostatic repulsion, van der Waals attraction dominates and causes FGSs to form highly-ramified aggregates. As the SDS concentration is increased to ~10 µM, repulsion from adsorbed SDS causes FGS aggregates to develop more compact structures. Additionally, over time ramified aggregates restructure and become more compact via an increase in sheet-sheet overlap area. Above ~10 µM, we find that the dispersed state becomes increasingly stabilized, and above ~40 µM electrostatic repulsion prevents FGS reaggregation for at least a year. Thus, neither surface micelle formation nor dense monolayer coverage of SDS is required to obtain stable aqueous FGS dispersions.

Single walled carbon nanotubes (SWNT) have exceptional charge transport properties making them attractive for next generation of carbon based electronic devices. When placed in contact with a semiconducting polymer such as poly-3-hexylthiophene (P3HT), SWNTs have been shown to exhibit an ultrafast charge transfer process under solar illumination, which holds great promise to enhance the performance of organic based photovoltaic (PV) solar cells.^1-3
Here we demonstrate a new solution based method to produce nano-engineered SWNT networks with improved charge transport in a P3HT matrix at very low nanotube loading. Traditional methods, such as drop casting or spin casting, produce nanotube networks which are random and whose electrical properties are non-optimal. Morever, these methods often produce bundles and require large amounts of nanotubes to form conducting pathways.
The method presented here is simple, controllable, scalable and enables the formation of nano-sized networks with exceptional properties not achievable by any other method. Charge transport was enhanced by at least one order of magnitude at low nanotube loadings compared to other traditional solution based methods. We demonstrate much enhanced electronic properties for both highly purified semiconducting nanotubes, and for a mixture of metallic and semiconducting nanotubes. The low amount of SWNT used reduces bundling, increases transparency and provides an economical solution for electronic applications.
1. Bindl, D. J.; Safron, N. S.; Arnold, M. S. ACS Nano 2010, 4, 5657-64.
2. Bernardi, M.; Giulianini, M.; Grossman, J. C. ACS Nano 2010, 4, 6599-606.
3. Stranks, S. D.; Weisspfennig, C.; Parkinson, P.; Johnston, M. B.; Herz, L. M.; Nicholas, R. J. Nano Lett. 2011, 11, 66-72.

Functional hyperbranched poly(ethoxysiloxanes) (PEOS) represent a new and versatile class of silica precursor. PEOS possess various attractive features such as flexibility to control their hydrophilic/hydrophobic balance, easy incorporation of functional groups and tunable physical and chemical properties determined by the surface groups. In this presentation, various examples of complex composite colloidal architectures formation by using PEOS will be shown.
In the first part, controlled biomimetic deposition of silica inside stimuli sensitive microgels will be summarized. Here, a water-soluble silica precursor PEG-PEOS was synthesized via post-modification of hyperbranched polyethoxysiloxane (PEOS) with poly(ethylene glycol) monomethyl ether (PEG). Poly(N-vinylcaprolactam)-based microgel functionalized with imidazole and β-diketone groups was used as a self-catalytic matrix. Composite microgel particles containing silica nanoparticles (up to 20 wt.-%) have been prepared by simultaneous PEG-PEOS conversion and silica deposition in the microgels.
In the second part, a special crosslinker (Cross-PEOS) was synthesized having both vinyl and PEG groups. Presence of vinyl group provided the crosslinking sites while PEG groups made the crosslinker hydrophilic. Here, the synthesis of degradable thermosensitive PVCL microgels via precipitation polymerization using Cross-PEOS as crosslinker will be demonstrated.
Further in the third part, the fabrication of composite capsules with precise control on size, shell structure and permeability will be touched upon. In this approach, PVCL microgels stabilize the oil-water interface via Pickering emulsion and PEOS act as an interfacial glue to bind these particles by sol-gel reaction. These microcapsules have significant potential for current cutting edge applications like encapsulation and smart coatings.

Hydrate-phobic surfaces are very desirable for flow assurance strategies aimed at reducing the occurrence of blockages in oil and gas pipelines. Initiated chemical vapor deposition (iCVD) is a unique method for copolymerizing reactants with no common solvent into a thin and conformal film and enables grafting of the film to surfaces, providing the robust adhesion required for industrial application. Thin films of bilayer divinyl benzene (DVB)/poly(perfluorodecylacrylate) (p-PFDA) were synthesized via all-dry iCVD technique on steel and silicon substrates. Coated surfaces exhibited receding water contact angle (WCA) higher than 120° and WCA hysteresis as low as 2°. Optical profilometer measurements were performed on the films and root mean square (Rq) values of 18.9±5.4 nm and 105.3±15.3 nm obtained on silicon and steel substrates, respectively. Nanoindentation and nanoscratching measurements were also performed on the assembled bilayer polymer coatings and indicated that the mechanical properties of the films were enhanced through the bilayer structure and the adhesions of the films to the substrates were improved via in-situ grafting mechanism. Strength of ice adhesion to the substrates was evaluated using a custom-built laboratory-scale adhesion apparatus. The strength of ice adhesion was reduced more than four-fold when the surfaces were coated with the iCVD polymer films as a result of the smoothness and low surface energy.

Hospital acquired infections are the fourth most common cause of death in the US. About 65% of these deaths are caused by infections due to adhesion and growth of microbes on medical surfaces. Therefore an efficient method of managing bacterial infections is to control adhesion and colony formation of pathogens on the surfaces through changes in the properties of the surfaces. Previous studies have shown that controlled surface topography can be used to control microbial adhesion to the surfaces. In this work, we have used hexagonally packed colloidal monolayers (HPCMs) of submicron size spheres as a new anti-adhesion mechanism which provides well organized controlled curvature on the surfaces. HPCMs of polystyrene have been deposited on polystyrene surfaces, and characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Films have been prepared from 210 nm, 420 nm, 640 nm and 820 nm particles and with no particles (control). Pseudomonas aeruginosa, PAO1, have been used as the model opportunistic pathogen and films have been exposed to bacteria in a center for disease control biofilm reactor for 1 day at 37oC. The results show that HPCMs will not only result in more than 80% reduction in the number density of cells adhered to the surface but also inhibit cell-cell contact and colony formation while bacteria will make several colonies on the control surfaces. The effect of the particle size and local curvature on microbial adhesion have been investigated and the mechanism for adhesion reduction and colony formation inhibition will be discussed.

Because of their outstanding properties such as emission of linear polarized light with tunable emission wavelength, high absorption coefficients and high photoluminescence quantum yield (PLQY), CdSe/CdS-Quantum-dots-quantum-rods (QDQRs) are favorable markers for bio imaging experiments. Since QDQRs are prepared via the hot injection synthesis by seeded growth, only hydrophobic QDQRs can be obtained. Therefore a phase transfer has to be done.
The seeded growth hot injection synthesis and subsequent phase transfer yielded to QDQRs with an aspect ratio of ~6, a PLQY of around 80% and emission wavelengths between 550 an 620 nm. The phase transfer was achieved via either an encapsulation within a shell of crosslinked PI-b-PEO diblock copolymer or growing a silica shell around the QDQRs for in vivo and in vitro studies.
The strong fluorescence of the water-soluble QDQRs can easily be observed by two-photon laser scanning microscopy (TPLSM) and be clearly distinguished from autofluorescent background after applying them onto the small intestinal mucosa of mice in vivo or by confocal laser scanning microscopy after incubating A549 cells with the QDQRs.
Our results demonstrate that PI-b-PEO encapsulated CdSe/CdS-QDQRs are excellent probes for studying the uptake and fate of nanoparticles by two-photon imaging techniques in vivo and confocal imaging since the PLQY is high enough even under harsh conditions (pH variation and in different biological relevant media).

Silica based microcapsules that contain two or three discreet chemical environments can be prepared by the manipulation of the characteristics of coacervate phases. Coacervate phases are organic and viscous systems which readily phase separate from an aqueous solution. They maintain high degrees of hydration but are able to demonstrate sequestration and compartmentalization from the surrounding aqueous environments. When micron sized droplets of coacervate phases are put into an oil phase they can be stabilized by silica nanoparticles, a system that is analogous to a water in oil Pickering emulsion. When the composition of the coacervate is tuned to minimize the electrostatic interactions between the coacervate phase and the colloidal particles the resulting colloidosomes are stable. Antithetically, when the coacervate phase is manipulated so that the electrostatic interactions between the silica and coacervate are attractive, the interface can be destabilized. Destabilization of the coacervate/oil interface promotes the ingress of oil droplets into the coacervate phase, leading to the formation of micron sized compartments with the colloidosome.
A cross-linking procedure is used to stabilize the microcapsules so that they can be transferred out of the oil phase and into other solvents (including acetone, ethanol & water). Following cross-linking the oil droplets template the creation of internal compartments within the silica microcapsules. The oil templated compartments exist separately to the coacervate phase and confocal microscopy has been used to demonstrate that components can be stored separately. The properties of the resulting complex structures have been characterized by a range of techniques, including confocal microscopy, SEM and µ-CT, and found to contain compartments spread throughout the silica microcapsules. These structures are mechanically tough, while also being porous and capable of entrapping a range of particles & organic species.

Mechanochromic materials are photoluminescent systems that change their emissive properties (wavelengths, intensities, lifetimes) under mechanical perturbation. Common mechanochromic systems typically consist of three classes: (1) pi-stacked conjugated organic small molecules or conjugated ligand-coordinated metal-complexes; (2) such small molecules physically dispersed in a polymer host; (3) small molecule mechanophores covalently attached at specific locations along polymer chains. In system (1), the grinding of small molecules or complexes changes their packing or molecular geometry, thereby altering their optical properties. The small molecules when incorporated in a polymer matrix undergo deaggregation when the polymer is strained, and a change in emission results from the breaking of excimers. These systems pose challenges in processability and precise aggregation control. Mechanophore-containing polymers, on the other hand, require the incorporation of functional groups or bonds prone to rupture upon mechanical activation, which limits the choice of molecules that could be incorporated. In our study, a stable, free-standing polymer blend film that chemically coordinates luminescent transition-metal based nanoclusters through a one-step reaction is demonstrated. The film is shown to exhibit marked mechanochromic properties. This material gives rise to opportunities for innovation in processing and optical sensing.

Polyprolylene is commonly used for crude oil spill cleaning but it has low absorption capacity and non-biodegradable. In our work, a green, ultralight and highly porous material was successfully prepared from paper waste cellulose fibers. The material was functionalized with methyltrimethoxysilane (MTMS) to enhance its hydrophobicity and oleophilicity. Water contact angles of 143 and 145o were obtained for the MTMS-coated recycled cellulose aerogel. The aerogel achieved high absorption capacities of 18.4, 18.5 and 20.5 g/g for three different crude oils RB, TGT and RD at 25 oC, respectively. In the investigated temperature range of 10, 25, 40 and 40 oC for the absorption of RB oil on the aerogel, a highest absorption capacity of 24.4 g/g was obtained. It was found that the viscosity of the crude oils mainly affects the absorption on the aerogel. The strong affinity of the crude oils to the MTMS-coated recycled cellulose aerogel makes it a good absorbent for crude oil removal.

Electrospinning was used to synthesize partially aligned and free-standing silver incorporated carbon nanofibers (CNFs) mat in an easy and cost effective manner by using polyacrylonitrile (PAN) and silver nitrate blend followed by its carbonization. Decomposition of PAN/AgNO3 blend during the carbonization of PAN polymer produces microporous Ag/carbon nanofibers (Ag/CNFs) with diameters in the range of 80-150 nm. The composite fibers are characterized for their morphology, crystallinity, surface area and porosity. In this work we have demonstrated the catalytic activity of the optimized electrospun Ag/carbon nanofiber mats towards the reduction of para-nitrophenol with sodium borohydride. We have also probed the incremental effect of Ag nanoparticles with average particle size ~33 nm over the catalytic activity of carbon mats. Calcinations of the Ag/CNF hybrid fibers produce a bi-continuous structure of silver nanofibers which may find further applications in nanoelectronic and nanoelectro mechanical devices because of their known high conductivities.

Directed self-assembly (DSA) of block copolymers (BCPs) can generate uniform and periodic patterns, and has been one of the promising nanofabrication methodologies for resolving the resolution limit of optical lithography. To realize high-resolution patterns, solvent annealing has shown great effectiveness in promoting the self-assembly of BCPs with a high Flory-Huggins interaction parameter (chi;), which is a measure of the degree of incompatibility between two blocks. However, because high-chi; BCPs have low chain mobility, a long annealing time is required under conventional (room-temperature) solvent annealing. Furthermore, solvent annealing often results in poor line edge roughness from the internal stress within the polymer due to the incommensurate dimension of dried film. In this study, we report that solvothermal annealing is a highly effective method for an ultra-fast self-assembly as well as for producing sharp interfaces between two blocks simultaneously. For solvothermal annealing, well-ordered nanostructures can be easily obtained within a few minutes via thermal assistance and high vapor pressure. Also, lower stress field is produced due to the less compression of cylinder to the perpendicular direction of film because of low effective chi;N at the swollen state. For the extremely rapid self-assembly and sharp interfaces, solvothermal annealing has the combined advantages of high throughput and improved pattern quality. This method will provide a new opportunity for high-chi; BCPs self-assembly.

Ethosomes which are phospholipid vesicular systems embodying ethanol in relatively high concentrations have ever been discovered for enhanced skin delivery of drugs. The development of competent ethosome-like catanionic vesicles for dermal drug delivery is demonstrated in this work. Double-chained ion-pair-amphiphiles (IPAs or catanionic surfactants) were prepared from single-chained cationic and anionic surfactants by the precipitation method. These lipid-like surfactants were thereafter used as the material to prepare the catanionic vesicles with the aid of ethanol as the cosolvent in aqueous buffer solution by a simple semispontaneous process. Formability and physical stability of the as-prepared ethosome-like catanionic vesicles were discussed based on the viewpoint of mixed solvent dielectric constant. The potential application of the ethosome-like catanionic vesicles as nano-carriers in dermal drug delivery was illustrated by the encapsulation of hydrophobic and hydrophilic drugs. Furthermore, effects of ethanol and cholesterol addition on physical stability, bilayer membrane rigidity, encapsulation efficiency, and release rate of the ethosome-like catanionic vesicles were systematically studied. The performance of ethosome-like catanionic vesicles as drug delivery nano-carriers, eventually, can be tailored by the concentrations of ethanol and. cholesterol. The results of gelation of drugs loaded ethosome-like catanionic vesicles by water soluble polymers with and without hydrophobical modifications, as revealed by the phase maps and the rheological properties, then provide useful information for practical use of the ethosome-like catanionic vesicles in dermal delivery of drugs.

Amyloidogenesis is a biochemical phenomenon in which soluble proteins turn into filamentous aggregates known as amyloid fibrils. They were observed as a product of protein misfolding involved in various neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), and Prion disease. But they are now recognized as nano-scaled one-dimensional biomaterials with formidable mechanical strength. Mature amyloid fibrils elicit polymorphism resulted from variations in their molecular-level structure. From a single amyloidogenic protein of α-synuclein, two distinctive amyloid fibrils were formed depending on the fibrillation processes. The polymorphism of curly amyloid fibrils (CAF) and straight amyloid fibrils (SAF) was achieved under different conditions for the fibrillar growth. CAF was produced with the centrifugal membrane filtration of the preformed α-synuclein oligomers, whereas SAF was obtained during the normal agitated incubation of α-synuclein from its monomeric forms. It is demonstrated that the production of CAF and SAF represents two parallel mechanisms of amyloidogenesis via double-concerted and nucleation-dependent fibrillation process, respectively. Differences in their secondary structures of two polymorphs have been suggested to be responsible for the morphological uniqueness with structural flexibility and mechanical strength. CAF and SAF exerted the self-propagation, demonstrating that characteristic fibrillar morphologies were inherited for two consecutive generations to the daughter and granddaughter fibrils. Accumulation of CAF resulted in the formation of protein hydrogel composed of the three-dimensional fibrillar network in fine nano-scale. The amyloid hydrogel was proven to be a suitable nanomatrix for enzyme entrapment, protecting the activity of immobilized enzyme from repetitive catalytic reactions and heat treatment. Therefore, the nano-scaled fibrillar network of CAF is expected to be employed for various future applications in nanobiotechnology including drug delivery, tissue engineering and biosensor development.

Silicon nanomembranes (SiNMs) are soft, freestanding films that have attracted attention as an active semiconductor in flexible devices. Fabricated from Silicon on Insulator (SOI) wafers, these films can be transferred to a variety of flexible substrates[1]. SiNMs have relatively high mobilities due to their monocrystalline structure, making them a candidate for use in high frequency flexible devices[2]. Previous studies have reported microwave frequency SiNM transistors exhibiting fMAX as high as 12 GHz[3]. All previous studies have examined the microwave frequency performance devices in the field-effect transistor configuration. In order to expand the potential applications of flexible SiNM RF technology, a microwave frequency SiNM bipolar junction transistor (BJT) will be reported. Using standard CMOS processing techniques, BJTs are fabricated with base regions as narrow as 200nm. This ultra-narrow base region is achieved using a previously reported self-aligned polysilicon sidewall spacer technique. After fabrication, devices are transferred to flexible substrates by selectively etching the buried oxide layer of the SOI. Microwave frequency data will be presented, along with an analysis of the limiting factors of the devices. Overall signal loss will be examined, and a comparison will be made between devices operated on the growth wafer and after transfer to a flexible substrate.
[1] K. J. Lee, M. J. Motala, M. A. Meitl, W. R. Childs, E. Menard, A. K. Shim, J. A. Rogers, and R. G. Nuzzo, “Large-Area, Selective Transfer of Microstructured Silicon: A Printing- Based Approach to High-Performance Thin-Film Transistors Supported on Flexible Substrates,” Advanced Materials, vol. 17, no. 19, pp. 2332-2336, Oct. 2005.
[2] K. Zhang, J.-H. Seo, W. Zhou, and Z. Ma, “Fast flexible electronics using transferrable silicon nanomembranes,” Journal of Physics D: Applied Physics, vol. 45, no. 14, p. 143001, Apr. 2012.
[3] L. Sun, G. Qin, J.-H. Seo, G. K. Celler, W. Zhou, and Z. Ma, “12-GHz thin-film transistors on transferrable silicon nanomembranes for high-performance flexible electronics.,” Small (Weinheim an der Bergstrasse, Germany), vol. 6, no. 22, pp. 2553-7, Nov. 2010.

Carbon nanotubes (CNTs) have been widely used in composites to improve the mechanical and electrical properties of a polymer matrix. Recently, single wall carbon nanotubes (SWNTs) have emerged as candidates for high performance carbon based electronic devices. In order to form a conducting path inside a polymer matrix, carbon nanotubes must form a network of interconnected, or percolated, tubes. Below a minimum concentration (percolation threshold), the nanotubes do not form a percolated path and the composite is non-conductive. The percolation threshold in a polystyrene matrix with random SWNT network was previously reported be as low as 0.17 wt.%^1,2.

Composites with different SWNT concentrations were produced and characterized by atomic force microscopy, UV-vis spectroscopy and electrical conductivity measurements. We report a reduction in percolation threshold by 3 orders of magnitude in nano-engineered SWNT networks³. The extremely low concentration necessary to form conduction provides an economical solution to make SWNT composites, and opens new routes for functional conductive nanotube composites which are also highly transparent. We present results showing conductive composites with a transmittance close to 100% in the whole visible range.
(1) Shrivastava, N. K.; Khatua, B. B. Carbon 2011, 49, 4571-4579.
(2) Tchoul, M. N.; Ford, W. T.; Ha, M. L. P.; Chavez-Sumarriva, I.; Grady, B. P.; Lolli, G.; Resasco, D. E.; Arepalli, S. Chem. Mater. 2008, 20, 3120-3126.
(3) Boulanger N. and Barbero D. R., in preparation (2013).

We recently developed stretchable electronic devices using several types of one-dimensional (1D) nanostructures such as silicon nanowires (SiNWs), Ag NWs and carbon nanotubes (CNTs) for stretchable/flexible devices. Several advantages of 1D nanostructures for such applications include: 1) the 1D nanostructures possess excellent electric and mechanical properties, such as high mobility and large fracture strength; 2) they can be tailored into different buckling shapes, either individually or collectively. For example, individual SiNW were found to buckle into coiled shape, which exhibited superior stretchability (e.g., over 100% strain); CNTs and AgNWs buckled collectively either out-of-plane or in-plane. In this talk, we will discuss several device applications based on the 1D nanostructures, including strain gages, pressure sensors, tactile sensors and wearable electrodes for bioelectric measurements.

Some of the most successful approaches in stretchable electronics rely on hard/soft composite materials, in a generalized sense of the term. The hard component provides semiconductor device functionality, while the soft supporting matrix enables an overall elastic response to large strain deformation. This talk describes concepts in fractal mechanics and heterogeneous integration that provide utility in this area. Device examples include classes of electronic systems that can establish non-invasive, high quality active interfaces to tissues of the human body.

Scientists dream to minic nature by exploring elastic and soft forms of robots, electronic skin and energy harvesters. Such research potentially enables novel applications in diverse fields, sports and healthcare, biomedical systems to consumer and mobile appliances. All conceivable classes of materials are employed, with an extremely wide range in mechanical, physical and chemical properties. Liquids and gels, organic and inorganic solids are combined to achieve.functionalities never seen before. In the presentation soft robots which allow actuation with several degrees of freedom are discussed to emphasize that different actuation mechanisms lead to similar actuators, capable of truly complex and smooth movements in 3d space. Latest research examples in sensor skin development are introduced and ultra-flexible electronic circuits are discussed, as well as light emitting diodes and solar cells. Briefly reviewed are additional functionalities of sensor skin, such as visual sensors inspired by animal eyes, camouflage, self-cleaning and healing and on-skin energy storage and generation. Finally, it is shown how to change energy generators from hard ones to soft ones based on dielectric elastomers, leading to a paradigm change in energy harvesting. Soft energy generators are shown to work with high energy of conversion, making them potentially interesting for harvesting mechanical energy from human gait, winds and ocean waves. Currently we are at the verge of witnessing the demonstration of truly complex bionic systems, eventually similar to the machine human in "Metropolis" and the android “Data”, the visionary character from Star Trek. Without much doubt, the future of soft materials research is bright, and this century may later be termed “the soft matter age”.

Recent advances in graphene research, particularly the colloidal chemistry of chemically reduced graphene using low-cost solution processing techniques and the self-assembly of graphene sheets using vacuum filtration of chemically reduced graphene colloids, open up new ways to utilize large scale graphene in significant quantities. At the same time, the emerging application of flexible/stretchable devices, ranging from electronics, composites, biomedicine, to energy storage, brings up new challenges in engineering large-scale nanomaterials to generate some extraordinary properties and multifunctionalities. Here, we present a soft approach that addresses the challenges, to control reversible crumpling and unfolding of large-area graphene papers by harnessing its mechanical instabilities using soft materials. We transfer large-area graphene paper on an elastomer substrate that is either uniaxially or biaxially stretched to 3~5 times of its original dimension. Graphene paper develops wrinkles and delaminated buckles when the substrate is relaxed uniaxially, and become crumpled when the substrate is relaxed biaxially. The crumpled graphene paper can be unfolded by stretching the substrate back. The contact angle (CA) of crumpled graphene paper is 162 degree with a hysteresis CA of 157 degree, showing an interesting “rose petal effect”. The CA of crumpled Au/graphene paper is 168 degree with a hysteresis CA of 3 degree, showing an interesting “lotus leaf effect” with self-cleaning capability. The crumpled Au/graphene paper remains superhydrophobicity with extremely low hysteresis CA (below 10 degree) even when graphene paper stretches to two times of its original size. Unfolding crumpled graphene paper with nano-scale pores is used for extremely stretchable supercapacitor with a stable capacitance of ~150 F/g over 400% uniaxially tensile strain or 350% × 350% biaxially tensile strain. The research on reversible crumpling and unfolding of graphene papers offers multifunctionalities, from on-demand super-hydrophobicity to stretchable supercapacitors, enabling us to advancing graphene-base technologies for many practical applications.

Our recent work [1] has shown that coiled carbon nanotube (CNT) composite yarns have great potential as highly reversible, fast, strong and with large-stroke tensile and torsional types of actuators (Fig. 1). This new class of artificial muscles has several potential applications such as lighter and faster actuators for robotics, nano-medicine, MEMS, energy harvesting, smart materials and textiles. The two main mechanisms for actuation in coiled artificial muscles are the expansion of the active material driven by either thermal expansion or absorption of molecules or ions. Thermal actuation can be achieved electrically, photonically, by convection (absorbing heat from the environment) or by exothermal chemical reactions. The large changes in temperatures makes this type of actuation energetically inefficient and not compatible with many types of applications. Absorption driven actuation shows great promise for development of more energetically efficient and biocompatible actuators since it can operate isothermally. We have recently advanced our artificial muscles by using absorption driven actuation in polymer loaded CNT yarns which are capable to delivers up to 50% tensile contraction. Actuation under loads up to 50 MPa and with contraction times less than 0.2 sec were demonstrated and the same yarns can also operate thermally using electricity or light.
[1] M. D. Lima et al., Electrically, Chemically, and Photonically Powered Torsional and Tensile Actuation of Hybrid Carbon Nanotube Yarn Muscles. Science 338 (2012) 928.

In recent years, the development of soft and stretchable electronics and sensors has seen the wide use of Polydimethylsiloxane (PDMS) as a convenient soft substrate on which such circuits are fabricated. When coupled with compliant electrodes, silicone membranes can be used however not simply as a passive elastic substrate, but also as an active material, for sensing, actuation, and for optics, allowing for completely flexible objects with a complex and intelligent behaviour. We illustrate this potential for integration in this papers with two devices: a) a bio-inspired Dielectric Elastomer Actuator (DEA) -based electrically tuneable lens capable of changing its focal length by up to 28% in less than 500 mu;s, and b) a compliant DEA energy harvesting system with 128 active silicone layers.
Our tunable lens consists of two circular PDMS membranes bonded together by oxygen plasma. At the centre, a small amount of liquid (un-crosslinked PDMS) is encapsulated between the two membranes to form a Oslash;5 mm bi-convex lens with an initial curvature radius between 8 and 16mm. Annulus-shaped compliant electrodes are patterned on both sides of the device around the lens. When a voltage is applied between the electrodes, the charges squeeze the membrane in the electroded zone, which expands in plane. The lens is therefore compressed, and its diameter decreases, causing an increase of the lens curvature and decrease of the focal lens, similar to what happens in the crystalline lens of our eyes. Here, PDMS plays the multifaceted task of constitutive material for the whole device, active material providing actuation, stretchable optical material defining the lens, and high refractive index liquid inside the lens.
Unlike traditional optical systems, which achieve tuning by moving rigid fixed-focal lenses relative to each other, our bio-inspired lens minimizes the displaced mass allowing very fast tuning. It also minimizes the number of parts needed to build a lens, leading to a fast and cheap fabrication process. The amount of liquid displaced upon activation is minimized, and thanks to the low viscoelasticity of PDMS, the lens presents sub ms response time, and no long-term viscoelastic drift, as often observed with DEAs based on acrylic elastomer membranes
We also show how PDMS in a dielectric elastomer structure can be used as a soft and deformable capacitor for energy harvesting. We present a 1cm3 generator formed by a stack of 128 active layers connected in parallel for an initial capacitance of 2.2nF. The cylindrical structure is compressed until its capacitance doubles, and then relaxed to the initial position. We demonstrate an energy generation of 4mJ/cycle when activated at 1Hz (ie. 4 mW power output)
Combining such actuators or generators with soft electronics allows using PDMS for new smart and soft machines integrating intelligence and actuation and capable of harvesting the energy they need from their environment.

In recent years, supramolecular chemistry has been utilized to tune the intermolecular interactions of soft polymers. These supramolecular interactions exhibit reversibility in response to a number of environmental triggers or stimuli including temperature, pH, light, chemical, magnetic and electric field activation. Of dramatic interest, is the coupling of the aforementioned physical fields with a mechanical response particularly large deformations and conformational changes in response to an external trigger. Materials of this type are generally referred to as active or smart materials. Biological systems have highly vascularized networks that deliver internal triggers to activate a variety of processes. This observation has been leveraged to date to investigate synthetic interpenetrating vascular channels for self-healing and self-cooling via sacrificial fibers. We introduce a class of novel active materials that use vascular networks containing physically or chemically functionalized fluids to enable polymer activation i.e. shape change and that are also capable of large strain mechanical sensing. We have previously demonstrated internal activation of shape memory polymers by means of an interpenetrating thermal network. Here, we utilize stereolithography (SLA) type 3D printing to directly fabricate microchannel arrays in a soft dielectric elastomer. The channel network is filled with a eutectic alloy of gallium and indium (EGaIn) liquid metal. We demonstrate that applying an electric field induces localized channel deformation enabling surface patterning and large-scale area change. As a sensor, the network changes its electrical properties (resistance/capacitance) when the polymer is stretched up to 100%. This combined concept of sensing and actuating microstructures provides new opportunities for stretchable active materials in applications such as skin-like distributed transducers and stretchable displays.

Materials that adapt dynamically to environmental changes are currently limited to two-state switching of single properties, and only a small number of strategies that may lead to materials with continuously adjustable characteristics have been reported. I will discuss adaptive surfaces made of a liquid film supported by a nanoporous elastic substrate. As the substrate deforms, the liquid flows within the pores, causing the smooth and defect-free surface to roughen through a continuous range of topographies. In this novel material, a graded mechanical stimulus can be directly translated into finely tuned, dynamic adjustments of optical transparency and wettability. In particular, I will demonstrate simultaneous control of the film&’s transparency and its ability to continuously manipulate various low-surface-tension droplets from free-sliding to pinned. This strategy should make possible the rational design of tunable, multifunctional adaptive materials for a broad range of applications.

In this work, we investigate the processes leading to the room-temperature growth of carbon based nano-crystals, notably silicon carbide (SiC) and graphene, by supersonic molecular beam epitaxy technique. In particular, we present both experimental data and computational modeling of the collision of fullerene on silicon and copper surfaces. This intermediate energy impact induces strong chemical-physical perturbations in the system and, for sufficient translational energy, disruption of molecular bonds and C60 cage breaking, leading to the formation of nanostructures with different stoichiometric character.
Careful and extensive characterization of the material by a variety of experimental techniques (XPS, UPS, Auger, LEED, TEM, Raman) after the collision demonstrates the
potentiality of our approach to grow nanostructured materials at room temperature.
On the theoretical side, we show that in these out-of-equilibrium conditions, it is necessary to go beyond the standard implementations of density functional theory, as ab-initio methods based on the Born-Oppenheimer approximation fail to capture the excited-state dynamics. In
particular, we analyse the Si- and Cu-C60 collision within the non-adiabatic nuclear dynamics framework, where stochastic hops occur between adiabatic surfaces calculated with time-dependent density functional theory. This theoretical description of the C60 impact on metallic and semiconductive substrates is in good agreement with our experimental findings.

Purpose. Photoacoustic (PA) imaging holds great promise for the visualization of physiology and pathology at the molecular level with deep tissue penetration and fine spatial resolution. However, the full utilization of this potential is greatly constrained by the lack of PA molecular imaging probes, particularly activatable PA probes. Herein we introduce near infrared (NIR) absorbing semiconducting polymer nanoparticles (SPNs) as a new class of PA contrast agents that outperform many existing materials for PA molecular imaging.
Results. Semiconducting polymers (SPs) originally used to convert sunlight into electricity have been made into nanoparticles that produce ultrasound signals upon pulsed NIR laser irradiation. These nanoparticles have a unique set of advantages that derive from their precursor SPs, including a large mass extinction coefficient and high photostability. These advantages make SPN a superior PA imaging agent with stronger and more photostable PA signals in the NIR region when compared with single-wall carbon nantubes (SWNTs) and golden nanorod (GNRs). At the same mass concentration, the intrinsic PA amplitude of the SPN at 700 nm can be more than 5-times higher than SWNTs and GNRs. Such a high PA brightness in conjunction with its favorable size (sim;40 nm) enables the efficient PA imaging of major lymph nodes in living mice with a high signal-to-noise ratio of 13.3 after a single intravenous administration of a small amount of SPN. With the characteristics such as a narrow PA spectral profile, good photostability and reactive oxygen species (ROS) inert PA signal, we have developed the first NIR ratiometric PA probe for in vivo real-time imaging of reactive oxygen species that are vital chemical mediators of diseases, such as cancer, cardiomyopathy, stroke and bacterial infections.
Conclusion. We have introduced SPNs as a new class of NIR PA contrast agents for in vivo PA molecular imaging. They can serve not only as simple accumulation-based PA probes (as demonstrated for lymph node mapping) but also as a platform to develop activatable probes (as shown by ratiometric PA imaging of inflammatory ROS in living mice). Given many key merits of SPNs, we believe that SPNs can provide opportunities for advanced PA molecular imaging, from facilitating the preclinical investigation of physiological and pathological processes in living subjects to enhancing the PA imaging modality now in the process of clinical translation.

This presentation highlights the preparation of poly(sodium acrylate) (PSA) cryogels incorporated with silver nanoparticles (AgNPs) for rapid disinfection of drinking water. Robust PSA cryogels with a superfast swelling rate and a high degree of swelling were synthesized by cryo-copolymerizing N,N&’-methylenebis(acrylamide) and sodium acrylate. Several synthesis methods were used to prepare cryogel/AgNPs hybrids. The as-synthesized cryogels were comprehensively characterized using FESEM, CLSM, TEM, XRD, XPS, and X-ray micro-CT. The excellent swelling and mechanical properties of the cryogels inspired us to proposed a novel strategy for emergency water disinfection. The approach involves using the cryogels as a sponge to absorb contaminated water during which the bacterial cells are inactivated after getting into close contact with the bioactive Ag species on the cryogel pore surfaces, and squeezing the water out of the swollen cryogel to recover the disinfected water. Hybrids of cryogel/AgNPs prepared via the intermatrix synthesis (IMS) method could inactivate more than 5-logs of viable bacteria after a brief 15-s swelling time. These cryogels are also effective in disinfecting natural water samples and showed stable performance over ten repetitions. In addition, the total dissolved Ag concentration in the treated (or squeezed) water was below the WHO&’s recommended limit for Ag in drinking water (100 µg/L). Other synthesis methods such as cryogelation of the PSA cryogel in the presence of nanosilver and an ice-mediated coating will also be discussed in the presentation. These methods are anticipated to result in a different nanosilver distribution in the cryogel (on the pore surface, within cryogel matrix, or both), and hence different antibacterial properties as compared to the PSA/Ag cryogels synthesized using the IMS method. This will presentation will also highlight our recent investigations on the biocidal mechanisms of the cryogel/AgNPs hybrids and the effect solution chemistry on their bactericidal and Ag release behavior. The results obtained thus far indicate that the cryogels offer excellent potential for applications requiring potable water production in response to emergencies or disasters. Furthermore, the cryogels permit simple operation and can be easily deployed for emergency response due to its lightweight.

Broad-spectrum antibacterial agents, such as fluoroquinolones (i.e. levofloxacin, ciprofloxacin, etc.) are highly effective agents in the treatment and prophylactic prevention for a variety of bacterial infections. However, a major problem with fluoroquinolones, in addition to many other antibacterial agents, is their quick excretion that ultimately requires frequent dosing schedules. Nanoparticle formulations have the potential to overcome this problem due to their high cargo capacities and sustained release capabilities. The nanoporous silica particle-supported lipid bilayer (or ‘protocell&’) is a novel cargo delivery platform that synergistically combines the advantages of both mesoporous nanoparticles and liposomes while simultaneously overcoming the downfalls of either nanoparticle alone. Protocells are formed via electrostatic fusion of liposomes to mesoporous silica nanoparticle cores. The mesoporous core has a high surface area, tunable porosity, controllable diameter, and tailorable surface chemistry, making it amenable to being loaded with various types of cargo. The release rates of small molecule drugs are inversely proportional to the degree of silica condensation in conjunction with the physicochemical properties of the drug, and can therefore be modulated by controlling the degree of silica condensation either during synthesis or through post-synthesis processing. The supported lipid bilayer (SLB) provides a fluid surface, to which peptides, polymers and other molecules can be conjugated to promote specificity, enhanced circulation times, and serves as a barrier to cap cargo within the silica particle core. Here we describe how the physicochemical properties of the SLB can be further engineered to confer protocell stability in extreme conditions that simulate the characteristic environment of the gastrointestinal tract. Enhanced stability is accomplished via covalent attachment of the SLB to the silica particle surface in conjunction with the controlled deposition of polymer-cushioned bilayers. Covalent SLB attachment to the nanoparticle surface is accomplished via the reaction of heterobifunctional crosslinkers towards functionalized silanes on the silica surface followed by reaction with either functionalized phospholipid or cholesterol molecules and electrostatic SLB fusion. Subsequent fusion of additional bilayers is electrostatically induced through the use of cationic polymers and mixtures of anionic and zwitterionic lipids and is controlled by the stoichiometric ratios of lipid to polymer. This layer-by-layer deposition allows for sacrificial bilayers to be degraded in the lower pH of the GI while protecting the covalently attached bilayer and protects the protocell against the lipolytic and proteolytic action of digestive enzymes, which make it possible for the protocell to engineered for oral delivery of a variety of therapeutic compounds.

Proteases are involved in several diseases including cancer and pathogen infection¹. In HIV infection, the viral protease plays a central role in the virus lifecycle, which has made it a clear therapeutic target. In this work we propose new peptide nanosensors for the one-step detection of proteases that could be used for the one-step detection of proteases based on two biorecognition events, increasing the selectivity and specificity of the assay with respect to previously proposed methods.
The first step in the design of the peptide nanosensors involves finding sequences that can recognize the target protease with high affinity. This is achieved through phage display - an in-vitro screening method which allows for the isolation of peptide sequences which show an affinity to a target protein of choice. Five heptameric peptide sequences were found. These bind to different regions of the HIV-1 protease. These sequences have been characterised for their inhibitory effects and binding affinities through biochemical (ELISA) and biophysical (SPR) assays. Two sequences showed mild inhibitory effects (above concentrations of 10mu;M) while all show strong affinities to the protease of at least an order of magnitude greater than controls.
These sequences were then bound to fluorescent tags to obtain peptide nanosensors. The binding of the peptides to different sites of the protease results in a FRET signal that can be used to detect the protease in one step without the utilization of tedious incubation and washing steps typical of laboratory-based techniques such as ELISA^2-3. The results of these experiments show promising behaviour towards future detection strategies for the point-of-care detection of disease biomarkers.
1. Aili, D.; Stevens, MM., Bioresponsive peptide -inorganic hybrid nanomaterials. Chem. Soc. Rev, 2010, 39, 3358-3370
2. De la Rica, R.; Stevens, MM., Plasmonic ELISA for the ultrasensitive detection of disease biomarkers with the naked eye. Nature Nanotechnology, 2012, 7, 821-824
3. Rodríguez-Lorenzo, L.; de la Rica, R.; Álvarez-Puebla, RA.; Liz-Marzán, LM.; Stevens, MM., Plasmonic nanosensors with inverse sensitivity by means of enzyme-guided crystal growth. Nature Materials, 2012, 11, 604-60

In the last two decades the understanding of fundamental aspects in cell biology has rapidly increased due to investigation of cellular response primarily in 2-D environments, showing that cells are influenced by topographic patterns, (1) biochemical cues (2) and substrate mechanical properties. (3) These determinants play a central role in many cellular functions, such as proliferation, migration, differentiation and apoptosis. Ongoing studies that target the investigation of cellular behavior in designed microenvironments further revealed that the 3-D geometry of the matrix, mimicking the extracellular matrix (ECM), plays a central role. (4) 3-D matrices with well-defined microenvironments, which are asymmetric or in which the key determinants geometry, topography, biochemical functionality and mechanical properties can be varied independently, are currently addressed to enable unprecedented insight into cellular behavior.
We report here on our efforts in creating 3-D cellular microenvironments by patterning of biocompatible polymers via nanoimprint lithography, analyzing the resulting topographic structures via atomic force microscopy (AFM) and scanning electron microscopy (SEM) and finally investigating the behavior of pancreatic tumor cells (Patu T 8988) in these microenvironments. We further report on novel approaches based on directed assembly of polymeric building blocks with different shapes that are used to design asymmetric cellular environments. The controlled surface modification of these building blocks with various monomers via the grafting from and grafting to techniques is discussed. Subsequent to surface functionalization with an initiator, both free radical and atom transfer radical polymerization (ATRP), respectively, (5) were exploited to grow brush-like polymer layers. The modified surfaces were further investigated with ellipsometry, AFM, reflection Fourier-transformed infrared spectroscopy (FT-IR) and contact angle measurements. Finally the behavior of Patu T 8988 cells was investigated on these tailored microenvironments that contained various structures.
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(2) Connelly J.T., Gautrot J.E., Trappmann B., Tan D.W.M., Donati G.,
Huck W.T.S, Watt F.M. Nature Cell. Biol. 2010, 12, 711
(3) Discher D.E., Janmey P., Wang Y.-L., Science 2005, 310, 1139
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J.R.Soc.Interface 2008, 5, 1173
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Macromol. Symposia 2013, 328, 64-72

Structural DNA is an emerging templating technology for energy, sensing and other applications due to its ability to repeatably self-assemble complex architectures with nanoscale precision. These architectures can vary in form from linear DNA to custom 2-D and 3-D shapes designed using DNA origami, and can have site-specific fluorescent tags or nanoparticles to enable optical, mechanical or eletrical effects. In order to ensure complete self-assembly and to examine stuctural characteristics, high-resolution physical characterization is necessary. Imaging has been heretofore limited to atomic-force microscopy or required negative staining procedures relevant for TEM of biological applications to be observed. For structures under 50 nm, settling times limit AFM and staining limits the resolution required for robust characterization. To increase the resolution for TEM and STEM, sample preparation is critical for preparing such structures and ultrathin substrates (such as graphene) are neccesary for direct imaging to occur.
In a previous study, we demonstrated a method for transmission electron microscopy imaging of low contrast biomolecules using suspended graphene supports. However, certain limitations remain. Graphene grown by CVD on Cu foils and subsequently transfered using a resist-based liftout often leaves residues on the graphene support film, which are visible at high resolution and makes determining DNA structures ambiguous. Adventitious carbon deposited during sample handling is another source of contamination. Additionally, as-produced graphene is hydrophobic, and thus not well-suited for uniform dispersal of DNA structures. Attempts to clean and oxidize the graphene using an oxygen plasma can reduce the hydrophobicity of the surface. These treatments, however, can oxidize the graphene leading to charging artifacts, damage to the graphene structural backbone, and render it less useful for imaging. In this study, we chronicle the effects of various cleaning and subtle oxidation treatments on the preparation of graphene surface supports for imaging. These include high-temperature H2 and/or CO2 annealing, or annealing in Ar/O2 mixture ambients. Using these supports, we highight direct imaging of unstained, DNA Origami nanostructures both in TEM (JEOL 2200 FS, 200 kV) and low-voltage STEM mode (aberration-corrected Nion UltraSTEM, 60keV). We found that the use of H2 significantly lowered the amount adventitious carbon and photoresist while leaving the surface hydrophobic. Other oxidation techniques improved the hydrophobic nature of the surface and lowered the contact angle, and thus decreased the concentration of DNA required for direct imaging. AFM and XPS measurments were performed for macroscale characterization of the effects of our heat treatments. We were able to directly characterize DNA structures and found that certain ambiguities about origami shape and size could be clarified.

Nature surprises and inspires people by producing nanomaterials with superior mechanical behavior. It is of great importance to learn from nature and therefore, develop biomimetic materials accordingly. In the recent decade, countless efforts were carried out by researchers around the world for this goal. However, the long standing difficulty persists in determining and characterizing the properties of soft biomaterials, especially tissues, as while as developing synthetic nano materials which duplicate not only the structure but also the behavior of the nature ones.
This presentation is targeted to report our efforts in light of paving above difficulties. First, natural tissue was investigated as a “role model” of the biomimetic materials. Mechanical properties of rat liver were obtained under micro and nano scales. The measured properties exhibit strong correlation with and high sensitivity to the tissue&’s surrounding temperature. Then, Polydimethylsiloxane (PDMS) were modified with nano ceramic particles in hope to resemble the hierarchical structure of nature tissue. As the first step of this effort, single layer PDMS/nano-ceramic composites were fabricated into sub-micron thick films, and then characterized and examined with micro/nano indentation experiments. Constitutive behavior was extracted from the experimental data with the help of theoretical modeling. Temperature effects were once again observed and compared with those obtained from rat liver. Furthermore, structural and mechanical behavior of bulk PDMS/nano-ceramics composites were observed and characterized by confocal microscopy and macro/micro mechanical experiments, respectively. It&’s always meaningful to resemble nano structures into macro ones which in the similar scale of tissue/organ. Only when the synthetic tissue/organ exhibits viability and improved mechanical behavior, we can conclude that the success is achieved.

The reported work is meaningful in following aspects. First, temperature effects on mechanical property of rat liver could provide optimization plan for the radiation therapy for cancer. Second, a widely-adopted biomedical material PDMS was modified with nano ceramic particles and the mechanical response of the resulting composite was compared with natural liver as a biomimetic effort of replicating superior hierarchy structure of natural tissue. Third, contact behavior between rigid indenter and tissue/composite mimics that between the man-made implant and surrounding tissues. Hence, the investigation on the contact between indenter and tissue/composite could provide hints to the in-depth understanding upon the interaction between implant and tissue.

Increasingly, nanoparticle formulations incorporate multiple components, including both diagnostic and therapeutic functionalities, within a single construct. Direct encapsulation of such units, however, can lead to unfavorable interactions between encapsulated materials, as well as reduced performance of the nanoparticle. While surface functionalization serves as a method of spatial organization, subsequent reaction and purification steps can be detrimental to the formulation. To this end, we synthesized a chitosan modified with hydrophobic, octadecyl chains and gadolinium-chelating diethylenetriaminepentaacetic acid, named as a polymeric fastener. In this way, the chitosan fastener was able to link gadolinium, an MRI contrast agent, to the surface of liposomes by self-assembly. Due to the localization of gadolinium on the liposome surface, we were able to achieve enhanced relaxivity compared to gadolinium loaded within the liposome. The resulting gadolinium-coated liposome enabled us to successfully detect and image defective vasculature in an ischemic hindlimb and kidney using MRI.
In addition, we improved the stability of the liposome-fastener complex in physiological fluid by cross-linking lipids of the liposome using DC8,9PC lipids, which contained the photo cross-linkable diyne moiety. This approach not only stabilized the liposome, but also enhanced its association with the functional fastener. Interestingly, cross-linking the lipids after attachment of the fastener, rather than prior, was critical in enhancing the initial association with the fastener, as well as stabilizing it in serum. Ultimately, the strategy proved effective in enhancing MRI contrast nearly two-fold per liposome dose after one hour of serum exposure. Taken together, we believe that both polymeric fastener and lipid cross-linking will be broadly useful in spatially organizing functional cues in nanoparticles and further extending their lifetimes.

Understanding cell adhesion to material surfaces is critical to the performance of implantable medical devices. Bacteria are becoming increasingly resistant to the effects of antibiotics. Furthermore, proteins which adsorb to the material surface will eventually mask the effects of chemical surface modifications. There is increasing interest in designing antimicrobial surfaces inspired by nature. Researchers found that nanostructures on the surface of cicada wings can kill bacterial cells, apparently through physical surface topography (Ivanova et al. 2012, Pogodin et al. 2013). In previous studies we found that nanopatterns can also control the adhesion of mammalian cells (Yim et al. 2005, Kong et al. 2013). Our objectives are to develop polymer surfaces that could control cell adhesion solely by altering physical surface topography and to study the role of geometric parameters on adhesion.
We created nanostructures on polymethylmethacrylate (PMMA) films using nanoimprint lithography (Guo 2004), and plated E. coli on flat film, line gratings (width = 134 ± 9 nm), and pillared surfaces (diameter = 215 ± 9 nm, spacing = 342 ± 22 nm). After 20 hours, bacteria on the flat film and line gratings are fully rod-shaped, the normal E. coli cell morphology. On round pillared surfaces, bacteria appear more deflated on pillars, stretching over the spaces between the pillars. In live dead assays, we observed that the total number of cells on pillared surfaces decreased compared to the total number on the flat film, and the percentage of dead cells found on the pillared surface is twice the percentages found on the flat film and line gratings (p<0.05). We also observed that the average length of dead cells on all three surface patterns is twice the average length of live cells.
In preliminary studies using mammalian cells, we seeded primary murine macrophages onto PMMA films. Previous work showed a correlation of cell shape and macrophage phenotype in that elongated macrophages adopted the pro-healing phenotype (McWhorter et al. 2013). After 24 hours, we observed that the macrophages adopted different cell morphologies, possibly indicating changes in their phenotype. Macrophages showed a spread-like morphology on the flat film. On line gratings, macrophages elongated and aligned in the direction of the lines. While the average elongation factor of cells observed on microscale lines was 10 (McWhorter et al. 2013), the average elongation factor of cells on the nanolines was 13. Macrophages on round pillars were more equiaxed.
Our study has shown that imprinted nanostructures in the 100-500 nm-size range could prevent bacterial adhesion to a polymer surface, and pillar structures resulted in increased bacterial cell mortality on the PMMA surface. We found that structure dimensions could induce various mechanisms that led to the materials&’ antibacterial properties as well as the modulation of macrophage response toward pro-healing versus pro-inflammatory.

Biosensing utilizing Localized Surface Plasmon Resonance (LSPR) offers label-free, sensitive, and facile detection.1 However, the measurement of specific analytes of interest through plasmonic devices in complex biological media has been limited due to lack of specificity and biofouling. This presentation will highlight recent advances in LSPR-based biosensing devices in the Sagle group to overcome these limitations. Protein-nanoparticle devices which monitor changes in solution pH and glucose concentration are presented. These devices make use of protein conformational changes which mediate the plasmonic coupling between nanoparticles. The resulting changes in the LSPR frequency are significantly less susceptible to biofouling. Moreover, the specificity stems from the protein itself, and is not limited by surface chemistry. Ultimately, our goal is to put such plasmonic devices on a surface to allow for microfluidic, on-chip fabrication. In order to improve protein-surface compatibility, nanofabrication techniques designed to optimize biomolecular orientation and binding capabilities on a surface are also presented.
1. a) K. A. Willets and R. P. Van Duyne, Ann. Rev. Phys. Chem., 2007, 58, 267-297, b) L. B. Sagle, L. K. Ruvuna, J. A. Ruemmele and R. P. Van Duyne, Nanomedicine, 2011, 6, 1447-1462.

Locomotion of synthetic nano-/microscale objects through fluid environments is one of the most exciting and challenging areas of nanotechnology. Inspired by animal interactions, the ability of synthetic nanoscale motors to produce self-organized structures is of considerable interest, owing to their future implications in nanomedicine, nanomachinery, transport systems, and chemical sensing. Organized self-assemblies of Janus catalytic motors, induced by hydrophobic surface interactions involving multiple motor/motor and motor/nonmotor particles, display controlled coordinated self-propulsion. These assemblies were prepared by octadecyltrichlorosilane (OTS) modification of the surface of a silica microparticle and addition of a catalytic Pt hemispheric coating. The influence of the self-assembled structures upon the motion behavior is investigated. Different bonding orientations between these hydrophobic Janus motors induce different forms of motion. The relative orientation of each motor in the assembly changes its contribution to the net propulsion force and rotational moment. The hydrophobic interactions between individual micromotors and micromotor assemblies can promote a continuous growth of the assembly during its movement and lead to dynamic changes in the motion behavior. Organized assemblies of multiple motor/nonmotor particles are also illustrated toward optimal cargo transport and delivery. Such controlled structures and motion of chemically powered Janus nanomotor assemblies hold considerable promise for the creation of intelligent nanomachines that perform collective tasks.

Gold nanocages (AuNCs), a novel class of hollow plasmonic nanostructures, have been extensively investigated for bioimaging and therapeutic applications. AuNCs have also been employed as contrast agents in optical coherence tomography, photoacoustic imaging and photothermal therapy. It has been predicted that hollow nanostructures exhibit significantly higher refractive index sensitivity compared to solid nanoparticles like nanospheres, nanocubes, and nanorods. However, the use of gold nanocages as plasmonic nanotransducers for biosensing is still rare. For the first time, here we demonstrate that the large refractive index sensitivity and small electromagnetic decay length of AuNCs make them excellent candidates for label-free plasmonic biosensing. AuNCs with built in artificial antibodies by molecularly imprinting enables the detection of kidney injury biomarker (neutrophil gelatinase-associated lipocalin, NGAL) from synthetic urine down to the concentration of 25 ng/ml; which is more than an order of magnitude lower compared to gold nanorods. The limit of detection of the target biomarker is significantly improved. In addition to the excellent sensitivity, AuNCs with built-in artificial antibodies for NGAL exhibit excellent selectivity against numerous interfering urinary proteins and remarkable stability across pH ranging from 4.5 to 8.5 and specific gravities from 1.005 to 1.030. The AuNCs-based biosensor can be employed in point-of-care setting to rapidly urinalysis for patients that can progress to acute kidney injury, thus enabling early therapeutic intervention.

Ironically, sulfur is rather suffering from excessive surplus and its lowering price even though it is mainly produced from petroleum which is on the brink of depletion. People still have difficulty in figuring out what to do with the abundant and cheap sulfur except for limited utilization such as agriculture and a few chemical products including rubbers. Sulfur itself exhibits a number of useful properties relevant to advanced materials. However, due to its inherently poor solubility, brittle nature, and spontaneous sublimation, synthesis and processing methods with sulfur to prepare well-defined functional materials are currently limited. Recently, our group developed facile polymerization methods for processible polysulfide copolymers with high content of sulphur, namely, ‘inverse vulcanization&’. A number of polysulfide polymers were synthesized by the simple reaction of divinylic monomers within bulk liquid sulphur.
Meanwhile, the chemistry of amine and sulfur has previously been explored in the context of preparing chalcogenide based semiconductor nanocrystals. In these nanocrystal syntheses, the reaction of oleylamine and sulfur served to generate H2S as the sulfur source to promote metal chalcogenide formation. Herein, we report on the copolymerization of sulfur with oleylamine to prepare high content sulfur copolymers and PbS nanoparticle composite materials. In the current study, we report on the dual reactivity of oleylamine to form chemical stable copolymers via copolymerization with elemental sulfur, along with in situ formation of PbS nanoparticles (NPs) to prepare PbS-sulfur copolymer nanocomposites. In this system, a one pot, tandem reaction of oleylamine and sulfur in the presence of PbS NP precursors enabled in situ formation of chalcogenide NPs, which enabled efficient dispersion of colloidal inclusions throughout the sulfur copolymer matrix. The number density of NPs in the copolymer matrix was easily controlled by varying the concentration of Pb2+ ions added in the copolymer solutions. Furthermore, resulting nanocomposites were well dissolved in common organic solvents, enabling spin-casting to fabricate nanocomposite thin films. Other inorganic nanoparticles are also expected to form similar nanocomposites based on the currrent work as far as they can be synthesized using oleylamines as coordinating ligands. This general approach is a new synthetic advance in the emerging area of sulfur utilization by direct modification of elemental sulfur as a novel feedstock for material synthesis.

Materials with hierarchical or multimodal pores have attracted considerable attention due to their outstanding structural characteristics. In multimodally porous systems, larger pores provide the optimized transport through enhanced accessibility to internal sites. In parallel, smaller pores impart the characteristics of increased interfacial area as well as the specific size selectivity. To form such structures, dual templating, micelle-assisted methods and photolithography are mainly utilized, however, they have suffered from several limitations in obtaining greater flexibility and large-area scalability, along with an issue of non-economically viable process. Here, we demonstrate a novel means to fabricate the hierarchically porous membranes with well-ordered structures using a strategy of multiscale self-assembly. To fabricate the hierarchically porous structures, first, macroporous three dimensional-inverse opal (3D-IO) structures, primary pores, is prepared by fabricating the inverse opal structure (IO) by molding the interstitial gaps of the highly ordered colloidal opal structure with UV-curable polymeric resin as a constituent of the outer skeletal frame. The constructed 3D-IO structures offer several advantages of large-area fabrication capability as well as reinforced mechanical stability. The IO structured template was then dip-coated with a block copolymer (BCP) solution of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) to form cylindrically microphase-separated BCP films, preferentially at the internecking pores of 3D-IO structure. After selective removal of the minor PMMA phase, BCP nanocolander networks with uniform-sized mesopores can be created. Finally, hierarchically porous structures in a form of free-standing films have been readily adopted for potential application in ultrafiltration (UF) membranes. Notably, it is observed that enhanced membrane performances with high selectivity and high permeability are concurrently obtained. Therefore, we anticipate that this type of hierarchically porous membranes, consisting of macroporous 3D-IO and mesoporous phase-separated BCP, have a great promise for the next-generation porous framework such as, separation, energy storage, catalysis and chemical sensing due to their uniform pore size distribution, improved permeability, and highly mechanically strengthened properties.

We have developed that a new series of low-molecular-weight hydrogelators and provide intramolecular building block of phenyl-perfluorophenyl pair for the formation of supramolecular hydrogels. According to experimental and computational results, the formation of intramolecular phenyl-perfluorophenyl complex may be assisted by the sandwiching water between aromatic rings. It is notable that we synthesized an amino-acid based hydrogelator has the minimum number of atoms up to date and its scaffold can achieve all the hydrogel features associated with larger peptides. From the spectroscopic result, it indicates the aromatic-aromatic and hydrogen-bonding interactions may be the major driving force behind the self-assembly of the hydrogelators. We also found amino-acid sequence of the peptide building blocks could dominate the structural and physical properties of dipeptide hydrogels. The biocompatibility tests of the hydrogels show the newly discovered hydrogelators are potential biomaterials. This work illustrates the importance of structure-hydrogelation relationship and provides new concept for designing of self-assembly nanobiomaterials.
References
[1] Hsu, S.M.; Lin, Y.C.; Chang, J.W.; Liu, Y.H.; Lin, H.C., Angew. Chem. Int. Ed. under revision.
[2] Lin, H.C., Xu B., Applications of Supramolecular Chemistry (Eds.: H.-J. Schneider), CRC, Boca Raton, FL, 2012, Chap 13.
[3] Li, X., Kuang, Y., Shi J., Gao Y., Lin H.C., Xu B., J. Am. Chem. Soc. 2011, 133, 17513-17518
[4] Li, X., Kuang Y., Lin H.C., Gao Y., Shi J., Xu B., Angew. Chem. Int. Ed. 2011, 50, 9365-9369.

Because of the aesthetics, handy and low cost features, acrylic resin is the main material in denture fabrication last 40 years. The purpose of this study is to improve mechanical properties of acrylic based dental composites used in dentistry by applying nanofiber approaches. Polymethylmethacrylate (PMMA) is commonly used as a base acrylic denture material having the benefits of rapid and easy handling but sometime this material can be fractured or cracked in clinical use because of the strength issues that is frequently used in restorative dentistry in recent years. A wide variety of fillers that are used to produce PMMA composites draw the attention in literature. Using PMMA composite resins with electrospun polyvinylalcohol (PVA) nanofiber fillers is our first novelty. Also the producing and using aligned electrospun fibers as a filler is our second novelty of this practice. PVA was selected as composite filler because of biocompatibility and preparing easily also has non-toxic solvent. Electrospinning system is manufactured that allows manipulation of electric field used in the application of alignment in lab scale. Various auxillary electrode systems are used for different patterns of alignment with the manufactured device and electrode systems produce fibers in different range of diameter. Scanning electron microscopy (SEM) is used for physical characterization and determined the range of fiber diameters. After the optimization of concentration step, non-woven and aligned fibers are also analyzed. Non-woven fiber has no unique pattern because of the nature of electrospinning but aligned fibers has crossed lines. These produced fibers structured as layer-by-layer form with different features are used in producing PMMA dental composites with different volume ratios. The last part of the practice PMMA dental composites are produced with aligned and formless fibers that are characterized with three-point bending test. The maximum flexural strength figure shows that fiber load by weight %0.25 and above improves the maximum. The change of flexural strength, elastic modulus values and toughness are obtained and compared with formless and aligned PVA nanofiber included composite specimens. As a result, mechanical properties of PMMA dental composites are improved with using PVA nanofibers as a filler also with the usage of aligned fibers instead of the formless ones the effects of improvement gets better with maximum values as 5.21±0.8 MPa (flexural strength), 0.79±0.08 GPa (elastic modulus), 174±12 kJ/m3 (toughness).

Since silicon technology has shown limitations, soft lithography and flexible/ stretchable electronics have taken a great attention to overcome those limitations. Soft lithography is an alternative technology of conventional UV photolithography for ‘pattern transfering&’ and ‘microfabrication&’ tasks by making stamps, molding, and contact-printing processes at a low cost. Flexible/stretchable electronics employs a soft lithographic technique to transfer small patterns from the original masters to the substrates. The resolution of soft lithography relies on the elastomeric elements and also significantly affects to the electrical performance of flexible/stretchable devices. To enhance the electrical currency, scientists try to achieve nano-resolutions in soft lithography. However, commercially available silicon elastomers often results in collapse and mergence due to a low mechanical strength, especially in the nano-scale regime (<100 nm). The limitation has motivated us to bring a new version of silicon elastomer with a photocurable self-assembly. The new PDMS prepolymers are specifically designed to satisfy a set of requirements in soft lithography, such as a high physical toughness, low linear polymerization shrinkage, photocurability, and freedom from stress; we then inserted photocurable functionalities to reduce the thermal shrinkages. We demonstrated a soft lithographic performance using an a master with features of 300 nm width and 600 nm height, which is one of the most challenging ‘nano-patterning tasks&’ in this area. The result showed an improved pattern transfer performance. Furthermore, we also demonstrated ‘an elastomeric photo-pattern task.&’ The result showed a 5 micrometer resolution. As we demonstrated here, the photopatternability is crucial to advance stretchable electronics; functional patterns can be fabricated on the substrates using the photofunctional silicon elastomers.

Conducting polymers have been an intensely studied subject since the late 1970's. While these materials have found limited use in modern technological devices, primarily as anti-static coatings, they hold the potential to be used in a wide variety of devices, ranging from low-cost, light-weight solar cells to advanced biosensors. Unfortunately, despite the intense research efforts, the relationship between synthesis, morphology, doping, and material properties is still poorly understood for conducting polymers.
In this presentation I will discuss our efforts to address these issues by presenting our recent work on poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires. Specifically, I will discuss how we use the lithographically patterned nanowire electrodeposition method (LPNE) to prepare PEDOT nanowires from aqueous and non-aqueous solutions, how we have characterized the resulting nanowires (SEM, AFM, Raman, etc.), and how the various electrodeposition parameters (solvent, deposition voltage, template size, etc.) affect the materials properties (conductivity, crystallinity, average chain length) of the prepared nanowires.

Magnetic field responsive hydrogels have been intensively studied as smart materials. Applications of these hydrogels have been attempted in many fields including biomedicine engineering, non-degradable drug carrier, and tissue engineering. In this study, we demonstrated the feasibility of using tunable magnetic nanoparticles embedded in cylindrical hydrogel materials for guided actuation via controlled modulation of alternating magnetic field and frequency, and numerically simulated the bending behavior of the hydrogel cylinder to explore the possible causes of bending.
The hydrogel cylinder was synthesized by encapsulating ferromagnetic nano-particles (Fe3O4) within a thermo-sensitive polymer network [-poly(N-isopropylacrylamide) (PNIPAM)], which were polymerized inside the 1.5mm diameter capillary tubes. Inside alternating magnetic field (25-70 Oe, 150-280 kHz), the hydrogel cylinder quickly bended along the longitudinal axis. The bending behavior of the hydrogel cylinder was influenced by the following factors: (a) mechanical strength of the monolith, (b) ac field-induced temperature regulation, and (c) the surface evaporation.
We hypothesized two possible explanations on the bending behavior of the hydrogel cylinder:
a) The heat transfer rate from the cylinder to the base plate was different from the heat transfer rate from the cylinder to the surrounding air. The temperature gradient inside the hydrogel caused different shrinkage rate and thus the bending.
b) Surface friction between the base plate and the hydrogel slowed the shrinkage at the bottom side of the hydrogel while the top side experiences no friction. This force imbalance then caused the bending of the hydrogel.
The validity of these two hypotheses was investigated by using finite element analysis (FEA) numerical methods. A 3D geometric model of hydrogel cylinder was designed in Pro-Engineer Wildfire 4.0 (Pro-E), and numerical analysis was carried out in ANSYS Version 12.0. Structural and thermal analyses were performed under different boundary conditions and load conditions. Our simulation result suggested that the second hypothesis was more likely to explain the bending behavior. More physical experiments are required to further validate our initial simulation result.

Polymer brushes, with one end of the polymer chain tethered onto a solid support, have emerged as versatile soft materials for surface functionalization owing to the high spatial density of functional groups and stimuli-responsive properties. Surface patterning of polymer brushes further extends their applications in a broad range from microelectronic devices, smart surfaces, to bioanalysis and cell study. Moreover, polymer brushes have shown remarkable advantages as building blocks to construct complex 3D nanostructures by employing serial lithographic techniques such as electron beam lithography (EBL) and scanning probe lithography (SPL). However, these methods face the fatal drawbacks of low throughput, limited patterning area and high cost per patterning unit. It remains challenging to realize large-area fabrication of complex 2D and 3D polymer brushes for practical applications in a simple, rapid, and cost-effective manner.
Herein we present a “bench-top” printing method based on atomic force microscope (AFM) to allow massively parallel and serial patterning of 2D and 3D polymer brushes over macroscopically large areas, and its applications in material micro/nanofabrication and microarray-based bioassays. This method, namely polymer pen lithography (PPL), utilizes a low-cost elastomeric pyramidal tip array to direct write initiator molecules on a substrate followed by growth of functional polymer brushes via surface-initiated atom transfer radical polymerization (SI-ATRP). We show that patterned 2D arrays and complex 3D arrays of poly(glycidyl methacrylate) (PGMA) brushes can be readily generated on Au substrate by this method over square-centimeter areas with good uniformity. The shape, feature size and height of the fabricated brush patterns can be well-controlled, with lateral feature size as small as 300 nm and vertical dimension control of 10-80 nm. The patterned PGMA brushes are further employed as resists for wet etching to transfer the pattern into Au substrate. Also the brush-protected Au patterns are demonstrated as hard molds for replica molding of soft stamps. On the other hand, we utilize the patterned PGMA brushes as robust and chemically active platforms for biochips. DNA oligonucleotide and proteins are successfully immobilized onto the 2D and 3D patterned brushes. The bioactivity is verified by testing DNA hybridization and the specific interaction between IgG and anti-IgG.
We anticipate that this low-cost, yet high-throughput “bench-top” serial fabrication of functional polymer brush patterns meets the requirement for lab-scale high speed prototyping and proof-of-concept experiments, and can be readily applied to a wide range of fields including micro/nanofabrication, sensors and actuators, bio-related researches, etc.
This research was sponsored by National Natural Science Foundation of China (Project 51273167) and General Research Fund of Hong Kong (Project PolyU5041/11P).

We report a new strategy for emergency water treatment enabled by the fabrication of superabsorbent cryogels. Robust poly(sodium acrylate) (PSA) cryogels that could swell up to 200 g/g within 15 s were synthesized by copolymerizing N,N&’-methylenebis(acrylamide) and sodium acrylate at -20 °C. Silver nanoparticles (AgNPs) were decorated on the PSA cryogel surface via intermatrix synthesis method. The as-synthesized PSA/Ag cryogels were used in a novel approach to disinfect water that involves (i) allowing the cryogel to swell in contaminated water during which the bacterial cells are inactivated after getting into close contact with the bioactive Ag species on the cryogel pore surfaces, and (ii) recovering the disinfected water by squeezing the water out of the swollen cryogel. Employing this process allowed the cryogels to achieve enhanced disinfection because the squeezed water (i.e., the absorbed water that is squeezed out) was found to be disinfected to a greater extent than that of the bulk water (i.e., excess water outside the cryogel). Particularly, the PSA/Ag cryogel could inactivate more than 5 logs of E. coli and B. subtilis after a 15-s swelling time with minimal Ag release into the treated water. The biocidal function of Ag has been attributed to the toxicity of the dissolved Ag+ ions and/or to the nanoparticle specific physicochemical effects that cause rupture of bacterial membranes. However, controversy still exists in the literature concerning the exact mechanisms. This presentation is dedicated to highlight our latest investigation for better understanding of the multifaceted rapid biocidal mechanism of AgNPs, both in general and in the specific context of the macroporous PSA/Ag cryogels.

The photodegradation of herbicide can reduce the efficiency of control of weeds when occur before the period of weeds control. An ideal herbicide is one that remains active in the environment for a long enough time to control the weeds in a particular culture, but not so long that cause injury to susceptible crops that come in succession and also the environment. In this way, the use of biopolymers as protective agents can increase the efficiency of agrochemicals by blocking ultraviolet radiation, decreasing the exposure of the compounds and thus its losses by photodegradation. In the present study, ametryne was added to starch and montmorillonite and from this mixture, gelatinized starch/clay/ametryne composite was obtained. The aim of this study was to verify the possibility of protective encapsulation of herbicide submitted to UVC irradiation within the starch and clay composite. The effect of inclusion of clay in this composite was compared with composite without clay. The analysis of scanning electron microscopy (SEM), infrared spectroscopy (FTIR) and X-ray diffraction (XRD) showed the effective interaction between the montmorillonite and starch gel. SEM results revealed that the presence of clay minerals was essential for protection of the herbicide present in the nanocomposite. It was also observed a decrease in the crystallinity of the material after exposure to light. It is believed that the MMT into the starch matrix is able of absorbing light and avoid photoexcitation of the herbicide or to accept the excess energy from the molecule by energy transfer or by mechanisms of charge transference dissipating the energy on its surface and avoiding that degrade the herbicide. As a result, the residence time of the herbicide can be substantially increased. These results showed that the encapsulation of ametryne by the nanocomposite (starch gel and montmorillonite) protects the herbicide from photochemical degradation, reducing volatilization which promotes an increase in the activity of the herbicide.

The utilization efficiency of fertilizers is the key element of the development of agricultural productions. However, due to surface runoff, leaching and vaporization, the fertilizers escape to environment to cause diseconomy and environmental problems. The development of starch-based biodegradable polymers offers a possibility to overcome the mentioned problems. They can be used as the fertilizers controlled release matrices to release the fertilizers slowly or in controlled way. As a result, the loss of fertilizers and environment pollution can be avoided or reduced. In this way, this work aims is to produce a nanocomposite able to control release of the ametryne herbicide in a high amounts of an active compounds present in its matrix. A nanocomposite based in exfoliated clay mineral in a starch matrix, incorporating around 50% (w/w) of ametryne was the proposed method. It was prepared systems with 50-80% (w/w) of clay mineral, the montmorillonite. The starch gelification was occurred at 90 0C and montmorillonite was dispersed after the gelification starch process at 70 0C. The materials were analyzed by X-Ray diffraction (XRD) and thermal analysis (TGA-DTA). The results showed that the biopolymer was intercalated with the montmorillonite lamellas. The release test of the herbicide showed that the release, in short time, is controlled by starch amount and in long time is controlled by clay mineral. It was also observed a synergic effect between the components, i.e., the materials as starch/ametryne and montmorillonite/ametryne did not present the same effect of control release observed in the nanocomposite with both materials. However, it was observed that the release is mainly governed by physical barriers to the diffusion of ametryne, since the interaction between starch and ametryne were poor as observed by nuclear magnetic resonance solid (NMR). In the other way, the interactions between the clay mineral and starch were observed, reinforcing the synergistic control of the release observed.

Research on anti-frost has been conducted as the application of superhydrophobicity, however it is generally accepted that superhydrophobic surface have low anti-frost property because large surface area provides a lot of spots where frost can form. On the other hand, SLIPS (Slippy Liquid Infused Surface) have superior liquid repellency and it is said to prevent frost formation by slipping fog. SLIPS film which can prevent frost formation needs high transmittance as frost is caused by differences of temperature between opposite sides on glass windows and lens. Also, the development of multilayer thin films with nanopores containing biomolecules has attracted much attention in material and surface science as one of the optical applications and surface wettability control via LBL (Layer-by-Layer) self-assembly method. In this study, anti-frost film with high transmittance was fabricated by improvement of hydrophobic underlayer of SLIPS. We fabricated films with low refractive index and antireflective property by using LBL and functionalized it by fluoroalkylsilane via gas phase method as the underlayer. The antireflective film with nanopores composed bio-based polymer by LBL showed that the highest transmittance was 97% and the lowest refractive index was 1.20. After adding hydrophobic performance by gas-phase process, the film indicated that the highest transmittance was 97%, the lowest refractive index was 1.23 and the water contact angle is 153°. In addition, we fabricated transparent SLIPS (Slippy Liquid Infused Surface) film by putting a drop of lubricant oil (Krytox GPL 103) on the films and the highest transmittance of this SLIPS film was 98%. Anti frosting test was conducted on the glass substrate, the LBL hydrophilic film, superhydrophobic film and SLIPS film. The SLIPS film delivered superior anti-frost performance compared with other films with maintenance of high transmittance.

With the recent development of medical technological tools, some combination therapies containing both therapeutics and diagnostics are incessantly on demand due to lower sensitivity/selectivity, stronger background noise and inferior biocompatibility of the conventional constituents. Alternatively, a variety of biomaterials for medical applications have been developed promisingly. Here, we report a new versatile luciferase mutant and its exploitation to the use of a self-illuminative cooperative anti-cancer therapy. The luciferase demonstrates both enhanced luminescence and long-term serum stability. In terms of the modified Renilla luciferase, a bacterial subcloning design was lately established; luciferase-encoding DNA sequences were redesigned so that mutant luciferase could be easily expressed in an Escherichia coli system. The mutant Renilla luciferase termed here as “m-Rluc8", confirmed much characteristic enzymatic function and individually showed a 5.65-fold increase in luminescence activity. In addition, the enzyme's physiological stability remained more than 80 % for over 5 days. The luciferase mutants were redesigned as the novel self-illuminative theragnostic cassettes, which are formed via a simple conjugation of both quantum-dot and m-Rluc8. Merged with gold nanorods possessing a photothermal effect, it executed a synergetic therapeutic and diagnostic effect to the target cancer models. It is estimated that the theragnostic cassettes provides a simple design concept but operative medical tool kit toward solid tumors at a time as a innovative paradigm of cancer treatments.

With the advent of new bionanotechnological tools based on bio-inspired engineering concept, an artificial cell organization that attempts the mimicry of both external and internal properties of a cell would be the most promising research field in the modern science. To date, a few have caught much success on the replication of cell interior functions via an in vitro protein production system, in which several transcription or translation factors are optimized to gain target proteins.[1] Externally, a cell construct is usually composed of lipid membranes and genes and several expression ingredients. Most recently, our group proved a lipid-supported polymeric structure as a synthetic nucleus platform.[2] Even yet, there were still few studies for the optimization of the synthetic nucleus exteriors and for the realization of maximization in their functions. Here, we present a novel DNA-genomic networked matrix as an artificial nucleus possessing a potency of protein expressions. Briefly, the synthetic cell structure was made by knotting genes with DNA block crosslinkers and being encapsulated with lipid bilayers. Most interestingly, DNA-genomic networks in a core of the artificial nucleus was shrunk and condensed spatially, leading to the diameter of ~100 nm in a sphere. Similar to the natural nucleus inside a cell, it formed a separate region between lipid bilayer and DNA compact zone, which may be a cytosol in nature. Therefore, it was observed that the artificial nucleus was floating in the cytosol via a Brownian motion. In addition, it contained multi-genes to encode target proteins and produced them in higher yield. The artificial nucleus was also effective to enhance the functionality of the cell. It is highly anticipated that the hand-made cell may provide insight on various research field such as personalized medicine.
[1] Pier L. Luisi, Pasquale Stano. Synthetic biology: Minimal cell mimicry. Nat. Chem. 3, 755-756 (2011)
[2] Sun Ju Bae, Woo Chul Song, Sung Hwan Jung, Seung-Woo Cho, Dong-Ik Kim, and Soong Ho Um. A Gene-Networked Gel Matrix-Supported Lipid Bilayer as a Synthetic Nucleus System. Langmuir. 28 (49), 17036-17042 (2012)

In this work, the hydroxyapatite (HA) mineralized on chitosan (CS)-coated poly (latic acid) (PLA) nanofiber sheets were prepared and compared in term of their mineralization characteristic. Significant calcium phosphate crystals were formed on various concentration of CS-coated PLA fiber sheets with better uniformity after 2 hrs of incubation in 10 times of simulated body fluid (10× SBF). X-ray diffraction (XRD) results further indicated that the composition of the deposited mineral was a mixture of dicalcium phosphate dehydrate and apatite. The chitosan, an cationic polysaccharide can promote more nucleation and growth of calcium phosphate under 0.4% of the chitosan concentration. These results indicated that HA-mineralized on CS-coated PLA fiber sheets can be prepared directly via simply CS coating follow by SBF immersion, and this composites could mimic the structure, composition, and biological functions, and serve as good candidate for BTE.

We report the construction of uniuqe supramolecular fluorescent organic nanotubes derived from self-assembly and inclusion complexation of dendrons with cyclodextrins (CDs) or cucurbituriles(CBs). In particular, their biosensory and delivery characterisctics will be discussed.
The organic nanotubes with unique fluorescence characteristics were fabricated by self-assembly of the amide dendrons with CDs and CBs. The supramolecular approach provideds an facile synthetic route to highlt complex and regular structures with novel function. The unique structural aspect is that the surface of the nanotubes is covered with CDs or CBs. Therefore, the functional group on the surface of the nanotube is controlled precisely by modifying the functionality of CD. In addition, the fluorescent properties of the nanotubes are highly dependent on the exterior environment of the nanotube. The facile functionalization of the nanotube with specific peptide epitope provides high selectivity as a sensory vehicle. Therefore, this type of supramolecular nanotubes exhibited unique biosensory function for proteins, sugars, and ions.
In addition, the nanotube is a usefule carrier vehicle for biomolecules such as DNAs and RNAs. The delivery characteristics of the nanotubes will be discussed as well.

Amyloid fibrils, typically induced by hydrogen bonds between parallel or anti-parallel beta sheets, have recently received intense attention as functional materials in a wide variety of research areas such as nanotechnology and nanomedicine, due to highly ordered structure and robust mechanical properties. In this study, we developed a novel platform for the formation of in-situ nanocomsposites based on the fibrillation of precursor proteins within thin films by controlling intermolecular interactions between amyloid precursor proteins and charged polyelectrolytes (PEs). κ-Caseins, which are one kind of food grade proteins from bovine milk, and poly(acrylic acid) (PAA) were used to build up multilayered thin films by the layer-by-layer (LbL) deposition. The intermolecular interactions within multilayered films, assembled by a combination of hydrogen bonding and electrostatic interactions, were tuned by external pH. When the interactions between κ-caseins and PAA were weaker than the initial interactions of an assembled film by changing pH, thermal incubation of the weakly bound film led to long fibrils of κ-caseins within the film. The fibrils were found to be uniformly distributed across the entire film thickness and the aspect ratio as well as the number density of fibrils increased with the increase in incubation time. Furthermore, we noted that κ-casein fibrils became thicker by the interfibrillar assembly within the film during extended thermal incubation, leading to significant increase in mechanical strength of the nanocomposite film. The present study could serve as useful platforms for reinforced polymeric thin film systems as well as for biomedical applications.

Kinesin is a well-known naturally occurring protein capable of cargo transport upon interaction with a cytoplasmic system of fibers, known as microtubules. Conversion of chemical energy into mechanical work, harnessed by the hydrolysis of adenosine-5'-triphosphate, propels kinesin along microtubules. In fact, kinesin is considered a promising tool in the development of synthetic nano-machines, been widely studied on artificial nanotransport systems in order to carry out directional transport of nanoobjects in a cell-free environment. Here, we report the transport of biotin-functionalized magnetite (Fe3O4) nanoparticles through a biotinylated recombinant kinesin protein onto predefined microtubule tracks using fluorescent-labeled streptavidin as the linker.
The movement of the biofunctionalized magnetic nanomaterial over microtubules filaments could be monitored under fluorescence, and run lengths and velocities of engineered nanotransport devices were monitored. These experiments shed light on the transport of functional hybrid nanoparticles by kinesin-based molecular shuttles to be potentially employed as drug delivery systems.

Flexible, free-standing polymer thin films are typically fabricated on a substrate before being released and captured on a support. The release step becomes more difficult as the film becomes thinner due to the strength of interfacial adhesion between the polymer and the substrate, and can be a limiting factor in the fabrication of free-standing polymer films.
We have developed a method for releasing ultrathin (<100 nm) films of polyvinyl formal (PVF) from silicon wafers by first passivating the silicon surface with a polycation. The passivation is self-limiting based on electrostatic interactions, which eliminates the need to optimize and tightly monitor the process. X-ray photoelectron spectroscopy confirms that the polycation is present on the substrate before and after the deposition and release of PVF, differentiating this release mechanism from the use of a sacrificial interlayer.
The released films stretch unsupported across up to 13 mm, enabling characterization with a macroscopic ball-indenter. Films fabricated from passivated substrates fail at twice the depth of films fabricated using a sacrificial layer, a state-of-the-art method for releasing ultrathin films. PVF films that are 35 nm thick can bear external loads greater than 1.5 g and deflections greater than 3 mm. Such films connect nanoscale thickness with macroscopically relevant length and mass scales.
LLNL-ABS-645242

Most of animals and insects have high developed sensory systems. Especially, spider has extremely sensitive organs to detect force and vibration. Their sensory system is based on a slit system embedded in the exoskeleton. Here, we mimic their sensory system and demonstrate a spider-inspired artificial slit sensor that makes use of ultrasensitive displacement readout using a nanoscale metal crack junction. This device achieves a pressure sensitivity of ~10 kPa^-1 and a vibration sensitivity 100 mV/g, bandwidth greater than 2 kHz and a dynamic range of greater than 40 dB. Also, the devices which we demonstrate are mechanically flexible and shape-deformable so that it can be used on human skin with multi-pixel arrays. The most notable thing is that the sensory system is applicable for voice as well as speech recognition by catching the fine epidermal vibration signal. We believe our approach to forming ultra-sensitive epidermal electronic system for vibration detector and it finally offers a unique avenue for solving the ‘cocktail party problem&’ in the future.

Nitroaromatic (NA) explosives are the primary constituents of many unexploded land mines worldwide [1]. Selective, fast and low-cost detection of NA explosives such as trinitrotoluene (TNT), and dinitrotoluene (DNT), is crucial for military operations, homeland security, and environmental safety [2]. Various analytical and spectroscopic methods have been developed for sensitive detection of NA compounds. These instrumental techniques are mostly expensive and not portable to use in the field. The detection of NA explosives with fluorescent-based sensors have been extensively studied because of their sensitivity, portability, and short response time [3]. The underlying explosive detection mechanism of the fluorescent polymer is photo-induced electron transfer (PET) from the polymers to the NA explosives. The key feature of this phenomenon is the presence of the π-π stacking (excimer) formation between the polymer chains and chromophore groups. This π-stacked formation can significantly enhance the sensing performance of films [4].
In this work, we have fabricated a novel fluorescent thin film based on pyrene-doped polyethersulfone (Py-PES) polymer for detection of nitro-explosive vapours with a rapid and facile method [5]. This fluorescent thin film exhibits extremely fast, selective and portable usage to detect trace amount of NA explosive vapours. The detection of NA explosive vapours can be simply observed by naked eye under a simple UV lamp in less than 1 min with no need of any expensive instrument [5]. The pyrene excimer band (at 471 nm) of film is quenched by 95% for DNT vapour within 30s, while this value decreases to 90% for TNT. Moreover we examined the quenching response of the Py-PES film to different chemicals that may affect the detection efficiency of NA explosive vapours. The results showed that the Py-PES films exhibit selective quenching responses for different compounds[5]. Therefore, the Py-PES thin film exhibits a promising potential to prepare easy, portable, cheap, sensitive and extremely fast-response sensor material for NA explosives detection.
[1] J. S. Yang and T. M. Swager, J. Am. Chem. Soc., 1998, 120, 11864.
[2] J. Yinon, Anal. Chem., 2003, 75, 99A.
[3] Y. Salinas, R. Martinez-Manez, M. D. Marcos, F. Sancenon, A. M. Costero, M. Parra, S. Gil, Chem. Soc. Rev. 2012, 41, 1261.
[4] J. C. Sanchez, S. A. Urbas, S. J. Toal, A. G. DiPasquale, A. L. Rheingold, W. C. Trogler, Macromolecules 2008, 41, 1237.
[5] G. B. Demirel, B. Daglar, M. Bayindir, Chemical Communications, 2013, 49, 6140.

One dimensional (1D) nanostructures of ferroelectric materials have promising potential in the fields of flexible, printed, and nanoelectronics. Here we are reporting improved piezoelectric properties, energy harvesting performance, lower coercive voltage and the polarization direction of 1-D Poly (vinylidene fluoride - trifluoroethylene) [PVDF-TrFE] nanotubes synthesized from melt wetting of anodic aluminum oxide (AAO) mesoporous templates. Field emission scanning electron microscopy images shows that the nanostructures formed from AAO template with 100 nm pore diameter are nanotubes. X-Ray diffraction pattern shows a peak at 19.8° corresponds to the planes of (110) / (200) planes of ferroelectric beta phase. The polarization behavior (P-E) measurements on the free-standing horizontal nanotubes bundles using Piezo force microscope (PFM) revealed that the effective polarization direction is oriented at an inclination to the long axis of the nanotubes. The nanotubes have a lower coercive field of 21 MV/m along the length axis and 40 MV/m in a direction perpendicular to the length axis, which is lower than the thin film counterpart of 50 MV/m. The nanotubes exhibited an enhanced vertical piezo electric d33 coefficient values of 42 pm/V, compared to poled thin film (20 pm/V), when measured in a direction perpendicular to the long axis of the nanotubes. The mechanical energy harvesting performance of the nanostructures are measured by poling at significantly reduced electric fields making it more efficient than the thin film counterpart. An output voltage of ~ 1.8 V is obtained under a cyclic compression pressure of less than 0.5 MPa. These nanotubes are anticipated to found applications in nanoelectronics, where there is need to switch ferroelectric in one direction and to have its switching effect in a perpendicular direction for the functional devices, in addition to pressure sensors, piezoelectric nanogenerators.

The emerging field of nanomedicine offers tremendous promise for improving human health, curing disease, or repairing damaged tissues by applying the tools of nanotechnology to create and control materials with molecular-level medical effects. We think that designed novel polymers with controlled functionalities, molecular weights, polydispersities, molecular architectures and topologies will play essential roles in the development of the field, particularly in the high-value areas of drug encapsulation, transport and delivery, as well as alternative antimicrobial agents. The construction of highly tunable non-covalent hydrogels prepared from biodegradable ABA triblock copolymers will be described. The sustained delivery of cargo from the hydrogel via subcutaneous injection in breast cancer mouse models was shown to be efficacious in reducing tumor size. In addition, cationic hydrogels were shown to be antimicrobial and with the ability to disperse mature biofilms.

Poly(N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc) microgel-based etalons have been shown to exhibit bright visual color, which depends dramatically on solution pH. This is due to the pNIPAm-co-AAc microgels changing their charged state as a function of pH, which is able to modulate the distance between the etalon's two metal layers, hence changing its color. In this study, the etalon was used as one electrode in an electrochemical cell. Application of a potential to the etalon and an ITO-modified slide resulted in water electrolysis, which changed the pH of the solution the etalon was immersed in, therefore etalon could change color in different potentials. We also observed that the etalon's color can be maintained at a single state for many days, and is reversible upon the reversal of the applied potential. This process was shown to be fully reversible over many cycles without breakdown of the device or diminishment of their optical properties.

Ionic Liquids (ILs) are pure salts that are found in their liquid state at temperatures below 100 °C. Many of them are still liquid at room T. ILs are attracting intense research interest on account of their properties: negligible vapor pressures, wide temperature and (frequently) redox stability ranges and their ability to predictably change their physical properties through a systematic variation in the structure of the cations and anions. ILs are an attractive option to many applications: electrochemical capacitors, lithium ion batteries, energy storage at extreme temperatures and electrochromic devices stabilization are some examples. These processes involve the interaction of IL with surfaces, creating thus a solid-liquid (S-L) interface. ILs S-L interfaces are not trivial and they cannot be described by the usual cation-anion double layer pile stacking. Most IL cations contain a quaternary nitrogen or phosphorus group attached to an alkyl chain, consisting of charged and apolar regions and thus behaving more closely to amphiphilic molecules than to charged ions in most cases. A model consisting of three regions describes the ILs interface: The interfacial innermost layer comprises the layer of ions in direct contact with the surface of the solid phase. This layer is often well organized and enriched in one of the ions. The transition zone is the region over which the strong interfacial layer structure decays to the bulk morphology. The third region is the bulk structure, where the IL structure is no longer affected by the presence of the nearby solid surface.
The author presents a study on the structure of ILs S-L interfaces on mica by means of AFM. The novelty of this study consists on the molecular resolution achieved for the in-plane structure of both the interfacial and the transition zones. The results obtained reveal the gradual loose of the hexagonal symmetry imposed by the proximity of the mica surface to a 90° symmetry. The results show surprising lateral cohesivity of the IL layers. The progressive "peeling" + imaging of the IL layers was achieved by controlling the pressure that the AFM tip applies on the sample, in practice by reducing the set point amplitude in the AM-AFM mode.
On a different set of experiments the formation of a cation enriched layer on graphite was studied for both EAN (protic and with a relatively large hydrophilicity) and EMI TFSI (aprotic and hydrophobic). While the tip was the working electrode in the first case, a no conductive tip was placed under an external electric field (EF) in the second. The natural configuration of the IL interface was disrupted by the application of the EF while scanning by AM-AFM. The growing (under negative EF) or the shrinking (when positive EF are applied) of a cation enriched layer on top of the substrate can be monitored. The height of this layer is smaller (approximately 50%) than the ion pair diameter and shows a markedly contrast on the AM-AFM phase signal.

The Eshelbian (or configurational) force is the main concept of a celebrated theoretical framework associated with the motion of dislocations and, more in general, defects in solids. In a similar vein, in an elastic structure where a (smooth and bilateral) constraint can move and release energy, a force driving the configuration is generated, which therefore is called by analogy ‘Eshelby-like&’ or ‘configurational&’. This force (generated by a specific movable constraint) is derived both via variational calculus and, independently, through an asymptotic approach. Its action on the elastic structure is counterintuitive, but is fully substantiated and experimentally measured on a model structure that has been designed, realized and tested. These findings open a totally new perspective in the mechanics of deformable mechanisms, with possible broad applications, even at the nanoscale.

The potential of nano-materials is limited by their tendency to aggregate. This work demonstrates the effective dispersion of bacterial cellulose nanofibrils (BCNs) in organic solvents using exfoliative principles developed for Carbon nanotubes, Graphene and a wide range of other 2-dimensional nanomaterials. [1]

The central point in this solution based technique requires matching the surface energy of the organic solvent to that of BCNs. The dispersion was sonicated and concentration was measured spectroscopically. BCNs were dispersed in a range of solvents. The concentration of dispersed material was measured as a function of solvent surface energy (simply related to the surface tension). Interestingly, the optimum solvents found to disperse BCNs were found to have surface energies close to 85 mJ/m2. Nanotubes, Graphene, and the other 2-dimensional materials (all of which aggregate due to Van der Waals forces) have been dispersed using this methodology all showed optimum dispersion in solvents whose surface energies were close to 70mJ/m2. [1] We propose that the variation shown for BCNs reflects the stronger Hydrogen-bonds that cause BCN to aggregate.
The bundle diameter (D) of BCN successfully dispersed in various solvents was measured using atomic force microscopy. Values of the average bundle diameter ranged from 10.7nm in NMP to 15.8 nm in Benzyl Alcohol. The mechanical properties of BCN nano-papers, produced from dispersions in various solvents, were measured. Mechanical responses were modelled using pervious work on carbon nanotube papers which suggests that the number and nature of the bundle-bundle junctions (NJ) are responsible for the transfer of stress between adjunct bundles. This ultimately determines the strength and stiffness of the papers.[2] Helium Ion microscopy images show that BCNs papers have similar bundle diameter to that of the liquid dispersion. It was shown that BCN nano-paper strength and Young&’s modulus scale linearly with NJ, (where NJ is proportional to ρ^2/D^3 and ρ is the density of the paper). This resulted in NMP based nano-papers being the most mechanically robust with tensile strength=114MPa and Young&’s modulus=1.37GPa. The strains at break values for the papers were solvent independent.
[1] Coleman, Jonathan N, Liquid-Phase Exfoliation of Nanotubes and Graphene , Advanced Functional Materials 2009 19 (23) 3680-3695
[2] Fiona M Blighe, Philip E Lyons, Sukanta De, Werner J Blau, Jonathan N Coleman, On the factors controlling the mechanical properties of nanotube films. Carbon 2008 46 (1), 41-47

Proteins and enzymes, like other nanoscale objects, do not have a liquid phase. That is, when subjected to heating, dry protein powders will thermally degrade and sublime rather than melt. This fundamental absence in the phase diagram arises due to the large short range attractive interactions between the protein molecules. Here, we demonstrate for the first time that the liquid phase of dry proteins can be accessed by increasing the length scale of the interparticle interactions using surface engineering. Specifically, we synthesize functional protein-polymer surfactant nanohybrids via a process of electrostatic self-assembly to yield charge neutral constructs that are liquids in the absence of solvent.
Using a nanohybrid liquid of myoglobin, we show through the use of synchrotron radiation circular dichroism (SRCD) and small angle scattering (SANS/SAXS) that in the absence of solvent, protein secondary and tertiary structure is highly conserved. In addition, the constricted environment of these fluids imparts hyperthermophilic-like behaviour, where the protein refolds completely from temperatures as high as 155 °C.(1) Moreover, through elastic incoherent neutron scattering (EINS) experiments, we have demonstrated that the surfactant corona dynamically replaces water, providing the flexibility and conformational freedom that is analogous to a protein in an aqueous environment.(2) Furthermore, we show that the biological function of myoglobin is retained under almost completely anhydrous conditions, as evidenced by reversible oxygen binding.(3) Finally we present new data showing that protein-polymer surfactant nanohybrid liquids of the industrial enzyme lipase also display hyperthermophilic-like behaviour and can catalyse the hydrolysis of fatty acid esters in the absence of solvent at temperatures in excess of 100 °C.
1. A. P. S. Brogan, G. Siligardi, R. Hussain, A. W. Perriman, and S. Mann, Chem. Sci., 2012, 3, 1839-1846.
2. F.-X. Gallat, A. P. S. Brogan, Y. Fichou, N. McGrath, M. Moulin, M. Härtlein, J. Combet, J. Wuttke, S. Mann, G. Zaccai, C. J. Jackson, A. W. Perriman, and M. Weik, J. Am. Chem. Soc., 2012, 132, 13168-13171.
3. A. W. Perriman, A. P. S. Brogan, H. Cölfen, N. Tsoureas, G. R. Owen, and S. Mann, Nat. Chem., 2010, 2, 622-626.

Self-assembled structures combining nucleic acids and π-conjugated polyelectrolytes (CPE) constitute a novel class of nanomaterials for potential biomedical applications in imaging, sensing, and therapeutic delivery systems, by the combination of unique optical properties of polymers and the DNA (or RNA) recognition properties.[1] For example, the fluorescence properties of conjugated polyelectrolytes have been exploited to selectively detect complementary DNA strands or to probe conformational changes of DNA aptamers upon ligand binding. Despite the fact that self-assembled DNA-CPE hybrid nanomaterials show promising properties, their self-assembly processes and structures and are lacking, while these are essential to establish structure-properties relationships and evolve towards well-defined nanomaterials.
Using a supramolecular approach, we used specific nucleic acids and a series of conjugated polyelectrolytes synthesized by controlled polymerization techniques to give insights into their self-assembly in aqueous media. The effects of relative sizes, charge balance, DNA sequence and topology (ssDNA, dsDNA, quapdruplex DNA) are studied by chiroptical spectroscopy, molecular modeling simulations, and scanning probe microscopy. Importantly, we show that DNA sequence-specific interactions are at play upon self-assembly with conjugated polyelectrolytes, related to the right- or left-handed conformational chirality of polymer backbone within the supramolecular duplexes. The self-assembly is subtly affected by the molar ratio and temperature, with the existence of transitions from left-handed to right-handed helical assemblies.[2] This study provides a better understanding of the supramolecular organization and structure-properties relationships of DNA-CPE nanomaterials.
[1] C. Zhu, L. Liu, Q. Yang, F. Lv, and S. Wang, Chem. Rev. 2012, 112, 4687.
[2] J. Rubio-Magnieto, A. Thomas, S. Richeter, A. Mehdi, Ph. Dubois, R. Lazzaroni, S. Clément, and M. Surin, Chem. Commun. 2013, 49, 5483.

In recent works, it has been realized that the extra-cellular matrix (ECM) is an intricate interweaving of nanometer sized protein fibers (i.e., mainly collagen). Understanding the organization, replication, and formation of micro-fibers forming the ECM is important for answering key biological questions related to cell growth, biocompatibility with implants, and causes for several diseases related to defects in the collagen structure. Replicating the ECM using synthetic processes remains a challenge. Currently there are several tissue engineering methods for replicating the structures found in the ECM. These methods have numerous drawbacks including, (1) lack of processing repeatability and (2) failure to replicate internal fibrillar collagen structures. The use of nano-materials in tissue engineering is also being widely researched and many applications currently exist. This work utilizes a shear-spinning method to self-assemble collagen fibrils in the presence of several different nano-carbons. The nano-carbons are studied as a templating material to aid the self-assembly of collagen fibrils. Both thermal and structural characterizations show that the addition of nano-carbons does not affect the collagen triple helix stability. Wide-angle X-ray diffraction patterns of the collagen fibers show a strong meridional reflection with spacing of 0.282 nm, which remains constant upon the addition of the nano-carbon indicating the collagen molecule repeat distance is also unaffected by the nano-carbons. In addition, a strong equatorial reflection at 1.16 nm is also observed for collagen fibrils, which increases in size with the presence of the nano-carbons indicating a slightly increased lateral spacing of the collagen molecules in the composite fibers. These preliminary results give some insight toward how nano-carbons may have an effect on collagen self-assembly and molecular packing.

The classical view of the airway surface liquid (ASL) is that it consists of two layers - mucus and periciliary layer (PCL). Mucus layer is propelled by cilia and rides on the top of PCL, which is assumed to be a low viscosity dilute liquid. This model of ASL does not explain what stabilizes the mucus layer and prevents it from penetrating the PCL. I propose a different model of ASL in which PCL consists of a dense brush of mucins attached to cilia. This brush stabilizes mucus layer and prevents it penetration into PCL, while providing lubrication and elastic coupling between beating cilia. Both physical and biological implications of the new model will be discussed.

Most superior performing materials found in nature posses a hierarchal composite structure. Natural composites have mechanical properties that vastly exceed the properties of their relatively weak constituents. However, knowledge is lacking on how nature uses morphology and a limited chemical composition to produce a superior performing hierarchal composite material. Exoskeleton scales found on the alligator gar fish (Atractosteus spatula) is an example of highly superior performing material. To gain a better understanding of its enhanced properties, scales have been examined by electron microprobe analysis (EMPA), transmission electron microscopy (TEM), dual-beam focused ion beam (FIB), X-ray absorption near-edge spectroscopy (XANES), and Fourier-transformed infrared spectroscopy (FTIR). Experiment analysis indicates the scale is mainly comprised of collagen and mineral (hydroxyapatite-HAP), in varying proportions and density. Gar scale is usually capped by a dense enamel-like ganoine layer, which is composed of nearly 100% HAP platelets (not needles) with little collagen. The HAP platelets are often arranged in crystallographic continuity. At the base of the ganoine, HAP is most commonly extra-collagen and wraps around the collagen fibrils. Orientation of HAP crystals at the ganoine base follows the collagen long axis. This texture forms a stiffening architecture that also links the ganoine to the underlying layer of tightly woven collagen fibers of the “lamellar bone” region. Extra-collagen HAP is rare in the lamellar bone. The lamellar region gradates into a “diffuse bone” region where collagen fibrils are less organized, loosely packed and only occasionally organized into fiber bundles. The total mineral content decreases away from the ganoine. The results from this research will be used in developing bioinspired methodologies for designing/fabricating superior performing hierarchal composite materials.

The bone tissue results from the intimate association of apatite crystals which are co-aligned with collagen fibrils resulting in a complex composite. Unfortunately, there are several factors that hinder the chemist in his ambition to understand bone formation via its structural characterization directly from an intact bone sample. This is particularly so because, rare are the spectroscopic techniques able to first probe locally the apatite mineral and secondly to point out the possible mineral/organic interactions which occur among such a hybrid-composite. However, as the 31P nucleus is essentially located within the mineral, 31P-based solid-state nuclear magnetic resonance (NMR) experiments allow us to get around these issues. Especially, the use of the standard 1H-31P HetCor experiment permits us to understand which protons and phosphates species are spatially correlated with each other within the apatite crystals. Usually, experiments on bone are biased, as they deal with aged samples partially or completely dehydrated. This is why we conducted NMR experiments on an intact fresh bone sample within two hours after its extraction from the animal. This allowed us to highlight that a significant amount of rigid water surrounds the apatite crystals in vivo.[1]
Following this statement, we undertook a comprehensive study comparing various samples: bone, bone tissue-like matrix, deproteinized bone, biomimetic and highly crystalline apatite, both in their hydrated and dry states.[2],[3] We pointed out that these latest rigid water molecules interact with the mineral surface only when a disordered layer coats the crystalline core of the mineral particles. Furthermore, we identified this disordered mineral layer as an amorphous calcium phosphate (ACP)-related phase.[3] In order to understand what could be the implication of these water molecules in bone, we carried out cryogenic TEM (cryoTEM) observations of apatite crystals samples exhibiting variable amounts of the ACP-like layer. This technique allows the preservation of the hydration of the ACP-like layer. Observations of a water suspension of biomimetic apatite crystals shows the surprising presence of large self-assembled objects up to 500 nm with a preferential longitudinal orientation.[3] These results are supported by wide-angle X-ray scattering (WAXS) experiments where apatite samples soaked in water show a noticeable increase of the intensity of the (002) reflection compared to the ones in the dry state. All of these results suggest that water induces the orientation of the apatite particles in the c-axis direction via the ACP-like layer, leading unexpectedly to an organization quite similar to that found in bone. This proposition is very innovative because this role was commonly assigned to the organic components.
[1] Wang et al. Nature Mater. (2012), 11, 8, 724-733
[2] Wang et al. Materials Horizons 2013, 10.1039/c3mh00071k
[3] Von Euw, Wang et al. Nature Mater. 2013, 10.1038/nmat3787

Soft hybrid bionanomaterials comprising proteins and synthetic polymers provide an attractive opportunity to increase the diversity of chemical milieux encountered by protein-based components because the chemical construction of a surface-bound polymer corona enables the biomolecules to be utilised in a range of dielectric mediums, and potentially, in both the solid and the liquid phase. Accordingly, there are a number of reported examples of enzymes that retain their native structure and catalytic activity in organic solvents when enclosed in a sheath of polymers. In addition, covalent coupling of polyethylene glycol polymer chains to the surface of proteins (PEGylation) has also been shown to elicit reduced immunogenicity, antigenicity and increased circulatory time. However, direct covalent attachment of polymers to the surface of a protein has several drawbacks that arise predominantly from loss of biological function from surface-induced denaturation, intermolecular aggregation, and steric hindrance of active sites.
To this end, we describe a new integrated approach based on a generic strategy in which nanoscale building blocks are used to produce functional protein-polymer surfactant nanohybrids with a diverse range of properties. The approach involves systematically tuning protein-protein interactions via chemical modifications of the biomolecule surface to produce highly adaptable protein-polymer surfactant nanoconstructs that can be either dehydrated to produce functional solvent-free nanoliquids (1,2) dispersed in aqueous solutions to generate artificial membrane binding proteins with tuneable cell affinities, or spontaneously self-assembled to yield hierarchically ordered, catalytically active soft membranes (3). Remarkably, this new class of soft hybrid bionanomaterials retains near-native protein structures that are catalytically active, and exhibit extreme thermophilic behaviour.
References
1. Perriman, A. W.; Brogan, A. P. S.; Coelfen, H.; Tsoureas, N.; Owen, G. R.; Mann, S., Reversible dioxygen binding in solvent-free liquid myoglobin. Nature Chemistry 2010, 2 (8), 622-626.
2. Perriman, A. W.; Mann, S., Liquid Proteins-A New Frontier for Biomolecule-Based Nanoscience. Acs Nano 2011, 5 (8), 6085-6091.
3. Sharma, K. P.; Collins, A. M.; Perriman, A. W.; Mann, S., Enzymatically Active Self-Standing Protein-Polymer Surfactant Films Prepared by Hierarchical Self-Assembly. Advanced Materials 2013, 25 (14), 2005-2010.

Morphologically complex amorphous calcium phosphate nanostructures were synthesized within water-in-oil miniemulsions stabilized by calcium bis(2-ethylhexyl)phosphate (Ca(DEHP)₂) and P123 triblock copolymer surfactants. The solubility of P123 in the oil phase was initially increased by the addition of Ca(DEHP)₂ , followed by addition of aqueous calcium and phosphate ions to initiate calcium phosphate nucleation.
Mineralization of calcium phosphate nanostructures within the aqueous mini-emulsion droplets initially produced short nanofilaments (50-100 nm), followed by the formation of spherical amorphous particles after one hour via a dissolution and reprecipitation mechanism. After three hours, a filamentous calcium phosphate network linking the spherical particles evolved. Solvent evaporation at room temperature resulted in a self-supporting viscous gel stabilized by the intertwined filaments. The calcium phosphate composite gel was tested as a potential biocompatible material to treat tooth hypersensitivity using a bovine tooth model. Scanning electron microscope images confirmed the full occlusion of exposed tooth tubules three days after application of the calcium phosphate/polymer gel.

Low-density hybrid molecular materials with organic and inorganic components engineered at molecular length scales can be made to exhibit diverse mechanical, thermal, and optical properties. We present a novel class of hybrid nanocomposites created through a unique backfilling approach in which selected polymers are homogeneously infiltrated into the pores of a nanoporous glass scaffold, leading to uniform mixing at unprecedentedly small length-scales (~1nm) and axial confinement of polymer chains to dimensions far smaller than their bulk radius of gyration. The second-phase material may be chosen from an extensive library of functionalized polymers, allowing for the development of composites with novel electrical, optical, and mechanical properties.

In this work, we show that it is possible to dramatically alter and improve the mechanical and fracture properties of a nanoporous organosilicate matrix by filling the porosity with a polystyrene second phase. The degree of toughening is shown to increase with the molecular weight of the second-phase polymer, and is also found to depend on processing conditions. We present evidence for a toughening mechanism based on the molecular bridging of individual polystyrene chains, distinct from the more common entanglement and crazing mechanisms exhibited by bulk polymers. This study provides new insight into the mechanical behavior of polymer chains under nanoscale confinement and suggests potential routes for increasing the cohesive strength of soft nanomaterials, where the traditional bulk toughening mechanisms may be absent.

Yujing Liu1,2,3 and Hanying Li1,2,3,*
1MOE Key Laboratory of Macromolecular Synthesis and Functionalization, 2State Key Laboratory of Silicon Materials, 3Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China.
Synthetic single-crystals are usually homogeneous solids. Biogenic single-crystals,1,2 however, can incorporate biomacromolecules and become inhomogeneous solid so that their properties are also extrinsically regulated by the incorporated materials.3,4 The discrepancy between synthetic and biogenic single-crystals inspires an idea to modify the internal structure of synthetic crystals to achieve non-intrinsic properties by foreign material incorporation. Here, Au and/or Fe3O4 nanoparticles were incorporated, through a gel-grown crystallization method, into calcite single-crystals and, as a result, the intrinsically colorless and diamagnetic calcite single-crystals were turned into colored and paramagnetic solids. The gel growth media instead of solutions are necessary to induce the nanoparticle incorporations during which crystals incorporate the gel network and also the nanoparticles trapped in the gels. This result suggests that the nanoparticles are “glued” into the crystals by the gel polymers. Similarly, CdTe quantum dots, Carbon nanotubes and Graphene Oxide nanosheets were incorporated by this gel method to endow single-crystals with other non-intrinsic properties such as photoluminescence . As such, our work extends the long-history gel method for crystallization into a platform to functionalize single-crystalline materials to expand their potential application.
1. Aizenberg, J., Hanson, J., Koetzle, T. F., Weiner, S. & Addadi, L. Control of Macromolecule Distribution within Synthetic and Biogenic Single Calcite Crystals. J. Am. Chem. Soc. 119, 881-886 (1997).
2. Veis, A. A Window on Biomineralization. Science 307, 1419-1420 (2005).
3. Li, H. Y., Xin, H. L., Muller, D. A. & Estroff, L. A. Visualizing the 3-D Internal Structure of Calcite Single Crystals Grown in Agarose Hydrogels. Science 326, 1244-1247 (2009).
4. Kim, Y. Y. et al. An artificial biomineral formed by incorporation of copolymer micelles in calcite crystals. Nature Mater. 10, 890-896 (2011).

We describe an efficient and rapid self-healing thermo-reversible elastomer by simply cross-linking the randomly branched hydrogen bonding network with graphene oxide. Due to the high strength of the graphene oxide, our derived materials have good mechanical property and fast self-healing rate. Compared to other reported systems, our materials are observed to afford 80% mechanical healing in only ~10 min. The healing is still effective even the two severed pieces are left apart for 48 hrs. Moreover, our developed materials exhibited good elasticity and have similar mechanical strength as conventional soft rubbers. This work represents a novel approach towards self-healing elastomers. Our described self-healing elastomers are highly versatile in their applications as they can widely be used as protecting barrier for electronic wires and devices, sealing layer for gas systems, etc.
[1] C. Wang, N. Liu, R. Allen, J. B. Tok, Y. Wu, F. Zhang, Y. Chen, Z. Bao Adv. Mater. 2013, 25, 5785-5790.

High-level control of the nanostructuring of soft polymeric and biomaterials for organic electronic and biomedical use is becoming increasingly important as commercial applications of these materials becomes widespread. Traditional nanoimprint lithographic processes are a route to nanoscale pattern formation in soft materials, and rely on replication via permanent plastic deformation at high pressures and/or temperatures. The fidelity of the final nanopattern depends strongly on the mechanics and flow properties of the target material, and finally the clean debonding of the pattern master, not always facile at high temperatures or strains and nanometer length scales.
Here we discuss a novel method of nanoforming within the context of a new kind of molecular nanoimprint lithography, where relatively small strain confined plasticity is used to promote a local, permanent reorganisation of material within a well controlled volume. We show using nanoindentation - as an enabling test tool - that a nanoscale diamond flat punch is able to instigate plastic molecular rearrangement in nanometer thick polymeric layers at sub 0.1 strains, due a confining state of uniaxial strain where all in-plane strains are inhibited. An approximately one-to-one ratio of hydrostatic pressure and shear stress is injected during loading, which we take advantage of for molecular lithography. In the case of a glassy polymeric layer, a densification of up to 15% at room temperature may be induced in the local volume directly below the punch (replicating exactly the punch geometry) upon loading to strains of 0.2, leaving a rather small residual topographic impression but permanently modifying the molecular arrangement. High-resolution scanning force microscopy data of the residual indentation is used to determine density increase assuming no lateral flow of material. Finite element simulations are used to aid in understanding this lithography process at low strains, where for a simple constitutive elastoplastic model polymer we find quantitative agreement in terms of the experimentally measured density increase within the confined geometry.
We see the future applications of such a process to be a high fidelity lithography based on molecular tuning via density or reordering, and thus would be suitable for applications in flexible electronics and bioscaffold materials, where one could envisage inducing functional changes in the material within the framework of a high fidelity nanopattern.

Single-crystal semiconductor and metal nanostructures are highly desirable for their unique electrical, optical and other properties and have been adapted for novel applications such as optoelectronics, sensors, and energy storage and generation. Here we describe the use of soft matter self-assembly structure formation coupled with laser irradiation as an alternative route to fabricate high quality single-crystal nanostructures. First, block copolymers are utilized as structure directors to achieve epitaxial growth of silicon and nickel silicide single-crystal nanostructures from the silicon substrate. We will demonstrate that our approach is highly flexible and scalable, using colloidal crystal templating to construct crystalline silicon nanostructures with non-close-packed symmetry. We will further explore alternative strategies of coupling soft-matter self-assembly with laser thermal processing to direct and design intricate complex nanopatterned crystalline inorganic materials.

Natural composites such as wood, bone, marine shells and the elaborate structures built by silica-condensing microorganisms have provided much inspiration for the design and synthesis of artificial materials. Efforts here primarily have focused on mimicking a life-like attribute in a synthetic material, for instance self-assembly, self-healing, oscillatory behavior, etc. However in natural systems, it is ultimately the complex behavior of individual cells that enable realization of material systems optimized across multiple length scales. Can this complexity be exploited for the development of synthetic materials? Unfortunately, useful strategies to control structure formation, for instance, at the level of single plant or diatom cells have proven challenging. Alternatively, tissue-derived cultured cells exhibit a nearly limitless range of morphological features in vitro, depending on phenotype and interactions with the surrounding environment. Yet, it is these cells&’ fragility that prohibits their direct use in the production of more durable functional materials. An ability to translate these forms into engineered materials would provide new opportunities for the design and fabrication of particles, assemblies and hierarchical structures.
In this work we describe such an approach, where soft biological surfaces are replicated in silica with nanometer precision, a process we term silica bioreplication (SBR). As described recently (PNAS, 2012, 109:17336-41), we show the scalability of this approach and its application across a wide range of animal cell types. Complete external and internal cellular structures, from the nano- to macro-scale, are captured and preserved in these composites following drying and high temperature processing allowing, for instance, shape-preserving transformation into new materials (e.g., Si, Pt, graphitic carbon). As a striking example of the possibilities afforded this approach, we exploit the well-characterized sensitivity of human erythrocytes to chemical perturbation to generate distinct libraries of non-spherical inorganic particles with tunable properties (e.g., mesoporosity, particle cohesion, bulk surface energy).

Devices constructed by sandwiching poly (N-isopropylacrylamide) (pNIPAm) - based microgels between two thin gold mirrors have been shown to exhibit visual color. The native devices change color in response to temperature as a result of the pNIPAm-based microgels changing solvation state, and hence the mirror-mirror distance. Here, we show that microgels can be synthesized that change solvation state in response to solution pH changes. Furthermore, by confining them between the two Au mirrors, devices that change color with pH could also be fabricated. In fact, various devices capable of measuring solution pH over many magnitudes were fabricated and characterized, which will be presented.

Composites of carbon-based fillers and elastomeric matrices are at the heart of developing technologies such as high-strain sensors/actuators and stretchable electronics due to their unique combination of electrical and mechanical properties. Production of these composites typically includes dispersion of filler particles into an uncross-linked polymer matrix such as liquid polydimethylsiloxane (PDMS) and a subsequent cross-linking of that matrix. We show here that, in the cross-linking of PDMS elastomer, carbon-based fillers such as carbon blacks and functionalized graphene can diminish the extent of cross-linking via a deactivation of small molecule catalysts and cross-linking agents. This deactivation is evidenced by the relationship between the filler loading, the composition at which gelation is observed, and the elastomer cure time. We have studied composite mechanical properties over a broad range of cure mixture compositions, and we demonstrate that materials with a high degree of cross-linking can be obtained when corrections are applied for this deactivation effect. Mechanical and electrical properties of these composites are explored with stretchable conductor applications in mind.

Many bio-composites such as bamboo, tissue interfaces and teeth exemplify how tailoring and optimization of their mechanical performance rely strongly on the creation of specific hierarchical architectures and on the accurate spatial distribution of readily available reinforcing elements [1]. It has been shown, for example, how mollusk shells improve their resistance to contact damage and layer delamination and provide a barrier to crack propagation through a smart spatial design of elastic moduli, which undergo approximately 40% gradual changes between intercrystalline organic layers and stiff ceramic crystallites [2]. In order to mimic the complex architecture of such bio-materials and synthesize composites characterized by continuously graded composition and mechanical properties, an innovative synthetic strategy making use of magnetic field gradients and based on the motion of superparamagnetic Fe₃O₄@SiO₂ core-shell nanoparticles is adopted [3]. It is demonstrated that by lowering the viscosity of the system through particle functionalization, and increasing the magnetic force acting on the nanoparticles upon optimization of a simple set-up composed of two permanent magnets in repulsion configuration, the magnephoretic process can be considerably accelerated. Thus, owing to the magnetic responsiveness of the Fe₃O₄ core and the remarkable mechanical properties of the SiO₂ shell, approximately 150 mu;m thick polymeric films with continuous gradients in composition and characterized by considerable increments in elastic modulus (up to asymp;70 %) and hardness (up to asymp;150%) when going from particle-depleted to particle-enriched regions can be synthesized, even in times as short as 1 hour. The present methods are highly promising for a more efficient magnetic force-based synthesis of inhomogeneous materials whose continuously graded composition not only can be locally tuned to meet the specific mechanical demands arising from non-uniform external loads, but can also efficiently reduce internal stresses and resulting distortion and damage issues normally encountered in multilayered structures.
[1] A.R. Studart, Adv. Funct. Mater. 2013, 23, 4423.
[2] H. Moshe-Drezner, D. Shilo, A. Dorogoy, E. Zolotoyabko, Adv. Funct. Mater. 2010, 20, 2723.
[3] T. Nardi, M. Sangermano, Y. Leterrier, P. Allia, P. Tiberto, J.-A. E. Maring;nson, Polymer 2013, 54, 4472.

The immobilization and hybridization of DNA on the surface are the key issues in DNA based biosensors and have been studied extensively in solution. However, the efficiency of the sensor property is always hindered by the additional challenges involving continuous changes in solution parameters, such as temperature or ionic strength, which are typically used to destabilize and denature DNA hybrids in solution experiments. For any DNA hybridization biosensor, the immobilization amount and accessibility of probe DNA are the vital issues. The nanoparticles in solution could largely increase the immobilization of the DNA on the surface because of the large surface area, but, in this method the nanoparticles are linked to the DNA though the linkers with functional groups, which very often disturb the electrochemical signal of DNA biosensor and reduce the sensor activity. The present study focuses on the hybridization and conjugation of DNA with nanostructured surfaces in solution-less environment as well as demonstrates that self assembled nanostructured surfaces of TiO2, created through ion beam irradiation, achieve hydrophilicity on sputtering and become excellent candidates for DNA conjugation, having enormous applications for biosensor and bio-implants.
Titanium dioxide (TiO2) is considered to be an excellent and promising material for biomedical implants due to its nontoxic nature, corrosion resistance properties and compatibility with many biomolecules. Fabrication of nanodots on Rutile TiO2 surface through ion beam sputtering is an attractive scheme as this technique can produce self assembled, regular arrays of close- packed nanodots, in a single technological step [1]. These ion beam patterned surfaces have interacted with the circular plasmid DNA (pBR 322). Microscopy results and statistical techniques of Power spectral density methods demonstrate that intermolecular plasmid DNA diameter as well as the Persistence length of DNA gets enhanced on ion sputtered TiO2 patterned surfaces. These results indicate the crucial effect of surface morphology on the DNA conformations [2]. Also, the enhancement in plasmid-diameter, after sputtering, leads to a decrease in contact angle between DNA and the surface. Thus, the surfaces become more hydrophilic, and so more biocompatible, as the irradiation fluence is increased.
The presence of oxygen vacancies, which promote charge transfer from DNA moiety to sputtered surfaces, are crucially responsible for these properties as well as for strong conjugation of plasmid DNA with the patterned surfaces. Better biocompatible and hydrophilic nature of TiO2 surface, which increases with ion fluence, is primarily caused by the formation of nanostructures with enhanced oxygen vacancies after ion irradiation.
[1] Subrata Majumder, D. Paramanik, V. Solanki, B.P. Bag and ShikhaVarma, Appl. Phys. Lett. 98, (2011) 053105.
[2] Subrata Majumder, I. Mishra, U Subudhi, Shikha Varma, Appl. Phy. Lett. 103 (2013) 063103

Highly stereoregular polymerisations of p-n-octyphenylacetylene (pOcPA) were performed using a [Rh(norbornadine)Cl]₂-triethylamine catalyst in ethanol at minus;20 and 25 °C to afford yellow and orange polymers, Poly(Y) and Poly(O), in yields of 64 and 99%, respectively. The XRD patterns of Poly(Y) showed a hexagonal columnar crystal with a contracted cis-cisoid helix, ^HexaPoly(Y)^CC. The XRD pattern of Poly(O) matched that of Poly(Y) when heated to 80 °C. The heat treatment of ^HexaPoly(Y)^CC at 100 °C generated two tetragonal crystals: ^Tetra1Poly(R)^CC, containing contracted cis-cisoid helices, and ^Tetra2Poly(R)^CT, containing stretched cis-transoid helices. The helical diameters of ^HexaPoly(Y)^CC before and after heat treatment were estimated using XRD and were consistent with the results of MMFF94 calculations, although the n-octyl alkyl chains of ^HexaPoly(Y)^CC and ^Tetra2Poly(R)^CT did not have linear alkyl chains; a bend in the chains was confirmed by ¹³C CP-MAS NMR. When ^HexaPoly(Y)^CC was heated to 100 °C in the solid phase, the lambda;_max in the diffuse reflective UV-vis spectra shifted from 448 nm to 565 nm. Furthermore, the endothermic transition for ^HexaPoly(Y)^CC occurred at 100 °C in the DSC trace. Therefore, these data corroborated the assertion that ^HexaPoly(Y)^CC thermally converted into ^Tetra1Poly(R)^CC and ^Tetra2Poly(R)^CT.

The yellow colored poly(phenylacetylene), Poly(Y) is obtained from phenylacetylene using a [Rh(norbornadiene)Cl]₂-NEt₃ catalyst in ethanol at 25 °C. The color of Poly(Y) drastically changes into red Poly(R) or reddish-black Poly(B) by immersion in acetylacetone or expose to chloroform vapor, respectively. Poly(R) is also created from Poly(B) by contact with acetylacetone. Poly(Y) is regenerated from both Poly(R) and Poly(B) by reprecipitation from their chloroform solution into methanol. XRD patterns of Poly(Y) and Poly(R) correspond to a pseudohexagonal crystal called a columnar as Stretched cis-transoid and Contracted cis-cisoid helices, respectively. These helical diameters and pitch widths obtained from the XRD measurements are agreed with those of MMFF94 calculation models. The smallest helical pitch width is 3.3 #8491; for Poly(R) and Poly(B). Moreover, information regarding the size and ordering of the vacant space within each polymer is estimated by using ¹²⁹Xe NMR technique.

The agricultural industry worldwide is facing several challenges including the environmental pollution problems (soils and water) caused by the unsuitable control on the use of agrochemicals. Recently, nanotechnology has become an option to improve the existing crop management techniques. Polymer nanoparticles can be used for storage and controlled-release of agrochemicals, such as pesticides and fertilizers. In this regard, chitosan nanoparticles have been considered for agricultural applications due to the capability of size control at the nanoscale and porosity control capability, in addition to biodegradable and biocompatible characteristics. On the above basis, this work focuses on the development of a size-controlled synthesis method for chitosan nanoparticles for further use as a platform for the controlled-release system of agrochemicals. The chitosan nanoparticles were synthesized by polymerization using methacrylic acid in water. Several chitosan precursor concentrations (0.1- 0.8 wt.%) were evaluated in order to manipulate the size of produced nanoparticles. The hydrodynamic diameter of those nanoparticles was determined by means of a Malvern Zetasizer, whereas the morphology and geometrical size were evaluated by Transmission Electron Microscopy (TEM). Chitosan nanoparticles&’ size ranged between 50 and 60 nm when a precursor 0.2 wt.% chitosan solution was used. X-ray diffraction and Fourier Transform Infrared Spectroscopy techniques confirmed the chitosan formation and its interaction with methacrylic acid.

We report the design and characterization of injectable and thermosensitive hydrogels consisting of poly (ethylene glycol)-poly (lactic-co-glycolic acid) (PEG-PLGA) copolymer and hydroxyapatite (HA) particles for potential applications in bone tissue engineering. The biodegradable PEG-PLGA copolymer was synthesized using ring opening polymerization and its chemical structure was controlled so that the resulting hydrogel was in sol-state at room temperature and became gel-state as temperature increasing to body temperature. HA was synthesized using a hydrothermal method to react calcium nitrate tetrahydrate with lecithin, which is a fatty substance occurring in animal and plant tissues, served as the source of phosphate ions. The experimental results exhibited that the morphologies (shape and size) of the HA were controlled by the reaction temperature, pH values, and the addition of lecithin. The effects of HA morphologies on the rheology properties of the resulting HA/PEG-PLGA hydrogels were investigated in terms of storage modulus, loss modulus, and sol-gel transition properties. The test results confirmed that the HA morphologies (size and shape) significantly affected the rheology behavior of the hydrogels. This study provided a better understanding how the particle morphologies affect the rheology behavior of hydrogels and also revealed a crucial point to develop a biodegradable, injectable, and thermosensitive hydrogels for various applications.

The use of non-biodegradable plastics used in food packaging has generated a major environmental concern because of the waste generated. Besides, microbial contamination of food is a serious problem affecting the human health and the food industry. An alternative to face these concerns is the use of biopolymers-based nanocomposites, which are biodegradable and can be modified to provide protection against bacteria based on the tenability of their functional properties. On this basis, the present work focuses on the fabrication of chitosan/cellulose films hosting environmental friendly ZnO nanoparticles (NPs) as an attempt to produce nanocomposites with enhanced bactericidal capacity. The solution casting method was used to fabricate the chitosan/cellulose blend films at various chitosan/cellulose w/e ratios. Highly monodisperse ZnO nanoparticles were synthesized using Zinc acetate and Triethylene glycol (TEG) via a modified Polyol route. ZnO crystal size was controlled by the heterogeneous nucleation approach.
Optical properties of ZnO nanoparticles were studied by UV-Vis Spectroscopy and Photoluminescence Spectroscopy (PL) techniques. The nanoparticles&’ size and morphology were determined by Transmission Electron Microscopy (TEM). Obtained results confirmed the effectiveness of the size-controlled synthesis employed. The chitosan/cellulose/Zinc oxide nanocomposites were characterized by Fourier Transform - Infrared spectroscopy (FTIR) and X-ray diffraction (XRD) methods. The mechanical properties of produced bare and ZnO-bearing composites were determined from stress-strain tests. The Standard Plate Count and the Halo Zone methods were used to evaluate the bactericidal properties of the ZnO nanoparticles, chitosan/cellulose blend films and chitosan/cellulose/ZnO nanocomposites against Escherichia coli.

Polyurethane based nanocomposites have a widespread use in biomedical, structural and high performance engineering due to its high tunable mechanical and functional properties. Moreover, magnetically responsive elastomers composites can also offer tunable properties during use, wireless mechanical actuation, magnetoresistance shape memory systems, for example. However, incorporation of high concentration of nanoparticles, associated with high dispersivity and absence of agglomerates are the main challenges in nanocomposites with high concentration of nanoparticles and still a barrier to reach the full potential of these materials. In this work, we produced a high nanoparticle concentration composite with good dispersion and absence of agglomerates at nanometric scale, using functionalized magnetite nanocrystals (Fe3O4) and a comercial isocyanate terminated polyester urethane. Fe3O4 nanoparticles were synthesized and functionalized in one-step reaction using iron (III) acetylacetonate as precursor and poly(1,4-butanediol) as solvent and functionalizing molecule [1]. After synthesis the nanoparticles were characterized by transmission electron microscopy and it was possible to observe 8 to 10 nm spherical nanoparticles with single crystalline domains. Thermogravimetric analysis (TGA) has shown that the surface organic functionalization was responsible by 30% of the system mass. After removal of excess non-reacted solvent, nanoparticles were dispersed in tetrahydrofuran to facilitate incorporation into the polymer matrix. Bulk and film samples with concentrations ranging from 1 to 50 percent in weight of Fe3O4 nanoparticles (disregarding the organic mass and certified by TGA) were produced by mixing the colloidal dispersion of nanoparticles and the polymer. These high nanoparticle concentration is possible due the high chemical affinity between the organic functionalization and polymer matrix. Polymer hardening was carried out at 30 oC during 6 hours without any atmosphere control. Small-angle x-ray scattering (SAXS) measurements shown good nanoparticles dispersion in bulk samples and scanning electron microscopy realized on thin film samples deposited on aluminum foil has corroborated the result. Also, no agglomerates were observed even in high magnification images and high concentrated samples. Initial measurements had presented mechanical properties similar to the expected for unmodified polyurethane even for concentration as high as 50%.
1. Goncalves, R.H., C.A. Cardoso,E.R. Leite, Synthesis of colloidal magnetite nanocrystals using high molecular weight solvent. Journal of Materials Chemistry, 20(6): p. 1167-1172, 2010.

Nipah virus (NiV), a highly pathogenic member of the Paramyxoviridae family, was first isolated after a 1998-1999 outbreak of fatal encephalitis among pig farmers and abattoir workers in Southeast Asia. NiV and its close relative, Hendra virus (HeV), have been classified as BSL-4 agents due to their broad host range, their numerous routes of transmission, and the high rates of mortality associated with infection. Despite recent advances in understanding the tropism of NiV and HeV, however, there are currently no available vaccines or therapeutics. To reduce the time and cost associated with developing, for example, subunit vaccines or therapeutic antibodies for emerging pathogens, we have constructed complex (~10¹⁰ members) random peptide libraries displayed on MS2 phage virus-like particles (VLPs). These VLPs self-assemble from 180 copies of a single coat protein into a 28-nm icosahedron that can display up to 90 peptides/particle in an accessible surface loop. We have shown that affinity-selection against neutralizing antibodies yields MS2 VLPs that display peptide mimics of natural antigen epitopes, regardless of whether the epitope is linear, conformational, or carbohydrate-based. Furthermore, since MS2 VLPs display peptide mimotopes in dense repetitive arrays, they provoke efficient oligomerization of B cell receptors and induce potent anti-peptide immune responses.
In order to identify NiV and HeV vaccine candidates, we performed affinity selections against several neutralizing monoclonal antibodies that recognize the NiV attachment glycoprotein (G). After two rounds of selection at high valency (90 peptides/VLP) and two rounds at low valency (~3 peptides/VLP), we obtained peptides for each antibody that map directly onto the NiV-G and HeV-G sequences. VLPs that display these peptides in high valency bind to their respective antibodies with high affinity (K_d = 1-20 nM) and induce peptide-specific, high-titer (10⁴-10⁵), adjuvant-independent IgG responses when injected into C57Bl/6 mice. Furthermore, anti-sera collected from immunized mice completely neutralize NiV and HeV pseudoviruses at dilutions as high as 1:10,000 and provide complete protection of ex ovo avian embryos challenged with a lethal dose of pseudovirus. Our results demonstrate that MS2 VLPs are, to date, the only nanoparticles that can be used both for epitope identification and vaccination. This technology holds great promise for rapidly (< 1 month) identifying vaccine candidates, since it requires only convalescent anti-sera against an emerging pathogen and negates the time-consuming steps of pathogen isolation and characterization. As importantly, MS2 VLP-based vaccines can be produced in large quantities using either bacterial expression systems or cell-free protein synthesis at a fraction the cost of subunit vaccines or therapeutic antibodies.

Due to their high mechanical properties, renewability and high surface area to volume ratios, researchers are looking at the preparation and utilization of cellulose nanofibers (CNF) in a variety of polymer applications. Cellulose can be converted to different nanostructures with a variety of physical properties, depending on the origin of cellulose and the method of production. High crystallinity nanocellulose can also be obtained from a process based on high concentrated-acid hydrolysis. In this process, the cellulose is exposed to sulfuric acid for a controlled period of time and temperature. The amorphous parts of the cellulose are removed, leaving single and well-defined crystals in a stable colloidal suspension and promotes the grafting of sulfate groups on cellulose surface, but this process uses a corrosive chemical treatment of fibers and can induce a rapid decrease in cellulose degree of polymerization. Enzymatic pre-treatments had been used to produce cellulose nanostructures, this is a more environmentally friendly, and this route can result in higher degree of polymerization of the cellulose molecules and to maintain high aspect ratio. Exoglucanases are a type of cellulase which is able to attack cellulose at the chain ends resulting in cellobiose units and endoglucanases hydrolyze the amorphous regions randomly. Most methods that use enzymes to perform the hydrolysis contain predominantly endoglucanase and/or exoglucanase. This process results in nanofibers in the single crystal range with most of fibers being in the form of crystalline structure entwined in an amorphous cellulose phase. This is an initial study of the implementation of two new enzymes, an endoglucanase and a concoction of hemicellulases and pectinases to obtain cellulosic nanoparticles from sugarcane bagasse. In this study, sugarcane bagasse were dewaxed and bleached prior to enzymatic action for 72h at 50oC, and then followed by sonication (20min). The concentration between these two enzymes was varied, and for the concentrations and time of enzymatic treatment used, subsequent sonication was necessary for cellulose nanoparticle release. The bleached fibers were characterized by HPLC (High-performance liquid chromatography) and SEM (Scanning Electron Microscopy) and the nanofibers were characterized also by TEM (Transmission Electron Microscopy). XRD (X-Ray Diffraction) was used to evaluate the structural changes on cellulose crystals after each treatment. Cellulose nanofibers were extracted from sugarcane bagasse without damage of cellulose chains, but cellulose nanocrystals (single crystals) and larger diameter nanofibers were attained only after the sonication. A mild decrease of the crystallinity with respect to bleached bagasse was observed indicating that the treatment with any of the enzymes had not influenced this property, it could be evidence that cellulose was defibrillated, releasing nanostructures without damage on cellulose chains.

Recent research articles have focused on the use of carbon nanotubes (CNTs) in polymer matrix composites. CNTs tend to agglomerate, so chemical functionalization can improve its dispersion and physico-mechanical properties of nanocomposites. Poly(hydroxybutyrate-co-valerate), PHBV, is a biodegradable polyester and has physical and mechanical properties comparable with conventional thermoplastics. PHBV has brittleness and poor thermal stability, what restrict its applications, then, the development of nanocomposites is an alternative to improve its performance. In this work, pristine multi-walled carbon nanotubes, MWCNTs, were oxidized in nitric acid for 12 h at 120 degrees celsius. The resulting MWCNTs were reduced by lithium aluminium hydride in tetrahydrofuran, and refluxed for 1 h under nitrogen atmosphere. The functionalization of MWCNTs was investigated by FTIR and Raman spectroscopy, dispersion tests and zeta potential. To produce the nanocomposites, PHBV was dissolved in chloroform and then the MWCNTs were added and sonicated in ultrasonic processor. The solution was poured onto glass plates and allowed to evaporate slowly at room temperature to form a film. The films were prepared with 0,5% (w/w) of pristine, oxidized and reduced MWCNT, and characterized by differential scanning calorimetry (DSC), thermogravimetry (TGA) and conductivity analysis. In the FTIR analysis, bands in 1719 and 1560 cmminus;1 on the spectra of oxidized MWCNTs are assigned to C=O of carboxyl functional groups. These bands disappeared on the reduced MWCNTs spectra, and an increase on the band in 3436 cmminus;1 was observed, related to OH groups. The Raman spectra show no significantly change on the MWCNTs morphology after functionalization. Zeta potential confirms the results from dispersion tests, which show higher stability for functionalized MWCNT. For the nanocomposites, DSC analysis show an increase on the cristalinity and melting enthalpy and TGA curves show a small shift to higher temperatures, both compared to pure PHBV. On both analyses there were no significant differences between nanocomposites with pristine and functionalized MWCNT. PHBV is an insulating polymer, but adding MWCNTs, nanocomposites became conductors. The conductivity is lower for nanocomposites containing functionalized MWCNT.

Chitin is the second most abundant polysaccharide and in the nanofiber form is part of many structural elements in the animal kingdom including the arthropod cuticle, marine mollusk shells, and crab shells. We have demonstrated chitin nanofiber self-assembly from a solution of squid pen beta Chitin in hexafluoro-2-propanol (HFIP). Upon drying, this solution self-assembles into networks of 3 nm alpha chitin nanofibers. Here, we investigate structure properties processing relationship of these chitin nanofiber networks. Network density and chitin nanofiber to nanofiber contact are controlled with processing and affect chitin nanofiber network mechanical properties. Mechanical properties are characterized both at the macroscale using tensile testing and correlated with nanoscale analysis using flat punch indentation. Using a network model the elastic modulus of the individual nanofibers is derived.

Alginate is known to have superior biocompatibility and hence can be used for biomedical application such as scaffold, wound dressing, suture and so on. However, it is difficult to prepare homo alginate fibers due to its rigid chemical structure. To modify the rigid structure of alginate, dialcohols were mixed during solution preparation. Rheological proeprties and viscoelastic properties of the solution were investigated. Complex and shear viscosity, dynamic modulus and relaxation time of the solution were obtained to find optimum condition of spinning dope. Effect of electrospinning parameters on morphology and property change was investigated.
Acknowledgement: This research was supported by the Small and Medium
Business Administration in 2013 (No. S2045799).

Assembly of graphene into functional macroscopic objects, such as sheets, fibers, foams, and other complex architectures, is of enormous research interest. Gelation is a straightforward route to macroscopic functional materials from graphene. Taking advantage of high electrical conductivity, large surface area, and soft hydrated character, graphene gel possesses enormous potentials for supercapacitor electrode, catalytic support, cell growth scaffold and so on. Here we have proposed a facile gelation principle for GO relying on layer-by-layer electroless reduction. Highly hydrated structures stably maintains network of pores within the graphene gel while the continuously overlap of the individual rGO sheets at the pore wall impart high electro-conductivity to it. Benefited from the good electrical conductivity and fluent ion transportation within the hydrated porous network, graphene gel sheet serves as the excellent candidate for electrical double layer supercapacitor. The supercapacitor can be operated at high rate while maintaining a high areal capacitance; a typical combination of figure of merits which still remains a technological challenge. Significantly, the areal capacity maintains high values in high discharge rates. The areal capacity at 1 mA/cm2 is 33.8 mF/cm2, which slightly decreases to 29.89 mF/cm2 at 10 mA/cm2. The areal capacitance values are among the best reported values to date Our graphene gel based supercapacitor demonstrates not only high areal power of 369.8 mW/cm2 but also energy density as high as 2.73 µWh/cm2. The maximum attainable areal energy density is 4.66 µWh/cm2 at the power density of 124 mW/cm2. The maximum areal power density is comparable or higher than the state of art graphene based supercapacitors .

Cellulose nanocrystals (CNC) has been one of the most investigated nanofiller in the production of polymer nanocomposites, because they are not toxic, show high Young&’s modulus, low density, and can be produced by renewable source. These properties make CNC very interesting for the development of new biomaterials. In addition to the mechanical properties, CNC can change other properties of biomaterials, as morphology and swelling degree. In this work the effect of CNC was evaluated in the morphology and swelling degree of hydrogels of chitosan and hydrogels of poly(viny alcohol), PVA, for medical applications. CNC produced by acid hydrolysis of cellulose microcrystals with H2SO4 (64% w/w) were used in the production of chitosan hydrogels and PVA hydrogels. The chitosan hydrogels were produced using glutaraldehyde as crosslinking agent in molar proportion of 1: 2(glutaraldehyde: amine groups of chitosan), while the PVA hydrogels were produced by 10 cycles of freezing-thawing. In both hydrogels, the addition of CNC cause the decreasing of swelling degree compared to pure chitosan and PVA hydrogels. However, while the increase of CNC caused a linear decrease of swelling degree in the chitosan/CNC hydrogels, in the PVA/CNC hydrogels a slight increase of swelling degree was observed in function of CNC concentration. The glutaraldehyde used in the production of chitosan/ CNC hydrogels react with anime groups of chitosan promotes the crosslinking between their chains, it can react with hydroxyl groups of CNC surface, decreasing the number of functional groups responsible by water absorption. But in the PVA/CNC hydrogels the crosslinking occurs by a physical process (without chemical bonds) and therefore the hydroxyl groups of PVA and CNC remain free for water absorption. The SEM images of fracture surface of PVA/CNC hydrogels show a decrease of porosity, while in the chitosan/CNC hydrogels the increase of CNC apparently assists the formation of pores.

Hydrogels composed by different kinds of polymers have been used in a large number of medical applications as contact lenses, artificial cartilage, drug deliverers, wound dressing, scaffolds for cellular growth etc. The control of hydrogels properties as mechanical resistance, water absorption, porosity among other properties is very important to define its application. In this work hydrogels of poly(vinyl alcohol), PVA, were produced with different concentrations of cellulose nanocrystals, CNC, to evaluate the effect of these nanofiller in the hydrogels properties. Aqueous Solutions of 15% (w/v) of PVA with 0, 1, 2 and 3% of CNC (w/w) were prepared and autoclaved. Aliquots of these mixtures were put into plastic tubes and submitted to 10 cycles of freezing at -80 C for 12 hours and thawing at room temperature for 8 hours. The PVA/CNC hydrogels samples were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and swelling tests. The addition of CNC caused the decreasing of porosity of PVA hydrogel, making the material more compact, as observed in the fracture surfaces of samples analyzed by SEM. The pure PVA hydrogels showed a high swelling degree compared with PVA/CNC hydrogels, however, the swelling degree of PVA/CNC hydrogels increased slightly in function of CNC concentration. This result indicates that CNC helps in the water absorption and the decreasing of swelling degree observed for PVA/CNC hydrogels is probably caused by the increasing rigidity of these hydrogels. The presence of water in the samples of PVA/CNC hydrogels even after their lyophilization was verified by DSC.

In carpentry, it is common to apply a thin sheet wood to change the facade of a core material, thus giving it a more pleasing appearance. Similarly, protective finishes ranging from nitrocellulose to polyester and glass can be applied to improve the durability of a core structure. Drawing from this analogy, we explore various methods than enable us to apply molecular veneer and finishes on two-dimensional materials, such as MoS2 sheets, for the purpose of modifying self-assembly behavior. To start, we will discuss assembly of proteins on MoS2 surfaces using native electrostatic interactions, measurement of assembly dynamics through activity and spectroscopic assays and, later, ligand/molecular conjugation to enable tailored interactions with biomacromolecular interactions in vitro and in vivo, in particular, in ways of modulating hemolytic interactions and circulation behavior. Secondly, we will discuss tuning the optical and catalytic properties of MoS2 sheets by molecular veneering, thus changing the way in which they interact with foreign molecules in their environment. Ultimately, our goal is to demonstrate molecular strategies to alter the way two-dimensional colloids, such as MoS2 sheets, interact with molecules in their environment, and use it to shape and build self-assemblies that can be applied towards applications ranging from drug delivery to catalysis.

Energy harvesting devices from the ambient environment or “bio-mechanical” energy from directly coupled to human body are good candidates for the next generation of wearable electronic systems. Here we report a facile fabrication of flexible piezoelectric nano-generators based on highly aligned poly(vinylidene fluoride) (PVDF) nanofibers and printed silver electrodes without any additional poling processes. One-dimensional (1-D) piezoelectric PVDF nanofibers are directly produced onto stamped and sprayed inter-digitated electrodes by electro-spinning. The voltage and current generation of the PVDF piezo-electric sensors were highly affected by the actual contact areas between the electrodes and the PVDF nanofibers. The measured output voltage under periodic bending stress is up to about 1 V. We expect that this facile fabrication technique for PVDF piezo-electric sensors can be easily utilized for their integration into flexible and stretchable functional electronic devices. This concept also can be extended to many applications for sensitive detection of mechanical stimuli.

Polymer based textile composite materials have various application potentials from their excellent mechanical properties with light weight. The superior properties are mainly caused by the reinforcing effect of fiber preform along its aligning direction. On the other hands, mechanical properties along the thickness direction are not sufficiently strong, which is probably caused by weak interfacial bonding between polymer matrix and fiber surface.
In this study, carbon nanomaterials such as graphene oxide and carbon nanotube were embedded on the surface of carbon fabric by electrophoretic deposition method in order to improve the interfacing bonding between polymer and the reinforcing fiber. Effects of the modified reinforcing fiber were investigated in two respects. One is the increase of interfacing area by introducing the carbon nanomaterials, the other is chemical interaction between reinforcing fiber and the carbon nanomaterials. The effects were analyzed by measuring surface energy and adhesive force of the modified fibers. Mechanical properties of the resulting composites were also measured in tensile and shear deformations to verify the improvement of interfacial bonding by the nanomaterial embedding.
It is another important thing that constructs the optimum process condition of composite molding to successfully apply the modified fiber reinforcements to composite products. This study investigated the liquid molding process of the composite materials composed of polymer matrix and the carbon fiber preforms embedded by carbon nanomaterials. Permeability of fiber preform, the process parameter that affects the production speed and quality of the composite, was measured to investigate the effect of nanoscale surface modification on the macroscale processing condition for composite manufacturing. Swelling behavior of fiber preforms was also investigated with respect to the embedding of the carbon nanomaterials, which is related with not only the final fiber volume fraction of composite but also the optimization of the injection and post-filling condition of polymer resin.

Amphiphilic block copolymers undergo self-assembly to form a variety of micelle morphologies in both aqueous media and organic solvents. As new and advanced nanomaterials, multicompartment micelles attract researchers in both academic and application fields due to their potential applications in biomedicine, drug delivery, and biotechnology. The micelle morphology is tuned by molecular parameters, such as molecular weight and block copolymer composition, and solution parameters like copolymer concentration, solvent composition, temperature, and others.
Temperature has been used as a tool to control the block copolymer self-assembly for several years. The determination and control of the sol-to-gel transition temperature in a reliable manner are quite important because the sol-to-gel transition temperature determines injectability, formulation temperature, and sterilization condition. Thus, the kinetics of gel formation is determined by sol-to-gel transition temperature.
The temperature dependence of the shell structure of micelles formed by a deuterated polystyrene-poly(ethylene oxide) diblock copolymer (dPS-b-PEO) in heavy water were investigated with small-angle neutron scattering (SANS). SANS data were analyzed using a core-shell modeled with a structure factor for a hard sphere potential. The shell thickness were obtained from the fits to the SANS data. The shell thickness first decreased with increasing temperature, reached a minimum at some point and then increased with a further increase of temperature. These structural changes seemed to be due to the combined effects of the decrease in hydrophilicity of the PEO block and the increase in thermal motion of the PEO block with increasing temperature.

We report a novel design of highly fluorescent, biocompatible, folic acid (FA) functionalized carbon nanoparticles (CDs) as a carrier for zinc phthalocyanine (ZnPc) PS to achieve simultaneous biological imaging and targeted photodynamic therapy. After longstanding interests in search of benign alternatives such as toxic based fluorescent quantum dot , carbon nanoparticles (also known as C-dots, CDs) have recently emerged as a new class of biolabels by virtue of their biocompatibility, low toxicity, simple preparation and high stability. On top of the high fluorescence properties of CDs, their unique chemical structures allow the integration of active therapeutic molecules into the sp² carbon frame, and their surface functional groups enable further conjugation with other molecules such as biological affinity ligands. These unique characteristics make CDs ideal for simultaneous diagnosis and therapeutics (theranostics).
Specifically, 3.5 nm of CD is synthesized via the thermal decomposition of α-cyclodextrin as a molecular precursor. The surface of CD is subsequently passivated with poly(ethylene glycol) diamine (PEG) to enhance its fluorescence as well as to increase the biocompatibility. The PEG-passivated CD (CD-PEG) is further modified with FA to afford CD-PEG-FA for the targeted delivery to FA-positive cancer cells. FA is an ideal ligand for the folate receptors that are overexpressed in various types of human cancer cells owing to its high affinity for cancerous cells and stability. The quantum yield (QY) of as-prepared CDs using quinine sulfate was measured to be 2.1%. After surface passivation, the QYs increased significantly to 7.8% for CD-PEG and 10.9% for CD-PEG-FA. In addition, as a second generation PS, we used ZnPc which possesses a good cytotoxic efficiency and ZnPc was loaded onto CD-PEG-FA by π-π stacking interactions.
When we investigated the efficacy of targeted delivery of CD-PEG-FA/ZnPc, CD-PEG-FA/ZnPc was also internalized in the HeLa cells with prominent fluorescence signals of both blue (CD, lambda;_ex/lambda;_em = 358/461 nm) and red (ZnPc, lambda;_ex/lambda;_em = 647/665 nm) channel, indicating the successful intracellular delivery of ZnPc by the CD carrier. After the irradiation (660 nm, 30 mW/cm²) for 10 min for photodynamic therapy, significant cell death was observed in CD-PEG-FA/ZnPc (8.2%) with irradiation in cell viabilty test, whereas ZnPc, CD-PEG-FA/ZnPc without irradiation showed 60.9 and 94.2 %, respectively.
We anticipate that the present CD-based targeted delivery of the PS would offer convenient and effective platform for the enhanced photodynamic therapy to treat cancers in the near future due to its excellent biocompatibility, bioimaging and targeting capability, and therapeutic efficacy.

Using a polymeric gel and elastic fibers, we design a thermo-responsive composite film that can be harnessed to manipulate the nanoparticle motion in microfluidic devices. At low temperatures, the fibers are hidden and unable to interact with external fluid. At higher temperatures, the gel shrinks and exposes the fibers to the external solution; hence the exposed fibers can be utilized to hinder the motion of fluid-driven nanoparticles on the film surface. We use dissipative particle dynamics (DPD) to model our system. We construct the gel in a coarse-grained manner by crosslinking polymer chains. We examine the volume phase transition and swelling kinetics of the gel in explicit solvents and validate our model through comparisons with Flory-Huggins theory. During simulations, a hydrophobic nanoparticle is introduced to the outer solvent and driven over the film surface by an external flow. We focus on the effects of the imposed flow, temperature variations, and particle-fiber interactions on the particle motion. We show that by varying the temperature of the system, we can program the film to interact with the particles in a well-controlled manner. Our findings reveal how nanofibers can be used to enhance the properties of thermo-responsive gel coatings.

Fibroblasts play a critical role in normal wound healing, but pathologic hyperactivity can lead to fibrosis, which causes significant clinical morbidity in nearly all organs, including the lungs, kidneys, heart, and skin. Within fibrotic tissue, fibroblasts undergo myofibroblastic differentiation, characterized by the expression of α-smooth muscle actin (αSMA) and increased production of extracellular matrix (ECM) components, such as collagen I and III. TGFβ signaling initiates myofibroblastic differentiation, but the mechanisms that regulate TGFβ signaling in fibroblasts are unclear. Our previously published results demonstrates that biophysical cues, such as topography, down regulate both TGFβ signaling and myofibroblastic differentiation in fibroblasts. Currently, it is unclear the mechanism through which topography regulates myofibroblastic differentiation.
We have developed a series of nanofibrous films fabricated by laminating medical grade polypropylene through a nanoporous polycarbonate membrane. The fiber length and diameter can be reliably controlled allowing tunable topography. As fiber length increases, the characteristic elongated morphology of cultured fibroblasts decreases dramatically. Intercellular tension is also decreased, as marked by a decrease in phosphorylated myosin light chain. Moreover, as fiber length increases, fibroblastic gene expression for components of the TGFβ pathway, including TGFβ1, Smad3 and TGFβ receptor II (TβRII) decreases. This reduction in TGFβ signaling suggests that fibroblasts are becoming insensitive to TGFβ as fiber length increases. As expected, the reduction in TGFβ signaling results in a decrease in staining for αSMA and fibroblastic gene expression of αSMA, collagen I, collagen III. These results indicate that nanofibrous films desensitize fibroblasts to TGFβ, thereby inhibiting myofibroblastic differentiation. A further investigation into the mechanisms behind the interaction between TGFβ and nanotopography, including in vivo assays in mouse models of fibrosis, may elucidate novel material design strategies that could be used to treat fibrotic diseases.

Liquid metals with their unique physical properties are among the list of attractive materials in the fields of analytical chemistry, electronics and experimental physics. A well-known liquid metal is mercury, but has become increasingly unattractive due to its inherent health hazards. Recently, safer liquid metals including eutectic alloy of gallium (68.5%), indium (21.5%) and tin (10%) (galinstan) has become readily available and gained widespread research interests in various applications such as in soft electronic components, stretchable antennas, inter-connectors, electromagnets, MEMS switches and re-configurable wires.
Despite many desirable properties, a major disadvantage of galinstan is that it aggressively amalgams other metals, presenting a major obstacle for interfaces with other solid metals. A semiconductor coating (non-corrosive) on the liquid metal droplet offers a potential solution for this obstacle. Such a system is so called a “liquid metal marble”. In this work, the droplets of galinstan liquid metal droplets were coated with semiconducting nanoparticles (including WO3, TiO2, MoO3, In2O3 and CuO) and also insulating nanoparticles (including Teflon and silica).
The liquid metal marble presents itself as a natural platform that integrates a highly conductive metallic core with semiconductor nanoparticles and hence would be able to operate as active electronic junctions. In this work, p-type (CuO) and n-type(WO3) nano coatings were used to investigate the electronic properties of these liquid metal marbles. These investigations were performed through obtaining the current-voltage characteristics for the various junction configurations including metal/semiconductor (p- or n-type)/metal junctions and metal/p-type semiconductor/n-type semiconductor/metal junctions. It is shown that the electronic junctions formed through this platform follow metal-semiconductor-metal equations which are tuned by altering the coating material. The investigation thus shows that the liquid metal marble platform allow them to be operated as an active electronic junctions which can be attractive in the realization of actively re-configurable soft electronic circuits.

Infection in wounds is caused by the colonization of bacteria and microoragnisms. The presence of bacteria in wounds can delay wound healing and further worsen the infected site. An infected wound not only can cause increased local pain and inflammation, it can also result in bacteremia (the presence of bacteria in the blood), which can lead to infection in other parts of the body. Silver ions have long known of their antibacterial effects in a broad range of bacteria, and silver-containing healthcare products such as wound dressing (eg. Aquacel AG), topical antimicrobial gel (eg. Silvasorb), and catheters (eg. Bard BARDEX) are being used for wound control. While most bacteria on infected wound exist as external biofilm, they can also be present as internal biofilm or as planktonic bacteria. These internal and suspended forms of bacteria are more difficult to remove due to the inaccessibility of the internal biofilm and the diffuse nature of planktonic bacteria. In this work, cellulose nanofibrils (CNFs) functionalized with silver nanoparticles were investigated as potential bacteria clustering agents, and a comparative study of antimicrobial effects of CNF with silver nanoparticles (CNF-Ag) on planktonic bacteria versus static biofilm will also be conducted. Pure rice straw cellulose was used to generate CNFs via TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) mediated oxidation process. Silver nanoparticles was introduced onto the CNFs by exchanging the sodium ions on the carboxyl groups (COO-Na+) with silver ions (COO-Ag+), and then reducing the silver using sodium borohydride. The physical and chemical properties of the various CNFs was characterized using TEM, XRD, UV/vis spectroscopy, and zeta potential measurements. Preliminary TEM and XRD results showed successful attachment of silver nanoparticles onto CNFs, and UV/vis spectroscopy confirmed that the CNF-Ag was stable in high salt media and over large pH range based on zeta potential measurements. Future work will include the evaluation of CNFs with different degrees of substitution (i.e., COO- functional groups) as well as CNF-Ag for their ability to 1) inhibit bacterial growth, 2) promote clustering of bacteria, and 3) exert antimicrobial effects on the bacteria. The clustering and antimicrobial effects of CNF-Ag on bacterial biofilm and planktonic bacteria will also be compared.

The extensive use of chemicals for various purposes in day-to-day life has resulted in environmental contamination with diverse range of organic and inorganic pollutants.[1, 2] These pollutants have adverse effect due to their ability to disrupt the normal physiochemical processes in the body.[3, 4] Hence, developing low cost and efficient adsorbents for their removal from water is at the forefront of many countries. We have utilized hydrothermal carbonization of renewable materials such as sugarcane bagasse (SCB) to generate carbon materials at low temperature. A comparative study was performed by employing the as synthesized and in situ Zr-modified carbonized material to adsorb a series of dyes. In a similar way, monodisperse carbon naospheres were prepared using glucose as precursor material. After post modification, these materials were successfully employed for the removal of nanoparticles form aqueous solution. The functional groups and morphologies of the carbon materials were characterized using FT-IR and FESEM, respectively. Results suggested that the developed materials with Zr loading showed enhanced adsorption capacity as compared to the carbon produced from SCB alone. Similarly, the carbon materials showed very efficient removal of all nanoparticles.

Complex coacervation is a facile approach for the preparation of soluble droplets or coatings in aqueous solutions by mixing polyelectrolytes of opposite charge [1-3]. Recent advancements in scientific methods affords the ability to rationally design and investigate this type of material for applications ranging from electronic ink to drug delivery [4-6]. Here, a model complex coacervate system capable of irreversible degradation under mild conditions has been rationally designed. Temperature, pH, and ionic strength are parameters employed to control the degradation. The degradation of the polyelectrolyte complexes reflects polymer decomposition. DNA and fluorescein are encapsulated as models for cargo. Discussed is the physicochemical nature of this complex coacervate.
1 Agnihotri S.A. et al. Journal of Controlled Release. 1, 5-28. (2004)
2 Lee K.W. et al. Biomaterials. 34, 9877-9885. (2013)
3 Priftis D. and M. Tirrell. Soft Matter. 8, 9396-9405. (2012)
4 Hunt J.N. et al. Advanced Materials. 23, 2327-2331. (2011)
5 Jin K.M. and Y.H. Kim. Journal of Controlled Release. 3, 249-256. (2008)
6 Song J.K. et al. Molecular Cyrstals and Liquid Cyrstals. 1, 263-269. (2007)

Hydrophobic therapeutic agents are frequently suffered from low water solubility and the presence of solubilizing agents such as organic solvents may cause severe side effects. We introduce a novel kind of drug delivery system in this presentation. Precursors of hydrophobic therapeutic agents will undergo a self-hydrolysis process or under redox conditions via non-covalent interactions to form self-supporting hydrogels. The formed nano-structures in the 3D networks of hydrogels are mainly consisting of therapeutic agents themselves. Therefore, the drug loading capacity is very high and it is a novel kind of carrier-free drug delivery system. We will talk about our recent progress of this kind of molecular hydrogels: one focus on taxol and the other one are steroid drugs. We will also discuss the in vivo activity of taxol hydrogel in mouse tumor models. We believe that this novel kind of drug delivery system will have bigger potential to be used in practical because it use clinically used drug molecules as both delivery components and carriers.
References:
1. Wang, H. M.; Wei, J.; Li, D. X.; Yin, Z. N.; and Yang, Z. M.* Biomaterials, 2012, 33(24), 5848-5853.
2. Wang, H. M.; Lv, L. N.; Xu, G. Y.; Yang, C. B.; Sun, G. T.;* Yang, Z. M.* Molecular hydrogelators consist of Taxol and short peptides/amino acids. J. Mater. Chem., 2012, 22, 16933-16938.
3. Gao, J.; Wang, H. M.; Wang, L.;* Wang, J. Y.; Kong, D. L.;* and Yang, Z. M.* J. Am. Chem. Soc., 2009, 131, 11286-11287.

Polymer hydrogel nanoparticles that have an intrinsic affinity for specific proteins are of considerable interest for their potential in biological/biomedical science and biotechnology. In addition to their binding capability, synthetic materials offer the possibility of controlling binding affinity by external stimuli including light, electromagnetic radiation and temperature. This feature can be used for the remote control capture or release of target proteins in a spatiotemporally controlled manner. Recently, we have succeeded in the synthesis and applications of multifunctional, polymer hydrogel nanoparticles with intrinsic binding affinity for target proteins. Polymer hydrogel nanoparticles with an optimized composition selectively capture a protein without denaturation. Furthermore, the nanoparticles can efficiently release the target protein in response to small change in temperature. We are now expanding the scope of the research for development of "nanobiomaterials" for various applications.

We focus on the biomedical applications of short-peptide based molecular hydrogels, including drug delivery, 3D cell culture, bacterial inhibition, and cell surface engineering. We have integrated hydrophobic therapeutic agents with peptides in single molecular gelator to produce a novel kind of self-delivery system. In this system, the drug loadings are high and can be designed. What's more, there are no burst release behaviors. We have also developed several biocompatible methods to form molecular hydrogels, such as those of specific protein-peptide interactions, disulfide bond reduction, vitamin C-catalyzed reduction reaction, etc. The gels formed by these biocompatible triggerations can be applied for 3D cell culture, protein encapsulation and delivery, etc. Assisted by the strategy of 'surface-induced hydrogelation' where gelators can form gels on attracting surfaces below their minimum gelation concentrations in solution phases, we can selectively form thin layers of gels on surfaces of hydrophobic electro spun PCL nanofibers, platelets, cells, and bacterial, which offers versatile strategies for surface modification of hydrophobic nanofibers, platelet aggregation inhibition, cell surface engineering, and bacterial detection and inhibition, respectively. We believe that the research efforts to molecular hydrogels will result in novel strategies to control the fates of biological individuals and novel biomaterials for regenerative medicine.
Reference
1. Zheng, W. T.; Gao, J.; Song, L. J.; Chen, C. Y.; Guan, D.; Wang, Z. H.; Li, Z. B.*; Kong, D. L.*; and Yang, Z. M.* "Surface-induced hydrogelation inhibits platelets aggregation" J. Am. Chem. Soc., 2013, 135(11), 266-271.
2. Wang, Z. H.; Zheng, W. T.; Wang, H. M.; Wang, S. F.; Zhao, Q.; Zhang, J.; Yang, Z. M.*; and Kong, D. L.* "Highly stable surface modification of PCL by molecular self-assembly of a gelator" Chem. Commun., 2011, 47 (31), 8901-8903.

Optical devices composed of two mirrors deposited on either side of a planar, dielectric material are known as interferometers or "etalons". Light entering the dielectric between the mirrors can constructively and destructively interfere, leading to specific wavelengths of light being reflected and transmitted. This affords a device with visual color. The group has demonstrated that color tunable etalons can be constructed using thermoresponsive poly (N-isopropylacrylamide)-based microgels as the dielectric layer. This presentation will detail our research efforts in this area with a focus on controlling the optical properties of the devices and how they can be used for sensing and biosensing applications.

A nanoscale, visible-light, self-sensing stress probe, especially one that does not alter the mechanical properties of the material under study, would be highly desirable for a variety of biological, soft nanomaterial, and materials engineering applications. Here we present CdSe-CdS tetrapod quantum dots (tQDs) as in situ luminescent nanoscale stress sensors for local mechanical properties of polymer fibers. tQDs are synthesized in house and embedded into polymer films or spun into fibers via electrospinning, a readily scalable process amenable to commercial processing. When anisotropic stress is applied to tQDs, the arms torque about the CdSe core, stretching the bonds and changing the optical response. In order to characterize the optical sensing ability of tQDs, we use a homebuilt polymer stretcher interfaced with an inverted fluorescence microscope. Direct comparisons to side-by-side traditional mechanical tests validate the tetrapod as a luminescent stress probe. The tetrapod fluorescence stress-strain curve for tQDs in PLLA matches well with uniaxial stress-strain curves measured mechanically at all filler concentrations reported. With increasing concentration from 3.6% to 20% by weight, we find that the probe sensitivity to strain increases by 60% with minimal changes in the mechanical properties. For example the young&’s modulus of PLLA remains at 2.2 ± 0.4 GPa with up to 20% loading of tQDs. The tQD nanoprobe is elastic and recoverable and undergoes no permanent change in sensing ability upon many cycles of loading to failure.
We further show that the tQDs are capable of optically monitoring more complex mechanical deformations, such as load relaxation and hysteresis; the tQD fluorescence measurements indicate a 20.9% ± 6.24% load relaxation as compared to a mechanically measured relaxation of 29.6% ± 1.16%. The surface chemistry of our colloidal tQDs can be easily modified following established methods of nanoparticle ligand exchange, which can allow them to be easily incorporated into a wide variety of synthetic and biological polymers. We show the tQD to be a highly versatile probe capable of stress sensing in polymer fibers and films of very different structures and compositions, including polymers such as PLLA, PCL, SEBS, and PBD. While in PLLA polymer, the tQD functions as a non-perturbing probe (i.e., one that does not have any impact on the mechanical properties); it functions as a theragnostic sensor in more strongly-interfaced SEBS nanocomposites, capable of predicting its own ability to tune composite mechanical properties.
Since the tQD has high quantum yield and uses visible light, it can be used in commercial stress-sensing applications without using geometrically demanding or low signal to noise methods requiring controlled laboratory environments. Applications include detection of premature crack propagation in thermal, corrosion, and anti-abrasion coatings and in structural polymeric materials for airframes.

Using newly developed computational approaches, we design a gel system capable of re-growth after a substantial section of the material was cut away. Atom transfer radical polymerization (ATRP) is utilized to form gels with preserved “living” chain ends and residual unreacted cross-linking groups. These active species can re-initiate polymerization or participate in further reactions. When this “living” gel is cut, the reactive chain ends are exposed to a solution containing monomer, crosslinker, initiator and catalyst. A “repairing” polymerization occurs from both the new initiators introduced in the outer solution and the reactive chain ends present at the cut site. This new polymerization results in a covalent linkage between the initial living gel and the new gel prepared in the outer solution, and the connection is promoted by the presence of residual cross-linking groups. The height of the new gel is defined by the container dimensions and amount of the reactive species in the outer solution. To design this composite system, we developed the first DPD model for the ATRP process. To validate this model, we probe the polymerization kinetics and calculate gel points in the bulk copolymerization of monomer and cross-linker, and show excellent agreement between our simulations and the experimental results. By measuring the diffusion of the outer solution into the cut gel and characterizing the width and strength of the interface between the initial and new gels, we identify the optimum parameters that result in the formation of a strong interface between the gel layers. Our simulations results are in good agreement with our experimental studies. This strategy not only regenerates “injured” gels, but also offers a novel means to engineer multi-layered composite gels.

The membrane is a natural protective layer for the cell structure, which is made up of lipid bilayer and involves in various cellular functions including cell adhesion, ion conductivity and cell signaling. To mimic natural cell membranes, many different artificial polymeric vesicles spanning a large diameter range from 20 nm to 2 µm have been fabricated using different methods. In particular, the synthetic phosphate lipid vesicles with a nanometer size scale (50 ~ 200 nm) have been found useful as a nanocontainer to encapsulate and store various cargoes, such as enzymes, proteins, DNA, and various drug molecules. Their flexible lipid bilayer surface acts as a permeability barrier to generate a confined volume from zeptoliter to attoliter and offer a more native environment for the biological entities .
Here, we showed that lipid vesicles are ideal nanoreactors at zeptoliter volume level for reactions triggered by small molecules passing through the membrane. Moreover, we also demonstrated that vesicles could be able to work for reactions involving large molecules through SNARE-mediated membrane fusion in a fast and regulated way for the in vivo synthesis of drug molecules in a well-controlled manner.

Graphene is considered the ultimate material for applications in many fields, from electronics to composites and biosensors. Biological studies on graphene and graphene oxide are also currently underway in many laboratories for two main aims: (i) the exploitation of the graphene properties in biological applications; (ii) the assessment of the potential toxicity of graphene layers.
Graphene is usually prepared by the renowned scotch tape technique or by CVD processes. As such, graphene cannot be dispersed in water of biological media, owing to its complete insolubility. Novel ways to prepare dispersible graphene in water are very much needed. Ball milling of graphite in the presence of melamine has been found in our labs to be a method of choice to exfoliate graphite and generate dispersions of graphene in many solvents, including water.
During this talk, we will discuss (i) optimized ways to generate graphene in solvents using ball milling; (ii) the use of graphene in polymer composites for drug delivery purposes; This work was financed in part by the European Union FET Graphene flagship.

Self-assembly of block copolymers (BCPs) has attracted much attention for the last several decades due to their excellent ability to overcome the challenges of conventional semiconducting process. BCPs which consist of two or more immiscible polymeric blocks can create various well-defined patterns with sub-30 nm such as dot, line, ring, and hole structures. Because of the high resolution, scalability, and cost-effectiveness, the BCP nanolithography is one of the most promising candidates for next-generation lithography. However, to get the well-organized nanostructures for the BCPs with high Flory-Huggins interaction parameter (chi;), in general it takes a few to tens of hours. In order to induce fast self-assembly kinetics for the high-chi; poly (styrene-b-2vinylpyridine) (PS-b-P2VP) BCPs, we employed the mixture solvents of toluene and pyridine which are preferential for PS and P2VP, respectively. Well-ordered BCP 10-nm line pattern formation was successfully achieved within 1 minute by using the mixture solvents. In addition, we found that various metal honeycomb nanostructures can be obtained by precisely controlling the volume ratio of toluene and DMF from a cylinder-forming PS-b-P2VP. This practical method may also applicable to other BCPs, providing more opportunity for next-generation sub-10 nm lithography applications.

Understanding how ink transfers to a surface in dip-pen nanolithography (DPN) is crucial for designing new ink materials and developing the processes to pattern them. Herein, we investigate the transport of block copolymer inks with varying viscosities, from an atomic force microscope (AFM) tip to a substrate. The size of the patterned block copolymer features was determined to increase with dwell time and decrease with ink viscosity. A mass transfer model is proposed to describe this behaviour, which is fundamentally different from small molecule transport mechanisms due to entanglement of the polymeric chains. The fundamental understanding developed here provides mechanistic insight into the transport of large polymer molecules, and highlights the importance of ink viscosity in controlling the DPN process. Given the ubiquity of polymeric materials in semiconducting nanofabrication, organic electronics, and bioengineering applications, this study could provide an avenue for DPN to expand its role in these fields.

Hydrogels, composed of hydrophilic polymer network and water, are used as scaffolds in tissue engineering, carriers for drug delivery, valves in microfluidic systems and actuators. The applications of hydrogels are often limited by their poor mechanical properties. Success has been achieved in synthesizing tough but soft hydrogels. For instance, the polyacrylamide-alginate hybrid hydrogel has fracture energy up to 9000 Jm-2, due to the synergy between crack bridging by the network of covalent crosslinks and hysteresis by unzipping the network of ionic crosslinks. Subject to the trade-off of toughness and strength, the hybrid gel has elastic modulus around 30kPa and strength on the order of 100kPa.[Sun, et al. Nature 2012] It is still challenging to synthesize tough and strong hydrogels. Here we adopt the strategy of the hybrid gel, and develop a tough and strong hydrogel from covalently crosslinked polyacrylamide and highly crystallized polyvinyl alcohol. We demonstrate although containing more than 70% water, the gel has tensile strength ~1MPa, elastic modulus up to 2.7MPa, compressive strength beyond 50MPa and fracture energy up to 4900Jm-2. The performance is attributed to the synergy of two mechanisms: cracking bridging by the covalently crosslinked network of polyacrylamide and hysteresis by breakup the lamellar nano-crystallites of polyvinyl alcohol.

Recently, several groups (including us) introduced the concept of tough hydrogels based on interpenetrating polymer network hydrogels using 2 networks cross-linked with sacrificial bonds and covalent bonds, see the work by the groups of Professors Gong (Macromolecules 2012), Suo (Nature 2012), in het Panhuis (Soft Matter 2012) and Zheng (Advanced Materials 2013). These hydrogels, prepared using a “one-pot” synthesis method, exhibited high extensibility, excellent toughness and some recover-ability, and are thought to be suitable materials for the emerging field of soft robotics (Whiteside, Angewandte Chemie International Edition 2011).
In this presentation, we describe the preparation of tough, self-recovering hydrogels from gellan gum and gelatin. The optimal concentrations of gellan gum, Ca2+, gelatin and genipin were identified and the resulting hydrogels were demonstrated to be homogenous and possess excellent mechanical properties. The behavior of the hydrogels when immersed in simulated body fluid was demonstrated and it was observed that calcium was leeched from the hydrogels over time. The mechanical characteristics were found to decrease with increasing swelling ratio. The recoverability of the ICE network hydrogels was shown to be as high as 88 ± 2% when the hydrogels were rested in simulated body fluid (37 °C) for more than 10 minutes between compression cycles.
We believe that this work will be appreciated by the interdisciplinary community of researchers interested in the emerging field of soft nanomaterials (including tough hydrogels which can self-recover) with potential future applications in tissue engineering and soft robotics.

Natural elastomers made from protein extracts have received significant interest as eco-friendly functional materials for underwater adhesion. While some biological materials present interesting properties, they cannot be processed due to chemical cross-linking or thermal instability. However, a recently discovered bioelastomer (the sucker ring teeth SRT extracted from squid species) present thermomechanical properties similar to thermoplastic polymers, allowing the material to be molded into any 3D geometry. Exploiting this unique behavior in natural protein materials, we studied the pressure-induced adhesion mechanism of this thermo-reversible, recyclable and reusable bioelastomer as a potentially inexpensive, environmentally safe alternative to synthetic adhesives. The underwater adhesive is at least two orders of magnitude stronger than synthetic adhesives and ten times the strength of biological adhesives.

Biological matter in cells is often compartmentalized by elastic membranes that assume various shapes such as blood cell membranes, organelles and viral capsids. Shape also plays a key role in the design of synthetic materials such as biomimetic red blood cells or metallic nanocrystals. It is thus crucial to enhance our current capabilities, particularly at the nanoscale, to design membranes of desired shapes. We show that Coulomb interactions can be used as a tool for designing and manipulating shapes of soft elastic nanoshells. The shape changes can be driven by varying environmental conditions such as the electrolyte concentration in the solvent surrounding the shell. Starting from a uniformly charged, spherical elastic shell and using molecular dynamics as an optimizing tool, we find the shape that minimizes the energy of the shell subject to the constraint of total fixed volume for a wide range of electrostatic and elastic parameters. Our simulations reveal that this system exhibits a variety of smooth shapes, which include spheres, ellipsoids, discs, and bowls. The transition from a structure of high symmetry, such as the sphere, to shapes of lower symmetries, such as a disc or a bowl, is achieved by decreasing salt concentration or increasing the total charge on the shell's surface.

Coil-Liquid Crystalline block copolymers exhibit ordered morphologies that reflect the interplay between microphase segregation and liquid crystal (LC) order. Specifically, spontaneous anisotropy in the local chain conformation of Side-Group Liquid Crystalline Polymers (SGLCPs) drives the formation of anisotropic self-assembled microstructures of diblock copolymers consisting of an SGLCP block and a random coil block (polystyrene) when dissolved in a small molecule LC, as observed by SANS and TEM. The local chain conformation and self-assembly of “end-on” and “side-on” coil-LC diblock copolymers with near constant SGLCP block lengths and increasing polystyrene block lengths (40 kg/mol to 120 kg/mol) was investigated. SANS measurements of dilute solutions of these coil-SGLCP diblocks in aligned nematic LC solvent reveal the formation of anisotropic, self-assembled micelles. Combining SANS with both positively-stained and unstained TEM enabled a direct correspondence between the structural features found in the anisotropic scattering and micelle sizes. Size scales of the morphological features at both at the network (>100 nm) and intrachain (5-100 nm) levels were examined. The shape and anisotropy of the micelle core appears to depend on both the SGLCP block and the polystyrene block lengths.

Active contraction of smooth muscle results in the vasomotion of arteries, which adjusts the blood flow and nutrient supply of the organism. The electrical and chemical kinetics coupled with the mechanical behavior of smooth muscle affect the myogenic response of arteries undergoing finite deformation. This paper presents a new constitutive model for the media layer of the artery wall to describe the force produced by the contractile units of the smooth muscle cell. The model includes three major components: electrical, chemical, and mechanical parts. The electrochemical model is a lumped Hodgkin-Huxley-type cell membrane model for the nanoscopic ionic currents: calcium, sodium, and potassium. The calculated calcium concentration serves as input for the chemomechanical portion of the model; its molecular binding causes the relative sliding of thin and thick filaments of the contractile unit. In the chemomechanical model, a new nonlinear viscoelastic model is introduced using a continuum mechanics approach to describe the time varying behavior of the contractile unit. Specifically, this model captures the filament overlap effect, active stress evolution, initial velocity, and elastic recoil in the media. The artery wall is considered as a thin-walled cylindrical tube. Using the proposed constitutive model, the myogenic response is calculated for different transmural pressures. The integrated model is able to capture the pressure-diameter relationship incorporating fewer parameters than previous work and with clear physical meanings.

Soft structures made of elastomers and gels may significantly change their architecture in response to diverse stimuli. When excessive deformation is applied, they may eventually become unstable. Beyond the instability threshold, rapid and dramatic changes of the structural geometry occur and careful design of the initial architecture may lead to the formation of new periodic patterns.
We exploit the non-linear behavior of highly deformable structures to create a new class of adaptive materials that use large deformations and dramatic geometric rearrangements induced by instabilities to rapidly tune their functionalities. Topological changes associated with instabilities are intentionally pursued as an effective approach for tuning the macroscopic response of the structure. Possible and exciting applications include the design of novel materials with adaptive wave propagation characteristics, reversible encapsulation systems, active materials for on-demand drug delivery, robots that can squeeze themselves through small openings and into tight places and materials with unusual properties such as negative Poisson's ratio.

One of the most fascinating properties of biomaterials, and thus far one of the least investigated, is that of self-healing i.e. the property of a material to “repair itself”. This characteristic is observed in nature where tissues like skin or bone are able to undergo long-term reparation after an instantaneous damaging event, but has also been replicated in artificial materials through various strategies. Numerical work on this topic has however been limited, but predictive models could provide the means to minimize cumbersome efforts in experimental work and help optimize desired material properties (e.g. strength, stiffness, toughness, etc). Here, we present a hierarchical numerical approach, which is essential to extract physical properties on the macro scale, since these are a result of the behaviour at smaller size scales. The numerical tool we propose is used to calculate multiscale mechanical properties of self healing materials and discuss in particular the role of material structure, hierarchy and scaling. The numerical results are applied to specific experimental cases on natural materials such as collagen fibrils, or on artificial materials such as self-healing concrete or polymer composites.

The development of predictive methods for deformable electronics calls for an equally composite theoretical foundation that unites traditionally separated fields. We are pioneering theoretical methods that unite polymer physics with liquid state theory, and develop a dynamical algorithm for inhomogeneous polarizable media between capacitor plates. By a quantitative study of the local molecular correlations we can explain the macroscopic behavior and the induced (non-equilibrium) potentials of mean force between the ions, the supporting medium, and the electrodes. Several timescales are found that correspond to different relaxation processes, related to ion diffusion, double layer formation, and the elastic response of the network. The application of an alternating current reveals a complex frequency-dependent response, by which the relative importance of the different underlying processes can be tuned. Typical non-equilibrium forces, generated by the applied field, are found to arise between regions with sharp gradients in the molecular structure or supporting background. The results may inform experimental efforts on noise reduction in soft capacitors, and suggest new functionality based on frequency-dependent non-equilibrium forces.

We present a novel and very simple method for patterning the stiffness of soft polymer nanocomposites. This is achieved by controlling the concentration distribution of magnetite nanoparticles (MNPs) in the nanocomposites. When mixed with liquid precursor of poly-dimethylsiloxane (PDMS) prior to curing, MNPs interfere with the crosslinking reactions by inhibiting the platinum catalyst in the curing agent of PDMS (Sylgard 184, Dow Corning). This in return degrades the elastic modulus (E) of the polymer. In contradiction to the commonly utilized mixture rule, a higher concentration of the MNPs yields a lower E in the PDMS. An externally applied magnetic field (~0.6 T) can be employed to control the concentration distribution of MNPs in the liquid precursor of PDMS via magnetophoresis. If the PDMS is cured while exposed to the field, this concentration distribution is preserved. The magnetophoretic control of MNP concentration distribution and the catalyst inhibiting effect of MNPs were combined in this study to enforce specific pattern on the elastic modulus distribution of the PDMS-MNP composite system. The spatial distribution of the modulus was then mapped using instrumented nanoindentation. We established up to 140% variation in the elastic modulus over a length of 0.5 mm. Thus, a high-resolution, sharp gradient patterning of elastic modulus is possible with this method. The method carries the potential for enabling functional grading of properties in micro-electromechanical systems. It can also serve as an enabling tool for controlling of heterogeneities in material properties for future 3D printing systems.