Yves Brechet Grenoble Institute of Technology
J. David Embury McMaster University
Patrick R. Onck University of Groningen
LL5: Towards Structures
Wednesday AM, April 15, 2009
Room 3022 (Moscone West)
9:30 AM - **LL5.1
Interest and Development of Architertured Steel-based Materials for Automotive Applications.
Olivier Bouaziz 1 Show Abstract
1 , ArcelorMittal R&D, Maizières-lès-Metz France
One of the main driving force for the development of advanced structural materials is weight saving especially in the transportation industry in order to reduce CO2 emission. These new demands provide strong requirements for an optimal choice of materials (inducing a very fierce competition between materials such as aluminium, magnesium and steels in the automotive industry, aluminium, titanium and composite materials in the aeronautical industry). They also lead the engineer to consider solutions where the structural component also provides a functional property. Facing these increasing demands for multifunctional solutions, the classical strategy of the metallurgist to improve properties, using microstructural refinement, reaches its limits: very often the function is not provided by the property only, but by the interplay between the shape, the properties, and possible association of materials. Thus the first part of the presentation outlines the principles of different innovative strategies either to by-pass intrinsic contradiction between properties or to give to structural materials additional functional qualities. These new strategies provide a much richer panel to solve complex multi-criteria requirements then the ones provided by microstructural optimization and shape optimization alone. They propose to explore the potentialities of introducing an intermediate scale between the microstructure and the structure. In a second part examples of developments of architectured solutions are summarized concerning the combination of :-specific stiffness in bending,-strength and ductility,-strength and spring-back.Finally a third part focuses on recent development of architectured materials to combine more efficiently strength and strain-hardening. Indeed the improvement of the strain-hardening is often a crucial challenge for the development of alloys or composites suitable to be formed without localization of the plastic strain. Unfortunately the strain-hardening tends to decrease with an increasing strength. This problem has been widely investigated by metallurgical solution as metal matrix composites, multiphase alloys (as steels or Ti-based]) and using also dynamic hardening mechanism as Tranformation Induced Plasticity or TWinning Induced Plasticity. It is shown how a strategy based on architecture can be a promising alternative.
10:00 AM - LL5.2
Design of Architectured Sandwich Core Materials using Topological Optimization Methods.
Laurent Laszczyk 1 , Remy Dendievel 1 , Oliver Bouaziz 2 , Yves Brechet 1 , Guillaume Parry 1 Show Abstract
1 , SIMaP / Grenoble-INP, Saint-Martin-d'Hères France, 2 , ArcelorMittal Research, Maizières-les-Metz France
Sandwich structures are especially interesting when multiple functionalities (such as stiffness and thermal insulation) are required. Properties of these structures are strongly dependent on the general geometry of the sandwich, but also on the detailed patterns of matter partitioning within the core. Therefore it seems possible to model the core pattern in order to obtain the desired properties. But multifunctional specifications and the infinite number of possible shapes, leads to non-trivial selection and/or optimization problems.In this context of "material by design", we propose a numerical approach, based on structural optimization techniques, to find the core pattern that leads to the best performances for a given set of conflicting specifications. The pattern is defined thanks to a level-set function, and the convergence toward the optimized distribution of matter is performed through the evolution of this function on a fixed grid. This requires for each step the calculation of the performances to optimize and its shape derivative. This time-consuming operation is performed by an appropriate number of finite element calculations wherein the geometry is described by a volume fraction function on a fixed mesh.A first application of this approach is presented for the design of sandwich core materials, in order to obtain the best compromise between flexural rigidity and relative density. The influence of both the initialization (starting geometry) and the formulation of the performances to optimized are detailed.
10:15 AM - LL5.3
Metallic Sandwich Structures with Hollow Spheres Foam Core.
Pierre Lhuissier 1 , Alexandre Fallet 1 , Luc Salvo 1 , Yves Brechet 1 , Marc Fivel 1 Show Abstract
1 , SIMaP - GPM2 - Grenoble INP, Saint Martin d'Heres France
Sandwich structures and foamed materials are typical architectured materials. Their combination provides potentially very performant solutions combining stiffness, strength, energy absorbtion and acoustic damping. The present contribution deals with the integration of a special type of foams ( hollow spheres stackings) into sandwich structures.Stainless steel hollow spheres foams behave classical foam compressive behaviour. However, their strain-stress curves are very smooth and show a very good repeatability, compared to other metallic foams. Therefore these foams are interesting alone but also in sandwich design.We first performed a parametric study of the macroscopic behaviour in uniaxial compression of random stainless steel hollows spheres packing, including sphere thickness effects and sphere size effects. We obtained scaling laws for the Young's modulus, the compressive stress at 25%, the densification strain. Based on these scaling laws, we developed an analytical model to predict the absorbed energy at densification strain.Then one of the studied metallic hollow sphere packing has then been integrated in a sandwich structure with stainless steel faces. Four point bending tests have been performed on various sandwich structures with four core thicknesses and three face thicknesses up to large deflection. We obtained thus the stiffness, the critical load where first damage occurs, the maximum load as a function of the sandwich parameters (core and face thickness). We compared this to classical analytical models and also to numerical simulation in order to be able to predict the load – deflection curves up to large deflection on these kind of sandwich structures.
10:30 AM - LL5.4
Superelasticity, Shape Memory and Stability of Nitinol Honeycombs under In-plane Compression.
John Shaw 1 , Petros Michailidis 1 , Nicolas Triantafyllidis 1 , David Grummon 2 Show Abstract
1 Aerospace Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Chemical Engeering and Materials Science, Michigan State University, East Lansing, Michigan, United States
Nitinol (NiTi) shape memory alloy honeycombs, fabricated by a recently developed brazing method (Grummon, et. al., 2006), have recently demonstrated enhanced shape memory and superelastic properties by exploiting kinematic amplification of thin-walled deformations. So far, prototype honeycombs have been made with densities less than 10%, while retaining useful adaptive properties of the underlying SMA material. The combination of the sparse cellular topology and adaptive properties represents a new class of materials that can be used as light-weight passive or adaptive structural elements that respond to changes in external loads and temperature. In addition, the sparse topology can lead to an order of magnitude improvement in thermal response time and recoverable strain capability as compared to monolithic (100% dense) Nitinol. The realization of such adaptive, light-weight cellular structures opens interesting possibilities for design and novel applications, including reusable energy absorbing structures, highly resilient structures, light-weight armor, thermal actuation materials, vibration isolation, and biomedical implants. This talk addresses the consequent need for design and simulation tools to make effective use of such structures, and analyzes the multi-scale stability aspects during thermomechanical, in-plane compression loading. An in-depth parameter study is shown of the influence of different material laws on the behavior of honeycombs of finite and infinite extent having perfect and imperfect initial geometries.
10:45 AM - LL5.5
Numerical Simulations of Topologically Interlocked Materials Coupling DEM Methods and FEM Calculations: Comparison with Indentation Experiments.
Charles Brugger 1 , Marc Fivel 1 , Yves Brechet 1 Show Abstract
1 Grenoble Institute of Technology, SIMaP-GPM2, St Martin d Heres France
Interlocked materials are architectured materials from their very definition. Inspired from civil engineering, they are formed of blocks of a variety of geometry which are prestressed by a frame, and cannot slide freely one away from the other because of topological constrains. Even made of brittle materials, such materials can nevertheless have a very high damage tolerance (a crack in a block doesn’t propagate into the neighbouring one) and a high flexibility (due to the possible relative movements of the blocks). The macroscopic behaviour of these “interlocked materials” depends on the block geometry and constitutive material, on the friction coefficient and on the intensity of the prestress. In addition, since the “building block scale” is compable to the global structure dimensions, possible sample size or block size effects are expected.In order to model these influences, we have developped a numerical simulation using Discrete Element Modelling, where the interaction laws between the bocks is computed by a FEM model. The block geometry investigated is the simplest possible one, a cube. Experimental data are obtained from plaster cube interlocked structure. Mechanical response of the assembly is tested in indentation loading conditions both experimentally and numerically. The main numerical result is the existence of a master curve relating the stress and the indentation depth, which allows summarizing rapidly the main features observed experimentally. The most striking phenomenon is the existence of an effective negative stiffness during unloading.
12:00 PM - LL5.7
Materials of Controlled Shape and Stiffness with Photocurable Microfluidic Endoskeleton.
Suk Tai Chang 1 , Ahmet Ucar 1 , Garrett Swindlehurst 1 , Robert Bradley 1 , Frederick Renk 2 , Orlin Velev 1 Show Abstract
1 Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 Center for Packaging Innovation, MeadWestvaco, Raleigh, North Carolina, United States
Microfluidic systems have been widely investigated for biological analysis, organic synthesis and nanoparticle fabrication. The potential of microfluidics in other areas of technology, such as microfluidic-enhanced adhesion, microsolidics and self-healing materials has only begun to be realized and investigated very recently. We report here new microfluidic materials in the form of flexible sheets that can be solidified on demand to acquire specific shapes. They are based on microfluidic channel networks in a thin PDMS layer filled with photocurable SU-8 photoresist. The materials formed in this way possess the unique ability to adopt and retain a certain user-defined shape. When the microchannel networks are deformed and exposed by UV light, the photoresist inside the channels is solidified and acts as endoskeleton within the PDMS layer, locking in the programmed shape. The bending and stretching moduli of the materials with solidified endoskeleton increase drastically and after external forces are applied, the "memorized" shapes are recovered. The elastic modulus of the microfluidic composite material increased linearly as a function of the volume fraction of SU-8 in the PDMS layers – up to 40 times higher than that of the pure PDMS layer at about 20 % volume of SU-8 photoresist. The estimations of the elastic modulus using analytic expressions for 3D composite materials were in good agreement with the experimental data. The photo-cured microfluidic endoskeleton structure had also higher bending modulus increasing with the volume fraction of SU-8 photoresist in the PDMS layer. Thus the sheets become stiffer and their shapes are more recoverable. The permanent preservation of the shape of solidified microfluidic sheets could be used in making instant containers and supports on demand, creating "exoskeletons" for delicate package contents and multiple other applications.
12:15 PM - LL5.8
Development of Smart Textiles Using Atmospheric Pressure Plasma Polymerization.
Khushboo Mittal 1 Show Abstract
1 , North Carolina State University, Raleigh, North Carolina, United States
Aptly called ‘Smart textiles’, they not only look smart but also act accordingly. Often, these are multifunctional and have the ability to respond to external stimuli as requisite for the user. This research focuses on the development of analogous intelligent textile which is hydrophilic and hydrophobic concurrently. This implies that these textiles have the ability to absorb the sweat of the wearer, simultaneously repelling off any external liquid contaminant spill. The design of this style of smart textile is novel and unexplored which in this study is achieved by the in-situ atmospheric plasma polymerization . A polyester/polyurethane blend and cellulose is used for this purpose, on which a fluorocarbon monomer layer is polymerized using helium gas glow discharge plasma treatment at atmospheric pressure. Optimization of fluorocarbon and helium flow rate, plasma frequency, plasma power and treatment time was done in order to enhance performance exclusivity. It is found that a conventional fabric can be transformed into this intelligent, multi-functional fabric in 8-10 seconds of treatment time.
12:45 PM - LL5.10
Metallic Hollow Spheres Packing Manufacture.
Cecile Davoine 1 , Regis Bouchet 1 , Sebastien Mercier 1 , Fabienne Popoff 1 , Anais Goetzfried 1 Show Abstract
1 Metallic Materials and Processes Department, Onera, Chatillon France
Cellular metal structures has been gaining interest for multi-functional applications where weight lightening combined with acoustic damping and ultra high temperature application is required. An application of such a material concerns the decrease of internal noise produced by aeronautical turbo engines. Compared to conventional metal foams, the hollow sphere packings allow high degrees of porosities and structural regularity. This kind of architecture shows a mechanical and acoustical energy absorption ability, which can be adjusted by the structure and the basic material.However their specific properties in terms of mechanical, acoustic, and oxidation resistance, depend strongly on the manufacture process. Therefore the developpement of fabrication technologies for panels with hollow sphere cores includes screening of suitable joining techniques and relevant test methods. Here, two different processing concepts are presented: the joining of single cells by brazing, and a powder metallurgy process using a sintering step. In the brazing process, a thermal treatment is performed to melt the brazing material which concentrates to the contact points between neighbour spheres by capillarity and forms meniscuses. Compared to classical brazing process, the technological barrier is to control the optimum quantity of brazing material. Different processes have been investigated to bond nickel hollow spheres. We performed a screening of the brazing layer thickness and material to evaluate their impact on the architecture. The SEM characterization of brazed shells proved that a “brazing-diffusion” thermal treatement homogenizes the composition in order to obtain a monophased microstructure.The sintering process consists in coating polystyrene spheres with a binder/metal powder mixture and subsequently sintering the metal to obtain a dense metal shell and the bonding between spheres. Compared to classical sintering (bulk material), the hard point is to ensure a contact between spheres during sintering without collapsing the structure.The resulting architectures will be compared: thicknesses of the shells, porosities, microstructures, size of meniscuses. In both cases, the performances in term of mechanic and acoustic damping will be evaluated. Some possible applications of these advanced lightweight materials involve high temperature and an aggressive environment. Thus, the influence of the oxidization phenomenon on the specific properties of the hollow spheres packings has been evaluated.
Yves Brechet Grenoble Institute of Technology
J. David Embury McMaster University
Patrick R. Onck University of Groningen
LL7: Multifunctional Materials II
Thursday AM, April 16, 2009
Room 3022 (Moscone West)
9:30 AM - **LL7.1
Multifunctional Composite Materials for Structural Energy Storage Devices.
Natasha Shirshova 2 , Alexander Bismarck 2 , Joachim Steinke 1 , Emile Greenhalgh 3 , Paul Curtis 3 , Milo Shaffer 1 Show Abstract
2 Chemical Engineering, Imperial College London, London United Kingdom, 1 Chemistry, Imperial College London, London United Kingdom, 3 Aeronautics, Imperial College London, London United Kingdom
This paper introduces a new multifunctional composite material that can simultaneously carry mechanical loads whilst storing (and delivering) electrical energy; the current embodiment is an electrochemical double layer capacitor, based on polymer gel electrolytes reinforced by carbon and glass fibres. In order to simultaneously maximise the mechanical and electrical performance, both the reinforcing fibres and the matrix have been modified. Rather than using conventional activated carbon fibres, structural carbon fibres were treated to produce mechanically robust, high surface area material. A mesoporous silica phase was introduced into the polymer gel electrolyte via a templated sol-gel process in order to improve the mechanical performance whilst retaining ionic conductivity. Working structural supercapacitor composite prototypes have been produced using a hand lay-up approach. The electrochemical performance of the composites has been examined using impedance spectroscopy, cyclic voltammetry and charge-discharge measurements, whilst the mechanical performance in compression was characterized using a four point bending technique.
10:00 AM - LL7.2
Acoustic Behavior of Organically Modified Silica Aerogels.
Winny Dong 1 , David Dong 2 , Travis Thompson 1 , Elizabeth Scott 1 , Michael Pantell 1 , Diana Simon 1 , Tanya Faltens 1 Show Abstract
1 Chemical and Materials Engineering, California State Polytechnic University, Pomona, Pomona, California, United States, 2 , Veneklasen Associates, Santa Monica, California, United States
Composite aerogels (with varying concentrations of silica and poly-dimethylsiloxane) were developed and their acoustic absorption coefficient as a function of composition have been measured. The polydimethylsiloxane modified the ceramic structure of the silica aerogels, decreasing the material’s modulus of elasticity and bulk modulus while still maintaining the high porosity of the aerogel structure. The composite aerogels were found to have excellent absorption characteristics in the 1000 Hz frequency range, approximately 40% better than that of commercial fiberglass. The incorporation of the PDMS into the silica aerogel successfully modified the structure to reduce the rigidity of the aerogels. The results show that these materials have a large surface area (> 400 m2/g) and small pore sizes (d ~ 5 nm). Although these composites appear homogeneous, SEM images also suggest phase separation at the nano-scale. The composite aerogels have a significantly different acoustic absorption characteristic compared to both fiberglass and undoped silica aerogels. The absorption coefficient peak (95% absorption at ~ 1000 Hz) as a function of the concentration of PDMS will be discussed.
10:15 AM - LL7.3
Novel Collective Properties of Artificially Patterned Thin Film Two-phase Magnets: Hard Magnetic Dots Embedded in a Soft Magnetic Film.
Christian Jooss 1 , Sven Schnittger 1 , Sibylle Sievers 2 , Uwe Siegner 2 Show Abstract
1 Institute of Materials physics, University of Goettingen, Goettingen Germany, 2 , Physikalisch-Technische Bundesanstalt , Braunschweig Germany
In order to study novel emergent collective magnetic properties due to magnetic interactions of two different types of nano- and microstructured magnetic materials, two-dimensional patterns of square dots embedded in a magnetic film with different geometries were fabricated. We use hard magnetic (001) L10 CoPt squares embedded in a Permalloy matrix  and ferrimagnetic CoFe2O4 squares embedded in a La0.7Sr0.3MnO3 film. The structural and magnetic properties of these arrays were characterized by scanning electron microscopy, magneto-optical measurements, atomic force and magnetic force microscopy. Magnetostatic coupling on different length scales was observed. This coupling modifies both the magnetic properties of the dots and the matrix material. The emergent new collective magnetic properties cannot be understood as a superposition of the properties of the individual materials. To be more specific, in periodic arrays of embedded CoPt squares, the stray-field interaction induces a symmetry-breaking long-range ordered domain pattern in the soft magnetic matrix and short-range correlations of edge domains in adjacent CoPt squares. The results have impact onto the tailoring of new magnetic properties by micro- and nano-structured magnetic composites  S. Schnittger, S. Dreyer, Ch. Jooss, S. Sievers, and U. Siegner, Appl. Phys. Lett., 90, 042506 (2007)
10:30 AM - LL7.4
Sound Absorption Characteristics of Porous Steel Manufactured by Lost Carbonate Sintering
Miao Lu 1 , Gary Seiffert 2 , Carl Hopkins 2 , Yuyuan Zhao 1 Show Abstract
1 Department of Engineering, University of Liverpool, Liverpool United Kingdom, 2 School of Architecture, University of Liverpool, Liverpool United Kingdom
Lost Carbonate Sintering (LCS) is a novel technology for manufacturing open-cell porous metals. It offers significant advantages over competing technologies, combining low production cost and accurate control over the pore structure. This paper studies the sound absorption characteristics of porous steel manufactured by LCS by the impedance tube method. The sound absorption coefficients of single layer and multilayer porous steel samples with different pore sizes (250-400, 400-710, 710-1000 and 1000-1500 microns) and porosities (60, 65, 70 and 75%) were measured. In the low frequency range, the sound absorption coefficient increased with increasing porosity, pore size and sample thickness. In an assembly of four porous steel samples with different porosities, the order of the samples had a great effect on the sound absorption coefficient. The sound absorption coefficient of the assembly with decreasing porosity was nearly 40% higher than that of the assembly with increasing porosity along the incident sound wave direction. The results showed that LCS porous steel has a great potential for sound absorption applications, especially in harsh environments where conventional sound absorbing materials cannot be used.
10:45 AM - LL7.5
Nanoparticle based Multilayers as Multifunctional Optical Coatings.
Hernan Miguez 1 , Mauricio Calvo 1 , Silvia Colodrero 1 , Manuel Ocana 1 , Olalla Sanchez-Sobrado 1 Show Abstract
1 Institute of Materials Science of Seville, Spanish National Research Council, Seville Spain
Herein we introduce nanoparticle based periodic multilayers  as base materials to create different types of multifunctional coatings that combine good optical, mechanical and diffusion properties. The technological potential of these versatile materials is demonstrated by showing applications in the fields of sensing, photoconducting materials, and photovoltaics. Due to the porous nature of such structures, liquids and gases can infiltrate or condensate, respectively, within the interstices, causing a variation of the refractive index of the layers. This gives rise to clear but gradual changes of the optical response, either when liquids of increasing refractive index are infiltrated in the structure or the partial pressure of different ambient gases is varied in a closed chamber. Also, photoconducting Bragg mirrors can be built by precise control of the spatial variation of the refractive index in a pure titanium oxide multilayer. Rationally placed within a dye-sensitised solar cell, they give rise to a significant enhancement of the solar-to-electric power conversion efficiency through the amplification of sunlight absorption. In this case, the pores in the multilayer allows for the diffusion of the electrolyte through it while maintaining a high reflectivity that confines incident photons in the dye-sensitised layer. Direct observation of both optical absorption and photocurrent resonances can be seen. S. Colodrero, M. Ocaña, H. Míguez, Langmuir 24, 4430, 2008. S. Colodrero, M. Ocaña, A.R. González-Elipe, H. Míguez, Langmuir 24, 9135, 2008. M.E. Calvo, S. Colodrero, J.A. Anta, M. Ocaña, H. Míguez, Adv. Func. Mater. 18, 2708, 2008 (inside cover story). S. Colodrero, M. Ocaña, A. Hagfeldt, H. Míguez, Adv. Mater. 2008, in press.
LL8: Surface Functionalization and Bio-inspiration I
Thursday AM, April 16, 2009
Room 3022 (Moscone West)
11:30 AM - **LL8.1
Magnetotactic Bacteria – a Natural Architecture Leading from Structure to Possible Applications.
Kui Zhang 1 , Tian Xiao 2 , Longfei Wu 3 Show Abstract
1 Department of Physics, University of Reims, Reims France, 2 , Key Laboratory of Marine Ecology and Environmental Sciences, CAS, QingDao China, 3 , Laboratoire de Chimie bactérienne, CNRS, Marseille France
Magnetotactic bacteria are aquatic micro-organisms which have the specific capacity of navigation along an applied magnetic field. Such property is related to the formation of chains of magnetic crystals called magnetosomes. All magnetotactic bacteria synthesize nano-sized intracellular magnetosomes which are surrounded by ultra-thin bio-membranes. If the magnetosome chains serve as compass for navigation of magnetotactic bacteria, the cell flagella are considered as the driving force for propelling the bacteria forward. This presentation describes various functions of the architectural structure of magnetotactic bacteria as well as their possible applications in biotechnology.
12:00 PM - LL8.2
Biocatalytic Mechanotransductive Surfaces Based on Cryptic Site Architectures.
Damien Mertz 1 , Cedric Vogt 1 2 , Joseph Hemmerle 1 , Jerome Mutterer 3 , Vincent Ball 1 , Jean-Claude Voegel 1 , Schaaf Pierre 2 , Philippe Lavalle 1 Show Abstract
1 UMR595 Biomaterials, INSERM, Strasbourg France, 2 Institut Charles Sadron, CNRS, Strasbourg France, 3 Institut de Biologie Moléculaire des Plantes, CNRS, Strasbourg France
Fibronectin, like other proteins involved in mechanotransduction, has the ability to exhibit recognition sites under mechanical stretch (1). Such cryptic sites are buried inside the protein structure in the native fold and become exposed under applied force.4 This unmasking then activates specific signalling pathways. Here we report the design of a new family of polymeric functionalized nanoassemblies which mimic the activation mechanism of cryptic sites.The nanoassemblies consist of a first polyelectrolyte multilayer(2) strata acting as a reservoir of enzymes capped with a second polyelectrolyte multilayer strata acting as a mechanically sensitive nanobarrier (3-4). The biocatalytic activity of the film is switched on/off by mechanical stretching:i) In the absence of stretching, no enzymatic activity is detected.ii) Once the film is stretched over a critical stretching degree, the embedded enzymes are exhibited and the enzymatic reaction takes place, catalyzing products formation and their delivery in the solution.iii) When returning to the unstretched state, the enzymes are again buried inside the film structure and the catalysis is switched off. The whole exhibition mechanism proves to be reversible, allowing switching between an activated and deactivated state of the surface, similarly to mechanisms involved in proteins during mechanotransduction.References :1. Vogel, V. & Sheetz, M. Local force and geometry sensing regulate cell functions. Nature Rev. Mol. Cell. Biol. 7, 265-275 (2006).2. Decher, G. Fuzzy nanoassemblies: Toward layered polymeric multicomposites. Science 277, 1232-1237 (1997).3. Garza, J.M., Schaaf, P., Muller, S., Ball, V., Stoltz, J.-F., Voegel, J.-C., Lavalle, Ph., Multicompartment films made of alternate polyelectrolyte multilayers of exponential and linear growth. Langmuir 20, 7298-7302 (2004).4. Mertz, D., Hemmerle, J., Mutterer, J., Ollivier, S., Voegel, J.-C., Schaaf, P., Lavalle, P., Mechanically responding nanovalves based on polyelectrolyte multilayers. Nano Lett 7, 657-662 (2007)
12:15 PM - LL8.3
Nanostructure-Mediated Skeletal Muscle Regeneration from Aligned Multiwall Carbon Nanotube/Polypyrrole Platfrom.
Joselito Razal 1 , Magdalena Kita 1 2 3 , Raquel Robles 4 , Mei Zhang 4 , Anita Quigley 1 2 3 , Michael Higgins 1 , Amy Gelmi 1 , Rob Kapsa 1 2 3 , Ray Baughman 4 , Gordon Wallace 1 Show Abstract
1 Intelligent Polymer Research Institute, University of Wollongong, Wollongong, New South Wales, Australia, 2 Clinical Neurosciences , St. Vincent’s Hospital, Fitzroy, Victoria, Australia, 3 , Bionic Ear Institute, East Melbourne, Victoria, Australia, 4 Alan G. MacDiarmid Nanotech Institute, University of Texas at Dallas, Richardson, Texas 75080 USA , Richardson, Texas, United States
Standard cell transplantation in skeletal muscle degenerative conditions has shown limited therapeutic potential, in part due to immediate cell death, lack of proliferation of surviving donor cells, and the lack of directional support for the differentiating myofibres. Here we investigate the use of a novel nanostructured platform to promote directional muscle differentiation in vitro. The basic platform architecture is fabricated by a two-step process. First by dry-spinning oriented multiwall carbon nanotube (MWNT) sheet onto a substrate, and then followed by electrochemical modification of MWNT surface with polypyrrole (PPy). Atomic force microscopy analysis and contact angle measurements revealed variation in surface properties upon MWNT surface modification with PPy. Immunofluorescent analysis of proliferated myoblasts adhered to both MWNT and PPy-modified MWNT surface. Upon induction of differentiation, the myoblasts preferentially formed multinucleated myotubes on the PPy-modifed MWNT surface. More interestingly, unbranched myotubes formed and aligned parallel to the direction of the MWNT fibers. The present study clearly shows that nanostructured surface provides the essential anisotrophic growth of differentiated and unbranched skeletal myofibers. This hybrid MWNT/PPy platfrom shows great promise as a tool for basic research and applications in muscle engineering and also to other tissues that require a degree of order in their structure (i.e. nerve).
12:30 PM - LL8.4
Anisotropic Particle Assembly in Microdroplets Suspended on Superhydrophobic Substrates.
Vinayak Rastogi 1 , Orlin Velev 1 , Antonio Garcia 2 , Manuel Marquez 2 Show Abstract
1 Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 Harrington Department of Bioengineering, Arizona State University, Tempe, Arizona, United States
We present a new class of anisotropic particles fabricated inside droplet templates on superhydrophobic substrates. Droplets containing aqueous suspension of monodisperse microspheres are dispensed on the solid substrate and retain their initial shape during the evaporation process. The evaporation of the solvent forces the constituent microspheres to organize themselves into close packed structures and allows their organization in layers or more complex patterns within the assembly. Unlike the conventional wet self assembly methods where final structures need to be extracted from the liquid environment, our simple one-step procedure produces ready to use ‘dry’ supraparticles. We produced both shape-anisotropic and composition-anisotropic supraparticles. The shape anisotropy was demonstrated by fabricating "doughnut" assemblies using droplets of both pure silica suspensions and silica mixed with gold nanoparticles. Two major factors determining the final shape of the assemblies are the initial particle concentration and the time when the three phase contact line pins. The composition anisotropy was exhibited by redistribution of the magnetic nanoparticles in droplets containing mixtures of latex and magnetic particle suspensions. The redistribution is dictated by the pattern of magnetic field to which the droplet templates are introduced during drying. We have created mono-patch, bi-patch and tri-patch magnetic supraparticles. The mono-patch magnetic supraparticles in turn self assemble themselves into crystal like arrangements when subjected to non uniform magnetic field. These patchy magnetic particles can find application in targeted drug delivery where the latex matrix can be infused with a drug and the magnetic patch(es) facilitate remote manipulation of the carrier. The multi-patch magnetic supraparticles can also be used in microfluidic mixing, where the suspended particles respond to rotating localized magnetic fields.
12:45 PM - LL8.5
Designing Proteins as Materials for Electronics Applications.
Nurit Ashkenasy 1 3 , Clara Shlizerman 2 , Ravit Cooper 1 , Gonen Ashkenasy 2 Show Abstract
1 Materials Engineering, Ben Gurion University, Beer Sheva Israel, 3 The Ilse Katz Institute for Nanoscale Science and Technology, Ben Gurion University, Beer Sheva Israel, 2 Chemistry, Ben Gurion University, Beer Sheva Israel
In recent years there is a great interest in the integration of biological macromolecules within electronic devices in order to exploit their unique properties. These molecules may serve as active device components, they can be used to guide the bottom-up assembly of hybrid structures, and also to tailor material and device properties. The goal of our research is to study the assembly and electronic properties of synthetic protein molecules designed specifically for such molecular electronics applications. In this talk I will give two different examples that will demonstrate the versatility and flexibility of our approach.In the first example the design is based on the abounded coiled coil motif of natural proteins, which can adopt parallel and anti-parallel conformational states that differ in their internal molecular dipole. The proteins are folded in solution and are self assembled in predefined orientation as monolayers on gold electrodes. Large scale Kelvin probe measurements and Kelvin Force Microscopy (KFM) images are used in order to demonstrate the dependence of the surface dipole, which is induced by the molecular dipoles, on the conformation and orientation of the protein structures, and on their overall charge. We further show how this molecular dipole affects electron transfer through the proteins.In the second example we make use of peptide sequences that were found, using biological libraries, to bind to specific inorganic materials. Peptides that bind to materials such as silicon oxide, Galium Arsenide, Gold, and Carbon nanotubes, are used as templates for patterning these materials at the micro- and nano- metric scale. In the suggested process we first form the desired shape with a pre-designed peptide using soft lithography and high resolution scanning probe microscopy based techniques. In the second step we selectively attach inorganic material to the modified areas on the surface. We will demonstrate the flexibility of this method that can be used with variety of materials both as substrates and patterns.
LL9: Surface Functionalization and Bio-inspiration II
Thursday PM, April 16, 2009
Room 3022 (Moscone West)
2:30 PM - **LL9.1
Nanostructured Active Biomaterials for Tissue Engineering Applications
Nadia Jessel 1 Show Abstract
1 Biomaterials and Tissular engineering, INSERM, Strasbourg France
S. FACCA1, A. DIERICH2, J.-F. STOLTZ3, J.-C. VOEGEL1, N. JESSEL11 Institut National de la Santé et de la Recherche Médicale, Unité 595, 11 rue Humann, 67085 Strasbourg Cedex, France. 2 Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Institut Clinique de la Souris (ICS), CNRS/INSERM/ULP, Collège de France, BP 10142, Strasbourg, France.3 Mécanique et Ingénierie Cellulaire et Tissulaire (LEMTA – UMR CNRS 7563 and IFR 111) Faculté de Médecine F – 54505 Vandoeuvre-Lès-Nancy – France.Contact : email@example.comAbstractIn recent years, considerable effort has been devoted to the design and controlled fabrication of structured materials with functional properties. The layer by layer buildup of polyelectrolyte multilayer films (PEM films) from oppositely charged polyelectrolytes1 offers new opportunities for the preparation of functionalized biomaterial coatings. This technique allows the preparation of supramolecular nano-architectures exhibiting specific properties in terms of control of cell activation and may also play a role in the development of local drug delivery systems. Peptides, proteins or DNA, chemically bound to polyelectrolytes, adsorbed or embedded in PEM films, have been shown to retain their biological activities (2-7). Recently, tissue engineering has merged with stem cell technology with interest to develop new sources of transplantable material for injury or disease treatment. Eminently interesting, are bone and joint injuries disorders because of the low self-regenerating capacity of the matrix secreting cells. We present here for the first time that embedded BMP-2 and TGFβ1 in a multilayered polyelectrolyte film can drive embryonic stem cells to the cartilage or bone differentiation depending on supplementary co-factors. We selected a model system made from layer by layer poly-L-glutamic acid (PGA) and poly-L-lysine succinylated (PLLs) films into which BMP-2 and TGFβ1 have been embedded. Our results demonstrate clearly that we are able to induce osteogenesis in embryonic stem cells mediated by growth factors embedded in a polyelectrolyte multilayer film(8).References1. Decher, G. Fuzzy nanoassemblies: Science 277, 1232-1237 (1997)2. Jessel, N. et al. Adv. Mater. 15, 692-695 (2003)3. Jessel, N. et al. Adv. Funct. Mater. 14, 174-182 (2004)4. Jessel, N. et al. Adv. Funct. Mater. 14, 963-969 (2004)5. Jessel, N. et al. Adv. Mater. 16, 1507-1511 (2004)6. Jessel, N. et al. Adv. Funct. Mater. 15, 648-654 (2005)7. Jessel, N. et al. Proc. Natl. Acad. Sci (USA). 103, 8618-8621 (2006)8. Dierich, A et al. Adv. Mater. 19, 693-697 (2007)
3:00 PM - LL9.2
Ag Nanoplates on GaAs Substrates: A Unique Class of Composite Surfaces for Understanding the Correlation between Surface Roughness and Hydrophobicity.
Yugang Sun 1 Show Abstract
1 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States
GaAs wafers have been decorated with Ag nanoplates through direct galvanic reactions between aqueous AgNO3 solutions and GaAs, resulting in Ag nanoplate/GaAs composite surfaces with various hydrophobocities after the Ag nanoplates are coated with self-assembled monolayers of alkyl thiol molecules. By carefully controlling the reaction conditions, such as growth time and concentration of the AgNO3 solution, size, thickness, and surface roughness of the individual Ag nanoplates can be tuned to produce different topographic structures and roughness of the composite surfaces, which in turn influences hydrophobicity of the surfaces. Water droplets on the as-synthesized composite surfaces have been found to exhibit various levels of hydrophobicity and different wetting states such as the Wenzel wetting state, Cassie impregnating wetting state, and Cassie non-wetting state. The relationship between surface structures and hydrophobic states is also discussed in this presentation.(Use of the Center for Nanoscale Materials at Argonne National Laboratory was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.)
3:15 PM - LL9.3
Hydrophobic Metallic Nanorods coated with Teflon Nanopatches by Glancing Angle Deposition
Wisam Khudhayer 1 , Rajesh Sharma 1 , Tansel Karabacak 1 Show Abstract
1 Applied Science, UALR, Little Rock, Arkansas, United States
AbstractIntroducing a hydrophobic property to vertically aligned hydrophilic metallic nanorods was investigated experimentally and theoretically. First, platinum nanorod arrays were deposited on flat silicon substrates using a sputter glancing angle deposition Technique (GLAD). Then a thin layer of Teflon (nanopatches) was partially deposited on the tips of platinum nanorod at a glancing angle of θ = 85 degree as well as at normal incidence (θ = 0 degree) for different deposition times. Contact angle measurements on Pt/Teflon nano-composite have shown contact angle values as high as 138 degree, indicating a significant increase in the hydrophobicity of originally hydrophilic Pt nanostructures. The enhanced hydrophobicity of Pt-nanorods/Teflon-nanopatch composite may be attributed to the presence of nanostructured Teflon coating which imparted the low surface energy through its enhanced surface roughness. Our nano-composite Pt/Teflon structures were also analyzed using scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDAX). It was found that GLAD technique is capable of depositing ultrathin isolated Teflon nanostructures on selective regions of nanorod arrays due to the shadowing effect during obliquely incident deposition. Finally, we performed surface energy calculations on Pt nanorods, Teflon thin film, and Pt/Teflon composite using two liquids method to confirm the contact angle measurements as well as a theoretical explanation of the Pt/Teflon nanocomposite contact angle utilizing Cassie and Baxter theory of heterogeneous surfaces.
3:30 PM - LL9.4
Simulating the Architectural Dynamics of Trabecular Bone.
John Dunlop 1 , Markus Hartmann 1 , Yves Brechet 2 , Peter Fratzl 1 , Richard Weinkamer 1 Show Abstract
1 Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam Germany, 2 SIMAP, Institut National Polytechnique de Grenoble, Grenoble France
Living trabecular bone is a dynamic cellular material, which changes its architecture in response to altered external loading, aging, disease and drug treatment. This remodeling process allows bone to adapt to its mechanical environment and to repair damage from everyday life. Bone in addition is not only a structural material, but it also acts as a store of calcium for the body. This means that any remodeling which changes the surface architecture of bone will also have an influence on the access to calcium. Remodeling is thought to occur via the mechanosensitive response of the bone forming and bone resorbing cells. This results in bone being preferentially deposited in regions of high load and removed in regions of low load. A knowledge of how bone cells respond to their mechanical environment is important in understanding the process of aging and the progression of bone diseases. Several such “remodeling rules”, that give the amount of bone removed or deposited as a function of the local loading, have been proposed in the literature e.g. . However due to experimental difficulties in measuring local cell response in-vivo these hypotheses have been difficult to confirm. We present a different strategy by evaluating different remodeling rules with a stochastic lattice model for bone remodeling . The evolution of our simulated trabecular bone structures are compared to what evidence is known from m-CT measurements of real bone . Depending on how the remodeling process is specifically controlled by local mechanical stimuli, the simulated bone reacts differently to standard therapeutic methods like physical exercise or suppression of bone resorption. The experimentally observed insensitivity of the bone volume fraction to reductions in bone resorption was observed in the simulations only for a remodeling rule including an activation barrier for the mechanical stimulus above which bone deposition is switched on. This is in disagreement with the commonly used rules which have a so-called “lazy-zone”. Stauber M, Müller R (2006) Age-related changes in trabecular bone microstructures: global and local morphometry. Osteoporosis International 17:616-626 Weinkamer, R., M. A. Hartmann, Y. Bréchet and P. Fratzl (2004). "Stochastic lattice model for bone remodeling and aging." Physical Review Letters 93: 228102. Frost HM (1987) Bone mass and the mechanostat - a proposal. Anatomical Record 219:1-9
4:30 PM - LL9.6
Acrylic-silica Hybrid Nanocomposites used as a Protective Hard Coating.
Raymond Tsiang 1 Show Abstract
1 Chemical Engineering, National Chung Cheng University, Chiayi Taiwan
Organic-inorganic hybrid materials have been extensively investigated recently because of its superior mechanical properties, thermal stability, and optical properties. Of particular interest is the acrylic-silica hybrid which has found great use in the optical membrane application. While acrylics provide easy processibility and optical transparency, silica particles provide hardness and scratch resistance. However, the incompatibility between the acrylics and the silica causes poor dispersion of silica particles in the acrylics matrix and makes a direct blending of acrylics and silica particles impossible. Therefore, significant efforts have been devoted to form chemical bond between the acrylics and silica particles. Apart from the various sol-gel processes involving the in-situ formation of silica with tetraethylorthosilane, one method is to blend the unreacted acrylic monomer with the silica particles which have been modified with compatible organic species. Under UV irradiation, acrylic monomers and organic species copolymerize and crosslink to form a highly transparent hybrid composite material. Research data on modification of silica particles are abundant in literature[2-10]. Herein, we have prepared the acrylic-functionalized silica nanoparticles and copolymerized the modified silica nanoparticles with a dendritic acrylic oligomer (DAO) via UV-curing to make an acrylic-silica hybrid nanocomposite. The use of the dendritic oligomer enhances the cure rate and the choice of nano-size for silica particles provides transparency to the hybrid material. This hybrid nanocomposite hss excellent properties for use as a protective hard coating.