Paul Millett, University of Arkansas
Esther Amstad, Ecole Polytechnique Federale de Lausanne
Paul Clegg, University of Edinburgh
Daeyeon Lee, University of Pennsylvania
BM02.01: Colloids I
Monday AM, November 27, 2017
Sheraton, 2nd Floor, Back Bay A
8:30 AM - *BM02.01.01
Synthesis, Assembly and Applications of Nanoemulsions
Patrick Doyle 1 Show Abstract
1 , MIT, Cambridge, Massachusetts, United States
Nanoemulsions are liquid-liquid dispersions with droplet sizes of order 100nm. There is a burgeoning interest in nanoemulsions for both fundamental studies of colloidal self-assembly, and applications ranging from cosmetics to enhanced oil recovery to pharmaceuticals. Advances in our understanding of fundamental concepts in nanoemulsion synthesis and assembly are enabling the design of advanced nanoemulsion-based materials. In this talk I will discuss advances we have made in rational synthesis of nanoemulsions using both low and high energy approaches, hierarchical assembly of nanoemulsions combining both bottom-up and top-down methods, and application of nanoemulsions in a process intensification approach to formulating drug products with enhanced performance.
9:00 AM - *BM02.01.02
Strategies for Making Smart Foams, Emulsions and Multiphase Gels Stabilized by Functional Particles
Orlin Velev 1 Show Abstract
1 , North Carolina State University, Raleigh, North Carolina, United States
We will discuss strategies for making novel responsive classes of soft matter by using multiphasic fluids and particle-controlled interfacial effects. One such class of materials can be formed when light- or field-responsive particles are embedded into foams, emulsions and colloidal gels. In the first part of the talk, we will present the design and characterization of a few types of very stable, yet stimuli-responsive, Pickering foams. These foams are stabilized by rod-like polymer particles or ones made from hydrophobically modified cellulose. By the addition of carbonyl iron particles into the matrix, these Pickering systems can be made photo- as well as thermally sensitive, resulting in novel photo-thermo-magneto responsive foams. In the second part of the talk, we will describe a new smart multiphasic gel system containing ultra-flexible chains assembled from magnetically responsive nanoparticles bound by liquid lipid bridges. The initial application of an external magnetic field aligns the superparamagnetic nanoparticles into chains, where they become bound by the soft attractive potential induced by the surface-condensed lipid. The liquid bridges allow for particle rolling and sliding. The nanoparticles binding through soft, "snappable" liquid bridging provides a facile means of creating self-repairing gel networks. The control of the capillary interactions made possible the making of precise cluster assemblies from metallo-dielectric Janus particles, as well as few magnetically responsive gels. Finally, these flexible responsive multiphasic structures can be used in novel colloidal inks for 3D printing. These capillary inks are made of silicone beads, which are bound by liquid silicone precursor bridges, and dispersed in water. The softness and flexibility of the printed delicate PDMS lattices allowed making "Pickering emulsions" with droplets protected by 3D printed cocoons wrapped around them.
9:30 AM - BM02.01.03
Hyperuniformity of Bidisperse Droplet Jammed Assemblies
Joshua Ricouvier 1 , Pavel Yazhgur 1 , Romain Pierrat 1 , Rémi Carminati 1 , Patrick Tabeling 1 Show Abstract
1 , ESPCI Paris, Paris France
We explore the possibilities of fabricating photonic materials using the self-organisation of soft matter at the optical wave length scale. Hyperuniform materials, being disordered systems with suppressed long-scale fluctuations have been demonstrated to exhibit interesting photonic properties such as transparency for optically dense materials or photonic bandgap. In our project we study a jammed packing of bidisperse oil droplets in water. They are produced in a PDMS microfluidic chip and directly assembled in a microfluidic channel. By varying the fluid pressures, we manage to sharply control the droplet production (size ratio, number ratio) and thereby govern the structural properties of the obtained jammed material. We monitor various defects that prevent the system to be hyperuniform and investigate their influence on the structure factor. Our results show that at appropriate experimental conditions droplets self-organize in disordered hyperuniform patterns. Our electromagnetic simulations also show that the obtained material can be transparent while staying optically dense. As far as we know, the proposed material is one of the first examples of experimentally made hyperuniform materials. We hope that our studies will help to establish a new way of disordered photonic material production.
9:45 AM - BM02.01.04
Particles, Droplets and Bubbles Together—Particle Adsorption and Fluid-Fluid Wetting in Colloidal Four-Phase Systems and Ensuing Opportunities for New Materials and Separation Processes
Sven Behrens 1 , Carson Meredith 1 Show Abstract
1 , Georgia Institute of Technology, Atlanta, Georgia, United States
Classical definitions of a colloidal dispersion invoke a two-phase systems with a continuous phase (medium), and a dispersed phase consisting alternatively of solid particles, liquid droplets, or gas bubbles. More complex multi-phase systems with distinctly colloidal character are familiar as well and have drawn increasing attention as platforms for materials engineering: particle-stabilized emulsions or foams, and bijels (bicontinuous interfacially jammed emulsion gels) are examples of colloidal three-phase systems that can even be prepared in simple batch processes; and microfluidic techniques have enabled the production of “designer emulsions” with complex and highly controllable multi-phase structure.
Nonetheless, systems containing immiscible liquids as well as a gas phase and solid particles are rarely studied. Messy as the concept of such “wild colloidal mixtures” may at first appear, the selective adsorption of particles to the various types of fluid-fluid interfaces in such mixtures can be leveraged to direct robust multi-scale assembly upon homogenization. It also provides a powerful tool for tuning fluid-fluid wetting and can be exploited for novel separations of dispersed or emulsified contaminants from liquid media. To illustrate these benefits we briefly discuss the recently discovered “capillary foams”, in which gas bubbles in water are stabilized by an intricate network of oil-bridged particles. We further demonstrate the particle-mediated reconfiguration of bubble-droplet wetting morphologies, and the removal of particles and droplets from aqueous media with the help of bubble/oil/particle complexes.
BM02.02: Microfluidics I
Monday AM, November 27, 2017
Sheraton, 2nd Floor, Back Bay A
10:30 AM - *BM02.02.01
Drop Microfluidics—A Versatile and Promising Approach for Fabricating Functional Granular Materials
Liang-Yin Chu 1 , Martin Haase 1 Show Abstract
1 , Sichuan University, Chengdu China
Abstract: Functional granular materials with typical sizes of 1~1000 µm have received considerable attention for many applications. Generally, the overall functions of these microparticles strongly rely on both of their structures and the properties of their component materials. Thus, the combination of unique structures with functional materials provides an important route for developing advanced functional granular materials. Utilization of emulsions as templates allows producing versatile microparticles, with their size, shape and structure largely depends on those of the emulsions. Emulsion-template synthesis of microparticles allows precise control over their size, shape, composition and structure by tuning those of emulsions via specific emulsification techniques. With excellent control over emulsion drops, microfluidic technique provides a powerful platform for reproducible and scalable production of granular materials with unprecedented control over their structures and compositions. This provides vast opportunities for producing granular materials with the structure-property combination strategy for achieving elaborately designed functions. The controllable architectures of the emulsions and their tunable chemical composition for each separate phase allow for flexible combination of the structure characteristics and material properties for producing microparticles with elaborately tailored functions. In this presentation, we highlight the recent efforts for microfluidic fabrication of granular materials with well-designed functions, along with the development of microfluidic techniques for producing the versatile emulsion templates.1-4 We envision that the versatility of microfluidics for microparticle synthesis could open new frontiers and provide promising and exciting opportunities for fabricating brand-new functional microparticles with broad implications for myriad fields.
1. Chu L.Y., Wang W., Microfluidics for Advanced Functional Polymeric Materials. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 2017.
2. W. Wang, M.J. Zhang and L.Y. Chu, Acc. Chem. Res., 2014, 47, 373.
3. W. Wang, M.J. Zhang, R. Xie, X.J. Ju, C. Yang, C.L. Mou, D.A. Weitz and L.Y. Chu, Angew. Chem. Int. Ed., 2013, 52, 8084.
4. W. Wang, R. Xie, X.J. Ju, T. Luo, L. Liu, D.A. Weitz and L.Y. Chu, Lab Chip, 2011, 11, 1587.
11:00 AM - *BM02.02.02
Order and Chaos—Collective Behavior of Crowded Drops in Microfluidic Systems
Sindy Tang 1 Show Abstract
1 , Stanford University, Stanford, California, United States
Droplet microfluidics, in which micro-droplets serve as individual reactors, has enabled a range of high-throughput biochemical processes. Although the physics of single drops has been studied extensively, the flow of crowded drops or concentrated emulsions—where droplet volume fraction exceeds ~80%—is relatively unexplored in microfluidics. Ability to leverage concentrated emulsions is critical for further increasing the throughput of droplet applications. Prior work on concentrated emulsions focused on their bulk rheological properties. The behavior of individual drops within the emulsion is not well understood, but is important as each droplet carries a different reaction.
This talk examines the collective behavior of drops in a concentrated emulsion by tracking the dynamics and the fate of individual drops within the emulsion. At the fast flow limit, we show that droplet breakup within the emulsion is stochastic. This contrasts the deterministic breakup in classical single-drop studies. We further demonstrate that the breakup probability is described by dimensionless numbers including the capillary number and confinement factor, and the stochasticity originates from the time-varying packing configuration of the drops. To mitigate breakup, we design novel amphiphilic nanoparticles, and show they are more effective than surfactant molecules as droplet stabilizers.
At the slow flow limit, we observe an unexpected order, where the velocity of individual drops in the emulsion exhibits spatiotemporal periodicity. Such periodicity is surprising from both fluid and solid mechanics point of view. We show the phenomenon can be explained by treating the emulsion as a soft crystal undergoing plasticity, in a nanoscale system comprising thousands of atoms as modeled by droplets. Our results represent a new type of collective order not described before, and have practical use in on-chip droplet manipulation. From the solid mechanics perspective, the phenomenon directly contrasts the stochasticity of dislocations in microscopic crystals, and suggests a new approach to control the mechanical forming of nanocrystals.
*Chaos stands for Crowded droplet breakup HydrodynAmics not Ordered but Stochastic
11:30 AM - BM02.02.03
Flow-Induced Chemistry within Inkjet Droplets Providing Tunable Materials Properties
Niamh Willis-Fox 2 , Etienne Rognin 2 , Talal Aljohani 1 , Ronan Daly 2 Show Abstract
2 Department of Engineering, University of Cambridge, Cambridge United Kingdom, 1 , King Abdulaziz City for Science and Technology, Riyadh Saudi Arabia
Molecular-scale interactions in multiphase fluids are of great interest due to their use in applications such as the directed self-assembly of block copolymers for use in electronic devices1a or the encapsulation of self-healing materials within a polymer network.1b Often these materials are deposited on surfaces both for studying but also to integrate into devices. Solution phase processing is used, such as inkjet printing, spray coating or microfluidics which are particularly attractive when considering the possibility of device scale-up and digital manufacturing. However, functional materials can be degraded and damaged by forces imparted during these fluid flows. This is highlighted by the degradation and reduction in polymer molecular weight observed during inkjet printing attributed to polymer elongation due to shear forces.2
Recently it has been shown that these forces need not be destructive but may in fact be used to create programmable catalytic material,3a drive crosslinking reactions3b or provide access to new reaction pathways inaccessible by other driving forces such as the use of light or heat.3c Here we report on the particularly exciting application of these findings to the field of digital printing where the prospect of using normally destructive forces to create and modulate properties during processing is extremely intriguing. We examine the formation of functional droplets via drop-on-demand inkjet printing using in the first instance, a model system of polystyrene (PS) and poly(methyl methacrylate) (PMMA) of varying molecular weight with the radical trap 2,2-diphenyl-1-picrylhydrazyl (DPPH). Under flow polymer chain scission leads to homolytic C-C bond scission leading to the neutralisation of DPPH causing it to change from its native purple to a pale yellow. The shear rate, and by extension droplet size, is controlled by the nozzle dimensions and fluid flow parameters, allowing regulation of the polymer chain scission and colour change of the system through careful nozzle selection. The potential is shown to control the chemistry and function of each drop through careful process control and we discuss the future of this research in potentially driving cross-linking and localised chemical synthesis.
1. a) Y. Zhang and K. Hashimoto, J. Am. Chem. Soc., 2008, 130, 7812. b) M. m. Caruso and J. S. Moore et al., Chem. Rev., 2009, 109, 5755.
2. K. A-Alamry, S. G. Yeates et al., Macromol. Rapid Commun., 2011, 32, 316. J. S. R. Wheeler, S. G. Yeates et al., Polym. Degrad. Stab., 2016, 128, 1.
3. a) A. Piermattei, S. Karthikeyan and R. P. Sijbesma, Nat. Chem., 2009, 1, 133. b) Z. S. Kean, Z. Niu, G. B. Hewage, A. L. Rheingold and S. L. Craig, J. Am. Chem. Soc., 2013, 135, 13598. c) Hickenboth, C. R. et al., Nature, 2007, 446, 423.
11:45 AM - BM02.02.04
High-Precision Modular Microfluidics for Reconfigurable Droplet Production Systems
Crystal Owens 1 , A. John Hart 1 Show Abstract
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
High-precision rapid prototyping methods are instrumental to the realization of microfluidic devices to produce, measure, and manipulate droplets. Experiments often give more insight into performance than modeling, due to the complex interfacial effects involved. Herein, we present a reconfigurable and modular microfluidic platform based on modified polycarbonate LEGO bricks and demonstrate its use for the production and manipulation of water-in-oil droplets. True to their reputation, LEGO bricks have tight geometric tolerances - below ~50µm (0.1% COV) - and elastically averaging mechanical features that will align bricks to a standard baseplate with a repeatability <3µm.
To create our systems, we machined channels into the sides of as-received LEGO bricks using a micromill (Roland SRM-20); channel dimensions ranged from 150-500µm in width and 50-500µm in depth. The assembled bricks were reversibly sealed in series to form modules using embedded O-rings. By this approach, we constructed a library of modules, each performing one operation within a series, including droplet generation, advective mixing, optical sensing, sorting by density, and tubing connection. Various microfluidic systems then were built by placing modules in series on a LEGO baseplate. Using an assembly of LEGO-fluidic modules, we demonstrated the generation and in-situ optical measurement of single-component emulsions. In T-junction cross flow, we produced up to 9000 drops/min with a COV ~3%. Droplet size distribution was controlled by total flow rate and were consistent after reconfiguring the system.
Future possibilities for the system include the fabrication of complex 3D networks, fast prototyping of multi-step reactions, and system control including measurement and feedback.
BM02.03: Particles at Fluid Interfaces
Monday PM, November 27, 2017
Sheraton, 2nd Floor, Back Bay A
1:30 PM - *BM02.03.01
Bijels—A Unique Platform for Materials Synthesis, from Energy Systems to Biomaterials
Ali Mohraz 1 Show Abstract
1 , University of California, Irvine, California, United States
Bicontinuous interfacially jammed emulsion gels (bijels) are a new class of soft materials that spontaneously form when spinodal decomposition in a binary mixture of partially miscible fluids is kinetically arrested by colloidal jamming at the fluid interfaces. The result is a mechanically stable multiphase mixture comprised of independently percolating, interpenetrating fluid domains with uniform domain size throughout the mixture, separated by a jammed monolayer of colloidal particles that predominantly exhibit a negative local Gaussian curvature. This unique morphology provides an excellent template for the synthesis of composite materials with tunable microstructure and co-continuous arrangement of their constituents, which result in optimum transport and mechanical properties with applications ranging from electrochemical energy storage to tissue engineering. In this talk I will present the materials synthesis routes that we have pioneered to convert bijels into functional microstructured composites, and discuss the utility of our technology in energy systems and biomedical applications. Examples from two completely different applications will demonstrate how the unique morphology of bijel-based materials enables the synthesis of battery electrodes with tunable electrochemical function over a wide range and simultaneous delivery of high energy and power densities, and also translates to foreign body response mediation, host tissue and vascular integration, and robust cell delivery vehicles in biomedical technologies. Finally, I will discuss our ongoing efforts to expand the library, chemistry, and utility of bijel-based materials in other related fields.
2:00 PM - BM02.03.02
Bijels Prepared by Direct Mixing at Fixed Temperature
Paul Clegg 1 , Katherine Rumble 1 , Dongyu Cai 1 , Tao Li 1 , Joe Tavacoli 1 Show Abstract
1 , University of Edinburgh, Edinburgh United Kingdom
Historically bicontinuous interfacially jammed emulsion gels (bijels) have been prepared by making use of the phase-separation behaviour of partially miscible liquids.  This greatly constrains the choice of starting ingredients. We have recently found that, by combining interfacial nanoparticles and molecular surfactants together with immiscible liquids of high viscosity, we can avoid the need for a phase separation transition. This work builds on a previous suggestion,  that the wetting properties of nanoparticles will self-optimize in the presence of molecular surfactants and then can be used to form non-equilibrium structures. We develop this idea by tuning the sample composition and by demonstrating a multi-step mixing protocol to achieve a tortuous arrangement of liquid domains. These bijels are prepared from common ingredients which are widely used in industry: glycerol, silicone oil, silica nanoparticles together with cetyltrimethylammonium bromide surfactant. We show that the nanoparticle location changes from one of the phases to the interface during multi-step mixing. The changes in both the microscopic and macroscopic sample configuration after a waiting time of months have been assessed. In order for the structure to have long-term stability we find that the densities of the two phases must be similar which we achieved by filling one of the phases with nanoparticle-stabilized droplets of the other. This work paves the way to the production of bijels using fully immiscible liquids and hence their exploitation in many application areas.
 e.g. Rumble, K. A., Thijssen, J., Schofield, A., and Clegg, P.S. (2016). Compressing a spinodal surface at fixed area: the bijel in a centrifuge. Soft Matter, 12, 4375–4383.
 Cui, M., Emrick, T., and Russell, T. P. (2013). Stabilizing liquid drops in nonequilibrium shapes by the interfacial jamming of nanoparticles. Science (New York, N.Y.), 342(6157), 460–3.
2:15 PM - BM02.03.03
Multifunctional Nanocomposite Membranes and Biphasic Liquid-Liquid Microreactors Based on Bijels
Martin Haase 1 Show Abstract
1 , Rowan University, Glassboro, New Jersey, United States
Industrial separation processes, such as distillation, amount to 10 to 15 percent of the world’s energy consumption. Energy efficient methods to purify chemicals are urgently needed to lower carbon dioxide emissions and cut energy costs. Our research investigates bicontinuous interfacially jammed emulsion gels (bijels) for reactive separations. We have recently introduced Solvent Transfer Induced Phase Separation (STRIPS) for the formation of nanoparticle stabilized liquid fibers composed of bicontinuous oil water scaffolds (STRIPS bijels).[2, 3] Based on these we develop a facile single-step method of generating nanoparticle decorated polymer membranes. Our approach advances the field of nanocomposite membranes by allowing for the introduction of diverse building blocks for membrane formation with potential applications in water treatment, in industrial separations, and as catalytic membrane reactors. Furthermore, we advance STRIPS-bijels as biphasic liquid microreactors for interfacial catalysis. Here, the bicontinuous oil/water channel network facilitates intimate contact between immiscible reactants that can undergo phase transfer reactions, catalyzed by the interfacially jammed layer of nanoparticles. This novel approach gives rise to continuously operated flow reactors, enabling simultaneous reactions and separations in a single unit.
 Herzig, E., White, K., Schofield, A., Poon, W. & Clegg, P. Bicontinuous emulsions stabilized solely by colloidal particles. Nature materials 6, 966-971 (2007).
 Haase, M. F., Stebe, K. J. & Lee, D. Continuous Fabrication of Hierarchical and Asymmetric Bijel Microparticles, Fibers, and Membranes by Solvent Transfer Induced Phase Separation (STRIPS). Advanced Materials 27, 7065-7071 (2015).
 Haase, M. F., Sharifi-Mood, N., Lee, D. & Stebe, K. J. In Situ Mechanical Testing of Nanostructured Bijel Fibers. ACS Nano 10, 6338-6344 (2016).
 Haase, M.F., Jeon, H., Hough, N., Kim, J.H., Stebe, K.J., Lee, D., Multifunctional Nanocomposite Hollow Fiber Membranes by Solvent Transfer Induced Phase Separation. Nature Communications, In Press (2017)
2:30 PM - BM02.03.04
Tuning Thin-Film Bijel Morphologies Using External Electric Fields
Joseph Carmack 1 , Paul Millett 1 , Mukerrem Cakmak 2 Show Abstract
1 , University of Arkansas, Fayetteville, Arkansas, United States, 2 , Purdue University, West Lafayette, Indiana, United States
Creating bijels in thin-film geometries provides an efficient and scalable method for integrating nanoparticles and their unique properties into membranes thereby increasing membrane functionality. In this work, we explore mechanisms for tuning bijel membrane morphology by manipulating particle loading, thickness, and employing electric-field alignment techniques. These parameters and their mechanisms are studied using computer simulations based on a hybrid Cahn-Hilliard and Brownian Dynamics computational model which couples the diffusion driven phase separtion of an immiscible binary liquid mixture to the Brownian motion of dispersed particles in electric fields. The bijel formation simulations show the relationship between electric-field induced dipole-dipole particle interactions and particle attachement to liquid-liquid interfaces. Thin-film Bijel morphologies tuned by electric-fields are a novel way to create through channel membranes where channels are lined with nanoparticles. We expect these simulations to facilitate the design of new bijel materials with superior functionality for energy, environmental, and other industry applications.
2:45 PM - BM02.03.05
Understanding the Effect of Particle Charge, Solution Viscosity and Mass Fraction on Bicontinuous Interfacially Jammed Emulsion Gels
Rachel Malone 1 , Geena Smith 1 , Aseem Pandey 1 , Milana Trifkovic 1 Show Abstract
1 Chemical and Petroleum Engineering, University of Calgary, Calgary, Alberta, Canada
Bicontinuous interfacially jammed emulsion gels (bijels) are formed during the spinodal decomposition of two liquid phases. Colloidal particles with a 90 degree three-phase contact angle are used to stabilize the interface between two liquids as they separate, and tuning particles can be a non-trivial task when the interactions between the liquids is complex. The original water-2,6-lutidine system traditionally uses Stöber silica that has been optimally washed and dried for neutral wetting, although recent works have also successfully used graphene oxide sheets to stabilize the structures. Understanding the design space surrounding particle tuning, morphology, and the structural properties of bijels will allow us to streamline the development of new bijel systems for a wide range of applications. In this study, we aim to understand the effect of the particles’ mass fraction, charge, and solution viscosity on bijel structure and consequent mechanical properties. In particular, we take advantage of Coulombic forces to tune particle location in the system. It is known that the interface between aqueous and most oil phases has a negative charge due to the orientation of water molecules and hydroxide ions near the interface. Here, we utilize commercially available cationic silica nanoparticles (15-20 nm), to successfully create a water-2,6-lutidine bijel. Prior to heating, the basic pH of the critical water-lutidine system causes the cationic silica to form a silica gel, and by tuning the particle concentration, the viscosity of the system can be varied and thus the kinetics of the bijel's formation can be tuned. We utilize confocal-rheology (laser scanning confocal microscopy combined with rheology) to capture and quantify the 4D (3 dimensions plus time) microstructure under the influence of well-defined shear. This method allows us to make direct connections between the evolving microstructure and the macroscopic properties of the developed bijels. The 2,6-lutidine phase was tagged with a fluorescent dye, and the particles are imaged with reflectance to visualize these systems in 3D and during rheological testing and formation. We generate phase domains that are in the sub-ten micron range. The use of cationic particles is a new method for bijel particle tuning, and the commercial availability of these particles and their long term stability in critical solutions of water and lutidine offers a significant advantage for further processing of the bijels.
BM02.04: Colloids II
Monday PM, November 27, 2017
Sheraton, 2nd Floor, Back Bay A
3:30 PM - *BM02.04.01
All Water Emulsion-Bodies (AWE-somes) with Permeable Shells and Selective Compartments
Sarah Hann 1 , Daeyeon Lee 1 , Kathleen Stebe 1 Show Abstract
1 , Univ of Pennsylvania, Philadelphia, Pennsylvania, United States
Compartmentalization is a key structural feature of living cells enabling spatial and temporal control of reactions and signaling pathways. Creating cell-mimetic, bio-friendly host structures that have multiple compartments is challenging using conventional techniques, due to the presence of a potentially deleterious oil phase. In this work, we present a new route to creating encapsulated double emulsions within an all-water framework. The aqueous two phase system of poly(ethylene glycol) (PEG) and dextran is used to template complementary polycation PEs and anionic nanoparticles (NPs), which are included in the dispersed dextran-phase and continuous PEG-phase, respectively. The NPs attach to the interface during complexation, the membrane network is still porous, and PEG from the continuous phase is driven into the dextran droplet phase to reduce the osmotic pressure difference between the two phases. This process continues until the membrane permeability is restricted and no more PEG is included; we name the final structures all-water emulsion bodies (AWE-somes). The amount of included PEG is inversely proportional to NP concentration; the higher the NP concentration, the more quickly the NP-PE membrane permeability is reduced. We also demonstrate control over membrane rigidity by modulating anionic NP content by introducing an additional anionic PE. We demonstrate membrane permeability, partitioning of small molecules within the lumen compartments, and simple reaction within the inner PEG phase, suggesting these AWE-some vehicles are indeed able to support compartmentalization with biologically relevant materials.
4:00 PM - *BM02.04.02
Effect of Electric Field on the Bijel Morphology on PS/PMMA with Si02 and BaTiO3Nanoparticles
Yuchen Guo 1 , Sungho Yook 1 , Mukerrem Cakmak 1 Show Abstract
1 Materials and Mechanical Engineering Department, Purdue University, West Lafayette, Indiana, United States
Polymer blend morphologies trapped by nanoparticles and the effects of an AC electric field on the blend morphologies were investigatedd. Immiscible polymer blends of polystyrene (PS) and Poly(methyl methacrylate) (PMMA) were stabilized by nanoparticles grafted with PS-r-PMMA brushes during solvent-induced phase separation. The monolayer nanoparticles were found at the interface between PS and PMMA domains. The final morphologies of polymer blends were significantly influenced by the rate of solvent evaporation, polymer blend ratio, nanoparticle size and nanoparticle loadins. Notably, the morphology could be controlled by the solvent evaporation rate from PS/PMMA bicontinuous morphology to PMMA droplet domains in a PS matrix morphology. AC electric field deformed the PMMA droplets domains into column shapes during the solution drying. SiO2 nanoparticles (dielectric constant : ~4) were covered the surface of the aligned PMMA columns when an out-of-plane electric field was applied. BaTiO3 nanoparticles (dielectric constant : ~2,000) formed aligned chain-like structures at the interface of PS/PMMA domains by the application of electric field.
4:30 PM - BM02.04.03
Pickering Nanoemulsions via Self-Assembly of Particles on Condensing Droplets
Dong Jin Kang 1 , Hassan Bararnia 1 , Sushant Anand 1 Show Abstract
1 , University of Illinois at Chicago, Chicago, Illinois, United States
Absorption behavior of particles between liquid-liquid interfaces has been widely investigated to understand the complex mechanisms such as the interface adsorption and the wetting behavior of particles in water-in-oil (w/o) or oil-in-water (o/w) emulsions. Here, we suggest a novel strategy preparing w/o nanoemulsions using water vapor condensation on an immiscible liquid in presence of nanoparticles. The nanoparticles are irreversibly adsorbed at the oil-water interface and limit the growth of droplets while at the same time also stabilizing the droplets against coalescence. The nanoparticle absorption is induced simultaneously with water condensation process that is governed by positive and negative spreading coefficient that can provide the nanoscale water droplets in the oil medium. The size of droplets and number of droplets are significantly influenced by nanoparticle size and concentration. Furthermore, the formation of water droplets in the oils shows a unique feature depending on condensation time. Emulsification by vapor condensation in presence of nanoparticles is shown to be a simple, scalable and highly energy-efficient technique for making nanodispersions.
4:45 PM - BM02.04.04
Particle-Loaded Porous Foams Prepared via High Internal Phase Emulsion—Applications in Military Medicine and Force-Protection
Christopher McGann 1 , Benjamin Streifel 1 , Robert Balow 1 , Jorge Miranda Zayas 1 , Grant Daniels 1 , Jeffrey Lundin 1 , Pehr Pehrsson 1 , James Wynne 1 Show Abstract
1 , Naval Research Laboratory, Washington, District of Columbia, United States
The preparation of porous polymers via high internal phase emulsion templating (polyHIPEs) has proven to be a highly robust method for the development of materials with well-defined porosity and high specific surface areas; polyHIPEs have seen application in separation science, catalysis, and as scaffolds in tissue engineering. The facile incorporation and display of functional particles is important advantage of utilizing the HIPE approach. Here, porous polymeric materials produced via HIPE templating for applications as wound-contact materials and as self-decontaminating foams for force protection are discussed. Hydrophilic polyHIPEs composed of cross-linked poly(ethylene glycol)s and polyacrylates exhibited characteristic HIPE microstructure via SEM even when loaded with hemostatic agents such as kaolin particles or chitosan microspheres. These porous foams demonstrate significant promise as bandage materials with their great capacity for buffer absorption, low cytotoxicity, notable hemostatic activity, and capability of delivering active antibiotics. Additionally, the development of polyHIPE foams synthesized via ring-opening metathesis polymerization for oleophilic self-contaminating sponges due to the high porosity and flexibility of particle incorporation is presented.
BM02.05: Poster Session
Monday PM, November 27, 2017
Hynes, Level 1, Hall B
8:00 PM - BM02.05.01
Biaxially Shaping Droplet by Initiating Localized Elastic Pattern Bifurcation
Ding Wang 1 , Glen McHale 1 , Gary Wells 1 , Ciro Semprebon 1 , Halim Kusumaatmaja 2 , David Wood 3 , Bin Xu 1 Show Abstract
1 , Northumbria University at Newcastle, Newcastle upon Tyne United Kingdom, 2 Department of Physics, Durham University, Durham United Kingdom, 3 Department of Engineering, Durham University, Durham United Kingdom
Wetting phenomena with the ability to reshape liquids within a capillary length have many technological applications including coating, adhesion, self-cleaning surfaces, printing, and nano-microfluidics. Sinusoidal wrinkle and crease patterns on an elastic substrate can create an ordered roughness with the potential to control droplet motion. Non-uniform distributions of surface energy can cause anisotropic wetting and droplet deformation, while asymmetric chemical or physical patterns on a material surface can cause directional wettability. On a micro-wrinkled surface, the geometrical aspect ratio strongly influences the shape of a droplet. On an elastic wrinkled groove surface, as the certain compressive strain is approached, a droplet can start imbibing into the grooves leading to an eventual filling of entire grooves. To achieve highly controllable instabilities and a bi-axial switching droplet shape, we created a patterned elastic surface able to initialize localized surface instabilities and induce reversible surface morphology changes. At equilibrium, our topographic surface consists of a set of circular voids distribute din an equilibrium manner. By using plasma treatment and mechanical stimuli, we investigated the evolution of the nano/micro-structure on surface, which forms under mechanical stimuli and redistributes the surface energy. A droplet placed on our surface is pinned by the topographic features and deforms as the circular shapes elongate to elliptical shapes. The static, advancing and receding contact angles were measured before and after plasma treatment, showing the enhancement of the surface wettability due to changes in the surface chemistry, morphology and roughness. This finding opens a window to create the robust wetting state surface with potential applications in microfluidics, bio-engineering and soft robots.
8:00 PM - BM02.05.02
Integration of Functional Inorganic/Organic Hybrid Materials via Microfluidic Technology—From Small to Large
Su Chen 1 Show Abstract
1 , Nanjing Tech University, Nanjing China
Microfluidic technology provides a powerful platform in fundamental science and applied researches such as manipulation of nanoparticles, cell screening, and synthesis of drugs on account of the special properties of fluids in microscale. In this paper, we demonstrate the microfluidic technology to explore the integration of inorganic/organic hybrid materials by using polymer, quantum dots and monodispersed polystyrene, silica microspheres as units. By means of physical and chemistry interaction among the units, the structural design, surface modification and compound interconnection are investigated to realize the inorganic-organic assembly. In practice, we successfully integrate nanocrystals into magnetic response colloidal photonic crystals, which reveal double optical signals containing fluorescent and reflected light and are applied in optical display devices, environmental sensor and molecular-analogue blocks. In addition, we put forward a new microfluidic spinning technique for the controllable preparation of multidimensional nanocrystal/polymer composite fibers which may have great potential applications in LED optoelectrical devices, microreactor, encoding, etc.
8:00 PM - BM02.05.03
Core-Shell Photonic Microcapsules Containing Cholesteric Liquid Crystals with Opposite Handedness
Sang Seok Lee 1 , Yun Ho Kim 2 , Shin-Hyun Kim 1 Show Abstract
1 , Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of), 2 , Korea Research Institute of Chemical Technology, Deajeon Korea (the Republic of)
Cholesteric liquid crystals (CLCs) are nematic liquid crystals whose director is rotated along the perpendicular axis by chiral dopants. The helical rotation of the directors makes refractive index periodically modulated along the helical axis, thereby providing photonic bandgap property. The CLCs selectively reflect circularly-polarized light with the same handedness to their helical structure at the photonic stopband. When the stopband is located in the visible range, structural colors are developed. However, the colors originated from a single stopband are highly limited. To provide a variety of structural colors, distinct CLCs with different helical pitches should be integrated into single granules; multiple stopbands are important not only for the coloration but for various photonic applications including lasing and optical barcoding. In this work, we design core-shell microcapsules containing left- and right-handed CLCs in their own core and shell by employing oil-in-water-in-oil-in-water (O/W/O/W) triple-emulsion drops as a template. The triple-emulsion drops are prepared with a capillary microfluidic device in a highly controlled fashion to have a right-handed CLC core, thin aqueous layer, and left-handed CLC shell. The aqueous middle layer between the CLC core and CLC shell prevents the mixing between the two CLCs with opposite handedness. At the same time, poly(vinyl alcohol) dissolved in the aqueous layer induce a planar orientation of liquid crystal molecules. The triple-emulsion drops are stabilized by polymerizing reactive mesogen in the CLC shell, which yields stable core-shell microcapsules. As the CLCs in the core and shell reflect their own structural colors, the core-shell microcapsules display a mixed structural color under illumination with unpolarized white-light. Under illumination of circularly-polarized light, the structural color can be selected from either the core or shell according to the handedness of the light. As the wavelengths of the photonic stopbands for the core and shell are independently controlled during the microfluidic encapsulation, unlimited combinations of two stopbands are selected to display various mixed structural colors, which are otherwise difficult to develop. We believe that the core-shell microcapsules with dual photonic stopbands can be used as novel photonic inks for anti-counterfeiting applications.
8:00 PM - BM02.05.04
Simultaneous Stress and Weight Measurements for Particulate Films Made from Capillary Suspensions
Steffen Fischer 1 , Erin Koos 1 Show Abstract
1 , KU Leuven, Leuven Belgium
Cracking and particle mobility are a significant problem in the drying of films from hard sphere suspensions. One pathway to avoid these problems is by using capillary suspensions . In the pendular state, the preferentially wetting secondary fluid forms capillary bridges between the particles. The capillary force from such bridges induces the formation of a sample-spanning particle network [2, 3], which limits the direction of particle motion during film drying, and the capillary force also counters the capillary force within pores generated by evaporation. Crack-free films can be produced at thicknesses much greater than the critical cracking thickness for a suspension without capillary interactions, and even persists after sintering. This method is applicable to a broad range of materials and can be easily implemented using well-established industrial methods.
A simultaneous weight and stress measurement of a drying film allows direct relation of dynamic changes in stress with the corresponding drying rate. The overall stress of a film can be measured using the cantilever deflection method  as the film dries in a temperature and humidity controlled chamber. Capillary suspensions, with a higher shear modulus, can lower the overall stress in the film while drying. Although no visible cracks occur in any of the films, a characteristic stress increase followed by relaxation occurs. Capillary suspensions change the shape of the stress profile from a slow stress rise followed by a rapid, uniform relaxation towards a more rapid rise followed by a two-stage relaxation, where the stress reduction in the second stage is significantly slower. Moreover, the peak stress occurs at a higher film loading compared to the pure suspension, shifting from around to X = 16 % to 26 %. An increase in relative humidity has little effect on the drying behavior for each sample composition.
8:00 PM - BM02.05.05
Decoupled Hierarchical Structures for Suppression of Leidenfrost Phenomenon
Nazanin Farokhnia 1 , Seyed Mohammad Sajadi 1 , Peyman Irajizad 1 , Hadi Ghasemi 1 Show Abstract
1 , University of Houston, Houston, Texas, United States
Thermal management of high temperature systems through cooling droplets is limited by the existence of the Leidenfrost point (LFP), at which the formation of a continuous vapor film between a hot solid and a cooling droplet diminishes the heat transfer rate. This limit results in a bottleneck for the advancement of the wide spectrum of systems including high-temperature power generation, electronics/photonics, reactors, and spacecraft. Despite a long time effort on development of surfaces for suppression of this phenomenon, this limit has only shifted to higher temperatures, but still exists. Here, we report a new multiscale decoupled hierarchical structure that suppress the Leidenfrost state and provide efficient heat dissipation at high temperatures. The architecture of these structures is composed of a nanomembrane assembled on top of a deep micropillar structure. This architecture allows to independently tune the involved forces and to suppress LFP. Once a cooling droplet contacts these surfaces, by rerouting the path of vapor flow, the cooling droplet remains attached to the hot solid substrates even at high temperatures (up to 570 °C) for heat dissipation with no existence of Leidenfrost phenomenon. These new surfaces offer unprecedented heat dissipation capacity at high temperatures (2 orders of magnitude higher than the other state-of-the-art surfaces). We envision that these surfaces open a new avenue in thermal management of high-temperature systems through spray cooling.
8:00 PM - BM02.05.06
Reduced Coffee Ring Effect by Tunable Wetting of PPy(DBS) Surfaces
Kang Yan 1 , Jian Xu 1 , Wei Xu 2 , Eui-Hyeok Yang 1 Show Abstract
1 Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey, United States, 2 , Brookhaven National Laboratory, Shirley, New York, United States
The coffee ring effect is a ubiquitous phenomenon, which occurs in daily life. The ring-like solid residues along the three-phase contact line is formed after a droplet containing colloidal suspensions or nonvolatile particles evaporates. This coffee ring effect often leads to an undesired inhomogeneous distribution of particles or solutes, which affects their applications on DNA microarrays, coating, inkjet printing and thin film formation. Several techniques have been studied to reduce this effect. For example, electrowetting is found to suppress coffee stains of both colloidal particles of various sizes and DNA solutions by adjusting surface hydrophilicity. Small amount of ionic surfactants can be added to colloidal droplets, which induces Marangoni flow to facilitate uniform deposition of colloidal particles. However, it has been shown that these methods do not provide sufficient condensation of the particles .
In this work, we utilize the electrochemical redox (oxidation and reduction) of polypyrrole-dodecylbenzenesulfonate (PPy(DBS)) to explore controlled suppression of the coffee ring effect. PPy(DBS) surfaces switch their affinity to water during electrochemical redox at very low voltages (<±1V): Reduced PPy(DBS) shows higher water contact angle than oxidized PPy(DBS), which can reduce the coffee ring effect. Furthermore, reduced PPy(DBS) releases DBS- molecules (i.e., surfactants molecules) to aqueous droplets, which can induce the Marangoni flow to further reduce the coffee ring effect.
To this end, we characterize the ring stains resulting from the evaporation of NaNO3 droplets containing polystyrene (PS) microparticles dispersed on PPy(DBS) surfaces under redox. Sequential pinning and unpinning of the droplet contact lines (via switchable hydrophilicity), with varying the concentration of PS microparticles in the solution from 0.1% to 0.005%, generates uniquely distributed deposition patterns. We characterize these deposition patterns, where we find most homogenous deposition patterns on reduced PPy(DBS) at -0.9V. We will further systematically study parameters including voltages, time interval, PPy(DBS) thickness, and NaNO3 concentration to optimize the suppression of ring stains.
 T. Still, P. J. Yunker, and A. G. Yodh, “Surfactant-induced marangoni eddies alter the coffee-rings of evaporating colloidal drops,” Langmuir, 28 (11), 4984–4988, (2012).
8:00 PM - BM02.05.07
Shape-Tunable Amphiphilic Dumbbell-Shaped Particles with pH-Responsive Reversible Surfactant Properties
Kang Hee Ku 1 , Young Jun Lee 1 , Daniel Klinger 2 , Gi-Ra Yi 3 , Se Gyu Jang 4 , Craig Hawker 5 , Bumjoon Kim 1 Show Abstract
1 , Korea Advanced Institute of Science and Technology (KAIST), Daejeon Korea (the Republic of), 2 , Freie Universität Berlin, Berlin Germany, 3 , Sungkyunkwan University, Suwon Korea (the Republic of), 4 , Korea Institute of Science and Technology, Jeonbuk Korea (the Republic of), 5 , University of California, Santa Barbara, Santa Barbara, California, United States
The shape and the chemical components of Janus particles are crucial factors to determine the balance of amphiphiles and their surfactant behavior. We developed a simple strategy to control the shape and relative composition of two different spheres of dumbbell-shaped particles, and exploited to manipulate the pH-responsive formation, breakage, and switching of the Pickering emulsions in response to solution pH. Polystyrene/poly(2-vinylpyridine) (PS/P2VP) with cross-linkable moieties were emulsified to produce dumbbell-shaped particles with different relative sphere sizes and controllable swelling degrees at different pH conditions. Both the phase and the stability of Pickering emulsions were strongly dependent on the geometry and the wettability of dumbbell-shaped particles at the water/oil interface, which is determined by i) the size differences of two spheres and ii) the contact angle of each sphere at the interface. As the anisotropy of dumbbell increased with large swelling behavior, higher contact angle value remarkably increased the overall curvature of emulsion droplets, generating more stable emulsions. A distinct transition behavior of emulsions of toluene/water (i.e. from toluene-in-water to water-in-toluene emulsions) was achieved by adjusting pH condition from 2.0 to 8.0. In particular, the ultrafast transition of emulsion type was reproducible over continuous cycles of pH tuning. Moreover, recovery of dumbbell-shaped particle surfactants with easy separation and purification was demonstrated by incorporating magnetic nanoparticles into the dumbbell-shaped particles, making the system useful for nanoreactors and molecule carriers.
8:00 PM - BM02.05.08
Multi-Functional Microcapsules of Gold Nanoparticles Fabricated by Alpha-Synuclein
Chul-Suk Hong 1 , Jong Tak Lee 1 , Jae Hyung Park 1 , Seung R. Paik 1 Show Abstract
1 , Seoul National University, Seoul Korea (the Republic of)
Bio-applicable cargo delivery system requires biocompatibility, stability, and controlled release by responding to external stimuli at target sites. Here, we introduce microcapsules comprised of a single layer shell of gold nanoparticles (AuNPs) assembled with an amyloidogenic protein of alpha-synuclein (aS). The microcapsules were fabricated by producing oil(CHCl3)-in-water Pickering emulsion of AuNPs encapsulated with aS (aS-AuNPs) followed by stable beta-sheet formation between aS molecules in the presence of CHCl3. The wrinkled skin of microcapsules obtained after evaporation of the internal CHCl3 also reflects robustness of the protein-protein interaction which was reinforced by either heat-treatment or laser-exposure to stimulate the photothermal effect of AuNPs. With Rhodamine 6G (R6G) loaded, its release was demonstrated to be highly sensitive to trypsin-treatment. In addition, low pH (<4) and copper ion affecting the outlying aS were also shown to trigger the cargo release. For additional functionalization of the microcapsules, quantum dots and magnetic nanoparticles were encapsulated in order to enhance their theranostic properties by emitting fluorescence and exhibiting megnetothermal/targeting activities, respectively. The microcapsules could be further functionalized by modifying the surface-exposed aS and encapsulating inverted micelles containing biologically active substances. Taken together, the multi-functional AuNP microcapsules are suggested to be an ideal cargo carrier system which could be employed in biomedical applications as they exhibit structural robustness, target localization, and triggered release.
8:00 PM - BM02.05.09
Anomalous Behaviors of Block Copolymers at the Interface of Incompatible Polymer Blend
Ji Ho Ryu 1 , YongJoo Kim 2 , Won Bo Lee 1 Show Abstract
1 , Seoul National University, Seoul Korea (the Republic of), 2 , Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
We present the effects of structures and stiffness of block copolymers on the interfacial properties of an immiscible homopolymer blend. The diblock and grafted copolymers with variation in stiffness are modeled using coarse-grained molecular dynamics to compare the compatibilization efficiency, i.e. reduction of interfacial tension. Overall, grafted copolymers are located more compactly at the interface and show better compatibilization efficiency than diblock copolymers. In addition, an increase in the stiffness of one block of diblock copolymers causes unusual inhomogeneous interfacial coverage due to bundle formation. On the other hand, an increase in the stiffness of one block of grafted copolymers prevents the bundle formation due to the branched chain. As a result, homogeneous interfacial coverage of homopolymer blends is realized with significant reduction of interfacial tension which makes grafted copolymer can be better candidate for the compatibilizer of immiscible homopolymer blend.
8:00 PM - BM02.05.11
Architecting Emulsion Interfaces for Controlled Dipole-Dipole Interdrop Association
Minchul Sung 1 , Jin Yong Lee 1 , Kyounghee Shin 1 , Jin Woong Kim 1 2 Show Abstract
1 Bionano Technology, Hanyang University, Ansan Korea (the Republic of), 2 Department of Chemical and Molecular Engineering, Hanyang University, Ansan Korea (the Republic of)
This study introduces a new approach to architect the oil/water interface of nanoemulsion drops, in which amphiphilic ABA triblock copolymers and lipid assemble to generate dipole-dipole interdrop association. For this, we first synthesized two kinds of triblock copolymers, poly (ethylene oxide)-b-poly (ε-caprolactone)-b-poly (ethylene oxide) (PEO-b-PCL-b-PEO), with different molecular weights and hydrophilic lipophilic balance values. And then, we fabricated nanoemulsions composed of the triblock copolymers and lecithin with different compositions. The emulsion droplet size ranged in approximately 300-400 nm regardless of the composition of interfacial membrane. The zeta potential was tunable from 0 to -40 mV by varying the concentration of lecithin. The nanoemulsion showed extraordinary stability against repeated freeze-thawing. Moreover, our suspension rheology studies revealed that the addition of lecithin to triblock copolymer membrane led to the dipole-dipole interaction of interdrops between methoxy- terminal group of PEO chain and phosphorylcholrine group of lecithin. Interestingly, we figured out that the enhanced modulus of concentrated nanoemulsions was attributed to effective entanglement of the hydrophilic PEO chains. Exclusively, the modulus of nanoemulsions dramatically decreased at high temperatures due to the collapse of PEO blocks. All these findings support the potential use of our attractive nanoemulsion system over a wide range of applications in drug delivery, cosmetic and food formulations, and life sciences
8:00 PM - BM02.05.12
Dynamics of Wetting for Two Liquid Systems
Joel De Coninck 1 , Juan Carlos Fernandez-Toledano 1 , Terence D. Blake 1 Show Abstract
1 , Univ de Mons, Mons Belgium
We use large-scale molecular dynamics simulations to study the Lennard-Jones forces acting at the various interfaces of a liquid bridge (liquid 1) between two realistic solid plates on the scale of few nanometers when the two free surfaces are in contact with a second immiscible liquid (liquid 2) with an interfacial tension of γ12 . Each plate comprises a regular square planar lattice of atoms arranged in three atomic layers. To maintain rigidity while allowing momentum exchange with the liquid, solid atoms are allowed to vibrate thermally around their initial positions by a strong harmonic potential. By varying the solid− liquid coupling, we investigate a range of nonzero contact angles between the liquid− liquid interface and the solid. We first compute the forces when the plates are stationary (equilibrium case), from the perspectives of both the liquid and the solid. Our results confirm that the normal and tangential components of the computed interfacial forces at each contact line are consistent with Young’ s equation on this small scale. In particular, we show that the tangential force exerted by the liquid− liquid interface on the plates is given by the difference in the individual works of adhesion of the two liquids and equal to γ12 cos θ1,2 where θ1,2 is the equilibrium contact angle measured through liquid 1. This result, which differs from that expected for a single liquid, is relevant to the interactions and behavior of two liquid− solid systems in nanotechnology. We then study the forces when the plates are translated at equal speeds in opposite directions over a range of steady velocities (dynamic case) and repeat the measurements of the force exerted by the liquid− liquid interface on the solid. We find that the normal and tangential components of this force are still correctly predicted by the normal and tangential components of the interfacial tension, provided only that the equilibrium contact angle is replaced by its dynamic analogue θ1,2D. Usually assumed without proof, this result is significant for our proper understanding of dynamic wetting at all scales. More systems such as tubes, … will also be considered and compared to the single liquid case.
8:00 PM - BM02.05.13
Synthetic, Anisotropic Polymer Particles Derived from Cellular Structures
Bryan Kaehr 1 2 , Kristin Meyer 1 , Nick Labriola 3 , Eric Darling 3 , Katherine Latimer 2 Show Abstract
1 Advanced Materials Lab, Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 Chemical and Biological Engineering, The University of New Mexico, Albuquerque, New Mexico, United States, 3 Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, Rhode Island, United States
Biological cells are masters of liquid phase segregation to achieve the evolutionarily honed compartmentalization necessary for living functions. Considered as a multiphase solution, cells such as erythrocytes have solved the challenge of overcoming viscous and capillary forces to form relatively stable and deformable non-spherical particles and materials. Abilities to synthetically replicate the complex morphology and mechanical properties of single cells would impact many areas of materials science and medicine and has thus received considerable attention using emulsion, microfluidic and lithographic strategies.
Here we describe a cell-directed route to replicate cellular structures into hydrogel materials such as polyethylene glycol (PEG). First, the internal and external surfaces of chemically fixed cells are replicated in a conformal layer of silica using a sol-gel process. The template is subsequently removed to render shape-preserved, mesoporous silica replicas. Infiltration and crosslinking of PEG precursors and dissolution of the silica results in a soft hydrogel replica of the cellular template as demonstrated using erythrocytes, Hela, and neuronal cultured cells. We find that the elastic modulus can be tuned over an order of magnitude (~10-100 kPa) though with a high degree of variability. Furthermore, synthesis without removing the biotemplate results in stimuli responsive particles that swell/deswell in response to changes in pH and ionic strength due to the properties of crosslinked cellular proteins (primarily hemoglobin for erythrocytes). Overall this work provides a foundation to develop soft particles with nearly limitless architectural complexity derived from dynamic biological templates.
8:00 PM - BM02.05.14
Digital Microfluidic Methods for Forming Droplets of Low-Surface-Energy Fluids, Combining Them into Emulsions and Transforming Them into Polymer Shells
David Harding 1 2 , Brandon Chock 1 2 , Thomas Jones 3 2 Show Abstract
1 Department of Chemical Engineering, University of Rochester, Rochester, New York, United States, 2 Laboratory for Laser Energetics, University of Rochester, Rochester, New York, United States, 3 Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York, United States
The production and manipulation of droplets ranging in size from 0.3 to 20 μL to form polymer shells is done routinely to produce fuel capsules for laser-driven Inertial Confinement Fusion experiments.1 The process consists of creating an emulsion of two immiscible fluids with the outer fluid containing a polymer, which is encapsulated by a third immiscible fluid and transformed into a spherical shell (<1% nonsphericity) with a uniformly thick wall. The polymer shell maybe either fully dense or a low-density foam (~10%), depending on the chemicals present in the fluids.
Digital microfluidics is a relatively new technique that is being investigated as a possible method for producing the desired emulsions and polymer shells. This presentation describes how electric fields are used to form droplets of fluids from large reservoirs and combine them into emulsions. The amount of fluid in each droplet is precisely controlled (as small as 7±0.4 nL and as large as 30±1.8 μL) to produce shells with tightly controlled dimensions (0.9- or 4-mm diameter with a wall 0.008- or 0.36-mm thick, respectively). Two fluid/polymer emulsions are discussed: (i) an oil and water emulsion, where the water phase contains resorcinol and formaldehyde that react to produce shells with a foam wall; and (ii) a water and oil emulsion, where the water phase contains acetonitrile and the oil phase is styrene, isobutanol, and a photoinitiator. The latter emulsion is formed into polystyrene shells.
The production and transport of these droplets is done using electrowetting-on-dielectric and dielectrophoresis techniques. The electrode designs and electrical conditions (voltage and frequency) that are needed to accomplish this are reviewed.
This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Numbers DE-NA0001944 and DE-NA0001369, the University of Rochester, and the New York State Energy Research and Development Authority. The support of DOE does not constitute an endorsement by DOE of the views expressed in this article.
1. R. S. Craxton et al., Phys. Plasmas 22, 110501 (2015).
8:00 PM - BM02.05.15
Phase-Field Simulations of Thermally-Induced Phase Separation in Polymer Solutions
M. Cervellere 1 , Paul Millett 1 , Xianghong Qian 1 Show Abstract
1 , University of Arkansas, Fayetteville, Arkansas, United States
Phase inversion, a process that occurs when a polymer collapses from solution into a thin film upon quenching or exposure to a non-solvent, is the most widely used process for producing porous polymer membranes. The level of understanding of this manufacturing processes remains mostly empirical, with little theoretical basis to connect the process conditions and important quantitative membrane characteristics. This gap in knowledge necessitates a substantial amount of trial-and-error experimental work to discover and define the “process window” for a particular membrane product, which increases R&D costs and limits innovation of new membrane products or processes. We have developed mesoscopic simulation models to examine the dynamics of the liquid-liquid phase inversion process to predict the morphology of pore structures that develop within polymer membrane filters. The computational approach for modeling phase inversion is a novel phase-field method that utilizes Cahn Hilliard equations that incorporate the thermodynamic and kinetic parameters relevant to phase separation in polymer solutions. The modeling tools developed will enable significant speed-up in membrane development. This presentation will focus on the computational results of the Cahn Hilliard model and compare simulated structures and morphologies to current manufactured polymer membrane filters. This project is supported by the NSF and 3M through the Membrane Advanced Science and Technology (MAST) Center.
8:00 PM - BM02.05.16
Robust Photonic Microparticles Comprised of Cholesteric Liquid Crystals for Anti-Forgery Materials
Hyeon Jin Seo 1 , Sang Seok Lee 2 , Jong Chan Won 1 , Cheolmin Park 3 , Shin-Hyun Kim 2 , Yun Ho Kim 1 Show Abstract
1 Advanced Materials Division, Korea Research Institute of Chemical Technology (KRICT), Daejeon Korea (the Republic of), 2 Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon Korea (the Republic of), 3 Department of Materials Science and Engineering, Yonsei University, Seoul Korea (the Democratic People's Republic of)
Cholesteric liquid crystals (CLCs) possess photonic bandgap owing to the helical arrangement of molecules. The CLCs reflect circularly-polarized light of a specific handedness and wavelength, exhibiting colors. The wavelength of the selective reflection, or the structural color, can be easily controlled by varying the concentration of a chiral dopant. Although such a unique optical property renders CLCs promising for various applications, their fluidity severely limits the ease of processing and structural stability. To overcome the limitation, we design CLC microparticles (CLC-MPs) by photopolymerization of reactive mesogens (RMs) in CLC droplets. With capillary microfluidic devices, highly uniform emulsion drops of CLC-RM mixtures are prepared in an aqueous phase drops, which are then exposed to ultraviolet (UV) to yield solid microparticles. The diameter of the CLC-MPs is precisely controlled by either manipulating the flow rates of dispersed and continuous phases or varying the diameter of the capillary orifice in the microfluidic devices. The wavelength of reflection and handedness of helical structure are selected by the composition of the dispersed phase. The photo-polymerization of RMs leads to the formation of a three-dimensional rigid network, thereby yielding the CLC-MPs with high mechanical stability. The CLC-MPs could be further assembled to form two-dimensional hexagonal arrays on flat surfaces or deposited in pre-defined trenches or holes by a mechanical rubbing. Two distinct CLC-MPs with opposite handedness can be patterned to show different color graphics depending on the selection of handedness of circularly-polarized light, which are appealing for anti-forgery patches.
8:00 PM - BM02.05.17
Designing Versatile Hollow Microcapsule with Controlled Spatial Position through the Metal-Phenolic Interaction Based on Microfluidic Generation
Gwan Hyun Choi 1 , Pil Jin Yoo 1 Show Abstract
1 , Sungkyunkwan University, Suwon Korea (the Republic of)
Recent developments in the field of chemical engineering have led to a renewed interest in the manipulation of liquid-liquid (Liq.-Liq.) interfaces between multiphase for a wide range of scientific and industrial processes such as liquid-liquid extraction, separation process, and emulsions. Above all things, emulsion technology has emerged as powerful platforms for soft-template for the formation of solid phase at the Liq.-Liq. interfaces by exploiting interfacial localized reaction or adsorption of functional materials.
As far as the size distribution of emulsion is concerned, the microfluidic technique performed by elaborate means of capillary device enable to generate highly monodisperse-sized emulsion with micrometer scale. In most cases, double-emulsion system has been exploited with subsequent solidification of the materials in middle phases resulting in the solid shell of the microcapsule. However, concern of this method is that it is difficult to diversify function of film which strongly depends on the composition of materials used in the middle phase. In order to add new functions for the practical usage, it requires tuning of starting materials containing additional synthesize step which results in change of solubility or another physicochemical properties.
Particularly, in order to fabricate high performance capsule, requirements can be divided into two categories: one is manipulating shell composition to control film with desired functions varied with components of materials, and the other is arranging deterministic position of the shell to spatially control the sequential function of capsule in more complex system such as multiple emulsions. One possible implication of spatial control of film position in the multi-capsules is that it enable sequential combination of capsule functions in a diverse way. So far, very little attention has been paid to the role of control of the spatial position. Because it is technically challenging to possess diverse functions with spatially controlled position and there exists trade-off relationship between simple fabrication process and multi-functions of capsules. Therefore, it is imperative to develop versatile and multi-functional capsule with new chemistry for precisely controllable properties including size, porosity, stability, spatial position and shell composition by facile means of experimental methods.
In this work, we combine these two techniques: the microfluidics and metal-phenolic chemistry, as promising tools for designing versatile hollow functional microcapsule. By taking advantages of both techniques, it is available to fabricate multiple functional capsules with spatially controlled position by simply utilizing Liq.-Liq. interfacial reaction of metal-phenolic chemistry. It is expected that this approach makes a major contribution to research on the role of the spatially sequential combination of various functional capsules.
8:00 PM - BM02.05.18
Inkjet Printed Femtoliter Scale Water-in-Oil Drop Compartments on a Chip for Molecular Confinement Applications
Felicia Cavaleri 1 , Giuseppe Arrabito 1 , Alessandro Porchetta 2 , Francesco Ricci 2 , Valeria Vetri 1 , Maurizio Leone 1 , Pignataro Bruno 1 Show Abstract
1 Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Palermo Italy, 2 Dipartimento di Scienze e Tecnologie Chimiche, Università degli Studi di Roma "Tor Vergata", Roma Italy
Molecular confinement leads to acceleration of molecular dynamics along with surface interaction. Nature employs confinement in molecularly crowded, heterogeneous femtoliter (fL) compartments inside living cells in order to obtain higher reaction efficiency and spatial-programming of complex biochemical processes (1). Being inspired by Nature, we here design a novel on chip droplet assembling approach to produce molecular confinement inside aqueous fL droplets by inkjet printing. Droplets by inkjet printing are normally up to picoliter scale (2), being droplet size dependent on the nozzle diameter (typically not below 10 µm). Recent approaches show the possibility to reduce droplets volume down to the attoliter scale by reducing the nozzle radius or by employing electric fields, but these approaches can cause nozzle clogging or should require electrolyte media support in solution.
Here we show a novel actuating waveform that permits to assemble on a chip fL aqueous droplets in oil drops from 10 µm size nozzles, by a “field-free” piezoelectric inkjet printer. Water/oil interface is stabilized by a polymeric surfactant. Molecules are confined at the border of fL drops, giving rise to regular ring-shaped patterns with thickness below 1 micron. We test confinement effects by Fluorescence lifetime imaging (FLIM) at the single droplet level, discovering significant differences in characteristic lifetimes of environmental sensitive molecules (e.g. Fluorescein or proteins) with respect to macroscopic solutions. Interestingly, the fluorescence lifetime of molecular rotors increases with the environment viscosity - not revealing any change not even at the evident higher intensity ring pattern observed at the drop border. We observed that the fL droplet environment does not modify high affinity intermolecular interactions such as Streptavidin-Biotin (3).
Finally, we tested the functionality of a model DNA-based nanomachine in aqueous solution under confinement conditions provided by the drop. In particular, we used a model DNA beacon activated by a strand displacement mechanism. Fluorescence measurements clearly show that DNA beacon conformation is changed in the fl drop with respect to the one observed in large volumes. We ascribe the observed behavior to single strand elongation and molecular ordering phenomena of DNA strands occurring in presence of surfactants at the interface according to DNA Ψ-phase condensation models (4).
1) M.M. K. Hansen et al., Nat Nanotech 2016, 11, 191.
2) G. Arrabito et al., Lab on a Chip 2016, 16, 4666.
3) S. Shipovskov et al., ChemPhysChem 2012, 13, 3179.
4) C. Zhang et al., PNAS 2009, 106, 16651.
8:00 PM - BM02.05.19
Facile Preparation of Liposomes by Squeezing from Flexible Macroporous Monoliths
Gen Hayase 1 , Shin-ichiro Nomura 1 Show Abstract
1 , Tohoku University, Sendai Japan
Methods for preparing capsules such as nanomicelles and liposomes as carriers have been studied for the application to drug delivery system (DDS) to deliver the targeted drug only to the intended place in the body. For practical use, a facile process for introducing various chemicals is desired, but existing methods still have problems. We report a new interface control method to rapidly prepare liposomes with various internal compositions by utilizing inner smooth surface of flexible macroporous monoliths. In addition, we will also present application on cell-free protein synthesis.
8:00 PM - BM02.05.20
Modeling Effects of Salinity and Temperature on the Dynamics of Polyacrylamide Gels in Oil-Water Mixtures
Chandan Choudhury 1 , Olga Kuksenok 1 Show Abstract
1 Material Science and Engineering, Clemson University, Clemson, South Carolina, United States
Maximizing the recovery of oil from mature oil fields is one the major challenges for the petroleum industry; after primary and secondary recoveries, about two-thirds of oil remains trapped in the reservoir pores. Gel treatments are commonly used in a number of enhanced oil recovery (EOR) techniques. A number of EOR approaches are based on polyacrylamide (PAM) polymers and PAM gels. For example, a recently developed deep reservoir treatment consists of dual cross-linked PAM gel particles with permanent and thermally breakable cross-links1,2. High temperatures deep within the injection wall result in breaking the temperature-sensitive cross-links; the gel particles then swell and block the rock pores, thus reducing the permeability of the rock in the thief zones and improving the EOR. Herein, we develop a Dissipative Particle Dynamics approach to model the dynamics of gel with two types of cross-links within the water/oil mixtures. We first focus on tailoring the interfacial tension of oil/water emulsions with these polymers varying temperatures and salinity by choosing the concentrations close to these at well-bores. We then, consider various architectures of these gels and the effect of shear flow on the dynamics of these complex system. Our results show that tailoring the gel properties affects gel-oil interactions. Our findings could potentially optimize the design principles for PAM-based gel treatments for the enhanced oil recovery.
1. Kelland, M. A. Production chemicals for the oil and gas industry. CRC Press, (2014).
2. Chen, Z. et al. Journal of Applied Polymer Science 134.13 (2017).
8:00 PM - BM02.05.21
Mesoscale Computer Simulations of Surface-Directed Phase Separation in Immiscible Liquid Films
Michael Wise 1 , Paul Millett 1 Show Abstract
1 Mechanical Engineering, University of Arkansas, Fayetteville, Arkansas, United States
Phase separation in immiscible liquids can be significantly altered by surface wetting conditions. Here, we demonstrate through large-scale computer simulations that unique phase morphologies emerge in immiscible liquids confined between two planar surfaces that are completely wetted by one of the liquid phases. A Cahn-Hilliard model with additional surface interactions for the selected wetting liquid was employed to capture the separation process in large three-dimensional simulations. The outcomes of varying film thickness as well as the volume fractions of the two liquids were explored to investigate the effect on the resulting morphologies. It was found that, due to the formation of wetting layers of one liquid, an inner bicontinuous morphology could be achieved using low concentrations of the non-wetting liquid at various film thicknesses. The results from this computational study may guide the development of novel thin-film porous membrane materials.
8:00 PM - BM02.05.22
Light-Induced Thermoelectric Response in Plasmonic Nanofluids via Convection, Thermophoresis and Nanobubbles
James McQuade 1 , Heriberto Vasquez-Carrasco 2 , Luat Vuong 2 Show Abstract
1 Chemistry, Queens College, Flushing, New York, United States, 2 Physics, Queens College, Flushing, New York, United States
Thermoelectric effects, such as Thompson Effect, Seebeck Effect, and Soret Effect, have been observed and described in colloidal suspensions. The behavior of the suspended particles as well as the liquid constituents in response to temperature gradients are of considerable interest, and have been utilized in applications including nanoparticle assembly, thermophoretic separations, heat transfer materials, and thermoelectric devices. In particular, the plasmonic response of metal nanocolloids can lead to large temperature gradients and anomalous thermal behavior, such as the production of ethanol vapor directly in the absence of the usual azeotropic behavior. However, the thermoelectric behavior of plasmonic nanofluids has not yet been thoroughly studied.
Here, we measure a thermoelectric current in a plasmonic nanofluid induced by light at the plasmon resonance. A number of highly-sensitive experimental configurations are used to probe the dynamics using non-interacting silver electrodes in different geometries. Modification of the solvent chemistry is found to have significant effects on the electrical behavior, through the onset of convection and solvent evaporation as well as other flow effects and the influence of the solvent hydrogen bond networks. For the first time, electrical measurements are combined with imaging and analysis of the far-field thermal diffraction patterns, allowing the current readings to be correlated with the thermal diffusion occurring in the liquid phase. The current readings are interpreted in light of fluid properties such as thermo-optic coefficient, heat capacity, viscosity, and thermal expansivity to provide guides for further study of plasmon-mediated thermoelectric systems. We present detailed simulations of nanoparticle-fluid interactions to describe the fluid motion and thermal diffusion.
This study represents one of the first investigations of light-induced electrokinetics with plasmonic nanofluids. We hope to contribute not only to emerging photothermoelectric technologies, but also to the harnessing of thermophoresis for lab-on-a-chip technology, and the use of plasmonic effects in chemistry. We contribute to the fundamental understanding of the behavior of plasmonic nanofluids, particularly in regard to fluid flow, thermal diffusion, and photoinduced effects, as well as their effects on thermoelectric behavior.
8:00 PM - BM02.05.23
Mitigation of Asphaltene Adsorption Using Lubricant Impregnated Surfaces
Henri-Louis Girard 1 , Philippe Bourrianne 1 , Robert Cohen 1 , Gareth McKinley 1 , Kripa Varanasi 1 Show Abstract
1 , MIT, Cambridge, Massachusetts, United States
Asphaltene are heavy organic molecules found in crude oil. They exhibit aromatic, aliphatic and polar regions that allow them to adsorb readily on industrial surfaces and eventually lead to clogging of pipes, contaminations of equipment... We investigate the adsorption of these molecules at liquid-liquid interfaces through interfacial tension measurements. Then, we develop a lubricant impregnated surface that prevents asphaltene adsorption and remains thermodynamically stable in aromatic and aliphatic solvents (Toluene and Heptane, respectively). We characterize the effectiveness of such surfaces with various techniques: contact angle measurements, XPS, stability to shear flow.
8:00 PM - BM02.05.24
Generating Monodisperse, Two-Phase Liquid Colloid Droplets Using Microfluidics
Kent Harvey 1 Show Abstract
1 , MIT, Boston, Massachusetts, United States
Multiphase, complex emulsions of two or more immiscible fluids offer potential applications as tunable microlenses and as sensors for various biological and chemical analytes. Cooling a mixture of hydrocarbon (HC) and fluorocarbon (FC) oils after emulsification above the upper consulate temperature leads to structured droplet emulsions of HC and FC in water, which can be alternated between encapsulated states (HC in FC, or FC in HC) and a Janus state. For sensing purposes, surface functionalization and stimuli-responsive surfactants can be used to induce a detectable change in morphology in the presence of specific analytes. However, sensor sensitivity and consistency can vary based on the method of droplet emulsion generation. Using a microfluidic approach for generation of these emulsions offers a solution to these issues. By generating smaller droplets, sensitivity for molecular analysis can be greatly improved, and could even enable single bacteria-cell detection. Microfluidics allow for parallelization, creating monodisperse droplets with precisely controlled sizes, morphologies, and internal structures that can be used in an array for consistent quantitative throughput. Here, we present on generation of complex emulsions of various sizes with high monodispersity using a flow-focusing microfluidic device. The ability to precisely control droplet size and polydispersity will be important for the development of new optical transduction methods for detection of both small molecules and biomolecules.
8:00 PM - BM02.05.25
Flow Shear Tomography with Luminescent Nanorods
Jongwook Kim 1 , Sebastien Michelin 1 , Charles N. Baroud 1 , Lucio Martinelli 1 , Michiel Hilbers 2 , Albert M. Brouwer 2 , Jacques Peretti 1 , Thierry Gacoin 1 Show Abstract
1 , Ecole Polytechnique, Palaiseau France, 2 , University of Amsterdam, Amsterdam Netherlands
Direct measurement of the local shear rate in micro- and bio-fluidic systems is a challenging but essential task to understand various phenomena (e.g. blood capillary flows, separation and mixing mechanisms, biomechanical response of cells). Although shear profiles can be deduced from the particle imaging velocimetry (PIV) data, the accessible dynamic and resolution ranges are limited especially for non-stationary flows. We present an alternative method to probe directly the local shear rate by observing the shear-induced orientation of luminescent nanorods rather than tracking their displacements. Orientation of rod-like objects under flow is a ubiquitous effect. At the nanoscale, the balance between the shear force and the thermal relaxation sets a strong correlation between the shear rate vector (γ) and the director (n) and order parameter (S) of the particles’ collective orientation. We fabricated rare-earth phosphor nanorods (Eu-doped LaPO4) that exhibit peculiarly polarized luminescence, which allows to determine the three-dimensional rod-orientation by a simple spectroscopic analysis . By monitoring the local (inside the focal volume) but collective orientation of these tiny nanorods (diameter = 10 nm, length = 200 nm) dispersed in the fluid, we measure the local shear rate in a microfluidic channel with a complex geometry. The potential of this approach is demonstrated through a tomographic mapping of the shear rate distribution in the channel by using a scanning fluorescence confocal microscopy .
 J Kim*, L Martinelli, J-P Boilot, E Fradet, S Michelin, C Baroud, M Hilbers, A M Brouwer, J Peretti, T. Gacoin* “Monitoring the orientation of rare-earth doped nanorods for flow shear tomography” Nature Nanotechnology (2017) DOI: 10.1038/nnano.2017.111
8:00 PM - BM02.05.26
Graphene as a Two-Dimensional Surfactant
William Dickinson 1 , Douglas Adamson 2 , Hannes Schniepp 1 Show Abstract
1 , College of William & Mary, Williamsburg, Virginia, United States, 2 , University of Connecticut, Storrs, Connecticut, United States
Graphene exhibits a surprisingly strong attraction to the interface of two immiscible solvents, which is interesting from both a fundamental and an application point of view. At the heptane/water interface graphite particles spontaneously exfoliate into thinner and thinner sheets due to this interaction, which can be used to mass-produce pristine graphene at bulk quantities, but also to make conductive graphene surface coatings at a large scale. Moreover, this high degree of surface activity of graphene can be used to stabilize liquid/liquid interfaces, giving rise to the notion of graphene sheets as surfactants, albeit with a 2D morphology. This property can be exploited for Pickering emulsions with novel properties tuned by the geometry of the employed graphene sheets. Based on such emulsions we have successfully produced graphene-based foams, polymer nanocomposites, and other structures of various geometries.
We have used force spectroscopy to study the interactions of graphene with the liquid/liquid interface in a rigorous way. Therefore, we functionalized colloidal atomic force microscopy probes and moved them relative to the interface of pinned droplets. Analysis of force spectroscopy results at this interface is then used to improve our understanding of the peculiar behavior of graphene observed under such conditions. Our experimental efforts at the nano- and macroscale are complemented by calculations and molecular dynamics simulations. To characterize the obtained graphene surface coatings we also developed a low-cost, high-throughput optical method, which rapidly provides the lateral dimensions of thousands of graphene sheets, as well as their thickness with single-layer resolution. In addition, the method has enough sensitivity to characterize the oxidation state of graphene sheets with different degrees of functionalization. This optical method is universally applicable to other 2D materials.
8:00 PM - BM02.05.27
Remote Droplet Manipulation on Self-Healing Thermally Activated Magnetic Slippery Surfaces
Peyman Irajizad 1 , Sahil Ray 1 , Nazanin Farokhnia 1 , Steven Baldelli 1 , Hadi Ghasemi 1 Show Abstract
1 , University of Houston, Houston, Texas, United States
Manipulation of discrete droplets is a paramount procedure in a broad spectrum of disciplines from digital microfluidics to energy and water systems. In these applications, droplet manipulation is required for mass or energy transport in various physical and chemical interactions. The discrete droplet manipulation enables developments of integrated microfluidic platforms without the use of conventional pumps, valves, or channels. A variety of approaches are developed for droplet manipulation. In these approaches, either the solid surface characteristics or droplet properties are tuned to control the droplet motion. However, drawbacks such as custom fabrication of the solid surface (e.g., embodiment of actuators in the solid and physical or chemical modification), limited application for high viscous fluids, fixed functionalities, and enhanced friction by the solid substrate have impeded their widespread implementation. Here, a new self-healing surface called magnetic slippery surface (MAGSS) is reported for remote and controlled droplet manipulation with exceptional droplet mobility and a wide range of functionalities (e.g., transportation, guidance, removal, and merging of droplets). This surface allows droplet manipulation in a channel-free configuration independent of viscosity of the droplet. This study envisions that MAGSS emerges as a disruptive platform for energy systems (e.g., condensation), miniature reactors, microfluidics devices, and medical bioassays.
8:00 PM - BM02.05.28
Durable Droplet Networks with Emergent Functional Properties
Elio Challita 1 , Donald Leo 1 , Eric Freeman 1 Show Abstract
1 , The University of Georgia, Athens, Georgia, United States
Droplet based materials consist of aqueous droplets dispersed in an oil reservoir with dissolved phospholipids. Manipulating these droplets into contact spontaneously forms biological membranes at their intersections, and multiple droplets linked together can form large 2D and 3D complex tissue mimics with emergent transducing properties. These droplet-based structures may be further functionalized with transmembrane pores thus providing them with the ability to operate as electromechanical devices and biosensors. These materials have been investigated for applications ranging from sensing to energy conversion, drawing inspiration from naturally occurring cellular systems. One particular restriction to these systems however, is the usage of the bulk oil phase which limits their usability outside the lab environment: the network architecture is delicate and prone to degradation with time.
This paper examines a solution for the delicate droplet networks through solidification with the aim of producing a stimuli-responsive composite material. This was achieved first by replacing the oil phase with a block copolymer organogel. The latter is a temperature-sensitive thermoplastic elastomeric gel (TPEG) comprised of poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) mixed with low-volatility, midblock-compatible hexadecane oil. The organogel has been previously proven to provide both a suitable environment to form artificial lipid bilayer membrane formation at high temperature when the organogel is at its liquid state and a stable solid-like scaffold for the lipid membranes at room temperature. A custom-made pressure-based 3D printing device is used to precisely print the different droplet architectures at high temperature. Once the printing is finished, the organogel is cooled to room temperature without disrupting the interfacial membranes. The water-in-gel mixture is then coated with a thin polyurethane film. Not only does the polyurethane layer ensure the portability and durability of the system, but it also permits the affixation of stable Ag/AgCl electrodes within the system which could allow chip-to-chip electrical communication. The final manufactured product is a composite, modular, and scalable material, capable of replicating biomolecular functionalities and compatible with printing large collections of droplets for emergent behaviors.
Paul Millett, University of Arkansas
Esther Amstad, Ecole Polytechnique Federale de Lausanne
Paul Clegg, University of Edinburgh
Daeyeon Lee, University of Pennsylvania
BM02.06: Microfluidics II
Tuesday AM, November 28, 2017
Sheraton, 2nd Floor, Back Bay A
8:30 AM - *BM02.06.01
Droplet Microfluidics for Designing Photonic Capsules Containing Colloidal Crystals
Tae Min Choi 1 , Shin-Hyun Kim 1 Show Abstract
1 , Korea Advanced Institute of Science and Technology (KAIST), Daejeon Korea (the Republic of)
Colloidal crystals possess a photonic stopband as refractive index is periodically modulated in the structures. The stopband develops the colors through the reflection of selected wavelength of light when it is located in the visible. The structural colors are iridescent, never fade as long as the structure persists, and tunable by adjusting interparticle distance, which render the colloidal crystals promising for various coloration and sensing applications. However, a conventional film format of the crystals has low post-processability and reconfigurability, restricting the use. A granular format is expected to overcome the limitations of the film format. Furthermore, the granules, designed to have fluidic compartments containing colloidal crystals, potentially provide in-situ color tuning. To design such photonic capsules in a controlled manner, we have used droplet microfluidics. With a capillary microfluidic device, water-in-oil-in-water (W/O/W) double-emulsion drops are prepared, which are then used as a template to produce the photonic capsules. Innermost water phase contains colloidal particles to build colloidal crystals and middle oil phase is either photo- or thermo-curable monomer to form a stable polymeric membrane. To crystallize the colloidal particles in the innermost water phase, two opposite interparticle potentials of repulsion and attraction are employed, respectively. Colloidal particles with surface charges have the repulsive potential due to electrical double-layer interaction. The particles spontaneously form non-close packed crystals in the core above a certain volume fraction by occupying the whole volume of the innermost phase. The colloidal crystals are formed by aligning the hexagonal array of crystals along the inner wall of the spherical core at an early stage, resulting in the isotropic photonic property. The crystals slowly evolve into a single crystal by rearrangement. The photonic capsules containing a single crystal have anisotropic photonic property as crystal planes that are aligned parallel to the wall are different depending on the location. The attractive potential is achieved by depletion interaction. When the depletant is dissolved in the innermost phase in the presence of salts, attractive potential overwhelms the repulsive one. The depletion attraction leads to the formation of close-packed crystals, which results in many crystallites along the inner wall and no particles in the center. As the close-packed crystals coexist with the particle-depleted center, the volume change of each colloidal particle can lead to a change of lattice constant; this is difficult to achieve with nonclose-packed crystals prepared by repulsive potential. When the colloidal particles are composed of an insensitive core and temperature-sensitive shell, the crystallites in the core exhibit a drastic temperature-dependent color change.
9:00 AM - BM02.06.02
Reaction-Diffusion-Convection Chemical Computer—Marangoni Flow Driven Maze Solving
Rita Toth 1 , Kohta Suzuno 2 , Petra Lovass 3 , Michal Branicki 4 , Artur Braun 1 , Daishin Ueyama 2 , Istvan Lagzi 3 Show Abstract
1 , Swiss Federal Laboratories for Materials Science and Technology, Dübendorf Switzerland, 2 , Meji University, Tokyo Japan, 3 , Budapest University of Technology and Economics, Budapest Hungary, 4 , University of Edinburgh, Edinburgh United Kingdom
Algorithmic approaches to maze solving and shortest path problems are generally computationally expensive. In the past few decades several chemical and physical methods have been proposed to provide a more efficient alternative. We demonstrate a novel chemical method for maze solving which relies on the Marangoni flow induced by either a surface tension or temperature gradient between the entrance and the exit of the maze. Fluid flow maintained by the gradient (Marangoni flow) drags dye particles at the liquid-air interface from the entrance to the exit of the maze. The flow is most intense along the shortest path, therefore most of the particles travel this way. Accordingly, the shortest path is marked by the most intense color. The longer paths, which also solve the maze, emerge subsequently as they are associated with weaker branches of the chemically-induced Marangoni flow. Our model reproduced the main behavior observed in experiments.
9:15 AM - BM02.06.03
Broadband Microwave Microfluidics of Complex Fluids
Angela Stelson 1 , Cully Little 1 , Nathan Orloff 1 , James Booth 1 Show Abstract
1 Communications Technology Laboratory, National Institute of Standards and Technology, Boulder, Colorado, United States
Microwave microfluidics is an emergent technique for characterizing conductivity and permittivity of fluids and has wide-ranging applications in the materials science and biomedical fields. The electrical properties of a complex fluid as a function of frequency can be leveraged to characterize the properties of the individual components (e.g. colloids or nanoparticles), as well as the interface effects such as electrical double layers and bound water molecules. However, extraction of quantitative electrical properties over a wide range of frequencies (100 kHz- 100 GHz) is nontrivial, and extensive calibration is required. Here, we utilize a microfluidics device with microwave circuitry incorporated to characterize the broadband properties of colloid suspensions in situ and non-destructively. We measure the bulk properties of colloidal suspensions up to 110 GHz, and use effective medium theory to quantitatively determine the permittivity and conductivity of the particles. We also characterize the dielectric relaxation signatures of charge-stabilized and sterically stabilized particles, demonstrating the viability of this technique for probing surface chemistry in suspensions. This technique is broadly applicable to many suspension systems, and provides information critical to advancing understanding of electric field-responsive systems.
9:30 AM - BM02.06.04
Biomimetic Crystallization Using a Crystal Hotel Microfluidic Device
Yi-Yeoun Kim 1 , Mark Levenstein 1 , Xiuqing Gong 1 , Colin Freeman 2 , Fiona Meldrum 1 Show Abstract
1 , Univ of Leeds, Leeds United Kingdom, 2 , The University of Sheffield, Sheffield United Kingdom
Soluble additives in synthetic and biological crystallization processes are one of the most widely used means of controlling the size, shape and structure of crystalline materials. However, due to the rapid change in size of small crystals, little is known about the influence of additives on the early stages of growth. Here, we profit from the fact that crystallization proceeds slower in small volumes than in bulk solution to investigate the effects of the contrasting soluble additives Mg2+ and poly(styrene sulfonate) (PSS) on the early stages of crystallization of biological important material, calcium carbonate. “crystal hotel” microfluidic device comprises a series of static droplets ("rooms"), each of which offers an independent, structured reaction environment. By precipitating calcium carbonate within this well-defined nanoliter droplet, it reveals that additives only affect shape after the crystals have reached sizes of at least 100 nm. As the crystal grows, the density of specific surface sites to which the additives bind increases. Only when this is high enough will changes in shape become evident. Moreover, by constructing a 2D pattern of micro-pillars in each room and operating controlled flow of ions and additives into the room, we demonstrate levels of control over crystallization comparable to those in biomineralization processes.
This work develops our understanding of effective control over crystallization by simutaneously utilizing biological strategies such as additives, templating and controlled flows. This will ultimately enable us to optimise the synthesis of crystalline materials such as nanostructures, to minimise undesirable processes such as scale deposition or kidney stone formation.
9:45 AM - BM02.06.05
Microfluidic Self-Templating Synthesis of Anisotropic Hollow Mesoporous Silica Ellipsoids
Nanjing Hao 1 , Yuan Nie 1 , John Zhang 1 Show Abstract
1 , Dartmouth College, Hanover, New Hampshire, United States
Hollow mesoporous silica nanomaterials (HMSNs) have attracted considerable attentions in various fields such as biosensing, drug delivery, energy, and catalysis due to their unique properties of typical thin shell, large inner void, large pore volume and good biocompatibility [1, 2]. Over the past two decades, great efforts have been devoted to the rational design of HMSNs for maximizing their application efficacies through optimizing the physicochemical characteristics, including particle size, pore, and surface chemistry. However, most reported materials were those of spherical shape, and research on anisotropic shaped MSNs still lagged . In this study, we firstly developed microfluidics-based anisotropic mesoporous silica ellipsoids (MSEs) with well-ordered parallel channels along the short axis using CTAB and tyrosine as structure directing agents.Microfluidic laminar flows provide fast operation and automation of multi-step synthesis, and there is great potential to combine chemical reactions, purification, and analysis together in a single microchip for realizing the “lab-on-chip” for advanced nanomaterials design [4, 5]. Miniaturized spiral-shaped microfluidic device was then designed as a self-template directing tool to successfully produce hollow MSEs (HMSEs) using PBS as the etching agent and BSA protein as the surface protective coating agent at room temperature. Compared with conventional methods, which usually require hard or soft templates  and post-template-removal process by either calcination at elevated high temperature or selective dissolution in strong acid/basic solvents [7, 8], the microfluidics-based synthesis method we proposed here is rapid, effective and efficient, producing final products with controllable size and morphology in a continuous and reproducible way. The microfluidic platform also provides the flexibility and fine control of the shape evolution toward hollow nanostructure, through adjusting key design parameters of the microfluidic channels and the operating conditions such as the flow rate. We demonstrated the applications of the synthesized MSEs and HMSEs, both of which exhibited superior performance in nanomedicine in terms of high drug loading capacity, controllable drug release, and enhanced cancer cell inhibition activity.
 F.Q. Tang, L.L. Li, D. Chen, Adv. Mater. 24 (2012) 1504–1534.
 X.W. Lou, L.A. Archer, Z.C. Yang, Adv. Mater. 20 (2008) 3987–4019.
 N.J. Hao, L.F. Li, F.Q. Tang, Int. Mater. Rev. 62 (2017) 57–77.
 G. M. Whitesides, Nature 442 (2006), 368–73.
 Y. Nie, N. J. Hao, John X. J. Zhang, Scientific Reports, 2017. DOI: 10.1038/s41598-017-12856-9.
 N. Hao, L. Li, F. Tang, Biomater. Sci. 4 (2016), 575-591.
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 N.J. Hao, X. Chen, S. Jeon, M. Yan, Adv. Healthc. Mater. 4 (2015) 2797–2801.
BM02.07: Colloids III
Tuesday AM, November 28, 2017
Sheraton, 2nd Floor, Back Bay A
10:30 AM - *BM02.07.01
Formation of Complex Nanoemulsions for Colloidal Synthesis
Mengwen Zhang 1 , Paula Malo de Molina 1 , Matthew Helgeson 1 Show Abstract
1 , University of California-Santa Barbara, Santa Barbara, California, United States
In recent years, complex emulsions – droplets with internal structure – have generated great research interest due to their potential applications in materials, foods, cosmetics, pharmaceuticals, and chemical separations. Microfluidic methods have already demonstrated the ability to create micron- and larger scale complex emulsions with breathtaking sophistication and control, as well as compartmentalize encapsulation of molecules within them. However, scaling the size of such droplets to the nanoscale has been extremely challenging due to limitations on the devices and energies required to produce nanoscale droplets, i.e. nanoemulsions. Here, we report the ability to fabricate complex nanoemulsions of various morphologies, and use them as templates for nanoparticle synthesis. To produce complex morphologies, we combine high-energy emulsification methods with co-surfactant pairs possessing highly asymmetric molecular geometry. The former aids the generation of nanoscale droplets, whereas the latter influences their morphology through ultra-low surface tension and control over frustrated spontaneous curvature, resulting in the reproducible generation of droplets with a range of controlled complex morphologies. The size, stability, internal morphology and chemical compartmentalization of these complex nanoemulsions have been quantified using a combination of scattering, optical microscopy and cryogenic-transmission electron microscopy techniques. We show that complex droplet morphologies are retained upon the addition of various material pre-cursors, and that the droplets are stable over the time scales required for material chemistry, thereby enabling their use as templates for complex nanoparticles.
11:00 AM - *BM02.07.02
Macromolecular Materials by Assembly at All-Aqueous Interfaces
Anderson Shum 1 2 Show Abstract
1 Mechanical Engineering, University of Hong Kong, Hong Kong Hong Kong, 2 , HKU-Shenzhen Institute of Research and Innovation, Shenzhen China
All-aqueous emulsions, which consist of aqueous droplets surrounded by an immiscible aqueous phase, have demonstrated great potential in applications, such as extraction of rare compounds. They are also increasingly used in biomimetics, as they allow compartmentalization and processing of bioactive species. However, it has been challenging to achieve all-aqueous emulsions with long term stability, due to the low interfacial tension commonly observed in these emulsions. In this talk, I will discuss our works in understanding the properties of these all-aqueous interfaces, the partitioning properties of which enable controlled partitioning-induced assembly of macromolecules, ranging from polyelectrolytes to proteins. In particular, I will demonstrate how the interplay between the all-aqueous interfaces and the macromolecular networks can result in surprising macroscopic behaviors of the all-aqueous droplets. Using these approaches, we also fabricate structures, including microgel particles, microcapsules, and fibrillosomes, whose bio-compatibility is superior to their counterparts fabricated based on an oil-containing emulsion. We will conclude the talk by discussing the disciplines, ranging from biotechnology, to nanotechnology, to bio-materials and to medicine, that will be benefited from the new approach of forming bio- and cyto-mimetic materials.
11:30 AM - BM02.07.03
Novel Encapsulation Systems for 1-Pot Industrial Formulations
Joshua Katz 1 , Xiaocun Lu 2 , Adam Schmitt 3 , Jun Li 1 , Jeffrey Moore 2 Show Abstract
1 , The Dow Chemical Company, Collegeville, Pennsylvania, United States, 2 Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 3 , The Dow Chemical Company, Midland, Michigan, United States
Encapsulation of actives comprises an area of exploration undergoing rapid growth in both academic and industrial research settings. Encapsulation processes are employed as a part of product synthesis processes for improved efficiency, enhanced stability, active ingredient compatibility, increased safety, targeted delivery, and novel performance of the end product. One area of particular interest for improving ingredient compatibility is in reactive systems, such as thermosets. Classically, thermoset systems are limited to being formulated in two parts, the combination of which induces the curing reaction, leading to short pot lives. In the interest of simplicity, formulations with extended pot lives when combined or stable shelf life are desired. With these needs in mind, Dow and the University of Illinois (UIUC) have collaborated for the past five years to develop new materials for improving the performance of thermoset systems. This talk will highlight some of the most exciting and recent advancements from this collaboration and the implications for their use in emerging industrial formulations.
11:45 AM - BM02.07.04
Creating Nanoscale Emulsions Using Condensation
Ingrid Guha 1 , Sushant Anand 2 , Kripa Varanasi 3 Show Abstract
1 Electrical Engineering & Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 , University of Illinois at Chicago, Chicago, Illinois, United States, 3 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Nanoscale emulsions provide essential formulations in numerous products, ranging from processed foods to novel drug delivery systems. Most methods of emulsification rely on top-down approaches, such as mechanical agitation of two separated phases or induced changes in chemical composition to trigger solvent exchange/inversion. Here we report a simple, bottom-up assembly method of creating nanoscale water-in-oil emulsions by condensing water vapor onto an oil solution containing surfactants. Nanoscale water droplets nucleate at the oil-air interface and spontaneously disperse within the oil due to the spreading dynamics of oil on water. The surfactant concentration in the oil phase controls the spreading behavior of the oil phase over the nucleated water droplets, as well as the size, polydispersity, and stability of the resulting emulsions. Using condensation, we form emulsions with peak radii as small as ~100 nm and polydispersities as low as ~10%. These emulsions remain stable over several months. This method of forming nanoscale emulsions may open new routes to create novel emulsions, colloidal systems, and emulsion-based materials.
BM02.08: Microfluidics III
Tuesday PM, November 28, 2017
Sheraton, 2nd Floor, Back Bay A
1:30 PM - *BM02.08.01
Microfluidic-Based Nanocrystal Synthesis—Towards Ultra-Fast Parametric Space Mapping
Andrew deMello 1 , Richard Maceiczyk 1 , Ioannis Lignos 2 , Maksym Kovalenko 1 Show Abstract
1 , ETH Zurich, Zurich Switzerland, 2 Department of Chemical Engineering, Massachusetts Institute of Technology, Boston, Massachusetts, United States
Recent years have seen considerable progress in the development of microfluidic systems for use in the chemical and biological sciences. At a primary level, interest in such systems has been stimulated by the fact that physical processes can be more easily controlled and harnessed when instrumental dimensions are reduced to the micron scale. For example, it is well recognized that when compared to macroscale instruments, microfluidic systems engender a number of distinct advantages with respect to speed, analytical throughput, reagent usage, process control and operational/configurational flexibility. Put simply, microfluidic systems define new operational paradigms and provide predictions about how molecular synthesis and analysis might be revolutionized.
Nanomaterials exhibit optical and electronic properties that depend on their size and shape, and are seen as tailored precursors for functional materials. These critical dependencies indicate that ‘bottom-up’ approaches for nanomaterial synthesis must provide for fine control of the physical dimensions of the final product. Synthetic routes have attracted significant interest owing to their versatility and ease of use, but for most applications deviations about the mean particle diameter must be <1%. This is beyond the tolerance of standard macroscale syntheses, and it is almost always necessary to post-treat to extract the desired particle size. Conversely, microfluidic systems provide an ideal medium for nanoparticle production. Since both mass and thermal transfer are rapid, temperatures may be defined with precision and reagents rapidly mixed to ensure homogeneous reaction environments.
I will describe how we have utilized microfluidic reactors for highly efficient nanomaterial synthesis. Specifically, I will present autonomous ‘black-box’ systems for the controlled synthesis of nanoparticles, such as CdSe, ZnS, ZnSe, CdSeTe and CuInS2/ZnS. Such platforms incorporate microfluidic reactors and real-time optical spectroscopy to monitor the properties of emergent particles. Acquired data is assayed (using control algorithms) to estimate “experimental success”, with the system intelligently updating reaction conditions in an effort to drive the system towards a desired goal. In this way ‘intelligent’ synthesis of nanoparticles of varying size, shape and size-distribution becomes possible. I will also discuss how droplets (formed spontaneously when multiple laminar streams of aqueous reagents are injected into an immiscible carrier fluid) can be used for the synthesis of high-quality nanomaterials on short timescales. Specifically, I will present the use of droplet-based microfluidics for the synthesis of Cesium Lead Halide Perovskite nanocrystals. The combination of online photoluminescence and absorption measurements and rapid reagent mixing allows the rapid mapping of the reaction parameters, including molar ratios of Cs, Pb and halide precursors, reaction temperatures and reaction times
2:00 PM - BM02.08.02
Reconfigurable Microfluidic Droplets Stabilized by Nanoparticle Surfactants
Anju Toor 1 , Brett Helms 1 , Thomas Russell 1 2 Show Abstract
1 , Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts, United States
Nanoparticle surfactants (NPS) consist of nanoparticles dispersed in one liquid phase and functionalized surface-active polymers (`ligands') dispersed in a second, immiscible liquid phase. Due to the complementary (e.g. acid-base) chemistry between the particles and ligands, they interact at the liquid-liquid interface and are bound to the interface, forming NPS monolayers that impart viscoelastic characteristics to the interface. NPS offer two keys advantages over the traditional surfactants, one is that these systems are versatile meaning that NPS can be formed regardless of the choice of nanoparticle material and geometry since the interfacial segregation relies on the interactions between the nanoparticles and polymer. Secondly, by controlling the strength of interactions between the polymer and the NPs, the assemblies of the NP-surfactants can be made responsive to external stimuli. NPS are promising materials for creating structured, liquid-bicontinuous systems that can be dynamically reconfigured by a large range of external stimuli.
Due to their stimuli-responsive nature, these self-assembled NPS assemblies hold significant potential for drug delivery applications. Self-assembled NPS monolayers at the interface between two liquids can stabilize microfluidic emulsions of one liquid in another. Current microfluidics based drug delivery techniques, rely on the encapsulation and on-demand release of the drugs from the microfluidic droplets. One of the major limitations of such methods is the cross-contamination among the droplets. For example, molecule retention has been a challenge in assays using fluorophore probes as their readout, since hydrophobic molecules partition out of droplets into the continuous phase. This is due to the dynamic nature of the organic surfactant molecules stabilizing the droplet. On contrary, these NPS are rigid in nature possessing high mechanical robustness.
In this contribution, the effect of the NPS formed by the electrostatic interactions between carboxylic acid treated nanoparticles (SiO2-COOH) dispersed in an aqueous phase, and amine-terminated polymer ligands dissolved in an oil phase, on the stability against coalescence for microfluidic emulsions is investigated. The self-assembly and the formation of the nanoparticle surfactants at the water−oil interface is studied using pendant drop tensiometry. We present results demonstrating that the water−oil interfacial tension undergoes a significant reduction, due to the formation of nanoparticle surfactants. An extensive series of droplet generation experiments for the water−oil systems with nanoparticle surfactants were performed, varying the fluids’ flow rates, nanoparticle material, polymer material, and the nanoparticle and polymer concentration. NP surfactants were found to significantly affect the stability of droplets resulting in robust water in oil microfluidic emulsions.
2:15 PM - BM02.08.03
Microfluidic Devices for Producing Millimeter-Size Droplets, Emulsions and Polystyrene Shells for Inertial Confinement Fusion Experiments
Nelia Viza 1 2 , David Harding 1 2 Show Abstract
1 Chemical Engineering, University of Rochester, Rochester, New York, United States, 2 , Laboratory for Laser Energetics, Rochester, New York, United States
Millimeter-size polymer shells made using coaxial flow devices are used to contain the fuel for inertial confinement fusion experiments.1 The process combines three immiscible fluids into a spherical double-emulsion droplet with a polymer (or reactive chemicals) in the middle fluid. The double emulsion is rotated and dried to form a shell (0.9 to 3 mm diam) with a uniformly thick wall (8 to 180 mm). Improvement to this process to better control the shells’ dimensions and polymer’s microstructure are desirable. The performance of three different microfluidic-device geometries for making these double emulsions is discussed.
The mechanisms for combining low- and high-molecular-weight fluids in T-junctions, double-cross junctions, and focus-flow devices into oil–water–oil and water–oil–water double emulsions were evaluated. (The fluids include oil, water, fluorobenzene, polystyrene, and styrene.) The devices possessed different dimensions: channel construction (rectangular versus circular cross section) and spacing between channels, and were made of different materials (acrylic, polyvinyl chloride, BK7 glass, Teflon, and fluorinated ethylene propylene). The effect of the fluids’ velocities and interfacial tension on the droplet and emulsion forming processes were summarized by the capillary number (Ca) and the relative volumetric flow rates (j).
Of the three channel designs evaluated, the focus-flow design performed the best: droplets formed over a wide range of fluid parameters (0.03 < j < 0.17 and 0.0003 < Ca < 0.001), while double emulsions formed over a more limited range (j > 0.5 and Ca < 0.4). The double emulsions produced polystyrene shells with an outer dimension ranging from 2.3±0.07 mm to 4.3±0.23 mm and a wall 30 mm and 160 mm thick. The volumetric flow-rate ratio was the most-sensitive parameter for controlling the shells’ dimensions.
1. R. Cook, Energy and Technology Review, Lawrence Livermore National Laboratory, Livermore, CA, Report UCRL-52000-95-4, 1–9 (1995).
2:30 PM - BM02.08.04
Surface-Chemical Patterns and Gradients for the Organization, Manipulation, and Processing of Liquid Precursor Droplets into Functional Materials
Karla Perez-Toralla 1 , John Bowen 1 , Abhiteja Konda 1 , Stephen Morin 1 Show Abstract
1 , University of Nebraska–Lincoln, Lincoln, Nebraska, United States
Synthetic surfaces with discrete patterns and distributions of surface functional groups (e.g., patterned self-assembled monolayers with differential wettability) have been applied to the spatial manipulation and patterning of liquid droplets; however, these investigations have been mainly limited to rigid, planar surfaces (e.g., silicon or glass). We are investigating the use of surface-functionalized elastomeric substrates as tools for the organization and manipulation of microscale liquid droplets. An advantage of this strategy, over those based on rigid substrates, was that both chemical properties and mechanical deformations could be used to control the droplets. Specifically, we chemically functionalized the surface of silicone films to yield periodic surface-chemical patterns and gradients that, when coupled with the ability to stretch and relax the films, enabled the generation of discrete patterns and the spatial manipulation of droplets of polar liquids (e.g., aqueous solutions or suspensions). We demonstrated that, through appropriate chemical post-processing, these droplets were readily transformed into functional materials (e.g., stimuli-responsive inorganic/organic microgels). This strategy is scalable to the fabrication of several million functional microstructures simultaneously. Furthermore, we used the ability to create predictable distributions/patterns of colloidal microdroplets for the assembly of nanoparticles onto 2D silicone substrates that were transferable to substrates with 3D geometries—a process enabled by the elasticity and low adhesion of silicone. We believe this approach will enable significant advances in the manipulation and organization of liquid precursors applicable to the fabrication of functional microstructures of compositional diversity with properties useful to numerous fields (e.g., sensing, cell biology, plasmonics, etc.).
2:45 PM - BM02.08.05
Controlled Crystallization of Calcium Carbonate in a Droplet Microfluidic Device Enabled by Passive Pico-Injection
Shunbo Li 1 , Shuheng Zhang 1 , Fiona Meldrum 1 Show Abstract
1 School of Chemistry, University of Leeds, Leeds United Kingdom
Droplet microfluidic devices offer an attractive means of studying crystallisation processes. However, while they have been widely employed for protein crystallisation, there are few examples of their use for sparingly-soluble compounds due to problems with rapid device fouling and irreproducibility over longer run-times. We here describe a novel microfluidic device which opens the door to studying the precipitation of insoluble crystals over extended periods of operation. Importantly, the chip design is sufficiently simple and easy-to-use that it can be employed by crystallisation research groups rather than specialist microfluidic labs. As demonstrated for the precipitation of calcium carbonate from highly supersaturated solutions, our device offers excellent reproducibility due to the elimination of non-specific crystallisation at, or prior to, droplet formation. Central to our strategy is the use of pico-injection to generate droplets of supersaturated solution, where this eliminates all problems of non-specific precipitation. This is achieved using a new design of pico-injector which employs a Venturi junction to reduce the pressure within the droplet at the point of injection, therefore enabling injection into surfactant-stabilised droplets. Further, precise control over the injection volume can be readily achieved by varying the flow rate in the injection capillary. We also demonstrate the importance of efficient mixing to the precipitation of insoluble compounds within droplets, where different calcium carbonate polymorphs were generated in devices that contained serpentine channels for efficient mixing as compared with linear channels. This work not only opens the door to the use of microfluidics to study the crystallisation of low solubility compounds, but the simple design of a passive pico-injector will find wide utility in areas including multi-step reactions and investigation of reaction dynamics.
BM02.09: Colloids IV
Tuesday PM, November 28, 2017
Sheraton, 2nd Floor, Back Bay A
3:30 PM - *BM02.09.01
Colloidal Cholesteric Liquid Crystals in Spherical Confinement
Eugenia Kumacheva 1 Show Abstract
1 , University of Toronto, Toronto, Ontario, Canada
The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. In particular, spherical confinement of nanocolloids yields new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. We exploerd the organization of the cholesteric liquid crystal formed by nanorod particles – cellulose nanocrystals (CNCs) - in spherical aqueous droplets. For cholesteric suspensions of CNCs , with progressive confinement, we observed confinement-induced structural transitions, that is, phase separation of the cholesteric phase into an isotropic droplet core and a cholesteric shell formed by concentric cholesteric layers. Further progressive confinement resulted in a transition to a bipolar planar cholesteric morphology of the droplets. We explore this effect for hybrid cholesteric CNC droplets laden with polymer, metal, carbon or metal oxide nanoparticles. We show that the distribution of the host nanoparticles in the droplets is governed by the elastic energy minimization and it can be controlled by the nanoparticle size. The resulting hybrid cholesteric droplets exhibit fluorescence, plasmonic properties and magnetic actuation. We also show that host nanoparticles can change the structure of teh host liquid crystal. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of hybrid soft matter.
4:00 PM -
4:15 PM - BM02.09.03
Glass Step Emulsification for the Production of Functional Materials
Alessandro Ofner 1 , David Moore 1 , Patrick Ruehs 1 , Maximilian Eggersdorfer 2 , Esther Amstad 3 , David Weitz 2 , Andre Studart 1 Show Abstract
1 Material Science, ETH Zürich, Zurich Switzerland, 2 , Harvard University, Cambridge, Massachusetts, United States, 3 , EPF Lausanne, Lausanne Switzerland
High-throughput production of monodisperse droplets is of importance for industrial applications due to increased emulsion stability, precise control over droplet volumes, and the formation of periodic arranged structures. So far, parallelized microfluidic devices are limited by either their complicated channel geometry or by their chemically or thermally unstable embedding material (1, 2). This study (3) shows a scalable microfluidic step emulsification chip that enables production of monodisperse emulsions at a throughput of up to 25 mL/h in a glass device with 364 linearly parallelized droplet makers. The chemical and thermal stability of such a glass device allows for the preparation of a broad variety of functional particles and microdroplets by using any desired solvent together with nanoparticles, polymers, and hydrogels. Moreover, the microfluidic device can be stringently cleaned for nearly unlimited use and permits the alternating production of oil-in-water and water-in-oil emulsions. The combined high throughput, chemical and thermal stability offered by our device enables production of monodisperse functional materials for large-scale applications.
(1) Eggersdorfer et al., Lab Chip, 2017, 17, 936
(2) Amstad et al., Lab Chip, 2016, 16, 4163
(3) Ofner et al., Macromol Chem Phys, 2016.
4:30 PM - BM02.09.04
Expanding the Use of Microemulsions—Synthesis of Hollow Nanospheres and Base Metal Nanoparticles
Claus Feldmann 1 Show Abstract
1 , Karlsruhe Institute of Technology (KIT), Karlsruhe Germany
Microemulsions (MEs) are ideal for obtaining high-quality inorganic nanoparticles and belong to the most widely applied techniques with about 5000 papers appearing each year. MEs are thermodynamically stable systems that contain a nanosized droplet phase serving as a nanoreactor . MEs, on the other hand, have specific restrictions that hamper the synthesis or even exclude inorganic materials from synthesis. Thus, nanoparticles with specific shape as well as hydrolysable/oxidizable compounds are typically excluded from ME-based synthesis. In this contribution, we show how to expand ME synthesis to nanoscale hollow spheres and base metal nanoparticles [1-5].
To obtain hollow nanospheres, the reactants are separately added to the polar droplet phase and to the non-polar dispersant phase. As a consequence, the reaction occurs only at the liquid-to-liquid phase boundary of the micellar system. With this background, it can be instantaneoulsly rationalized that the final diameter of the hollow sphere is in close relation to the micelle size. The resulting solid sphere wall naturally encapsulates the pristine water droplet as an inner cavity. Based on this strategy, we could prepare a wide range of hollow nanospheres (e.g., g-AlO(OH), La(OH)3, ZnO, Fe2O3, SnO2, TiO2, ZrO2, CuS, Cu1.8S, Cu2S, MgCO3, Gd2(CO3)3, Ag2S, Au, Ag) with outer diameters of 10–50 nm, a wall thickness of 2–10 nm and an inner cavity ranging from 5 to 30 nm in diameter [1-3]. We could also show the use for sensing (e.g. SnO2@Pd, Pd@SnO2), drug release (e.g., doxorubicine, isoniacid in AlO(OH) or Fe2O3 hollow nanospheres)  or for magnetothermal heating and magnetothermally induced drug release (e.g. with Gd2(CO3)3 hollow nanospheres) .
MEs with liquid ammonia as the polar droplet phase are shown for the first time . They are highly promising for both the synthesis of base metal nanoparticles (e.g., Bi0, Re0, W0, Fe0)  as well as for the synthesis of nitride nanoparticles (e.g., CoN, GaN, TiN, Si3N4) . All nanoparticles were obtained with diameters of 2-5 nm and specific surface areas up to 800 m2/g. Based on the knowhow on suitable concentrations and surfactants liquid-ammonia-in-oil MEs can be handled as easy as standard water-in-oil MEs, except for the need of low temperatures (-40 °C) for avoiding NH3 evaporation.
 S. Wolf, C. Feldmann, Angew. Chem. Int. Ed. 2016, 55, 15728 (Review).
 P. Leidinger, J. Treptow, K. Hagens, J. Eich, N. Zehethofer, D. Schwudke, W. Öhlmann, H. Lünsdorf, O. Goldmann, U. E. Schaible, K. E. J. Dittmar, C. Feldmann, Angew. Chem. Int. Ed. 2015, 54, 12597.
 J. Jung-König, M. Sanhaji, R. Popescu, C. Seidl, E. Zittel, U. Schepers, D. Gerthsen, I. Hilger, C. Feldmann, Nanoscale 2017, DOI:10.1039/c7nr01784g.
 F. Gyger, P. Bockstaller, D. Gerthsen, C. Feldmann, Angew. Chem. Int. Ed. 2013, 52, 12443.
 F. Gyger, P. Bockstaller, D. Gerthsen, C. Feldmann, Chem. Mater. 2016, 28, 7816.
4:45 PM - BM02.09.05
Influence of Substrate Chemistry, Morphology and Surface Energy on Crystalline Dessication Patterns
Samantha McBride 1 , Sami Khan 1 , Susmita Dash 1 , Kripa Varanasi 1 Show Abstract
1 , MIT, Cambridge, Massachusetts, United States
A particle or solute laden drop evaporating on a substrate will often leave behind a ring-like dessication pattern due to radial evaporative flow; termed the "coffee-ring effect." This seemingly simple phenomenon has been studied extensively, as disrupting the coffee ring effect allows for more precise control of deposition patterns in inkjet printing, microarray assembly, sensors, displays, and other applications. Previous investigations have shown that the coffee ring effect can be disrupted in particle-laden drops by using superhydrophobic surfaces or by using particles with a high aspect ratio. It is more difficult to avoid ring-patterns using solute-laden drops as many solutes will preferentially crystallize as the triple phase contact line between the evaporating solvent, the substrate, and the surrounding air. We explore the influence of substrate morphology, chemistry, and surface energy for evaporating drops of different salt solutions. Specifically, we use superhydrophobic micropost morphologies with different spacing between posts, superhydrophobic nano-cratered surfaces, and smooth hydrophobic surfaces. These same superhydrophobic surfaces were also used with an impregnating oil to eliminate pinning between the substrate and crystallizing solute. To explore the influence of surface chemistry, we use oxide coatings on smooth textures; including hydrophobic rare earth oxides. Water drops containing salts of different solubilities and surface energies were deposited onto these surfaces to explore the evaporation modes and resulting dessication patterns. Results from these experiments show that the contact angle controls evaporation speed and therefore size/shape of the crystals, that salt composition is important for surface selection, and that liquid impregnation can disrupt the coffee ring effect by eliminating substrate-crystal interactions. Finally, real world applications of these results will be discussed, including corrosion-resistant surfaces and micropatterning.
Paul Millett, University of Arkansas
Esther Amstad, Ecole Polytechnique Federale de Lausanne
Paul Clegg, University of Edinburgh
Daeyeon Lee, University of Pennsylvania
BM02.10: Colloids V
Wednesday AM, November 29, 2017
Sheraton, 2nd Floor, Back Bay A
8:00 AM - *BM02.10.01
Structure of Capillary Suspensions and Their Applications
Frank Bossler 1 , Irene Natalia 1 , Moritz Weiss 1 , Steffen Fischer 1 , Erin Koos 1 Show Abstract
1 , KU Leuven, Leuven Belgium
Ternary liquid-liquid-solid systems exhibit a wide variety of different morphologies depending on the ratio of the three components. With small amounts of secondary fluid, the characteristic mechanical strength of such capillary suspensions arises due to the capillary force inducing a percolating network of particles bridged by small individual droplets of secondary fluid . Spatial information on the structure of such particle networks can be obtained using 3D confocal microscopy on an index-matched model system and directly correlated to changes in the mechanical strength  or mixing conditions.
We investigate microstructural properties and transitions as the particle size, contact angle, and volume ratio of secondary fluid to particles, φsec/φsolid, is changed. A transition from a granular system without added liquid, through a sparser capillary suspension network at intermediate volume ratios, to a network of dense aggregates at larger ratios is observed. For intermediate volume ratios, a change from binary bridges to more complex funicular and clustered arrangements is observed when the volume ratio is increased or when the contact angle is modified. Computational analysis of 3D confocal images provides structural parameters like the coordination number, which lies around 4 when the particle network is fully established but, due to particle agglomeration, increases when more secondary liquid is added. The fractal dimension of the network increases with the particle size. This transition may be explained by the corresponding reduction in the capillary force with increasing particle size.
These capillary suspensions can be used in several different application pathways including in the formation of porous materials, printed electronics with high conductivity, and crack-free films. The particle network is able to be preserved either through sintering or direct polymerization of the bridges to create materials with a high open porosity (up to 80%) with a narrow, micrometer-sized pore distribution . We can use capillary suspensions to produce stable suspensions using conductive particles that have a twofold increase in conductivity over existing formulations using polymeric stabilization . Finally, the capillary force limits the direction of particle motion during film drying and the capillary force of the bridges counters the capillary force within pores generated by evaporation. Crack-free films can be produced at thicknesses much greater than the critical cracking thickness for a suspension without capillary interactions, and even persists after sintering .
 E. Koos, N. Willenbacher, Science, 2011, 331, 897.
 F. Bossler, E. Koos, Langmuir, 2016, 32(6), 1489.
 J. Dittmann, E. Koos, N. Willenbacher, J. Am. Ceram. Soc., 2013, 96(2), 391.
 M. Schneider, E. Koos, N. Willenbacher, Sci. Rep., 2016, 6, 31367.
 M. SchneiderACS Appl. Mater. Interfaces, 2017, 9(12), 11095.
8:30 AM - *BM02.10.02
Capillarity-Based Morphology Control of Particulate Materials
Sachin Velankar 1 Show Abstract
1 , University of Pittsburgh, Pittsburgh, Pennsylvania, United States
The colloids and rheology community has enormous knowledge about the structure and rheology of suspensions comprising particles dispersed in a liquid. Much less is known about suspensions composed of particles suspended in two immiscible fluids. In such cases, the ternary liquid/liquid/particle mixture can show a variety of microstructures: particles aggregated by fluid menisci, compact capillary aggregates, Pickering emulsions, and bicontinuous morphologies, many of which provide the basis for developing new materials.
These microstructures result from a coupling between interfacial tension between the fluids, particle wettability, and viscous forces during mixing. This talk will explore these issues in mixtures of particles with two immiscible polymeric liquids. Most of this talk will focus on systems in which particles are fully-wetted by one of the two fluids. We will catalog the transitions between various microstructures, and the corresponding changes in rheology, as composition is changed. Remarkably, capillarity is found both stabilize as well as destabilize three-phase microstructures, depending on the mixture composition. These studies culminate in a microstructural map of the morphologies of the mixtures across a wide range of composition space.
Comparisons of these polymeric systems with a diverse variety of mixtures from the literature – including air/water/particle mixtures – show strong parallels. This apparent universality indicates underlying features that are shared across all liquid/fluid/particle mixtures, and we will discuss a non-equilibrium state diagram for such ternary mixtures. Clear understanding of such a state diagram can guide new approaches for materials processing.
9:00 AM - BM02.10.03
Joining Emulsion Droplets Using Colloidal Rods
Paul Clegg 1 , Katherine Rumble 1 Show Abstract
1 , University of Edinburgh, Edinburgh United Kingdom
Many of the differences between conventional emulsions and particle-stabilized emulsions stem from the fact that the particles are mesoscopic objects. One curious difference is the phenomenon of bridging. This is where colloidal particles are shared by more than one droplet. It results in emulsions with clusters of droplets that are all attached and it has the effect of making the emulsions very fragile. Previous work in this area has focused on colloidal spheres. Here we explore the bridging behavior of droplets stabilized by colloidal rods. Our rods are spherocylinders which have an iron oxide core coated with a silica shell; in this work we use rods with aspect ratios 3 and 15. We find that bridging is ubiquitous for rod shaped particles, especially at high aspect ratio.
Previously, computer simulations have shown that the adsorption of colloidal rods to liquid interfaces is likely to involve two steps which happen sequentially. In the first step the rods are adsorbed to the interface; in the second step the rods reorient to lie with their long axis in the plane of the interface.
We suggest that extensive bridging occurs when droplets collide before the rods have had a chance to reorient. We show how it can be suppressed by varying the emulsification conditions to reduce early droplet-droplet collisions.
 French, D. J., Taylor, P., Fowler, J., & Clegg, P. S. (2015). Journal of Colloid and Interface Science, 441, 30.
 French, D. J., Brown, A. T., Schofield, A. B., Fowler, J., Taylor, P., & Clegg, P. S. (2016). Scientific Reports, 6, 31401.
 Günther, F., Frijters, S., & Harting, J. (2014). Soft Matter, 10, 4977.
9:15 AM - BM02.10.04
Shaking Colors—Bio-Inspired Melanin-Based Supraball Inks via Reverse Emulsion
Ming Xiao 1 , Ziying Hu 2 , Nathan Gianneschi 2 , Matthew Shawkey 3 , Ali Dhinojwala 1 Show Abstract
1 Department of Polymer Science, The University of Akron, Akron, Ohio, United States, 2 , University of California, San Diego, San Diego, California, United States, 3 , University of Ghent, Gent Belgium
Structural colors can potentially replace pigments in many applications, due to their advantages over conventional pigmentary colors, including remarkable color tunability, long-lasting resistance to photo/chemical bleaching, and reduced dependence on toxic metal oxides. However, challenges including dull, faint colors, iridescence, and difficulty in mass production remain. Nature provides inspiration to tackle these demanding questions. For example, some birds contain hollow melanosomes (sub-micron melanin-filled organelle) to increase refractive index (RI) contrast to achieve brighter feather colors. Inspired by this, we have synthesized core-shell synthetic melanin nanoparticles (CS-SMNPs, melanin core and silica shell) to achieve RI modulation and used a scalable one-pot reverse emulsion process to assemble CS-SMNPs supraball structures that produce colors across the visible range. The high absorption from the melanin core increases the color saturation and the core-shell morphology increases the color brightness based our finite-difference time-domain calculations. The colors of these supraballs are angle-independent and can be tuned by changing either the sizes of CS-SMNPs or the mixing ratios of binary sized CS-SMNPs. Our work paves the way for producing novel photonic inks, suitable for applications like painting, textiles, and display.
9:30 AM - BM02.10.05
Elasticity and Failure of Liquid Marbles—Influence of Particle Coating and Marble Volume
Abigail Rendos 1 , Nourin Alsharif 1 , Brian Kim 1 , Keith Brown 1 Show Abstract
1 , Boston University, Boston, Massachusetts, United States
When coated with microscale hydrophobic particles, macroscopic liquid droplets can become non- wetting liquid marbles that exhibit an array of fascinating solid-like properties. Specifically, the force required to uniaxially compress liquid marbles depends on their volume, but it is unclear if the particle coating plays a role. In contrast, the failure of marbles upon compression does depend on the particle coating, but the conditions for failure do not appear to change with marble volume. Here, we experimentally study the elastic deformation and failure of liquid marbles and, by applying a doubly truncated oblate spheroid model to quantify their surface area, explore the role of marble volume and particle composition. First, we find that the work required to compress liquid marbles agrees with the product of the core fluid surface tension and the change in the marble surface area, validating that the elastic mechanics of liquid marbles is independent of the particle coating. Next, we study marble failure by measuring their ductility as quantified by the maximum fractional increase in marble surface area prior to rupture. Not only does marble ductility depend on the particle coating, but it also depends on marble volume with smaller marbles being more ductile. This size effect is attributed to an interaction between marble curvature and particle rafts held together by interparticle forces. These results illuminate new avenues to tailor the rupture of liquid marbles for applications spanning smart fluid handling and pollution mitigation.
Citation:  A. Rendos, N. Alsharif, B. Kim, and K. Brown, Soft Matter, 2017, DOI: 10.1039/C7SM01676J.
9:45 AM - BM02.10.06
Monodisperse Shelled Bubbles of Graphene Oxide Nanosheets with Diverse Shapes
Seon Ju Yeo 1 , Min Jun Oh 2 , Yu Jin Jeong 2 , Daeyeon Lee 3 , Seok Joon Kwon 1 , Pil Jin Yoo 2 Show Abstract
1 , Korea Institute of Science and Technology, Seoul Korea (the Republic of), 2 , Sungkyunkwan University, Suwon Korea (the Republic of), 3 , University of Pennsylvania, Philadelphia, Pennsylvania, United States
Well-defined assemblies of graphene or graphene derivatives have been devised to create materials with improved physicochemical properties. However, methods for fabricating structured graphene assemblies are limited due to difficulties of time-consuming and low-yield processes. To challenge these issues, here, we present a microfluidic synthesis that uses solid bubbles of graphene oxide (GO) nanosheets with high size uniformity and outstanding stability. We employ alkyl functionalization of GO nanosheets to generate gas-in-oil-in-water (G/O/W) compound bubbles consisting of dispersed GOs. In particular, the assembling behavior of functionalized GOs in the middle oil phase strongly depends on their degree of alkylation, which offers an additional tunability over the shape of the resulting GO-shelled bubbles; these can be manipulated to be either perfectly spherical or non-spherical polyhedral in shape. In one hand, highly-alkylated GOs impart stable and homogeneous stacking conditions for shell formation, allowing for a generation of compound bubbles while retaining their spherical shape even after complete oil evaporation. One the other hand, lightly alkylated GOs are interrupted by shell inhomogeneity, and the bubbles undergo buckling deformations to form faceted polyhedral bubbles of GO, driven by the pressure difference. This shape-variant behavior of G/O/W compound bubbles is readily controlled by varying the mid-shell thickness and size of the bubbles, resulting in polyhedral bubbles with a variety of facets. The shell deformation of the bubbles is interpreted from both experimental and theoretical analyses supported by numerical calculations. Finally, we demonstrate the feasibility of harnessing GO-shelled bubbles as building blocks to create a new class of integrated graphene structures, which can offer outstanding stimuli-responsive properties for optical, electrical, or structural material applications.
10:30 AM - *BM02.10.07
Jasna Bruijc 1 Show Abstract
1 , New York University, New York, New York, United States
Traditionally, assembly lines to build machines, from electronic circuits to motor vehicles, follow specific instruction manuals, followed by robots or people. On the other hand, in biology, organisms self-assemble spontaneously according to instructions encoded in their genes - nonetheless following the laws of physics. Inspired by biology, we design and develop emulsions with specific DNA or protein-protein interactions that guide their spontaneous assembly into linear or branched freely-jointed polymers, with programmable sequences, capable of folding into complex 3D architectures. The droplets can readily be solidified, therefore they offer a route to hands-off manufacturing of objects with inbuilt hierarchy.
11:00 AM - *BM02.10.08
Optical Trapping of Colloids at a Liquid-Liquid Interface
Alessio Caciagli 1 , Mykolas Zupkauskas 1 , Jurji Kotar 1 , Darshana Joshi 1 , Erika Eiser 1 Show Abstract
1 Cavendish Laboratory, University of Cambridge, Cambridge United Kingdom
The study of the thermodynamic properties of colloids and (bio-)polymers at interfaces is of ongoing interest to both the colloid-science community and researchers studying binding properties on synthetic and bio-membranes. While many have investigated the aggregation behavior of colloids in Pickering emulsions or on lipid mono-and bilayer systems few have looked at colloids anchored to a liquid-liquid interface and their response to an external field.
In this talk I will introduce new ways to anchor single-stranded (ss)DNA oligomers either as single stickers of on polymer rafts to an oil-liquid interface such that we can anchor colloids holding complementary ssDNA to this interface . The DNA-anchor allows us to attach any type of colloids to these liquid-liquid interfaces reversibly; further we can also prepare a mixture of different ssDNA and thus allow different populations for colloids to be created at these fluid interfaces. Such anchored colloids can diffuse freely in the interface hence representing an ideal 2D-colloid system. After introducing various ways of producing DNA-functionalized oil-droplets (ODs) with sizes ranging from 200 nm to 100 μm, I will discuss the response of 0.5 μm large colloids anchored to 30 μm large ODs when trying to trap these particles with optical tweezers. The size of an optical trap is similar to the colloid diameter - therefore multiple particles can enter the same trap. This trapping results in multiple scattering between the particles themselves leading to the formation of 2D aggregates at solid-liquid interfaces and is known as optical binding . This aggregation is often irreversible (due to surface pinning).
In our system we show that reversible lateral optical binding of colloids in a single-beam configuration can be achieved . When we switch on our optical trap (focusing on the oil-water interface) we observe extended colloidal-colloid interactions only mediated by scattering and excluded volume effects. These lead to close-packing structures, which can be strengthened or relaxed upon adding additional inter-particle interactions (e.g. depletion). Using two traps we can then create two crystals next to each other, studying the evolving grain boundary.
 D. Joshi, D. Bargteil, A. Caciagli et al., Science Advances 2, 8 (2016)
 R. W. Bowman & M. J. Padgett, Reports on Progress in Physics 76, 2 (2013)
 A. Caciagli, D. Joshi and E. Eiser, arXiv:1703.08210v1 (2017)
11:30 AM - BM02.10.09
Controlled Single Cells Encapsulation and Assembly Using Multi-Compartment Microgels for Study of Cell-Cell Interaction
Liyuan Zhang 1 , Huanan Wang 2 , Changhyung Choi 1 , Angelo Mao 1 , David Mooney 1 , David Weitz 1 Show Abstract
1 , Harvard University, Cambridge, Massachusetts, United States, 2 Biomaterials and Tissue Engineering Laboratory, School of Life Science and Biotechnology, Dalian China
Controlled encapsulation and assembly of single cells within a confined three-dimensional (3D) matrix can enable the replication of the highly ordered cellular structure of human tissues. Microgels with independently controlled compartments that can encapsulate different types of cells within separately confined hydrogel matrix would provide further control over the assembly route. Here, we present a one-step microfluidic method to generate monodisperse multi-compartment microgels that can be used as a 3D matrix to assemble single cells in a highly biocompatible manner. We present a method to induce microgels formation on-chip, followed by direct extraction of the microgels from oil phase, thereby avoiding prolonged exposure of the microgels to the cytotoxic oil. We further demonstrate that by entrapping stem cells with niche cells within separate but adjacent compartments of the microgels, we can create complex stem cell niche microenvironments in a controlled manner, which can serve as a useful tool for the study of cell-cell interactions. This microfluidic technique represents a significant step towards high-throughput controlled cell encapsulation and assembly for the study of cell-cell interactions, which is of importance for cell biology, stem cell therapy and tissue engineering.
11:45 AM - BM02.10.10
Combinatorial Selection of Droplet Interfaces Generates Emulsions Protected by Mineral Shells
Lukmaan Bawazer 1 , Andrew deMello 2 , Fiona Meldrum 1 Show Abstract
1 School of Chemistry, University of Leeds, Leeds United Kingdom, 2 Department of Chemistry and Applied Biosciences, ETH Zürich, Zurich Switzerland
Droplet-based microfluidic systems have been used in a wide range of applications, including DNA amplification, biochemical diagnostics, high-throughput screening and polymer capsule production. However, the development of these systems for such varied applications remains challenging due to the requirement to identify unique oil/surfactant combinations that are compatible with the intended application and that support stable droplet formation and storage. In this work, we describe a novel strategy that couples combinatorial methods with a new droplet-based microfluidic screening platform to rapidly identify combinations of oils and surfactants that generate droplets optimised for specific functions. The potential of our strategy is demonstrated here by selecting a simple target property – enhanced droplet stability – where we take inspiration from biomineralisation processes to rapidly identify combinations of oil and surfactants that direct the formation of a mineral shell to stabilise the emulsions droplets. Libraries of over 100 oils and surfactants were screened for combinations that promote mineralisation at the interface of water-in-oil emulsions. This process was facilitated using a novel screening platform, which is operated by a simple vacuum manifold and which permits 24 droplet-generating microfluidic devices to be screened in parallel. As a key element of our method, we also show how genetic algorithms can be used to accelerate reaction discovery, where this approach is inspired by the diversification strategies observed in natural evolution. By evaluating the stability of the droplets generated from each library member, multiple rounds of genetic algorithm-guided evolution were conducted to efficiently identify the oil/surfactant combinations that promote droplet stability. Analysis of the “winning” droplets demonstrates that they exhibit a protective and biocompatible mineral/organic composite interface that reduces droplet merging and endows them with significant stability off-chip.
BM02.11: Colloids VI
Wednesday PM, November 29, 2017
Sheraton, 2nd Floor, Back Bay A
1:30 PM - *BM02.11.01
Anisotropic, Stimuli Responsive Endoskeletal Emulsions
Eric Furst 1 , Tamás Prileszky 1 Show Abstract
1 Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware, United States
The emulsions found in cosmetics, prepared foods, pharmaceuticals, agrochemicals, and other products provide a platform for mixing two immiscible liquids: one with chemical and physical properties for a target environment and the other capable of solubilizing an active ingredient. However, the spherical shape of emulsion droplets often limits their effectiveness as a delivery vehicle. We present an endoskeletal droplet formulation and production system for generating monodisperse oil emulsions of controllable anisotropic shape by incorporating a network of small crystallites that form a droplet-spanning elastic network. A microfluidic platform enables the rapid production of free droplets or superstructures assembled from droplets by tailoring their residence time and stability against partial coalescence. We demonstrate the capability of droplets to respond to their environment by increasing temperature to induce structural collapse as surface tension dominates over elasticity. In addition, the dispersal of ferromagnetic nanoparticles into the liquid phase of the droplets provides a new means of external control with magnetic fields. Depending on the type of field applied, static or alternating, droplets can be made to respond in a variety of ways, including directing their assembly and heating them by induction. Endoskeletal droplets provide novel routes to controlling the shape, stability, and dynamics of multifunctional emulsions, with promising applications for designing emulsions that can respond to the conditions of their environment to better deliver active ingredients to their target location.
2:00 PM - *BM02.11.02
Separation and Assembly of Colloidal Particles by Capillary, Magnetic and Electrostatic Forces
Jens Harting 1 Show Abstract
1 , Helmholtz Institute Erlangen-Nuremberg for Renewable Energy, Forschungzentrum Juelich, Nuremberg Germany
Colloidal particles are known to be very efficient stabilizers for fluid interfaces with applications in the food and cosmetics industry, enhanced oil recovery, drug delivery or waste water management. Capillary interactions between particles with different shape, contact angle on the particle surface, or particle-particle interactions are also promising candidates to self-assemble complex structures for the production of new soft materials or applications in the printing and coating industries. We present computer simulations based on a hybrid lattice Boltzmann and molecular dynamics method  and demonstrate the impact of the particle shape and its wettability on the detachment energy of a colloidal particle  and demonstrate new ways to self-assemble complex structures by means of capillary interactions and external magnetic fields to steer the movement of ellipsoidal particles [3,4]. We then introduce spherical magnetic Janus particles with a hydrophobic and a hydrophilic side and demonstrate that their capillary interactions can be tuned by a well-controlled external magnetic field [5,6]. At last, we introduce a new algorithm to simulate electrokinetic effects in multiphase flows and colloidal suspensions and demonstrate its ability with several benchmark examples.
 F. Jansen, J. Harting, “From Bijels to Pickering emulsions: a lattice Boltzmann study”,
Physical Review E 83, 046707 (2011)
 G. B. Davies, T. Krüger, P. V. Coveney, J. Harting, “Detachment energies of spheroidal
particles from fluid-fluid interfaces”, Journal of Chemical Physics 141, 154902 (2014)
 G. B. Davies, T. Krüger, P. V. Coveney, J. Harting, F. Bresme, “Interface deformations affect
the orientation transition of magnetic ellipsoidal particles adsorbed at fluid-fluid interfaces”,
Soft Matter 10, 6742 (2014)
 G. B. Davies, T. Krüger, P. V. Coveney, J. Harting, F. Bresme, “Assembling ellipsoidal particles
at fluid interfaces using switchable dipolar capillary interactions”, Advanced Materials 26, 6715
 Q. Xie, G. B. Davies, F. Günther, J. Harting, “Tunable dipolar capillary deformations for
magnetic Janus particles at fluid-fluid interfaces”, Soft Matter 11, 3581 (2015)
 Q. Xie, G. B. Davies, J. Harting, “Controlled capillary assembly of magnetic Janus particles at
fluid-fluid interfaces”, Soft Matter 12, 6566 (2016)
3:30 PM - *BM02.11.03
Capturing Anisotropic Surface Stresses and Particle Desorption with the Fipi Method—Simulating Complex Particle-Laden Fluid Interfaces on a Laptop
Lorenzo Botto 1 Show Abstract
1 School of Engineering and Materials Science, Queen Mary University of London, London United Kingdom
In Pickering emulsions, Bijels and particle-stabilised foams the stabilisation mechanism rests on the formation of a semi-solid skin, composed by one or more layers of particles, on the fluid-fluid interface . Understanding the link between the rheological properties of this skin and the surface particle microstructure is a key challenge of modern multiphase fluid materials science. In this talk we present FIPI , a new method for the fast simulation of particle-interface interaction problems involving bubbles, droplets and complex interfacial structures (e.g. bicontinous phases) interacting with particulate materials. The method enables to simulate a large (O(106)) number of particles in a reasonable time on a common PC, and reach the length scale separation and time scales of realistic experimental systems. The idea of the method is to fully resolve interfacial phenomena and hydrodynamics on scales larger than the particle, and model particle-level phenomena using physically-sound analytical or semi-empirical expressions. After describing the working principle of the method, I will illustrate the application of FIPI to two problems. One problem is that of a pendant drop covered by a monolayer of purely repulsive spherical particles. In this case, the simulations reveal the distribution of surface stresses in a fluid interface presenting complex, non-uniform curvature, providing insights into where surface stress anisotropy - and thus surface shear elasticity - is important, and how the surface stress evolves in time when the drop pinches off. A second problem is that of the shrinkage of a drop or a bubble covered with a particle monolayer. In this case we use FIPI to investigate the transition between surface buckling and particle desorption when the drop or bubble is shrunk in a quasi-static manner, and the surface pressure is increased beyond a critical buckling threshold. The numerical results reveal a complex dependence on 3 non-dimensional parameters, characterising the surface overpressure, the particle-interface adhesion strength, and the particle-to-drop size ratio. The simulations, which enables to track the dynamics of each single particle in the monolayer and capture microscopic phenomena, suggest that desorption and buckling may not be mutually exclusive, in contrast to what is often assumed based on macroscopic observations.
 Botto, L., Lewandowski, E. P., Cavallaro, M., & Stebe, K. J. (2012). Capillary interactions between anisotropic particles. Soft Matter, 8(39), 9957-9971.
 Gu, Chuan, and Lorenzo Botto. "Direct calculation of anisotropic surface stresses during deformation of a particle-covered drop." Soft matter 12.3 (2016): 705-716.
4:00 PM - BM02.11.04
Electrowetting Characterization of Droplet Interface Bilayers
Joyce Beyrouthy 1 , Eric Freeman 1 Show Abstract
1 , The University of Georgia, Athens, Georgia, United States
Droplet interface bilayers (DIB) allow for the creation of model cellular membranes at the interface of aqueous droplets dispersed in oil with dissolved phospholipids. Due to their amphiphilic properties, the lipids coat the droplets at their oil-water interfaces, stabilizing the droplets and forming biological thin films as the droplets are brought into contact. These systems allow for dynamic control of the droplets contact angle under an applied voltage, leading to in situ characterization of the interfacial tensions and membrane characteristics through the Berge-Lippmann-Young (BLY) equations. In addition to the membrane’s properties dependency on the oil-buffer-phospholipids combination, this work investigates the energetics of membrane deformation.
In this work, the monolayer tension of the oil-water interface with lipids is first measured using the pendant drop tensiometry, observing the deformation of a suspended droplet due to gravitational force and inferring the surface tension necessary to maintain its pendant shape. Next, microdroplets are suspended from silver/silver-chloride wires coated in agarose and brought in contact to form a lipid membrane at their intersection. The membrane capacitance is recorded through an alternating command voltage via electrophysiology, and the specific capacitance of the membrane is determined by combining the total membrane capacitance with a measured membrane area via microscopy. These measurements of the monolayer tension and specific capacitance provide the initial characterization of the DIB properties.
Once the initial characterization is completed, the energetics of the membrane under electrical loading is examined. When an additional DC voltage is supplied the membrane’s area increases – electrowetting – whereas its thickness decreases – electrocompression. These processes continue until a new stable configuration of the system is reached, corresponding to the new minimum energy of the droplet pair. This energy-per-area or tension is compared to the BLY theory for electrowetting, and additional terms are proposed to capture the mechanics of membrane deformation.
4:15 PM - BM02.11.05
Scaling Electrowetting with Printed Circuit Boards for Large Area Droplet Manipulation and Digital Millifluidics
Udayan Umapathi 2 , Rui Qing 1 2 Show Abstract
2 Media Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 1 Center for bits and atoms, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Recently, droplet based microfluidics (digital microfluidics) with Electrowetting on dielectric (EWOD) has gained popularity with the promise of being technology for a true lab-on-chip device with applications spanning across assays/library prep, next-gen sequencing and point-of-care diagnostics. Most electrowetting device architecture are linear electrode arrays with a shared path for droplets, imposing serious limitations -- cross contamination and limited number of parallel operations. Our work is in addressing these issues through 2D grid arrays with direct addressability providing arbitrary programmability. We also show how such large arrays can motivate applications beyond biology.
Scaling electrowetting to larger arrays still remains a challenge due to complex and expensive cleanroom fabrication of microlfuidic devices. We take the approach of using inexpensive PCB manufacturing and investigate challenges and solutions for scaling electrowetting to large area droplet manipulation. PCB manufactured electrowetting arrays impose many challenges due to the irregularities from process and materials used. These challenges generally relate to preparing the surface that interfaces with droplets -- a dielectric material on the electrodes and the top most hydrophobic coating that interfaces with the droplets. A requirement for robust droplet manipulation with EWOD is thin (<10um), uniformly flat dielectric which does not break down at droplet actuation voltages (DC, 60V to 300V). For this, we engineered a hydrophobic dielectric films specifically for PCBs -- a porous membrane filled with liquid. Our paper and presentation will go in to details about the process and materials used. Our work also demonstrates a new droplet sensing architecture (capacitive) performed simultaneously with large area actuation.
Traditionally, digital microfluidic devices sandwich droplets between two plates and hence limiting the volume of droplets that can be manipulated. In our approach we droplets are on an open surface with which we are able to manipulate droplets in microliter to milliliter volumes. For the first time we demonstrate the possibility of "digital millifluidics” on electrowetting devices. Finally, to motivate the need for large open arrays we show examples of running multiple parallel biological experiments, interactive displays with droplets and color mixing for painting.
4:30 PM - BM02.11.06
Microcapsules with Ordered Nanoporous Shells from Block Copolymer Self-Assembly in Double Emulsion Drops
Joerg Werner 1 , Hyomin Lee 1 , Ulrich Wiesner 2 , David Weitz 1 Show Abstract
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 2 Materials Science and Engineering, Cornell University, Ithaca, New York, United States
Encapsulation enables the storage and transportation of actives in hostile environments enabling the use of sensitive actives in a wider range of application sites. Microcapsules, particles with thin shells and large hollow cores, are particularly interesting because only small amounts of encapsulant is needed for protecting large amounts of cargo. Encapsulation systems traditionally use sacrificial encapsulants in a one-time, one-way encapsulate and release design. We are developing novel microcapsules with shell materials capable of stimulated reversible property changes for cargo release without shell destruction, leaving the capsule intact for reuse or repeated on-off switching of the release. Here we report the combination of the microfluidic fabrication of microcapsules from double emulsion drops with the nanoscale self-assembly of amphiphilic block copolymers. The co-assembly of amphiphilic block copolymers with removable small molecule additives inside the oil phase of the water-in-oil-in-water double emulsion droplets is demonstrated. The obtained microcapsules with controllable diameters of 10s to 100s of microns exhibit thin polymeric shells with ordered nanostructures and well-defined nanopores with pore sizes in the 10s of nanometers. Self-assembled nanoporous morphologies include three-dimensionally ordered, bicontinuous gyroid networks, and one-dimensional hexagonally packed cylinders. The walls of these nanopores are lined with a pH-responsive polymer block, rendering the nanoporous microcapsules reversibly responsive to external stimuli for repeated triggered release and uptake of cargo with nanometer-scale selectivity. The challenges in using amphiphilic block copolymers in water-in-oil-in-water double emulsions are also discussed.
4:45 PM - BM02.11.07
Dynamic Liquid Colloids for Sensor Applications
Lukas Zeininger 1 , Timothy Swager 1 Show Abstract
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Multiphase complex emulsions formed from two or more immiscible solvents offer a unique platform as new materials for chemical sensor applications. The temperature controlled miscibility of fluorocarbons (F) and hydrocarbons (H) enables a temperature induced phase-separation, leading to structured emulsion droplets of H and F in water (W), which can be alternated between encapsulated (F in H, and H in F), and Janus configurations by varying the interfacial tensions using surfactants. These complex emulsion droplets can selectively invert morphology in response to external stimuli such as the presence of specific analytes, small pH changes, light or high energy irradiation, and the presence of an electric or magnetic field. Here we will show how the addition of emissive dyes to one of the two immiscible phases of the complex emulsions provides a method to create a ratiometric optical read-out of such a morphology change. The potential of the microcolloids to manipulate light in form of waveguides further leads to the development of new optical transduction methods, where an adjustment of the refractive indices of the solvents results in a new unprecedented control of light propagation inside the emulsion droplets. While light trapped inside a glass waveguide in a certain angle is totally internally reflected at a glass-low refractive index media interface (air, water, fluorocarbon) an out-coupling of light from a glass slide can be realized if a higher refractive index solvent (hydrocarbon) is proximate to the interface. Using this scheme, slight morphology changes (e.g. from F in H to Janus) are readily detectable. Similarly, the liquid colloid particles can further be employed for detection of droplet agglutination. In both cases, our results show, that having control over the total internal reflection of light inside droplets creates a platform for using dynamic liquid colloids for the quantification of analytes for sensor applications.