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An atom is cooled by a standing-wave light field between two high-quality mirrors. Cavity cooling avoids the usual light scatter into the surroundings. Instead, the light leaking out of the mirrors is blue-shifted to a higher frequency (image credit: Pepijn Pinkse Max Planck Institute of Quantum Optics)
Artist's impression of an atom cooling device
NECF Meeting Abstracts


77th New England Complex Fluids Meeting
Harvard University | Friday, November 30, 2018
Registration deadline: Wednesday, November 28, 2018
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Abstracts for Invited Talks and Sound Bites:

Invited Talks

1. Carroll, Nick; Nick Carroll

University of New Mexico
"Programming assemblies of phase-separated polypeptide liquid"
Aqueous multi-phase systems comprising immiscible biopolymer solutions are ubiquitous in biological cells. However, the structure-to-function relationship and the physics describing the behavior of these polymer systems are, in general, not well understood. For example, almost all proteins have a specific three-dimensional structure that maintains its specific activity in the cell. One class of phase separating proteins, which has flown under the radar for decades, do not. They are referred to as intrinsically disordered proteins (IDPs). Their role in the cell appears to be to spontaneously associate with other proteins in phase separated compartments to activate them collectively. This is an important function to include in the design of a synthetic cell and for integration with cellular regulatory systems. Our work explores how we can leverage the blue print provided by the cell to engineer biological systems comprising phase-separated liquids with applications spanning areas of tissue culture, gene delivery, microfluidic colloid synthesis and engineered synthetic cells. Potential advancements include understanding how these interactions affect the regulation of gene expression and cell metabolism, understanding how dysfunctional interactions are linked to neurodegenerative disorders, and the design of synthetic cellular systems to create membraneless organelles to control a variety of biological processes at the molecular level.
Keywords: 

2. Halsey, Thomas C.; Thomas C. Halsey

ExxonMobil
"Erosion of unconsolidated beds by turbidity currents"
TBD
Keywords: 

3. Invited; Sarah Codd

Montana State University
"Magnetic Resonance of Complex Fluids - RheoNMR and dynamics of polymer-solvent phase transitions"
The dissipative, heterogeneous and non-equilibrium nature of the microscale dynamics in most soft matter systems impact the macroscale material response. The role of NMR relaxation, diffusion and imaging in the study of soft matter systems will be overviewed with emphasis on rheological responses of micellar polymer solutions and solvent dynamics in a weak gel of a concentrated polymer-solvent system.

RheoNMR allows Couette cells to be placed inside the NMR spectrometer and MRI velocity maps quantify the local spatial shear rate response to an imposed stress. The memory effect in wormlike micelles subject to different preshear measurement history are demonstrated and fluctuations during start-up are resolved with time resolutions on the order of seconds. Using large angle oscillatory shear, data on a range of fluids from Newtonian to yield-stress have been acquired to demonstrate the potential of LAOS RheoNMR. The data provides the velocity across the gap of the Couette cell as a function of the oscillatory shear. Interpretation of the data in the context of LAOS shear stress-shear rate correlations could provide novel insight into material response. Phase transitions during solvent evaporation drying of biopolymer solutions (e.g. HPMC) are important in food science and pharmaceutical production processes. NMR relaxation and diffusion measurements can characterize the structure of glassy polymer solutions and gels and provide insight into the transport processes within these systems and study the molecular dynamics of phase transitions during the solvent evaporative drying process.
Keywords: 

4. McKinley, Gareth; M. Geri, B. Keshavarz, T. Divoux, C. Clasen, and D. Curtis

MIT
"Optimal Fourier Transform Rheology for Probing the Linear Viscoelasticity of Gels and Time-Evolving Soft Materials"
Numerous approaches have been proposed for developing time-resolved oscillatory rheometric protocols that can provide both time- and frequency-resolved measurements on an aging, curing, drying or crosslinking gel system. Previous approaches include multiwave techniques, random/white noise sequences, short-time Fourier transforms, and repeated step strain pulses. Here we revisit an audio signal processing sequence known as the exponential chirp, which offers a number of benefits including a frequency-independent amplitude and a continuously-varying phase. This sequence enables the linear viscoelastic properties of a "mutating" (or time-evolving) gel to be rapidly determined over several decades in frequency in ~30-100s, and has been claimed to be an "optimal" Fourier transform sequence. However, closer investigation of high-resolution calibration data on a model polymer network shows that regardless of choice of the time-frequency bandwidth parameter, measurement precision can be severely compromised at the highest and lowest frequencies by "leakage" of material information into side-lobes of the chirp power spectrum. Taking inspiration from the chirp sequences used by bats in echolocation, we illustrate how these inaccuracies can be resolved through convolution of the chirp sequence with a carefully-chosen windowing function or envelope. The resulting waveforms can be readily encoded and then used to drive a controlled-strain rheometer. Numerical computations and experimental measurements show that the error magnitude can, in fact, be reduced exponentially with correct selection of the window parameters plus implementation of careful signal conditioning protocols. We present experimental measurements on a semi-dilute entangled polymer solution, a worm-like micellar fluid and a time-evolving cross-linked biopolymer gel, to show that the resulting Optimally-Windowed Chirp (or OWCh!) can indeed rapidly and accurately extract the entire linear viscoelastic spectrum of a time-evolving complex material in less than 15s, the time typically required to obtain the complex modulus at a single low frequency.

Keywords: 

5. Shum, Ho Cheung (Anderson)

Hong Kong University
"Assembly at aqueous-aqueous interfaces"
Liquid-liquid interfaces have been shown as versatile substrates to form material structures. Aqueous-aqueous liquid interfaces, which are characterized by tunable properties, such as interfacial tension and affinity partitioning, have inspired new opportunities to assemble particles, macromolecules and biological cells. In this talk, I will share our works in assembling material structures with unconventional properties at these interfaces.
Keywords: 


Sound Bites

1.

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Keywords: 

2.

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Keywords: 

3. Aime, Stefano

"Impact of interfacial rheology on two-phase flow in porous media"
Two-phase flow in porous media is a fascinating open problem, with huge implications in many fields, including oil recovery. Despite the efforts of an ever-increasing scientific community, its complexity keeps challenging our understanding, while its industrial relevance calls for practical guidelines to improve the economic, social and environmental impact of current oil extraction techniques. Among the many challenges faced by experimental as well as numerical approaches, one is certainly the complex rheological properties of interface of crude oil with the displacing fluid, which are highly simplified in current models relying on the existence of well-defined (constant) viscosities and contact angles. While there is some ongoing effort to extend current models to take bulk viscoelasticity into account, to the best of our knowledge no attempt has been done to account for nontrivial rheological properties of the water/oil interface. Our preliminary experimental data demonstrate that, unlike most model oils used in benchtop experiments, crude oil does exhibit interesting interfacial rheology, which should be taken into account by models aiming at a quantitative description of crude oil recovery.
Keywords: 

4. Brouchon, Julie; Julie Brouchon, Yuan Yuan, Perry Ellis, Xu Zhang, John Heyman, Jaime M. Calvo-Calle, David A. Weitz

Harvard university
"Microfluidics for high-throughput single-cell analysis of immune cells"
Isolation of antigen-specific T cells is fundamental to study autoimmune diseases and to develop immunotherapies. Unfortunately, these cells are rare and cannot be easily identified by surface markers. We overcome these challenges by compartmentalizing cells into microfluidic droplets and performing a functional assay relying on T cell-target cell interaction and subsequent fluorescent detection of cytokine secretion. In one day we can screen several million cells to isolate live, antigen-specific T cells.
Keywords: 

5. Cochard, Thomas

Harvard University, Weitz lab
"Hydraulic fracturing dynamics in natural and artificial low-permeability porous media"
Despite the impact that hydraulic fracturing has on the energy sector, the physical mechanisms that control its efficiency and environmental impacts remain poorly understood in part because of the complex heterogeneous structures of the natural low permeability formations. We developed an experimental approach to study the hydraulic fracture propagation in both natural and model low-permeability media. Natural shale sample, thin sections of Mancos Shale, and engineered gels have been hydro-fractured under controlled conditions. The combination of high-speed imaging during the process and X-ray tomography before and after allows us to monitor the fracture propagation and gives insight on how heterogeneities drive hydraulic fracturing dynamics.
Keywords: Hydraulic fracking, porous media, heterogeneity

6. Dillavou, Sam; Shmuel Rubinstein, John Kolinski

Harvard University
"Virtual Frame Technique: Ultrafast Imaging with Any Camera"
Many phenomena of interest in nature and industry occur rapidly and are difficult and cost-prohibitive to visualize properly without specialized cameras. The Virtual Frame Technique (VFT), is a simple, useful, and accessible form of compressed sensing that increases the frame acquisition rate of any camera by several orders of magnitude by leveraging its dynamic range. VFT is a powerful tool for capturing rapid phenomenon where the dynamics facilitate a transition between two states, and are thus binary. We have used the VFT on a variety of processes including fracture, liquid, and solid, and biological interaction with a hard surface, and tape peeling. The performance of the VFT - even with a 'slow' camera - exceeds that of any commercial high speed camera not only in rate of imaging but also in field of view, for example, videos at 65MHz with 4MPx resolution. In principle, modern cell phones can achieve imaging rates of over a million frames per second using the VFT.
Keywords: high-speed imaging, technique, rapid phenomena, impact, fracture

7. Ellis, Perry; Giridhar Anand, David A. Weitz, Sharad Ramanathan

Harvard University
"Identifying pathogenic bacteria by phenotyping individual cells"
While estimates give the number of bacterial species on this earth to be greater than 10^10, we have currently cataloged fewer than 10^7. Of all the species we have cataloged, only 10^3 are pathogenic. As even a single pathogenic bacterium can colonize humans and cause disease, identifying pathogenic bacteria in natural sample has important consequences for human health. We work to address this problem using high-throughput methods. Our goal is to identify even a single pathogenic bacterium in a collection of 10^6 bacteria obtained from a natural sample. Our current approach relies on droplet microfluidics: we co-encapsulate human tissue with the bacteria of interest, forming a functional assay capable of screening 10^6 bacteria per day.
Keywords: 

8. Filippov, Sergey; Leonid I. Kaberov, Bart Verbraeken, Anna Riabtseva, Richard Hoogenboom

Harvard University, SEAS
"Fluorophilic-lipophilic-hydrophilic poly-2-oxazolines block copolymers as MRI contrast agents: from synthesis to self-assembly"
This work focused on the synthesis and self-assembly of triphilic poly(2-oxazoline) triblock copolymers with high fluorine content towards our future aim of developing poly(2-oxazoline) MRI contrast agents. A highly fluorinated 2-substituted-2-oxazoline monomer, namely 2-(1H,1H,2H,2H-perfluorooctyl)-2-oxazoline was synthesized using the Grignard reaction. The polymerization kinetics of the synthesized monomer was studied and it was used for the preparation of triblock copolymers with hydrophilic 2-methyl-2-oxazoline, hydrophobic 2-octyl-2-oxazoline and fluorophilic blocks by Cationic Ring-Opening Polymerization yielding polymer with low relatively dispersity (1.2-1.4). The presence of the blocks with the different nature in one copolymer structure facilitated self-assembly of the copolymers in water and dimethylsulfoxide as observed by dynamic light scattering, cryotransmition electron microscopy, and small-angle neutron scattering. The nanoparticle morphology is strongly influenced by the order and length of each block and the nature of solvent, leading to nanoparticles with core-shell structure as confirmed by small angle neutron scattering. The reported poly(2-oxazoline) block copolymers with high fluorine content have high potential for future development of MRI contrast agents.
Keywords: poly(2-oxazoline)s, fluorine, self-assembly, DLS, SANS, Cryo-TEM, MRI

9. Green, Yoav

Harvard T.H. Chan School of Public Health
"Current rectification in nanochannel systems"
Permselective nanochannels can rectify the electric current transported through them similar to solid-state diodes. The rectification is due to symmetry breaking related to distribution of the nanochannels surface charge as well the geometry. Here, I will explain what is the origin of the current rectification and review the numerous ways to rectify the current.
Keywords: Nanochannels, electrokinetics flows, concentration polarization

10. Guzman, Edward; A. Green, N. Clark, D. Walba

University of Colorado, Boulder
"Nano-phase Segregating Groups in Bent-Core SmAP Mesogens"
Since the rediscovery of bent-core liquid crystals and “Banana-mania” in the late 1990s and early 2000s, the interplay between chirality and polarity in smectic liquid crystals has been re-evaluated. In 2011, the first reported achiral orthogonal polar liquid crystal phase, the SmAPf, was reported by the Walba and Clark groups in the bent-core mesogen W586 [1]. Two key molecular design principles to induce the phase were the inclusion of only one “tail,” and the addition of a linear tricarbosilane moiety at the tail terminus, a combination that was expected to favor the formation of an orthogonal ferroelectric phase. A variety of derivatives and homologs of W586 were synthesized since to study the structure-property relationships of the phase. Prior to the start of this project the effects of the nano-phase segregating group have on SmAP phase properties had not been investigated, motivating studies of the structural features responsible for the formation of ferro or antiferroelectric SmAP phases. A series of SmAP mesogens with different carbosilane moieties have been synthesized and studied to probe the role nano-phase segregating groups have on phase formation and phase properties. [1] R. A. Reddy, C. Zhu, R. Shao, E. Korblova, T. Gong, Y. Shen, E. Garcia, M. A. Glaser, J. E. Maclennan, D. M. Walba, and N. A. Clark, Science 332, 72- 77(2011).
Keywords: Liquid Crystals, Ferroelectric, Antiferroelectric

11. Haney, Bobby Tyrell; Joerg Werner, David A. Weitz, Subramanian Ramakrishnan

Florida A&M University, Harvard University
"Stable Pickering Emulsions Using Amphiphilic Microgel Particles via Microfluidics "
Pickering emulsions are important in systems where controlled confinement of an oil or water phase is needed. For example, micro-capsules incased by particles can serve as rigid vehicles for drugs or precious food ingredients. These coated emulsions can harbor oils in water or even water in oils. Nonetheless, the stability of the Pickering emulsions depend on the wetting properties of the particle. Amphiphilic, “Janus”, particles with two distinct surface chemistries are ideal for stabilizing emulsions due to the ability to tune wetting properties by changing the chemistry. Microfluidic techniques are used to create Janus particles to form stable water in oil as well as oil in water Pickering emulsions. These particles are composed of polyethylene glycol hydrogel as the hydrophilic side and polypropylene glycol as the hydrophobic side. The hydrogel and hydrophobic polymer’s abilities to respectively absorb the water and oil in an emulsion system enable the particles stronger attachment to the oil-water interface. The flowrates in a glass capillary device are varied to demonstrate complete control over particle sizes and hydrophilic to hydrophobic domain ratios. Using UV light, these droplets are cross-linked via photo-polymerization to form monodispersed particles. By manipulating the inner-phase flowrate, larger sized particles are fabricated which give larger stable emulsions. By adjusting the ratio of inner-phase hydrophilic fluid to hydrophobic fluid, the sizes of the two individual sections of the Janus particle are controlled. Emulsion stability is tested via centrifugation. Use of these larger particles to stabilize the emulsions allows direct visual observation, which lead to better understanding of how factors such as the particle orientations at the L-L interface affect Pickering emulsion stability.
Keywords: Pickering Emulsion, Hydrogel, Microfluidics, Amphiphilic

12. Ionkin, Nikolay P; Daniel Harris

Brown University
"A versatile 3D-printed droplet-on-demand generator"
There is a rapid and persistent growth in the study of dynamical behavior of droplets, however, the precise generation of these droplets over a range of sizes can be challenging. A versatile 3D- printed droplet-on-demand generator is presented for laboratory use. The design is modeled off of an existing design [Harris et al., Experiments in Fluids, 56:83 (2015)] but is tested with an extended range of working fluids and the manufacturing process is greatly simplified by 3D-printing the principal components. The present device is tested with deionized water and water-glycerol mixtures, and was reliably able to produce single droplets-on-demand of diameters 0.65-1.32 mm with an overall variability of less than 1%.
Keywords: Drops, Droplet-on-demand, Piezoelectric, Rapid prototyping

13. Jiang, Nan; Guoliang Ying, Yu Shrike Zhang*

Harvard University
"Three-dimensional (3D) Bioprinted Porous Hydrogels by Using Aqueous Two-Phase Emulsion Bioink"
The 3D bioprinting technology has been unprecedentedly progressed during the past decades in the field of regenerative medicine and disease modeling. By using programmable and customizable platforms, the 3D bioprinting technology enables engineered cell-laden constructs in a spatial-controllable manner. However, the conventional 3D encapsulated cells are always restricted in spreading and proliferation by the dense hydrogels. In this talk, we will introduce a novel approach to construct a 3D bioprinted porous cell-laden hydrogel by using a newly developed bioink. The bioink is consist of two aqueous phases, namely cell-laden gelatin methacryloyl (GelMA) solution and poly(ethylene oxide) (PEO) solution. The interconnected micropores within the 3D bioprinted cell-laden constructs were formed by photocrosslinking and subsequent PEO removal process. Both of extrusion bioprinting or digital micromirror device-based stereolithographic bioprinting allow for patterned cell-laden hydrogel constructs with high cell viability, spreading and proliferation. This new 3D bioprinting technique offers a robust and versatile platform to modeling human tissues.
Keywords: Aqueous two-phase emulsion, 3D bioprinting, bioink, porous hydrogel, gelatin methacryloyl (GelMA), tissue engineering

14. Kim, Seongsoo; Dohyun Kim, Jongwoo Kim, Sangmin An, Wonho Jhe

Harvard University
"Experimental verification of the curvature dependent surface tension in nanoscale"
Surface tension plays crucial role in diverse fields of science such as microfluidics, granular media and colloidal science. Despite its importance, physical understanding of the surface tension at molecular scale is still in open question. In 1948, Tolman predicted that pure water droplet would have lower surface tension than the bulk value when its radius of curvature gets down to few nanometers. However, its direct experimental verification was lacked due to the difficulty of observing single nanometer-size droplet. Here, we overcome this limitation by capturing the first moment of phase transition. We use quartz tuning fork-based atomic force microscopy and measure the critical distance at which single meniscus is condensed between two hydrophilic surfaces. By having statistical analysis of the critical distance at different humidity, we measured a slight deviation from the classical nucleation theory described as the Kelvin equation and found the deviation can be accounted by the curvature dependent surface tension. We experimentally determined the Tolman length, an important parameter for curvature dependent surface tension. Our results may provide deep understanding of the molecular mechanism of the surface tension and its effect on general nucleation phenomena.
Keywords: surface tension, curvature effect, nucleation, liquid-vapor phase transition

15. Lima, Nicolle; Shima Parsa, Marcio Carvalho

"Foam formation during drainage of a surfactant solution by gas injection"
Foam can be used in enhanced oil recovery to maximize oil production and solve problems caused by either a thief zone or gravity override. The presence of liquid lamellae between gas bubbles in the foam reduces the gas mobility; the resistance imposed by drag on moving lamellae resembles a shear-thinning viscosity behavior and leads to a more stable oil displacement flow. The flow mobility is a function of the pore geometry and foam properties. Foams can be injected in the reservoir or produced in-situ in the gas-liquid flow through the pore space. The goal of this research is to study foam formation during drainage of a two- dimensional porous media glass model by visualizing the pore scale displacement flow of a surfactant solution by injected gas. Image processing is used to study the evolution of the phase distribution and foam characteristics as a function of pore space geometry and flow conditions.
Keywords: foam, surfactant, porous media, EOR

16. McKeown, Ryan; Rodolfo Ostilla-Monico, Alain Pumir, Michael Brenner, Shmuel Rubinstein

Harvard University
"From Rings to Smoke: Visualizing the Breakdown of Colliding Vortex Rings "
The turbulent cascade, or the means by which the energy of a flow is conveyed from large to small scales, is governed by the interactions between vortices over many scales. In order to better understand the mechanisms that govern the close-range interactions between vortices, we experimentally examine the head-on collision of two vortex rings. By seeding the vortex rings with fluorescent dye and imaging their collision with a high-speed scanning laser sheet, we visualize the breakdown dynamics of the flow in full 3D. For weak collisions at low Reynolds numbers, the colliding rings stretch radially, develop long-wavelength perturbations, and reconnect into a tiara of secondary vortex rings. Conversely, for violent collisions at high Reynolds numbers, the rings rapidly develop short-wavelength perturbations as they stretch radially before erupting into a turbulent cloud of fine-scale vortex filaments. Initiated by these instabilities, the colliding vortices break down through various distinct processes and lead to the generation of small-scale flow structures. Thus, the close-range interactions of the colliding vortices could provide new insights into the mechanistic underpinnings of the turbulent cascade.
Keywords: Vortex Rings, Vortex Dynamics, Turbulence

17. Parsa, Shima; David Weitz

Harvard University
"Emulsions in porous media"
We measure the cooperative dynamics of mono-disperse emulsion droplets in porous media. Using particle tracking and confocal microscopy we track each drop and its impact on the surrounding pores and eventually long-range correlation between pores.
Keywords: Emulsion, Porous media

18. Sintes, Guillaume; Philippe Bourrianne, Irmgard Bischofberger

MIT
"Drying of colloidal droplets: the influence of particle concentration"
The interplay between the microscopic transport of particles and macroscopic mechanical instabilities occurring during the evaporation of a colloidal suspension leads to a rich variety of final deposit patterns. At low volume fraction of colloids, the pinning of the contact line induces the well-known coffee-stain effect. At higher volume fraction, the contact line is no longer pinned, which leads to a more homogeneous particle deposition and to the formation of radial cracks. We investigate the transition between these two regimes over a large range of volume fractions and show the emergence of two additional drying patterns.
Keywords: Drying, Colloidal droplet

19. Stolovicki, Elad; Elad Stolovicki, Lloyd Ung, Roy Ziblat and David A. Weitz

Harvard universty
"Drop chemostats: White biotechnology on a chip"
White biotechnology, the production of chemicals using cells or enzymes, is increasingly employed as it results in higher, overall greener chemical processes. Bio-production is also ideally suited in cases where the selectivity of enzymes for a specific molecule enantiomer (chirality) is critical. By using an emulsion of small drops of growth medium in oil as a micro-reactor, we can optimize the production yield of a desired bio-product, preforming toxicity tests or response-resistance assays. Another key feature of our system is that each, individual droplet emulates a larger-scale bioreactor that can be grown using batch, fed-batch or continuous culture methods. Thus, drop micro-reactors have the advantages of reducing R&D production time and cost by having thousands of parallel experiments, greatly reduced quantities of reagents, and compact space requirements.
Keywords: Keywords: White biotechnology, bio-production, drop micro-reactors, microfluidics

20. Thiele, Julian

Leibniz Institute of Polymer Research Dresden
"Design of microscopic polymer materials by droplet microfluidics and additive manufacturing for cell-free biotechnology"
The structural diversity of natural and synthetic macromolecular building blocks allows for designing polymer materials with tailored size, shape, porosity, degradability, stimuli-sensitivity and stiffness, which have thus evolved as promising experimental platform in cell biology and cell-free biotechnology. However, to process macromolecular building blocks into well-defined polymer materials with feature sizes from 1 to 100 µm, and spatial control over physicochemical / mechanical properties on the same length scale requires innovative fabrication strategies. On this account, we utilize two methods: droplet microfluidics to fabricate polymer microgels swollen in water, and 3D-printing based on micro-stereolithography to fabricate polymer materials with micron-scale precision in bulk. Focusing on applications in cell-free biotechnology, we combine these methods to design experimental platforms that reflect key aspects of cellular life, and allow for controlling biochemical reactions in a tailored microenvironment with reduced energy consumption and undesired side reactions.
Keywords: microfluidics, micro-stereolithography, cell-free protein synthesis

21. Werner, Joerg; Guanming Lao, David Weitz

SEAS, Harvard University
"Double emulsion drops in electric fields"
Electro-coalescence of water drops dispersed in oil, so-called water-in-oil (W/O) emulsions, is a well known phenomena that is employed in de-emulsification processes on the industrial scale. Complex, multiple emulsions, however, such as oil-in-water-in-oil (O/W/O) double emulsion drops resist de-emulsification and complete phase separation during electro-coalescence. We set out to study the behavior of double emulsion drops in electric fields under controlled conditions in droplet microfluidc devices. Droplet microfluidics enable the production of homogeneous complex emulsion drops with control over size, oil-to-water ratio, electric field strength, and residence time.
Keywords: Microfluidics, complex emulsions, electro-coalescence

22. Xin, Weiyue; Maria Santore

UMass Amherst
"The impact of curvature on solid domains in multicomponent phospholipid vesicles."
Multicomponent phospholipid membranes have long held scientific interest as an ideal model to study the complex phase behavior of biological membranes and their utility as drug delivery agents. The control of molecular organization is important because solid type and the domain shape will determine the ability of membrane diffusion, affect transportation along the membrane, also curvature at domain edges can influence biochemical reaction. Here I am using curvature to pattern patch-shaped membrane-integral solid domains on multicomponent phospholipid vesicles.
Keywords: Membranes, Vesicles phase separation

23. Yamani, Sami; Gareth McKinley; Irmgard Bischofberger

Massachusetts Institute of Technology
"Submerged turbulent jets of polymer solutions"
Dilute synthetic polymer solutions have been shown to reduce turbulent drag in pipelines and around marine vehicles. Water-soluble biopolymers such as flax seed mucilage extracts have the potential to serve as cheap and environmentally friendly alternatives to synthetic polymers. In this work, we employ Schlieren imaging to unveil the mixing dynamics and recirculating regions that develop in turbulent jets of dilute aqueous polymer solutions in quiescent water. At the interface of the viscoelastic jet and water, a free shear boundary layer develops leading to momentum transfer between the two fluids. We demonstrate the impact of viscoelasticity on this momentum transfer and evaluate the performance of both synthetic polymers and biopolymers in dampening turbulent vortical structures.
Keywords: Schlieren imaging, Dilute polymer solutions, mixing, turbulence, biopolymers

24. Yamani, Sami; Gareth McKinley; Irmgard Bischofberger

Massachusetts Institute of Technology
"Submerged turbulent jets of polymer solutions"
Dilute synthetic polymer solutions have been shown to reduce turbulent drag in pipelines and around marine vehicles. Water-soluble biopolymers such as flax seed mucilage extracts have the potential to serve as cheap and environmentally friendly alternatives to synthetic polymers. In this work, we employ Schlieren imaging to unveil the mixing dynamics and recirculating regions that develop in turbulent jets of dilute aqueous polymer solutions in quiescent water. At the interface of the viscoelastic jet and water, a free shear boundary layer develops leading to momentum transfer between the two fluids. We demonstrate the impact of viscoelasticity on this momentum transfer and evaluate the performance of both synthetic polymers and biopolymers in dampening turbulent vortical structures.
Keywords: Schlieren imaging, Dilute polymer solutions, mixing, turbulence, biopolymers

25. Yamani, Sami; Gareth McKinley; Irmgard Bischofberger

Massachusetts Institute of Technology
"Submerged turbulent jets of polymer solutions"
Dilute synthetic polymer solutions have been shown to reduce turbulent drag in pipelines and around marine vehicles. Water-soluble biopolymers such as flax seed mucilage extracts have the potential to serve as cheap and environmentally friendly alternatives to synthetic polymers. In this work, we employ Schlieren imaging to unveil the mixing dynamics and recirculating regions that develop in turbulent jets of dilute aqueous polymer solutions in quiescent water. At the interface of the viscoelastic jet and water, a free shear boundary layer develops leading to momentum transfer between the two fluids. We demonstrate the impact of viscoelasticity on this momentum transfer and evaluate the performance of both synthetic polymers and biopolymers in dampening turbulent vortical structures.
Keywords: Schlieren imaging, Dilute polymer solutions, mixing, turbulence, biopolymers

26. Yamani, Sami; Gareth McKinley; Irmgard Bischofberger

Massachusetts Institute of Technology
"Submerged turbulent jets of polymer solutions"
Dilute synthetic polymer solutions have been shown to reduce turbulent drag in pipelines and around marine vehicles. Water-soluble biopolymers such as flax seed mucilage extracts have the potential to serve as cheap and environmentally friendly alternatives to synthetic polymers. In this work, we employ Schlieren imaging to unveil the mixing dynamics and recirculating regions that develop in turbulent jets of dilute aqueous polymer solutions in quiescent water. At the interface of the viscoelastic jet and water, a free shear boundary layer develops leading to momentum transfer between the two fluids. We demonstrate the impact of viscoelasticity on this momentum transfer and evaluate the performance of both synthetic polymers and biopolymers in dampening turbulent vortical structures.
Keywords: Schlieren imaging, Dilute polymer solutions, mixing, turbulence, biopolymers

27. Yang, Xiaoyu; Xiaochen Ma, Ganggang Chang*, Ge Tian, Xiaoyu Yang*

Wuhan University of Technology; Harvard University
"Strong host-guest interaction induced supported amorphous/ crystalline hetero-phase Pd nanoclusters for highly efficient performance in tandem catalysis"
The tandem reaction processes that incorporate several reactions to give the final product in one operation have recently emerged as a promising field for advancing modern and sustainable chemistry due to the avoidance of separation, purification, and transfer processes of costly intermediates produced in each step. Acid, base and noble metal sites have been widely used as the catalytic active sites in one-pot tandem catalysis, however, the integration of different active site in to a single catalyst has been a great challenge considering the maximum usage of each active sites. Especially, for noble metal sites, the size, shape, composition, interaction with support/reactants and so on, can significantly affect its catalytic performance. In the present work, a strong host-guest interaction strategy has been employed to synthesis an ultrafine supported Pd nanoclusters, which showed an interesting amorphous/crystalline hetero-phase structure, and was first observed in sole metal nanoparticles as far as we know. When applied our catalyst in one-pot Knoevenagel condensation-hydrogenation reactions, our material showed excellent catalytic activities both in conversion and selectivity in terms of its ultralow Pd loading (0.14 wt%) and mild reaction conditions (atmospheric temperature and pressure), which was ascribed to the amorphous/crystalline hetero-phase structure induced by strong interaction between host and Pd nanoclusters. More importantly, a significantly higher structure and performance stability of our materials was also presented, and a unique restored property of amorphous/crystalline hetero-phase structure during H2 reducing was discovered. The successful fabrication of high performance bifunctional catalyst pave the way to new opportunities on design and preparation of highly stable metal supported composite materials, especially for advanced catalysis applications carried out under mild and green conditions.
Keywords: MOFs, tandem catalysis, amorphous nanoclusters, host-guest interaction

28. Yang, Xiaoyu; Xiaochen Ma, Ganggang Chang*, Ge Tian, Xiaoyu Yang*

Wuhan University of Technology; Harvard University
"Strong host-guest interaction induced supported amorphous/ crystalline hetero-phase Pd nanoclusters for highly efficient performance in tandem catalysis"
The tandem reaction processes that incorporate several reactions to give the final product in one operation have recently emerged as a promising field for advancing modern and sustainable chemistry due to the avoidance of separation, purification, and transfer processes of costly intermediates produced in each step. Acid, base and noble metal sites have been widely used as the catalytic active sites in one-pot tandem catalysis, however, the integration of different active site in to a single catalyst has been a great challenge considering the maximum usage of each active sites. Especially, for noble metal sites, the size, shape, composition, interaction with support/reactants and so on, can significantly affect its catalytic performance. In the present work, a strong host-guest interaction strategy has been employed to synthesis an ultrafine supported Pd nanoclusters, which showed an interesting amorphous/crystalline hetero-phase structure, and was first observed in sole metal nanoparticles as far as we know. When applied our catalyst in one-pot Knoevenagel condensation-hydrogenation reactions, our material showed excellent catalytic activities both in conversion and selectivity in terms of its ultralow Pd loading (0.14 wt%) and mild reaction conditions (atmospheric temperature and pressure), which was ascribed to the amorphous/crystalline hetero-phase structure induced by strong interaction between host and Pd nanoclusters. More importantly, a significantly higher structure and performance stability of our materials was also presented, and a unique restored property of amorphous/crystalline hetero-phase structure during H2 reducing was discovered. The successful fabrication of high performance bifunctional catalyst pave the way to new opportunities on design and preparation of highly stable metal supported composite materials, especially for advanced catalysis applications carried out under mild and green conditions.
Keywords: MOFs, tandem catalysis, amorphous nanoclusters, host-guest interaction

29. Yang, Xiaoyu; Xiaochen Ma, Ganggang Chang*, Ge Tian, Xiaoyu Yang*

Wuhan University of Technology; Harvard University
"Strong host-guest interaction induced supported amorphous/ crystalline hetero-phase Pd nanoclusters for highly efficient performance in tandem catalysis"
The tandem reaction processes that incorporate several reactions to give the final product in one operation have recently emerged as a promising field for advancing modern and sustainable chemistry due to the avoidance of separation, purification, and transfer processes of costly intermediates produced in each step. Acid, base and noble metal sites have been widely used as the catalytic active sites in one-pot tandem catalysis, however, the integration of different active site in to a single catalyst has been a great challenge considering the maximum usage of each active sites. Especially, for noble metal sites, the size, shape, composition, interaction with support/reactants and so on, can significantly affect its catalytic performance. In the present work, a strong host-guest interaction strategy has been employed to synthesis an ultrafine supported Pd nanoclusters, which showed an interesting amorphous/crystalline hetero-phase structure, and was first observed in sole metal nanoparticles as far as we know. When applied our catalyst in one-pot Knoevenagel condensation-hydrogenation reactions, our material showed excellent catalytic activities both in conversion and selectivity in terms of its ultralow Pd loading (0.14 wt%) and mild reaction conditions (atmospheric temperature and pressure), which was ascribed to the amorphous/crystalline hetero-phase structure induced by strong interaction between host and Pd nanoclusters. More importantly, a significantly higher structure and performance stability of our materials was also presented, and a unique restored property of amorphous/crystalline hetero-phase structure during H2 reducing was discovered. The successful fabrication of high performance bifunctional catalyst pave the way to new opportunities on design and preparation of highly stable metal supported composite materials, especially for advanced catalysis applications carried out under mild and green conditions.
Keywords: MOFs, tandem catalysis, amorphous nanoclusters, host-guest interaction

30. Yang, Xiaoyu; Xiaochen Ma, Ganggang Chang*, Ge Tian, Xiaoyu Yang*

Wuhan University of Technology; Harvard University
"Strong host-guest interaction induced supported amorphous/ crystalline hetero-phase Pd nanoclusters for highly efficient performance in tandem catalysis"
The tandem reaction processes that incorporate several reactions to give the final product in one operation have recently emerged as a promising field for advancing modern and sustainable chemistry due to the avoidance of separation, purification, and transfer processes of costly intermediates produced in each step. Acid, base and noble metal sites have been widely used as the catalytic active sites in one-pot tandem catalysis, however, the integration of different active site in to a single catalyst has been a great challenge considering the maximum usage of each active sites. Especially, for noble metal sites, the size, shape, composition, interaction with support/reactants and so on, can significantly affect its catalytic performance. In the present work, a strong host-guest interaction strategy has been employed to synthesis an ultrafine supported Pd nanoclusters, which showed an interesting amorphous/crystalline hetero-phase structure, and was first observed in sole metal nanoparticles as far as we know. When applied our catalyst in one-pot Knoevenagel condensation-hydrogenation reactions, our material showed excellent catalytic activities both in conversion and selectivity in terms of its ultralow Pd loading (0.14 wt%) and mild reaction conditions (atmospheric temperature and pressure), which was ascribed to the amorphous/crystalline hetero-phase structure induced by strong interaction between host and Pd nanoclusters. More importantly, a significantly higher structure and performance stability of our materials was also presented, and a unique restored property of amorphous/crystalline hetero-phase structure during H2 reducing was discovered. The successful fabrication of high performance bifunctional catalyst pave the way to new opportunities on design and preparation of highly stable metal supported composite materials, especially for advanced catalysis applications carried out under mild and green conditions.
Keywords: MOFs, tandem catalysis, amorphous nanoclusters, host-guest interaction

31. Yang, Xiaoyu; Xiaochen Ma, Ganggang Chang*, Ge Tian, Xiaoyu Yang*

Wuhan University of Technology; Harvard University
"Strong host-guest interaction induced supported amorphous/ crystalline hetero-phase Pd nanoclusters for highly efficient performance in tandem catalysis"
The tandem reaction processes that incorporate several reactions to give the final product in one operation have recently emerged as a promising field for advancing modern and sustainable chemistry due to the avoidance of separation, purification, and transfer processes of costly intermediates produced in each step. Acid, base and noble metal sites have been widely used as the catalytic active sites in one-pot tandem catalysis, however, the integration of different active site in to a single catalyst has been a great challenge considering the maximum usage of each active sites. Especially, for noble metal sites, the size, shape, composition, interaction with support/reactants and so on, can significantly affect its catalytic performance. In the present work, a strong host-guest interaction strategy has been employed to synthesis an ultrafine supported Pd nanoclusters, which showed an interesting amorphous/crystalline hetero-phase structure, and was first observed in sole metal nanoparticles as far as we know. When applied our catalyst in one-pot Knoevenagel condensation-hydrogenation reactions, our material showed excellent catalytic activities both in conversion and selectivity in terms of its ultralow Pd loading (0.14 wt%) and mild reaction conditions (atmospheric temperature and pressure), which was ascribed to the amorphous/crystalline hetero-phase structure induced by strong interaction between host and Pd nanoclusters. More importantly, a significantly higher structure and performance stability of our materials was also presented, and a unique restored property of amorphous/crystalline hetero-phase structure during H2 reducing was discovered. The successful fabrication of high performance bifunctional catalyst pave the way to new opportunities on design and preparation of highly stable metal supported composite materials, especially for advanced catalysis applications carried out under mild and green conditions.
Keywords: MOFs, tandem catalysis, amorphous nanoclusters, host-guest interaction

32. Yang, Xiaoyu; Xiaochen Ma, Ganggang Chang*, Ge Tian, Xiaoyu Yang*

Wuhan University of Technology; Harvard University
"Strong host-guest interaction induced supported amorphous/ crystalline hetero-phase Pd nanoclusters for highly efficient performance in tandem catalysis"
The tandem reaction processes that incorporate several reactions to give the final product in one operation have recently emerged as a promising field for advancing modern and sustainable chemistry due to the avoidance of separation, purification, and transfer processes of costly intermediates produced in each step. Acid, base and noble metal sites have been widely used as the catalytic active sites in one-pot tandem catalysis, however, the integration of different active site in to a single catalyst has been a great challenge considering the maximum usage of each active sites. Especially, for noble metal sites, the size, shape, composition, interaction with support/reactants and so on, can significantly affect its catalytic performance. In the present work, a strong host-guest interaction strategy has been employed to synthesis an ultrafine supported Pd nanoclusters, which showed an interesting amorphous/crystalline hetero-phase structure, and was first observed in sole metal nanoparticles as far as we know. When applied our catalyst in one-pot Knoevenagel condensation-hydrogenation reactions, our material showed excellent catalytic activities both in conversion and selectivity in terms of its ultralow Pd loading (0.14 wt%) and mild reaction conditions (atmospheric temperature and pressure), which was ascribed to the amorphous/crystalline hetero-phase structure induced by strong interaction between host and Pd nanoclusters. More importantly, a significantly higher structure and performance stability of our materials was also presented, and a unique restored property of amorphous/crystalline hetero-phase structure during H2 reducing was discovered. The successful fabrication of high performance bifunctional catalyst pave the way to new opportunities on design and preparation of highly stable metal supported composite materials, especially for advanced catalysis applications carried out under mild and green conditions.
Keywords: MOFs, tandem catalysis, amorphous nanoclusters, host-guest interaction

33. Yang, Xiaoyu; Xiaochen Ma, Ganggang Chang, Ge Tian

SEAS, Harvard University
"Strong host-guest interaction induced supported amorphous/ crystalline hetero-phase Pd nanoclusters for highly efficient performance in tandem catalysis"
The tandem reaction processes that incorporate several reactions to give the final product in one operation have recently emerged as a promising field for advancing modern and sustainable chemistry due to the avoidance of separation, purification, and transfer processes of costly intermediates produced in each step. Acid, base and noble metal sites have been widely used as the catalytic active sites in one-pot tandem catalysis, however, the integration of different active site in to a single catalyst has been a great challenge considering the maximum usage of each active sites. Especially, for noble metal sites, the size, shape, composition, interaction with support/reactants and so on, can significantly affect its catalytic performance. In the present work, a strong host-guest interaction strategy has been employed to synthesis an ultrafine supported Pd nanoclusters, which showed an interesting amorphous/crystalline hetero-phase structure, and was first observed in sole metal nanoparticles as far as we know. When applied our catalyst in one-pot Knoevenagel condensation-hydrogenation reactions, our material showed excellent catalytic activities both in conversion and selectivity in terms of its ultralow Pd loading (0.14 wt%) and mild reaction conditions (atmospheric temperature and pressure), which was ascribed to the amorphous/crystalline hetero-phase structure induced by strong interaction between host and Pd nanoclusters. More importantly, a significantly higher structure and performance stability of our materials was also presented, and a unique restored property of amorphous/crystalline hetero-phase structure during H2 reducing was discovered. The successful fabrication of high performance bifunctional catalyst pave the way to new opportunities on design and preparation of highly stable metal supported composite materials, especially for advanced catalysis applications carried out under mild and green conditions.
Keywords: MOFs, tandem catalysis, amorphous nanoclusters, host-guest interaction

34. Yuan, Yuan; Jing Xia, Brouchon Julie, John Heyman, David Weitz

Harvard University
"Droplet-based assay for activated immune cell detection and sorting"
Immune system is a defense system of our body to fight against cancer or infections. In our blood, there is a huge number of immune cells, about 7 billion immune cells per liter blood, while only a small fraction of cells would be activated when pathogen comes. Insufficient activation usually accounts for severe diseases like cancer and viral infections, so we really need a good way to detect and sort activated immune cells to take full advantage of the immune system. Based on our microfluidic droplet technique, we developed a quick assay by co-encapsulating individual immune cells and target cells into one drop. On one hand, immune cells are coat with a bispecific antibody, which can be coated on the surface of immune cells and thus the secreted cytokines could be captured and enriched on the surface of the exact activated immune cells. This in-drop assay greatly reduces the cross-contamination in bulk. As compatible with flow cytometry, thousands of cells with signals could be sorted and recovered for further analysis in our assay.
Keywords: Droplet microfluidics, Immune therapy, single-cell quick assay

35. Zhang, Weixia; Weixia Zhang, Liangliang Qu, Hao Pei, Jonathan Didier, David Weitz

Harvard SEAS
"Controllable Fabrication of Inhomogeneous Microcapsules for Triggered Release by Osmotic Pressure"
In this study, microcapsules with inhomogeneous shell thickness are controllably fabricated to encapsulate various cargo using a microfluidic approach, which can be triggered to release cargo at a low critical osmotic pressure. Using a glass capillary microfluidic device, monodisperse water-in-oil-in-water double emulsion droplets are produced with cargo in the core and an inhomogeneous middle oil layer containing photo-curable monomers that can be crosslinked under UV exposure. The inhomogeneity of shell thickness in these microcapsules can be controlled by tuning the flow rate ratio of the middle oil phase to the inner aqueous phase. It is demonstrated that the swelling of these inhomogeneous microcapsules begins at the thinnest part of shell and eventually leading to rupture at the weak spot with a low osmotic pressure. Moreover, systematic studies indicate the rupture fraction of these inhomogeneous microcapsules increases with the increasing internal osmotic pressure and the inhomogeneity. Finally, the inhomogeneous microcapsules are demonstrated to be impermeable to small probe molecules, which enables long-term storage, and to release enzyme triggered by osmotic pressure without impairing its biological activity. Our study provides a new approach to design effective carriers to protect and release biomolecules on-demand upon applying osmotic shock.
Keywords: 

36. Zhang, Xingcai; J. Heyman, D. Weitz, E. Appel

Harvard University;
"Multifunctional Drugs/Vaccines Delivery System"
My project is to generate a transformational strategy for vaccination/drugs in a single injection. 1.5 million children die each year from vaccine-preventable diseases. According to the World Health Organization, 40% of those children had received the first dose of the vaccine but were unable to complete the 3-dose series. Improving vaccination technology can be truly transformational in the prevention of infectious disease. The majority of vaccines require multiple doses to elicit full immunization, which increases both the cost and complexity of reaching the entire globe.4 Moreover, vaccines/drugs are generally formulations of biologics, which are highly susceptible to denaturation and subsequent loss of activity, thus complicating their global distribution and storage. A stable multifunctional vaccines/drugs single-administration technology would reduce the number of required interventions, thereby preventing the unnecessary spreading of infectious disease, especially amongst rural populations, who must often travel far to reach their closest healthcare clinic. The enhanced convenience and reduced costs associated with this approach will certainly be welcomed in the developed world. I am developing a single administration vaccination platform using advanced micro/nanotechnology along with a novel hydrogel excipient to create tunable, pulsatile release of vaccines.
Keywords: Multifunction; Drugs; Vaccines; Delivery System

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