Abstracts for Invited Talks and Soundbites

82nd New England Complex Fluids Meeting
ON HOLD - Brown University | Friday, March 13, 2020
Registration deadline: Wednesday, March 11, 2020

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Invited Talks

1. Bourouiba, Lydia


Life of bubbles at the interface
Bubbles are ubiquitous in industrial and environmental processes, indoors and outdoors, and have an important impact on a wide range of systems. They can be beneficial in mixing bulk water, they contribute significantly to the planetary-scale transfer of compounds from water bodies to the atmosphere and they are also sources of contamination. Upon reaching the air–water interface, bubbles are the source of myriads of droplets transporting the organisms, chemicals, or particles from the bulk in which they traveled to the air that we breathe. An understanding of this important source of droplets starts by understanding the formation, aging, and death of bubbles at the air–water interface. We start by focusing on the fundamental physics portion of the problem and how a large class of Marangoni-inducing effects fundamentally change the lifetime of bubbles. We discuss how physically and biologically induced Marangoni effects can sustain bubble lifetimes dramatically, with profound implications on dispersal of contaminants and life.

References/more resources: http://lbourouiba.mit.edu/research/projects/water-air-transfer-bubbles-interface


2. Mak, Michael

Yale University

Biophysical signals in the extracellular matrix: Interplay of cell dynamics and matrix properties
The extracellular matrix (ECM) in stromal microenvironments is typically comprised of a complex network of fibers. The ECM is a reservoir of biophysical and biochemical signals—including stiffness, alignment, tension, and ligand density—that can direct cell behavior and fate. Importantly, cells can induce the formation of these signals and create dynamic signaling profiles in the microenvironment. Many of these signals can be generated via the application of force, which induces strain-stiffening and strain-alignment of the local matrix. Additional signaling motifs can be achieved via the force-sensitive nature of the molecular bonds than interconnect fibers, which enables non-elastic remodeling. In our lab, we investigate, via computational and experimental methods, the regulators and underlying mechanisms that drive the emergence of these cell-generated signals in the microenvironment.

3. Olson, Sarah

Worcester Polytechnic Institute

Sperm navigation in complex environments
Microorganisms can swim in a variety of environments, interacting with chemicals and other proteins in the fluid. In this talk, we will highlight recent computational methods and results for swimming efficiency and hydrodynamic interactions of swimmers in different fluid environments. Sperm are modeled via a centerline representation where forces are solved for using elastic rod theory. The method of regularized Stokeslets is used to solve the fluid-structure interaction where emergent swimming speeds can be compared to asymptotic analysis. In the case of fluids with extra proteins or cells that may act as friction, swimming speeds may be enhanced and attraction may not occur. We will also highlight how parameter estimation techniques can be utilized to infer fluid and/or swimmer properties.

4. Zenit, Roberto

Brown University

Fluid mechanics of artistic painting
Painting is a fluid mechanical process. The action of covering a solid surface with a layer of a viscous fluid is one of the most common human activities; virtually all manmade surfaces are painted to provide protection against the environment or simply for decoration. This process, in an industrial context, has been vastly studied and it is well understood. In the case of artistic painting the purpose is different. Painters learn how to manipulate the nonuniform deposition of paint onto a surface, through lengthy empirical testing of the action and modifying the physical properties of the fluids, to create textures and patterns of aesthetic value. In this paper, an analysis of some notable painting techniques is presented from the point of view of fluid mechanics. In particular, we discuss the so-called "accidental painting" technique, originally devised by David A. Siqueiros, which is the result of a Rayleigh-Taylor instability. An analysis of several techniques used by Jackson Pollock is also presented, showing how he learned to carefully control the motion of viscous filaments to create his famous abstract compositions. We also briefly discuss how pattern and textures are produced in decalcomania and watercolor painting. These investigations indicate that it is possible to establish concrete scientific discussions among modern fluid mechanics, art, art history, and conservation.

Sound Bites

1. Berezney, John; Zvonimir Dogic, Seth Fraden

Brandeis University

Active cytoskeletal composite networks
We describe a new composite material composed of an active microtubule network driven by kinesin motors which interdigitates a second network of entangled actin filaments. We show such a material generates a wide variety of dynamic phenomena, including bulk contraction and bulk expansion, which we capture in a state diagram. Finally, we characterize the behavior in these states.
Keywords: active matter, actin, microtubules, kinesin

2. Bhaskar, Dhananjay; Ian Y. Wong

Brown University

Using Topological Data Analysis to Identify Patterns in Active Matter
I will outline a novel methodology to detect phase transitions and quantify pattern formation observed in soft-tissue cancer biology and in simulations of active matter. The proposed method, based on persistent homology, is model-agnostic, scale invariant, robust to noise and tolerant to changes in population size.
Keywords: pattern formation, active matter, soft tissues, topological data analysis

3. Cochard, Thomas; Y. Song, L. Xiao, D. A. Weitz


Hydraulic fracture dynamics
Hydraulic fracking of shale reservoirs is a process where a highly pressurized fluid is injected into the shale matrix, inducing fractures that create a connected path between the pores filled with hydrocarbons. The dynamics of hydraulic fractures in high strength materials remain poorly understood, despite the widespread application of hydraulic fracking. Particularly related to mitigation of seismicity and aquifer pollution. Most of the research on hydraulic fracking is focused on the evolution of the pressure during the fracture propagation. In contrast, in our work, we are developing an energy balance approach that accounts for both the compressed volume and pressure of the injected fluid. Importantly, by only considering the pressure evolution within the system, the total volume of the injected fluid is neglected. Our results show that the volume of fluid cannot be neglected as the applied pressure upon fracture is at least 350 times the atmospheric pressure. To accomplish that, we designed a 3D-printed cube using a stereolithography apparatus with an injection system allowing us to initiate a systematic controlled hydraulic fracture. We use high speed imaging to follow the fracture propagation and measure the pressure evolution and the volume of injected fluid being compressed, as piezo electric sensors to evaluate the resulting deformation. As a result, we can demonstrate that the desired volume of fractures can be triggered by the total volume of fluid used during the fracking process. In addition, we find that by using an energetic approach, we can estimate mechanical parameters in situ such as the fracture toughness of the material.
Keywords: Hydraulic fracture, high speed imaging, 3D printing, Seismic wave propagation

4. Ellis, Perry; Debojyoti Panda, Giridhar Anand, Sharad Ramanathan, David A. Weitz

Harvard University

Identifying pathogenic bacteria by phenotyping individual cells
Identifying pathogenic bacteria in natural samples has important consequences for human health. For example, 80% of foodborne illness comes from "unknown origin" --- there are either too few pathogenic bacteria in the sample to detect, or there doesn't exist a specific test for the pathogen at fault. To address these concerns we focus on high-throughput methods that require no prior knowledge of the bacteria to assess its pathogenicity. 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:  Microfluidics, Screening, Pathogenicity, Droplets

5. Ho, Ian; Giuseppe Pucci, Daniel M. Harris

Brown University

Self-propelling capillary surfers on an oscillating fluid bath
We explore the dynamics of millimetric "surfers" trapped at the air-water interface on a vibrating fluid bath. Our experiments demonstrate that these surfers can self propel at constant horizontal velocity when the rotational symmetry of the body is broken. A system of multiple surfers will interact with one another and self-organise through their mutual capillary wavefield. Our results open the door to further investigations of this novel and tunable active system at the fluid interface.
Keywords: Surface Tension, Active Matter

6. Kumar, Ajay Harishankar; Thomas R. Powers, Daniel M. Harris

Brown University

Theoretical Investigation of Taylor Dispersion of Elongated Rods
Particles transported in fluid flows such as cells, polymers or nanorods are rarely spherical in nature. In this study, we theoretically predict the asymptotic lateral dispersion of an initially localized patch of elongated Brownian particles in a 2D pressure-driven shear flow. Starting with the fluxes, we begin with a conservation equation in the form of a Fokker-Planck equation. This master equation can then be simplified using asymptotic analysis for large transitional Peclet numbers, specifically when the short rotational time scale is well separated from the longer transitional time scale. The simplified equations are then solved to obtain an effective diffusivity factor which compares well with Brownian Dynamics simulations and predict an enhanced lateral dispersion for elongated particles.
Keywords: Taylor Dispersion, Microfluidics, Anisotropic Diffusion, Migration

7. Seara, Daniel; Michael Murrell, Benjamin Machta

Yale University

Entropy production in pattern forming fields
Living and non-living active matter consumes energy at the microscopic scale to drive emergent, macroscopic behavior including traveling waves and coherent oscillations. Recent work has characterized non-equilibrium systems by their total entropy production, but little has been said about how dissipation manifests in distinct spatiotemporal patterns. We introduce a measure of dissipation we term the entropy production factor (EPF) to quantify how time reversal symmetry is broken in field theories across scales. We use the EPF to study simulations of the Brusselator, a minimal model for non-linear biochemical oscillators, and find that the energetic cost of synchronization is negligible compared to the energetic cost of establishing robust oscillations. The EPF measures how microscopic irreversibility propagates to larger length and time scales, and integration through frequency space bounds the net dissipation of any stochastic process.
Keywords: entropy production, pattern formation, biochemical oscillator, stochastic fields

8. Wong, Ian; Susan E. Leggett, Mohak Patel, Thomas M. Valentin, Lena Gamboa, Amanda S. Khoo, Evelyn Kendall Williams, Christian Franck

Brown University

Mechanophenotyping of 3D multicellular clusters using displacement arrays of rendered tractions
Epithelial tissue development, wound healing, and tumor progression are governed by mechanical interactions between groups of cells and the surrounding extracellular matrix. Multicellular clusters exert spatially heterogeneous deformations within 3D biomaterials, which confound existing analyses established for individual cells. Here, we demonstrate a scalable method to profile multicellular clusters based on how they locally pull, push, and twist the surrounding matrix. We validate this method using biochemical treatments that perturb cell–cell and cell–matrix interactions, which result in cluster disorganization and dissemination with distinct signatures of matrix deformation. This assay is implemented in a standardized well-plate format, which enables higher-throughput measurements of aberrant cell–matrix interactions and drug responses in human disease.
Keywords: cell–matrix interactions, 3D culture, collective migration, epithelial–mesenchymal transition

9. Wu, Jiwei; T. Cochard, L. Xiao, D. A. Weitz

Harvard University

Experimental Investigations of Oil Transport in 2D Porous Media
The understanding of immiscible flow in porous media is a major interest for oil and gas recovery in conventional reservoir. After the secondary oil recovery (water flood), the oil network is disconnected in the pore structure. In order to understand how the single oil ganglia is being transported in such condition, we generate an artificial 2D porous media where we can trigger dominant parameters such as pore size, porosity and connectivity. Those artificial porous materials are then transferred into a PDMS chip. Thanks to our microfluidic design we can generate oil ganglia and look at its transport under certain condition: Type of fluids injected (water, polymer and surfactant mixture), surface properties of the PDMS device. Coupled with high speed imaging we can track the initial oil ganglia, look at its transport which can be achieved in several ways: continuous transport, break up into smaller ganglia but also study the coalescence of oil ganglia under certain conditions. New way of modelling the transport behavior are proposed and a framework of modelling the tertiary oil and gas recovery is suggested.
Keywords: artificial porous media; multiphasic flow; wettability; viscous flow; interfacial tension

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© 2020 New England Complex Fluids Workshop
Supported by Harvard University's
Materials Research Science and Engineering Center