Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session Y17: Emulsions and Foams |
Hide Abstracts |
Sponsoring Units: GSOFT Chair: Chinedum Osuji, Yale University Room: 276 |
Friday, March 17, 2017 11:15AM - 11:27AM |
Y17.00001: Optimizing the use of surfactants and water with foams: a comparison between soapy solutions and foams for sebum detergency Frederic Restagno, Pauline Valois, Pauline Petit, Colette Cazeneuve, Luc Nicolas-Morgantini, Emmnauelle Rio, Gustavo Luengo Human sebum is excreted at the skin surface by the sebaceous glands. Surfactants are the core ingredients of shampoos and other cosmetics to eliminate the excess of sebum as detergency is the classical mechanism used for hair cleaning.. In this study, we add a precise amount of sebum on different hair. We developed a new protocol to measure the cleaning efficiency of surfactant solutions and foams made with the same surfactant solutions based on a spectroscopic method. More precisely, we add a well-controlled amount of colored sebum, we clean the hair with our test foam or solution and we remove completely the unwashed sebum. The sebum remaining after washing is quantified by visible spectroscopy. We tested either classical detergents such as SLES at different concentrations or white egg. The studies were performed on natural or bleached hair. In all the studied case, it was not possible to observe any difference in the cleaning efficiency between the bulk solutions and the foams made from the solutions. This study could allow to develop new shampoos formulations or dispensers in order to replace washing solutions by foams that could have the same cleaning efficiency with a lower amount of surfactants; diminishing the water rinsing needs during application. [Preview Abstract] |
Friday, March 17, 2017 11:27AM - 11:39AM |
Y17.00002: Teasing Bio-inspired Micro-Reactor Chemistry out of Simple Polymer Solutions Huan Wang, Steve Granick We live in an age where research fields benefit from cross-pollination. In living cells, liquid droplets, which mostly are dynamical assemblies of macromolecules, function to enable chemical reactions by concentrating reactants through this nonequilibrium process. We have noticed that droplets of polymer in volatile solvent similarly concentrate into local dynamical pockets as evaporation proceeds. This presents interesting new physics on the one hand as the influence of polymer viscoelasticity in this nonequilibrium situation is subtle. It also presents chemists with a practical tool to trigger chemical reactions that in the bulk solutions would at equilibrium not occur or cease reaction by selective depletion of reactants into pockets. [Preview Abstract] |
Friday, March 17, 2017 11:39AM - 11:51AM |
Y17.00003: Border-Crossing Model for the Diffusive Coarsening of Wet Foams Douglas Durian, Cody Schimming For dry foams, the transport of gas from small high-pressure bubbles to large low-pressure bubbles is dominated by diffusion across the thin soap films separating neighboring bubbles. For wetter foams, the film areas become smaller as the Plateau borders and vertices inflate with liquid. So-called ``border-blocking" models can explain some features of wet-foam coarsening based on the presumption that the inflated borders totally block the gas flux; however, this approximation dramatically fails in the wet/unjamming limit where the bubbles become close-packed spheres. Here, we account for the ever-present border-crossing flux by a new length scale defined by the average gradient of gas concentration inside the borders. We argue that it is proportional to the geometric average of film and border thicknesses, and we verify this scaling and the numerical prefactor by numerical solution of the diffusion equation. Then we show how the $dA/dt=K_0(n-6)$ von~Neumann law is modified by the appearance of terms that depend on bubble size and shape as well as the concentration gradient length scale. Finally, we use the modified von~Neumann law to compute the growth rate of the average bubble, which is not constant. [Preview Abstract] |
Friday, March 17, 2017 11:51AM - 12:03PM |
Y17.00004: Effect of Salt on Drainage via Stratification in Micellar Foam Films Subinuer Yilixiati, Rabees Rafiq, Yiran Zhang, Vivek Sharma Understanding and controlling the drainage kinetics of thin films is an important problem that underlies the stability, lifetime and rheology of foams and emulsions. Foam films containing micelles, colloidal particles or polyelectrolyte-surfactant mixtures exhibit step-wise thinning or stratification, due to the influence of non-DLVO forces, including supramolecular oscillatory structural forces. In this study, we use Interferometry, Digital, Imaging, Optical Microscopy protocols to investigate the drainage and stratification in micellar foam films (\textless 100 nm) with high spatial (thickness \textless 10 nm) and temporal resolution (\textless 1 ms). We determine how the concentration of surfactants and added salt influences the nanoscopic topography, stratification kinetics and step size of foam films formed using micellar sodium dodecyl sulfate (SDS) solutions. [Preview Abstract] |
Friday, March 17, 2017 12:03PM - 12:15PM |
Y17.00005: Experiments on foam stability at different salinities Tatsuo Izawa, Lesley James, Anand Yethiraj A deeper understanding of foam stability in the presence of high salinity levels that are characteristic of ocean brine is important for enhancing oil recovery. We experimentally investigate how 3 dimensional foams drain and collapse under gravitational stress at various temporal and spatial scales. By employing an imaging technique that simultaneously probes the macroscopic and bubble scale features of the foam system, we study the concentration dependence of synthetic ocean brine on foam stability. From our results, we obtain the physical characteristics of foam on time scales from seconds to days. This work may potentially be useful in characterizing different aqueous foam systems. It may also allow us to detect any signals that may arise prior to catastrophic collapses of foams on different length scales. [Preview Abstract] |
Friday, March 17, 2017 12:15PM - 12:27PM |
Y17.00006: Domain and nanoridge growth kinetics in stratifying foam films Yiran Zhang, Vivek Sharma Ultrathin films exhibit stratification due to confinement-induced structuring and layering of small molecules in simple fluids, and of supramolecular structures like micelles, lipid layers and nanoparticles in complex fluids. Stratification proceeds by the formation and growth of thinner domains at the expense of surrounding thicker film, and results in formation of nanoscopic terraces and mesas within a film. The detailed mechanisms underlying stratification are still under debate, and are resolved in this contribution by addressing long-standing experimental and theoretical challenges. Thickness variations in stratifying films are visualized and analyzed using interferometry, digital imaging and optical microscopy (IDIOM) protocols, with unprecedented high spatial (thickness \textless 100 nm, lateral \textasciitilde 500 nm) and temporal resolution (\textless 1 ms). Using IDIOM protocols we developed recently, we characterize the shape and the growth dynamics of nanoridges that flank the expanding domains in micellar thin films. We show that topographical changes including nanoridge growth, and the overall stratification dynamics, can be described quantitatively by nonlinear thin film equation, amended with supramolecular oscillatory surface forces. [Preview Abstract] |
Friday, March 17, 2017 12:27PM - 12:39PM |
Y17.00007: Dynamic surface tension measurements of ionic surfactants using maximum bubble pressure tensiometry Camilla U. Ortiz, Norman Moreno, Vivek Sharma Dynamic surface tension refers to the time dependent variation in surface tension, and is intimately linked with the rate of mass transfer of a surfactant from liquid sub-phase to the interface. The diffusion- or adsorption-limited kinetics of mass transfer to interfaces is said to impact the so-called foamability and the Gibbs-Marangoni elasticity of surfaces. Dynamic surface tension measurements carried out with conventional methods like pendant drop analysis, Wilhelmy plate, etc. are limited in their temporal resolution (\textgreater 50 ms). In this study, we describe design and application of maximum bubble pressure tensiometry for the measurement of dynamic surface tension effects at extremely short (1-50 ms) timescales. Using experiments and theory, we discuss the overall adsorption kinetics of charged surfactants, paying special attention to the influence of added salt on dynamic surface tension. [Preview Abstract] |
Friday, March 17, 2017 12:39PM - 12:51PM |
Y17.00008: Stress distributions and bubble rearrangements in a compressed bubble raft Klebert Feitosa, Brian Seymour, Nicholas Albright, Christine O'Dea, Shengfeng Cheng Soap bubbles floating at an air-water interface experience shape deformations as a result of surface tension and hydrostatic forces. The deformation of the fluid interface causes the bubbles to aggregate forming stable jammed packings. We investigate the stress distributions of such aggregates by uniaxially compressing a bubble raft between parallel plates while capturing the deformations and rearrangements with a video camera. We find that under compression, the stress distribution is inhomogeneous and characterized by strings of stressed bubbles surrounding less stressed ones reminiscent of force chains in granular materials. Bubble rearrangements are then analyzed against the stress map to obtain their correlation with local stress variations in the bubble raft. [Preview Abstract] |
Friday, March 17, 2017 12:51PM - 1:03PM |
Y17.00009: Interfacial complexation in microfluidic droplets for single-step fabrication of microcapsule Gilad Kaufman, Siamak Nejati, Raphael Sarfati, Rostislav Boltyanskiy, Danielle Williams, Wei Liu, Ashley Schloss, Lynn Regan, Elsa Yan, Eric Dufrense, Michael Loewenberg, Chinedum Osuji We present microfluidic interfacial complexation in emulsion droplets as a simple single-step approach for fabricating a large variety of stable monodisperse microcapsules with tailored mechanical properties, protein binding and controlled release behavior. We rely on electrostatic interactions and hydrogen bonding to direct the assembly of complementary species at oil-water droplet interfaces to form microcapsules with polyelectrolyte shells, composite polyelectrolyte-nanoparticle shells, and copolymer-nanofiber shells. Additionally, we demonstrate the formation of microcapsules by adsorption of an amphiphilic bacterial hydrophobin, BslA, at oil-in-water and water-in-oil droplets, and protein capture on these capsules using engineered variants of the hydrophobin. We discuss the composition dependence of mechanical properties, shell thickness and release behavior, and regimes of stability for microcapsule fabrication. Nanoparticle based microcapsules display an intriguing plastic deformation response which enables the formation of large aspect ratio asperities by pipette aspiration of the shell. [Preview Abstract] |
Friday, March 17, 2017 1:03PM - 1:15PM |
Y17.00010: Rearrangement of 2D clusters of droplets under compression: transition from crystal to glass Jean-Christophe Ono-dit-Biot, Solomon Barkley, Eric Weeks, Thomas Salez, Elie Raphael, Kari Dalnoki-Veress A crystal and a glass are different at a molecular level which leads to strong consequences at the macroscopic scale. We have developed an ideal experimental system to model such structures. The 2D clusters are made of an emulsion of lightly attractive, stabilized oil droplets ($R \sim 10$ $\mu m$) in water which are assembled droplet by droplet (tens of droplets). We study the response of the cluster when it is compressed between two thin glass rods ($R_c \sim 10$ $\mu m$). One glass rod is used as a force transducer in order to measure the forces as the droplets spatially rearrange under compression. Coupling the optical microscopy images of structural rearrangements within the 2D cluster with the direct force measurements provides insight into the failure mechanisms. Perfectly ordered crystals (highly monodisperse droplets) show well defined transitions. As the number of defects (substitution of a droplet by a smaller one) is increased in the crystal, we can study the transition toward a glassy system (bidisperse cluster). Additionally, the impact of the size of the cluster, the geometry of the initial aggregate, the relative size of a defect or even its position can be studied. [Preview Abstract] |
Friday, March 17, 2017 1:15PM - 1:27PM |
Y17.00011: A Microscopic Test of Fluidity in Soft Sphere Suspensions Marcel Workamp, Sepideh Alaie, Joshua Dijksman We experimentally study the possible microscopic ingredients of the fluidity field that determines the slow flow behavior in a suspension of soft spheres. The experimental system consists of hydrogel particles made using a simple macroscopic technique. We perform experiments using a custom designed Couette shear cell, with transparent bottom and lid. The measurement cell has a fixed volume and we investigate suspensions at a finite pressure, which we measure on a part of the lid. By imaging in transmission mode, we have access to local velocities and stresses through the photoelastic properties of the hydrogel. As we use a rheometer to drive the system, we also measure the driving stress. We have thus have access to the local quantities required to probe the ingredients of fluidity. We compare results of suspensions of two different types of hydrogel; one of these displays a flow instability in its global rheology. We investigate how the local rheology is influenced by the instability. [Preview Abstract] |
Friday, March 17, 2017 1:27PM - 1:39PM |
Y17.00012: Hyperuniform materials made with microfluidics Pavel Yazhgur, Joshua Ricouvier, Romain Pierrat, RĂ©mi Carminati, Patrick Tabeling Hyperuniform materials, being disordered systems with suppressed long-scale fluctuations, now attract a significant scientific interest, especially due to their potential applications for disordered photonic materials production. In our project we study a jammed packing of oil droplets in water. The droplets 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 and thereby govern the structural properties of the obtained material. The pseudo-2D (a monolayer of droplets) and 3D systems are investigated. Our results show that at appropriate experimental conditions droplets self-organize in 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 materials production. [Preview Abstract] |
Friday, March 17, 2017 1:39PM - 1:51PM |
Y17.00013: Large Amplitude Oscillatory Shear (LAOS) of Acrylic Emulsion-Based Pressure Sensitive Adhesives (PSAs) Sipei Zhang, Alan Nakatani, William Griffith Large Amplitude Oscillatory Shear (LAOS) testing has recently taken on renewed interest in the rheological community. It is a very useful tool to probe the viscoelastic response of materials in the non-linear regime. Much of the discussion on polymers in the LAOS field has focused on melts in or near the terminal flow regime. Here we present a LAOS study conducted on a commercial rheometer for acrylic emulsion-based pressure sensitive adhesive (PSA) films in the plateau regime. The films behaved qualitatively similar over an oscillation frequency range of 0.5-5 rad/s. From Fourier transform analysis, the fifth or even the seventh order harmonic could be observed at large applied strains. From stress decomposition analysis or Lissajous curves, inter-cycle elastic softening, or type I behavior, was observed for all films as the strain increases, while intra-cycle strain hardening occurred at strains in the LAOS regime. Overall, as acid content increases, it was found that the trend in elasticity under large applied strains agreed very well with the trend in cohesive strength of the films. [Preview Abstract] |
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