Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session D11: Thin Films Surface Flows and Interfaces IIIRecordings Available
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Sponsoring Units: DFD Chair: Felipe Jimenez, Northwestern University Room: McCormick Place W-181B |
Monday, March 14, 2022 3:00PM - 3:12PM |
D11.00001: Ionic and compositional effects on phospholipid thin film formation and stability Oscar Zabala-Ferrera, Peter J Beltramo Membrane fusion and adhesion are ubiquitous processes in biological cells that are vital to cell function. Phospholipid membranes and thin films suspended in water provide insight into lipid membrane interactions based on the presence of mono or divalent cations (Na+, Ca2+), altered ionic concentrations, and chemical properties of the lipid constituents. Of specific interest is the role of phosphatidylethanolamine (PE), which initiates membrane fusion in the presence of Ca2+. In this work, we create free-standing lipid films in water to investigate interleaflet headgroup interactions as opposing lipid monolayers come close together, mimicking membrane adhesion. We perform disjoining pressure isotherm experiments to shed light on the effect of salt concentration on close-range (<10nm) interactions between leaflet headgroups and the final newton black film thickness. A stepwise increase in film thinning is also done to explore dynamic film evolution. These experiments provide insight into the stability (coalescence time, drainage characteristics) of lipid headgroups in altered environments. We present results for DOPC films with varying aqueous buffer characteristics, then investigate DOPE to better understand the effect of Ca2+ on monolayer headgroup-headgroup interactions. |
Monday, March 14, 2022 3:12PM - 3:24PM |
D11.00002: Relationship between viscosity and acyl tail dynamics in lipid bilayers Michihiro Nagao, Elizabeth G Kelley, Antonio Faraone, Makina Saito, Yoshitaka Yoda, Kurokuzu Masayuki, Shinichi Takata, Makoto Seto, Paul D Butler Membrane viscosity is a fundamental property that controls transport phenomena within two-dimensional biological membranes. To better understand the molecular origins of membrane viscosity, we employed quasi-elastic x-ray and neutron scattering techniques to access coherent lipid acyl tail correlation dynamics over time scales from several ps to hundreds of ns. In the fluid phase of dimyristoyl phosphocholine bilayers, two relaxation processes are observed with the relaxation times of ≈ 30 ps and ≈ 500 ps. The fast relaxation was attributed to density fluctuations of the lipid acyl tails while the slow mode was assigned to lipid molecular rearrangements. These two modes became a heterogeneous single mode with relaxation times of 10s to 100s of ns when the temperature was decreased to the lipid gel phase. Based on the relationship between density fluctuations and viscosity in three-dimensional molecular liquids, we estimated the two-dimensional membrane viscosity both in the lipid fluid phase and in the gel phase. The estimated membrane viscosity values were in the middle of a broad distribution of reported values in the fluid phase and increased by an order of magnitude larger in the vicinity of the melting transition temperature in the gel phase. |
Monday, March 14, 2022 3:24PM - 3:36PM |
D11.00003: Taylor dispersion of finite-sized particles near a boundary Joshua D McGraw, Alexandre Vilquin, Vincent Bertin, Thomas Salez Brownian objects moving in a shear flow undergo an advection-diffusion coupling typically called Taylor dispersion. Such diffusive objects are normally treated as point-like and the walls are considered as passive reflectors. At nanoscales, however, the size of the dispersed objects and their energetic interactions with the confining boundaries should not be neglected. Through the use of evanescent wave microscopy, we here study the motion of fluorescent nanoparticles in linear shear flow near a plane boundary. By varying the concentration of electrolyte, we show how the electrostatic and hydrodynamic interaction between the particles and the surface affects the dispersion. In particular by varying the salt concentration, we measure a large dispersion increase when the electrostatic repulsion decreases. These results, in agreement with numerical simulations and existing theories, highlight the crucial role of hydrodynamic and energetic particle-surface interactions during Taylor dispersion at nanoscales. |
Monday, March 14, 2022 3:36PM - 3:48PM |
D11.00004: Interfacial Properties of Per- and Polyfluoroalkyl Substances (PFAS) at Air-water Interface Muchu Zhou, Zahra Abbasian Chaleshtari, Reza Foudazi Per- and polyfluoroalkyl substances (PFAS) are a group of man-made chemicals that are used in everyday products such as non-stick cookware, carpets, textiles, cleaning products, coatings, and firefighting foam. The PFAS have been detected almost everywhere in the U.S., particularly in water resources. More importantly, they are harmful and accumulate in our bodies. Therefore, PFAS contamination has become a major concern. PFAS have unique properties, for instance, high thermal and chemical stability and lowering the surface tension due to possessing a hydrophobic fluorinated tail and a hydrophilic head group in their structure. Therefore, they can accumulate at the air-water interface, which is regarded as the main retention source of PFAS transport in the environment. In the present work, we study the interfacial properties of PFAS with different chain lengths adsorbed at the air-water interface. Furthermore, we investigate the kinetics and equilibrium adsorption of PFAS along with the effect of salts and cosurfactants on PFAS adsorption at the air-water interface. |
Monday, March 14, 2022 3:48PM - 4:00PM |
D11.00005: Marangoni instabilities in spreading of polymer solutions on a suspended liquid film Melika Motaghian, Thiemo van Esbroeck, Erik van der Linden, Mehdi Habibi Spreading of multi-component droplets is a rich physics phenomenon that has attracted much attention in the past years. Particularly because of its prevalent presence in many technological applications like those involving coating, surface cleaning, surface patterning, material deposition, and many others. Here, we report a novel instability that occurs during the spreading of a polymer-surfactant solution on a soap film. We previously have shown that after deposition of a droplet on a soap film, the droplet forms a new suspended layer in the center of a soap film. When the droplet's surface tension is lower than the soap film, a rapid spreading takes place in the order of milliseconds. Such geometry enables us to study the spreading behavior of liquids in the absence of high shear viscous forces induced by solid boundaries. When the deposited droplet is a polymer solution, the spreading dynamics can show instabilities. We show that at low polymer concentration, the spreading front remains stable and perfectly circular. However, above the entanglement concentration of the polymers, it destabilizes into a daisy shape pattern. We discovered that the enhanced elastic response of the solution due to the formation of polymer networks triggers the instabilities. We introduce a critical length scale based on balancing elastic and capillary forces which its growth rate perfectly predicts the onset of the instability. |
Monday, March 14, 2022 4:00PM - 4:12PM |
D11.00006: Molding, Patterning and Driving Liquids with Light Feng Lin, Aamir Nasir Quraishy, Runjia Li, Guang Yang Guang Yang, Mohammadjavad Mohebinia, Tian Tong, Yi Qiu, Talari Vishal Talari Vishal, Junyi Zhao, Wei Zhang, Hong Zhong, Hang Zhang, Chaofu Zhou, Xin Tong, Peng Yu, Jonathan Hu, Suchuan Dong, Dong Liu, Zhiming Wang, John R. Schaibley, Jiming Bao When a laser beam induces surface tension gradient at the free surface of a liquid, a weak surface depression is expected and has been observed. Here we report giant depression and rupture in “optothermocapillary fluids” under the illumination of laser and sunlight. Computational fluid dynamics models were developed to understand the surface deformation and provided desirable physical parameters of the fluid for maximum deformation. New optothermocapillary fluids were created by mixing transparent lamp oil with different candle dyes. They can be cut open by sunlight and be patterned to different shapes and sizes using an ordinary laser show projector or a common laser pointer. Laser driving and elevation of optothermocapillary fluids, in addition to the manipulation of different droplets on their surface, were demonstrated as an efficient controlling method and platform for optofluidic operations. The fundamental understanding of light-induced giant depression and creation of new optothermocapillary fluids encourage the fundamental research and applications of optofluidics. |
Monday, March 14, 2022 4:12PM - 4:24PM |
D11.00007: Condensation Experiments on Wettability-Patterned Surfaces in the Absence of Non-Condensable Gases George Damoulakis, Mohamad Jafari Gukeh, Constantine M Megaridis Water vapor condensation is affecting many engineering applications, especially in the power industry. The main modes of this phenomenon are dropwise condensation (DwC) and filmwise condensation (FwC). In DwC, the condensate creates droplets that grow, coalesce and eventually get pulled by gravity to leave the surface, while in FwC, the condensate forms a liquid film. In terms of heat transfer rate, DwC's performance far exceeds that of FwC. DwC and FwC can be combined spatially on the same surface, with philic wedge-shape tracks facilitating FwC and capillary-driven condensate drainage, while the phobic background promotes DwC. This strategy is applied here in passive heat spreaders to effectively enhance their condensation heat transfer coefficient (HTC). An innovative experimental setup was designed and built to evaluate the HTC for wettability-patterned surfaces with diverse characteristics by generating water vapor and condensing it on a cooled wettability-patterned plate in an environment devoid of non-condensable gases. Significant differentiators for the investigated wettability-patterned surfaces include the ratio of philic to phobic domains, the length of the contrast line between the two wettabilities, the size and opening angle of the wedge track, and the number of low pressure wells where condensate accumulates before removal. |
Monday, March 14, 2022 4:24PM - 4:36PM |
D11.00008: An experimental procedure to quantify solid-liquid surface energy in wetting configurations Sreya Sarkar, Mohamad J Gukeh, Tamal Roy, Ranjan Ganguly, Constantine M Megaridis, George Damoulakis Wettability is correlated with the affinity between a solid and a liquid. Roughness is a primary factor affecting the wettability of a solid surface. When a droplet sitting on a surface is infused with more liquid (through a syringe or a small hole underneath the droplet), the droplet footprint begins to advance from its equilibrium position. During this motion, the droplet experiences a “pinning” force, analogous to the solid-solid frictional force, which opposes fluid motion; this force has its origins in the roughness of the surface. We perform experiments on different hydrophilic surfaces with varying degrees of topological roughness. We find that the pinning force during contact-line advancement increases linearly with surface roughness, and the slope of the line is equal to the surface energy between the solid and the liquid. This method reveals a new and simple way to predict the value of the solid-liquid surface energy for a wetting configuration. The experimental findings are elucidated using well-known arguments from wetting theory and contact angle hysteresis. |
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