Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session A11: Thin Films Surface Flows and Interfaces IRecordings Available
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Sponsoring Units: DFD Chair: Vivek Sharma, University of Illinois Chicago Room: McCormick Place W-181B |
Monday, March 14, 2022 8:00AM - 8:12AM |
A11.00001: Bending a floating film using capillary forces Lauren A Dutcher, Carmen L Lee, Angela Moskal, Kari Dalnoki-Veress Thin polymeric films have important applications including coatings for microelectronic devices. To study these nanoscale systems, we investigate the deformation of a floating glassy film where the inclusion of a liquid/solid contact line on top of the floating film introduces a capillary tug. The system is constructed by preparing a nanometric glassy film, which floats atop a thin supported liquid film. A third liquid film partially covers the assembly introducing the contact line boundary. Thus, at the stepped transition from a bilayer to a trilayer, the topmost liquid layer exerts a capillary pressure on the rigid layer. The contact line perturbs the rigid layer and in this geometry the bending of the intermediate rigid film mitigates the role of capillarity in a way that has not been previously studied. Atomic force microscopy is used to visualize the topology of these samples at the stepped border. |
Monday, March 14, 2022 8:12AM - 8:24AM |
A11.00002: Surface Tension of Binary Systems: Role of Polarity Nusrat Ahmad, Aleksey Baldygin, Raymond Sanedrin, Prashant R Waghmare The effect of polar and dispersive components on the spreading of a liquid on a solid substrate has long been established through numerous experimental as well as theoretical studies. This study demonstrates similar hypothesis for liquid-fluid interface verifying that the polar and dispersive components of the liquid and the vapor phases strongly effect the equilibrium surface tension of a binary system. In the case of volatile binary systems, the high mass flux across the liquid-vapor interface gives rise to substantial inaccuracies in surface tension measurements. We have developed a standard protocol for a wide range of liquid-vapor combinations, i.e., polar-polar, polar-nonpolar and nonpolar-nonpolar, which ensures accurate measurement of the surface tension. In doing so, we observed that the surface tension varies only if the molecular weight of vapor phase is lower than the liquid phase, which is not the case with a combination where the vapor phase is molecularly heavier. |
Monday, March 14, 2022 8:24AM - 8:36AM |
A11.00003: Nonequilibrium Thermodynamics of Multi-Component Interfaces Phillip M Rauscher, Hans C Oettinger, Juan De Pablo Interfacial thermodynamics has important implications for determining boundary conditions of crucial biological and industrial processes. We have developed a theory of local equilibrium for multi-phase multi-component interfaces that builds upon the "sharp" interface first introduced by Gibbs, allowing for a description of nonequilibrium interfacial transport. By requiring that the thermodynamics is insensitive to the precise location of the dividing surface, we identify conditions for local equilibrium and then use extensive, high-precision nonequilibrium molecular dynamics (NEMD) simulations to test these conditions, establishing the validity of the local equilibrium hypothesis at interfaces. In particular, we demonstrate that equilibrium equations of state for select observables can be used to determine interfacial temperature and chemical potential(s) which are consistent with nonequilibrium generalizations of the Clapeyron and Gibbs adsorption equations. These results hold even far from equilibrium in the presence of heat and/or mass fluxes, thereby providing a thermodynamic foundation and computational tools for studying a wide variety of interfacial transport phenomena. |
Monday, March 14, 2022 8:36AM - 8:48AM |
A11.00004: Growth and Coalescence of Nanoscopic Mesas in Stratifying Micellar Foam Films Chenxian Xu, Yiran Zhang, Subinur I Kemal, Vivek Sharma Freestanding films of soft matter exhibit stratification due to confinement-induced structuring and layering of supramolecular structures like micelles. Stratification in micellar films proceeds by the growth of thinner domains at the expense of surrounding thicker film, and local volume conservation leads to the formation of nanoscopic ridges at the moving front. The ridge often undergoes an instability leading to nucleation of nanoscopic mesas, that grow and coalesce over time along the moving front. The shape and size of ridges and mesas in stratifying films are visualized and analyzed using interferometry, digital imaging, and optical microscopy (IDIOM) protocols, with unprecedented high spatial (thickness < 100 nm, lateral ~500 nm) and temporal resolution (< 1 ms). In this contribution, we analyze the shape evolution and coalescence of mesas in an effort to develop a comprehensive understanding of drainage by stratification in micellar foam films, including the role played by the contribution of supramolecular oscillatory structural forces to disjoining pressure. |
Monday, March 14, 2022 8:48AM - 9:00AM |
A11.00005: Intrinsic Stress Network and the Perception of Surface Tension Li Shen, Muhammad Rahman, James Ewen, Daniele Dini, Edward R Smith The evolution of the intrinsic liquid-vapour interface of a Lennard-Jones fluid owing to temperature variation is examined through molecular dynamics simulations employing the intrinsic sampling method (ISM) with a moving frame of reference. Results suggest, in good agreement with capillary wave theory, clear dampening effect on the density profiles as temperature increases. Further to this, an increase in temperature consequences in a decrease in the space filling nature (fractal dimension) of the stress-clusters at the surface. A percolation analysis of these clusters indicates that a surface at a higher temperature is more disconnected in terms of stress-field, and it is precisely this fragile nature of the surface that results in an overall lower surface tension. |
Monday, March 14, 2022 9:00AM - 9:12AM |
A11.00006: Dynamics of colloidal and viscous soap films: the role of viscosity Phalguni Shah, Eleanor Ward, Srishti Arora, Michelle R Driscoll A Newtonian soap film ruptures on the timescale of milliseconds, and at a constant rate known as the Culick velocity. Here, we explore the rupture of colloidal suspension films, in order to access a range of flow behavior by varying colloidal volume fraction. Using a high-speed camera, we systematically studied rupture dynamics for volume fractions ranging from 0 to 0.5, where the films contained a minimal amount of surfactant. Films were formed by stretching a known fluid volume to a specific size on a custom film stretcher. Surprisingly, even at high volume fraction, the rupture opened at a constant rate that was slower than the Culick velocity for water films. To investigate the role of Newtonian effective viscosity in this decrease in rupture speed, we conducted experiments on glycerol-water soap films. Over two orders of magnitude increase in fluid viscosity, the rupture speed was observed to decrease. As we used constant fluid volumes to form films, we hypothesize that the film thickness profile is a function of fluid viscosity. To test this hypothesis, we estimated the film thickness using dye absorption, and verify it using interferometry. |
Monday, March 14, 2022 9:12AM - 9:24AM |
A11.00007: Dynamics of capillary replacement between two mutually immiscible liquids on an open channel Hiroki Yasuga, Ko Okumura Capillarity-driven microfluidic devices have been receiving considerable attention in engineering and medical applications [1]. Almost all previous capillarity-driven microfluidic devices involve spontaneous flow of a single liquid. In recent years, the spontaneous replacement between two mutually immiscible liquids has begun to receive attention and is expected to be applied to droplet microfluidics [2]. However, the physical understanding of the replacement is still premature for microfluidic implementation. At the last APS March meeting, we reported the preliminary results of the replacement of aqueous solution with oil on open channels, which were fabricated by a digital light processing 3D printer. This time, we report a quantitative analysis of the dynamics of the capillary replacement using an improved experimental system. |
Monday, March 14, 2022 9:24AM - 9:36AM |
A11.00008: Interfacial dynamics of a two-layer thin film Ensela Mema, Linda J Cummings, Lou Kondic Stability properties of thin films on solid substrates are relevant in industrial applications such as coating and drying processes. They help researchers develop methods to stabilize thin films or to break thin films in a controlled manner. While the dynamics of film rupture of one layer systems have been thoroughly investigated, the stability properties of two layer systems are more complex as a result of the coupled interactions between the liquid-liquid and liquid-gas interfaces. This work focuses on developing a mathematical model that describes the evolution of two liquid layers of different viscosities on a solid substrate. We use the long-wave approximation scalings to obtain the evolution equations for the liquid-liquid and liquid-gas interfaces where the viscosity ratio of the two liquid layers is $O(\epsilon^2)$. Analytical methods such as linear stability analysis are used to gain insight into the stability of each layer. |
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