Bulletin of the American Physical Society
74th Annual Meeting of the APS Division of Fluid Dynamics
Volume 66, Number 17
Sunday–Tuesday, November 21–23, 2021; Phoenix Convention Center, Phoenix, Arizona
Session T20: Microscale Flows: Mixing and Chemical Reactions & Microscale Flows: Non-Newtonian Fluids |
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Chair: Vivek Narsimhan, Purdue Room: North 221 AB |
Tuesday, November 23, 2021 12:40PM - 12:53PM |
T20.00001: Hydrogel triggered liquid-liquid phase separation in ternary mixtures Etienne Jambon-Puillet, Andrej Kosmrlj, Pierre-Thomas Brun Liquid-liquid phase separation (LLPS) is ubiquitous in nature and engineering. In mundane situations, mixing Ouzo and water yields spontaneous emulsification, while similar demixing effects are used to manufacture porous membranes. Furthermore, LLPS have been shown to underly the formation of membraneless compartments in cells. While bulk phase separation has received most of the attention in recent years, the influence of surfaces on this complex physico-chemical processes remains poorly understood. Here, we study the phase separation of a ternary water-oil (DEP)-ethanol mixture on the surface of a hydrogel. The absorption of ethanol and release of water from the hydrogel perturbs the chemical composition locally, triggering the phase separation on the hydrogel surface and the formation of a phase separated layer. We analyze the dynamics of this process in a simplified Hele-Shaw geometry and draw the parallel between liquid-liquid phase separation and the surface induced solidification of a melt, or Stefan problem. |
Tuesday, November 23, 2021 12:53PM - 1:06PM |
T20.00002: Green CO2 Capture using Waste Concrete and Natural Seawater Abhishek Ratanpara, Mazen Hafez, Mahyar Ghazvini, Myeongsub Kim Global warming associated with rising CO2 concentrations in the atmosphere has become one of the most critical issues. Carbone capture and storage (CCS) is promising technology to mitigate the global warming. In this research, a new method of CO2 mineralization is proposed. In the microfluidic device, CO2 is captured in the seawater at ambient pressure. Further, the solution is exposed to minerals extracted from waste concrete, which can react with carbonate ions and precipitate carbonate minerals. Minute analysis of CO2 dissolution and the chemical reaction of minerals and carbonate ions in seawater is viable in a microfluidic device with a controlled environment. The use of seawater in our method lessens the heavy demands of freshwater in the conventional method. Additionally, utilizing waste concrete makes the CO2 capture process economical. Preliminary results show that the CO2 dissolution capacity of seawater is similar to freshwater with a negligible difference. Around 3% of CaO and other minerals are found in the few samples of waste concrete in the XRD analysis. These minerals are precipitated as carbonated minerals by reacting with CO2, which can be helpful in the growth of marine life like coral reefs and seashells. |
Tuesday, November 23, 2021 1:06PM - 1:19PM |
T20.00003: Towards a theory of soft hydraulics of complex fluids flows through compliant conduits Ivan C Christov Microfluidic devices manufactured from soft polymeric materials have emerged as a paradigm for cheap, disposable and easy-to-prototype fluidic platforms for integrating chemical and biological assays and analyses. The interplay between the flow forces and the inherently compliant conduits of such devices requires careful consideration. Mechanical compliance of these devices has now become a paradigm, enabling new approaches to microrheological measurements, new modalities of micromixing, and improved sieving of micro- and nano-particles, to name a few applications. While the theory of soft hydraulics of Newtonian fluid flows through compliant conduits has matured, the case of complex fluids remains largely open due to a lack of both theoretical and experimental results. In this talk, I will describe how to construct tractable, reduced models of soft hydraulics of complex fluids, taking into account their shear-dependent viscosity, the hydrodynamic pressure gradients during flow, and the elastic response (bulging and deformation) of the soft conduits due to flow within, including the effect of cross-sectional conduit geometry on the resulting fluid--structure interaction. First, the relationship between volumetric flow rate and axial pressure gradient is needed. This relationship is challenging (or impossible) to obtain in closed analytical form for most non-Newtonian fluids with shear-dependent viscosity. Notable exceptions are the power-law and Ellis models for the effective viscosity. Then, the channel height or tube radius in the pressure gradient--flow rate relation is to be replaced with an expression, suitably derived from the theory of elasticity, that accounts for the pressure-induced deformation of the height/radius of the conduit. Then, the entire 3D coupled, multiphysics problem is reduced to a single ODE, which can often be turned into a quadrature. |
Tuesday, November 23, 2021 1:19PM - 1:32PM |
T20.00004: A high throughput method to measure shear viscosity of bilayer membranes reveals shear-thinning and charge-dependence Hammad A Faizi, Rumiana Dimova, Petia M Vlahovska Lipid bilayers are the main structural component of cell membranes. The nanometrically thin bilayer behave as a two-dimensional fluid and its shear viscosity controls the transport of embedded biomolecules and membrane deformation. In this study, we devise a high throughput and non-invasive method to measure shear surface viscosity of bilayer membranes based on transient deformation of giant vesicles (closed membrane sacs) in an uniform electric field. Our method is probe-free and sensitive enough to allow for robust measurement of membrane viscosity of single-and multi-component lipid and polymer membranes. The amassed data reveals that homogeneous membranes of liquid disordered and ordered phase are Newtonian fluids while phase separated bilayer membranes and polymersomes exhibit shear thinning behavior. Surprisingly, we find that shear surface viscosity depends on the imbalance of the induced surface charges on the opposite membrane surfaces. This has important implications for biomolecular transport in living cell membranes that are intrinsically charged due to a transmembrane potential. |
Tuesday, November 23, 2021 1:32PM - 1:45PM |
T20.00005: Nanostructured Complex Fluids for Biofilm Removal Marcel M Louis, Antonio Perazzo, Mohamed Labib, Howard A Stone Effective methods for cleaning surfaces are of increasing importance in the healthcare sector. Medical instruments such as endoscopes and various tubes for dental and medical procedures are continuously susceptible to cross-contamination and biofilm formation as these devices are typically reused from patient to patient. Complex fluids such as micro-fibrillated cellulose are particularly useful in this application of cleaning as its heterogeneous structure has been shown in our experiments to be effective in removing both adhered particles and bacteria from surfaces. The goal of this study is to understand the role of the normal and wall shear stresses on cleaning and how altering parameters such as strain rate and cellulose fiber concentration affects the cleaning process. The main component of our experimental model is a rectangular microchannel made of PDMS and a glass slide, where we can control the flow rate, and hence the wall shear rate, for different choices of fluids, whose rheology we measure. In particular, we culture bacterial (Staphylococcus aureus) biofilms on the glass side of a channel and, using fluorescent microscopy, observe biofilm removal by the flow. Finally, we characterize the flow field and cleaning as a function of time with the use of particle image velocimetry (PIV) and other image analytical techniques. |
Tuesday, November 23, 2021 1:45PM - 1:58PM |
T20.00006: Experimental and theoretical studies of cross-stream migration of non-spherical particles in a quadratic flow of viscoelastic fluid Cheng-Wei Tai, Shiyan WANG, Vivek Narsimhan Particulate suspension in a viscoelastic fluid is common in industrial applications and in the fields of microbiology and microrheology. When in a quadratic flow, particles migrate in the lateral direction due to the imbalance of normal stress over the particle surface. A detailed understanding on the migration and rotation behavior of non-spherical particles within such system will be vital to developing precise particle manipulation and separation techniques. |
Tuesday, November 23, 2021 1:58PM - 2:11PM |
T20.00007: Microscale fluid structure interactions of non Newtonian fluids peeling a linearly elastic sheet Anirudh Venkatesh, Vishal Anand, Vivek Narsimhan In this study, we investigate the transient fluid structure interactions (FSI) of a non-Newtonian fluid peeling a Hookean sheet at low Reynolds numbers (Re) .The rheology of the fluid is rendered by the simplified Phan-Thien-Tanner (sPTT) model. Invoking the lubrication approximation for fluid flow and considering the relative time scale for deformation and the relaxation time of the polymer, we solve a reduced problem for the evolution of the deformed height in time and space. An order of magnitude analysis of the resultant equation reveals two distinct regimes of peeling, based on the relative magnitude of the viscoelasticity and FSI parameters, further aided by similarity solutions. On inspecting the numerical solution, we infer that the non-Newtonian nature plays a pivotal role in bringing the system to a steady state faster in comparison to a Newtonian fluid. This inference, in turn, further motivates us to investigate the dynamics of peeling actuated by purely shear thinning fluids. Some preliminary results for the peeling actuated by such generalized Newtonian fluids are also presented. To conclude, this study aims to afford to the experimentalist a system of knowledge to a priori delineate the peeling characteristics of a certain class of complex fluids. |
Tuesday, November 23, 2021 2:11PM - 2:24PM |
T20.00008: A micro-reactor based on opposed-jet configuration: flow features and chemical reaction Sara Tomasi Masoni, Matteo Antognoli, Chiara Galletti, Alessandro Mariotti, Roberto Mauri, Maria V Salvetti, Elisabetta Brunazzi Microreactors are very attractive for a wide range of applications, spanning from lab-on-chip to nanoparticle production or chemical reactions. For the latter, they ensure a continuous operation with large heat transfer, thus enabling significant intensification of many pharmaceutical and fine-chemistry processes with respect to conventional batch reactors. Although very complex geometries have been proposed in the literature to trigger the mixing of reactants in the laminar flow conditions occurring in microfluidic devices, simple designs are preferred to facilitate microfabrication and avoid fouling. |
Tuesday, November 23, 2021 2:24PM - 2:37PM Not Participating |
T20.00009: Impact of flow regimes and chemical kinetics on the reaction progress in a T-shaped microreactor Maria V Salvetti, Alessandro Mariotti, Sara Tomasi Masoni, Matteo Antognoli, Chiara Galletti, Elisabetta Brunazzi, Roberto Mauri Microreactors show very promising features for improving the sustainability of many pharmaceutical and fine-chemistry processes. Indeed, they enable continuous operation with unprecedented control over operating conditions thanks to the very high heat transfer rates stemming from the large surface-to-volume ratio. With such characteristics, higher reaction yields than conventional batch processes may be typically obtained with less material and energy consumption. |
Tuesday, November 23, 2021 2:37PM - 2:50PM |
T20.00010: Transient Membrane Kinematic Model for Viscoplastic Fluids: Periodic Contraction in the Microchannel Dinesh Singh S Bhandari, Dharmendra Tripathi, Vamsi Krishna Narla A coupled model of viscoplastic fluid and membrane contraction mechanism is presented mathematically. The time-dependent wall deformation due to membrane motion through the microchannel is retained in the analysis. Further, we examined the rheological effects on flow analysis, pressure distribution, wall shear stress, and discuss their importance for the physiological transport phenomena. In the membrane pumping mechanism, the expansion and compression phases are used for the micropump actuator simulation. Propagation of membrane as a motion of actuation is embedded in the middle of the microchannel. With the creeping nature of physical transport, a lubrication approach has been used. An analytical approach is adopted to derive the closed-form solutions. Numerical results indicate that the flow characteristics and pumping characteristics are significantly affected by the plasticity of the fluids and membrane shape. Such results provide the initial idea for designing the novel micro-valveless pumping actuator to control the microscale transport phenomena of physiological systems. |
Tuesday, November 23, 2021 2:50PM - 3:03PM |
T20.00011: Normal force induced by viscoelastic flow between confined surfaces Xin Zhao, Xu Zheng, Dongshi Guan Particle dynamics and lubrication flows for a particle moving near a confining boundary in viscoelastic surrounding are widely encountered and of essential significance in biophysics, nature and engineering application. Different from normal force of confined particle in viscous fluid caused by geometry and inertial effect in high Reynolds number, viscoelastic fluid under shear shows normal stress. In this talk, we aim to clarify the elasticity-induced normal force and justify the contributions from elastic effect and soft boundary. Our study focuses on flow in small Re while Wi number is in a wide range from 0.05 to 10. Large elastic effect will be introduced for large elasticity number El = Wi / Re >> 1. We deduce a theoretical expression of elasticity-induced normal force based on scaling analysis and numerical simulation, which unveils major factors dominating normal force and characteristic length scale. The analysis is further applied to the situations with the presence of a soft boundary, and we show normal force in viscoelastic fluid can be in magnitude dominant to that of elastohydrodynamic one in micro- and nanofluidic. Overall, our findings could provide helpful insights to understand nonintuitive migration behaviors of particles in various biophysical applications. |
Tuesday, November 23, 2021 3:03PM - 3:16PM |
T20.00012: Measuring Young's Modulus of soft gels in a planar microfluidic device via simple clogging Charles P Moore, Julien Husson, Arezki Boudaoud, Gabriel Amselem, Charles Baroud Measuring the elastic modulus of soft gels usually requires complex micro-pipette aspiration or atomic force microscopy, two complex methods. Here we investigate the deformation of a soft hydrogel particle when it is aspirated into a high aspect ratio slit as a way to measure its Young's modulus. This geometry provides a simple analog to micro-pipette aspiration that can be implemented using microfluidic channels. Using a single layer microfluidic chip with a bypass line microgels are trapped and forced into a narrow constriction. PIV is used to measure the amount of flow passing in the bypass and through-pass channels. The ratio of these flow rates provides a measurement of the resistance of the hydrogel to flow as it is squeezed through the slit. The deformation of the soft particle is also measured, thus providing a relationship between the forcing pressure and deformation for different elastic properties and particle and slit sizes. These measurements are collapsed onto a master curve by comparing with a Herzian contact model for a rectangular hold, which yields a value of the elastic modulus of the particles. |
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