Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session L32: Electrokinetic Transport II 
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Chair: Michael Booty, New Jersey Institute of Technology Room: 158AB 
Monday, November 20, 2023 8:00AM  8:13AM 
L32.00001: Electrokinetic Flow for a Drop Michael R Booty, Manman Ma, Michael Siegel A general, timedependent model is described for the induced charge electrokinetic flow in and near an electrolyte drop that is suspended in an external electrolyte solution. The model assumes a sharp interface that separates a pair of thin Debye layers with evolution on the timescale for chargeup of the layers by an impulsively applied electric field. The dynamics and behavior with respect to the influence of various effects and parameters are explored, with an emphasis on analytical results under conditions of small applied field strength. 
Monday, November 20, 2023 8:13AM  8:26AM 
L32.00002: Effect of finite Debye layer in electromigration TaylorAris dispersion of charged species in a thin channel Anirban Chatterjee, Ameeya K Nayak

Monday, November 20, 2023 8:26AM  8:39AM 
L32.00003: Application of Physics Informed Neural Networks (PINNs) on combined electroosmoticpressure driven flow Arshia Merdasi, Saman Ebrahimi Multiphysics involved in microelectromechanical systems (MEMS) is of great importance to analyze the fluid motion in biomedical and biotechnological applications, chemical synthesis, mixing and various other applications. We have implemented different architectures of physicsinformed neural networks (PINNs) to investigate the mixed electroosmotic pressure driven (EOF/PD) flow in microchannels with nonuniform zetapotential distribution on the walls. Through performing a detailed numerical simulation and PINN solutions based on PoissonBoltzmann, Laplace, NavierStokes, concentration, and energy equations, we have predicted the nonuniformly distributed zetapotential on the fluid dynamic, and heat transfer characteristics. It is found that there is a good agreement between the Finite Volume Method (FVM) and segregated PINN approach. From the grid point distribution effect on PINNs, we also demonstrate that using boundary layer collocation points can drastically improve the training efficiency and reduce the total loss for EOF/PD flow. Furthermore, comparing the PINN results with the numerical simulation for mixing index and Nusselt number variation, we present that applying a single PINN leads to higher training loss when compared to the multistructured PINN, where a PINN is separately trained for each governing equation. Specifically, the normalized mean absolute percentage errors in the velocity prediction of the single and segregated PINNs are 20.17% and 9.2% respectively. 
Monday, November 20, 2023 8:39AM  8:52AM 
L32.00004: Viscoelectric effect analysis in an electroosmotic flow with microchannel wall slip Edgar Ramos, Ian Guillermo Monsivais Montoliu, Federico Mendez, Jose Lizardi In the present work, we developed a numerical analysis for an electroosmotic flow circulating in a rectangular microchannel considering electrolyte viscosity as a function of the induced electric field; which is also reflected in the slip condition imposed on the system walls, since the slip length is a function of the fluid viscosity. It should be clarified this is an entirely hydrodynamic problem, and for this reason there are no induced pressure gradients, because we are in the presence of a purely electroosmotic flow, where the fluid motion is due only to electrokinetic forces. Based on these comments, the problem is centered on high induced potentials, enabling viscoelectric effect analysis in the electroosmotic flow, which leads to significant increases in velocity and volumetric flow profiles compared to the case where the viscosity is a constant and there is no slip condition. Due to analytical analysis limitations, we implemented a dimensionless equation scheme defined by the continuity equation, the momentum equations in the x and y direction, the PoissonBoltzmann equation, and the charge conservation equation to obtain the velocity and volumetric flow rate profiles mentioned above. This model is described in its variational form in order to implement the finite element technique using free software, FreeFem++. The results obtained show how the viscoelectric effect is relevant when working with high induced potentials; that is, for values of ζ>1, when the dimensionless viscoelectric parameter f increases, there is a significant decrease in the velocity profiles u, a situation that is not observed when ζ≤1, where there are low induced potentials, and for this reason, as the dimensionless parameter f increases, the velocity profiles remain constant. This condition is preserved for different values of the slip length δ. 
Monday, November 20, 2023 8:52AM  9:05AM 
L32.00005: A new Lattice Boltzmann application to plasma wakefield acceleration Daniele Simeoni, Gianmarco Parise, Fabio Guglietta, Mauro Sbragaglia, Alessandro Cianchi, Andrea Renato Rossi Plasma wakefiled consitutes a new technique in the field of particle acceleration, that promises same (or superior) energy gains w.r.t. conventional modernday methods, while being operated in more compact and less expensive physical structures. In this talk we present the first application of the Lattice Boltzmann (LB) method to the problem of plasma wakefield acceleration, where the relevant macroscopic equations can be recasted as advection equations. 
Monday, November 20, 2023 9:05AM  9:18AM 
L32.00006: Optimization of MultiElectrode Dielectric Barrier Discharge Arrays for Active Flow Control Anthony Tang, Benjamin Price, Nicholas Kirschbaum, Alexander Mamishev, Igor Novosselov Dielectric barrier discharge (DBD) plasma actuators for active flow control offer several advantages over conventional flow control techniques, including no moving parts, instantaneous response, and quiet operations. However, DBD actuators are limited to lowspeed applications and require further optimization. The addition of DBD in series electrodes can improve the thrust of and increase the area averaged the density of the overall system. Optimization of a multiDBD array requires adjusting AC phase shift and streamwise spacing over a range of applied voltages and frequencies. Direct thrust and fluid velocity measurements as a function of electrical parameters are presented for two and threestage arrays. A multiDBD array with outofphase AC electrodes provides significantly more thrust than previously reported multiDBD systems. It is found to scale well for geometric constraints. This optimization allows DBD plasma actuators to increase the trust density and modify a fluid system more effectively. 
Monday, November 20, 2023 9:18AM  9:31AM 
L32.00007: Convection Influences the Charging Dynamics of Porous Electrodes Alexander J Wagner, Aaron D Ratschow, Mathijs A Janssen, Steffen Hardt Electrolyteimmersed porous electrodes are essential for various electrochemical technologies and subject to ongoing research. Most theories for porous electrode charging consider only diffusion and electromigration as ionic charge transport mechanisms. However, the charging process can induce a fluid flow causing additional convective charge transport, whose influence on the charging dynamics of porous electrodes is unknown so far. Here, we simulate the charging using the fully coupled modified PoissonNernstPlanck and NavierStokes equations for a single cylindrical pore next to a reservoir. The simulations show that convection caused by an induced fluid flow can substantially speed up the charging of porous electrodes. Furthermore, we present a semiheuristic analytical model describing the induced fluid velocity and the electric current arising from convection. We demonstrate the model’s applicability for moderate applied potentials and that, in this regime, convection speeds up charging most for pore radii roughly ten times larger than the Debye length. Our results show that neglecting convective effects when studying the charging dynamics of porous electrodes is often not realistic, which opens a direction for future research. 
Monday, November 20, 2023 9:31AM  9:44AM 
L32.00008: Enhancing Conductivity of PEDOT:PSS by Blending PEO in Films and Jets: A Combined Ab Initio Modeling and Experimental Study Vitaliy Yurkiv, Xinnian Wang, Yong Kim, Farzad Mashayek, yayue pan, Alexander L Yarin The rapid advancement of innovative organicbased technologies has led to significant development of various electronic devices. Conducting polymers in blends with nonconducting polymers acquire viscoelasticity sufficient for direct ink writing (DIW) of conducting circuits on knitted and nonwoven materials. In this regard, poly(3,4ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) in blends with poly(ethylene oxide) (PEO) posses beneficial properties, excellent thermal stability and processability. In this study, a combination of ab initio modeling and experimental analysis is presented to investigate the electronic conductivity of composed PEDOT:PSS/PEO films. Ab initio DFT calculations are performed based on experimental data to unveil the band structure and density of states of the composite materials. Various polymer compositions with varying PEDOT, PSS, and PEO ratios are examined, revealing unexpected electronic properties of these polymer blends. Notably, the addition of PEO results in a significant change in the band gap, particularly near the maximum PEO content of 52 weight%. These findings are consistent with our own measurements of film conductivity. This combined modeling and experimental approach provides a mechanistic interpretation of the underlying reasons behind the variations in polymer blends conductivity and opens way for synthesizing highlyconducting polymers for extrusionbased manufacturing techniques such as DIW . 
Monday, November 20, 2023 9:44AM  9:57AM 
L32.00009: Microstructure and dynamic characteristics of electric double layer at montmorilloniteNaCl aqueous interface Yixuan Feng, Hongwei Fang, Yitian Gao, Jiale Han The microscopic structure of solidliquid interface is of widespread interest across the physical science, with electric double layer (EDL) playing a pivotal role in enhancing our understanding of macroscopic properties of liquid flow. In this study, we employ molecular dynamics simulations to analyze the structure and dynamic properties of liquids in montmorilloniteNaCl aqueous systems. Our focus lies on measuring the distributions of ions and hierarchical water clusters within the hydrogen bond network, providing a comprehensive overview of the liquid structure. 
Monday, November 20, 2023 9:57AM  10:10AM 
L32.00010: Interplay between metal deposition and electroconvection on a charge selective electrode Sungyeong Choi, Jeonghwan Kim, Minsang Kang, Rhokyun Kwak We investigate an unknown coupling effect between dendrite growth and electroconvective instability (EC), which arises from electrokinetic instability at the electrolyteelectrode interface. To achieve this, we design an in situ Operando microscopy platform that visualizes ion concentration, fluid flow, and dendrite growth at the electrodeelectrolyte (ZnZnSO4) interface. Based on the order of occurrence between EC and dendrite formations, we identified five distinct dynamic regimes: (i) inert regime where neither EC nor dendrites occur, (ii) EC regime exhibiting only EC, (iii) ECdendrite regime where dendrites form at current hotspots induced by EC, (iv) EC/dendrite regime where the both EC and dendrites simultaneously occur, and (v) dendrite regime where only dendrite forms. By incorporating the Damkohler number (ion reduction reaction vs. selfdiffusion on the electrode), electric Rayleigh number, and the second Damkohler number (ion diffusion from the electrolyte vs. ion reduction reaction on the electrode), we diversify the five dynamic regimes. Our study sheds light on the interplay between EC and dendrite formation, providing valuable insights for devising novel strategies to control dendrite growth. 
Monday, November 20, 2023 10:10AM  10:23AM 
L32.00011: Biomimetic membranes in electric fields: capacitive charging and stability Petia M Vlahovska, Shuozhen Zhao, Michael J Miksis Cells and cellular organelles are encapsulated by nanometrically thin membranes whose main component is a lipid bilayer. In the presence of electric fields, the ionimpermeable lipid bilayer acts as a capacitor and supports a potential difference across the membrane. We analyze the dynamics of a planar membrane separating bulk solutions with different electrolyte concentrations in an applied uniform DC electric field. The membrane is modeled as a zerothickness capacitive interface. The evolution of the evolution potential and ions distributions are solved for using the PoissonNernstPlanck equations. Asymptotic solutions are derived in the limit of thin Debye layers and weak fields (compared to the thermal electric potential). The effect of the field on the thermal fluctuations of a membrane is also considered. 
Monday, November 20, 2023 10:23AM  10:36AM 
L32.00012: Vortical structures of electroconvection on ionselective surfaces during the steadytochaotic transition Gwiyeol Kim, Rhokyun Kwak When an electric field is applied to an ionselective membrane, exclusive transport of positive or negative ions induces hydrodynamic instability, initiating electrokinetic flows known as electroconvection(EC). In this study, we directly observe convective states of EC during the steadytochaotic transition for the first time. By conducting a tomography scan with 3D confocal microscopy, we classify two hithertounknown states between two wellknown initial and final states: i) singlelayer steady EC, ii) doublelayer EC with steady primary and secondary vortices. iii) doublelayer EC with steady primary and chaotic secondary vortices, and iv) fully chaotic EC. First, as described in previous studies, singlelayer primary EC occurs on the membrane at the threshold voltage. Secondly, with increased voltage, smaller vortices arise between the larger primary vortices. These primary vortices lead to current hotspots between them, in which the influx of vortices presents towards the membrane. Consequently, in these hotspots, the ion flux and electric field become concentrated, inducing EC once again. Initially, this secondary EC is stable while keeping the balance with the primary EC. In the third state, however, the secondary EC becomes chaotic, spreading to the beneath primary EC and causing the current fluctuations of a finite value. Finally, when voltage is far beyond the threshold, both primary and secondary EC become chaotic. 
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