Electrohydrodynamic Instability of Two Thin Viscous Leaky Dielectric Fluid Films in a Porous Medium

El-Sayed, M. F.; Moussa, M. H. M.; Hassan, Ahmed A. A.; Hafez, N. M.

doi:10.5402/2011/498718

Cited by 8 publications

(13 citation statements)

References 27 publications

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“…The instabilities induced by van der Waals force − and externally applied electric field − in thin films have emerged as potential techniques to engineer periodic micro/nano structures. These patterns find diverse applications in variety of areas including optoelectronic devices, drug delivery, microfluidics, and patterned functional surfaces, among others.…”

Section: Introductionmentioning

confidence: 99%

Electric-Field-Induced Instabilities in Thin Liquid Trilayers Confined between Patterned Electrodes

2012

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Electric-field-induced instabilities of trilayer of immiscible thin films confined between both planar and patterned electrodes have been explored by the linear stability analysis (LSA) and the long-wave nonlinear simulations. The twin liquid–liquid interfaces of a trilayer can undergo either in-phase bending or antiphase squeezing or mixed modes of evolution. The linear and nonlinear analyses together uncover the conditions under which these modes evolve and subsequently form an array of interesting, complex patterns. The study confirms that when the middle layer is of the highest or lowest dielectric permittivity than the other layers the interfaces undergo a squeezing mode of deformation. In other cases, the interfaces evolve in the bending mode, except for the situations where the linear growth coefficient versus wavenumber curves in the LSA show a bimodal behavior and the interfaces evolve in a mixed mode. The LSA also highlights the importance of the ratios of the thermodynamic parameters such as thicknesses, dielectric permittivities, and interfacial tensions of the films in altering the length and time scales. Importantly, variation in the kinetic parameters such as the ratio of the viscosities of the films can also alter the modes of evolution, relative amplitudes of deformation, and morphologies at the interfaces. Nonlinear simulations under spatially varying electric fields uncover several intriguing self-organized periodic microstructures such as composite core–shell columns, pin-cushion-like structures, membranes with ordered pores, and arrays of open/closed embedded/encapsulated microchannels and microdroplets. Examples of miniaturization of patterns employing patterned electrodes with periodicity less than the spinodal length scales are also shown.

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Section: Introductionmentioning

confidence: 99%

Electric-Field-Induced Instabilities in Thin Liquid Trilayers Confined between Patterned Electrodes

2012

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“…Numerical accuracy and convergence were checked by varying the number of grid points. The electric field can be obtained by solving the analytical equation (9). A van der Waals-like repulsive force is imposed on the top electrode and substrate to prevent the airfilm interface from penetrating the upper electrode.…”

Section: Presentation Of the Simulation Modelmentioning

confidence: 99%

“…Numerous theoretical and experimental works have been carried out to understand this phenomenon [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. These studies are mainly based on linear stability analysis, whereas the dynamic evolution process of the interface growth can be studied by nonlinear simulation.…”

Section: Introductionmentioning

confidence: 99%

Faithful replication of grating patterns in polymer through electrohydrodynamic instabilities

Yu¹,

Wang²,

Zhang³

et al. 2014

J. Micromech. Microeng.

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Electrohydrodynamic instability patterning (EHDIP) as an alternative patterning method has attracted a great deal of attention over the past decade. This article demonstrates the faithful transfer of patterns with a high aspect ratio onto a polymer film via electrohydrodynamic instabilities for a given patterned grating mask. We perform a simple mathematical analysis to determine the influence of process parameters on the pressure difference ∆P. Through numerical simulation, it is demonstrated that thick films subject to large electric fields are essential to realize this faithful replication. In particular, the influence of the material properties of the polymer on pattern replication is discussed in detail. It is found that, to achieve the smaller periodic patterns with a higher resolution, film with a larger value of the dielectric constant and smaller value of the surface tension should be chosen. In addition, an ideal replication of the mask pattern with a short evolution time is possible by reducing the viscosity of the polymer liquid. Finally, the experiments of the pattern replication with and without defects are demonstrated to compare with the numerical simulation results. It is found that experiments are in good agreement with the simulation results and prove that the numerical simulation method provides an effective way to predict faithful replication.

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“…Surface charges are crucial in such cases, as conduction in the interface area plays a significant role in many electrical systems. El-Sayed et al [21] investigated the influence of an applied electric field on the stability of an interface between two thin viscous leaky dielectric fluid layers in a porous medium within the long-wave limit. In addition, they performed a linear stability analysis of a two-dimensional incompressible leaky dielectric viscous liquid sheet surrounded by a hydrodynamically passive conducting medium when an electric field is applied parallel to the originally flat bounding fluid boundaries, admitting surface charges as well [22].…”

Section: Introductionmentioning

confidence: 99%

Electroviscoelstic Stability Analysis of Cylindrical Structures in Walters B Conducting Fluids Streaming through Porous Medium

Metwaly

Hafez

2022

Fluids

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In this research, the linear stability of a cylindrical interface between two viscoelstic Walters B conducting fluids moving through a porous medium is investigated theoretically and numerically. The fluids are influenced by a uniform axial electric field. The cylindrical structure preserves heat and mass transfer across the interface. The governing equations of motion and continuity are linearized, as are Maxwell’s equations in quasi-static approximation and the suitable boundary conditions at the interface. The method of normal modes has been used to obtain a quadratic characteristic equation in frequency with complex coefficients describing the interaction between viscoelstic Walters B conducting fluids and the electric field. In light of linear stability theory, the Routh–Hurwitz criteria are used to govern the structure’s stability. Several special cases are recoverd under suitable data choices. The stability analysis is conferred in detail via the behaviors of the applied electric field and the imaginary growth rate part with the wavenumbers. The effects of various parameters on the interfacial stability are theoretically presented and illustrated graphically through two sets of figures. Our results demonstrate that kinematic viscosities, kinematic viscoelasticities, and medium porosity improve stability, whereas medium permeability, heat and mass transfer coefficients, and fluid velocities decrease it. Finally, electrical conductivity has a critical influence on the structure’s stability.

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Electrohydrodynamic Instability of Two Thin Viscous Leaky Dielectric Fluid Films in a Porous Medium

Cited by 8 publications

References 27 publications

Electric-Field-Induced Instabilities in Thin Liquid Trilayers Confined between Patterned Electrodes

Electric-Field-Induced Instabilities in Thin Liquid Trilayers Confined between Patterned Electrodes

Faithful replication of grating patterns in polymer through electrohydrodynamic instabilities

Electroviscoelstic Stability Analysis of Cylindrical Structures in Walters B Conducting Fluids Streaming through Porous Medium

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