Fabrication of a novel liquid metal microelectrode in microfluidic chip

2021 ◽  
pp. 2140005
Author(s):  
Yanli Gong ◽  
Bei Peng ◽  
Xuan Weng ◽  
Hai Jiang
Keyword(s):  
Liquid Metal ◽  
Electric Field ◽  
Microfluidic Chip ◽  
Three Dimensional ◽  
Uniform Electric Field ◽  
High Quality ◽  
Manufacturing Method ◽  
Injection Process ◽  
Metal Microelectrode ◽  
Good Material

Electrokinetics is a good fluid control tool in microfluidics and usually microelectrodes play important roles in such approach such as generating a desired electric field. Though the fabrication of two-dimensional (2D) microelectrodes has been relatively mature, they cannot generate uniform electric field in space. Three-dimensional (3D) microelectrodes developed more recently may solve the problem, however the fabrication process is usually complicated and requires micro-alignment platform. Non-toxic liquid metal is a good material for making electrodes that has been introduced into microfluidics. It can be injected directly into a microchannel to form an electrode, but its special physical properties make the injection process complex and difficult to control. In this study, we investigated an optimized manufacturing method of liquid metal microelectrode in a microchip by numerical analysis and experimental study. High quality microelectrodes on morphology and stability were successfully fabricated. A fluorescent enrichment experiment was performed using the developed microelectrode in a microfluidic chip. The result shows that the optimized fabrication method of microelectrode in this study provides a promising way for high quality and good performance liquid metal microelectrode formation, and paves the way for its versatile applications.

scholarly journals Electrorheology of a dilute emulsion of surfactant-covered drops

2019 ◽  
Vol 881 ◽  
pp. 524-550 ◽  
Author(s):  
Antarip Poddar ◽  
Shubhadeep Mandal ◽  
Aditya Bandopadhyay ◽  
Suman Chakraborty
Keyword(s):  
Electric Field ◽  
Applied Electric Field ◽  
Surface Deformation ◽  
Three Dimensional ◽  
Shear Thickening ◽  
Field Configuration ◽  
Uniform Electric Field ◽  
Surface Tension Gradient ◽  
Drop Surface ◽  
Flow Perturbation

We investigate the effects of surfactant coating on a deformable viscous drop under the combined action of shear flow and a uniform electric field. Employing a comprehensive three-dimensional approach, we analyse the non-Newtonian shearing response of the bulk emulsion in the dilute suspension regime. Our results reveal that the location of the peak surfactant accumulation on the drop surface may get shifted from the plane of shear to a plane orthogonal to it, depending on the tilt angle of the applied electric field and strength of the electrical stresses relative to their hydrodynamic counterparts. The surfactant non-uniformity creates significant alterations in the flow perturbation around the drop, triggering modulations in the bulk shear viscosity. Overall, the shear-thinning or shear-thickening behaviour of the emulsion appears to be greatly influenced by the interplay of surface charge convection and Marangoni stresses. We show that the balance between electrical and hydrodynamic stresses renders a vanishing surface tension gradient on the drop surface for some specific shear rates, rendering negligible alterations in the bulk viscosity. This critical condition largely depends on the electrical permittivity and conductivity ratios of the two fluids and orientation of the applied electric field. Also, the physical mechanisms of charge convection and surface deformation play their roles in determining this critical shear rate. As a consequence, we obtain new discriminating factors, involving electrical property ratios and the electric field configuration, which govern the same. Consequently, the surfactant-induced enhancement or attenuation of the bulk emulsion viscosity depends on the electrical conductivity and permittivity ratios. The concerned description of the drop-level flow physics and its connection to the bulk rheology of a dilute emulsion may provide a fundamental understanding of a more complex emulsion system encountered in industrial practice.

Continuous Dielectrophoretic Separation of Multiple Particles in a Microfluidic Chip

2008 ◽  
Author(s):  
Christian Davidson ◽  
Junjie Zhu ◽  
Xiangchun Xuan
Keyword(s):  
Particle Size ◽  
Electric Field ◽  
Flow Separation ◽  
Microfluidic Chip ◽  
Continuous Flow ◽  
Uniform Electric Field ◽  
Dielectrophoretic Force ◽  
Size Dependent ◽  
Multiple Particles ◽  
Dc Dielectrophoresis

We successfully demonstrate that DC dielectrophoresis can be utilized to separate particles of three dissimilar sizes simultaneously in a microfluidic chip. This continuous-flow separation is attributed to the particle size dependent dielectrophoretic force that is generated by the non-uniform electric field around a single insulating hurdle on the channel sidewall.

Combination of Au Dielectrophoresis Chip and Optical Tweezers for Cell Culture

2015 ◽  
Vol 656-657 ◽  
pp. 549-553
Author(s):  
Kyohei Nishimoto ◽  
Kozo Taguchi
Keyword(s):  
Electric Field ◽  
Optical Tweezers ◽  
Cell Separation ◽  
Low Cost ◽  
Three Dimensional ◽  
Uniform Electric Field ◽  
Objective Lens ◽  
Separation System ◽  
Ac Electric Field ◽  
Viable Cells

Dielectrophoresis (DEP) force will arise when an inhomogeneous AC electric field with sinusoidal wave is applied to microelectrodes. By using DEP, we could distinguish between viable and non-viable cells by their movement through a non-uniform electric field. In this paper, we propose a yeast cell separation system, which utilizes an Au DEP chip and an optical tweezers. The Au DEP chip is planar quadrupole microelectrodes, which were fabricated by Au thin-film and a box cutter. This fabrication method is low cost and simpler than previous existing methods. The tip of the optical tweezers was fabricated by dynamic chemical etching in a mixture of hydrogen fluoride and toluene. The optical tweezers has the feature of high manipulation performance. That does not require objective lens for focusing light because the tip of optical tweezers has conical shape. By using both the Au DEP chip and optical tweezers, we could obtain three-dimensional manipulation of specific cells after viability separation.

scholarly journals Model Equations for Three-Dimensional Nonlinear Water Waves under Tangential Electric Field

2017 ◽  
Vol 2017 ◽  
pp. 1-8
Author(s):  
Bo Tao
Keyword(s):  
Electric Field ◽  
Water Waves ◽  
Three Dimensional ◽  
Liquid Sheet ◽  
Capillary Waves ◽  
Uniform Electric Field ◽  
Nonlinear Water Waves ◽  
Petviashvili Equation ◽  
Model Equations ◽  
Layer Problem

We are concerned with gravity-capillary waves propagating on the surface of a three-dimensional electrified liquid sheet under a uniform electric field parallel to the undisturbed free surface. For simplicity, we make an assumption that the permittivity of the fluid is much larger than that of the upper-layer gas; hence, this two-layer problem is reduced to be a one-layer problem. In this paper, we propose model equations in the shallow-water regime based on the analysis of the Dirichlet-Neumann operator. The modified Benney-Luke equation and Kadomtsev-Petviashvili equation will be derived, and the truly three-dimensional fully localized traveling waves, which are known as “lumps” in the literature, are numerically computed in the Benney-Luke equation.

scholarly journals A Study of Dielectrophoresis-Based Liquid Metal Droplet Control Microfluidic Device

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 340
Author(s):  
Lu Tian ◽  
Zi Ye ◽  
Lin Gui
Keyword(s):  
Liquid Metal ◽  
Electric Field ◽  
Microfluidic Device ◽  
Bubble Formation ◽  
Metal Droplet ◽  
Uniform Electric Field ◽  
Chip Design ◽  
Pdms Film ◽  
Liquid Metal Droplet ◽  
Droplet Control

This study presents a dielectrophoresis-based liquid metal (LM) droplet control microfluidic device. Six square liquid metal electrodes are fabricated beneath an LM droplet manipulation pool. By applying different voltages on the different electrodes, a non-uniform electric field is formed around the LM droplet, and charges are induced on the surface of the droplet accordingly, so that the droplet could be driven inside the electric field. With a voltage of ±1000 V applied on the electrodes, the LM droplets are driven with a velocity of 0.5 mm/s for the 2.0 mm diameter ones and 1.0 mm/s for the 1.0 mm diameter ones. The whole chip is made of PDMS, and microchannels are fabricated by laser ablation. In this device, the electrodes are not in direct contact with the working droplets; a thin PDMS film stays between the electrodes and the driven droplets, preventing Joule heat or bubble formation during the experiments. To enhance the flexibility of the chip design, a gallium-based alloy with melting point of 10.6 °C is used as electrode material in this device. This dielectrophoresis (DEP) device was able to successfully drive liquid metal droplets and is expected to be a flexible approach for liquid metal droplet control.

Computational Studies of Droplet Dynamics in a Steady Electric Field

2012 ◽  
Author(s):  
Ye Yao ◽  
Kevin M. Beussman ◽  
Yechun Wang
Keyword(s):  
Electric Field ◽  
Digital Microfluidics ◽  
Three Dimensional ◽  
Boundary Integral ◽  
Uniform Electric Field ◽  
Immiscible Fluid ◽  
Droplet Deformation ◽  
Droplet Dynamics ◽  
And Migration ◽  
Neutrally Buoyant

A three-dimensional spectral boundary integral algorithm has been developed to investigate the dynamics of a neutrally buoyant and initially uncharged droplet in another immiscible fluid subjected to a steady electric field. Good agreement has been found by comparing with analytical solutions and experimental results for droplets in a uniform electric field. Benefit from the fully three-dimensional algorithm that we have developed, the droplet deformation and migration induced by the nonuniform electric field created by a point charge has been investigated. We computationally predict the deformation and migration of the droplet under the influence of physical properties of the system: resistivities, permittivities and viscosities, as well as the electric capillary number. The numerical scheme developed by this study and computational results provide foundation for the computational investigation of droplet motion in digital microfluidics.

Three-dimensional analysis of the steady-state shape and small-amplitude oscillation of a bubble in uniform and non-uniform electric fields

1999 ◽  
Vol 384 ◽  
pp. 59-91 ◽  
Author(s):  
S. M. LEE ◽  
I. S. KANG
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Indirect Effect ◽  
Oscillation Frequency ◽  
Small Amplitude ◽  
Free Oscillation ◽  
Three Dimensional ◽  
Spherical Shape ◽  
Uniform Electric Field ◽  
Small Amplitude Oscillation

A three-dimensional analysis is performed to investigate the effects of an electric field on the steady deformation and small-amplitude oscillation of a bubble in dielectric liquid. To deal with a general class of electric fields, an electric field near the bubble is approximately represented by the sum of a uniform field and a linear field. Analytical results have been obtained for steady deformation and modification of oscillation frequency by using the domain perturbation method with the angular momentum operator approach.It has been found that, to the first order, the steady shape of a bubble in an arbitrary electric field can be represented by a linear combination of a finite number of spherical harmonics Yml, where 0[les ]l[les ]4 and [mid ]m[mid ][les ]l. For the oscillation about the deformed steady shape, the overall frequency modification from the value of free oscillation about a spherical shape is obtained by considering two contributions separately: (i) that due to the deformed steady shape (indirect effect), and (ii) that due to the direct effect of an electric field. Both the direct and indirect effects of an electric field split the (2l+1)-fold degenerate frequency of Yml modes, in the case of free oscillation about a spherical shape, into different frequencies that depend on m. However, when the average is taken over the (2l+1) values of m, the frequency splitting due to the indirect effect via the deformed steady shape preserves the average value, while the splitting due to the direct effect of an electric field does not.The oscillation characteristics of a bubble in a uniform electric field under the negligible compressibility assumption are compared with those of a conducting drop in a uniform electric field. For axisymmetric oscillation modes, deforming the steady shape into a prolate spheroid has the same effect of decreasing the oscillation frequency in both the drop and the bubble. However, the electric field has different effects on the oscillation about a spherical shape. The oscillation frequency increases with the increase of electric field in the case of a bubble, while it decreases in the case of a drop. This fundamental difference comes from the fact that the electric field outside the bubble exerts a suppressive surface force while the electric field outside the conducting drop exerts a pulling force on the surface.

The role of three-dimensional shapes in the break-up of charged drops

1987 ◽  
Vol 410 (1838) ◽  
pp. 209-227 ◽  
Keyword(s):  
Electric Field ◽  
Three Dimensional ◽  
Uniform Electric Field ◽  
Dynamical Equations ◽  
Oblate Spheroids ◽  
Initial Stage ◽  
Break Up ◽  
Axisymmetric Disturbances ◽  
Rayleigh Limit

A nonlinear analysis of the non-axisymmetric shapes and oscillations of charged, conducting drops is carried out near the Rayleigh limit that gives the critical amount of charge for which the spherical equilibrium form loses stability. The Rayleigh limit is shown to correspond to a fivefold singular point with only axisymmetric spheroidal shapes bifurcating from the family of spheres. The oblate spheroids that exist for greater amounts of charge are unstable to non-axisymmetric disturbances, which control the evolution of drop break-up. The bifurcating prolate spheroids that exist for values of charge less than the Rayleigh limit are only unstable to axisymmetric perturbations that elongate the drop along its symmetry axis; hence, the initial stage of the droplet break-up is through a sequence of lengthening prolate shapes. An external uniform electric field or a rigid-body rotation of the drop breaks the symmetry of the spherical base shape and is an imperfection to the Rayleigh limit. Addition of an electric field leads to slightly prolate shapes that end at a limiting value of charge. Rigid rotation leads to slightly oblate forms that lose stability to triaxial shapes. For values of charge just less than the Rayleigh limit, the amplitude equations that are derived from a multiple timescale analysis are equivalent to the dynamical equations of the Hénon‒Heiles Hamiltonian. The remarkable and complicated properties of the bounded solutions to this set of equations are well known and reviewed briefly here.

Numerical Simulation of Formation and Distortion of Taylor Cones

2012 ◽  
Vol 3 (4) ◽  
Author(s):  
Kamal Sarkar ◽  
Palmira Hoos ◽  
Alberto Urias
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Moving Boundary ◽  
Three Dimensional ◽  
Simulation Method ◽  
Electrospinning Process ◽  
Uniform Electric Field ◽  
Dielectric Fluids ◽  
Polymeric Solutions ◽  
Theoretical Analyses

Taylor cones are integral parts in many important applications like electrospinning and electrospray mass spectroscopy. A better understanding of this complex phenomenon of Taylor cone is critical for better control of these processes. As an example, if it is possible to identify and prioritize the roles of fluid characteristics and externally applied electric field, it might be easier to target and control the diameters of nanofibers in an electrospinning process. Under the influence of high electric fields, Taylor cones are formed by a number of liquids including many polymeric solutions. Because of small spatial (microns and below) and temporal (microseconds and below) scales, it is difficult to experimentally study the transient formation of Taylor cones. A number of theoretical analyses have been done under simplifying assumptions like uniform electric field, constant electrohydrodynamic behaviors of the fluid, stationary droplet, etc. Initial Taylor formulation included the introduction of “leaky dielectric” that accumulated charges only on the surface for certain dielectric fluids. Yarin et al. later developed analysis for stationary droplets assuming them to be “perfectly conducting”. To simulate the electrospinning process, the formulation needs the ability to analyze moving boundary conditions, complex fluid properties, three dimensional geometry, and nonlinear coupling between air and liquid, among others. To overcome some of the assumptions of theoretical analyses and as another complementary tool, a computer simulation method was proposed using a commercially available software. In this investigation, much studied aqueous polyethylene oxide (PEO) solution was used to study formation and distortion of Taylor cones. An initial velocity was given to the fluid from the tip of a nozzle and an appropriate electric field was applied to form the Taylor cones. Literature values were used for flow, fluid, and electrical characteristics of the solution. By appropriately manipulating fluid velocities and electric fields, simulations were successful to both replicate the classical cone and distort it to various degrees. These formation and distortion of Taylor cones were similar to reported experimental results. While the numerical and experimental Taylor cones were significantly different in sizes, nondimensional shapes, and sizes of both the results were strikingly similar. Velocities of the fluid in the jet jumped almost 50 times to meters/second as was experimentally observed. Unlike theoretical solutions, the simulation results showed the interaction of the electric fields between the air and advancing fluid tip.

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