Electrokinetic Focusing of Colloidal Particles by Joule Heating Induced Temperature Gradient in a Convergent-Divergent Microfluidic Structure

2014 ◽  
Author(s):  
Zhengwei Ge ◽  
Chun Yang
Keyword(s):  
Temperature Gradient ◽  
Joule Heating ◽  
Colloidal Particles ◽  
Microfluidic Structure

Joule Heating Induced Temperature Gradient Focusing for Microfluidic Concentration of Samples

2010 ◽  
Author(s):  
Zhengwei Ge ◽  
Chun Yang
Keyword(s):  
Temperature Gradient ◽  
Electric Field ◽  
Joule Heating ◽  
Field Experiments ◽  
Dc Voltage ◽  
Sample Concentration ◽  
Great Achievement ◽  
Temperature Gradient Focusing ◽  
Concentration Enhancement ◽  
High Frequency Ac

Microfluidic concentration of sample species is achieved using the temperature gradient focusing (TGF) in a microchannel with a step change in the cross-section under a pure direct current (DC) field or a combined alternating current (AC) and DC electric field. Experiments were carried out to study the effects of applied voltage, buffer concentration and channel size on sample concentration in the TGF processes. These effects were analyzed and summarized using a dimensionless Joule number that is introduced in this study. In addition, Joule number effect in the Poly-dimethylsiloxane (PDMS)/PDMS microdevice was compared with the PDMS/Glass microdevice. A more than 450-fold concentration enhancement was obtained within 75 seconds in the PDMS/PDMS microdevice. Results also showed that the high frequency AC electric field which contributes to produce the temperature gradient and reduces the required DC voltage for the sample concentration. The lower DC voltage has generated slower electroosmotic flow (EOF), which reduces the backpressure effect associated with the finite reservoir size. Finally, a more than 2500-fold concentration enhancement was obtained within 14 minutes in the PDMS/PDMS microdevice, which was a great achievement in this TGF technique using inherent Joule heating effects.

Microfluidic concentration enhancement of bio-analyte by temperature gradient focusing via Joule heating by DC plus AC field: A numerical approach

2021 ◽  
pp. 1-17
Author(s):  
Amitava Dutta ◽  
Apurba Kumar Santra ◽  
Ranjan Ganguly
Keyword(s):  
Temperature Gradient ◽  
Joule Heating ◽  
Phosphate Buffer ◽  
Phosphate Buffer Solution ◽  
Numerical Approach ◽  
High Concentration ◽  
Buffer Solution ◽  
Temperature Gradient Focusing ◽  
Ac Field ◽  
Target Analyte

Abstract We present a detailed numerical analysis of electrophoresis induced concentration of a bio-analyte facilitated by temperature gradient focusing in a phosphate buffer solution via Joule heating inside a converging-diverging microchannel. The purpose is to study the effects of frequency of AC field and channel width variation on the concentration of target analyte. We tune the buffer viscosity, conductivity and electrophoretic mobility of the analyte such that the electrophoretic velocity of the analyte locally balances the electroosmotic flow of the buffer, resulting in a local build-up of the analyte concentration in a target region. An AC field is superimposed on the applied DC field within the microchannel in such a way that the back pressure effect is minimized, resulting in minimum dispersion and high concentration of the target analyte. Axial transport of fluorescein-Na in the phosphate buffer solution is controlled by inducing temperature gradient through Joule heating. The technique leverages the fact that the buffer's ionic strength and viscosity depends on temperature, which in turn guides the analyte transport. A numerical model is proposed and a finite element-based solution of the coupled electric field, mass, momentum, energy and species equations are carried out. Simulation predict peak of 670-fold concentration of fluorescein-Na is achieved. The peak concentration is found to increase sharply as the channel throat width, while the axial spread of concentrated analyte increases at lower frequency of AC field. The results of the work may improve the design of micro concentrator.

scholarly journals Numerical Simulation of 2D Electrothermal Flow Using Boundary Element Method

2013 ◽  
Author(s):  
Qinlong Ren ◽  
Cho Lik Chan ◽  
Alberto L. Arvayo
Keyword(s):  
Integral Equation ◽  
Temperature Field ◽  
Heat Conduction ◽  
Boundary Element Method ◽  
Temperature Gradient ◽  
Stokes Equation ◽  
Joule Heating ◽  
Electrical Potential ◽  
Space Velocity ◽  
Electrothermal Flow

Microfluidics and its applications to Lab-on-a-Chip have attracted a lot of attention. Because of the small length scale, the flow is characterized by a low Re number. The governing equations become linear. Boundary element method (BEM) is a very good option for simulating the fluid flow with high accuracy. In this paper, we present a 2D numerical modeling of the electrothermal flow using BEM. In electrothermal flow the volumetric force is caused by electric field and temperature gradient. The physics is mathematically modeled by (i) Laplace equation for the electrical potential, (ii) Poisson equation for the heat conduction caused by Joule heating, (iii) continuity and Stokes equation for the low Reynolds number flow. We begin by solving the electrical potential and electric field. The heat conduction is caused by the Joule heating as the heat generation term. Superposition principle is used to solve for the temperature field. The Coulomb and dielectric forces are generated by the electrical field and temperature gradient of the system. We analyze the Stokes flow problem by superposition of fundamental solution for free-space velocity caused by body force and BEM for the corresponding homogeneous Stokes equation. It is well known that a singularity integral arises when the source point approaches the field point. To overcome this problem, we solve the free-space velocity analytically. For the BEM part, we also calculate all the integral terms analytically. With this effort, our solution is more accurate. In addition, we improve the robustness of the matrix system by combining the velocity integral equation with the traction integral equation. Our purpose is to design a pump for the microfluidics system. Since the system is a long channel, the flow is fully developed in the area far away from the electrodes. With this assumption, the velocity profile is parabolic at the inlet and outlet of the channel. So we can get appropriate boundary conditions for the BEM part of Stokes equation. Consequently, we can simulate the electrothermal flow in an open channel. In this paper, we will present the formulation and implementation of BEM to model electrothermal flow. Results of electrical potential, temperature field, Joule heating, electrothermal force, and velocity field will be presented.

Joule Heating Induced Temperature Gradient Focusing in a Microfluidic Channel With a Sudden Change in Cross Section

2008 ◽  
Author(s):  
Gong Yue Tang ◽  
Chun Yang
Keyword(s):  
Temperature Gradient ◽  
Joule Heating ◽  
Stokes Equations ◽  
Sudden Change ◽  
Microfluidic Channel ◽  
Navier Stokes ◽  
Governing Equations ◽  
Temperature Gradient Focusing ◽  
Poisson Boltzmann Equation ◽  
Energy Equations

Temperature gradient focusing is a recently developed technique for spatially focusing and separating ionic analytes in microchannels. The temperature gradient required for temperature gradient focusing can be generated either by an imposed temperature gradient or by Joule heating resulted from an applied electric field that also drives buffer flow. In this study, a numerical model describing the Joule heating induced temperature development and temperature gradient focusing is developed. The model consists of a set of governing equations including the Poisson-Boltzmann equation, the Laplace equation, the Navier-Stokes equations, the energy equations and the mass transport equation. As the thermophysical and electrical properties including the liquid dielectric constant, viscosity and electric conductivity are temperature-dependent, these governing equations are coupled, and therefore the coupled governing equations are solved numerically by using a CFD based numerical method. The numerical simulations agree well with the experimental results, suggesting that the valid mathematical model presented in this study.

Growth of 4H-SiC in Current-Controlled Liquid Phase Epitaxy

2013 ◽  
Vol 740-742 ◽  
pp. 3-6 ◽  
Author(s):  
Takeshi Mitani ◽  
Masayuki Okamura ◽  
Tetsuo Takahashi ◽  
Naoyoshi Komatsu ◽  
Tomohisa Kato ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Temperature Gradient ◽  
Electric Current ◽  
Joule Heating ◽  
Liquid Phase Epitaxy ◽  
Negative Polarity ◽  
Growth Speed ◽  
Positive Polarity ◽  
Current Leads ◽  
Dc Current

4H-SiC crystallization from Si-C solution in electric current-controlled liquid phase epitaxy was investigated. The dependence of growth speed on a DC current shows that dissolution/growth is controlled by the electric current without altering temperature gradient in the furnace. Application of an electric current leads to reduction of growth speed with negative polarity and enhancement of growth speed with positive polarity. The variation of the growth speed with a DC current density has been explained by the combination of the effects of electromigration of C solute and Joule heating.

Effect of aluminum trace dimension on electro-migration failure in flip-chip package

2017 ◽  
Vol 31 (07) ◽  
pp. 1741002
Author(s):  
Peisheng Liu ◽  
Guangming Fan ◽  
Yahong Liu ◽  
Longlong Yang ◽  
Xiaoyong Miao
Keyword(s):  
Temperature Gradient ◽  
Joule Heating ◽  
Current Density ◽  
Flip Chip ◽  
3D Model ◽  
Hot Spot ◽  
Electrical Coupling ◽  
Migration Mechanism ◽  
Spot Temperature

A 3D model of flip-chip package is established and thermal–electrical coupling is analyzed. The effect of the width of Aluminum (Al) trace on electro-migration mechanism is also studied. Reducing rates of the hot-spot temperature, the max Joule heating, the max temperature gradient and the max current density are defined to research the effects of the Al trace thickness and the UBM thickness on electro-migration.

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