Abstract
Alternating current electrothermal flow has been extensively used for mixing of fluids in microfluidic systems. This work presents a novel approach to mixing two laminar flow streams in microchannels. The micromixer consists of a pair of asymmetric planar alternating current electrodes disposed along a fluidic channel and a thin film resistive heater below the electrode. Multiphysics (fluid flow, temperature, electrical, and concentration fields) in the micromixer is studied by numerical simulation method. The results indicate that external heating by the thin film resister leads to flow body forces that are proportional to the temperature gradient and chaotic stretching and folding of fluid material lines. Enhancement of mixing is demonstrated by numerical simulation results. Effects of size and location of the thin film resistive heater on mixing efficiency are also investigated.
Highlights
Chip-scale micromixing is essential in many microfluidic devices, which requires rapid mixing of reactants in biochemical processes.[1]
Mixing of fluid streams in microfluidic devices is limited by low value of the mass diffusion coefficient, as well as the low Reynolds number laminar flow and the absence of turbulence to assist mixing in microchannels
A heat flux of 2:5 3 105 W=m2 is prescribed on the surface of the thin film resistive heater, which is feasible because a heat flux has been used as the boundary condition of the heater in Yuan and Wu.[10]
Summary
Chip-scale micromixing is essential in many microfluidic devices, which requires rapid mixing of reactants in biochemical processes.[1]. A fixed value of heat flux is prescribed on the surface of the heater to model its heating effect.[16] Fluid temperature at the inlet is assumed to be a constant (room temperature), and an outflow boundary condition of zero normal temperature gradients is imposed at the outlet which is far enough from the AC electrodes.
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