Nonlinear Temperature Gradient Focusing of Deoxyribose Nucleic Acid in a Microfluidic Channel With Patterned Surface Charges: A Numerical Study

Abstract

We present a numerical analysis of electrophoretic transport of a biological sample, such as, deoxyribose nucleic acid (DNA) via nonlinear temperature gradient within a microfluidic channel having patterned surface charges. The transport of the electrolyte is induced by electroosmotic force by imposing an axial electric field, superposed with the wall electric field via electrodes embedded along the wall of the microchannel. We consider the periodic variation of wall zeta potential in electrokinetic motion of an electrolyte wherein the DNA sample exhibits electrophoretic migration. Temperature dependence of the thermophysical properties of the electrolyte and the electrophoretic mobility and diffusivity of the analyte sample is accounted for in the model to improve its accuracy. Nonlinear longitudinal temperature field along the microchannel is induced via Joule heating by suitably shaping the channel geometry, which enhances the concentration of DNA approximately 270 folds by applying just 500 V DC field with constant zeta potential at the walls. The study further reveals that the concentration of DNA reduces drastically when a periodic wall zeta potential is applied. Results of the study lend to the design of novel electrically actuated bio-microfluidic devices with tunable solute separation and dispersion capabilities.