Analysis of thermophoresis for separation of polystyrene microparticles in microfluidic devices

Abstract

We analysed the thermodiffusion phenomenon both numerically and experimentally for size-based separation of polystyrene microparticles. For model validation, we followed previously published numerical studies using ANSYS Fluent 2020 R2 software. For our experimental analysis, we defined a new microchannel geometry that would separate at least two groups of particles (5 and 20 µm). We analysed the trajectory of the microparticles in the central channel of the microdevice under the following conditions: without a temperature gradient, with application of a thermal gradient parallel to the gravitational field (cooling from the bottom or top part), and generation of a temperature gradient perpendicular to the direction of the gravity force. Numerical and experimental results for these geometry and boundary conditions demonstrated that, under terrestrial conditions, 5 µm and larger microsized polystyrene particles cannot be separated by thermophoresis in flow because of the gravity force.