Novel thermophoretic particle separators: Numerical analysis and simulation

In this paper, it is shown that thermophoresis is a viable method for precise particle separation (sieving) and manipulation in microchannels. To do so, thermophoresis force acting on particles suspended in air and water flowing in a microchannel heated from below are simulated and relative magnitude and difference of thermophoresis force acting on a particle in a gas and liquid is discussed, discerned and elucidated. To show the potential of thermophoresis to serve as a sieve, transport equations for suspension of polystyrene in water and gold particles in air are solved numerically, both in the absence and presence of gravity. In simulations, particles are considered as a discrete phase and their trajectories are tracked using a Lagrangian approach. It is shown that thermophoresis can be used to separate macromolecules and particles from a water stream in a microchannel with one inlet and two outlets. Also, it is demonstrated that thermophoresis can be used as a means to separate multiple particle streams with different characteristics such as size and density from a gas flowing in a microchannel. Two microchannel geometries were numerically analyzed and it is shown that in both cases particles with different sizes are forced to exit through a different outlets. This effect can be used to separate, concentrate, manipulate, trap, target and transfer macromolecules such as bio-molecules and DNA in a microchannel. The correct application of thermophoresis theory in a gas and liquid is elucidated throughout the simulations.