On-chip microscale thermophoresis using MEMS-fabricated fluidic channel

A temperature difference in microscale spatial distance in fluid can produce a strong temperature gradient, which induces thermophoresis of dispersed micro/nano particles. Such a particle transport, microscale thermophoresis, is expected to develop a new particle manipulation technique used in micro- and nanofluidic devices, since it has different physical characteristics from common methods such as electrophoresis. In the present study, we fabricate a microfluidic device with a micro heater using micro-electro-mechanical systems (MEMS) technologies and demonstrate that the microscale thermophoresis effectively controls the flow of microparticles. In particular, we find that polystyrene and silica microparticles have opposite responses to the temperature gradient, realizing the selective particle transport in the microfluidic system.