AC electrokinetic separation of particles by charge in a ratchet microchannel

The utilization of microfluidic techniques for particle manipulation is actively pursued across a wide range of disciplines in both fundamental and applied research. One of the important manipulation modes is particle sorting based on the difference in intrinsic properties. We present in this work a charge-based separation of particles with a similar size in a ratchet microchannel via AC insulator-based dielectrophoresis (AC iDEP). It is found that the faster-moving plain particles are focused into a stream along the center of the channel while the slower-moving fluorescent particles are concentrated at the base of the ratchets. We examine the effects of both the AC field amplitude and frequency on the particle separation. We also investigate the separation of the plain and fluorescent particles with different sizes. We have also developed a numerical model to understand and simulate the AC iDEP focusing and separation of particles.