Continuous dielectrophoretic particle separation using a microfluidic device with 3D electrodes and vaulted obstacles.

This paper reports a microfluidic separation device combining 3D electrodes and vaulted obstacles to continuously separate particles experiencing strong positive dielectrophoresis (DEP) from particles experiencing weak positive DEP, or from particles experiencing negative DEP. The separation is achieved by first focusing the particle mixture into a narrow stream by a hydrodynamic focusing flow, and then deviating them into different outlets by AC DEP. The vaulted obstacles facilitate the separation by both increasing the non-uniformity of the electric field, and influencing the particles to move in regions strongly affected by DEP. The 3D electrodes give rise to a spatially non-uniform electric field and extend DEP effect to the channel height. Numerical simulations are performed to investigate the effects of the obstacles on electric field distribution and particle trajectories so as to optimize the obstacle height and compare with the experimental results. The performance of the device is assessed by separating 25 μm gold-coated particles from 10 μm particles in different flow rates by positive DEP and negative DEP, and also separating 25 μm gold-coated particles from yeast cells using only positive DEP. The experimental observation shows a reasonable agreement with numerical simulation results.