(230j) Collective Dielectrophoretic Trapping Assisted By AC Electrokinetic Flow

Dielectrophoresis (DEP) is the migration of a polarized object under the action of a non-uniform electric field. As DEP is capable of trapping and distinguishing samples according to their properties, it has become a useful tool for achieving on-chip screening and diagnosis using microfluidics. However, because DEP trapping often occurs in close proximity of electrodes, it generally lacks a long-range trapping capability. In addition, because the DEP mobility is proportional to square of the sample size, it is also difficult to use DEP to trap nano-sized objects.

In this work we demonstrate that the above shortcomings of DEP can be overcome by using a proper electrode design. Our electrode design is a quadrupole one. But unlike a standard quadrupole design, the four electrodes here are made to be converging shaped with width being gradually decreased toward the central region. Using this design to trap microparticles, we find that not only the particles can be rapidly trapped by DEP around the central region but also the trapped particle assembly can keep growing in size due to the continuous particle supply from the AC electrokinetic flow (ACEK) set up by the converging electrodes. A successful trapping of nano-sized particles and biomolecules can also be realized, offering a promising means for rapid sensing and detection in chip scales.