Particles focusing using negative insulator-based dielectrophoresis

For medical applications of cell sorting, counting or flow cytometry, focusing of biological cells in microdevices is a prerequisite. Hydrodynamic focusing by sheath flow has been a widely used method for particle focusing, however, additional buffer inlets and precise flow control were needed. An insulator-based dielectrophoretic microdevice of four insulating structures forming X-pattern with effective focusing of biological cells was designed in this paper. The effects parameters such as electric filed applied and inlet velocity were also investigated herein. The inlet flow field and the electric field were applied vertically. The cells were introduced into the microchannel and pre-confined hydrodynamically by the funnel-shaped insulating structures close to the inlet. Thereupon the cells flowed into the constricting region where the square of the electric field distributed as saddle-shaped. The cells with negative dielectrophoretic response were therefore repelled toward the center of the constricting region. It indicated apparently that the increase of the electric field applied significantly enhanced the performance of focusing. According to the numerical results, decreasing the inlet velocity could increase the efficiency of focusing. The design proposed herein has no need of complicated flow controls for focusing of cells. The microdevice is easy to operate and integrate into further biomedical applications.