A three-dimensional dielectrophoretic particle focusing channel for microcytometry applications

In this paper, we have designed and fabricated a microfluidic channel to focus biological cells using dielectrophoresis for cytometry applications. The device consists of an elliptic-like channel fabricated by isotropic etching of soda lime glass wafers and a subsequent wafer-bonding process. Microelectrodes are patterned on the circumference of the channel to generate ac fringing fields that result in negative dielectrophoretic forces directing cells from all directions to the center of the channel. An analysis using a thin shell model and experiments with microbeads and human leukemia HL60 cells indicate that biological cells can be focused using an ac voltage of an amplitude up to 15 V_p-p and a frequency below 100 kHz, respectively. This design eliminates the sheath flow and the fluid control system that makes conventional cytometers bulky, complicated, and difficult to operate, and offers the advantages of a portable module that could potentially be integrated with on-chip impedance or optical sensors into a micro total analysis system.