A compact and low cost microfluidic cell impedance detection system

A microfluidic cell impedance measurement device is presented in this article. The design is simple to fabricate, compact, highly sensitive, and can be easily incorporated into a microfluidic flow cytometer suitable for point-of-care applications. The simple fabrication process and enhanced sensitivity are attributed partly to a novel design of using fluidic channels as "liquid electrodes" to assure a uniform electric field distribution over the cell detection zone. The system's low cost and compact size is due to its sheathless flow design and single circuit board for cell impedance detection, eliminating expensive and bulky equipments such as lock-in amplifiers and additional sheath flow pumps. The device clearly detects and distinguishes polystyrene beads of 7.66 mu m, 10.5 mu m and 14.7 mu m diameters in a mixture with coefficients of variation of 13.87%, 7.98% and 3.74%, respectively. By extracting the features of cell impedance signals using signal processing, we have introduced a new parameter, impedance ratio, to enhance the cell classification capabilities of the device, as demonstrated in the experiment of lymphocytes and granulocytes detection from whole blood.