Depth effects of DEP chip with microcavities array on impedance measurement for live and dead cells

We demonstrated the capability of cell trapping with combination of dielectrophoresis (DEP) and 3D microstructures array and also designed a multi-layer electrodes for impedance measurement of particles in the prior work. In the present study, in order to discriminate live and dead cells based on impedance measurement, a DEP chip consisted of microcavities array and three-layer electrodes was designed to trap cells and further impedance measurement. By introducing microstructure to DEP chip, the capability of positioning and immobilization of single cell could be achieved, however, some problems also accompanied along as impedance measurement, such as noise signal and less difference between different samples. Therefore, the depth effects on DEP force and electrical properties measurement were analyzed by numerical simulation. According to the numerical results, the microcavity with 10 mum in depth was the optimal design for this multi-functional DEP chip. In addition, two kinds of suspension cell lines, NB4 and HL-60, were utilized to examine the identification of live and dead cells by in vitro experiments. In our impedance measurement, the operation voltage is 0.2 V and the scan frequency is from 1 KHz to 3 MHz. The difference of impedance magnitude between live and dead cells was larger in the low frequency range; therefore, this microchip not only provides an efficient way to immobilization cells in the microcavity for a long period of time without applying DEP force but also easily identifies the live and dead cells based on impedance measurement.