A dielectrophoretic preconcentrator with circular microelectrodes for biological cells in stepping electric fields

The ability to enrich rare cells, e.g. circulating tumor cells (CTC), circulating fetal cells, and stem cells, has been an important issue in medical diagnostics and characterization. The main purpose of this investigation was to develop a handheld microdevice capable of the effective preconcentration of rare cells. Circular microelectrodes were designed to generate the stepping electric field by switching the electric field to an adjacent electrode pair by relays. The cancerous cells with positive dielectrophoretic response were not only conveyed but also concentrated toward the center of the circular microelectrodes because the high-electric-field region between the adjacent electrodes was gradually decreased in the direction of the stepping electric field. Numerical simulations of the electric fields were performed to demonstrate the concept of the proposed design. Moreover, enrichment of cervical cancer cells was successfully achieved and took about 160 seconds in the experiment with an approximate efficiency of 75%, when the peak-to-peak voltage of 16 volts, a frequency of 600 kHz and the time interval of relay switching with 20 seconds were applied.