Design and fabrication of coplanar waveguide probes for single-cell impedance measurement using radio frequency

When cell impedance measurements are conducted at low frequency, the current passes through the outside wall of the cell membrane. The capacitance effect of the double layer and the position of the cell change the impedance. Therefore the pathological change inside the cell cannot be investigated. To overcome the shortcomings of low-frequency measurements, this Letter proposes a method that uses a dielectrophoretic (DEP) trapping technique to position single cells and a coplanar waveguide electrode to measure the impedance of a single HeLa cell (human cervical epithelioid carcinoma) in the frequency range of 1 MHz-1 GHz. Two materials (a double-sided printed circuit board and glass) are used to fabricate the measurement microelectrodes. Trapping microelectrodes are deposited on the glass substrate near the measurement microelectrodes to trap single cells using the DEP force. The electrical characterisation of a single cell is demonstrated using a two-port vector network analyser. The electrical equivalent model used in this work is validated through measurements of cell impedance in phosphate buffer solution and through electrical simulations of a single HeLa cell.