Demonstration of New Microelectrode Design to Enhance Sensitivity of Dielectrophoretic Impedance Measurement

Dielectrophoretic impedance measurement (DEPIM) is a method using a microelectrode for measuring a target suspended in a solution by combining dielectrophoretic (DEP) trapping of the target and simultaneous measurement of impedance varied with the trapping. DEPIM can be utilized to detect bacteria and viruses without any chemical additive since DEPIM efficiency depends on the DEP trapping dominated by the microelectrode shape. This letter aims to demonstrate a new microelectrode design to increase bacteria detection efficiency instead of the conventional interdigitated microelectrode. The microelectrode having a serpentine gap as a sinusoidal waveform profile was proposed. The new microelectrode was compared with the interdigitated one in numerical simulation and experiments. The numerical simulation demonstrates that the serpentine microelectrode traps all the targets in a laminar flow in a microchannel. In contrast, the interdigitated one placed parallel to the microchannel does not because the target flowing away from the edges of the microelectrode cannot be trapped. The experiments using three kinds of bacteria were carried out. It was demonstrated that the serpentine microelectrode represented a sensitivity 10⁴ times higher than the interdigitated one when a small amount of the sample solution was tested for a short time (1 min).