Scalable Focusing in Single-Cell Analysis Enabled by Amplitude Modulated Positive Dielectrophoresis

In conventional stream-based single-cell analysis, hydrodynamical focusing methods typically require constraining sample flow or complex channel structures, which can adversely impact analysis throughput and is unsuitable for low-concentration samples. In this study, we introduced a microfluidic device that employed the positive dielectrophoresis (DEP) force to focus cells, eliminating the need for flow manipulation or clog-sensitive structures that compromise the system throughput. To mitigate the potential issues of cell attachment induced by strong attracting force, we employed a squarewave to modulate the amplitude of the DEP signal, enabling efficient cell focusing with amplitude-modulated positive DEP force (AM-pDEP). The theoretical model is constructed to facilitate parameter optimization and demonstrate its suitability for low-concentration samples. Additionally, focusing performance is verified with a side-arranged Coulter counter to form an impedance-based on-chip flow cytometer with scalable analysis throughput.