Single-Cell Capture and Electrically Induced In-Plane Rotation with Frequency-Dependent Spatial Segregation Using Serrated Floating Electrodes

Precise single-cell manipulation is essential for investigating cellular heterogeneity and enabling downstream bioanalytical applications. However, conventional dielectrophoretic platforms often suffer from excessive field localization, multi-cellular aggregation, and complicated electrode integration, limiting their controllability and scalability. Here, we present a microfluidic platform based on serrated floating electrodes for multimodal single-cell manipulation through frequency-dependent electrokinetic regulation. Periodically arranged driving and floating electrodes generate spatially confined high-gradient electric fields that enable deterministic single-cell trapping under low-voltage excitation. Numerical simulations reveal that the floating-electrode architecture redistributes the local electric field and transforms broad trapping regions into discrete localized trapping sites, thereby suppressing multi-cellular aggregation while maintaining sufficient dielectrophoretic trapping force. Experimental results demonstrate stable single-cell capture over a broad frequency range from 20 kHz to 1 MHz, with significantly improved single-cell selectivity compared with conventional driving electrodes. The platform further enables frequency- and voltage-dependent electrically induced in-plane rotation of dielectrophoretically-confined yeast cells under single-channel sinusoidal AC excitation. In addition, particles and cells with distinct dielectric properties exhibit frequency-dependent spatial segregation behaviors: polystyrene particles undergo negative dielectrophoresis and accumulate in low-field regions, whereas yeast cells exhibit positive dielectrophoresis and concentrate at serrated electrode tips. The system also enables label-free viability discrimination between live and dead yeast cells based on differential dielectric responses in the MHz-frequency regime. Owing to its structural simplicity, low-voltage operation, optical transparency, and multimodal controllability, this serrated floating-electrode platform provides a versatile strategy for integrated single-cell analysis and electrokinetic bioanalytical applications.