Design rules for size-based cell sorting and sheathless cell focusing by hydrophoresis

We describe the effects of geometric and operational parameters on the performances of hydrophoresis devices for optimal size-based cell sorting and sheathless cell focusing. Hydrophoresis has been recently demonstrated to precisely control cells in a continuous flow with advantages of sheathless, high resolution, and easy parallelization. To date, key parameters for optimal design and operation of hydrophoresis systems have yet to be fully studied. In this study we have investigated geometric parameters such as channel width and oblique angle of slanted grooves, and an operational parameter, flow rate that can potentially influence the device performances. The channel width is found to be the most significant geometric factor that affects the device performances, while the oblique angle of slanted grooves has no significant influence. Size-based separation of cells having size diversity (≈11% in a coefficient of variation (CV)), as well as sheathless cell focusing, was performed with optimal designs, demonstrating the potential use of hydrophoresis as a microfluidic component to precisely control cells for integrated cell sorting and analysis systems.