Tunnel dielectrophoresis for ultra-high precision size-based cell separation

In molecular and cellular biological research, cell isolation and sorting are required for accurate investigation of cell populations of specific physical or biological characteristics. By employing unique cell properties to distinguish between heterogeneous cell populations, rapid and accurate sorting with high efficiency is possible. Dielectrophoresis-based cell manipulation has significant promise for separation of cells based on their physical properties and is used in diverse areas ranging from cellular diagnostics to therapeutic applications. In this study, we present a microfluidic device that can achieve label-free and size-based cell separation with high size differential resolution from a mono-cellular population or complex sample matrices. It was realized by using the tunnel dielectrophoresis (TDEP) technique to manipulate the spatial position of individual cells three dimensionally with high resolution. Cells were processed in high speed flows in high ionic strength buffers. A mixture of different sizes of polystyrene micro-particles with a size difference as small as 1 μm can be separated with high purity (>90%). For the first time, high-pass, low-pass, and band-pass filtering within a mono-cellular mammalian cell population were demonstrated with a tunable bandwidth as small as 3 μm. In addition, leukocyte subtype separation was demonstrated by sorting monocytes out of peripheral blood mononuclear cells (PBMCs) from whole blood with high purity (>85%). Its ability to deliver real-time adjustable cut-off threshold size-based cell sorting and its capability to provide an arbitrary cell size pick-up band could potentially enable many research and clinical applications.