Three-dimensional hydrodynamic flow and particle focusing using four vortices Dean flow

We present a three-dimensional (3D) hydrodynamic focusing device built on a single-layer platform using single sheath flow. Despite the simple structure and operation, the device not only achieves narrow focusing of a sample fluid or particles but also switches the cross-sectional size and lateral position of the sample stream. The focusing mechanism utilizes four Dean vortices generated in a high-speed flow through a curved channel. Theoretical calculations, numerical simulations, and an experimental study demonstrated that the device could focus microparticles that resemble human platelets in terms of particle size and density in a single-stream manner. Further simulation study suggested that the device could focus most cell sizes used in flow cytometry with a throughput of 200,000 cells s(-1). In addition, the device can function as a 3D liquid-core/liquid-cladding (L2) optical waveguide by introducing a core liquid with a refractive index higher than that of the cladding.