Three-dimensional hydrodynamic flow focusing of dye,particles and cells in a microfluidic device by employing two bends of opposite curvature

This work relates to three-dimensional (3D) hydrodynamic flow focusing, wherein sample is encapsulated by sheath fluid in all the directions, making it a preferred method for particle focusing. Given the complex phenomenon involved in achieving 3D hydrodynamic focusing, we have been able to demonstrate a relatively simple microdevice for achieving this objective. In this work, a novel approach for 3D focusing utilizing two bends of opposite curvature in microchannel is proposed and demonstrated through experiments and numerical simulations. The proposed microdevice is fabricated on a single layer of polydimethylsiloxane and a single sheath inlet is used, thereby simplifying the 3D focusing mechanism and reducing the requirements of cost enhancing accessories. The mechanism underlying particle focusing is examined in detail. This microdevice provides several distinct advantages over other designs mentioned in the literature.