Simultaneous and Successive Three Dimensional Hydrodynamic Focusing in Flow Cytometer

Hydrodynamic focusing inside microfluidic devices has the main role in precisely directing the particles flow into a single stream carrying one particle at a time for cell sorting and medical diagnosis. In this paper two micro channel designs for focusing the sample flow in both the horizontal and vertical directions are presented. Using the proposed designs three dimensional (3D) focusing is achieved either simultaneously, where two pairs of cylindrical shaped horizontal and vertical side channels are located at same point, or successively by locating the vertical channels apart from the horizontal ones. A comparison between the two designs is presented regarding effect of vertical side channels location on focusing width, identity of focusing and ion concentration distribution inside the micro channel. Moreover the effect of different parameters on the focusing width and the concentration profile is investigated. Numerical simulation is performed using COMSOL multiphysics software.