The aim of hydrodynamic flow focusing is to focus the sample fluid using a sheath fluid. Hydrodynamic focusing is a simple yet effective technique for flow focusing and control. It has been successfully utilized in various microfluidic applications. This includes on-chip microfluidic flow cytometry (where hydrodynamic flow focusing is used to focus the cells suspended in the sample fluid in a single file, which can then be utilized for counting/sorting of cells), flow switches (for injection of sample in the desired outlet port by controlling the sheath flow rate), micro-mixers, etc.
We have been able to demonstrate a relatively simple microdevice for achieving this objective (see figure). Towards this, 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 proposed microdevice provides several distinct advantages over other designs mentioned in the literature.
Tripathi, S., Kumar, A., Kumar, Y.V.B., Agrawal, A.,
"Three-dimensional hydrodynamic flow focusing of dye, particles and cells in a microfluidic device by employing bends of opposite curvature," Microfluidics and Nanofluidics, Vol. 20, pp. 1-14, 2016.
Tripathi, S., Chakravarty, P., Agrawal, A.,
"On non-monotonic variation of hydrodynamically focused width in rectangular microchannel," Current Science, Vol. 107(8), pp. 1260-1274, 2014.
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