2007 NSTI Nanotechnology Conference and Trade Show - Nanotech 2007 - 10th Annual

Numerical and Experimental Investigation of Three-Dimensional Hydrodynamic Focusing in Polydimethylsiloxane (PDMS) Microchannels

C-C Chang and R-J Yang
National Cheng Kung University, TW

hydrodynamic focusing, microchannels

In this work, we have designed and fabricated a three-dimensional hydrodynamic focusing microfluidic device, as shown in Figure 1. The design of the device is modified from that of a previous study [1], which comprises two-layers PDMS microchannels structure. Sample flow is injected from B channel (bottom layer), the sheath flows for z-direction focusing are injected from A channel (upper layer ) and C channel (bottom layer), respectively, and that for y-direction focusing is injected from D channel (upper layer). The flows are all injected by syringe pumps. In the previous design [1], the perfect z-direction (vertical) focusing effect requires high aspect ratio (channel height-to-width, ~6) of the main channel. However, it can be achieved in lower aspect ratio (~ 0.95) microchannel in the design of this current study. Figure 2 show the numerical and experimental images of the focused stream shape from cross-section perspective. The experimental ones were captured using confocal fluorescence microscope. We have also investigated the effect of Reynolds number on the vertical focusing effect using CFD simulation. The results show that the rectangular-like shaped of the focused stream from cross-section perspective was deformed as the Reynolds number is high due to secondary flows was produced. In other words, the chip works well at low Reynolds number. The device can be integrated into an on-chip flow cytometer.

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