Microflows in complex channels with uneven surface often display unusual flow behavior compared to their macroscale counterparts. Channels with micro ridges are created in a plastic device using photolithography and molding. Recirculation is reported in the flow in these ridged channels [1]. We use recirculation to enhance fluid mixing and the utility is demonstrated by homogenizing fluorescein and water in the microchannels. In addition, deconvolution microscopy is developed to visualize the fluid flow in the ridged channel. Flow twisting, as expected, results in enhanced fluid mixing; the fluorescence intensity at a cross section is calculated as an indicator of the degree of mixing. The preliminary results show rapid mixing in the ridged channels, verifying existence of circulation. We also compared the experimental results with that from computational fluid dynamics simulation.

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