Experimental investigation of flow transition in microchannels using micron-resolution particle image velocimetry

Microchannel heat sinks are promising for cooling applications in advanced electronic systems. More research is needed to understand microchannel flow regimes. Recent pressure drop data in microchannels with hydraulic diameters between 50 and 300 /spl mu/m suggest that the transition to turbulence may occur at lower than expected values of the Reynolds number. This work studies turbulent transition in microchannels using micron-resolution particle imaging velocimetry (/spl mu/PIV) with epifluorescent microscopy of 950 nm particles. Silicon channels with dimensions 150 /spl mu/m/spl times/100 /spl mu/m/spl times/1 cm are fabricated using deep reactive ion etching and sealed using a glass plate. Velocity field data for 200Re>1600, which is lower than values near 2200 measured previously for larger channels with similar shapes. This discrepancy may be caused by wall roughness, viscous heat generation, or electrokinetic effects. The experimental approach developed here provides the groundwork for a detailed study of turbulence transition in microchannels.