Microdevice end pressure evaluations with Bagley correction

Abstract

In this study the end pressure of microdevices is derived through Bagley corrections with the use of an off-chip pressure transducer. Such approach has many advantages over the approaches using on-chip pressure transducers. In this study it has been used to measure the non-Newtonian fluid flow at the ends of microdevices. The experimental microdevices had a microchannel with a cross section of 149×158 μm2, end angles of 36° or 180°, a contraction ratio of 24, and a reservoir aspect ratio of 0.04. Two linear aqueous polymer solutions which have very different entry flow patterns were tested. Experimental results disclosed that the end pressures of microdevices are dominated by the excess pressure before the contraction plane. This is different from the conventional fluidics conclusions, which consider the kinetic energy change and/or the excess pressure from the boundary layer formation being the dominant sources of the end pressure. This discrepancy also explains why many earlier microfluidics studies observed higher frictional factors in microdevices. Determined by the unique device characteristics, microdevices have exhibited higher end pressures than macrodevices. The microdevice end angle has negligible effects on the end pressure.