The clogging pressure of bubbles in hydrophilic microchannel contractions

Abstract

We present a theoretical and numerical study of the quasi-static motion of large wetting bubbles in microfluidic channels with contractions. In most cases the energy of a bubble increases when it is moved from a wide channel to a narrow one, and the bubble thus tends to clog the flow of the fluid. A certain pressure, the so-called clogging pressure, is needed to push the bubbles out of the contraction. However, we show that in the case of a hydrophilic channel contraction there exists a range of parameter values where the bubble actually gains energy by moving into the narrow part. For these specific cases we analyze how the clogging pressure depends on channel geometry, surface tension and contact angle. Based on our analysis we establish design rules for minimizing the clogging pressure of microchannel contractions.