Capillary-flow dynamics in open rectangular microchannels

Abstract

Abstract

Capillary flow of liquids in open microchannels: overview and recent advances

“…1a ), for open channels the additional free surface due to the lack of a top also contributes to driving the flow (Fig. 1b–d ) 15 .…”

“…Due to breakthroughs in lithographic fabrication techniques, open microchannels with various cross-sectional geometries (Fig. 1b–d ) can be fabricated easily and inexpensively, including rectangular 14 , 15 , 35 – 37 , trapezoidal 38 , U-shaped 35 , and V-shaped 39 – 43 cross-sections. The lack of a top provides access to the inside of the channel and has been exploited in applications such as capillary micromoulding and microfluidics.…”

“…In these studies, while the scaling of still holds, the expression for the mobility parameter depends on the cross-sectional geometry. However, predictions from these modified Lucas–Washburn models (MLWs) for open channels have resulted in a varying agreement with experiments 14 , 15 , 24 , 35 , 36 , 38 . This is because the mechanism for capillary flow in open channels is more complex than that for closed channels.…”

“…Recently, Kolliopoulos et al 15 used a combination of theory and experiment to examine capillary-flow dynamics in open rectangular microchannels with negligible gravitational effects. Scanning electron microscopy and profilometry were used to highlight the complexity of the free-surface morphology.…”

“…Notably, the channels involved have widths and depths of tens to hundreds of microns so that surface tension, i.e., capillary forces play a key role in driving flow. The importance of capillary flow and evaporation in open microchannels along with recent insights obtained through an interplay between theory and experiment 14 , 15 make this Perspective article particularly timely, and we hope it will inspire others to advance both the fundamentals and applications related to this topic. We first discuss capillary-flow dynamics in the absence of liquid evaporation, and then consider the influence of evaporation.…”