The use of superhydrophobic surfaces in confined flows is of particular interest as these surfaces have been shown to exhibit a drag reduction effect that is orders of magnitude larger than those due to molecular slip. In this paper we present experimental results of the pressure-driven flow of water in a parallel-plate microchannel having a no-slip upper wall and a superhydrophobic lower wall. Pressure-drop versus flow-rate measurements characterize the apparent slip behavior of the superhydrophobic surfaces with varying pillar-to-pillar pitch spacing and pillar diameter. The superhydrophobic surface consists of a square array of cylindrical pillars that are fabricated by deep reactive ion etching on silicon and coated with a hydrophobic fluoropolymer. A major challenge, in correlating our experimental results with existing theoretical predictions, is uncertainty in the location of the gas/liquid interface and the associated gas/liquid/solid contact line within the pillar features comprising the superhydrophobic surface. We present experimental results, from laser-scanning confocal microscopy, that measure the location of the gas-liquid interface and associated contact line for fluid flowing through a parallel-plate microchannel. Knowledge of the contact line location is then used to correlate experimental pressure-drop versus flow-rate data with a theoretical model based on porous-flow theory that takes into account partial penetration of liquid into a superhydrophobic surface.
- Nanotechnology Institute
Effects of Interfacial Position on Drag Reduction in a Superhydrophobic Microchannel
Enright, R, Dalton, T, Krupenkin, TN, Kolodner, P, Hodes, M, & Salamon, TR. "Effects of Interfacial Position on Drag Reduction in a Superhydrophobic Microchannel." Proceedings of the ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. Darmstadt, Germany. June 23–25, 2008. pp. 835-845. ASME. https://doi.org/10.1115/ICNMM2008-62251
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