期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2013
卷号：110
期号：21
页码：8422-8426
DOI：10.1073/pnas.1304403110
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Tailoring the hydrodynamic boundary condition is essential for both applied and fundamental aspects of drag reduction. Hydrodynamic friction on superhydrophobic substrates providing gas-liquid interfaces can potentially be optimized by controlling the interface geometry. Therefore, establishing stable and optimal interfaces is crucial but rather challenging. Here we present unique superhydrophobic microfluidic devices that allow the presence of stable and controllable microbubbles at the boundary of microchannels. We experimentally and numerically examine the effect of microbubble geometry on the slippage at high resolution. The effective slip length is obtained for a wide range of protrusion angles,{theta} , of the microbubbles into the flow, using a microparticle image velocimetry technique. Our numerical results reveal a maximum effective slip length, corresponding to a 23% drag reduction at an optimal{theta} {approx} 10{degrees}. In agreement with the simulation results, our measurements correspond to up to 21% drag reduction when{theta} is in the range of -2{degrees} to 12{degrees}. The experimental and numerical results reveal a decrease in slip length with increasing protrusion angles when{theta} {gtrsim} 10{degrees}. Such microfluidic devices with tunable slippage are essential for the amplified interfacial transport of fluids and particles.
