Steinberger Audrey, Cottin-Bizonne Cécile, Kleimann Pascal, Charlaix Elisabeth
Université de Lyon, CNRS UMR 5586, Laboratoire PMCN, F-69622 Villeurbanne, France.
Nat Mater. 2007 Sep;6(9):665-8. doi: 10.1038/nmat1962. Epub 2007 Jul 22.
Reducing the friction of liquid flows on solid surfaces has become an important issue with the development of microfluidics systems, and more generally for the manipulation of fluids at small scales. To achieve high slippage of liquids at walls, the use of gas as a lubricant--such as microbubbles trapped in superhydrophobic surfaces--has been suggested. The effect of microbubbles on the effective boundary condition has been investigated in a number of theoretical studies, which basically show that on flat composite interfaces the magnitude of the slippage is proportional to the periodicity of the gaseous patterns. Recent experiments aiming to probe the effective boundary condition on superhydrophobic surfaces with trapped bubbles have indeed shown high slippage in agreement with these theoretical predictions. Here, we report nanorheology measurements of the boundary flow on a surface with calibrated microbubbles. We show that gas trapped at a solid surface can also act as an anti-lubricant and promote high friction. The liquid-gas menisci have a dramatic influence on the boundary condition, and can turn it from slippery to sticky. It is therefore essential to integrate the control of menisci in fluidic microsystems designed to reduce wall friction.
随着微流体系统的发展，更广泛地说，对于小尺度下流体的操控而言，降低液体在固体表面的摩擦力已成为一个重要问题。为了实现液体在壁面的高滑移，有人提出使用气体作为润滑剂，比如被困在超疏水表面的微气泡。在一些理论研究中已经探讨了微气泡对有效边界条件的影响，这些研究基本上表明，在平坦的复合界面上，滑移的大小与气态图案的周期性成正比。最近旨在探测带有被困气泡的超疏水表面上有效边界条件的实验确实表明，高滑移与这些理论预测相符。在此，我们报告了在带有校准微气泡的表面上进行的边界流纳米流变学测量。我们表明，被困在固体表面的气体也可以起到抗润滑剂的作用并促进高摩擦力。液 - 气弯月面对边界条件有显著影响，并且可以使其从光滑变为粘性。因此，在旨在降低壁面摩擦的流体微系统中，整合对弯月面的控制至关重要。
