National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, SO17 1BJ, UK.
Chemistry, University of Southampton, SO17 1BJ, UK.
Soft Matter. 2017 Feb 15;13(7):1413-1419. doi: 10.1039/c6sm02820a.
Previously superhydrophobic surfaces have demonstrated effective drag reduction by trapping a lubricious gas layer on the surface with micron-sized hydrophobic features. However, prolonged reduction of drag is hindered by the dissolution of the gas into the surrounding water. This paper demonstrates a novel combination of superhydrophobic surface design and electrochemical control methods which allow quick determination of the wetted area and a gas replenishment mechanism to maintain the desirable gas filled state. Electrochemical impedance spectroscopy is used to measure the capacitance of the surface which is shown to be proportional to the solid/liquid interface area. To maintain a full gas coverage for prolonged periods the surface is held at an electrical potential which leads to hydrogen evolution. In the desired gas filled state the water does not touch the metallic area of the surface, however after gas has dissolved the water touches the metal which closes the electrochemical circuit causing hydrogen to be produced replenishing the gas in the surface and returning to the gas filled state; in this way the system is self-actuating. This type of surface and electrochemical control shows promise for applications where the gas filled state of superhydrophobic surfaces must be maintained when submerged for long periods of time.
先前的超疏水表面通过在微米级疏水特征的表面上捕获润滑性气体层来有效地减少阻力。然而，气体溶解在周围的水中会阻碍阻力的持续降低。本文展示了一种超疏水表面设计和电化学控制方法的新组合，该组合允许快速确定润湿面积和气体补充机制，以维持理想的充气状态。电化学阻抗谱用于测量表面的电容，结果表明电容与固/液界面面积成正比。为了长时间保持完全充气状态，表面保持在导致析氢的电势下。在期望的充气状态下，水不会接触表面的金属区域，但是在气体溶解后，水会接触金属，从而关闭电化学回路，导致产生氢气以补充表面中的气体并返回到充气状态；通过这种方式，系统是自动操作的。这种表面和电化学控制对于需要长时间浸泡在充气状态下的超疏水表面的应用具有很大的应用前景。
