A Real‐Time Capacitive Sensor to Detect the Stability of Salvinia Layers on Porous Superhydrophobic Polymers Under Shear

Abstract

AbstractSuperhydrophobicity can be achieved by combining sufficiently low surface energy with a suitable surface roughness. Repellency in such surfaces is the result of the so‐called Salvinia layer, a small layer of air trapped between the superhydrophobic surface and a wetting fluid that prevents the fluid touching the surface. The drawback of the Salvinia layer is its instability due to either shear forces or the air dissolving in the passing fluid. When the air layer is lost, the coating loses its superhydrophobic properties. The direct observation of air layer is of high interest for many applications, specially for determining its behavior under shear. Here, a real‐time study of Salvinia layer on a porous superhydrophobic polymer, Fluoropor, by means of a capacitive sensor under shear in water is presented. The initial thickness of the Salvinia layer on Fluoropor‐coated electrodes is measured and the time of degradation for three Fluoropor thicknesses 30, 50, and 75 µm using degassed and nondegassed water at two flow rates, i.e., 0.35 and 0.7 mL min−1 is quantified. The sensor quantitatively assesses that Salvinia layer degrades fast for thin Fluoropor layer under higher shear but remains stable for up to 17 h in nondegassed water for thicker layers.