Phys.org July 26, 2021
A team of researchers in the US (Virginia Tech, UC Santa Barbara) created a de-icing method based on Cassie’s Law, which shows that air can be trapped under water drops if the drops are suspended atop a structure that is bumpy and water-repellent. They sought to make ice form in a layer with lower adhesion to the surface. They created an array of pillars, each one millimeter tall by half a millimeter wide. The tiny pedestals were machined into a pattern with a millimeter between the pillars. As the temperature dropped, frost preferentially grew on the tops of the pillars, resulting in elevated frost tips. As more water was added, it was absorbed into this porous frost layer. When water drops were subsequently impacted on the surface, they were caught on the frost pedestals. These freezing drops created tiny “ice bridges,” that sealed the gaps of air in the valleys between the frost-tipped pillars trapping air pockets underneath. Over time, it formed an air-trapping ice canopy over the frost-tipped pillars causing the sheet to be suspended, lowering the amount of adhesion ice has to the surface. With a weaker bond, it’s possible to use the air pockets to then push ice away…read more. TECHNICAL ARTICLEÂ
Model schematic for predicting whether frost-tipped pillars can trap an impacting supercooled droplet in the Cassie state. Credit: Phys. Rev. Lett. 127, 044501, 22 July 2021Â