Ice-phobic Surfaces That Are Wet

Ice formation on surfaces and structures produces damage and inefficiencies that negatively impact all manners of activities. Not surprisingly, for a long time, an unmet challenge has been to design materials capable of minimizing or even eliminating the formation of ice on the surface of the material. In recent years, there were significant efforts to develop such ice-phobic surfaces by building on the advances made with superhydrophobic materials since these, by definition, tend to repel water. However, a robust response includes the ability to deter the formation of ice when a substrate colder than the freezing temperature is exposed either to impacting water droplets or water vapor (i.e., frost formation). In the latter case, superhydrophobic surfaces in high humidity conditions were shown to allow significant ice accumulation. Consequently, a new design idea was needed. In this issue of ACS Nano, it is shown how a liquid-infiltrated porous solid, where the liquid strongly wets and is retained within the material, has many of the properties desired for an ice-phobic substrate. The composite material exhibits low contact angle hysteresis so only small forces are needed to provoke droplets to slide off of a cold substrate. This new slippery surface shows many characteristics required for ice-phobicity, and a method is demonstrated for applying this kind of material as a coating on aluminum. Ice may have met its match.