Ice wicking

Liquid-ice interactions are becoming increasingly relevant for many applications including hydraulic fracturing, arctic drilling, and liquid-impregnated surfaces. It is therefore surprising that the capillary action of a liquid wicking across the surface of ice has never been characterized. We observe silicone oil as it wicks up sheets of frost grown on vertically oriented aluminum surfaces of varying wettability. Superhydrophilic and hydrophilic surfaces promote the growth of continuous frost sheets which displace oil with a power-law slope of 1/3 with respect to time. While in contrast to the 1/2 slope of Washburn's law governing most porous media, the 1/3 slope can be rationalized by considering the dendritic frost structure as an array of vertical wedges incapable of supporting the liquid's weight. Nonwetting surfaces grow frost from a more dilute distribution of frozen dropwise condensate, resulting in lower slopes of 1/4 for hydrophobic surfaces and nearly zero for superhydrophobic surfaces promoting jumping-droplet condensation. When switching to a near-horizontal orientation, Washburn's law is obtained for continuous frost sheets. The spreading rate of a liquid across frost can therefore be controlled by tuning the underlying surface wettability or surface orientation. Finally, we show that oils cannot wick inside of a bulk volume of frozen water due to the small pore size of the hexagonal lattice structure.