Proc. Natl Acad. Sci. USA 109, 16073–16078 (2012 )

The formation of frost on solid surfaces limits the performance and safety of many technologies, most notably in aviation. Significant efforts have therefore focused on developing so-called icephobic surfaces that slow down or even suppress the formation of ice. However, their performance is strongly affected by environmental conditions such as humidity and shearing gas flow and, as Dimos Poulikakos and colleagues now demonstrate, also the thermal conductivity of the surface. The researchers examine the physics of ice formation in supercooled water droplets on different surfaces, and show that their evaporation — which starts explosively as a result of the latent heat released on impact — generates a condensation halo around each droplet, which in turn crystallizes into ice. Poulikakos and co-workers establish that the size of the frost halo depends, through a delicate balance between heat diffusion and vapour transport, on the thermal conductivity of the substrate: the droplets forming on a polymer surface have larger halos than those on titanium and copper, suggesting that good thermal conductors may be effective in minimizing ice formation and frost propagation.