Why superhydrophobic surfaces are not always icephobic.

We discuss mechanical forces that act upon a water droplet and a piece of ice on a rough solid surface and the difference between dewetting and ice fracture. The force needed to detach a water droplet depends on contact angle (CA) hysteresis and can be reduced significantly in the case of a superhydrophobic surface. The force needed to detach a piece of ice depends on the receding CA and the initial size of interfacial cracks. Therefore, even surfaces with very high receding CA may have strong adhesion to ice if the size of the cracks is small.