Delayed Freezing on Water Repellent Materials

Water drops on hydrophobic microtextured materials sit on a mixture of solid and air. In standard superhydrophobic situations, the drop contacts more air than solid, so that we can think of exploiting the insulating properties of this sublayer. We show here that its presence induces a significant delay in freezing, when depositing water on cold solids. If the substrate is slightly tilted, these drops can thus be removed without freezing and without accumulating on the substrate, a property of obvious practical interest.