On water repellency

Water-repellency is a property of some materials, either natural or synthetic, which makes water hardly stick to them: drops roll very easily off these solids, and bounce back upon impacting them. Here we discuss recent advances in this field, which has been particularly lively in recent years. We first examine the physical causes for this effect. Then we discuss the loss of adherence of the drops in such a state, and stress their remarkable dynamic behaviour. We finally suggest several remaining challenges in the field.