Towards ultrahydrophobic surfaces: a biomimetic approach

We report on efforts to mimic the wetting behaviour of surfaces or leaves of certain plants, which are rendered ultrahydrophobic through a dense layer of hairs grown on top of the leaf. We use a simple moulding approach to obtain elastic hydrophilic hydrogel networks with pillar structures that may serve as model systems for such hairy surfaces. In order to generate such structures, we first generate either a steel master or directly use a lady's mantle leaf. Second, the master is moulded against a silicone to yield an elastomer, which is a negative of the hairy surface. A subsequent radical polymerization in the negative leads to the formation of an elastic hydrogel even for the very high aspect ratios characteristic of the natural system. The results of some preliminary contact angle measurements on the obtained structures are discussed.