Functional topographically patterned surfaces

The slippery zone of the carnivorous (animal eating) plants Nepenthes alata located inside the pitcher shows pronounced anti-adhesive properties. Even insects with highly developed adhesive systems cannot adhere to the slippery zone. This zone consists of three hierarchically structured levels. Lunate cells (length scale of several dozens micrometers) as the first level are covered by two waxy layers representing the second and third hierarchical levels. Inspired by the anti-adhesive properties of the slippery zone, artificial surfaces consisting of polymeric monolithic microsphere arrays within the diameter range 0.4 - 90 µm were developed. These microsphere arrays having approximately the same dimensions as the level 1 lunate cells were prepared by a double replication procedure. For preparation of synthetic anti-adhesives, two different designs, polystyrene (PS) microsphere arrays for dry adhesion and porous polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) microsphere arrays for wet adhesion tests, respectively, were investigated. The adhesion measurements showed that such surfaces exhibit pronounced anti-adhesive properties to rigid as well as to sticky and compliant counterpart surfaces. Moreover, cell culturing experiments suggest that surface topographies promote anti-fouling properties. The bioinspired design strategy reported here may provide access to bioinspired surfaces with tailored contact mechanics by simple modifications of straightforward production processes. Furthermore, the results presented here may improve understanding of the contact mechanics of biological models