Multi-scale pattern with surface quasi crystal for wettability tuning

Abstract

Transparent and stretchable structures with multi-scale patterns on PDMS surfaces for a tunable superhydrophobicity are presented. The samples result in the transfer of photoinduced quasi-crystal structures of azopolymer-based thin films onto an elastomer. The quasi-crystal surface patterns have different complexities generated with superimposed multiple exposures. The obtained samples can be stretched or compressed. Periodic circular nanocavities as small as 500 nm could be obtained with their shapes changed by stretching. The surface stretching or compressing induced on the elastomer surface allows the size manipulation of nanocavities. An application of these surfaces is presented for a large control of the super-hydrophobicity. The wetting of these patterns is compared to the same surface pattern modified with metal nanoparticles obtained by a metal dewetting process where the roughness is increased. We show that in this case the hydrophobicity is higher, and the droplet is sticky on these surfaces leading to a rose-petal effect.