Microstructured nematic liquid crystalline elastomer surfaces with switchable wetting properties

Inspired by the lotus leaf, scientists have developed many superhydrophobic surfaces, some of which show remarkable switching between hydrophobic and hydrophilic state under external stimuli. However, the switch usually relies on the change of chemical properties rather than on the modification of the topographic structure of the surface. In this paper, the roughness-change-related switchable wetting properties of microstructured responsive surfaces made of nematic liquid crystalline elastomers (LCEs) is reported. First, various carbonate LC monomers and side-on LCEs are synthesized with low nematic-to-isotropic transition temperature, TNI. Then, LCEs prepared from 3-vinylcarbonyloxypropyl 2,5-di(4-octyloxybenzoyloxy)benzoate monomer, with TNI of 76 degrees C and contraction of 34% are used to construct a surface covered with micropillar arrays by using a replica molding technique. The contraction of the micropillars induces a reversible roughness change of the microstructured surface. Water contact angle of this microstructured surface changed with temperature, indicating a successful approach at building a surface with switchable wetting properties.