Fabrication of biomimetic superhydrophobic surfaces inspired by lotus leaf and silver ragwort leaf

Inspired by the self-cleaning lotus leaf and silver ragwort leaf, here we demonstrate the fabrication of biomimetic superhydrophobic fibrous mats via electrospinning polystyrene (PS) solution in the presence of silica nanoparticles. The resultant electrospun fiber surfaces exhibited a fascinating structure with the combination of nano-protrusions and numerous grooves due to the rapid phase separation in electrospinning. The content of silica nanoparticles incorporated into the fibers proved to be the key factor affecting the fiber surface morphology and hydrophobicity. The PS fibrous mats containing 14.3 wt% silica nanoparticles showed a stable superhydrophobicity with a water contact angle as high as 157.2 degrees, exceeding that (147 degrees) of the silver ragwort leaf and approaching that (160 degrees) of the lotus leaf. The superhydrophobicity was explained by the hierarchical surfaces increasing the surface roughness which trapped more air under the water droplets that fell on the fibers.