Fabrication Of Biomimetic Self-cleaning Surfaces Inspired From Lotus Leaf And Silver Ragwort Leaf Via Electrospinning

Superhydrophobic surfaces with water contact angle larger than 150°have bright future for various applications both in the industrial world and people's daily life. It also attracted tremendous interests of scientists during the past few years.There are many ways for creating superhydrophobic surfaces, which is believed to be governed by chemical composition and morphological structures presented on a surface. Numerous studies have demonstrated that materials with a combination of extremely low surface energy and roughened surface structures are indispensable for superhydrophobic surfaces. PS's surface energy is quite low, so this research is focused on the aspect of roughened surface structures.Many plants with hydrophobic surfaces are found in nature, such as lotus leaf, silver ragwort leaf. The micro-scaled bumps as well as the nano-scaled hair-like structures are covered on the surfaces of lotus leaf. The silver ragwort leaf is covered by numerous micro-scale and nano-scale grooves along the fiber axis. These structures ensure high roughness and large contact angle of surfaces. This research aims at combining the characteristics of both lotus leaf and silver ragwort leaf to create biomimic superhydrophobic fibrous mats. Inspired by the self-cleaning lotus leaf and silver ragwort leaf, we demonstrate the fabrication of biomimetic superhydrophobic fibrous mats via electrospinning polystyrene (PS) solution in the presence of silica nanoparticles. The resultant electrospun fibers' surfaces exhibited a fascinating structure with the combination of nano-protrusions and numerous grooves due to the rapid phase separation during the electrospinning process. The content of silica nanoparticles incorporated into the fibers was proved to be the key factor to affect the fiber surface morphology and hydrophobicity. The PS fibrous mats containing 14.3 wt% silica nanoparticles showed a stable superhydrophobicity with water contact angle as high as 157.2°, exceeding that (147°) of the silver ragwort leaf and accessing that (160°) of the lotus leaf. The superhydrophobicity was that the hierarchical surfaces increased the surface roughness which trapped more air under the water droplets that fell on the fibers.Physical techniques including FE-SEM, WCA, AFM, FTIR were applied to investigate characteristic of the fibrous mats. Wenzel and Cassie theory were also applied to analysis the results. The contents of silica nanoparticles and the kind of solvent were proved to be the key factors to affect the electrospun PS-Silica fiber surface morphology and hydrophobicity.In addition, this research extended this method to PMMA and fabricated significantly improved hydrophobic PMMA-Silica composite fibrous mats by one step approach.