The fabrication of robust superhydrophobic 3D porous materials is of great importance for both academic research and industrial applications. The main challenge is the poor adhesion between porous substrates and superhydrophobic coatings. In this study, a robust superhydrophobic polysiloxane layer was coated onto the surface of 3D porous polyurethane sponges through a one-step solution immersion method.The durability of the resulting sponges was investigated by repeated mechanical compressions, ultrasonication in polar solvents, and strong acid/alkali attacks. Results revealed that the superhydrophobic sponges showed excellent elasticity, high mechanical durability and good chemical stability. By combining the special wettability and high porosity, the sponges exhibited high oilabsorption capacity and high selectivity when they were employed as absorptive materials for cleaning oils on the water surface. More importantly, the superhydrophobic sponges could be reused for oil-water separation for more than 300 cycles without losing their superhydrophobicity, exhibiting the highest reusability and durability among the reported counterparts. Therefore, the present study offers a simple and low-cost strategy for large-scale fabrication of robust superhydrophobic 3D porous materials that might be applied to the cleanup of oil spills on the water surface.
Superhydrophobic surfaces with tunable water adhesion have attracted much interest in fundamental research and practical applications. In this paper, we used a simple method to fabricate superhydrophobic surfaces with tunable water adhesion. Periodic microstructures with different topographies were fabricated on copper surface via femtosecond (fs) laser irradiation. The topography of these microstructures can be controlled by simply changing the scanning speed of the laser beam. After surface chemical modification, these as-prepared surfaces showed superhydrophobicity combined with different adhesion to water. Surfaces with deep microstructures showed self-cleaning properties with extremely low water adhesion, and the water adhesion increased when the surface microstructures became flat. The changes in surface water adhesion are attributed to the transition from Cassie state to Wenzel state. We also demonstrated that these superhydrophobic surfaces with different adhesion can be used for transferring small water droplets without any loss. We demonstrate that our approach provides a novel but simple way to tune the surface adhesion of superhydrophobic metallic surfaces for good potential applications in related areas.
Realizing superhydrophobicity, high transparency on polydimethylsiloxane (PDMS) surface enlarges its application fields. We applied a femtosecond laser to fabricate well-designed structures combining microgrooves with microholes array on mirror finished stainless steel to form a template. Then liquid PDMS was charged for the duplicating process to introduce a particular structure composed of a microwalls array with a certain distance between each other and a microprotrusion positioned at the center of a plate surrounded by microwalls. The parameters such as the side length of microwalls and the height of a microcone were optimized to achieve required superhydrophobicity at the same time as high-transparency properties. The PDMS surfaces show superhydrophobicity with a static contact angle of up to 154.5 ± 1.7° and sliding angle lower to 6 ± 0.5°, also with a transparency over 91%, a loss less than 1% compared with plat PDMS by the measured light wavelength in the visible light scale. The friction robust over 100 cycles by sandpaper, strong light stability by 8 times density treatment, and thermal stability up to 325 °C of superhydrophobic PDMS surface was investigated. We report here a convenient and efficient duplicating method, being capable to form a transparent PDMS surface with superhydrophobicity in mass production, which shows extensive application potentials.
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