Controllable Fabrication Of Superhydrophobic Surface Based On Porous Structure

Superhydrophobic surface has long been a focused and hot topic researches in the fields of materials, nanotechnology and surface engineering. As a new kind of superhydrophobic surface, the porous superhydrophobic membrane has the merits of simple and easy to be fabricated, existing without substrate, and more adapt to be applied in large production and practical application. But till now, the regulation mechanism has not been cleanly explained. In the present paper, two types of porous superhydrophobic surfaces, making up of the papilla-like ZnO and organic polymeric fiber respectively, were prepared, and their structures, morphologies, contact angles to water and roughness values were investigated.Papilla-like porous membrane of ZnO was fabricated via hydrothermal immersing method. The observed results on its structure and morphology showed that the amount of zinc participated in the reaction incresed with increasing of the reacting time, leading to raising amount of ZnO generation and forming more nanopores on the surfaces of the micro-sized zinc particles. When the reaction time prolonged from 6 hr to 18 hr, the average diamter of the pores on the surface of the papilloma decreased from 0.77μm to 0.33μm, the surface roughness increased from 4.96μm to 9.46μm, and the water contact angle changed from 134.5°to 157.2°. Based on the experimental observationand the wettability theory, it is suggested that a controllable fabrication of papilla-like porous superhydrophobic membrane can be materialized by adjusting the size and porosity that governed by the reacting conditions.Organic polymer fiber was prepared and found to be entwisted each other, formed a net-like porous structure, and displayed hydrophobic behavior. After pressing at 20 MPa for 1 hr, the average diameter of the pores in the porous structure decreased from 1.30μm to 0.66μm, meanwhile the water contact angle of the fiber increased from 152.1°to 155.9°. It is seemed that there was a relationship between the parameter of the porous structure and its wettability.To have a good understanding of the wettability of the as-prepared organic polymer fiber, a fiberic membrane was fabricated via shearing dispersion followed by vacuum filtration. Experimental results showed that after string, Cu in the fiber acted as catalyst had reacted with O2 and CO2 in air, changed into Cu2(OH)2CO3, and with increase of dispersing time from 5 minute to 10 minute, the water contact angle increased from 156.3°to 164.9°. Based on the wettability theory of basic solid surface, combined with the experimental results of its porous morphology, surface roughness and the water contact angle, we found that during the violent dispersing process, the fibers became more incompact. With the increase of dispersing time, orinentation degree of the fibers became higher, the average diameter of the pores formed by fibers decreased from 1.27μm to 0.73μm, meanwile the surface roughness increased from 4.12μm to 9.61μm, and the final result was the contact angle to water increased. In a word, a controllable fabrication of net-like porous superhydrophobic surface can actualized, and an adjusting superhydrophobic mechanism for the porous structured membrane is approved again.