Ultra-wetting surfaces have broad prospects for applications in self-cleaning, fluid drag reduction, oil and water separation, anti-fog and other fields, which have drawn widespread attention. However, with poor mechanical stability, traditional ultra-wetting surfaces do not cope well with complex physical contact, making their applications extremely limited. Recently, Professor Wang Chengyu’s research team from the College of Material Science and Engineering (Ministry of Education Key Laboratory of Biomaterial Science and Technology) proposed an idea of producing mechanically stable ultra-wetting surfaces, and accordingly they designed and produced super-hydrophilic / underwater ultra-oleophobic surface and super-hydrophobic surface, both of which have excellent mechanical stability. This scientific research paper was published in ACS Applied Materials & Interfaces (DOI: 10.1021/acsami.7b02158).
According to master’s student Zhang Wenbo, the first author of the paper, to enhance the wear resistance of the ultra-wetting coating is very significant for the practical application of the ultra-wetting surfaces. At present, enhancing the wear resistance of the ultra-wetting surfaces mainly depends on the construction of the micro-nano binary coating structure or the use of commercial adhesives to enhance the adhesion of the coating and the substrate, but these two methods are both limited in upgrading the ultra-wetting coating stability, and the problem of poor microstructure strength of the ultra-wetting coating is unsolved. Through the reasonable choices and matches of coating materials and bonding technologies, the team has successfully produced two kinds of mechanically stable ultra-wetting surfaces: 1. Taking micron-grade silica and nylon as coating materials, they fix the coating on the surface of the substrate through a new adhesive swelling process, resulting in a super-hydrophilic / underwater ultra-oleophobic surface; 2. Taking the compressed polyurethane foam and nano-titanium dioxide as coating materials, they adhere the coating to the surface of the substrate through a simple adhesive bonding process, resulting in a super-hydrophobic surface. These two surfaces can withstand the friction length of 70cm and 1000cm with 600 mesh sandpaper at 24 kpa. There is no decline in ultra-wetting performance, which achieves the best wear resistance currently. When the two surfaces are worn by sandpaper, the rough structure of the coating surface will fall off, but the coating has a perfect strength and a continuous rough structure, so the newly exposed surface remains the original roughness morphology and ultra-wetting performance can be maintained. This “wear-off” mechanism allows this ultra-wetting surface to be much better than the conventional ultra-wetting surface, and the wear can also be used to quickly repair the damaged or contaminated coating areas, so that the ultra-wetting performance regenerates. In general, this work provides a new design idea for the production of ultra-wetting surfaces with mechanical stability or rapid self-repairing ability, which is useful for systematically studying the mechanical stability of ultra-wetting surfaces.
This research has been supported by the National Natural Science Foundation of China and the Fundamental Research Fund of the Central University.