Using Flame Spray to Make Surfaces Liquid Repellent
Potential applications of highly liquid-repellent surfaces range from protective and self-cleaning textiles, goggles and windows through to medical devices and gas exchange membranes. Applications for liquid-repellent coatings depend not only on their wetting properties, but also on their transparency, robustness, as well as the cost and speed of the production process.
Scientists at the Max Planck Institute for Polymer Research in Mainz, Germany, and Tampere University of Technology in Finland have found a new way of applying a structured coating that repels liquids. Besides its highly liquid-repellent properties, this new coating shows high transparency and withstands impacting high-velocity oil and water drops. These extraordinary properties are based on a specific structure of the coating composed of silicon dioxide–titanium dioxide particles. The method can be scaled up to provide a type of protective coating for large surface areas. By using liquid flame spray, the method is also extremely fast and even highly flammable materials such as paper and wood can be coated.
The scientists have combined this fast and scalable processing method with its liquid-repellent properties and established criteria that the coating must meet in order to meet all requirements for liquid repellency. They described in detail how they managed to optimise the coating structure to meet these criteria. Liquid flame spray can be used to synthesise a wide range of oxides, metal nanoparticles and their mixtures, which is why this strategy can be implemented to produce coatings made of different materials for a variety of applications.