Supersonically sprayed transparent flexible multifunctional composites for self-cleaning, anti-icing, anti-fogging, and anti-bacterial applications

We used supersonic aerosol deposition to fabricate transparent flexible thin “glass” films, comprising SiO₂ and ZnO, with antibacterial, superhydrophilic, and anti-fog properties. A polystyrene solution, which was supersonically sprayed onto the glass film to augment the superhydrophobicity, endowed the film with self-cleaning and anti-frost characteristics. The glass films have a thickness of 2–2.5 μm with a maximum roughness of approximately 0.25 μm. The sprayed polystyrene (PS) layer (approximately 200 nm thick) decreased the transparency of the film to 80% relative to that of the pure glass film (90%) at 580 nm. The large water contact angle of 165° renders the PS-coated glass film superhydrophobic, which slows the nucleation of condensing droplets and delays the subsequent formation of ice, known as the anti-frost or anti-icing effect. The superhydrophobicity is also responsible for the self-cleaning effect of the rolling droplets over a tilted substrate. The hydrophilicity of the glass-coated film (or simply, glass film) without PS facilitated the formation of a thin liquid layer, which minimized light scattering and augmented the anti-fog effect. Finally, the bacterial inhibition rates of the glass and PS-coated glass films were 97.5% and 96.3%, respectively. These multifunctional films are expected to minimize the transmission of bacteria resulting from physical contact.