Synthesis of superhydrophobic surfaces by polytetrafluoroethylene coating on rectangular grid microstructures

Abstract

A simple process to synthesize superhydrophobic surfaces by deep reactive ion etching (DRIE) and polytetrafluoroethylene (PTFE) coating of rectangular grid structures on Si substrate was developed. The Si substrate possesses unique quadrilateral network-type Si microstructures, which when sputtered upon with PTFE, creates a superhydrophobic surface. The fluorinated polymer also exhibited hydrophobic properties where the contact angle of the Si substrate after the PTFE coating was 108.4°. The DRIE etching and PTFE coating together increased the contact angle up to 158.6°for a 40 μm height and 10 × 10 m 2 area, thus synergistically increasing the hydrophobicity of the surface.

Ag-enriched TiO2 nanocoating apposite for self-sanitizing/ self-sterilizing/ self-disinfecting of glass surfaces

“…The conditions for super-hydrophobicity are a very high static water contact angle greater than 160°, and a very low inclination angle lesser than 5° necessary for a spherical droplet to roll off the surface [ 9 ]. However, on a smooth surface, it is not possible to exceed 120° contact angle by means of chemical hydrophobicity [ 10 ]. Hence, super-hydrophobicity requires tuning of surface roughness on nanoscale which can be possibly achieved through sophisticated fabrication techniques but at very high production costs besides being inappropriate for large-scale production of superhydrophobic surfaces.…”

“…Thus, silver-enriched titania (Ag–TiO 2 ) multifunctional nanocoating with super-hydrophilic property not only keeps the hydrophobic glass surface free from clogged grime but also chemically breaks down the adsorbed hydrocarbons, disinfects pathogens, and sanitizes microorganisms. Recent studies have elucidated that Ag incorporated TiO 2 coatings are more effective to combat COVID-19 and the related viral genomic RNA compared to bare TiO 2 [ 1 , 11 , [15] , [16] , [17] ].…”