Highly-transparent slippery liquid-infused porous surfaces made with silica nanoparticulate thin films

In this work, highly-transparent slippery liquid-infused porous surfaces (SLIPSs) were fabricated by an aqueous electrostatic layer-by-layer assembly process with silica nanoparticles and polyelectrolytes on glass substrate, followed by high temperature sintering, silanization, and infusion of perfluoropolyether liquid lubricant. The tuning of liquid-repellency and transparency resulted in a near optimum SLIPS of 15 body bilayers with the average transmittance of 95.9% in the visible light region of 400 nm-800 nm and the highest transmittance = 96.9% at 707 nm. The SLIPSs exhibited extreme liquid repellency as signified by very low sliding angles against seven pure liquids with surface tension ranged from 72.8 to 18.6 mN/m, including water, ethylene glycol, pentadecane, nonane, octane, heptane, and hexane. Via the method based on ellipsometry to determine the refractive index and porosity of the nanoporous thin films, a porosity of 29% was estimated for the near optimum SLIPS. Taken together, we demonstrated the highly-transparent slippery surfaces with omniphobicity developed from porous superhydrophilic nanoparticulate thin films through hydrophobization and liquid lubricant infusion, where the high optical transmittance of the as-fabricated SLIPS can be explained by the experimentally determined refractive indices of the nanoparticulate thin film.