Fluorine-free, liquid-repellent surfaces made from ionic liquid-infused nanostructured silicon

Liquid-repellent surfaces based on slippery liquid-infused porous substrates (SLIPS) were prepared from porous, nanostructured silicon surfaces with different surface functionalization, infused with the polar ionic liquid 1-ethyl-3-methylimidazolium methylsulfate ([C₂mim]MeSO₄). Contrary to nonpolar SLIPS based on perfluorinated substrates and infusion liquids, [C₂mim]MeSO₄ forms stable SLIPS with high energy surfaces like native silicon (Si-SiO₂) or ionic liquid-functionalized silicon (Si-[C₃mim]Cl), whose liquid-repellent properties against low surface tension liquids (toluene, cyclohexane) were demonstrated by very low sliding angles (α < 3°) and low contact angle hysteresis (Δθ < 10°). These polar, ionic liquid-based SLIPS present a promising, environmentally benign extension of liquid-infused substrates to natural, high-energy oxide surfaces.