Quantitative Testing of Robustness on Superomniphobic Surfaces by Drop Impact

Abstract

The quality of a liquid-repellent surface is quantified by both the apparent contact angle θ₀ that a sessile drop adopts on it and the value of the liquid pressure threshold the surface can withstand without being impaled by the liquid, hence maintaining a low-friction condition. We designed surfaces covered with nanowires obtained by the vapor−liquid−solid (VLS) growth technique that are able to repel most of the existing nonpolar liquids including those with very low surface tension as well as many polar liquids with moderate to high surface tension. These superomniphobic surfaces exhibit apparent contact angles ranging from 125 to 160° depending on the liquid. We tested the robustness of the surfaces against impalement by carrying out drop impact experiments. Our results show how this robustness depends on Young’s contact angle θ₀ related to the surface tension of the liquid and that the orientational growth of nanowires is a favorable factor for robustness.