Capillary-Enhanced Biomimetic Adhesion on Icy Surfaces for High-Performance Antislip Shoe-Soles

Abstract

The World Health Organization (WHO) reports 684,000 deaths/year due to slips and falls (SFs), with ∼38 million people requiring medical attention per annum. In particular, SFs on ice surfaces account for 45% of all SF incidents, costing over $100 billion globally in healthcare, intensive care, and insurance expenses. Current antislip solutions focus on hydrophobicity to repel interfacial fluids, aiming to maintain solid-to-solid contact. However, these solutions often wear out quickly, clog, or become ineffective. Wet ice is particularly challenging due to its nanometer-thick quasi-liquid layer (QLL), which makes it extremely slippery. Inspired by the capillary suction adhesion observed in gecko footpads and the slip resistance of frog toepads on wet surfaces, we developed an innovative approach to regulate ice adhesion and deadhesion. The solution presented in this work mimics this mechanism by employing textured microcavities into silicone rubber (SR)/zirconia (ZrO₂) closely mirroring the properties of gecko and frog toepads. Given the dynamics of walking, the surface exhibited hydrophilicity-induced capillary suction of the QLL, facilitating their rapid frost to achieve greater mechanical interlocking. The developed textures displayed capillary suction within 1.5 ms, resulting in a maximum friction coefficient of 3.46 on wet ice. This breakthrough outcome provides a robust, durable solution to significantly reduce SFs on ice surfaces, saving lives and livelihoods.