Ultra-low ice-substrate adhesion and self-deicing during droplet impact freezing

Abstract

A water droplet impacting onto a supercooled surface is typically considered to freeze and adhere to the substrate. This ice accretion poses safety and economic threats to transportation infrastructure, power generation/transmission systems, and telecommunication facilities. Here we report the observation of ultra-low ice-substrate adhesion (0–50 kPa) and remarkable self-deicing during droplet-impact freezing on copper surfaces having medium to high supercooling (30°C–80°C). Mechano-thermo-hydraulic coupling during droplet-impact freezing governs the ice-substrate adhesion by gapping the droplet-substrate contact, enabling self-peeling facilitated by thermal-mechanical stress relaxation. We observe a strong adhesion region in the center of the frozen droplet, which determines the adhesion strength, and develop a regime map to delineate the dependence of adhesion/peeling on droplet inertia, substrate supercooling, and surface wettability. Our work demonstrates key mechanisms governing ice-substrate adhesion during impact icing and presents an approach to passive self-deicing. • Clarification of the relationship among frost growth, peeling, cracking, and adhesion • Characterization of heterogeneous adhesion of droplet impact icing to substrates • Development of a regime map for self-peeling and ultra-low adhesion (0–50 kPa) • Demonstration of passive self-deicing for single and multiple impacting droplets A droplet impacting on a cold surface usually strongly sticks to the substrate during solidification. Jin et al. quantify the ultra-low ice-substrate adhesion and achieve spontaneous deicing on droplet impact freezing at high-surface supercoolings (>30°C).