Dynamic Brush Surface Inducing Mobile Crystallization for Sustainable Spray Cooling Using Saline

Spray cooling, which dissipates heat through droplet evaporation, is an efficient cooling method. Using seawater instead of freshwater in spraying is appealing given the intensifying global water crisis. However, seawater-based cooling suffers from salt accumulation on hot surfaces. To address this, we present a liquid-like polymer brush coating for heating surfaces. This coating with a dynamic nature regulates salt crystallization during saline evaporation, forming columnar structures beneath the crystals that facilitate salt grain detachment under gravity. As a proof-of-concept, we developed polydimethylsiloxane brush grafted aluminum alloy (PBGAA), which showed a stable temperature drop from 67.9 to 55.4 °C over 2 h of continuous spraying, compared to a temperature rise from 67.9 to 75.9 °C on the control surface (AA). Correspondingly, PBGAA exhibited minimal weight gain (0.015 g) versus a significant increase (1.242 g) on AA. This brush-grafting strategy holds great promise for using seawater in industrial cooling applications.