A Paintable Bioinspired Stratified Skin Resolving the Cooling-Electricity Trade-Off for All-Weather Building Retrofits.

Abstract

Passive daytime radiative cooling (PDRC) can mitigate heat stress by dissipating heat into cold outer space, yet its benefit is suppressed by rainfall and by overcooling at higher latitudes. To offset these limitations, globally distributed rainfall can be harnessed for complementary electricity generation via a droplet electricity generator (DEG). However, integrating DEG with PDRC while preserving both cooling and electrical performance remains challenging. Inspired by Tillandsia trichomes, we report a paintable bifunctional skin that resolves this trade-off through stratified organization and functional reuse. A fluorinated top layer enables repeatable droplet electrification and self-cleaning while preserving strong mid-infrared emission, whereas nanoparticle-based layers simultaneously provide broadband solar scattering and dielectric charge storage. Guided by Monte Carlo simulations, this skin exhibits 96.2% solar reflectance and 96.5% thermal emissivity, delivers a peak net cooling power of 104 W m^-2, and sustains outdoor sub-ambient cooling of up to 9.5°C for more than six months. During rainfall, it reaches a peak electrical power density of 357 W m^-2. Global modeling across 1803 cities predicts a 33.9% expansion in the latitude span of net-positive annual benefit relative to standalone PDRC, offering a scalable route toward all-weather, latitude-robust building retrofits.