Impact-Tolerant Radiative Cooling Enabled by Bioinspired Multiscale Glass Composite Coatings

Passive radiative cooling coatings are commonly designed for high reflectance under undamaged conditions, whereas protective surfaces must retain their optical function during impact. Reconciling mechanical and optical properties in a single material has been a challenge. The glass sponge (Euplectella sp.) maintains damage tolerance with desirable optical properties by laminated nanocomposite designs. Inspiring from this hierarchical structure, a rapidly photocurable polyurethane acrylate/Glass (PUA/Glass) multilayer composite coating is developed to confine impact damage while preserving radiative cooling performance. Alternating compliant PUA interlayers deflect and arrest cracks, whereas hollow glass microspheres (HGMs) and TiO₂/Al₂O₃ nanoparticles in glass layers redistribute load across multiple scales. HGM crushing, shell fragmentation, and local particle-matrix debonding dissipate energy yet retain or reconstruct air/glass/polymer interfaces; by contrast, connected macroscopic cracks disrupt the reflective layer. The coating combines solar reflectance above 92% with atmospheric-window emittance above 95% and remains, on average, 10.42°C below ambient during daytime outdoor testing. After a 20 J impact, localized hierarchical pores preserve reflectance and local cooling, while repeated 1 J impacts reveal a transition from optically tolerable microscale damage to reflectance-degrading macrocracks. These results provide a route toward impact-tolerant radiative-cooling surfaces for protective components.