Printable polymer nanocomposites for scalable and architected radiative cooling

Space cooling and lighting together consume 25% of global electricity, yet existing daytime radiative coolers are mostly limited to porous planar coatings that block visible light and lack durability. Here, we introduce rheology-optics coupling as a design principle that links polymer viscoelasticity to particle dispersion and optical scattering. Guided by this principle, we develop printable polydimethylsiloxane-zirconium oxide composites that achieve solar reflectance ( ~ 97.3%) and mid-infrared emissivity ( ~ 96.9%) comparable to the best reported values, despite a low filler loading of only ~4.5 vol.%. These scalable coatings provide up to 7.4 ^oC sub-ambient cooling and cut electricity use by 37% versus commercial paint in pilot-scale testing, while withstanding mechanical, thermal, and environmental stresses. Beyond planar coatings, the rheology-tunable polydimethylsiloxane-zirconium oxide ink enables direct ink writing of daylight-regulating architectures that deliver sub-ambient radiative cooling while admitting diffuse daylight for illumination, reducing both cooling and lighting demand. This work provides a practical and versatile platform for radiative cooling.