As heat waves intensify, keeping people, packages and gadgets cool without extra energy is climbing the global tech wish-list. A Donghua–Jiangnan University team led by Prof. Chao Zhang and Prof. Tianxi Liu now unveils a single-step bicomponent blow-spinning route that delivers kilometre-scale rolls of an ultra-flexible, self-healing micro-fibre textile engineered with two built-in gradients—one in fibre diameter (2.0 → 0.3 µm) and the other in polymer chemistry (PVDF → PMMA). The dual-gradient architecture behaves like a Janus optical engine: the sun-facing side reflects 98.7 % of solar irradiance while beaming 95 % mid-IR radiation to outer space; the human-facing side absorbs a broad IR spectrum, pulling heat away from self-heated objects such as electronic housings or human skin. Outdoor tests show 7.8 °C sub-ambient cooling for neutral objects and 13.6 °C temperature drop for internally heated enclosures—outperforming commercial aluminium-coated shade cloth by more than 5 °C.
Why This Matters
- Real-World Ready: Roll-to-roll production reaches 80 cm width; mechanical strength (4 MPa) supports 5 kg loads and 100 bending cycles without delamination.
- Self-Healing on Site: A portable blow-spinning gun re-deposits gradient fibres across tears, restoring both 98 % reflectance and mechanical integrity in minutes.
- Weather Tough: Hydrophobic surface (137° contact angle) sheds dust; 240 h UV aging retains 97.9 % solar reflectance.
- Energy-Free Cooling: Modelling predicts 114.8 W m-2 daytime cooling power under 1000 W m-2 solar irradiation even at h = 9 W m-2 K-1 convection—competitive with active HVAC.
Innovative Design & Features
- Hierarchical Pores: Continuously varying fibre diameters generate Mie-scattering centres sized to the 0.3–2.5 µm solar window, shortening photon path length and deepening penetration depth control.
- Janus Spectral Selectivity: PVDF-rich outer layer emits selectively at 8–13 µm (γ = 1.68); PMMA-rich inner layer offers 90 % broadband IR absorption (γ = 1.04), enabling rapid heat exchange with enclosed heat sources.
- Thickness Optimised: FDTD and experiments converge on ~300 µm as the sweet spot—thick enough for multiple scattering yet thin enough to avoid uniformity-induced reflectance loss.
- Multi-City Validation: Field trials in Beijing (dry, –8.7 °C) and Hong Kong (humid 90 % RH, –5.6 °C) confirm consistent sub-ambient performance under disparate humidity loads.
Applications & Future Outlook
- Wearable Thermal Management: Lightweight (area density < 40 g m-2) and air-permeable for cooling vests, sportswear and military uniforms.
- Logistics & EVs: Wraparound shields for battery packs, food containers and 5G outdoor cabinets, cutting peak temperatures by 10–15 °C.
- Built Environment: Retrofit awnings, tents and truck tarpaulins; simulation shows GMFT-covered roofs can lower indoor cooling demand by 20 % in subtropical climates.
- Next Steps: Team is coupling the textile with phase-change layers and exploring recyclable PVDF/PMMA blends to close the materials loop while scaling nozzle counts for metre-per-minute throughput.
The gradient-textile paradigm shifts radiative cooling from static, single-emission surfaces to adaptive, healable fabrics that can be manufactured, deployed and repaired on demand—pointing toward a truly sustainable route to beat the heat anywhere under the Sun.
