Scalable phase-change fibres with record thermo-mechanical properties for cooling textiles.

Efficient thermal regulation in clothing is critical for comfort, safety, and energy conservation, yet achieving it without active cooling remains a major challenge. Phase-change materials (PCMs), which store and release heat during solid-liquid transitions, offer a promising route toward passive and durable temperature control in everyday apparel. Embedding liquid-state PCMs into fibres (PCFs) is inherently challenging due to the instability of micro-scale liquid cores and the inability of conventional microfluidics to sustain continuous injection beyond centimetre lengths, limiting scalable fibre production. We overcome these barriers through a size-reduction and speed-matching strategy during thermal and cold fibre drawing, yielding uniform 35 m-long, 200 µm-thin core-shell PCFs. The fibres exhibit low supercooling (4.2 ± 0.3 °C), high latent enthalpy (122.6 ± 1.5 J g⁻¹), and record-level mechanical performance (32.1 ± 0.8 MPa strength, 671 ± 10.2% elongation). Fabrics incorporating 50% PCFs achieve sustained temperature reductions of 3-6 °C under realistic conditions, passively dissipating heat from sunlight and battery-generated hotspots while outperforming conventional cotton. These findings pave the way for scalable, high-performance textiles that provide passive thermal regulation, offering a practical strategy to reduce energy demand and mitigate environmental impact.