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. Phase change materials are promising for thermal regulating materials, though it is challenging to embed them into fibres. Here the authors use a speed matching strategy to fabricate core-shell phase changing fibres for thermal regulating textiles.