Twisted-Yarn Knitted Fabrics Enabling Humidity-Driven Infrared Regulation and Passive Thermal Cooling

To address the pressing demand for personal thermal management under extreme heat, we report a humidity-adaptive knitted fabric that integrates reversible structural actuation with synergistic infrared modulation via dual-layer nanocoating. Highly twisted cotton and cellulose triacetate yarns were employed and knitted in a stretchable architecture, enabling humidity-triggered geometric reconfiguration. Upon moisture uptake, yarn swelling and twist angle adjustment collectively induce reversible pore opening and increased fabric porosity, thereby regulating heat and mass transfer. The fabrics were treated with silica and silver nanoparticles to work together and boost their infrared transmittance and emissivity, thereby significantly improving their passive radiative cooling performance. The fabric’s infrared transmittance improved by 30%–35% under humidity stimulation, giving it substantial thermal radiation modulation capability (ΔT ≈ 5–12 °C). The high bacterial inhibition rate of both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) is due to the unique antimicrobial properties of silver nanoparticles, exceeding 99.99%. Following 5 cycles of intensive washing with distilled water and 50 cycles of stretching treatment, the retention rate of functionality exceeded 99%, highlighting outstanding mechanical durability. Integrating these high-performance properties can enhance the practical uses of this passive cooling fabric to address the increasing high-temperature environment.