All-fibrous sandwich-structured humidity actuators enabling multimodal adaptive thermal comfort management

The human body's thermoregulation is intrinsically linked to thermal-moisture transfer. Wearable textile-based humidity actuators that adapt to human body microenvironments represent a promising approach for dynamic personal thermal management, an area that remains underexplored. Here, we present an all-fibrous sandwich-structured humidity actuator with multimodal thermal management capabilities. This actuator consists of uniaxially aligned hydrophilic polyvinyl al co hol nanofibers, hydrophobic poly(vinylidene fluoride-co-hexafluoropropylene) nanofibers, and silver nanowire (AgNW) layers. The asymmetric hygroscopicity and aligned nanofibers enable regular and large bending deformation that reversibly responds to humidity changes. Significantly, a warming mode maintaining 31.2 °C is operated when the actuator remains in a closed flat state under dry, cold conditions, with the low-emissivity AgNWs and all-fibrous architecture effectively suppressing heat dissipation; while skin perspiration-triggered opening under hot conditions activates a cooling mode maintaining 28.7 °C, permitting direct thermal convection, radiation, and moisture evaporation. Additionally, the electrically conductive AgNWs introduce an active heating mode for extremely cold conditions, enabling the actuator to readily achieve 37 °C at just 0.3 V. Wearable experiments demonstrate the actuator's practical applicability and effective comfort management. This all-fibrous, multi-dynamic humidity actuator provides a viable pathway toward energy-efficient smart textiles for personal thermal management across various environments.