Thickness‐Programmable Nanoporous Metafabric for On‐Demand Thermoregulation

ABSTRACT Maintaining stable warmth across volatile cold environments requires materials capable of adjusting heat retention according to varying thermal demands. However, current thermal regulation materials focus on switching between insulating and cooling modes, unable to offer reliable warmth during transitions. Here, we report an on‐demand regulable thermal system constructed via a coupled insulator–actuator architecture, integrating axially aligned nanoporous fibers with shape‐memory filaments. The tailored structure of fibers is designed by the synergistic combination of hydrogen‐bond dissociation and confinement‐induced crystallization, which constructs a channel‐like, axially aligned nanoporous fiber network with an ultrahigh porosity of 99.89% and an ultralight density of 1.59 mg cm −3 , while the integrated shape‐memory filaments serve as structural actuators to compress and release the fibrous network. The as‐prepared metafabric enables nearly 5‐fold thickness modulation while delivering thermal insulation that matches varying thermal demands, stabilizing the human thermal comfort zone across a wide temperature range from –6.1 to 20.8 °C. Moreover, the metafabric outperforms representative commercial fabrics (e.g., down, wool, and acrylic) at comparable thicknesses, promising great potential for developing efficient warm clothing. This work presents a scalable strategy for high‐performance fabrics that deliver reliable warmth and establishes design principles for personal microclimate control in thermal management.