3D-arched fibrous sponge for high-performance thermal insulation

Frequent cold climates around the world place substantial burdens on public health, but most thermal protective materials still suffer from lightweight and insulation trade-off, weak mechanical elasticity, and moderate thermal insulation performance. Here, we report 3D-arched fibrous sponges (3D-AFSs) fabricated by moisture-assisted electrospinning of PAN/PEG/urea system followed by oxidative stabilization. Moisture-induced phase separation generates curly nanofibers that interlock and adhere to form a multilayer arched networks with ultralow bulk density (∼7 mg cm−3), high porosity (∼99.3%), and moderate water repellency (water contact angle ≈ 108°). Varying the urea content tunes jet hydration and conductivity, thereby controls fiber diameter, entanglement, and pore structure. The optimal 3D-AFS exhibits a minimum thermal conductivity of 0.019 W m−1 K−1, and on a simulated skin platform it yields a higher steady skin temperature than electrospun membranes, polyester fabric, and down. 3D numerical simulations and structural mechanism analysis attribute the thermal insulation to trapped quiescent air, highly tortuous solid pathways, and repeated solid-air interfaces within the arched nanofibrous layers. The 3D-AFSs also exhibit robust mechanics, maintaining shape after 200 compression cycles. These results demonstrate a scalable route to compressible, ultralight fibrous sponges that provide effective heat-flux suppression for wearable and personal thermal protection.