Bioinspired Segregated Networks Couple Phase‐Change Confinement With Ultrafast Sensing for Thermal Energy Storage

ABSTRACT Harvesting ambient renewable energy requires materials that can retain their function under coupled and often harsh environmental conditions. Flexible phase‐change materials (PCMs) are promising for wearable systems because they can integrate thermal regulation, physiological sensing and energy harvesting. Here, inspired by the hierarchical architecture of rice leaves, we report a phase‐change elastomer for ambient energy harvesting and ultrafast moisture sensing, fabricated via an in situ biomimetic assembly strategy. A continuous 3D segregated network of carboxymethyl chitosan coordinated with Cu 2+ ions spatially confines polyethylene glycol (PEG) within a poly(ethylene vinyl acetate) (EVA) matrix. This biomimetic network enables a toughness of 9.80 MJ m −3 and an elongation at break of 218%. Unlike conventional PEG composites that are prone to humidity‐induced instability, the elastomer exhibits enhanced moisture resistance and a reduced leakage rate of 1.46%. Continuous ionic pathways within the segregated network enable an ultrafast humidity response of 172 ms, whereas the Cu 2+ ‐containing network provides broad‐spectrum antibacterial activity. This work establishes a biomimetic strategy for designing multifunctional phase‐change elastomers for wearable energy harvesting and environmental sensing in complex operating conditions.