Ionic thermoelectric fibers woven into fabrics for human body heat harvesting

Ionic thermoelectric (i-TE) fibers are promising candidates for wearable low-grade heat harvesting by integrating ionic thermoelectric conversion with textile architectures. However, developing fiber-shaped i-TE materials that simultaneously achieve efficient ionic thermoelectric conversion, mechanical robustness, and textile compatibility remains challenging. Here, we construct a bacterial cellulose (BC)-based ionic thermoelectric fiber by incorporating 1-ethyl-3-methylimidazolium chloride (EMIM: Cl) into a three-dimensional cellulose porous network. The interconnected BC framework serves as both a mechanically stable fibrous scaffold and an ion-conducting matrix, enabling effective ionic transport while preserving fiber integrity. The optimized fibers exhibit an ionic thermopower of 13.05 mV K - ¹ and an ionic conductivity of 91.86 mS cm - ¹, together with a tensile strength of 3.9 MPa and an elongation strain of 115%. Moreover, the fibers maintain stable ionic thermoelectric performance over a broad temperature range from − 20 to 60 °C. By weaving these fibers into textile structures, an ionic thermoelectric fabric is fabricated to harvest human body heat under ambient conditions, generating a stable voltage output of ~ 0.1 V during on-body operation. This work establishes a fiber-based strategy for integrating ionic thermoelectric materials with textile architectures and advances the development of wearable thermal energy harvesting systems.