Weavable ion–electron hybrid gel fibers with adjustable thermopower and high output voltage for wearable energy harvesting

Abstract

Wearable devices are evolving towards self-powered and flexible directions. Ionic thermoelectric generators (i-TEGs) with high thermopower are expected to become an eco-efficient solution. However, their practical deployment faces constraints, including restricted serial scalability and the lack of mechanically flexible carrier-cooperative transport units. Here, we develop a thermoelectric (TE) hydrogel fiber with bidirectional ion selectivity, achieving widely tunable thermopower ranging from −7.9 to +5.9 mV K⁻¹. The system features ion-transport channels constructed with abundant hydroxyl and sulfonic acid groups, and incorporates well-dispersed electron transport media to ensure high conductivity (σ) and enhanced ion selectivity. This innovative design enables modulation of p/n characteristics simply by introducing different ion sources, without additional modifications. By weaving 24 pairs of p/n-type i-TE fibers, we successfully fabricated a TE textile capable of generating 4.9 V output voltage on the body surface, which exceeds the highest output voltage of 1.3 V reported for fiber-based TEGs. Moreover, through coating a hydrophobic Ecoflex layer, we realized low humidity-resistant i-TE operation without performance degradation and achieved prolonged output stability. The fabricated TE textile maintained nearly 100% voltage retention after 30 days of ambient exposure. This scalable manufacturing of i-TE fibers provides new inspiration for wearable low-grade energy harvesting technologies.