Synergistic ion–electron coupling in thermoelectric hydrogels for self-powered sensing

Abstract

Hydrogel-based thermoelectric (TE) materials are attractive for their flexibility and large Seebeck coefficient (S), yet achieving high and stable output remains challenging. Here, a synergistic ion–electron coupling strategy is proposed by integrating ionic and electronic conduction pathways within a single hydrogel system. A high-performance hybrid TE hydrogel is fabricated by incorporating p-type Bi_0.3Sb_1.7Te₃ (BST) particles and a KOH electrolyte into a κ-carrageenan/gelatin matrix. The introduction of BST establishes an electronic contribution, increasing S from ∼0.18 mV K⁻¹ to ∼1.35 mV K⁻¹, while subsequent addition of KOH further enhances S to ∼2.98 mV K⁻¹, surpassing that of individual components. Mechanistic studies reveal that BST not only provides electronic thermopower but also facilitates ionic thermal migration under a temperature gradient. The resulting hydrogel exhibits robust TE performance, long-term stability, and piezoresistive sensitivity, enabling its application as a self-powered temperature sensor for water temperature and respiratory monitoring. This work offers a novel design paradigm for high-performance, multifunctional hydrogel-based TE materials.