Interpenetrating double-network thermoelectric hydrogels with enhanced mechanical stability, superior water retention, and high thermoelectric performance

Abstract Thermoelectric hydrogels (TEHs) have attracted increasing interest as soft materials for miniaturized thermoelectric devices. However, achieving multifunctionality with balanced thermoelectric efficiency, mechanical robustness, and water retention to ensure overall stability in wearable electronics and personal thermal management remains a major challenge. Herein, we report high-performance TEHs with an interpenetrating double-network structure of carboxymethyl cellulose and acrylamide (C/A), incorporating K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ], KCl, and LiCl (Fe/K/Li). The resulting C/A hydrogels exhibit excellent mechanical strength and remarkable hydration stability, retaining 85.1% water after 14 days at 25℃ and 65% relative humidity, and reaching 90% water absorption within 8 days. Benefiting from the synergistic effects of ionic thermodiffusion and thermoelectric effect contributions, the Fe/K/Li-C/A TEHs achieve a peak Seebeck coefficient of – 4.67‧mV‧K −1 , a maximum power density of 30.86 mW‧m −2 under a 40 K gradient, and an optimal thermoelectric figure of merit (ZT i ) of 0.557. Furthermore, a lightweight and portable device assembled from serially connected TEH units generates a voltage output of 114 mV under body heat. This study demonstrates a versatile TEH with integrated stability, toughness, and high thermoelectric performance, offering a promising strategy for practical energy harvesting in wearable and biomedical applications.