Highly robust and sensitive dual-network freeze-resistant organic hydrogel thermocells

Thermocells (TECs) are eco-friendly and ideal power-generation devices that sustainably convert waste heat into electricity to power wearable electronics. However, their poor mechanical properties, limited operating temperature, and low sensitivity limit their practical application. Hence, K_3/4Fe(CN)₆ and NaCl thermoelectric materials were introduced into a bacterial cellulose-reinforced polyacrylic acid double-network structure and permeated into a glycerol (Gly)/water binary solvent to prepare an organic thermoelectric hydrogel. The resulting hydrogel had a tensile strength of approximately 0.9 MPa and a stretched length of approximately 410 %; moreover, it worked stably even in the stretched/twisted state. Owing to the introduction of Gly and NaCl, the as-prepared hydrogel exhibited excellent freezing tolerance (- 22 °C). In addition, the TEC also demonstrated excellent sensitivity (~13 s). Good environmental stability and high sensitivity make this hydrogel TEC a promising candidate for thermoelectric power-generation/temperature-monitoring systems.