Flexible All-Inorganic Thermoelectric Yarns.

Achieving both formability and functionality in thermoelectric materials remains a significant challenge due to their inherent brittleness. Previous approaches, such as polymer infiltration, often compromise thermoelectric efficiency, underscoring the need for flexible, all-inorganic alternatives. This study demonstrates that the extreme brittleness of thermoelectric bismuth telluride (BiTe) bulk compounds can be overcome by harnessing the nanoscale flexibility of BiTe nanoribbons and twisting them into a yarn structure. The resulting BiTe yarn, with a Seebeck coefficient of -126.6 µV K, exhibits remarkable deformability, enduring extreme bending curvatures (down to 0.5 mm) and tensile strains of ≈5% through over 1000 cycles without significant resistance change. This breakthrough allows the yarn to be seamlessly integrated into various applications-wound around metallic pipes, embedded within life jackets, or woven into garments-demonstrating unprecedented adaptability and durability. Moreover, a simple 4-pair thermoelectric generator comprising BiTe yarns and metallic wires generates a maximum output voltage of 67.4 mV, substantiating the effectiveness of thermoelectric yarns in waste heat harvesting. These advances not only challenge the traditional limitations posed by the brittleness of thermoelectric materials but also open new avenues for their application in wearable and structural electronics.