Multi-Functional and Stretchable Thermoelectric Bi₂Te₃ Fabric for Strain, Pressure, and Temperature-Sensing

Fiber-based electronics are essential components for human-friendly wearable devices due to their flexibility, stretchability, and wearing comfort. Many thermoelectric (TE) fabrics are investigated with diverse materials and manufacturing methods to meet these potential demands. Despite such advancements, applying inorganic TE materials to stretchable platforms remains challenging, constraining their broad adoption in wearable electronics. Herein, a multi-functional and stretchable bismuth telluride (Bi₂Te₃) TE fabric is fabricated by in situ reduction to optimize the formation of Bi₂Te₃ nanoparticles (NPs) inside and outside of cotton fabric. Due to the high durability of Bi₂Te₃ NP networks, the Bi₂Te₃ TE fabric exhibits excellent electrical reliability under 10,000 cycles of both stretching and compression. Interestingly, intrinsic negative piezoresistance of Bi₂Te₃ NPs under lateral strain is found, which is caused by the band gap change. Furthermore, the TE unit achieves a power factor of 25.77 µWm⁻¹K⁻² with electrical conductivity of 36.7 Scm⁻¹ and a Seebeck coefficient of −83.79 µVK⁻¹ at room temperature. The Bi₂Te₃ TE fabric is applied to a system that can detect both normal pressure and temperature difference. Balance weight and a finger put on top of the 3 × 3 Bi₂Te₃ fabric assembly are differentiated through the sensing system in real time.