Self-Powered fully stretchable temperature sensors from asymmetric composite thermoelectric materials

Thermoelectric (TE) materials have been extensively used in self-powered temperature sensing devices, especially flexible sensors that require low energy consumption. One of their important features is the flexibility that allows conformal contact with various subjects and tolerance to mechanical deformation. However, realizing both high TE conversion efficiency and excellent flexibility remains a significant challenge. Here, a general method was developed to produce stretchable high-performance TE composites and achieved asymmetric composite thermoelectric materials (ACTE) with high Seebeck coefficient (215 μV·K⁻¹ for n-type, 175 μV·K⁻¹ for p-type). The fully stretchable temperature sensors (FSTS) fabricated from ACTE exhibited good flexibility which could withstand 50 % uniaxial tensile strain and 30 % biaxial strain with low thicknesses (∼650 μm) that allowed for good contact on curved surfaces. The sensitivity of FSTS reached ∼145 μV·K⁻¹ with 18 n/p ACTE pairs and ∼37 μV·K⁻¹ with 2 pairs and could output stable signals regardless of flexural or tensile deformation. The FSTS was also fabricated into an array that could be worn as sensors or electronic skin with temperature sensing and mapping abilities. This work not only produced fully stretchable TE devices but also provided a general method for the fabrication of other high-performance stretchable composites and devices.