Highly sensitive flexible strain sensor based on the two-dimensional semiconductor tellurium with a negative gauge factor

Research on flexible strain sensors has advanced rapidly in recent years, with particular attention being devoted to two-dimensional (2D) semiconductor materials owing to their exceptional mechanical and electrical properties that are conducive to sophisticated sensing performance. However, resistive strain sensors based on 2D semiconductor materials typically exhibit positive gauge factors (GF), while materials for strain sensors with a negative GF remain elusive. We have identified a trend of reduction in the band gap of the emerging 2D semiconductor material tellurium (Te) under strain in simulations reported in past research, and have observed a negative GF in the Te-based strain sensor. In this study, we combined Te with a flexible polyethylene terephthalate (PET) substrate to manufacture a flexible strain sensor with a significantly negative GF. The results of tests revealed that the Te-based strain sensor achieved an impressive maximum sensitivity of -139.7 within a small range of bending-induced strain (< 1%). Furthermore, it exhibited excellent linearity and good cyclic stability, and was successfully applied to monitor limb movements. The work here verifies the significant potential for the use of Te-based strain sensors in next-generation flexible electronics.