A flexible dual parameter sensor with hierarchical porous structure for fully decoupled pressure–temperature sensing

Flexible pressure–temperature dual parameter sensors that mimic the function of human skin show potential applications in wearable devices and intelligent robots. Simultaneous sensing of pressure and temperature has been realized by obtaining separated signals utilizing independent piezoresistive and thermoelectric sensing mechanisms, respectively. However, temperature variations induced resistance change poses a negative influence on the pressure sensing accuracy. In this study, a flexible pressure–temperature dual parameter sensor with hierarchical porous structure is presented. The conductivity is realized by inserting graphene into a multilayer structured thermoplastic polyurethane/carbon nanofibers (TPU/CNFs) sponge. The hierarchical porous structured TPU/CNFs sponge with graphene coating endows the sensor with a high pressure sensitivity of 0.14 kPa⁻¹ (0–60 kPa) and a high temperature sensitivity of 30.8 μV/K. Moreover, in the dual parameter mode, the sensor demonstrates neglectable mutual interference between pressure and temperature signals due to lowered temperature-induced resistance change by surface coating of graphene. We show that the sensor can be integrated inside the mask to monitor real-time human respiration. It is also used as the sensing part of a robot arm for high temperature alarm and automatic evacuation. The excellent performance of the sensor ensures its promising application in healthcare monitoring, prosthesis and human–machine interaction (HMI) systems.