Highly flexible TPU/SWCNTs composite-based temperature sensors with linear negative temperature coefficient effect and photo-thermal effect

Conductive polymer composites (CPCs) based flexible temperature sensors are highly desirable for electronic skins (e-skins) due to their flexibility, good processability, and lightweight. However, it is still a challenge to fabricate a flexible CPC-based temperature sensor with linear negative temperature coefficient (NTC) effect because CPCs normally exhibit non-monotonic dependence on temperature. Herein, we prepare the flexible thermoplastic polyurethane (TPU)/single-walled carbon nanotubes (SWCNTs) composites by the facile method of solution blending and thermal annealing. The as-prepared composites exhibit a monotonic and linear NTC effect in the temperature range of 30–100 °C, which can be designed into highly flexible and sensitive temperature sensors. The as-prepared sensor can achieve respiratory monitoring, cellphone charging time monitoring and non-contact temperature detection, attributing to its high accuracy (0.1 °C), excellent reproducibility and high reliability (Deformation and heating rate have no effect on the thermal response.). Moreover, the sensors also show resistance response to infrared radiation owing to the excellent photo-thermal effect of SWCNTs. The integrated linear NTC effect and photo-thermal effect endow the sensors with tremendous potentials in e-skins and wearable electronics.