Ultra-flexible transparent temperature sensor with laser-direct writing of silver nanowire electrodes

Temperature monitoring of human skin to ensure the health has been a hotspot in present. In this work, an ultra-flexible transparent temperature sensor has been fabricated by embedding laser-direct writing of Ag nanowires (NWs) into a thin poly(vinylidene fluoride) (PVDF) film. The prepared Ag NWs/PVDF temperature sensors exhibit desirable overall resistance and acceptable sensitivity toward temperature variations, as well as distinct linearity in the temperature range from 30 ℃ to 120 ℃ and acceptable TCR values (0.00361/°C–0.00383/°C). Particularly, the obtained sensors achieve a high temperature resolution of 0.2 °C and high optical transmittance of 91.2 %. Moreover, the sensitivity of the sensors remains unchanged after 200 temperature measurement cycles from 30 ℃ to 80 ℃, demonstrating excellent reliability. In addition, the resistance of sensors is unchanged after 4000 bending cycles at a curvature radius of 3 mm, indicating the excellent mechanical flexibility. The ultra-thin thickness (5 μm) allows the Ag NWs/PVDF temperature sensors to intimately attached to human skin, guarantying the accuracy the measurement. As a proof of concept, the use of the Ag NWs/PVDF temperature sensor as a wearable thermometer is successfully demonstrated, which provides rapid response speed (<10 s) and sensing capabilities.