Strain/deformation-insensitive wearable rubber composite for temperature monitoring based on the photothermal and thermoelectric conversion

Wearable sensor has been developed for the temperature monitoring. However, the motion of human muscles is a nonnegligible background interference which affects the stable and accurate transmission of output electrical signals for temperature sensor. Rubber, as an elastic and flexible material, has been widely applied all over the world due to the easy processing and low cost, which is potential to serve as a matrix of intelligent sensing material. But it is difficult to construct a conductive pathway in the solid rubber by the filling conductive media. Herein, we report a temperature-responsive rubber composite with strain-insensitive resistance based on a synergism structure constructed by Ag nanoflakes (AgNFs) and Ag nanoparticles (AgNPs) after the rubber latex film forming. The AgNFs are easier to overlap and form stable conductive paths to endow the material with a stable conductivity within a small strain (ε < 9 %) via the slide of AgNFs, showing a maximal value of (R-R0)/R0 at only 0.001. In this case, the AgNPs with slight agglomeration are filled into the space of AgNFs to construct conductive paths. Under the larger strain (9 % <ε < 143 %), the agglomerated AgNPs are pull-apart and migrated to form single AgNP, maintaining the conductive path with a high quality factor of 9.09. The resultant material owns a high photothermal conversion efficiency of 78.6 %. Based on the satisfactory conversion of "light-heat-electricity" and "heat-electricity", material is used as a wearable temperature sensor, and it only takes 0.5 s to sensitively sense the changes in body temperature.