Thermochromic triboelectric nanogenerator enabling direct visualization of temperature change during operation

Triboelectric nanogenerator (TENG) depends on the effect of contact electrification to harvest mechanical energy. However, heat generation is unavoidable during the tribo-motions. Temperature increase may not only affect the output performance of TENG, but also bring potential harm to the operators. Hence, a thermochromic triboelectric nanogenerator (TC-TENG), which can directly visualize temperature changes, is designed based on a combination of thermochromic ionic liquid (TIL) and polyvinylidene fluoride (PVDF). This thermochromic polyvinylidene fluoride (TC-PVDF) film can change its color from white to light green at around 60 ℃, while it can also maintain good electrification performance for TENG. The triboelectric series of this TC-PVDF shifts to more positive position in comparison with common PVDF, which is possibly due to the contribution from TIL during the electrification. The TC-TENG with an effective contact area of 3 cm × 5 cm can provide a maximum output power density of 125 mW m −2 at a matching resistance of 330 MΩ and it shows excellent stability with various humidity and different air pressures. The proposed TC-TENG with self-alarming capability can further promote the study of intelligent TENG and fully automatic self-powered systems.