Photo-responsive liquid–solid triboelectric nanogenerator by photothermal effect

We present the report of a light-driven triboelectric switching property in liquid–solid triboelectric nanogenerator (L–S TENG). The developed photoresponsive L–S TENG (PR-TENG) employs a photothermal effect and phase-change material to alter surface wettability via light irradiation. The phase of the surface changes depending on the presence or absence of light, resulting in variations in wettability and adhesion to water droplets. As the surface properties changed reversibly, PR-TENG produced an open-circuit voltage and a short-circuit current of ∼15 V and ∼60 μA in the OFF state and ∼24 V and ∼95 μA in the ON state, respectively. The electrical signal was enhanced by more than 50 % under light, and the triboelectric switching characteristics were described by the difference in the maximum spreading area of droplets (A_max), which determined the transferred charges. The switching characteristics of PR-TENG at various Weber numbers and inclination angles were also investigated; the results indicated a consistent relationship between A_max and electrical signals. Furthermore, a PR-TENG-based self-powered photodetection system is proposed to detect light irradiance and proximity. In this study, we introduce the concept of photoresponsive triboelectric switching and demonstrate the potential of L–S TENGs in self-powered external stimuli sensors.