Integrative square-grid triboelectric nanogenerator as a vibrational energy harvester and impulsive force sensor

A square-grid triboelectric nanogenerator (SG-TENG) is demonstrated for harvesting vibrational energy and sensing impulsive forces. Each square of the three-dimensional (3D)-printed square grid is filled with an aluminum (Al) ball. The grid structure allows the SG-TENG to harvest vibrational energy over a broad bandwidth and operate at different vibrational angles. The most striking feature of the SG-TENG is its ability of being scaled and integrated. After connecting two SG-TENGs in parallel, the open-circuit voltage and short-circuit current are significantly increased over the full vibrational frequency range. Being integrated with a table tennis racket, the SG-TENG can harvest the vibrational energy from hitting a ping pong ball using the racket, where a direct hit by the racket generates an average output voltage of 10.9 ± 0.6 V and an average output current of 0.09 ± 0.02 μA. Moreover, the SG-TENG integrated into a focus mitt can be used in various combat sports, such as boxing and taekwondo, to monitor the frequency and magnitude of the punches or kicks from boxers and other practitioners. The collected data allow athletes to monitor their status and improve their performance skills. This work demonstrates the enormous potential of the SG-TENG in energy harvesting and sensing applications.