Boosting the energy conversion efficiency of a combined triboelectric nanogenerator-capacitor

With the growing popularity of various internet of things sensors and portable devices, such as smartphones and smartwatches, the demand for power generation sources for driving such electronic devices is becoming increasingly important and challenging. If we rely on batteries to drive all of the sensors related to Internet of things, most of the IoT would be impossible. Here, we report the exciting possibilities for the use of triboelectric nanogenerators (TENGs) toward real-time self-powered electronics, such as a smartphone-to-smartwatch telecommunication over Bluetooth via the capacitors charged by the TENGs, a self-powered pulse sensor, and a realtime self-powered calculator. To achieve the high-output power of the TENGs, we focused on multiple strategic points such as device structures, contacted materials, and mechanical systems, as well as circuit design methods of enhancing the charging efficiency to the energy storage device. The novel integration scheme of TENGs made it generate areal output power of approximately 3 mW/cm(2) under a low frequency of 3 Hz through a gear-cam system. Based on these results, fast-chargeable portable power-supplying systems for the continuous self-powered electronic systems were successfully developed.