Energy harvesting, which generates electricity from people walking, cars, and vibrations of machines, is attracting attention as a power source for sensors in the IoT society.Professor Tani's group has been working on the development of a flexible and lightweight friction generator made of rubber, charging film, and electrodes, which generates electricity from static electricity generated by friction, for several years.

　At the beginning of development, the amount of power generated during walking was as weak as 0.003 mW / step, but this time we succeeded in improving the amount of power generation by more than 100 times compared to the conventional product by devising the roughness of the rubber surface.When the amount of power generated by incorporating it into the insole of the shoe was evaluated, it was confirmed that it was possible to generate 1 mW (momentarily 0.6 mW) with one step of landing.With this amount of power generation, it is possible to turn on 10 or more LEDs and drive wireless circuits, and it can be expected to be applied to various places as an energy harvesting device.

　Since this friction generator has a simple structure and is based on rubber, it is flexible and low cost, and various applications can be considered.For example, if it is built into shoes, it will generate electricity each time it walks, and a beacon signal will be transmitted by a wireless circuit to notify the position, and by further increasing the amount of power generation, it will be possible to charge the battery of a smartphone or the like in combination with a power storage circuit.In the future, it aims to generate 0.1W / step by improving the structure.