Hybrid generator based on freestanding magnet as all-direction in-plane energy harvester and vibration sensor

Highlights: • The spring-mass system enables the device to harvest vibration energy along all in-plane directions. • The combination of two working mechanisms can enhance energy harvesting efficiency. • The device can work as a self-powered vibration sensor for distinguishing motion directions. Vibration is a widely existing mechanical phenomenon containing enormous energy that can be transformed into electricity without polluting the environment. However, most current mechanical energy harvesters only can scavenge energy from a specific direction, resulting in the waste of energy from other directions. Here, we propose a triboelectric-electromagnetic hybrid generator built on freestanding magnet (FMHG), which is able to harvest low-frequency vibration energy from arbitrary in-plane directions. Besides, it can detect vibration direction from periodical or pulse movement. Under the excitation of shaker, maximum power of 85.7 µW and 3.29 $m$W are obtained by one electrode pair of the TENG and EMG respectively, which can charge a capacitor of 20 µF to 7 V rapidly benefiting from the hybrid configuration. The hybrid generator can light up commercial LEDs driven by human running and bicycle braking, as well as distinguish leg movement in eight directions, proving its application potential in building up self-powered sensing systems such as alarms, environmental monitor and human-machine interface.