Development of microelectromechanical systems electromagnetic vibration energy scavengers with a nonlinear electroplated nickel spring

Three electromagnetic vibration energy scavengers with electroplated Ni springs have been designed, fabricated and characterised. Prototype I consists of a coil, an Ni spring on a silicon frame and a permanent magnet. Prototypes II and III are with a sandwich structure and consist of two coils, an Ni spring and a permanent magnet. There are air channels in the silicon frame in prototype III. These prototypes were fabricated using microelectromechanical systems microfabricating techniques. The experimental results show the electroplated Ni spring is a nonlinear and hardened one, so the spring-magnet system has a different resonant frequency under different excited vibration. The tested results show that prototype III has the highest output voltage and output power. The maximal load voltage is 157.5-mV and the maximal load power is 21.7--W for prototype III when it is excited by vibration with 280.9-Hz frequency and 0.8-g acceleration.