Miniaturized piezoelectric energy harvester for battery-free portable electronics

This paper describes a miniaturized energy harvester based on the interaction of two permanent magnets placed on both ends of a folded cantilever made with piezoelectric thin films. A unique design of the folded cantilever structures is developed to efficiently collect ambient vibrational energy over a wide frequency bandwidth for the operation of battery-free electronic devices. The output performance of the two energy harvesters is observed to improve significantly through the use of the mutual coupling technique. The folded cantilever structure also demonstrates improved space efficiency compared with the conventional rectangular cantilever design. A wide frequency band and sufficient energy-harvesting ability were successfully achieved by the optimally manufactured device. The maximum output power of the miniaturized energy harvester was 41.6 mu W with an impedance of 0.3 M omega. Furthermore, a pedometer was powered completely by the energy harvester without the need for any battery and external power source, demonstrating the potential of the proposed design for self-powered electronics applications in a vibrational environment.