Magnetic coupling between folded cantilevers for high-efficiency broadband energy harvesting

• A high-efficiency piezoelectric energy harvester based on a non-contact coupling technique is proposed.
• This design can take advantage of frequency detuning technique and multi-cantilevers to enhance the power generation.
• Broad bandwidth and improved output are achieved by non-contact magnetic coupling technique.
• Folded cantilevers are designed to improve the power generation and space efficiency.

In this paper, we proposed and characterized a high-efficiency piezoelectric energy harvester based on a non-contact coupling technique. The proposed design takes advantage of a frequency detuning technique and multi-cantilevers to enhance its power generation efficiency at ambient excitation. The energy harvester consists of two folded piezoelectric cantilevers with different resonance frequencies. A piezoelectric cantilever with a low resonance frequency (L-part) is coupled with another piezoelectric cantilever with a high resonance frequency (H-part) by a non-contact magnetic force. The output characteristic of each piezoelectric cantilever is improved using the magnetic coupling technique and a broad bandwidth is also realized under environmental vibrations. A feasibility of the fabricated energy harvester is experimentally confirmed to demonstrate the power generation capability in practical applications. With a load resistance of 50 kΩ, a maximum output power of 20 μW and an average power of 7.1 μW are achieved with the energy harvester, thus making it a suitable power supply for sensor nodes in wireless sensor network applications.