Design of Mems Based Piezoelectric Energy Harvester for Pacemaker

In this paper, a spiral-shaped piezoelectric cantilever structure is proposed to harvest the energy from the vibration of the heartbeat. The proposed cantilever structure is $14 \mu \mathrm{m}$ thin with the outer dimension of $5\ \mathbf{mm}\ \mathbf{x}\ 5\ \mathbf{mm}$ . The spiral structure reduces the stiffness of the cantilever beam which reduces the resonant frequency. A proof mass is introduced in the spiral structure to further reduce the resonant frequency of the cantilever beam. Due to biocompatibility nature, Zinc oxide (ZnO) has been used as the piezoelectric material for the design. The proposed structure has a resonant frequency of 45.8 Hz which is suitable for harvesting energy from the human heartbeat. The harvester generates peak output open circuit voltage of 3.2 V and peak output power of $\mathbf{3.5}\ \mu \mathbf{W}$ at the resonant frequency of 45.8 Hz for a sinusoidal acceleration of 1g.