Ultra-low frequency piezomems energy harvester for a leadless pacemaker

The next generation of leadless pacemakers will require an integrated energy harvester in order to develop a self-sustaining implantable device. An ultra-low frequency energy harvester will allow the device to operate at the resonant frequency of the impulse from the heart (20-30 Hz). This paper reports on the comparison of two piezoelectric MEMS energy harvesters based on an AlN piezoelectric layer with resonant frequencies of 28.5 and 678 Hz. The ultra-low frequency MEMS device operates at the resonant frequency of the heart impulse, and the other device operates off-resonance at higher acceleration. The results demonstrate that peak power densities of ~ 1 and 0.135 mW cm^-3 were experimentally measured for the high and low frequency device respectively. The devices were designed to enhance power by maximizing displacement of the cantilever within a leadless pacemaker capsule.