To build the harvester transducer, the researchers used a combination of thin-film energy-conversion materials with a minimally invasive mechanical approach in a modified pacemaker design. They harnessed the kinetic energy of the lead wire that’s attached to a beating heart, and then converted it into electricity to continually charge the batteries – see figure 1. The power-generating material, a specialized polymer piezoelectric film called polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), is designed with porous structures and then built into either an array of small beams or a flexible cantilever.
The team created a dual-cantilever peizoelectric structure that wraps around the pacemaker’s lead, with the structure’s two free ends available for connection and subsequent energy collection – see figure 2.
The maximum output was 0.5V at 43nA at 1Hz, a little over 20nW. By adding a small proof mass of 31.6 mg on the tip of the dual-cantilever tip, the power output increased by a little over 80% since the added mass enabled a larger bending curvature, resulting in higher electrical output from the harvester.