Researchers have created thin, flexible electronic devices that efficiently harvest the mechanical energy from natural motions of the human body. In addition to advances in materials processing to enable fabrication of these thin film devices, accurate analytical models were developed to predict electrical output of mechanical energy harvesting devices as a function of key design parameters and materials properties.

These novel devices could have multiple applications including meeting the power requirements for biomedical electronic implants and wearable health/fitness sensors.

Using key advances in materials processing and device assembly, researchers working at the University of Illinois at Urbana-Champaign, along with partner organizations, investigated mechanical energy harvesting from body motion with printable, flexible electronic devices. The devices in the study were made from a piezoelectric ceramic material, lead zirconate titanate (PZT), which generates electricity when mechanically deformed. Using designs and materials processing methods developed with DOE support, thin films of PZT were integrated onto flexible plastic (polyimide) substrates along with electronic circuitry and millimeter-scale batteries to produce devices capable of generating and storing electrical energy. When implanted on a moving surface such as a heart muscle, the device produced sufficient power for possible use with biomedical devices such as cardiac pacemakers and biometric sensors.

The research team also performed theoretical modeling to establish the design rules and predictive capability to correlate the multilayer designs with performance efficiency. In addition to furthering the understanding of the relevant energy conversion phenomena and enabling a qualitative model for predicting conversion efficiencies in these mechanical-to-electrical energy conversion devices, tests in the laboratory environment and in live animals also showed that the flexible PZT devices have promising mechanical durability as well as stability in the biological environment.

Department of Energy, Office of Science, Basic Energy Sciences. Mechanics modeling was supported by the Institute for Sustainability and Energy at Northwestern University. Animal testing was supported and performed by the Arizona Animal Care Facility, including support from the National Institute of Biomedical Imaging and Bioengineering.