Researchers from the University of Wisconsin-Madison, United States, have demonstrated a material that could be used to capture energy from respiration. The device, which uses a plastic microbelt made from polyvinylidene fluoride (PVDF), vibrates when passed by low-speed airflow such as human respiration. The resulting piezoelectric effect creates sufficient electrical energy to operate small electronic devices. According to Xudong Wang, a professor of materials science and engineering, “Basically, we are harvesting mechanical energy from biological systems. The airflow of normal human respiration is typically below about two meters per second. We calculated that if we could make this material thin enough, small vibrations could produce a microwatt of electrical energy that could be useful for sensors or other devices implanted in the face.” Wang and his team used an ion-etching process to thin the PVDF while preserving its piezoelectric properties. Their findings were published in the journal Energy and Environmental Science.

http://www.engr.wisc.edu/news/archive/2011/Oct11.html