One energy-harvesting strategy involves converting energy from vibrations, pressure, and other mechanical stresses to electrical energy. This approach, producing what is known as piezoelectricity, is often used in loudspeakers and microphones.
A commonly used piezoelectric material is lead zirconate titanate, whose lead content raises concerns that it might prove too toxic for use with humans. “But for lead to decompose from the structures, they would have to be heated to temperatures higher than 700 degrees Celsius,” Dagdeviren says. “You’ll never reach such temperatures in the body.”
To take advantage of piezoelectricity, Dagdeviren and her colleagues have developed flat devices that can be stuck onto organs and muscles such as the heart, lungs, and diaphragm. These devices are “mechanically invisible” in that their mechanical properties are similar to whatever they are laminated onto, so they don’t hinder those tissues when they move.
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