Michael McAlpine has developed a flexible material that produces record amounts of energy when subjected to mechanical pressure. It could turn the action of a patient’s lungs into enough energy to power an implanted medical device; forces produced by walking around could be sufficient to drive portable electronics.
In 2008, as a new assistant professor at Princeton, McAlpine started thinking about pacemakers: was there a way to harvest power from the lungs as people inhaled and exhaled, so that the batteries wouldn’t need to be surgically replaced every few years? Drawing on previous experience in making nanowire electronics and sensors on sheets of plastic, McAlpine began experimenting with PZT, a well-known material that is piezoelectric–able to convert physical stress into electricity. To make a flexible device, he deposits the PZT onto a hard substrate before carving the material into tiny ribbons. Then he uses chemicals to release the ribbons of PZT from the substrate and transfers them to a piece of silicone. A second piece of silicone seals the PZT in, creating a pliable, biocompatible material that’s four times as efficient as previous flexible piezoelectrics. So far McAlpine has made only small pieces of the material, but he is now scaling up the process to make larger wafers suitable for use in implanted electronics. –Katherine Bourzac