Do you remember elementary school science lessons where you’d rub a balloon on your head and your hair would stand up? Or rub a plastic comb with a piece of wool and it would attract little slips of paper? Or maybe you’ve received a painful shock in the winter when you touch a light switch after walking across a carpet? We tend to call this “static electricity,” but in scientific circles it is often referred to as a “triboelectric” effect. When two surfaces rub against each other, if they have the right characteristics, electrons from one side will “stick” to the other and build up. This creates an electrical charge — like a capacitor — that can be harnessed to do useful work (other than giving you a shock!)
Researchers at Georgia Tech have created a device that uses the triboelectric effect to harvest energy to power an implanted sensor system. As a result, the device never needs batteries and never needs to be recharged. They created a sandwich of plastic films with gold and aluminum layers as electrodes. All of the materials used are biocompatible, suitable for use in implants. The device is roughly 1.1 by .8 inches, and was implanted on the heart muscle of a pig. The system was able to produce up to 10 volts of electricity at 4 microamps, which is more than enough to be useful. Furthermore, the power is generated by the heart motion, so the power output itself becomes a data source about the heart’s operation. It was also possible to detect motion related to breathing, based on the changes in the power output.
After two weeks, the implant showed no signs of wear or damage to the encapsulation layers, and no signs of rejection by the host’s body. The researchers are confident that the design could be used for long-term implants, and used to power sensor systems that could provide real-time wireless monitoring of vital biometric measures.