The rumbling you feel driving along a bridge may soon serve a purpose beyond just waking you up behind the wheel. Researchers at MIT have developed a tiny energy-harvester that is able to harness low-frequency vibrations like those made by a bridge or pipeline and converting them to electricity for wireless sensors.
Wireless sensors are used for all kinds of things, from monitoring factory machines and oil pipelines to keeping track of pollution. While the efficiency of their energy consumption has improved, the sensors' batteries still need to be changed occasionally. MIT's device, a microelectromechanical system (we prefer the term energy-harvester) makes electricity from the vibrations of foot traffic and other low-power energy sources from the environment, potentially removing the need for batteries completely.
The quarter-sized energy-harvester has improved on the designs of similar devices by taking inspiration from the bridges themselves. MIT's energy-harvester consists of a microchip with a bridge-like structure anchored at either end. On the bridge is a weight sitting on one layer of piezoelectric material (PZT), which naturally gathers electric charge when faced with mechanical stress. Other devices use a cantilever beam instead of a bridge to pick up vibrations, which is much less efficient. MIT's design picks up a wider range of vibrations and produces 100 times more energy than any other harvester available.
The next step for the project is to get the device to pick up lower-frequency vibrations and generate at least 100 microwatts of power, a target that would be able to power a whole network of wireless sensors.