Researchers have created a motion-powered, fireproof sensor that can track the movements of firefighters, steelworkers, miners, and others who work in high-risk environments where they cannot always be seen. The sensor alerts someone outside if the movement ceases.
The low-cost sensor is about the size of a button-cell watch battery and can easily be incorporated into the sole of a boot or under the arm of a jacket — wherever motion creates a pattern of constant contact and release to generate the power the sensor needs to operate.
The sensor uses triboelectric (friction-generated) charging, harvesting electricity from movement in much the same way that a person in socks picks up static electricity walking across a carpet. The key material — a new carbon aerogel nanocomposite — is fireproof and the device never needs charging from a power source.
Previously developed self-powered sensors have allowed similar tracking but their materials break down at high temperatures, rendering them useless. A self-powered sensor is necessary in extreme heat because most batteries also break down in high temperatures. The new technology was tested at temperatures up to 300 °C — the temperature at which most types of wood start to burn — without any loss of function.