Engineers in Canada have built a chin strap that harnesses energy from chewing and turns it into electricity.
They say the device could one day take the place of batteries in hearing aids, earpieces and other small gadgets.
Made from a "smart" material that becomes electrically charged when stretched, the prototype needs to be made 20 times more efficient in order to generate useful amounts of power.
The researchers claim they can achieve this by adding layers of the material.
Their work appears in the Institute of Physics journal Smart Materials and Structures.