The group of researchers have developed a biofuel skin patch, which uses the lactic acid in a human's sweat to power an electrical device.
Joseph Wang, who was part of the team that worked on the patch, said: "We're now getting really impressive power levels. If you were out for a run, you would be able to power a mobile device."
The patch - which is only a few centimetres wide - can be stuck onto the skin and uses enzymes that work similar to the metals inside normal batteries. These enzymes can be powered using the lactic acid found in sweat.
In a summary post from the write up in the Energy & Environmental Science journal, they write: "This article describes the fabrication, characterization, and real-life application of a soft, stretchable electronic-skin-based biofuel cell (E-BFC) that exhibits an open circuit voltage of 0.5 V and a power density of nearly 1.2 mW cm−2 at 0.2 V, representing the highest power density recorded by a wearable biofuel cell to date.
"High power density is achieved via a unique combination of lithographically-patterned stretchable electronic framework together with screen-printed, densely-packed three-dimensional carbon-nanotube-based bioanode and cathode array arranged in a stretchable "island-bridge" configuration. The E-BFC maintains its performance even under repeated strains of 50%, and is stable for two days.
"When applied directly to the skin of human subjects, the E-BFC generates ∼1 mW during exercise. The E-BFC is able to power conventional electronic devices, such as a light emitting diode and a Bluetooth Low Energy (BLE) radio. This is the first example of powering a BLE radio by a wearable biofuel cell. Successful generation of high power density under practical conditions and powering of conventional energy-intense electronic devices represents a major step forward in the field of soft, stretchable, wearable energy harvesting devices."
It is thought the device could be used to "monitor health conditions" and using Bluetooth connection, the results could be read from a smartphone.
Mirella Di Lorenzo at the University of Bath added to the New Scientist: "The most exciting application is wearable sensors that can monitor health conditions, then sweat could generate enough power for a Bluetooth connection so that the results could be read straight from a smartphone."