Los Angeles, Jun 23 (PTI): Scientists have created a skin patch that can power a radio for two days using human sweat, and may eventually be used to charge mobile devices while people are out for a run.

The bio fuel patch may also provide a way to monitor glucose levels in people with diabetes, without needles and blood samples, researchers said.

The skin patch developed by researchers from University of California, San Diego in the US is a flexible square just a couple of centimetres across and sticks to the skin.

It contains enzymes that replace the precious metals normally used in batteries and uses sweat to provide power.

Getting enough power out of a bio fuel cell to make it useful has proved tricky, but the latest version can extract 10 times more than before, researchers said.

"We are now getting really impressive power levels. If you were out for a run, you would be able to power a mobile device," said Joseph Wang from the University of California, San Diego.

Researchers used the lactate found in sweat to power their particular bio fuel cell, 'News Scientist' reported.

The amount of lactate or lactic acid in sweat is also related to how efficiently a person's muscles are working, so could help give readings on an athlete's performance during exercise, researchers said.

Similarly, levels of glucose in sweat are related to its concentration in the blood, they said. The findings were published in the journal Energy and Environmental Science.