New wearable fitness trackers ‘could be powered by people’s sweat’

Rob Waugh
·2 min read
The film absorbs water rapidly - and could one day power gadgets (NUS)
The film absorbs water rapidly – and could one day power gadgets. (NUS)

Fitness gadgets of the future could be powered from an unusual source - the sweat pouring out of their wearers’ bodies.

Researchers at the National University of Singapore (NUS) created a film which helps to evaporate sweat from skin as people exercise – harvesting it to generate power.

The film is made from cobalt chloride and ethanolamine, chemicals which rapidly absorb water – and can be reused.

Using small electrochemical cells, the researchers show that sweat can generate power - and could herald a future of fitness devices without batteries.

Read more: Exercising in cold temperatures ‘could help burn off fat’

Assistant Professor Tan Swee Ching, from the NUS Materials Science and Engineering, said: “Sweat is mostly composed of water. When water is evaporated from the skin surface, it lowers the skin temperature and we feel cooler.

“In our new invention, we created a novel film that is extremely effective in evaporating sweat from our skin and then absorbing the moisture from sweat.

“We also take this one step further – by converting the moisture from sweat into energy that could be used to power small wearable devices.”

The film can be reused easily: it rapidly releases water when exposed to sunlight, and can be ‘regenerated’ and reused for more than 100 times.

The team designed a wearable energy harvesting device comprising eight electrochemical cells (ECs).

Each EC can generate about 0.57 volts of electricity upon absorbing moisture – and the experiment showed it was possible to power a light-emitting diode using the cells.

This research was published in the journal Nano Energy.

Read more: Do not wear a mask while exercising, says WHO

The new film absorbs water six times faster than normal materials and sucks up 15 times more moisture, the researchers say.

It also changes colour as it absorbs liquid, from blue to purple, and finally pink.

This means it could be used in shoe insoles and other devices, to show how much water had been absorbed.

Professor Tan said, “Underarm sweating is embarrassing and frustrating, and this condition contributes to the growth of bacteria and leads to unpleasant body odour.

“Accumulation of perspiration in the shoes could give rise to health problems such as blisters, calluses, and fungal infections.

“Using the underarm pad, shoe lining and shoe insole embedded with the moisture-absorbing film, the moisture from sweat evaporation is rapidly taken in, preventing an accumulation of sweat and provides a dry and cool microclimate for personal comfort.”

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