Wednesday 14 July 2021
a little sweat is enough
Device draws energy from fingers while sleeping
When working on a computer do not only consume energy, but also gain it? Or even while doing nothing, ie while sleeping? It works with a new device that generates electricity from the fingers. Sweating or mechanical pressure is sufficient for this. The whole thing is called “energy harvesting”.
A newly developed device extracts energy from sweat on the fingers – even when a person is sleeping. The device is affixed to a plaster-like tape and generates an electric current from parts of the sweat with a biofuel cell. Another component also generates electricity from mechanical pressure, As scientists from the University of California at San Diego report in the journal “Joule”.
The sweat glands on the fingers are much closer together than on other skin areas. According to researchers, a finger can secrete 80 to 160 grams of sweat per hour. “The buildup of more sweat on our fingers probably evolved to help us grip things better,” first author Lu Yin is quoted in a statement to the magazine.
Wang and his colleagues used a biofuel cell, and they also developed a foam made of carbon nanotubes through which sweat can perspire. This foam forms the electrode, which becomes the anode when the enzyme lactate oxidase is added. Here, lactates from sweat are chemically converted and energy is produced from it. Such production of small amounts of electrical energy from the environment is called “energy harvesting”.
When you sleep for about ten hours, the device generates about 400 millijoules of energy. A single finger press produces about 30 millijoules, because in addition to the biofuel cell, an element has also been created that generates electricity by mechanical pressure. Researchers have calculated that the body consumes about 0.5 millijoules to tap a finger, so that 30 millijoules uses 6,000 percent of the energy. “You can forget about the device and go to sleep or do desk work like typing and still generate electricity,” says Wang.
Enough power to power the sensor and display
To show what the energy received could be used for, the scientists connected the device to a vitamin C sensor and a simple electro-chromatic display. The biofuel cell generated enough electricity to power both the sensor and the display.
In a test person who took a vitamin C pill, researchers were able to measure an increase and subsequent decrease in the amount of vitamin C in sweat. They similarly measured the sodium content of sweat.
“We envision that this device can be used in any daily touch-based activity – things that a person would normally do at work, at home, while watching TV or eating anyway,” Wang said. Scientists can imagine integrating the device into a lightweight glove and thus supplying a variety of portable electronics with electricity.
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