Sweat could soon become a source of power--for wearable devices.
A device in the form of a flexible Band-Aid-like thin strip, which is wrapped around the fingertip, can harvest sweat to generate power without exerting effort. That is even when a person is sleeping or just sitting down, scientists revealed in a Cnet report.
The chemicals in the human sweat is converted into electrical energy by use of this device. Since fingers always emit sweat, the user can power any wearable device without lifting a finger. According to study co-author Joseph Wang--nanoengineering professor at University of California San Diego--using the sweat from the fingertips, "this technology provides a net gain in energy with no effort from the user."
The study was published in the journal Joule.
Human Sweat Chargers to Make Wearables Practical, Convenient
Wearable systems normally take power from bioenergy harvesters that need excessive amounts of energy. But using such a device that could power such systems without exerting any physical effort, wearables would become more "practical, convenient, and accessible" for any person.
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Such a device is ideal for low-power electronics that work in mere milliwatts, just like a wristwatch. But this can't be used for powering upscale gadgets such as smartphones, the researchers added.
The goal is to make the strip a practical device that can generate a small amount of energy to power simple yet useful gadgets like displays and sensors.
Having thousands of sweat glands, the fingertips can generate up to 1,000 times more sweat than other body parts. This is not quite apparent, as sweat would evaporate as it is produced. The thin strip, however, collects the sweat before it evaporates.
How Do These Chargers Convert Human Sweat Into Electricity?
Highly absorbent, the device has a padding of carbon foam electrodes that converts the absorbed sweat into energy. These electrodes have enzymes that cause chemical reactions between the lactate and oxygen molecules in sweat, thus producing electricity. A chip made of piezoelectric material is also placed underneath the electrodes to produce more energy as it is pressed.
The electrical energy is kept in a small capacitor as the wearer presses on it or sweats. This energy can then be used to enable low-powered devices.
A person can keep 400 millijoules of energy while sleeping for 10 hours with the strip placed on the fingertip. This could generate enough power to an electronic wristwatch for 24 hours. More strips attached to more fingertips could generate additional power, the scientists added.
Other devices that could be enabled by these thin strips include Fitbits and other fitness trackers. In other experiments, the device was used to enable a vitamin C sensing system.
Researchers indicated in an interview with The Independent that they envision the technology to be "used in any daily activity involving touch," including those that we do at work, at home, such as watching TV or eating," Wang added.