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Your next phone charger could be at your fingertips !
A new wearable device that wraps around your finger like plaster can harvest sweat while you sleep and use it to generate electricity, its developers claim.
The prototype device only stores up a trickle of power at the moment, and would take about three weeks of constant wear to power a smartphone, but the developers from University of California, San Diego, hope to increase capacity in future.
They found that wearing it for ten hours would generate enough power to keep a watch going for 24 hours or about 400mj (millijoules). And this is just from one fingertip. Strapping devices on the rest of the fingertips would generate 10 times more energy, the researchers said.
Most power producing wearable devices require wearers to perform intense exercise or depend on external sources such as sunlight or large changes in temperature. But the new strip uses a passive system to generate electricity from moisture in your fingertips, even if you are sleeping or sitting completely still, the team explained.
This is because the fingertips are the sweatiest part of the body, so, thanks to a smart sponge material, this can be collected and processed by conductors.
The energy harvester produces small amounts of electricity when the wearer presses down or starts to sweat, or from light finger tapping. It does this by converting activities like typing, texting, playing the piano or tapping in morse code, into extra charge so sending a tweet could power your phone.
Fingertips have one of the highest concentrations of sweat glands in the body, with each digit producing between 100 and 1000 times more perspiration than most other areas, according to the researchers. The device is equipped with electrical conductors or electrodes, made from a carbon foam, which absorbs any finger sweat.
A small chip under the electrodes, made of ‘piezoelectric material’, also generates power when pressed, with the power stored in a small capacitor and discharged to other devices when needed.
To test their device, a volunteer was asked to perform various tasks while wearing it on their finger including typing, tapping and even sleeping. From 10 hours of sleep, the device collected almost 400 millijoules of energy, enough to power an electronic wristwatch for 24 hours. From one hour of casual typing and clicking on a mouse, the device collected almost 30 millijoules, with no effort beyond normal activity.
And in an other experiment, the finger charger was connected to a chemical sensor and a small low-powered screen. Pressing it 10 times every 10 seconds or wearing it for two minutes was enough to power the sensor and screen.
Another experiment was held where the volunteer swallowed a vitamin C tablet and the device was used to power a sensor the researchers developed to read Vitamin C levels. Another sensor designed to measure sodium ion levels in saltwater was also successfully powered by the device.