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The group describes the technology in Applied Physics Letters, from AIP Publishing. An energy harvester is attached to the wearer's knee and can generate 1.6 microwatts of power while the wearer walks without any increase in effort. The energy is enough to power small electronics like health monitoring equipment and GPS devices.
"Self-powered GPS devices will attract the attention of climbers and mountaineers," said author Wei-Hsin Liao, professor in the department of mechanical and automation engineering.
The researchers used a special smart macrofiber material, which generates energy from any sort of bending it experiences, to create a slider-crank mechanism -- similar to what drives a motor. The authors chose to attach the device to the knee due to the knee joint's large range of motion, compared to most other human joints. "These harvesters can harvest energy directly from large deformations," Liao said.
Due to the continuous back-and-forth the material will encounter when the wearer walks, every time the knee flexes, the device bends and generates electricity. This means the harvester can "capture biomechanical energy through the natural motion of the human knee," according to Liao. Previous wearable energy harvesters took advantage of the vibration caused in the device as a result of motion, which comes with drawbacks regarding efficiency.
"The frequency of human walking is quite slow, which significantly decreases the energy-harvesting capability," Liao said. Because the group's device uses a different method, it bypasses this limitation.
The prototype weighs only 307 grams (0.68 pounds) and was tested on human subjects walking at speeds from 2 to 6.5 kilometers per hour (about 1 to 4 miles per hour). The researchers compared the wearers' breathing patterns with and without the device and determined that the energy required to walk was unchanged, meaning that the device is generating power at no cost to the human.
[...] The article, "Macro fiber composite-based energy harvester for human knee," is authored by Fei Gao, Gaoyu Liu, Brendon Lik Hang Chung, Hugo H. Chan and Wei-Hsin Liao. The article appeared in Applied Physics Letters on July 16, 2019 (DOI: 10.1063/1.5098962) and can be accessed at http://aip.scitation.org/doi/full/10.1063/1.5098962.
(Score: 3, Insightful) by The Mighty Buzzard on Sunday July 21 2019, @12:48PM (11 children)
Sorry, that's not how physics works. Without any noticeable increase, maybe, but as stated it's wrong.
My rights don't end where your fear begins.
(Score: 2) by fyngyrz on Sunday July 21 2019, @01:08PM (3 children)
Agreed.
First of all, moving mass through distance — doing work — takes energy. The device is not massless. Therefore, it takes work to move; and that requires energy. Secondly, it takes energy to bend the material in question; there will be some resistance to bending, and also, that mass is being moved through its own, independent distance by the motion of the knee joint.
What the conclusion is here is that the method used to measure the wearer's energy output was not sophisticated enough to tell the difference between device and non-device movement.
--
Ignorance is weakness.
(Score: 3, Interesting) by Anonymous Coward on Sunday July 21 2019, @02:15PM (2 children)
Slight variation -- what if this device took the same amount of energy to flex as the blue jeans that were worn by the control group? Then the energy required would be the same, just that with the device you harvest a tiny bit (instead of the extremely slight heating of the jeans due to flexing).
Clothing does waste some energy, compare to the nice sense of freedom when walking around naked!
(Score: 1, Funny) by Anonymous Coward on Sunday July 21 2019, @04:50PM
> Clothing does waste some energy, compare to the nice sense of freedom when walking around naked!
I tried that. The police came. I don't have a sense of freedom anymore. :(
(Score: 0) by Anonymous Coward on Sunday July 21 2019, @06:36PM
Just try short-shorts. You'll already get a huge improvement.
(Score: 2) by HiThere on Sunday July 21 2019, @04:08PM (1 child)
Not clear. If it only extracted energy on the downhill (compression) cycle, it might actually help. OTOH, an optimally "designed for walking" knee would already be extracting that energy. Kangaroos do it, but humans are recently apes living in trees, so they might not have that optimization.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 0) by Anonymous Coward on Monday July 22 2019, @06:32AM
AFAIK penguins have the most energy efficient walk, they wobble around. Just not going to catch any prey or escape a predator that way. But they do it because their enemy is the winter cold at Antarctica and they catch fish while swimming, not walking.
(Score: 2) by JoeMerchant on Sunday July 21 2019, @04:18PM (1 child)
I'm going to notice the #$)*( thing when it's just sitting there attached to me, much more so as I walk and it tugs at my skin and/or prevents my sweat from evaporating at the interfaces.
I may not notice the effort required to bend it, but it will take strong glue to keep me from unconsciously clawing it off of my body.
🌻🌻 [google.com]
(Score: 2) by JoeMerchant on Sunday July 21 2019, @06:40PM
Above was written before 1.6 microwatts was processed.... yeah, 1.6 microwatts, weighs 300gm, um... who cares?
A 1cm x 1cm solar cell should be good for 16 milliwats in full sun (a full 1m x 1m solar panel nets 160W), 1/1000th of that?
TFS should have lead with something from the vanishing significance dept.
🌻🌻 [google.com]
(Score: 0) by Anonymous Coward on Sunday July 21 2019, @06:16PM (1 child)
So this device will not work for goose-stepping fascists but the heel device would.
(Score: 2) by The Mighty Buzzard on Monday July 22 2019, @10:48AM
Antifa will be crushed. They were going to start ironically goose-stepping next week. Wile missing the irony that they really are fascists, of course.
My rights don't end where your fear begins.
(Score: 0) by Anonymous Coward on Sunday July 21 2019, @08:25PM
They'd be better off trying to harvest boob kinetic energy. The main downside is that they wouldn't bounce so much.