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posted by janrinok on Sunday July 21 2019, @12:22PM   Printer-friendly
from the just-what-we-knee'd dept.

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.


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  • (Score: 4, Touché) by Booga1 on Sunday July 21 2019, @01:44PM (3 children)

    by Booga1 (6333) on Sunday July 21 2019, @01:44PM (#869628)

    Weighs .68 lbs and only provides 1.6 microwatts? Why bother when you can use a 0.102oz(2.9g) coin cell battery in it with 220mAh capacity and get about 1375 hours run time at that kind of power usage?

    This thing weighs too much and is too big to haul around for a "self-powered GPS device." Something tells me this professor has never actually gone climbing or mountain hiking, nor even talked to anyone who does those things. Otherwise they would have told him it was a no-go right away.

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  • (Score: 1, Touché) by Anonymous Coward on Sunday July 21 2019, @02:18PM (1 child)

    by Anonymous Coward on Sunday July 21 2019, @02:18PM (#869635)

    Hey, it's a prototype, give them a little benefit of the doubt. Stuff in real production is often much better than the initial proof of concept test samples.

    • (Score: 2) by legont on Sunday July 21 2019, @05:04PM

      by legont (4179) on Sunday July 21 2019, @05:04PM (#869667)

      I am not saying it has no future use. What I am saying is that they faked the measurements pure and simple and were not even smart to hide it well.

      --
      "Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.
  • (Score: 3, Interesting) by JoeMerchant on Sunday July 21 2019, @04:28PM

    by JoeMerchant (3937) on Sunday July 21 2019, @04:28PM (#869658)

    Something tells me this professor got some kind of grant to investigate "zero power" devices and this is the best he could come up with. Not any more impressive than the piezo films I worked with 15 years ago, though his form factor is a little more convenient.

    As you say, a primary cell gives orders of magnitude more bang for your volume, weight, and buck, and by the time the primary cell has run down, the generative device may well have failed due to the harsh environment it is required to endure to capture its power.

    --
    🌻🌻 [google.com]