• Design tweak helps prevent malfunction i

    From ScienceDaily@1:317/3 to All on Tue Mar 22 22:30:48 2022
    Design tweak helps prevent malfunction in yarns designed to store energy


    Date:
    March 22, 2022
    Source:
    North Carolina State University
    Summary:
    Findings in a recent study could advance the development of 'smart
    textiles' that would capture energy from the wearer's movements.



    FULL STORY ==========================================================================
    In a new study, North Carolina State University researchers found a way
    to prevent electrical malfunctions in yarns designed to store electrical energy.

    Ultimately, the findings could help advance the development of "smart
    textiles" that would capture energy from the wearer's movements and
    power sensors and wearable electronics.


    ==========================================================================
    The researchers reported in npj Flexible Electronics that they were
    able to prevent short-circuiting in yarns that act as supercapacitors --
    which are electrical devices that store energy -- by wrapping the yarns
    with an insulating thread. They also tested the strength and durability
    of the yarns to make sure they could still work after going through
    knitting and weaving processes.

    "A supercapacitor functions like a battery, but in this case, we're
    working on a flexible battery shaped as a textile yarn that you could
    weave or knit into your T-shirt or sweater," said Wei Gao, associate
    professor of textile engineering, chemistry and science and a University Faculty Scholar at NC State. "In this study, we have woven this yarn
    into a piece of fabric so that it can store electrical energy, and
    eventually we want to use it to power whatever electronic devices
    you need, whether it be a sensor, a light or even a cell phone."
    While research into these so-called "yarn-shaped supercapacitors" is
    promising, researchers say developers face a consistent problem with
    their design: the yarn-shaped supercapacitors are more likely to short
    circuit as their length increases. Short-circuiting is when the electric current flows through an unintended path. It is a safety concern because
    a short circuit can result in a burst of heat energy or even a fire.

    "Everybody is trying to make smart electronics that can be incorporated
    into cloth or fabric," Gao said. "What we found is if you try to make
    a supercapacitor yarn longer than 8 inches, it's pretty easy for this
    device to short-circuit. It's pretty dangerous, and it's something nobody
    wants to encounter when wearing a smart suit." To solve that problem, the researchers tested what would happen when they wrapped the super-capacitor
    yarn electrodes with insulating threads. The idea was that the threads
    would act as a physical barrier, keeping the opposite electrodes from contacting each other and preventing short-circuiting. They tested their device's performance by connecting the electrodes to a power source and recording the device's current response. They also tested how well the
    yarns were able to hold a charge. They found that the yarns kept 90%
    of the initial energy after charging and discharging them 10,000 times.



    ==========================================================================
    The researchers also tested to see if they could withstand bending and stretching by weaving their yarn-shaped supercapacitors into a fabric.

    "The yarns need to be flexible and strong enough so that when you bend,
    stretch and press them, they keep their original electrical performance
    after all of those mechanical deformations," said the study's lead author Nanfei He, postdoctoral research scholar in textile engineering, chemistry
    and science at NC State. "The yarns all kept their original performance,
    even after going through weaving and knitting." Researchers said they
    made the yarn-shaped supercapacitor using processes that are conventional
    in textile manufacturing.

    "All of these processes can be scaled up very easily," He said.

    In future work, the researchers want to incorporate their design into a garment, and to try to integrate it with other energy-generating devices.

    "Materials innovation and process engineering are critical to the
    scalability and device performance," said Feng Zhao, CEO of Storagenergy Technologies Inc., the industrial partner of the project. "We have
    developed a process to produce thousands of meters of high-performance
    yarns in a continuous manner." The study, "Separator Threads in
    Yarn-Shaped Super-capacitors," was published online in npj Flexible Electronics. In addition to He and Gao, the other authors were Junhua
    Song, Jinyun Liao and Feng Zhao of Storagenergy Technologies Inc. The
    study was supported by Storagenergy Technologies Inc., and funded by the
    United States Army under contract numbers W911NF19C0074 and W911NF18C0086.


    ========================================================================== Story Source: Materials provided
    by North_Carolina_State_University. Original written by Laura
    Oleniacz. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Nanfei He, Junhua Song, Jinyun Liao, Feng Zhao, Wei Gao. Separator
    threads in yarn-shaped supercapacitors to avoid short-circuiting
    upon length. npj Flexible Electronics, 2022; 6 (1) DOI:
    10.1038/s41528-022- 00150-2 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220322154216.htm

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