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posted by janrinok on Wednesday November 06 2019, @10:31PM   Printer-friendly
from the Polymer?-More-Like-Puffermer dept.

Scientists in Sweden and Belgium have discovered a new material that expands (or contracts) by orders of magnitude in response to application of a weak electric current.

When placed in an electrolyte solution, the material expands by a factor of 100 in response to a weak positive electrical pulse. A negatively charged pulse causes the material to return to its original volume.

In follow up experiments, scientists insulated a wire with the new material. When electricity was run through the wire, the thin film of polymer absorbed water and converted to a rapidly expanding gel. When scientists repeated stronger electrical pulses, the gel expanded to a volume 300 percent larger than the film's original size.

Until now, researchers have not been successful in creating a material that was able to change volume anywhere near this significantly in response to an electric current.

There are myriad potential applications for such a substance across disciplines.

If integrated into a sponge or filter, scientists suggest the new material can manipulate via electricity to control the passage of different sized particles.

"We can control the pore size of a filter electronically, and potentially actively control the size of particles that pass through," Magnus Berggren, professor in organic electronics and director of the Laboratory of Organic Electronics at Linköping University, said in a news release.

"This means that the properties of this smart filter can be dynamically changed to allow different types or different sizes of particle to pass through. This function can be used for sieving, filtration, purification, and in process chemistry. It may also have applications in medicine and biochemistry," said.

Another possibility might be in synthetic muscles for robots and prosthetic limbs, where current research relies on activation using other methods such as heat.

Journal Reference
J. Gladisch et al., Reversible Electronic Solid–Gel Switching of a Conjugated Polymer, Advanced Science, p. 1901144, Oct. 2019. DOI: https://doi.org/10.1002/advs.201901144


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  • (Score: 2) by c0lo on Thursday November 07 2019, @04:43AM (2 children)

    by c0lo (156) Subscriber Badge on Thursday November 07 2019, @04:43AM (#917174) Journal

    I've built a couple of robots that use air muscles, inflatable bladders inside a mesh that's secured at each end to a movable piece of kit. This material could be used for a similar purpose and be a lot quieter than air muscles.

    I doubt it. The thing the "inflation" means the strands of the polymer are no longer aligned around the electrode, but get fluffier. Not dissimilar with what happens with someone hair's when staying insulated by the ground and touches a Van De Graaf generator. Except this happens in water, which means that, during "expansion", the volume of water is no longer "outside the polymer zone" but gets between the polymer fibres - you have the same volume of water (a virtual incomprehensible fluid for the purpose of mini-robotics).

    Now, if the "expansion force" those strands can exercise are enough to modify the shape of the enclosure (e.g. transform it from an elongated shape into something rounder), then yes, you could use it as an artificial muscle: the same volume of water in a "thicker" form guarantees the form will be "shorter". But I really doubt the expansion has enough force to act as a mechanical actuator - the 100x time increase in "volume" following a single pulse almost guarantees that there's not enough energy to create mechanical work.

    It is more likely the gizmo will be used exactly how its inventors propose it to be used [liu.se], as a variable pore size filter

    “We can control the pore size of a filter electronically, and potentially actively control the size of particles that pass through. This means that the properties of this smart filter can be dynamically changed to allow different types or different sizes of particle to pass through. This function can be used for sieving, filtration, purification, and in process chemistry. It may also have applications in medicine and biochemistry”, says Magnus Berggren, professor in organic electronics and director of the Laboratory of Organic Electronics.

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  • (Score: 2) by Immerman on Thursday November 07 2019, @07:01PM (1 child)

    by Immerman (3985) on Thursday November 07 2019, @07:01PM (#917437)

    >Except this happens in water, which means that, during "expansion", the volume of water is no longer "outside the polymer zone" but gets between the polymer fibres - you have the same volume of water
    Does that really matter? Put the polymer inside the "muscle mesh", and surround that with a flexible water-tight skin. The volume of water remains the same, but the volume within the muscle changes, and that's all that matters.

    >the 100x time increase in "volume" following a single pulse almost guarantees that there's not enough energy to create mechanical work.
    Two possibilities occur to me of what happens when expanding demands work:
    1) it doesn't expand, and is useless as a muscle
    2) it requires a longer pulse of power to deliver at least as much energy as the mechanical work done, in which case it would work fine.

    Assuming (2), the next important question is how *fast* can it change volume? There's no doubt *some* applications for an electrically actuated muscle that takes four hours to halve in length, but probably not many.

    • (Score: 2) by c0lo on Thursday November 07 2019, @10:46PM

      by c0lo (156) Subscriber Badge on Thursday November 07 2019, @10:46PM (#917595) Journal

      Based on the suggestions made by the researchers (shying away from artificial muscles as a possible use), I doubt this is the case here.

      --
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