Electronics

Liquid metal electrical wires can be stretched without breaking

One of NC State's stretchable conductive wires being put to the test
One of NC State's stretchable conductive wires being put to the test
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One of NC State's stretchable conductive wires being put to the test
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One of NC State's stretchable conductive wires being put to the test

Things like earbud cords have a nasty way of getting hooked on things and breaking. Such incidences may become a lot less common, however, as scientists from North Carolina State University have created conductive wires that stay intact even when stretched up to eight times their regular length.

The researchers made the wires by filling a tube of extremely elastic polymer with a liquid metal alloy of gallium and indium. As a result, even when the polymer is stretched to several times its relaxed state, the liquid metal inside of it is still able to carry an electrical current. A demonstration can be seen in the video below.

Ultra Stretchable Wires

According to NC State’s Dr. Michael Dickey, other efforts at creating stretchable electrical wires have involved embedding metals or other conductive materials within the polymer matrix itself. Doing so, however, compromised the elasticity of the material.

“Our approach keeps the materials separate, so you have maximum conductivity without impairing elasticity,” he said. “In short, our wires are orders of magnitude more stretchable than the most conductive wires, and at least an order of magnitude more conductive than the most stretchable wires currently in the literature.”

Not only could the wires be useful in devices like earbuds or phone chargers, but they could also find use in smart fabrics or stretchable electronics. Some of NC State’s other approaches to routing electricity through such materials have involved the use of coiled nanowires or carbon nanotubes that straighten out as the material stretches.

Before the new wires make their way into anything, however, the scientists still need to figure out how to minimize leakage of the liquid metal should the polymer be damaged.

Scientists from Northwestern University are conducting similar research – they’ve developed a stretchable electronic material in which liquid metal is deposited within the pores of an elastic polymer.

Source: North Carolina State University

6 comments
Dave MacLachlan
Wonder what the freezing point for the liquid metal alloy is? I would imagine that a typical winter day would make ear bud wires pretty rigid.
windykites
They don't need coiled nanowires, just helically coiled copper wires, which stretch easily. The elastic coating would re- tighten up the winding, as the tension was released.
notarichman
a sucky idea; using two rare earth metals is a waste... a better idea that serves another purpose might be to use mercury. then the user would have to take his/her chances on being poisoned... or actually listen to the rest of the world?
Bassmandan
To solve the leakage problem when the polymer sheath is compromised, they may want to look to biological solutions. If there were a component that could be mixed with the gallium/indium that would mimic the fibrinogen in blood, they could ostensibly induce the metal to form the equivalent of a clot. I suppose oxygen would be the obvious catalyst for the reaction and the “clot” may only need to be microns thick. This could also help with the wires’ terminations as long as the clot forming component was sufficiently conductive.
rdlongview
How do you connect them? I would guess it'd be a bit hard to strip and crimp on a connector.
Simon De Meulemeester
Good thing indium and gallium are dirt cheap.