Fishing Line As Artificial "Muscle"

brindafella writes "Researchers have made what they describe as an 'almost embarrassing' discovery, that twisted nylon fishing line can form a 'powerful, large-stroke, high-stress artificial muscle' capable of lifting as much as 100 times more weight than human muscles. They twisted the fishing line, then heated it to 'set' the shape-memory. The scientists are from the Australian Research Centre of Excellence for Electromaterials Science at the University of Wollongong, and the University of Texas. The findings are published in Science magazine."

Comments

Heat is the limiting factor in our muscles, too

[drinkypoo]

If you can prevent a person from overheating, you can keep them working 2-4 times longer. Muscles are bathed in blood, what coolant will be used for nylon? I suppose automotive stuff would be acceptable.

Re:Heat is the limiting factor in our muscles, too

[drinkypoo]

Heat isn't the limiting factor here, it's what causes the fibre to actuate.

Yes, but they will have to be cooled in order to de-actuate. The rate of thermal transfer is going to limit the working rate. It's fascinating stuff.

Mechanism

[symes]

If I read this right - they coil the line, stretch it and then use heat to return it back to the original coiled state. This then provides lift. I am wondering how much heat is required though. If you have enough of these filaments in an artificial muscle arrangement could you, while lifting your car or running for the bus, spontaneously ignite? That to one side, though, I really love these unexpected breakthroughs.

Re:Mechanism

[Anonymous Coward]

There are broadly speaking 2 varients mentioned in the paper, Nylon and Polythene. The Nylon was heated between 20C and 240C for full contraction, and the Polythene between 20C and 130C.

Re:Mechanism

[HornWumpus]

It should be noted that the crystal melt temperature of nylon 6-6 is 250-260 C.

I thought fishing line was nylon 6. Whose crystalline melt temp is 215-220 C.

Both glass transitions are in the 50-75 C range.

In any case 240C routine heating isn't going to be a long lived 'muscle'.

Fly fishermen have used this property for years

[BitZtream]

I've been using this property to tie flies since I was 5-7 years old ... 30 years ago. It wasn't new then. Admittedly, I never thought about using it or controlling it, but heat treating monofiliment isn't exactly new. Want a tight fly? Heat treat it, then give it a pinch to hold its shape after its good and warm. Use your fingers, not a tool that will nick the line and make it weak, as the heat treating already weakened its tensile strength considerably.

Mono hasn't been around that long so I suppose fly fishermen hasn't been doing it that long either, but still, this property is well known.

If only we had better search tools to be able to find things like this without rediscovering it. Its not wasted research by any means, but it sure does seem like we could make much more progress if we could benefit from the sum of human knowledge rather than the little bit we have domain specific knowledge of and trying to shoehorn everything else into it.

Re:Fly fishermen have used this property for years

[Sockatume]

Suffice to say the process they used is a bit more nuanced than that; I can't link to the paper's figures because of the paywall, but they developed complex hierarchical microstructures of the filaments, and different ones for different applications. (E.g. one structure gives you a fabric with pores that open as it warms up.)

Re:Fly fishermen have used this property for years

[The Grim Reefer]

Monofilament fishing line has been around since 1939 and the most popular type that is used today has been on the market since 1959. Considering all of the uses it has been repurposed for in the last half a century, I wouldn't consider it new, except in a geological timeframe.

Things like this discovery always make me laugh. People will make comments about how obvious this was. But it wasn't until the first time someone figured it out. Otherwise it should have happened sometime in the last fifty years.

Re:Fly fishermen have used this property for years

[arielCo]

Do you mean that the treated nylon re-twisted spontaneously upon heating? I already know that to make a tight knot on a stiff material you can soften it with heat, but this is about "shape memory" - twist, heat, relax; then it will coil up actively when heated:

Spinks says they attached the fishing line to an electric drill and applied tension to the thread.

As it twists, the fibre forms tight coils in a spring-like arrangement. Once heat is applied to the coils it permanently fixes that spring-like shape.

Spinks says to use these springs as artificial muscles heat is again applied, causing the whole coil to contract.

Re:Fly fishermen have used this property for years

[ceoyoyo]

Heating plastic to make it shrink or hold a new shape isn't new. Getting it to cycle from shrunken to unshrunken and back is.

Re:Fly fishermen have used this property for years

[jellomizer]

But they haven't measured and documented it. So it wasn't science, it was hearsay.
There are a lot of truths out there that science hasn't gotten to yet. Heck only a few years ago they calculated how scotch tape rips.

Re:Fly fishermen have used this property for years

[ceoyoyo]

The article describes heating the filament to set it, stretching it back out, then heating it again to contract. Fly fisherman (and kids with hairdryers) only do the first part. In the paper they describe:

A coiled nylon 6,6 muscle delivered over 1 million cycles during periodic actuation at 1 Hz (Fig. 3B), raising and lowering a 10-g weight producing 22 MPa of nominal stress. This actuation was powered by applying a 30 V/cm square-wave potential (normalized to coil length) at a 20% duty cycle. Although the coiled fiber did experience creep (inset of Fig. 3B), this creep was below 2% over the 1.2 million investigated cycles, stroke amplitude was negligibly affected, and the creep rate decreased with cycling.

It does indeed cycle. Reasonably quickly and a lot of times. The article also describes some applications they've successfully built, including automatic window openers that would require multiple cycles.

Re:so they invented the spring

[tippe]

FTFA:

Spinks says to use these springs as artificial muscles heat is again applied, causing the whole coil to contract.
Critically, with the ordinary fibres, the amount of contraction is as much as 50 per cent of the starting length of the coil, he says.

That's a little more "muscle"-like than your average spring, I'd say.

Re:Heck

[Cryacin]

More like tying flies. 95% of time tying em. 5% of the time losing em.

Re:so they invented the spring

[Anonymous Coward]

The interesting part is that it contracts when heat is applied - like a shape memory alloy, but at a fraction of the cost.

Re:so they invented the spring

[rmdingler]

Many breakthroughs are imaginative extensions of existing technologies.

Imagination is more important than knowledge

A.E.

Re:so they invented the spring

[oneandoneis2]

Almost: They invented a *self-coiling* spring - one that can get longer or shorter to order.

You know, like muscles do...

Stretching the definition of artificial muscle

[MobyDisk]

Most artificial muscles work by applying electric current along the muscle. When the current is removed they snap back to their original shape. Using heat sounds very limiting. Presumably you cool it to get it back to the original shape, but the ABC article is light on details.

Re: Fly fishermen have used this property for year

[iamhassi]

I'm sure someone figured it out long ago and I'm sure fishing line has probably already been used for this purpose. This is just the first time someone was willing to swallow their pride and publish it in a scientific journal. I'm sure there are scientists and engineers out there saying "no duh" and "thanks captian obvious" to this article.

Re:"University of Wollongong"

[flyingfsck]

You mean University of Verylongdong?

Out today

[PPH]

Gone fishin'^H^H^H^H^H^HThermo-mechanical materials property researchin'

Re:so they invented the spring

[noahwh]

They're not claiming to have invented a unique mechanism. They're claiming to have implemented a useful known mechanism in a low cost material.

Re:so they invented the spring

[Jarik C-Bol]

Reinventing the wheel is exactly what allows us to travel 80mph without even feeling it. The original wheel probably fell apart at about 5mph after 100 yards. Wow they're rubber, self-healing, last 4000 times longer. Whoever intended the phrase "you're reinventing the wheel" to be an insult was an idiot.