Artificial Muscles Pack a Mean Punch

sciencehabit writes "Here's a twist: Scientists have designed a flexible, yarn-like artificial muscle that can also pack a punch. It can contract in 25 milliseconds—a fraction of the time it takes to blink an eye—and can generate power 85 times as great as a similarly sized human muscle. The new muscles are made of carbon nanotubes filled with paraffin wax that can twist or stretch in response to heat or electricity. When the temperature rises, the wax melts and forces the nanotubes to contract. Such artificial muscles, the researchers say, could power smart materials, sensors, robots, and even devices inside the human body."

Robots don't regenerate

[Turksarama]

On top of the power efficiency I'm also wondering how many times a muscle can be used before it gets too damaged.

Really?

[Anonymous Coward]

Contract in 25 mS - what does that mean? The time before contraction is initiated? Or is it related to shortening velocity? If so, over what distance and how liner is the contractile force? Then there's recovery time before the next contraction; the force generated per unit cross sectional area of this material (what do they exactly mean by "size"); efficiency and heat dissipation. As with all these hyped technology claims that purport to mimic biological systems there's an embarrassing lack of detail. And optimistic expectations for attracting venture capital I imagine. I'm very skeptical this would compete with mammalian or avian skeletal muscle on any number of important functional parameters. If it did and it was mine, I would be shouting the numbers from the rooftops.

fiber recharge time less than 50 milliseconds

[girlinatrainingbra]

Sulphur, I don't have access through the paywall to the article, but I calculate the fiber recharge time to be less than 50 milliseconds:
"delivers 3% tensile contraction at 1200 cycles/minute"
The abstract explicitly states that they tested the carbon-nanotube fibers for up to 1-million cycles with a rep-rate of 1200 cycles/minute, so that gives us 20 Hz, so the recharge/rep time is less than 1/20th of a second = 50 milliseconds:
.
The article's abstract (Electrically, Chemically, and Photonically Powered Torsional and Tensile Actuation of Hybrid Carbon Nanotube Yarn Muscles) [sciencemag.org] has this to say about how many times this Nanotube yarn muscle can be used:
.
We have designed guest-filled, twist-spun carbon nanotube yarns as electrolyte-free muscles that provide fast, high-force, large-stroke torsional and tensile actuation. More than a million torsional and tensile actuation cycles are demonstrated, wherein a muscle spins a rotor at an average 11,500 revolutions/minute or delivers 3% tensile contraction at 1200 cycles/minute. [bold text added by me to accentuate the answer, at least one million cycles demonstrated thus far]