Intelligent Machines

Nanotube Motor

Artificial muscles could power tiny actuators and microfluidic mixers

  • by MIT TR Editors
  • December 20, 2011
  • Skinny strength: This carbon nanotube yarn, which has a diameter of 3.8 micrometers, twists when connected to an electrode and immersed in conductive liquid.

Source: “Torsional Carbon Nanotube Artificial Muscles”
Ray Baughman et al.
Science
334: 494–497

Results: Researchers at the University of Texas at ­Dallas made nanotube yarn that twists in response to electricity, enabling it to act as a motor. For a given length, it twists 1,000 times more than other materials designed for use as tiny motors, such as shape-­memory alloys that change shape in response to heat or another stimulus. The fastest of the nanotube motors spins at 600 revolutions per minute and can generate as much twisting force as a conventional motor. Researchers demonstrated this ability by using it to mix fluids with a paddle.

Why it matters: Making useful motors for very small applications has been difficult because decreasing the size of conventional motors greatly decreases the amount of twisting force they can exert relative to their weight. Even at this scale—just a fraction of a hair’s width—the nanotube yarn can exert as much force relative to its weight as a large motor. It could be useful for moving fluids around in microfluidic devices.

This story is part of our January/February 2012 Issue
See the rest of the issue
Subscribe

Methods: The researchers used previously ­developed methods to twist carbon nanotubes together into a thin yarn. They dipped one half of the yarn, along with an electrode, in an electrolyte. They also attached a paddle to the middle of the piece of yarn and anchored both ends to prevent them from rotating. When they applied electricity, ions from the electrolyte were attracted to electrons in the nanotubes. As the ions moved into the yarn, its volume increased, causing it to partially untwist; this, in turn, made the paddle move. When the power was cut, the half of the yarn that wasn’t immersed in the electrolyte acted as a spring that returned the paddle to its original position.

Next Steps: The researchers are now building microfluidic circuits that use the motors as pumps and mixers. They are also starting to make robots the size of bacteria that are propelled by the nanotube yarns.

Cut off? Read unlimited articles today.

Become an Insider
Already an Insider? Log in.

Uh oh–you've read all of your free articles for this month.

Insider Premium
$179.95/yr US PRICE

More from Intelligent Machines

Artificial intelligence and robots are transforming how we work and live.

Want more award-winning journalism? Subscribe to Insider Plus.
  • Insider Plus {! insider.prices.plus !}*

    {! insider.display.menuOptionsLabel !}

    Everything included in Insider Basic, plus ad-free web experience, select discounts to partner offerings and MIT Technology Review events

    See details+

    What's Included

    Bimonthly home delivery and unlimited 24/7 access to MIT Technology Review’s website.

    The Download. Our daily newsletter of what's important in technology and innovation.

    Access to the Magazine archive. Over 24,000 articles going back to 1899 at your fingertips.

    Special Discounts to select partner offerings

    Discount to MIT Technology Review events

    Ad-free web experience

/
You've read all of your free articles this month. This is your last free article this month. You've read of free articles this month. or  for unlimited online access.