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Registered: 09/01/02
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Berkeley Physicists Build World's Smallest Motor
    #1778826 - 08/04/03 06:12 PM (14 years, 8 months ago)

I enjoy seeing breaks in technology like this one. The telescopic nature of discoveries is taking amazing speeds.


Berkeley Physicists Build World's Smallest Motor

A UC-Berkeley physicist has created the first nanoscale motor ? a gold rotor on a nanotube shaft that could ride on the back of a virus.

"It's the smallest synthetic motor that's ever been made," said Alex Zettl, professor of physics at UC-Berkeley and faculty scientist at Lawrence Berkeley National Laboratory. "Nature is still a little bit ahead of us ? there are biological motors that are equal or slightly smaller in size ? but we are catching up."

Zettl and his graduate students and post-docs report their feat in the July 24 issue of Nature.

The electrostatic motors represent a milestone in nanotechnology, and prove that nanotubes and other nanostructures several hundred times smaller than the diameter of a human hair can be manipulated and assembled into true devices.

Zettl and other scientists had previously made transistors from nanotubes, but this device is different, he said.

Such motors could have numerous uses, Zettl said. Because the rotor can be positioned at any angle, the motor could be used in optical circuits to redirect light, a process called optical switching. The rotor could be rapidly flipped back and forth to create a microwave oscillator, or the spinning rotor could be used to mix liquids in microfluidic devices.

The motor is about 500 nanometers across, while the part that rotates, the rotor, is between 100 and 300 nanometers long. The carbon nanotube shaft to which it is attached is only a few atoms across, perhaps 5 to 10 nanometers thick.

An example of one of the unexpected difficulties, for example, is that the techniques for measuring the motor's speed are as yet too crude. The team's scanning electron microscope (SEM) can take pictures every 33 milliseconds and no faster, so they can't tell whether the rotor spins or flips faster than 30 times per second.

"We assume you could go much, much faster than that, probably to microwave frequencies," Zettl said. "There's no way we can detect that right now, but in principle the motor should be able to run that fast."

The motor's shaft consists of nested nanotubes much like the layers of a leek. Annealed both to the rotor and fixed anchors, the rigid nanotube allows the rotor to move only about 20 degrees. The team was able to break the outer wall of the nested nanotubes to allow the outer tube and attached rotor to freely spin around the inner tubes as a nearly frictionless bearing.

To build the motor, Zettl and his team made a slew of multiwalled nanotubes in an electric arc and deposited them on the flat silicon oxide surface of a silicon wafer. They then identified the best from the pile with an atomic force microscope, a device capable of picking up single atoms.

A gold rotor, nanotube anchors and opposing stators were then simultaneously patterned around the chosen nanotubes using electron beam lithography. A third stator was already buried under the silicon oxide surface. The rotor was annealed to the nanotubes and then the surface selectively etched to provide sufficient clearance for the rotor.

When the stators were charged with up to 50 volts of direct current, the gold rotor deflected up to 20 degrees, which was visible in the SEM. With alternating voltage, the rotor rocked back and forth, acting as a torsional oscillator. Such an oscillator, probably capable of microwave frequency oscillations from hundreds of megahertz to gigahertz, could be useful in many types of devices - in particular, communications devices such as cell phones or computers.

With a strong electrical jolt to the stators, the team was able to jerk the rotor and break the outer wall of the nested nanotubes, allowing the rotor to spin freely on the nested nanotube bearings. Zettl had made similar bearings several years ago, but this was the first time he had put them to use.

The rotor does not continue spinning for long once the electricity is turned off. It is so small that it has little inertia, so any tiny electric charges remaining on the device after it's turned off tend to stop the rotor immediately.

Zettl expects to be able to reduce the size even further, perhaps by a factor of five. For the moment, though, he and his team are trying to make basic quantum measurements, such as the conductance through the nanotubes and the amount of friction in the bearings.

The work is supported by the National Science Foundation and the Office of Energy Research of the U.S. Department of Energy.

July 24, 2003

Source: link.

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Re: Berkeley Physicists Build World's Smallest Motor [Re: Meph]
    #1779598 - 08/04/03 10:59 PM (14 years, 8 months ago)

Wow, and I'm going to be studying at Berkeley. Look forward to seeing such things.

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Re: Berkeley Physicists Build World's Smallest Motor [Re: daba]
    #1781068 - 08/05/03 11:13 AM (14 years, 8 months ago)

Next step is a nano ROV and then use it for exploring space.
I wonder what kind of magnetic field they create and if it could lead to better batteries as well. lots of potential.

Astronauts get all the tang they want.

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Re: Berkeley Physicists Build World's Smallest Motor [Re: Meph]
    #1785578 - 08/06/03 05:36 PM (14 years, 8 months ago)

Discoveries like this are happening exponentially more and more often I would assume, it's just that we don't hear about all of them since the average person wouldn't really care (although it could radically change their life style). I wonder if McKenna is right and that all of this technological advancement will peak in 2012 and a whole new way of life for all humans will come to be.

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