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Pushing Atoms

Pushing Atoms

Scientists have calculated the force it takes to move one atom.


Transcript

What it takes to move an atom. I'm Bob Hirshon and this is Science Update.

For the first time, researchers have measured the force it takes to move a single atom: a force that makes a gentle brush from a cat's whisker look like an asteroid impact. The team included Markus Ternes, a postdoctoral fellow at IBM's Almaden Research Center in California. Depending on the surface it was on, Ternes says moving a cobalt atom required a force as small as 17 piconewtons.

Ternes:

And to put it into perspective, to move an atom you need about a billionth of the force you would need to lift a piece of chocolate.

To do it, they created a super-vacuum at minus-454 degrees Fahrenheit—a temperature so cold that atoms don't bounce around on their own. The findings could eventually help scientists who are working to build brand new substances, one atom at a time. I'm Bob Hirshon for AAAS, the Science Society.


Making Sense of the Research

One of the hottest fields in science right now is nanotechnology. The prefix “nano” means “one-billionth” (just as “centi” means “one-hundredth” and “milli” means “one-thousandth”). Nanotechnology is the engineering of substances on the nanometer scale, which is the scale of molecules and atoms. (A typical atom is a fraction of a nanometer in diameter, while microbes and viruses range from tens to thousands of nanometers in diameter).

One goal of nanotechnology is to make incredibly tiny mechanical parts, like transistors, sensors, radio receivers, and computer chips, for nano-sized machines that run on minimal power and can fit in tight spaces like the human bloodstream. Another is to create new, human-scale materials by building them one atom or molecule at a time. In other words, instead of making things out of existing raw materials like plastic, diamond, or silicon, they hope to create entirely different raw materials. That could open up a whole new frontier of engineering.

Of course, putting together atoms is much harder than laying bricks and mortar. For one thing, you need a way to push single atoms around without disturbing the other ones. In addition, you've got to control the movement of the atoms. Normally they bounce and vibrate in ways that are difficult to control. That's why the researchers chilled their test chamber to about minus-454 Fahrenheit, or just a few degrees Kelvin. (At 0 degrees Kelvin, or absolute zero, molecules stop moving altogether.) They also created a super-vacuum devoid of other molecules besides the cobalt atom or carbon monoxide molecule they were manipulating. Then they used an atomic force microscope tip to carefully drag the atom or molecule across a copper or platinum surface.

They found that the force required ranged from 17 piconewtons to 210 piconewtons, depending on the atom and the surface it was being moved across (a newton is, in the meter-kilogram-second system, the unit of force required to accelerate a mass of one kilogram one meter per second per second). Their discovery revealed that different substances exert markedly different friction forces on the atom being moved. Presumably, each combination of molecule and surface will require its own exact force. By showing that this force can, in fact, be measured, the experiment suggests that it may be possible to build nanoscale factories that build with great precision.

Now try and answer these questions:

  1. What is nanotechnology?
  2. A nanometer is a billionth of a meter. For comparison, calculate a billion times your own height. How long is that, in miles? What in the universe is about that length?
  3. Why did the researchers have to create such specific conditions in order to conduct the experiment?
  4. Why would building materials atom by atom be such a breakthrough?

You may want to check out the March 14, 2008, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: archaeologists digging deep, the mystery of Maya Blue, where your hair has been, and more.


For Educators

The National Geographic online feature Nano's Big Future introduces students to the world of nanotechnology.

The National Geographic News article Nanotech: The Tiny Science Is Big, and Getting Bigger also provides an overview of nanotechnology.


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