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Atomic Force Microscopes

January 24, 2008

Atomic Force Microscopes (AFMs) can “see” things that are smaller than a nanometer – which is much better resolution than what’s possible with optical microscopes. How do they do that? How are AFMs used?

In the East Wing of the Main Building on Nanotechnology Island, there’s a Surface and Nano-Analysis Lab with a model of an AFM. (There’s also a model of a SIMS, which I’ll write about some other day.)

If you sit on the stool at the AFM, you can click on various samples to analyze them -an image appears on the computer screen, and you also get a notecard explaining what you see. Samples include a human hair, tungsten nanoparticles on a gold surface, and a PVC/PC polymer blend.

You can also click on the doors of the AFM enclosure, then click on the head of the AFM to see the innards a bit.

Outside the Surface and Nano-Analysis Lab is an exhibit which explains the principles of AFMs. The basic idea is that a needle is dragged across the surface of the sample being analyzed, a bit like a record player. The up-and-down motion of the needle tells you about how the height of the surface varies from place to place. (This is all roughly speaking, for clarity.)

AFMs can actually be operated in a variety of different imaging modes. The exhibit animates four of those modes: constant height, constant force, intermittent contact, and force modulation. Explanations of the modes are also given.

You can check it all out now, at Nanotechnology Island.

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