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Researchers: Electron Beams Could Function as Nano-Scale 'Tweezers


"...resolution and sensitivity 1,000 times finer than optical techniques."

Electron microscopes shoot a beam of electrons at an object to achieve a higher resolution than traditional light microscopes. The electrons have a shorter wavelength than visible light, which allows them to achieve this higher resolution. But, scientists have recently found a new purpose for these electron beams as a "tweezers."

So this means beams of electrons could move other objects? That's exactly what Vladimir Oleshko at the U.S. National Institute of Standards and Technology and James Howe at the University of Virginia found while studying droplets of aluminium and silicon, according to New Scientist:

Optical tweezers work thanks to the force generated when a particle refracts light, which pushes the object to the most intense part of a beam. Electron beams generate the same force, says Oleshko. The new tweezers have a resolution and sensitivity 1,000 times finer than optical techniques. Oleshko hopes to use them in the near future to manipulate single atoms.

Watch it in action here:

According to the NIST news release, the researchers compare this to the electron version of optical tweezers, which are already in use for moving tiny particles in several scientific fields. An optical tweezer is essentially a laser beam of light that attracts particles in order to manipulate them:

If you just consider the physics, says NIST metallurgist Oleshko, you might expect that a beam of focused electrons—such as that created by a transmission electron microscope (TEM) — could do the same thing. However that’s never been seen, in part because electrons are much fussier to work with. They can’t penetrate far through air, for example, so electron microscopes use vacuum chambers to hold specimens.

So Oleshko and his colleague, UVA materials scientist James Howe, were surprised when, in the course of another experiment, they found themselves watching an electron tweezer at work. They were using an electron microscope to study, in detail, what happens when a metal alloy melts or freezes. They were observing a small particle—a few hundred nanometers wide—of an aluminum-silicon alloy held just at a transition point where it was partially molten, a liquid shell surrounding a core of still solid metal. In such a small sample, the electron beam can excite plasmons, a kind of quantized wave in the alloy’s electrons, that reveals a lot about what happens at the liquid-solid boundary of a crystallizing metal. “Scientifically, it’s interesting to see how the electrons behave,” says Howe, “but from a technological point of view, you can make better metals if you understand, in detail, how they go from liquid to solid.”

Even with hopes for this to work in manipulation of other small objects, Oleshko says using the electron beam will still be challenge as it requires work to be done in a vacuum.

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