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Atomic force microscope sensitivity increases 20 times, thanks to laser cooling

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Microscopes are now 20 times more sensitive than ever before, thanks to lasers. The new evolution in microscopy is also able to detect extremely subtle forces, as light as the weight of a single virus, roughly 100 billion times less massive than a mosquito.

Laser beams are used to super-cool a tiny nanowire probe to a chilly 445 degrees below zero Fahrenheit.

Atomic force microscopes, which measure the minuscule forces between molecules, could be advanced by the new laser-based technology. These devices operate through the use of a tiny silver-gallium nanowire, coated in gold. This fine wire is 500 times thinner than a human hair. However, these structures are subject to shaking, caused by heat.

"At room temperature the probe vibrates, just because it is warm, and this can make your measurements noisy. We can stop this motion by shining lasers at the probe," Ben Buchler, from the Department of Quantum Science at the Australian National University (ANU), said.

Lasers create vibrations in the nanowire, but by carefully guiding characteristics of the energy, researchers were able to synchronize those vibrations to eliminate shaking due to ambient heat.

The microscope cannot be used while the laser is in operation, as  energy from the light-based cooling system completely overwhelms signals from the object being examined. This means researchers have to carefully time their measurements, recording data in a few thousands of a second, before the nanowire begins to warm once more.

"We now understand this cooling effect really well. With clever data processing we might be able to improve the sensitivity, and even eliminate the need for a cooling laser," Harry Slatyer, a doctoral student at ANU, told reporters.

Atomic force microscopes are capable of resolutions 1,000 times more detailed than the theoretical limit for optical devices. The tiny nanowire is affixed to a probe on the microscope. As this probe is drawn near the surface of a sample, electromagnetic forces create tiny movements in the nanowire, which are recorded as the "shadow" of the tiniest particles of matter. The first of these machines was developed in 1986, providing the first "images" ever seen of the movement of atoms and molecules.

In addition to observations of the building blocks of matter, atomic force microscopes may also be employed in moving individual atoms and molecules. This ability can be used to create the tiniest structures possible, using just a few particles.

Development of the ultra-sensitive laser-based microscope was detailed in the journal Nature Communications.

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