Physicists Use Lasers to Improve Sensitivity of Atomic-Force Microscope

Australian physicists have used lasers to make atomic-force microscope probes 20 times more sensitive than the current ones.

Quantum Optics Group of the Research School of Physics and Engineering researchers say that cooling nanowire probe to minus 265 degrees Celsius using lasers can improve the resolution of atomic-force microscopes.

The atomic-force microscopes are used to measure nanoscale structures and tiny forces between molecules. AFMs are a type of scanning probe microscopes that are designed to measure some properties such as height, friction and magnetism.

These microscopes have a wire probe that scans a surface. The probe is so sensitive that minute vibrations can disturb measurements.

"At room temperature the probe vibrates, just because it is warm, and this can make your measurements noisy," said Dr Ben Buchler, a co-author of the research, according to a news release.

"We can stop this motion by shining lasers at the probe," he added.

Using laser to counter the effect of room temperature increased the sensitivity of the probe.

"The level of sensitivity achieved after cooling is accurate enough for us to sense the weight of a large virus that is 100 billion times lighter than a mosquito," said Professor Ping Koy Lam, the leader of the Quantum Optics Group, according to a news release.

In the study, the researchers used 200 nm-wide silver gallium nanowire coated with gold. The wire is about 500 times thinner than a human hair. According to the researchers, the laser makes the probe warp and move due to heat. But, this warping counters the effect of thermal vibration and helps the researchers control the movement of the probe.

The team say that the probe can't be used, while the laser is beamed on it as the light overwhelms the wire. To make the measurements, the researchers have to switch off the laser and then measure the forces in few milliseconds, before the probe gets heated due to rise in room temperature.

The study is published in the journal Nature Communications.