ANU makes atomic force microscopes 20 times more effective

Shining laser beams on the nanowire probes cool them to minus 265 degrees Celsius, allowing the microscope to sense weight much more accurately

Researchers from the Australian National University (ANU) have developed a technique to make atomic force microscopes 20 times more effective by sensing weight that is 100 billion times lighter than a mosquito.

Atomic force microscopes allow researchers to examine nanoscopic structures and the tiny forces between molecules. This research can be used to help better understand viruses.

The challenge with these microscopes is that nanowire probes, whose tips scan over a surface, are prone to vibration as they are 500 times finer than an average human hair.

“At room temperature the probe vibrates, just because it is warm, and this can make your measurements noisy,” said Professor Ping Koy Lam, a co-author of the new research published in Nature Communications.

To solve this, ANU researchers shine laser beams at the probe to cool it to minus 265 degrees Celsius, allowing the microscope to sense weight more accurately. The researchers also used a gold-coated, 200 nanometre-wide silver gallium nanowire to carry out the exercise.

“The laser makes the probe warp and move due to heat. But we have learned to control this warping effect and were able to use the effect to counter the thermal vibration of the probe,” said Giovanni Guccione, a PhD student working on the project.

The researchers are also looking into doing predictive measurements so they do not have to be so reliant on using a laser for every single test over the long term.

The issue with the laser is that it heats up quite quickly after it has cooled, meaning measurements have to be made within a few milliseconds.

“If you imagine that during one time period you just observe the motion of the wires, that gives you information that in the next time period you use to [predict] something. By observing the period before, you can predict if there was anything present to cause the wire to behave in a certain way, for example,” explained Dr Ping Koy Lam from ANU’s Research School of Physics and Engineering.

“This information allows us to process and extract the measurement result much more accurately.”

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