Researchers found lasers could make atomic-force microscope probes 20 times more sensitive and capable of detecting forces as light as an individual virus.
The technique, developed by researchers in the Quantum Optics Group of the Research School of Physics and Engineering, uses laser beams to cool down a nanowire probe to minus 265 degrees Celsius, Australian National University reported.
"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.
The new technique could effectively improve atomic-force microscopes, which measure nanoscopic structures and the force between molecules. These devise measure the microscopic features by scanning a wire probe over the surface, but these are 500 times finer than a human hair and prone to vibration.
"At room temperature the probe vibrates, just because it is warm, and this can make your measurements noisy," said Doctor Ben Buchler, a co-author of the research that is published in Nature Communications. We can stop this motion by shining lasers at the probe."
The team used a 200 nanometer wide silver gallium nanowire coated with gold.
"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 on the team.
The prove is nor effective while the laser is on because it overwhelms the sensitive probe; the laser must be switches off in order for any measurements to be made. An accurate value can be achieved through different cycles of heating and cooling.
"We now understand this cooling effect really well," said PhD student Harry Slatyer. "With clever data processing we might be able to improve the sensitivity, and even eliminate the need for a cooling laser."
