Physicists at the Quantum Optics Group of the Australian National University (ANU) have found a new technique to make microscopes 20 times more powerful than usual. Using this laser technique, the atomic-force microscopes will now be capable of detecting things as small as a virus. The atomic-force microscopes (AFM) are usually used to measure friction, height, magnetism and other properties between molecules.
How did scientists improve the capacity of atomic-force microscopes?
The technique uses laser beams to reduce the temperature of a nanowire probe to minus 265 degrees Celsius. Professor Ping Koy Lam, leader author of the study, said the cooling makes sensitivity level accurate enough to measure the weight of a large virus that is about 100 billion times lighter than a mosquito. The new technique could significantly improve the resolution of atomic-force microscopes, said Lam.
The atomic-force microscopes achieve their extraordinary sensitivity measurements by scanning a wire probe over a surface. These wire probes, or nanowires, are 500 times thinner than a human hair. The nanowire used by ANU scientists was a 200 nm-wide silver gallium coated with gold. They are prone to vibration. Nanowires vibrate at room temperature and make your measurements noisy. Scientists were able to stop the vibration and improve the microscope’s magnifying capacity by “shining lasers at the probe.”
Microscopes measure accurate value through heating and cooling
Heat from the laser makes the probe warp and move. But researchers could control the warping effect, and directed this effect to counter the vibration of the probe. Giovanni Guccione, a PhD student on the team, said that the probe can’t be used when the laser is on because the laser effect overwhelms the highly sensitive probe. So, the laser must be turned off and measurements must be made quickly before the probe heats up. This cycle of heating and cooling takes place within a few milliseconds.
To find the accurate value, measurements are made over multiple cycles of heating and cooling. Findings of the study appeared in the journal Nature Communications.