Improving AFMs with Lasers
Lasers are a cool technology, but as science fiction and some science fact tells us, the beams themselves are not cool and can be used to heat and melt objects. As some other science facts also tell us though, lasers can be used to cool objects by exploiting or great control over the properties of the beam. Researchers at the Australian National University have recently used this control to cool the tip of an atomic force microscope, making it much more accurate.
Atomic force microscopes (AFMs) are among the more advanced measurement devices we have and operate by moving a cantilever with a very sharp tip over a sample. At its point, the tip can be just nanometers wide and is very sensitive to forces, such as a surface pushing against it, but also forces between molecules. It is so sensitive though that heat will cause vibrations that introduce noise to the measurements. The Australian researchers decided to tackle that noise by aiming a laser at the probe. By precisely tuning the laser, the vibrations of the probe can be cancelled out, cooling the probe to -265 ºC. This increases the sensitivity enough to detect the weight a large virus.
As the laser beam's effect overwhelms the probe, the AFM cannot be run when the laser is turned on, restricting the researchers to make measurements in millisecond long heating and cooling cycles. With additional study and data processing though, we may one day see the same sensitivity achieved without a cooling laser, thanks to our understanding of the cooling effect.
Source: Australian National University