How do you weigh a proton? With the world's most sensitive scale

Scientists have created a sensor so accurate it can now measure the weight of a single proton. The super scale uses the smallest unit of mass as a measurement, a single yoctogram, whereas previous sensors could only get within 100 yoctograms — a large margin at that scale.

The scale uses nanotubes to detect weight. The nanotubes vibrate at different frequencies depending on the mass of the particles or molecules on them. To achieve the more precise measurement short nanotubes — which are thought to give the best resolution — were used.

The short nanotubes also work at the low temperatures best for measuring frequency. The team from the Catalan Institute of Nanotechnology in Barcelona, Spain was able to tweak the process by adjusting temperature in the measurement process. The equipment is placed in a vacuum to minimize interference from other atoms, but the team took it further by briefly turning the heat up so the nanotubes would give up any bonds with stray atoms.

With this technique, the sensor was able to weigh a single atom of xenon. Taking it to the nearest yoctogram it was able to detect a single proton, which is an incredibly minute 1.7 yoctograms in xenon.

Team leader Adrian Bachtold and his colleagues at the Catalan Institute anticipate these super scales will be used to distinguish elements in chemical samples — as each element will have differing structures and molecular weight at the proton level.

Another application might be in the medical field, helping to diagnose diseases at the molecular level where minute differences in mass could be an indicator of a health condition.

As with all things on the nano-scale, the next challenge will be to find a cost effective way to manufacture the scales — or to streamline the process. Still, the achievement of narrowing down measurement to the sub-atomic level is a significant step.

New Scientist, via io9

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