writes "Caltech scientists have created an ultra-sensitive device that can weigh an individual molecule for the first time. The device is invisible to the naked eye and vibrates at a specific frequency based on the molecule resting on top of its bridge like structure."
More in the Caltech press release
. This is an improvement on a design from 2009
that also could theoretically weigh a single molecule, but in practice could not because the position along the "bridge" affected the result. Now the researchers have figured out how to measure the position of the molecule on the bridge and compensate. The device is built using semiconductor fabrication techniques "...making it easy to mass-produce. That's crucial, since instruments that are efficient enough for doctors or biologists to use will need arrays of hundreds to tens of thousands of these bridges working in parallel. 'With the incorporation of the devices that are made by techniques for large-scale integration, we're well on our way to creating such instruments,' Roukes says. This new technology, the researchers say, will enable the development of a new generation of mass-spectrometry instruments." The full article
is behind a paywall unfortunately.