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By Biocat

A team led by professor Adrian Bachtold of the Catalan Institute of Nanotechnology (ICN), has fabricated and tested the world’s most sensitive nanomechanical sensor, capable of detecting changes in mass of 1.7 yoctograms, roughly the mass of one proton. Their work has been published in Nature Nanotechnology.

The sensor is akin to a guitar string that vibrates at a very high frequency (around 2 GHz): by comparing the resonating frequency of the nanotube before and after some additional mass has bound to the nanotube’s surface, the can quantify the added mass.

After constructing the sensor, which comprises a 150 nanometre-long carbon nanotube that spans a trench of similar length, the team conducted several mass-detection and binding experiments. For example, they measured the rate at which naphthalene molecules adsorb onto the nanotube surface, and determined that adsorption of xenon atoms onto the surface is a thermally activated process.

Not only did these experiments require an exceptional level of control to obtain a sufficiently clean nanotube—achieved by annealing it with an electrical current—they also required extremely low temperatures (-269 ?C), ultra-high vacuum (10-14 bar), and an environment completely free of mechanical disruption or electrical noise. 

Bachtold and his team did not confine the binding to any specific area of the nanotube. However, in future work, they will endeavour to create a single “trapping site” on the nanotube, which should enable improved mass measurements—namely, by reducing fluctuations in the nanotube’s resonance frequency.

The newly developed nanomechanical mass sensor may have major implications in fields such as mass spectrometry, magnetometry, nanometrology and surface science.

A Nanomechanical Mass Sensor with Yoctogram Resolution (J. Chaste, A. Eichler, J. Moser, G. Ceballos, R. Rurali and A. Bachtold. Doi:10.1038/nnano.2012.42). 

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