Exotic behavior when mechanical devices reach the nanoscale

May 15, 2011, Institut Català de Nanotecnologia

Most mechanical resonators damp (slow down) in a well-understood linear manner, but ground-breaking work by Prof. Adrian Bachtold and his research group at the Catalan Institute of Nanotechnology has shown that resonators formed from nanoscale graphene and carbon nanotubes exhibit nonlinear damping, opening up exciting possibilities for super-sensitive detectors of force or mass.

In an article to be published in Nature , Prof. Bachtold and his co-researchers describe how they formed nano-scale resonators by suspending tiny graphene sheets or carbon nanotubes and clamping them at each end. These devices, similar to guitar strings, can be set to vibrate at very specific frequencies.

In all mechanical resonators studied to date, from large objects several metres in size down to tiny components just a few tens of in length, has always been observed to occur in a highly predictable, linear manner. However Prof. Bachtold´s research demonstrates that this linear damping paradigm breaks down for resonators with critical dimensions on the atomic scale. Of particular importance they have shown that the damping is strongly nonlinear for resonators based on nanotubes and graphene, a characteristic that facilitates amplification of signals and dramatic improvements in sensitivity.

The finding has profound consequences. Damping is central to the physics of nanoelectromechanical resonators, lying at the core of quantum and sensing experiments. Therefore many predictions that have been made for nanoscale electro-mechanical devices now need to be revisited when considering nanotube and graphene resonators.

This new insight into the dynamics of nano-scale resonators will also enable dramatic improvements in the performance of numerous devices. Already the Prof. Bachtold´s group has achieved a new record in quality factor for graphene resonators and ultra-weak force sensing with a nanotube resonator.

The work is particularly timely because an increasing number of research groups around the world with diverse backgrounds are choosing to study nanotube/ resonators, which have a number of uniquely useful properties.

Explore further: How long does a tuning fork ring? 'Quantum-mechanics' solve a very classical problem

More information: Paper online: DOI:10.1038/NNANO.2011.71

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4 / 5 (1) May 16, 2011
With any (strong) nonlinear effect you can create a transistor equivalent.

A nanoelectromechanical transistor would be a neat trick.
not rated yet May 18, 2011
This isn't surprising to me.

All of the major force laws, radiation propagation, and conversion laws end up being either quadratic or hyperbolic with respect to distance or some other property.

Quadratic is derived from the surface area of of an expanding sphere. Hyperbolic is derived from the reciprocal of a quadratic.

Solar Flux
Nuclear forces
Kinetic Energy
lots of other derived measures or force interactions
relativistic equations

At macroscopic scales these interactions may only appear to be linear perhaps due to the non-linear components somehow canceling out. An example would be destructive interference of wave crests offset by a half wavelength. Given random wave distributions, and if all the waves are of similar amplitude and period, then we could expect non-linear wave components to cancel one another out on average as seen collectively, but when viewed individually each wave has the non-linear characteristics.
not rated yet May 18, 2011
A nanoelectromechanical transistor would be a neat trick.

And they have already been made. I can not recall the title of the article or anything but i am sure it was on physorg.

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