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Like a guitar string,
a carbon nanotube(1) can resonate. In the same way that
the pitch of a guitar string can be modified by modifying the tension
of the string, a team of researchers has managed to adjust the resonance
frequencies of nanotubes by applying a voltage. “It amounts
to tuning a nano-guitar,” sums up Stephen Purcell from the
Materials Physics Department (CNRS - Université Lyon 1), co-author
of the work to be published this week in Physical Review Letters(2).
“Imagine you have thousands of similar nanotubes”,
suggests Stephen Purcell. “Inevitably, they do not all have
the same length or the same diameter. Their resonance frequencies are
therefore different. With our method, it is nevertheless possible to make
them resonate together: it is necessary merely to apply the right voltage
to each nanotube”.
The frequency adjustment is achieved by the electric force generated at
the end of the nanotube. It is thus possible to cause the frequency to
vary by a factor of 10. “The analogy with a nano-guitar is natural.
The physics is the same as when a string instrument is tuned by modifying
the tension on its strings”, explains the researcher.
The article which is being published in Physical Review Letters
also describes a novel method of observing the excitation of the mechanical
resonances of carbon nanotubes. That method should be very useful to other
researchers in the same field. By merely adding a function generator to
their apparatus, they will be able to study the mechanical properties
of their nanotubes as a function of the treatments they apply, or of temperature.
For Stephen Purcell, the possibility of acting over a wide range of frequencies
by using electronics constitutes a powerful new tool in the field of nanotechnologies.
(1)With
diameters of about one nanometer (10-9 meters), carbon nanotubes are ten
times stiffer and six times lighter than steel.
(2)“Tuning of Nanotube Mechanical Resonances
by Electric Field Pulling.”
Authors: S.T. Purcell, P. Vincent, C. Journet, Vu Thien Binh.
Web Site of Physical Review Letters: http://prl.aps.org/
("Recent and Future Issues" section).
The article
is scheduled to be published in that journal in the coming weeks.
Researcher
contact:
S.T. Purcell
Tel: +33 4 72 44 80 48
e-mail: purcell@dpm.univ-lyon1.fr
Press contact:
Nathalie Tramunt
Tel: +33 1 44 96 46 06
e-mail: nathalie.tramunt@cnrs-dir.fr
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