A group of researchers from Russia ,
Belarus and Spain
The scientists proposed using two nanotubes, one of which is a long
cylinder with double walls one atom thick. These tubes are placed so that their
open ends are opposite to each other. Voltage is then applied to them, and a
current of about 10nAflows through the circuit.
Carbon tube walls are good conductors, and along the gap between the ends
of the nanotubes the current flows thanks to the tunnel effect, which is a
quantum phenomenon where electrons pass through a barrier that is considered
insurmountable in classical mechanics.
This current is called tunneling current and is widely used in practice.
There are, for example, tunnel diodes, wherein current flows through the
potential barrier of the p-n junction.
Another example is a scanning tunneling
microscope (STM), in which the surface of a sample is scanned with a
very sharp needle under voltage. The needle slides along the surface, and the
magnitude of the current flowing through it shows the distance to the sample
with such accuracy that the STM can detect protrusions one atom high.
The authors of the article used the relationship between the tunneling
current and the distance between the ends of the nanotubes to determine the
relative position of the carbon nanotubes and thus to find the magnitude of the
external force exerted on them.
The new sensor allows the position of coaxial cylinders in two-layer
nanotubes to be controlled quite accurately. As a result, it is possible to
determine the stretch of an n-scale object, to which electrodes are attached.
Calculations made by the researchers showed the possibility of recording forces
of a few tenths of a nN(10-10newtons). To make it clearer, a single bacterium
weighs about 10-14newtons on average, and a mosquito weighs a few dozen mcN
(10-5 N).However, the device developed by the physicists may find application
beyond micro scales.
A double-layered coaxial nanotube is akin to a microscopic cylinder with a
sliding piston. Such a system has already been considered by a number of other
researchers as a potential part for various types of nanomachines. Nanotubes
have been proposed for the role of micromanipulators, or connecting
"studs" for complex mechanisms, and they may even be used for data
storage; the position of the inner "piston" may encode one bit of
information or more.
Furthermore, calculations have shown that it is possible to create a
combined device, where inside a two-layer carbon nanotube there will
be magnetic fullerenes. When placed in a magnetic field, a power will emerge,
which could be measured by changes in the magnitude of tunneling current. This
will convert the force sensor into a magnetic field sensor.
没有评论:
发表评论