Scientists Develop Force Sensor from Carbon Nanotubes
A group of researchers from Russia, Belarus and Spain, including Moscow Institute of Physics and Technology professor Yury Lozovik, have developed a microscopic force sensor based on carbon nanotubes. 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. The researchers 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.