Scientists have created a musical "nano-string" that can play itself by generating motion directly from electrical current, without external force.
Just as a guitar string vibrates when it is plucked, the wire vibrates when it is forced into motion by an oscillating voltage. Source: Lancaster University
The device is a carbon nanotube mounted on two metal supports on either end and cooled to 0.02 degrees above absolute zero. The nanotube is three nanometers in diameter and around 100,000 times thinner than an average guitar string. The central area of the wire is free to vibrate and sound a note.
The team, comprised of researchers from Lancaster University and the University of Oxford, passed a current through the device and measured the change in electrical resistance. The wire vibrates when forced into motion by an oscillating voltage. Researchers conducted a second test without a forcing voltage and were surprised to find that the wire could oscillate on its own under the right conditions.
This left the team to wonder: how does the device vibrate on its own?
Dr. Edward Laird of Lancaster University, lead researcher of the study, said, "It took us a while to work out what was causing the vibrations, but we eventually understood. In such a tiny device, it is important that an electrical current consists of individual electrons. The electrons hop one by one onto the wire, each giving it a small push. Usually these pushes are random, but we realized that when you control the parameters just right, they will synchronize and generate an oscillation."
Due to the thinness of the string, the nanotube oscillates at a much higher frequency than a typical guitar string. At 231 million hertz, the resulting sound is far too high for human ears to register, but the team was able to identify it as an A, 21 octaves above the standard guitar's open fifth string.
The new device could be used to amplify tiny forces in novel microscopes or measure the viscosity of exotic quantum fluids. Further testing and development will be done at the physics department of Lancaster University.
A paper on the new device was published in Nature Physics.
