"Imagine a swing that, once pushed, keeps swinging for almost 100 years because it loses almost no energy through the ropes." So says a Delft University of Technology researcher who has helped his team accomplish a parallel feat at the nanoscale.
In creating their super-vibrational nanostrings, Norte and his fellow TU Delft colleagues – along with scientists from Brown University – stretched out a strand of extremely resilient silicon nitride (Si3N4) to a length of 3 cm (1.2 in) while maintaining it at a thickness of just 70 nanometers. This is "equivalent to reliably producing ceramic structures with a thickness of one millimeter, suspended over nearly half a kilometer," write the researchers in a paper published in Nature Communications.
"Our manufacturing process goes in a different direction with respect to what is possible in nanotechnology today," says study co-author Andrea Cupertino, also from TU Delft.
"These kinds of extreme structures are only feasible at nanoscales where the effects of gravity and weight enter differently," she adds. "This allows for structures that would be unfeasible at our everyday scales but are particularly useful in miniature devices used to measure physical quantities such as pressure, temperature, acceleration and magnetic fields, which we call MEMS sensing."
Once the nanostrings were manufactured, they were clamped above a microchip. The strings were then shown to be able to vibrate 100,000 times per second without losing much momentum at ambient temperatures. Such a feat has previously only been exhibited by materials near absolute zero temperatures.
"The newly developed nanostrings boast the highest mechanical quality factors ever recorded for any clamping object in room temperature environments; in their case clamped to a microchip," says the TU Delft report.
Norte adds that the incredibly vibrational capacity of the nanostrings is due to their structure and composition, which makes it hard for energy to leak out and also hard for environmental noise to get in.
"This innovation is pivotal for studying macroscopic quantum phenomena at room temperature – environments where such phenomena were previously masked by noise," he says. "While the weird laws of quantum mechanics are usually only seen in single atoms, the nanostrings' ability to isolate themselves from our everyday heat-based vibrational noise allows them to open a window into their own quantum signatures; strings made from billions of atoms. In everyday environments, this kind of capability would have interesting uses for quantum-based sensing."
The researchers say their discovery could lead to next-generation microphones and other nanoscale acoustic devices, or could be used to create advanced accelerometers for navigation. High-aspect-ratio mechanical resonators, as the nanowires are called, are also regularly used in precision-sensing equipment such as macroscopic wave detectors.
In their paper the scientists also state that nanostrings bearing the same qualities as those they've created could help in searchers for dark matter, studies of entropy and time, and the understanding of the quantum phenomenon known as the Casimir effect.
Source: TU Delft
