Scientists have discovered that tiny vibrating devices called nanomechanical resonators can lose energy even when they never touch another object.
The surprising finding could help engineers design better sensors, communication devices and future quantum technologies.
The research, carried out by scientists at the Swiss Federal Institute of Technology Lausanne (EPFL), was published in Nature Physics.
Nanomechanical resonators are extremely small structures built onto computer chips. Although they are tiny, they vibrate very quickly, from thousands to billions of times every second.
Because they are so sensitive, they can detect incredibly small changes in mass, force, pressure and temperature.
They are also used in radio-frequency filters, precise timing devices and advanced quantum physics experiments.
For many of these applications, the resonators must be placed very close to other materials. This allows scientists to measure their motion or connect them with other electronic or optical systems. Until now, researchers knew that direct contact could reduce a resonator’s performance, but the new study shows that simply being nearby can also cause problems.
The researchers found that when a resonator vibrates close to certain insulating materials, it can slowly lose energy without ever touching them. This lowers the device’s performance by reducing what scientists call its “quality factor,” which measures how long the resonator can keep vibrating before it slows down.
The cause of this hidden energy loss is tiny static electric charges trapped inside the resonator. As the device vibrates, these charges create a changing electric field around it. If a nearby insulating material, such as silicon dioxide or silicon nitride, has even a very small amount of electrical loss, it absorbs some of this energy.
In other words, energy quietly leaks from the resonator into the nearby material, even though the two objects never make contact. This effect is related to a phenomenon known as noncontact friction, which has previously been observed in specialized scientific instruments.
The research team first created a mathematical model to predict how this hidden energy loss should behave. Their calculations suggested that slower vibrations would lose more energy than faster ones.
To test the idea, they built tiny silicon nitride resonators suspended only about 500 nanometers above an insulating layer. A nanometer is one billionth of a meter. Their measurements matched the predictions: the lowest-frequency vibrations lost the most energy.
The scientists then carried out a second experiment using even more advanced resonators placed between tiny optical structures separated by gaps only a few hundred nanometers wide. As the gap became smaller, the resonators performed much worse. In some cases, their quality factor dropped by as much as ten times.
The discovery provides important guidance for engineers developing future nanoscale devices. It shows there is a practical limit to how closely different components can be placed without affecting performance.
At the same time, the researchers believe this effect could become a useful tool. By carefully measuring the hidden energy loss, scientists may be able to study the electrical properties of very thin materials or create new ways to connect mechanical devices with electronic systems.
As nanotechnology continues to advance, understanding these invisible energy losses will be essential for building smaller, more sensitive and more reliable devices for science, medicine and future quantum technologies.
