Scientists at ETH Zurich have developed an ultra-thin silicon material that can guide vibrations along carefully designed paths, much like roads directing traffic.
The breakthrough could lead to new technologies for energy harvesting, advanced sensors, and even future computers that work without electricity.
The new material belongs to a class known as metamaterials.
While metamaterials may look ordinary from the outside, they contain specially designed microscopic structures that give them unusual properties.
By carefully arranging these tiny structures, scientists can create materials that behave in ways not found in nature.
Researchers led by Professor Dennis Kochmann have created a new type of metamaterial called a phononic metamaterial.
This material is designed to control mechanical waves, including vibrations and sound waves, with remarkable precision.
To build it, the team started with an extremely thin silicon membrane. Using techniques commonly employed in chip manufacturing, they etched a complex pattern of microscopic holes into the silicon.
The finished design contains hundreds of thousands of tiny repeating structures, each only a few micrometers wide—far too small to see clearly with the naked eye.
The microscopic pattern is not uniform. Instead, it changes gradually across the material. These carefully designed variations allow vibrations to travel along specific routes rather than spreading in all directions.
Normally, when an object vibrates, the resulting waves spread outward much like ripples in a pond. In the new material, however, vibrations can be directed to follow predetermined pathways. In some tests, the researchers even guided vibrations along a figure-eight-shaped route.
Designing such a complex system required advanced computer modeling. Simulating every detail of the wave motion would have required enormous computing power, so the researchers developed custom models to predict how the waves would move through the intricate structure.
After designing the patterns on a computer, the team manufactured the material in a cleanroom facility at ETH Zurich and IBM. They then tested it by firing laser pulses at the silicon membrane to generate vibrations. Using an optical measurement system, they tracked the movement of the waves in real time.
The experiments confirmed that the vibrations followed the intended paths exactly as predicted.
One surprising discovery was that the material worked across a much wider range of frequencies than expected. Although it was designed for vibrations at 750 kilohertz, it performed effectively from about 250 to 800 kilohertz. This flexibility could make the technology useful in a variety of applications.
Because silicon naturally allows vibrations to travel long distances without losing much energy, the material performs better than many plastic-based structures that quickly dampen vibrations.
The researchers believe the technology could eventually be used to control vibrations on computer chips, create sensors that operate without a power source, or harvest energy from environmental vibrations. Such devices could generate electricity from movement and vibrations that would otherwise go to waste.
For now, the team is focused on understanding the physics behind the material’s unusual behavior. They also hope to make the structures even smaller in future studies.
While practical applications may still be years away, the discovery opens exciting possibilities for controlling mechanical waves in ways that were previously impossible.
