These tiny drones are powered by sound

Researchers at EPFL’s MicroBioRobotic Systems (MICROBS) Lab have harnessed Helmholtz resonance to build hollow structures that act as miniature, sound-powered machines, according to a study published in Science Advances. The work demonstrates a new way to convert acoustic energy into directional thrust, potentially enabling tiny drones and other micro-robots to move without onboard power sources.

Helmholtz resonance occurs when airflow across an opening causes air trapped inside a cavity to oscillate, producing a humming sound. The EPFL team applied this principle to fabricate hollow round or bell-shaped cavities. When sound waves excite the air inside these cavities, the oscillating air is forced out as a concentrated jet, while incoming airflow is more diffuse. This imbalance generates thrust that can propel the devices.

“Instead of pushing devices around with sound waves, we have created acoustic resonators that are tuned to harness sound at specific frequencies to generate directional thrust and controlled motion,” says lab head Selman Sakar.

The team demonstrated miniature boats and microfliers that use this mechanism. While previous approaches used sound waves to levitate passive objects, these devices convert sound into their own propulsive force. The innovation shows the feasibility of transforming a simple, cleverly designed mechanical piece into robotic matter.

Source: Robohub