EPFL researchers develop sound-powered micro-robots

Researchers at the École Polytechnique Fédérale de Lausanne (EPFL) have developed a method to power micro-robots and tiny vehicles using sound waves instead of traditional motors, gears, or batteries. Published in Science Advances, the study from the MicroBioRobotic Systems (MICROBS) Lab utilizes Helmholtz resonance—the same physical principle that occurs when blowing across a bottle neck—to convert acoustic energy into directional thrust.

The technology employs 3D-printed hollow cavities, such as spherical or bell-shaped resonators, that act as mechanical actuators. When exposed to specific sound frequencies, the air inside these cavities oscillates and is expelled as a concentrated jet, creating net propulsion. This approach differs from acoustic levitation by using the sound to drive the device's own internal movement rather than pushing an object from the outside.

Testing included centimeter-scale boats that could be steered by changing sound frequencies to activate different resonators, and microscopic flying drones. These ultra-lightweight aerial prototypes, some weighing only 150 micrograms, used ultrasonic frequencies to achieve lift and rotation. The researchers suggest this method allows for significant miniaturization and simpler, lighter robotic structures for future aeronautics and robotics applications.