EPFL creates battery-less micro-drones powered by sound waves

Researchers at EPFL's MICROBS Lab have developed a new class of micro-drones and robots propelled entirely by sound waves, eliminating the need for onboard batteries or motors. By utilizing 3D-printed hollow cavities, the team created devices capable of hovering or shooting upward using ultrasonic frequencies.

The propulsion system relies on Helmholtz resonance, a phenomenon where sound waves energize air within spheroid or bell-shaped cavities to create concentrated jets of air. These jets generate the thrust necessary for movement. To achieve this, the team employed 3D printing and 3D nanoprinting to fabricate the devices from materials including glass, plastics, and rubbery polymers.

Among the prototypes, one design weighing just 150 micrograms can shoot straight up like a rocket. Another variation featuring blades can spin at 13,000 rpm to generate aerodynamic lift and hover. Beyond aerial flight, the researchers developed centimeter-scale boats equipped with up to three cavities. These boats are tuned to different audible frequencies, allowing for autonomous navigation.

Overcoming the Weight Barrier

Traditional micro-robotics have long been hindered by the physical constraints of power sources. As robots shrink, the weight and volume of batteries and motors become disproportionately large, limiting the potential for true miniaturization. While acoustic actuation has previously been used to manipulate particles in liquids, applying the same principle to air is significantly more difficult due to the lower density of the medium.

The EPFL team solved this by creating specialized resonators that transform ambient or directed sound vibrations into directional thrust. This shift allows the robots to be controlled wirelessly from a distance without carrying any internal power supply.

The Rise of Robotic Matter

This breakthrough suggests a future where robotics move beyond discrete machines and toward "robotic matter." The goal is to transform a simple piece of material into a functional robotic system. By removing the battery, these devices can be made completely silent and significantly smaller than current micro-bots.

Such technology could revolutionize fields where traditional power sources are impractical, including environmental monitoring, surveillance, and medical micro-bots. Because the system is based on the geometry of the resonator rather than complex circuitry, it allows for extreme scalability.

Future Scaling

As the team looks toward further miniaturization, the focus remains on pushing the boundaries of aeronautics and robotics. The concept is compatible with even smaller designs, and future developments will likely explore more complex autonomous behaviors and the integration of these sound-powered actuators into larger, adaptive materials.