Ultrasonic jets propel silent 3D-printed drone fliers

</>

The future of flight isn’t going to be driven by bulky motors or brute force; it’s going to be powered by whispers and resonance. A brilliant team at Switzerland’s École Polytechnique Fédérale de Lausanne (EPFL) has just unlocked a revolutionary method for propulsion, pioneering what they call a “sound-powered engine.” This isn’t science fiction; it is the reality of harnessing sound waves to generate directional thrust and controlled motion in the world of miniature robotics.

The breakthrough stems from manipulating the air itself. Researchers developed acoustic resonators—specially designed cavities—tuned to specific frequencies. When these cavities resonate, they energize the air within them, pushing out a concentrated jet as controlled thrust. Instead of merely using sound as a tool to push objects around, the team has created devices that literally transform a simple mechanical piece into robot matter by leveraging the physics of vibration.

“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,” explained Selman Sakar, head of the MICROBS laboratory. This work proves the feasibility of transforming carefully designed mechanical structures into self-propelled entities using sound energy.

The practical applications of this acoustically driven technology are astonishing. The team has successfully demonstrated three distinct uses for their sound-powered engine. First, they applied the principle to watercraft, creating a boat that used multiple resonators to achieve propulsion and navigation simultaneously.

More mind-bogglingly, they have engineered tiny flying machines powered by ultrasonic frequencies. One design featured three cavities facing downward, allowing it to lift off the ground like a miniature rocket. Another innovation involved microfliers with rotors that achieved incredible rotational speeds of over 12,000 rpm simply by resonating against precisely tuned cavities. Because these systems operate on ultrasonic frequencies—inaudible to humans—the resulting flight is practically noiseless.

While the initial experiments show limitations in size, with one flier reaching less than five millimeters in altitude, the fundamental concept has been proven. This development represents a seismic shift in how we think about micro-robotics and propulsion systems. The next logical step is scaling this technology up to carry significant payload, opening the door for propulsion systems capable of powering future micro-drones, potentially revolutionizing applications ranging from advanced surveillance to sophisticated military robotics.