# EPFL Engineers Build Sound-Powered Drones Using 3D-Printed Acoustic Resonators **Source:** https://glitchwire.com/news/epfl-engineers-build-sound-powered-drones-using-3d-printed-acoustic-resonators/ **Published:** 2026-08-24T15:14:40.050Z **Author:** Tech Desk ยท Glitchwire **Categories:** Tech, Science ## Summary Swiss researchers have demonstrated a propulsion system that generates thrust from sound waves alone, eliminating motors, gears, and onboard batteries from microscale flying machines. ## Article Engineers at the Swiss Federal Institute of Technology Lausanne (EPFL) have demonstrated a propulsion concept that reads like it belongs in a physics thought experiment. The system uses 3D-printed acoustic resonators to convert sound at specific frequencies into directed air jets, generating enough thrust to fly ultralight structures without motors, gears, or onboard power. The research, [published in Science Advances](https://www.science.org/doi/10.1126/sciadv.aef5620), exploits Helmholtz resonance. That's the same acoustic principle that produces a tone when you blow across a bottle opening. When external sound matches a cavity's resonant frequency, the air inside begins to oscillate strongly. The EPFL team shaped hollow chambers so that oscillating air escapes through a small opening as a concentrated jet, while incoming airflow spreads more diffusely. That asymmetry generates thrust. ## How It Works The researchers, led by PhD student Junsun Hwang and lab head Selman Sakar, built devices at two scales. At the centimeter level, they installed resonators on small boats, each tuned to a different audible frequency. Changing the sound frequency from an external speaker activated individual cavities, allowing the team to steer the craft around obstacles. One boat successfully traced the letters "EPFL" while responding to Bluetooth commands with latency around 30 milliseconds. The flying variants proved more striking. Using 3D nanoprinting, the team built microfliers with three microscopic resonant cavities integrated into polymer structures. One design weighing roughly 150 micrograms operated at 40 kilohertz, using ultrasound to generate direct upward thrust like a rocket. A second design arranged three blades around a central point, each blade housing a resonator that produced thrust at the correct frequency. Those blades spun at speeds exceeding 12,000 rpm, generating helicopter-style aerodynamic lift. The ultrasonic frequencies powering the fliers are inaudible to humans, meaning the devices operate in silence. "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," Sakar said in EPFL's announcement. ## Severe Limitations Remain The technology is nowhere near practical deployment. Current prototypes achieved less than 5 millimeters of lift. They carry virtually no payload. And they require an external acoustic energy source, meaning the microfliers only function within range of an ultrasonic phased array. The boats were extremely light, suitable only for laboratory demonstrations. One version did generate nearly five times its own weight in thrust, but that weight measured in micrograms. Scaling this approach to carry useful payloads presents formidable engineering challenges. ## Why It Matters Anyway The significance lies in what the concept eliminates. Batteries add mass that drags down flight performance. Motors introduce mechanical friction and wear. Complex electronics break down when miniaturized to microscopic scales. Acoustic cavities sidestep all of these constraints. The resonators can be manufactured from common 3D-printing plastics, flexible polymers, or glass. If scaled and commercialized, sound-powered propulsion could enable applications where conventional power systems fail. Medical devices navigating inside the human body might draw energy from external ultrasound rather than carrying batteries. Environmental sensors could operate in hazardous locations, powered remotely. Space missions might deploy extremely lightweight probes that receive propulsive energy from a larger craft. Sakar's lab envisions building multiple sound-responsive structures into single flexible devices, each reacting to different frequencies. Such devices could change shape in response to sound, enabling what he calls "aerodynamic robotic devices that can change shape in response to sound." None of this is imminent. The EPFL work establishes feasibility, not practicality. What the team has proven is that resonant cavities can serve as viable propulsion systems at microscopic scales, a foundation that future research can build upon. Whether that foundation supports anything beyond laboratory demonstrations will depend on breakthroughs in acoustic power transmission and cavity efficiency that haven't happened yet. --- **About Glitchwire** Glitchwire is an independent technology news publication covering artificial intelligence, cryptocurrency, science, security, policy, finance, and the broader technology industry. 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