Sound-Powered Propulsion Without Motors

Researchers have engineered a novel method of propulsion that operates entirely without standard mechanical components. Their 3D-printed cavities respond to specific frequencies, producing motion without motors, gears, or magnetic parts.

The fundamental mechanism behind this acoustic movement is grounded in everyday physics. Specifically, the effect is related to what happens when air is blown across the top of a bottle.

To construct these unique propulsion systems, researchers explored various structural materials. Ultimately, the team made the resonators from materials including 3D-printed plastics, rubber-like polymers, and glass.

This acoustic cavity design represents a distinct departure from existing micro-scale airflow solutions. The concept differs from ultrasonic cooling systems such as xMEMS' fan-on-a-chip, which uses a piezoelectric membrane to move air.

Acoustic Testing on Water

To test the capabilities of the acoustic resonators, the engineering team turned to water-based platforms. For one demonstration, the researchers installed up to three resonators on small boats.

These miniature aquatic vessels relied entirely on the directed airflow from the cavities to generate thrust. To ensure the acoustic propulsion was sufficient for movement, the boats were extremely light.

Hovering Microfliers

Following the aquatic demonstrations, the researchers scaled their designs down for airborne applications. The team then used 3D nanoprinting to build microfliers.

These diminutive aircraft required precise engineering to achieve liftoff. One flying design weighed 150 micrograms and used three cavities to produce downward thrust.

Another experimental design utilized rotary mechanics to achieve flight. The blades spun at up to 13,000 rpm, generating enough lift for the device to hover like a tiny helicopter.

While the fundamental propulsion concept was proven successful, the flight distances remained highly constrained during these early trials. The microfliers rose less than 5 millimeters.