Sound waves power these tiny drones

Engineers recently discovered a way to power tiny drones and robots with something we encounter every day—sound waves. The technology, described in a study published in the journal Science Advances, is based on a phenomenon in physics called Helmholtz resonance, also known as wind throb. Helmholtz resonance occurs when air trapped in a cavity oscillates back and forth in response to airflow. Think of what happens when you blow air across the opening of a glass bottle—that low hu