How acoustic levitation was scaled beyond a single particle

The article discusses advances in acoustic levitation, a technique that uses high-frequency sound waves to suspend matter in mid-air without physical contact. Acoustic levitation relies on acoustic radiation pressure generated by ultrasonic standing waves, which create regions of high and low pressure that can counteract gravity and hold small objects like droplets, powders, or fragile solids in place. Although the concept dates back to 19th-century experiments, practical levitation of liquid droplets was first demonstrated in the 1930s. Despite its versatility, a major limitation has been the tendency of multiple levitated particles to clump together due to secondary acoustic forces, making precise control of multiple objects difficult. A breakthrough by physicists at the Institute of Science and Technology Austria (ISTA) has overcome this clumping problem by electrically charging the levitated particles. The added electric charge induces electrostatic repulsion between similarly charged particles, counteracting the sound-induced attractive forces that cause them to cluster. This innovation enables stable, simultaneous levitation and independent control of