Noncontact manipulation of particles in air by switching pulse drive of ultrasonic speakers arrayed on a semicylinder

Abstract

Noncontact micromanipulation techniques are necessary for micromachine technology, biotechnology, materials processing, and so on. By using a bolted Langevin transducer and a reflector, one can trap small objects in air at nodes of sound pressure in a standing wave field, but such a technique requires high-voltage drive and careful tuning to achieve resonance. In this study, a large number of small ultrasonic speakers were placed on the inner surface of a semicylinder to form a strong sound field in the focus line. We showed that the pressure node can be moved, and thus the small object, along the focus line simply by switching the driving ultrasonic speakers without using complex electronics. We also showed that the object can be trapped and manipulated even at a duty ratio of 50% in tone burst waves. The above results are discussed by showing the experimental and calculated sound pressure distributions.