Noncontact rotation of a small object using an asymmetric ultrasonic field

Abstract

Noncontact manipulation techniques using airborne high-intensity ultrasound can be applied in various industrial fields such as pharmaceutical industry and future space industry. This paper discusses a method to rotate a small object in the air without physical contact using ultrasound. The experimental system consists of a vibrating disc with four bolt-clamped Langevin-type ultrasound transducers and two semicircular reflectors. The flexural vibration of the disc generates an acoustic standing wave between them, and a small object can be levitated at the nodal position. By inclining one of the two reflectors, an asymmetric acoustic field and an acoustic traveling wave in the circumferential direction are generated where the object can be rotated in the clockwise or counterclockwise direction. Vector flows of the acoustic intensity in the air between the vibrator and reflectors were calculated. When the tilt angle of the reflector was 0.32°, the object was rotated without contact, and the rotation direction corresponded with the direction of the vector flows of the acoustic intensity. A greater input current gave a greater rotation speed; the maximum rotation speed of the object was 6.84 rps in the case of 1.14 A.