Three-dimensional noncontact manipulation by opposite ultrasonic phased arrays

A three-dimensional acoustic manipulation in air is presented. Two arrays of ultrasonic transducers are arranged opposite each other, generating a localized standing wave at an arbitrary position through the phased-array focusing technique. Small particles are suspended in the nodes of the standing wave and also manipulated according to the position of the standing wave. This paper gives the following principles of the proposed method: the theory of acoustic levitation, the ultrasonic phased array, and the estimation of the radial and axial forces. It was experimentally confirmed that particles of 0.6 mm diameter are trapped in the nodes. The length of the localized standing wave, the suspension endurance, and the size of the work space were investigated. It was also demonstrated that a mass of particles can be scooped up when the localized standing wave moves through the mass. (C) 2014 The Japan Society of Applied Physics