Linearly Convergent Aerial Ultrasonic Source Providing a Variable Incident Angle and Acoustic Radiation Force by Standing-Wave Ultrasonic Field

We consider a method of retaining a very small solid or liquid object within a specific long and narrow region in a noncontact manner using an acoustic radiation force acting on the object. To realize this method, we intended to use a linearly convergent sound source (at 20 kHz) equipped with a conventional stripe-mode vibration plate. However, it is difficult for the sound field formed by this sound source to provide a good acoustic radiation force. To improve this sound source, therefore, we combined it with a new emission direction converter that can emit a convergent sound wave at a variable incident angle onto a focusing point. In addition, we proved that the sound source produced in the experiment could form a standing-wave sound field that provides a good acoustic radiation force. Then, we determined the acoustic radiation force provided by the sound field thus formed, and proved that the sound source was effective for forming the desired standing-wave sound field.