Enlargement of floator size in ultrasonic suspension by arranging the shape of vibrating surface

In near-field acoustic levitation, an object can be levitated vertically upward above vibrating surface of an ultrasonic transducer. On the other hand, it has been reported that an object can be suspended vertically downward under the vibrating surface in the air. We call this phenomenon ultrasonic suspension. When an object is suspended, there is restoring force, which attracts the object to the center of the vibrating surface. By using ultrasonic suspension in handling objects, we have some merits such as non-contact, easy release, material independence, possibility of approaching from above the object and so on. In previous research, the attractive force acting on the object has been measured under the ultrasonic suspension. According to measurement results, it was found that by enlarging the size of facing area of vibrating surface and floator, the actuation force was not the larger attractive force but the repulsive force. In this paper, arrangement of the shape of vibrating surface is discussed and method for enlargement of the size of the floator is proposed.