Actuation Force Characteristics of Non-contact Ultrasonic Suspension Mechanism for Minute Object (2nd Report)

Abstract

In near-field 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. However, there is no detailed explanation about this phenomenon yet. Following pressure distribution measurement for the suspension gap is requested for the explanation. Previously, such measurement was tried with a sensor with a small hole in a board and a sensor behind it. Results meeting with the phenomenon were not acquired, because of influence of the hole at measuring point. In this research, novel sensor without the hole was proposed and consisted of a small diaphragm to measure local pressure. But, the fabricated sensor could not work due to diaphragm vibration, when the gap between the vibration surface and the measuring surface was one hundred micrometer or less. To overcome the vibration problem, a mass was attached to the diaphragm and could suppress the vibration. Pressure distribution of ultrasonic suspension gap was successfully measured.