Development of Non-Contact Classifying Systems by Use of Acoustic Levitation

Abstract

The phenomenon that bubbles or particles are suspended at the node position of a standing wave of sound is known as acoustic levitation and has recently been applied in the fields of semiconductors, aerospace, and biology [1-3]. By using this phenomenon in this study, a new classification method has been proposed, and a device has been developed to sort objects in accordance with their densities. Unlike the conventional methods as such as centrifugal particle separation or magnetic separation, this method can separate fine particles both of metal and non-metal and without contact easily only using acoustic power. First, we derived the acoustic radiation pressure to be applied to the object from King’s theory, and then we designed and developed a twin-transducer system to apply the required levitation force. The distributions of sound pressure and particle velocity were then visualized. Finally, a series of experiments was conducted to show the capability of classifying the fine abrasive SiO2 particles and fine iron particles (φ = 50 μm).