In this work, we proposed and developed an ultrasonic actuator which can be used to separate mixed small solid particles in air. The device consists of an ultrasonic sandwich-type transducer and an aluminum plate which is extended from an end plate of the transducer. The aluminum plate is asymmetrically excited by the transducer, to vibrate flexurally. The transducer operates in the thickness mode and has a resonance frequency of 91.7 kHz. Particle mixtures used in the experiments are obtained by the combination of any two particles among shrimp eggs, glass balls and salt particles. The experiments showed that the glass balls could be separated from a mixture of glass balls and shrimp eggs, and salt particles separated from a mixture of salt particles and shrimp eggs. The device used in the method has no mechanical rotary part and the separation can be quickly completed. (c) 2014 Elsevier B.V. All rights reserved.