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Abstract: This paper presents a new method of extracting biologic particles from a mixture of particles. The method is based on the pumping effect in a π-shaped ultrasonic actuator, which has a gap between its two vibrating metal plates. An adhesive tape is placed at a proper position in the gap. Due to the pumping effect which is induced by the sound field in the gap, the particles with smaller mass and radius in the mixture can be pumped up to reach the adhesive tape; while the ones with larger mass cannot. Therefore, the particles with smaller mass and radius can be extracted from the mixture. A theoretical model which can well explain the operation principle and experimental phenomena is developed. By the experimental results and the theoretical analyses based on the model, the validity of the method in extracting small particles from a mixture of solid particles in air is confirmed, and the effects of the actuator’s vibration, adhesive tape height, contents of the mixture and viscosity of fluid on the extraction are clarified. Also, it is theoretically predicted that the method will work under the microgravity condition in air. [Copyright &y& Elsevier]

The temperature field in small piezoelectric vibrators is investigated experimentally. First of all, the effects of the solder points and internal loss of small piezoelectric vibrators on the non-uniformity of the temperature field are investigated. It is found that the solder points increase the temperature of adjacent piezoelectric material, and the non-uniformity of the temperature field increases as the internal loss increases. Then, the placement method of the piezoelectric vibrators on the temperature field is investigated. It is found that the placement method has a remarkable effect on the maximum temperature rise of the piezoelectric vibrators. Finally, the transient temperature field and its effect on the operation of the vibrators are investigated. It is found that the input power of the vibrators may fluctuate greatly during the transient process of the temperature field. [Copyright &y& Elsevier]