Acoustic Levitation for Large Particle Based on Concave Spherical Transducer Arrays

Abstract

With the advantages of non-contact, compatibility, no chemical effect and safety, acoustic levitation of object has great potential to apply in chemistry, biology, medicine field and micro robots. Suspension to large particle higher than the half wavelength( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.5\lambda $ </tex-math></inline-formula> ) of sound wave, is a challenge technology in micro-nanoscale manipulation. An increased large quantity probes, double sided and four sided phased array with virtual vortex can provide higher capture power, control ability and stability of particle fixation and the manipulation. However, for a limited confined space, the additional probes and sided phased array emission and receiving device is hard to be established and applied. Additional probes and sided ultrasonic phased array requires higher processing ability of MCU (Micro Control Unit) and the quantities of transducers. Further, multiparticles suspension is rare to be reported. In this study, a relatively simple suspension device of one sided concave spherical transducer array is designed, aiming to levitate a large particle and multi-particles. Based on the one sided acoustic field simulation of ultrasonic array, the optimized structure of open spherical sector (OSS) is constructed to establish levitation device. Experimental platform integrating FPGA controller, amplifier and impedance matching is developed to drive the transducer arrays, where a polystyrene particle with 6 mm ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.71\lambda $ </tex-math></inline-formula> ) diameter is successfully levitated. The virtual twin trap sound pressure of transducer array is measured to evaluate the particle stability. Experiments demonstrate the correctness of virtual twin trap acoustic field analysis, the feasibility in the manipulation to the large particle and multi-particles by acoustic trap.