Acoustic Tweezers Based On The Principle Of Ultrasonic Standing Wave System Design And Experimental Reasearch

Acoustic tweezers is a technology that uses the mechanical effect of acoustic waves to manipulate tiny objects non-contact,and its physical basis is due to the superposition of ultrasonic waves to form a high-intensity standing wave acoustic field,in which the object and the acoustic waves will undergo momentum and energy conversion,thus generating a force to control the motion of the particles.Ultrasonic manipulation of objects has the advantages of non-contact,good biocompatibility,no need to chemically and biologically label the particles,simple and easy to integrate devices,etc.It has a broad application prospect in precision manufacturing,biochemical analysis,precision medicine,simulation of microgravity environment,etc.,and occupies an important position in the manipulation of tiny objects.In this paper,the relationship between pressure,temperature and volume in an ideal acoustic field is first derived from the law of conservation of mass,the equation of matter and Newton’s second law,and then the fluctuation equation of acoustic waves is derived.On this basis,the expressions for the vibration velocity,sound pressure,time-averaged potential and acoustic radiation force on the medium mass in two different acoustic fields are derived by Gor’kov’s ultrasonic standing wave theory,and the stable position of the object suspended in the acoustic field is analyzed.The single-transducer structure and the double-transducer structure are compared to determine the scheme for levitating and manipulating objects by ultrasonic standing waves.Secondly,the half-wavelength longitudinal vibration sandwich transducer is developed,mainly including the design and optimization of the half-wavelength oscillator and the variable amplitude rod,and the dimensions of each part of the half-wavelength oscillator are determined by theoretical derivation,and the dimensions of each part of the variable amplitude rod are determined by theoretical derivation combined with simulation.Finite element simulation of the transducer modalities is carried out to verify whether the sandwich transducer meets the design requirements.When the transducer is determined to meet the design requirements,the parts are machined and fabricated and assembled into a transducer.Then the finite element simulation analysis of the sound field of the dual transducer is carried out using COMSOL to establish the sound field model,and the distribution of sound pressure,time-averaged potential and acoustic radiation force in the sound field is obtained by simulation to verify the levitation ability of the ultrasonic standing wave sound field on the object.By changing the parameters in the sound field and observing the changes of sound pressure,timeaveraged potential,acoustic radiation force and particle trajectory in the sound field,the feasibility of the method of manipulating the movement of the sphere by changing the phase difference is demonstrated.Finally,the experimental platform of the acoustic tweezer system is built,and firstly,the experiments of levitating the blob with single and double transducers are conducted to compare the levitating stability of the two structures and to obtain the stable levitating position of the blob in the acoustic field.Secondly,the experiments of changing the phase difference to move the sphere at the distance between the radiation surface and the half wavelength of the acoustic wave and one wavelength are carried out to verify the correctness of the method of manipulating the sphere by the ultrasonic standing wave of the double transducer.Finally,the experiments of moving trajectory of the sphere before and after compensation are conducted to verify the effectiveness of the nonlinear compensation method.