Design And Characteristics Of Piezoelectric Ultrasonic Transducer For Precise Micromanipulation Of Cell Rupture

Cell membrane piercing technology is an important link of various cell micromanipulation techniques and it significantly affects the survival rate and success rate of cell manipulation.The piezoceramic actuator-based cell piercing technology is a new method developed in recent years.Through the action of the ultrasonic mechanical vibration of the piezoceramic actuator on the cell surface,the zona pellucida or the molecular bonds is broken with small deformation and low damage.However,this kind of piercing technology suffers some problems,such as small vibration amplitude output and significant transverse vibration,limiting its practical application.To solve the mentioned problems,the ultrasonic transducer,which consists of the mechanical concentrator and the piezoceramic actuator,was proposed and the following researches had been performed.(1)Referring to the mechanism of the piezoceramic actuator-based cell piercing technology,the operational frequency range of the ultrasonic transducer was determined.By using the modular design and the electromechanical equivalent method,the electric impedance models of the horn,piezoceramic stack,and back slab were built up,based on which a whole four-terminal network corresponding to the ultrasonic transducer was developed.When combining the FEA method,the structural parameter sensitivity analysis,and the dynamic optimization,we had investigated the influential factors and their laws on the working modes of the transducer,and then determined the key parameters of the transducer,and finally realized the multi-modality inhibition and modal separation.(2)The needle and its holder are the two important functional components of the ultrasonic transducer for the cell piercing.In this research,the needle was regarded as a slender flexible cantilever beam firstly,and then,the influential factors of its transverse vibration caused by the axial vibration of the transducer horn were investigated.The two-point supporting method was proposed to reduce the transverse vibration amplitude.Then two types of structures for the holder were set up and they are embedded installation and external installation,respectively.For each structure,its geometric parameters were then determined based on the modal analysis.(3)To reduce the negative influence of the traditional rigid mounting clamp on the tip vibration amplitude output,and improve the ultrasonic energy transmission efficiency of the transducer,a new type of flexible hinge-based mounting clamp was proposed which combines the compliant hinge with the traditional flange-based mounting clamp.To get an opimal enhancement effect,a systemic method for the mounting clamp was developed,in which the finite element analysis was used to investigate the influences of several key geometric parameters on the modal characteristics of the transducer,the flexibility models of the newly proposed mounting clamp was used to constitute an optimal objective function and the relevant constraint conditions,the particle swarm optimization algorithm was adopted to find the optimal values of these key geometric parameters.(4)A performance test platform for the transducer was built up based on which a series of test experiments were carried out.The test results show that the transducer with the internally installed needle holder has a few parasitic modes near the longitudinal vibration modal of the transducer.The transducer with the newly proposed flexible hinge-based mounting clamp and externally installed holder shows the best comprehensive performance,laying a good foundation for future research.