Research On The Key Structural Design Of Ultrasonic Transducer For Cell Membrane Micromanipulatio

Cell membrane breaking is an important part of cell micromanipulation techniques,and the quality of membrane breaking depends on the micromanipulation tools used for cell membrane breaking.Cell membrane breaking based on the ultrasonic vibration created by the piezoceramic stack is a new technology that has emerged in recent years.However,this technique suffers from the problems of insufficient vibration amplitude out and excessive transverse vibration.To solve the above problems,a new type of membrane-breaking device was designed which combines the piezoceramic material and mechanical concentrator to constitute an ultrasonic transducer.A series of researches were then carried out which are about the design,analysis,and test of the proposed ultrasonic transducer.(1)Relying on the principle of the cell membrane breaking based on the piezoelectric ultrasonic transducer,the required operating frequency and output amplitude of the transducer for membrane breaking were determined.According to the electromechanical equivalent circuit method and fluctuation equation,the electrical impedance models of key components,such as piezoceramic oscillator and ultrasonic horn in the ultrasonic transducer,were established through the modular design idea,and then the geometric parameters of each structural unit are initially calculated.the finite element model of the transducer is established.Based on the finite element model of the ultrasonic transducer,the structural parameter sensitivity analysis and modal frequency sensitivity analysis are comprehensively applied to analyze the transducer’s vibration pattern,longitudinal vibration displacement distribution.The relationships between the different mode types of the ultrasonic transducer and the main structural parameters were revealed,and the separation of axial modes and the suppression of non-axial parasitic modes are realized.(2)To reduce the external disturbance moment introduced by the mounting clamp,increase the energy transfer efficiency,and reduce the shift of resonant frequency,three flexible mounting clamps,which combine the traditional mounting clamp with the flexible hinge and can support the revolute or the translational motion,were proposed.Based on the design theory of flexible mechanism and finite element modal analysis,the flexibility models of the newly proposed mounting clamps were established,and their flexibility,deformation capability,and motion decoupling capability were comprehensively evaluated.(3)The factors influencing the lateral vibration of the injection needle,together with the relevant laws,are investigated based on the theories of flexibility and structural dynamics.Firstly,the optimum length of the injection needle was determined using finite element analysis.Next,a needle-holding structure was designed to connect the transducer and the needle for membrane-breaking.In the needle-holder,a pair of rubber rings were arranged at different positions to tightly clamp the needle,reducing the vibration output in the transverse direction as much as possible,and ensuring a better vibration energy transfer efficiency.Finally,modal analysis and evaluation of the ultrasonic transducer assembled with a needle-holder were carried out.(4)An ultrasonic transducer vibration test system was built and four different types of ultrasonic transducers with different clamping flanges were fabricated.Firstly,the influential rules of the mechanical compliance of the mounting clamps on the electrical properties and the vibration responses of the transducer were investigated,and then the impedance analyses and a series of excitation experiments were carried out to examine the practical performance of the ultrasonic transducer assembled the needle-holder and the needle.