A Study Of Piezo-driven Ultrasonic Injector For Cell Micro-injection

With the rapid development of biotechnology, micro-injection has become an important method in cell engineering like reproductive technologies. Cell membrane-breaking technique is crucial in micro-injection. By penetrating cells with micro-pipette, this operation is widely used in exogenous gene injection and nuclear transfer. Commonly used method, based on the membrane puncture can cause damage to cells during the penetration procedure. The disadvantage includes low vitality and survival rate of cells in micro-injection. Current, researches on cell membrane-breaking techniques mainly focused on the shape, diameter, micro-injection force, and micro-injection kinetic parameters of injection pipette as well as environmental factors. Although these can increase the cell vitality and survival rate to some degree, large cell deformation is still inevitable and the improvement of the survival rate is not apparent. Therefore, a new minimally invasive cell membrane-breaking method for cell injection is still needed.With the advantage of slight damage to cells and high survival rate of injection, the piezoelectric membrane-breaking injection method has been widely used in the cell micro-injection. However, the traditional piezoelectric injection device still cannot solve the problems like harmful vibration and operation complexity. Therefore, a new design method of piezo-driven ultrasonic injector is proposed in this article, which could reduce harmful lateral tip oscillations of injection pipette substantially. The research contents are as follows:Firstly, a review on the research of piezoelectric injection methods was presented. The piezoelectric ultrasonic membrane-breaking principle was analyzed and summarized. Based on the characteristics of ultrasonic technology, the principle of ultrasonic injection and cutting were investigated, and the optimal ultrasonic membrane-breaking parameters were also determined. All these studies provides theoretical framework for the design of the piezo-driven cell injector system.Secondly, the ultrasonic vibration generator was developed, and then the principle of piezoelectric ceramic and vibration are characterized for a better selection of piezoelectric ceramic. The piezoelectric ceramic packaging method and installation form of piezo-driven injector were designed. Finally, a test experiment was designed, which demonstrated the stability and reliability of the proposed packaging design.Thirdly, on the basis of traditional injection device, the single point for fixing structure, two points for fixing structure and nozzle type structure were proposed. By using ANSYS software to conduct modeling and harmonic response analysis on the above three designs. In addition, the transverse vibration situation of injection pipette under different frequencies was simulated, and based on which, the initial configuration of the two points for fixing injection needle was established. After the structure dimension and the best processing parameters were analyzed, the piezo-driven cell injector was finally worked out.Fourthly, by the design of the drive and control system of piezoelectric ceramic, the vibration frequency and amplitude of piezo-driven cell injector could be adjusted freely, and the stability and practicability of system verified. Then, an observation testbed was setup to obtain the vibration amplitude of the injection pipette by marking the designed piezoelectric ultrasonic injector. And then, by testing transverse vibration displacement of injection pipette in air and liquid respectively, a deviation contrast curve could be achieved. After testing, the newly-designed injector can significantly reduce the transverse displacement caused by vibration, and the surroundings of injection pipette can significantly affect its transverse vibration amplitude.Finally, egg cell of mice injection experiments were performed with our designed NKTY-MR601 micro-manipulator system. After comparative tests, the optimal membrane puncture parameters was obtained(frequency 21 k Hz, amplitude 20V), and the rationality and practicality of piezo-driven ultrasonic cell injector design was validated, which could meet the requirements of micro-injection on cell micro-damage, and improve the success rate of cell injection(84%).