Structure Design And Research Of The Pneumatic Needle-free Injector For An Animal Application

Needle-free injection is a novel subcutaneous delivery technology using high-speed jet to achieve targeted drug injection.While applied to a large-scale animal vaccine injection,the needle-free injection has numerous advantages in terms of high efficiency,reducing animal stress response and reducing the risk of cross infections.In recent years,the needle-free injection system for human use has developed rapidly in China,however,not popular yet for an animal application due to its complex and precise equipment and high price,which restricts the development of stockbreeding on certain level.It is necessary to study and improve structural design of needle-free injectors orientated for animal use.A pneumatic needle-free injector proposed in this thesis is of great significance for avoiding cross infection among animals,improving injection efficiency and increasing economic benefits,which aims to provide a unique platform for such a needle-free injection technology to the animal vaccination.For a mass animal vaccination,key features of a rapid response,easy to use and veterinary injector without a needle are identified as the primary requirements.MATLAB and FLUENT software tools are firstly utilized to design and optimize parts/components of such a delivery system.The optimized parameters are then input for three-dimensional modeling.A prototype device is finally assembled and tested,to evaluate the injection performance.The main research results and findings are summarized as follows:(1)Proposed an overall design scheme of the needle-free injection system according to the principle of needle-free delivery system and practical working requirements.The entire system is divided into three subsystems: mechanical transmission,hydraulic circuit and pneumatic circuit design.The movement mechanism of pre-realized functional components in each subsystem was systematically analyzed,so that the equipment can complete automatic drug loading,rapid injection,differential dose adjustment and other functions if required.(2)According to the needle-free injection process,a physical-mathematical model of the injection system was established.Subsequently the influence of nozzle diameter,ampoule cavity diameter,the diameter of impact plunger rod and injection piston assembly quality on jet injection characteristics and performance was analyzed by using MATLAB software,and the optimal parameters were derived.(3)The parameters of the internal structure of the needle-free injector nozzle for animal use were optimized.Computational fluid dynamics software FLUENT was used to analyze and compare the jet field characteristics generated by the flat-top,cone-straight and cone-straight nozzles.It was shown that the cone-straight nozzle could get better controllable jet with higher speed.By adjusting the cone angle and length-diameter ratio of the straight cone nozzle,the optimum parameters of the needle-free syringe nozzle for animal use were obtained.(4)Specific design and selection of the pre-functional parts,including three-dimensional modeling of the prototype device,sealing design,gas path construction,parts processing and assembly,installation and dynamic testing of the integrated system.(5)A needle-free injection experimental platform was designed and built,and the injection effect of the prototype was evaluated with two experiments of dose reliability and agarose gel injection.