Research on Fluid Flow Characteristics and Jet Dynamics for the Needle-free Injection Process

There are different problems with hypodermic needle injections, such as skin induration at the injecting area, difficult to dispose the waste of the injections and needles, and people's desire for needle-free jet injectors is increasing day by day. recently the needle-free jet injectors have been constantly improved, and the injection effect has been widely improved. At present, the most representative needle-free jet injectors in the world were Intraject designed by the British Weston Medical Company and Injex of the American Equidyne company. Baxter and Mitragotri studied the relationship between penetration of the drug into the subcutaneous and jet velocity and diameter of needle-free jet injectors, and the results show that the performance of injection completely depends on the jet diameter and the jet velocity. Needle-free jet injection is a fantastic alternative to conventional injection; it also reduces patients' fear of the needle, anxiety of the needle, and needle injury, reducing the chances of cross-contamination by a considerable number. It is highly appropriate for small doses of medicines, such as insulin and vaccines. The structural design of the needle-free jet injector nozzle determines the performance and properties of nozzle to create the jet, and the optimized nozzle can improve injection performance and penetration. This study used the realizable Laminar flow model to study the effects of different nozzle structural designs and different nozzles diameters on the injection effect. The maximum jet velocity and penetration distance were selected as the primary research parameters. In this research we designed different nozzle structure, with further analysis; simulations were performed to verify the accuracy of the Nozzle jet effects. The simulations are carried out of the three nozzles with different tip diameters, Nozzle with a smaller tip diameter has higher jet velocity and deeper penetration into the air cylinder. The simulation results proved that the nozzle with a smaller tip diameter has the highest jet velocity with higher penetration at 0.1 microsecond. The effect of the nozzle length on peak stagnation pressure is limited and shows no apparent law. At the same time, the impact on the turbulence intensity is evident and can be seen in the simulation results. The longer the nozzle length, the less turbulence intensity in the jet flow. The results show that the simulation results are highly consistent in comparison with other experiments conducted on the needle-free jet injector development, which verifies the accuracy of the CFD model. The results provide ideas for optimizing the nozzle structure of commercial needle-free jet injectors and help realize efficient drug delivery. This complete injection process of fluid can be defined as two phases of penetration and diffusion. The dispersion characteristics of fluid in different phases could be controlled by an effective combination of the different nozzles and different nozzle diameters. Overall, the obtained conclusions provide a provident support for understanding the operation of the needle-free injector. even though some clinical studies have been conducted to understand the mechanism involved in these practices, an extensive study from an engineering point of view has not yet been conducted. Here, we aim to identify the key parameters in the needle-free injection process and study their effects on microjet characteristics.