Elucidation of injection behavior into skin-simulating soft materials using an impact-induced liquid jet

The needle-free injection has attracted attention as an alternative technique to the needle injection. Laser-induced jets are expected to have a thin jet tip and cause less pain and have attracted attention as a minimally invasive needle-free injection technique. However, there are still some concerns including the large size of the laser equipment. To overcome the disadvantage of laser-induced liquid jets for needle-free injectors, we developed a high-speed focused liquid jet mechanism driven by an impact, which is called the impact-induced liquid jet mechanism. This mechanism is smaller than a laser-induced focused liquid jet. Injection experiments into soft materials simulating human tissues succeeded using the impact-induced liquid jet mechanism and it was confirmed that the injection depth was found to be explained by the Reynolds number and Elastic Froude number (the ratio between elasticity and inertia) by varying liquid viscosity, liquid jet diameter, jet velocity, and soft material hardness. Based on these results, The injection phenomena of a focused liquid jet by an impact-induced liquid jet mechanism can be evaluated using drugs with different viscosities and skin of different hardness for needle-free injection.