In-vitro studies of jet injections.

In this study, needle-free jet injection dynamics were studied using homogeneous gelatin as model substrates. Whilst keeping nozzle properties such as orifice diameter (do) and ampoule volume (V) constant, we demonstrate the effect of standoff (s), confinement around the gel, storage modulus (G') of model gel and liquid viscosity (μ) on the penetration depth of the jet injection. High-speed imaging was used to observe the liquid jet propagation and dispersion dynamics, whilst a load cell was implemented to measure the impact force for different standoff distance and viscosity of the liquid. The different parameters considered showed significant effects on penetration depth, with non-linear dependence on standoff being the key result, which may have implications for future injector designs. Moreover, the effect of confinement serves as a caution of using gelatin substrates as a proxy for human tissue.