Investigation of fluid properties and ambient pressure on jet performance for needle-free injections

Needle free jet injections have been used for more than a half century and are attractive for reductions in sharps waste and elimination of needle-stick injuries and cross-contamination. Previously, jet injectors have targeted intramuscular delivery, however recent developments in DNA-based vaccines necessitate intradermal and subcutaneous delivery. This presents a significant challenge because a successful device must consistently achieve a specific delivery depth, while simultaneously addressing the variability in mechanical properties of the skin and the physical properties of drugs.

We attack this problem experimentally (with high-speed video), studying the effect of parameters such as fluid viscosity, rheology and ambient pressure on the jet characteristics such as coherence and speed. We also performed CFD simulations to examine the pressure drop and shear layer development in the orifice and how they might influence the jet characteristics. The simulations compared favourably to the experiments, thus providing us with a tool to development a broader understanding of the fluid flow in jet injection devices.