Liquid jet injectors are biomedical devices used for drug delivery without the use of hypodermic needles. These devices generate a high-speed small-diameter liquid jet of sufficient pressure to penetrate the skin and deliver an appropriate amount of medication. In this study, a detailed investigation on needle-free liquid injection systems powered by compressed air is carried out.Experiments are conducted using a custom-built experimental prototype which makes it possible to vary a number of parameters. The experimental results are used to validate a fluid mechanics model for air-powered needle-free injectors. The model, based on the work of Baker and Sanders

A liquid jet injector is a biomedical device intended for drug delivery. Medication is delivered through a fluid stream that penetrates the skin. This small diameter liquid stream is created by a piston forcing a fluid column through a nozzle. These devices can be powered by springs or compressed gas. In this study, a CFD simulation is carried out to investigate the fluid mechanics and performance of needle free injectors powered specifically by compressed air. The motion of the internal mechanisms of the injector which propels a liquid jet through an orifice is simulated by the moving boundary method and the fluid dynamics is modeled using LES/VOF techniques. In this paper, numerical results are discussed by comparing the fluid stagnation pressures of the liquid jet with previously published experimental measurements obtained using a custom-built prototype of the air-powered needle free liquid injector. Performance plots as a function of various injector parameters are presented and explained.

The advent of new drug therapies has resulted in a need for drug delivery that can deal with increased drug concentration and viscosities. Needle-free liquid jet injection has shown great potential as a platform for administering some of these revolutionary therapies. This investigation explores the detonative combustion phenomenon in gases as a simple and efficient means of powering needle-free liquid jet injection systems. A preliminary, large-scale prototype injector was designed and developed. In contrast with the widely used air-powered and electrical driven needle-free injectors, the proposed detonation-driven mechanism provides equivalent liquid jet evolution and performance but can efficiently provide a controllable power source an order magnitude higher in strength by varying combustible mixtures and initial conditions. The simplicity and power output associated with this concept aid in improving current needle-free liquid injector design, especially for delivery of high volume, high viscosity drugs, including monoclonal antibodies, which target precise locations in skin tissue.

In this study, an experimental investigation is carried out to further study the critical tube diameter problem for the transmission of gaseous detonation from a confined tube into a sudden open space in both regular mixtures, those highly diluted with argon and irregular mixtures of which the cellular detonation is highly unstable. The two commonly postulated modes of failure consisting of one by a local failure mechanism that is linked to the effect of instabilities for undiluted mixtures, and the other due to the excessive curvature of the global front in mixtures highly diluted with argon, are further investigated through experiments. To discern between these mechanisms in the different mixtures, flow perturbations are imposed by placing a minute obstacle with small blockage ratio at the tube exit diameter just before the detonation diffraction. Results show that the perturbation only has an effect in undiluted mixtures resulting in the decrease of the critical pressure for successful detonation transmission. In other words, the flow fluctuation caused by the small obstacle produces transmission and this result seems to indicate that local hydrodynamic instabilities are significant for the detonation diffraction in undiluted unstable mixtures. On the other hand, the results appear to be the same for both unperturbed and perturbed cases in highly argon diluted mixtures. The small blockage only produces flow fluctuations and does not substantially influence the global curvature of the

An experimental study was performed using a custom-built air-powered needle-free injector to investigate the various injector parameters governing the dynamics of jet injection. A parametric study using five different nozzle sizes at driver pressure ranging from 4 to 8 bar was carried out. The fluid stagnation pressure of the liquid jet was determined using a Honeywell force sensor. Performance plots as a function of various parameters were constructed. It was determined that as the driver pressure increased both the peak and average stagnation pressure increased almost linearly within the operating range considered. Varying the injection nozzle diameter, whilst keeping the driver pressure constant did not have any significant impact on the peak or average stagnation pressure. The chamber length was also varied and no significant influence was found on peak or average stagnation pressure.