Optimal voice coil actuators for needle-free jet injection

Rotatable Orifice for Needle-Free Jet Injection

This research explores a new development in orifice technology for needle-free jet injection. The premise lies in the ability to control the angle at which the drug is delivered into the tissue to increase the lateral dispersion of the drug. Towards this aim, a spherical orifice that can rotate to adjust the injection angle is explored. This work tests the design and feasibility of the spherical orifice, its housing, and the orifice seats. The results show that the most successful way to create a fluid seal within the housing was to use an o-ring to create a fluid seal at the inlet side of the sphere and an extended brass seat on the outlet side of the sphere. This allowed jet speeds up to approximately 123 m/s through a 0.2 mm orifice machined into 9.5 mm diameter brass sphere. Jet speeds large enough to penetrate porcine tissue were reached at jet angles of 0° to 50° relative to the base of the injector. Although the jets successfully penetrated the tissue, the amount of fluid delivered varied depending on the injection angle. With a shallow angle injection, the fluid retention rate (the percentage of the ejected fluid from the injector which the tissue sample retained) was on average 44%. When the spherical orifice was at its maximum angle, the injection achieved an average fluid retention rate of 22%. At its widest angle, lateral dispersion of the drug also increased by approximately 40%, in comparison to conventional needles and traditional perpendicular jet injection. In summary, a spherical orifice needle-free injection system successfully produced high-speed jets and delivered liquid into porcine tissue at injection angles from 0° to 50°, demonstrating the feasibility of this technique that offers unique advantages over typical orifice plates and conventional needles.Clinical Relevance-A rotatable nozzle can be used to control the angle of needle-free drug delivery.

Jet injectors: Perspectives for small volume delivery with lasers

Needle-free jet injectors have been proposed as an alternative to injections with hypodermic needles. Currently, a handful of commercial needle-free jet injectors already exist. However, these injectors are designed for specific injections, typically limited to large injection volumes into the deeper layers beneath the skin. There is growing evidence of advantages when delivering small volumes into the superficial skin layers, namely the epidermis and dermis. Injections such as vaccines and insulin would benefit from delivery into these superficial layers. Furthermore, the same technology for small volume needle-free injections can serve (medical) tattooing as well as other personalized medicine treatments. The research dedicated to needle-free jet injectors actuated by laser energy has increased in the last decade. In this case, the absorption of the optical energy by the liquid results in an explosively growing bubble. This bubble displaces the rest of the liquid, resulting in a fast microfluidic jet which can penetrate the skin. This technique allows for precise control over volumes (pL to µL) and penetration depths (µm to mm). Furthermore, these injections can be tuned without changing the device, by varying parameters such as laser power, beam diameter and filling level of the liquid container. Despite the published research on the working principles and capabilities of individual laser-actuated jet injectors, a thorough overview encompassing all of them is lacking. In this perspective, we will discuss the current status of laser-based jet injectors and contrast their advantages and limitations, as well as their potential and challenges.

A device for controlled jet injection of large volumes of liquid

We present a needle-free jet injection device controllably actuated by a voice coil and capable of injecting up to 1.3 mL. This device is used to perform jet injections of ~900 μL into porcine tissue. This is the first time that delivery of such a large volume has been reported using an electronically controllable device. The controllability of this device is demonstrated with a series of ejections where the desired volume is ejected to within 1 % during an injection at a predetermined jet velocity.

A compound ampoule for large-volume controllable jet injection

We present a new design for a needle-free injector ampoule, using two concentric pistons to pressurize the fluid during the injection. The smaller, inner piston is used to provide an initial high-velocity piercing jet; it then engages the outer piston to deliver the remaining drug via a low-velocity jet. The goal of this design is to enable needle-free delivery of relatively large volumes to controlled depths in tissue, a task impractical with conventional ampoules and actuators. We demonstrate this concept by constructing a 1.2mL ampoule, measuring the jet velocity it produces in free air, and performing a set of injections into post-mortem porcine tissue. The ampoule smoothly produces the two desired phases of an injection, with a smooth transition of jet velocity as the two pistons engage. The injection is able to penetrate porcine skin to a controlled depth and deliver fluid to the subcutaneous and/or intramuscular layers, though further investigation is required to ensure that all of the fluid delivered can be retained at the desired depth.