Analysis of Moving-Coil Actuator Jet Injectors for Viscous Fluids.

Abstract

A jet injector is a device that can be used to deliver liquid drugs through the skin using a fluid jet, without the use of a needle. Most jet injectors are designed and used for the delivery of inviscid liquids, and are not optimized for the delivery of viscous drug compounds. To better understand the requirements for delivering viscous drugs, we have developed a mathematical model of the electromechanics of a moving-coil actuated jet injector as it delivers viscous fluids. The model builds upon previous work by incorporating the nonlinear electrical properties of the motor, compliant elements of the mechanical piston and ampoule system, and the effect of viscosity on injector characteristics. The model has been validated by monitoring the movement of the piston tip and measurements of the jet force. The results of the model indicate that the jet speed is diminished with increasing fluid viscosity, but overshoot and ringing in the jet speed is unaffected. However, a stiffer ampoule and piston will allow for a better control of the jet speed profile during an injection, and reduce ringing. We identified that the piston friction coefficient, the compliance of the injector components, and the viscous properties of the fluid are important determinants of performance when jet-injecting viscous fluids. By expanding upon previous jet injector models, this study has provided informative simulations of jet injector characteristics and performance. The model can be used to guide the design of future jet injectors for viscous fluids.