Optimization of Portable Electronically Controlled Needle-Free Jet Injection Systems

Jet injection is a process by which a fluid drug is delivered through the skin in the form of a high-velocity jet. Powering jet injection using a controllable actuator, such as a moving-coil permanent magnet motor, offers many advantages, but to date has required large and heavy injection systems to provide the required power and control bandwidth. In order to minimize the size of the injection system, we developed a scaling model for jet injection systems powered by permanent magnet motors, giving the optimal actuator mass as a function of jet velocity, injection volume, motor efficiency, and energy storage density. We combined this model with an existing electromagnetic model to confirm the predicted scaling relationships and find optimal actuator designs. On this basis, we designed an injection system for 50 μL volumes, including a compact power amplifier and control system, and verified its performance by performing injections into pig skin. The total mass of the injector system was 578 g, with a 178 g handpiece. This model illustrates fundamental relationships that govern the design of any jet-production device powered by linear electric motors for jet injection or other applications.