Characterization of an electromagnetic impact-driven needle-free injector with enhanced pulsed control in a low-jet-power regime.

This study elucidates the development and performance characterization of an advanced electromagnetic impact-driven jet injector version 3 (IDM-v3), specifically engineered to achieve controllable jet formation within a low-jet-power regime. To overcome the excessive kinetic energy challenges observed in its predecessor (IDM-v2), several critical technical refinements were implemented, including the integration of a high-force solenoid, a calibrated 94 g projectile, and a reduced maximum impact stroke of 6 mm. Experimental results indicate that impact force, the calculated impact peak pressure metric, and exit jet velocity are highly sensitive to the impact configuration. The 0.2 mm nozzle produced the highest impact peak pressure, P_peak, of approximately 206 MPa, calculated from the measured peak target force using P_peak=F_peak/A_n. The corresponding jet power, calculated separately from the measured exit jet velocity, was approximately 2 W. In contrast, the 0.4 mm nozzle produced a higher calculated jet power of approximately 6 W because of its larger nozzle-orifice area. High-speed temporal analysis revealed a multi-pulse response in the area-normalized target-force signal and stable jet morphology within the initial millisecond of actuation. Validation through penetration assays on polyacrylamide gels and fresh ex vivo porcine tissue demonstrated that the 0.2 mm nozzle produced a narrower and more focused penetration channel, whereas the 0.4 mm nozzle produced greater lateral spreading and reached a greater final penetration depth under the tested conditions. These findings characterize the tunability of the IDM-v3 engineering prototype and provide a basis for further experimental development and evaluation. They do not establish biological safety or clinical or veterinary readiness.