Conceptualisation of a novel electromechanical system for small-volume needle-free jet injection

Needle-free jet injectors are minimally invasive drug delivery systems that utilise high-velocity microjets (∼100 m/s) created by pressurising the liquid drug through a micronozzle (50–300 µm in diameter). Most of the current commercially available jet injectors use a mechanical power possessed by a compressed spring or air to pressurise the fluid inside the injection chamber to deliver the liquid drug (typically ∼100 µL in volume) into the skin matrix. However, they cannot be utilised for achieving shallow penetration depths as they lack dynamic control that can shape the real-time microjet characteristics. Recently, electrically or optically powered jet injection systems are being developed to achieve shallow penetration depth by small-volume (<5 μL) injections. However, they require complex system and have a limited injection frequency (maximum reported value is 16 Hz). Herein, we propose a novel electro-mechanical jet injection system, where a mechanically actuated source pressurises the fluid inside the injection chamber and an electrically actuated system controls the characteristics of the propelled microjet. A computational model was developed to prove the feasibility of the proposed system, and the obtained results showed that the proposed system could produce stable small-volume microjets at about 100 Hz frequency that could be utilised for drug delivery applications.