Andrea Cavicchi

Dynamic behavior of a spring-powered micronozzle needle-free injector.

Conventional injection is still the leading method to deliver macromolecular therapeutics. Needle injection is considered a low compliance administration strategy, principally due to pain and needle phobia. This has fostered the research on the development of alternative strategies to circumvent the skin barrier. Among needle-free drug delivery methods, jet injection is an old strategy with great potential not yet completely disclosed. Here, the design, engineering and dynamic behavior of a novel spring-powered micronozzle needle-free injector is presented. Fluid mechanics was first studied in air to calculate jet force and speed as well as injection duration in different conditions. Polyacrylamide gel was used to simulate a soft tissue and to investigate the jet evolution over time of different injected doses. Finally, ex vivo characterization was carried out on pig skin. Results evidenced a direct dependence of the force, velocity, and duration with the injection volume. The model material allowed individuating the different steps of jet penetration and to attempt a mechanistic explanation. A different behavior has been recorded in the skin with interesting findings for subcutaneous and/or dermal delivery. Peculiar features with respect to existing jet injectors confers to this device good potentiality for a future clinical application.

Experimental and Numerical Assessment of Multi-Event Injection Strategies in a Solenoid Common-Rail Injector

Nowadays, injection rate shaping and multi-pilot events can help to improve fuel efficiency, combustion noise and pollutant emissions in diesel engine, providing high flexibility in the shape of the injection that allows combustion process control. Different strategies can be used in order to obtain the required flexibility in the rate, such as very close pilot injections with almost zero Dwell Time or boot shaped injections with optional pilot injections. Modern Common-Rail Fuel Injection Systems (FIS) should be able to provide these innovative patterns to control the combustion phases intensity for optimal tradeoff between fuel consumption and emission levels.In this work, a 1D-CFD model in GT-SUITE of a solenoid ballistic Common-Rail injector was firstly refined respect to the previous work [1] and then it was validated against an extensive experimental dataset of single injections, standard double pilot and multi-pilot injection patterns (up to 4 pilot events) with almost zero dwell time between two consecutive injection events. The experimental hydraulic test data used to validate the one-dimensional model were obtained by means of the UniPG Injection Analyzer based on the Zeuchs method.The comparison between the experimental and simulated volumetric injection rates showed a more than satisfactory accuracy of the model in predicting the actual behavior of the ballistic injector for all the injection patterns tested, even for relatively complex injector command strategies, characterized by reduced Dwell Time values between consecutive injection events.