A framework to optimize spring-driven autoinjectors.

The major challenges in the optimization of autoinjectors lie in developing an accurate model and meeting competing requirements. We have developed a computational model for spring-driven autoinjectors, which can accurately predict the kinematics of the syringe barrel, needle displacement (travel distance) at the start of drug delivery, and injection time. This paper focuses on proposing a framework to optimize the single-design of autoinjectors, which deliver multiple drugs with different viscosity. We replace the computational model for spring-driven autoinjectors with a surrogate model, i.e., a deep neural network, which improves computational efficiency 1,000 times. Using this surrogate, we perform Sobol sensitivity analysis to understand the effect of each model input on the quantities of interest. Additionally, we pose the design problem within a multi-objective optimization framework. We use our surrogate to discover the corresponding Pareto optimal designs via Pymoo, an open source library for multi-objective optimization. After these steps, we evaluate the robustness of these solutions and finally identify two promising candidates. This framework can be effectively used for device design optimization as the computation is not demanding, and decision-makers can easily incorporate their preferences into this framework.