Passive microfluidic-based core-shell drug delivery: a fluid mechanics-centric review

Core-shell microparticles have gained significant attention in drug delivery systems due to their ability to encapsulate multiple compounds, provide controlled release, and enhance stability. Conventional synthesis methods often face challenges in achieving uniform particle size and shell thickness. This review summarizes passive microfluidic techniques as a precise and reproducible approach for producing core-shell microparticles. The review focuses on the microfluidic aspects of the process, with three key parameters analyzed: physical properties of the phases, flow characteristics, and microfluidic chip geometries. Previous studies on the effects of hydrodynamic parameters (including flow rate, viscosity, and interfacial tension) on droplet formation are summarized, along with analyses of how different microfluidic chip geometries optimize particle size and morphology. By compiling and analyzing data from previous studies, this review provides a comprehensive analytical framework that can aid in optimizing process parameters for generating monodisperse droplets with precise control over shell thickness and core size. This extensive review highlights the key factors influencing passive core-shell microparticle production and offers guidance for designing and developing more efficient microfluidic systems for drug delivery and other biomedical applications.