Droplet and particle formation in an X-microdevice

Micro-and nano-droplets and particles find diverse applications in fields such as bi- ology, biotechnology, and pharmaceuticals. They can be fabricated using a variety of materials, both organic and inorganic, and employing various techniques. In particular, these particles are utilized for drug delivery, enabling the transport of Active Pharmaceutical Ingredients (APIs) within the human body. Achieving precise control over the shape, composition, and size of nanoparticles is crucial for such applications. Recent advances in microfluidics have played a key role in ensuring an accurate control of particle quality and many device geometries have been proposed in the literature to achieve well-controlled droplet generation, including the T- and X- shaped junctions used, e.g., for hydrodynamic flow focusing or co-axial injection. In this study, we explore the capabilities of numerical simulations for the computation of droplet and particle formation in microfluidic devices, drawing comparisons with experimental results. Specifically, we employ an X-junction to generate (i) alginate droplets using the segmented dispersed phase method and (ii) chitosan nanoparticles via solvent displacement method. Numerical simula- tions satisfactorily agree with experiments for all the considered flow rates. Thus, they are demonstrated to be effectively useful in evaluating how different flow regimes occur inside the microdevice as a function of the inlet flow rates and how these, in turn, impact the size and distribution of droplets and particles.