Production of microparticles with biomedical interest using array of obstacles devices

The controlled production of biocompatible microparticles with tailored size and transport properties is crucial for biomedical applications such as drug delivery and blood analogues. This study explores a hybrid milli-microfluidic approach for microparticle fabrication, combining flow-focusing with passive arrays of obstacles to enhance droplet breakup and size control. Two relevant systems were investigated: perfluorodecalin droplets in sodium alginate and sodium alginate droplets in mineral oil. Monodisperse droplets were initially generated using a 3D-printed millifluidic flow-focusing device featuring a herringbone array of obstacles, then further processed in a polydimethylsiloxane microchannel containing transverse rectangular obstacles. Droplet breakup was characterized at the millifluidic outlet and at the microchannel inlet and outlet. At the milliscale, experiments covered viscosity ratios ( X ) from 10 -2 to 10 2 and Capillary numbers of the dispersed phase ( C a d ) from 10 -4 to 10 0 . Results revealed that droplet area distributions at the millifluidic outlet were weakly influenced by flow rates and X , highlighting the dominant role of geometric confinement. However, droplet area decreased with increasing C a d for all values of X . Within the microchannel, successive breakup events reduced droplet diameters from ∼60 µm to ∼10 µm. The results demonstrate that arrays of obstacles provide a simple, efficient, and scalable method for producing uniform micrometric droplets.