Effect of Flow Parameters on the Formation of Core–Shell Pectin–Alginate Droplets in a Microfluidic Platform: Experimental and Numerical Investigation Publisher



Mozhdehbakhsh Mofrad Y ; Asiaei S ; Navaei Nigjeh M ; Abdollahi M
Source: International Journal of Multiphase Flow Published:2026

Abstract

Core–shell microparticles play an important role in biomedical applications. However, the droplet formation dynamics, interfacial behavior, and flow regimes of aqueous–aqueous–oil (W/W/O) core–shell systems remain largely unexplored, despite their considerable potential for biomedical applications. In this study, a novel core–shell W/W/O system based on pH-responsive polymers, sodium alginate (SA), and pectin (PEC), is introduced and investigated through numerical and experimental approaches. The physical properties of phases are measured, providing a valuable database for modeling multiphase systems in biomedical applications. Rheological characterization revealed that the flow behavior of the polymeric phases is strongly concentration-dependent. At the concentrations employed in this study, both SA and PEC solutions exhibited Newtonian behavior. The effect of flow parameters on droplet formation and interfacial behavior was analyzed. The results show that flow regimes are classified into stable and unstable, with transitions governed by the capillary number (Ca). Among the stable regimes, the dripping regime yields core–shell microparticles with an average diameter of 140.7633 μm and a coefficient of variation (CV) of 0.093433, indicating a uniform size distribution. Droplet size and shell thickness are controlled by phase flow rates, with the continuous phase flow rate exerting the strongest influence: it is inversely related to droplet size and shell thickness and directly related to generation frequency. Unstable regimes involve the formation of satellite droplets, leading to loss of uniformity, broadened size distribution, and reduced structural integrity. Middle-phase satellites originate from multi-stage jet breakup or incomplete pinch-off with filament retraction, while inner-phase satellites are associated with complex hydrodynamic interactions near the breakup region. These results enable the controlled generation of core–shell microcarriers with desired characteristics for targeted and pH-sensitive drug delivery as well as cell encapsulation applications. Copyright © 2026. Published by Elsevier Ltd.