Interfacial Behavior of a Compound Viscous Droplet in a Bounded Micropolar Medium

This study examines the translational motion of a compound droplet consisting of concentric viscous fluid layers as it moves through a bounded micropolar fluid under the influence of interfacial phenomena. The inner core and surrounding shell form a symmetric two-interface configuration, analyzed in the low-Reynolds-number regime. The governing equations are solved analytically, incorporating interfacial boundary conditions that enforce continuity of flow flux and hydrodynamic stresses across both droplet surfaces. The expressions are obtained for the velocity field, vorticity, and microrotation, expressed in terms of shell thickness, micropolarity parameters, spin characteristics, and the effective viscosity ratio. The resulting hydrodynamic force behavior is shown to be highly sensitive to these parameters. Overall, this work establishes a theoretical framework for axisymmetric motion of core–shell droplets and offers valuable insights for the design of tunable microcapsules, advanced drug-delivery vehicles, and biomimetic encapsulated systems in microfluidic applications.