(191cr) Interaction of Multiple Drops and Formation of Toroidal-Spiral Particles

In the development of drug delivery technologies for treating complex diseases, encapsulating multiple compounds and manipulating their sustained-release kinetics independently (for optimal therapeutic effect) can be challenging. We previously developed a fluid-dynamic technology based on multiple-drop interactions to achieve this goal. During sedimentation in a viscous liquid, polymeric droplets self-assemble into a reproducible and controllable toroidal-spiral (TS) structure, which could be solidified into solid particles by photo-initiated cross-linking of the polymer. The goal of encapsulating multiple drops featuring different physical properties generally requires complicated and time-consuming experimental iteration on the starting conditions, because all satellite drops (containing drugs) must catch up and coalesce simultaneously with the host drop that forms the surrounding matrix upon solidification. To guide laboratory trials and optimize conditions, a computational simulation is needed to accurately predict the configurations and interfaces of the multiple drop phases, especially when each drop comprises different physical properties. Our creeping-flow numerical simulations of drop sedimentation and interactions closely resemble the experimental shapes of single and multiple, interacting drops, and also reveal the internal interfaces and structures. Furthermore, understanding fundamental hydrodynamics of multiple drops could lead us to potential scale up production of TS particles and impact on mixing and printing in general.