Ferrofluid droplet breakup under magnetic fields with MDPD simulations

Ferrofluids are colloidal suspensions of magnetic nanoparticles (MNPs) with a wide range of applications, particularly in soft robotics. In this field, ferrofluid droplets can be externally manipulated to perform specific tasks, such as drug transport and delivery. Our study focuses on simulating the formation of ferrofluid droplets and their behavior under nonhomogeneous external magnetic fields, aiming to control the droplet breakup process at molecular-scale systems. To achieve the required small length scales, we utilize many-body dissipative particle dynamics (MDPD), a mesoscopic particle-based simulation method. MNPs are modeled as point particles with permanent dipole moments free to rotate in space. To validate our ferrofluid model, we first investigate the equilibrium properties of sessile droplets, such as their contact angles, and analyze how these properties depend on external homogeneous magnetic fields and MNP concentrations. Subsequently, we simulate the Rayleigh-Plateau instability under nonhomogeneous external magnetic fields to examine their influence on the breakup dynamics of a liquid thread. The magnetic field is tailored to control the number of droplets formed. Our findings reveal a possible transition between a magnetically induced breakup regime and a natural breakup regime, influenced by the number of droplets and the dipole moment strength.