Cyclic Rearrangement of a Disordered Ferrofluid Raft

In nature, disordered materials will generally find progressively more stable states through stochastic thermal fluctuations. In this work, we observe the evolution of a disordered raft of ferrofluid droplets under oscillatory driving from the magnetic field. We produce a two-dimensional, bi-disperse raft of ferrofluid droplets at an oil-water interface held together by cohesive forces and confined by the meniscus. The raft is placed in a uniform magnetic field which induces a force of repulsion between the ferrofluid droplets. If the strength of this repulsion is high enough, cohesive bonds between droplets are broken, allowing the raft to find new states. Cyclically driving the magnetic field allows the raft to sample more configurations, and the system finds more stable configurations.