Emergent Phenomena in Far-From-Equilibrium Magnetic Granular Ensembles at a Liquid-Air Interface

Remarkable nontrivially ordered self-assembled structures are formed in ensembles of magnetic microparticles suspended at a liquid/air interface and energized by an alternating magnetic field. These dynamic structures emerge as a result of a competition between magnetic and hydrodynamic forces. Each structure (snake) is accompanied by a hydrodynamic vortex quadrupole. Under certain conditions snakes spontaneously break the symmetry of surface flows and turn into swimmers. Observed phenomena have been successfully described by a phenomenological model.