Active dynamics of dissipatively assembled magnetic ribbons

We study the emergent dynamics of self-assembled ribbonlike aggregates that form in paramagnetic colloidal suspensions as an external field is toggled on and off. We note a set of dynamic instabilities that lead to the continual restructuring of aggregates. These are the spontaneous emission of small aggregates as well as their merging and splitting. We measure multiscale dynamics with perimeter tracking and dense optical flow methods and find that the presence of these instabilities increases total motion in the suspension. The dynamic structures formed in these experiments appear to be unique to the dissipative self-assembly of magnetic colloids in toggled fields.