Understanding the complexity of living systems poses a significant challenge for modern physics. Active matter offers a platform to explore the fundamental principles driving emergent collective behavior and self-organization. Recent experiments have shown that microtubules interacting with kinesin-4 motors can form structures such as active aster-like micelles and a novel non-equilibrium phase known as active foam. We have developed a field theory to describe these active supramolecular structures, explaining how motor-mediated interactions between microtubules give rise to these macroscopic patterns. Our numerical simulations reproduce the active micelle and foam phases observed in experiments, as well as the density-controlled transition between them. In our model, this transition occurs via a branching instability, breaking the radial symmetry of the micelles and leading to bilayer branch growth along the perimeter.
more