Achievement

Recent experiments by the group of Zvonimir Dogic at Brandeis Univ. (Sanchez et al. Nature 491, 431 (2012)) on bundles of microtubules coupled by kinesins showed that, when confined to a water-oil interface, the microtubule bundles form a dense, nematic film that flows spontaneously in the presence of ATP. The complex self-sustained flows resemble cytoplasmic streaming and yield patterns with pairs of topological defects or disclinations continuously re-generated by activity. The group of PI Cristina Marchetti has developed a continuum model of this active nematic. The theory shows that as a result of activity opposite sign defects can repel, resulting in the proliferation of disclinations. This is opposite to what happens in equilibrium where opposite sign defects always attract and eventually annihilate. The work suggests that one may describe active flows in terms of defect proliferation and dynamics. A paper with L. Giomi, M. Bowick and X. Ma is about to appear in Phys. Rev. Lett.