Bend instability and topological defects in 3D active nematics*

Active nematics describes a phase of matter where active particles that consume energy to produce mechanical work assemble at high density in a state with orientational order but no positional order. In this talk, I will show how the active nematic framework allows us to better understand aspects of the collective behaviors that emerge in bioinspired materials. In particular, I will present our recent efforts to describe the emergence of flows and topological defects in 3D active nematics composed of a passive colloidal liquid crystal doped with active microtubules and molecular motors. I will first describe the generic bend instability that emerges in a flow-aligned 3D active gel and show how the interplay between activity, nematic elasticity and confinement controls the wavelength of this activity driven instability. I will then present current work on the emergence of flows and topological defect in 3D.