Creation and evolution of defects in composite biopolymer nematics

Structured soft materials have internal order that give rise to unusual mechanical properties and emergent organization of inclusions. Here we present a composite structured liquid formed from biopolymers of distinct rigidities, actin and DNA. Actin filaments, well below their persistence length, behave as rigid rods while long polymers of DNA, well above their persistence length, form globular molecules. Crowded into a thin layer, actin filaments form a nematic liquid crystal phase within the DNA domains. As these nematic phases grow and coalesce, defects in the actin nematic filled with DNA are created. We investigate the evolution of these soft, polymer filled defects and compare the dynamics to a continuum model of lyotropic liquid crystal. From the model, we use the defect shape to extract material properties of the liquid crystal. Our results suggest a novel structured soft composite, potentially informing physical mechanisms of controlling material properties and templating functional polymeric materials.