Behavior of chemically powered active Janus colloids in a uniformly aligned nematic liquid crystal.

The emergence of active nematics has gathered a lot of attention and an exciting recent development in this field was the creation of living liquid crystals. Such materials combine rod-shaped swimming bacteria with water-based liquid crystal, giving rise to an active nematic phase. Our work focuses on studying the individual behavior of active Janus colloids propelled by a catalytic reaction, moving in uniformly aligned nematic liquid crystal DSCG (disodium cromoglycate). Polarized microscopy video imaging shows moving Janus colloids following the nematic director orientation. Motion analysis of two different colloid sizes reveals predominantly ballistic motion along the director, at high acquisition time. At short acquisition times, motion is found to be a combination of anomalous diffusion and ballistic behavior. Small colloids exhibit rolling while moving and yet undergo no change in direction of motion. In comparison, large colloids are relatively slow moving, show no signs of rolling during the time period of observation and cause significant distortion of the nematic environment surrounding them. Our findings suggests that large active colloids are good candidates to scale up the system to achieve collective behavior.