(171ab) Directed Motion of Light-Activated Janus Colloids in a Thermotropic Nematic Liquid Crystal

Designing synthetic microswimmers has advanced our understanding of the fundamental self-propelled mechanisms of living systems. However, studies on external fields-activated colloids have been mainly done within simple liquids. Here we use a highly structured anisotropic material that displays liquid crystalline mesophases. This host has the potential to serve as biomimetic surrogate to study the structure and dynamics of living systems. Our system consists of 2D confined Janus silica particles, half-coated with titanium in the thermotropic nematic liquid crystal (LC), 5CB. Under an LED illumination, the Janus particles motility is triggered by the self-induction of a nematic-isotropic phase transition. The particle trajectories are constrained by the planar alignment of the LC with respect to the confinement substrates, and tuned by the LED intensity, with the degree of breaking of symmetry playing the major role to direct the motion. Additionally, we propose a phenomenological model that accounts for the viscoelasticity of the LC medium to describe the diffusivity of the Janus particles. Our research contributes to developing a platform for studying highly structured anisotropic materials with interest in the physical, material and biological sciences.