Active motion of Janus particles in thermotropic liquid crystals

Studies of self-propelled colloids suspended in isotropic liquid mixtures have advanced significantly over the last decade. However, investigations of self-propelled systems in out-of-equilibrium liquid crystal (LC) interfaces have been scarce. In this work, we consider light-activated self-propelled particles in nematic systems. Specifically, we use Janus silica particles half-coated with titanium, immersed in a thermotropic LC, and confined in a slit channel. The Janus particles' mobility is triggered by light. The light-absorbing side of the colloids is heated, thereby inducing a localized LC nematic-isotropic (NI) phase transition. Consequently, the colloids move because of the uneven distribution of the NI interface around them. We use particle tracking analysis to examine the optical response of the LC that underlies the particles' trajectories. We implement machine-learning-based simulations to reproduce the colloids' dynamics, accounting for the elastic, surface, and Landau-de Gennes interactions. This research contributes to a better understanding of micro swimmers' trajectories immersed in highly structured media.