Non-Brownian Motion of Janus Particles in liquid crystals

Inspired by micro-swimmers in nature, significant studies on non-Brownian particles have been developed in the last decade. Examples include experiments conducting self-propelled colloids primarily suspended in water-like mixtures, activated by different methods. Rather than using water as a solvent, we choose to use a nematic structured medium. In this work, we implement microscopic Janus silica particles half-coated with titanium, immersed in a thermotropic liquid crystal. When the sample is heated slightly below the nematic-isotropic (NI) phase transition, the Janus particles’ mobility is triggered by light. The titanium side of the colloids is heated, thereby surpassing the isotropic temperature threshold. Consequently, the colloids use the localized NI phase transition to self-propel through the liquid crystal. Implementing particle tracking analysis allows us to further study the colloids’ patterns of movement. Accounting for birefringence intensity and particle rotation helps to predict the particles’ trajectories. In addition, we make a comparison between the Brownian case and the activated colloids. Our studies foster a better understanding of predicting trajectories in micro-swimmers immersed in structured media at the NI phase transition.