Microplate Active Migration Emerging From Light-Induced Phase Transitions in a Nematic Liquid Crystal

Achieving precise control over the diverse equilibrium configurations and corresponding optical textures of motile liquid crystals (LCs) in response to a wide range of external stimuli is a formidable challenge. This complexity becomes even more intriguing when applied to far-from-equilibrium systems. In this work, we investigate how LC phase transitions are leveraged to achieve controlled self-propulsion of colloids. To accomplish that, we designed quasi-2D solid, micron-sized, light-absorbing platelets suspended in a thermotropic nematic LC. When exposed to light, these platelets self-propel, generating localized nematic-isotropic (NI) phase transitions. The system's dynamics are governed by temperature, light intensity, and confinement, giving rise to three regimes: a large 2D regime where the platelet-isotropic phase bubble remains stationary with a stable NI interface; a compact motile-2D regime where the NI interface is closer to the platelet; and a motile-3D confinement regime, marked by the appearance of multipolar LC configurations. Furthermore, we employed continuum mean-field simulations to predict stable platelet-LC states in slab confinements. The approach gives insights crucial for designing far-from-equilibrium synthetic systems with controlled propulsion and tunable topological reconfigurations. This has implications for advancements in photonics and material sciences.