Multidirectional manipulation of anisotropic particles embedded in nematic media using photo-alignment

Controlling the position and orientation of colloidal particles in liquid crystal (LC) systems provides a significant opportunity to exploit their unique properties and enhance functionality. In this study, we present a method to manipulate cylindrical colloids, specifically carbon fibers (CFs) dispersed in a nematic medium. This is achieved by altering the easy axis of a photo-responsive alignment layer using patterned linearly polarized UV light. The CFs consistently realign in response to changes in the easy axis, exhibiting repeatable and reliable behavior. Additionally, positional control is achieved by placing CFs at boundaries between regions with distinct easy axes, utilizing the elasticity of the nematic medium to minimize free energy. The controllability depends on the UV irradiation pattern and the distribution of CFs within the irradiated regions. We analyze this behavior using a free energy model based on CF position and orientation. These findings provide new insights into the precise manipulation of anisotropic colloidal particles, suggesting the way for advanced applications in LC-based materials and devices.