Microchannel geometry effects on nematic dowser domain dynamics.

Understanding the dynamics of topological defects in liquid crystals is essential for optimizing their performance in adaptive optics, responsive surfaces, and advanced display technologies. Here, we investigate the dynamics of disclination loops enclosing an escaped structure in a nematic liquid crystal, known as dowser domains, within microfluidic channels of various geometries. Through a combination of experiments and numerical simulations, we demonstrate that fluid flow, dictated by the channel geometry alone, governs the dynamics, shape, and size of these domains. We find that channel constrictions extend the lifetime of dowser domains by accelerating their growth, while channel expansions slow down their dynamics and shorten their lifetime. In addition, manipulating the flow paths of dowser domains through serpentine microchannels can further influence their shape and lifespan. We also demonstrate domain splitting in a T-junction microchannel. These findings pave the way for the design of hierarchical networks that can manipulate dowser domains in high-throughput parallel channel systems. Taken together, the results presented here improve our understanding of defect loop dynamics in soft materials and advance the development of flow-based liquid crystal devices and applications.