Cholesteric Liquid Crystal Control Through Microfluidic Flow Manipulation

Materials capable of undergoing color changes in response to stimuli are of interest for various applications, including sensing, display technology, and camouflage. Cholesteric liquid crystals represent a unique class of soft materials due to their self-assembled helical structure, which is sensitive to various external stimuli and known for its selective light reflection. However, their response to pressure-driven flow in microfluidic channels has largely remained experimentally unexplored. Here, we investigate a cholesteric system with a helical pitch comparable to the wavelength of visible light, enabling it to exhibit structural coloration. We demonstrate that fluid flow can effectively align the helical axis of cholesterics within confined geometries. Before the application of flow, the color of the cholesteric phase remains independent of temperature. However, after flow alignment, a blue shift is observed as the temperature increases. Microfluidic flow creates cholesteric textures with helical pitches longer than those observed in the stationary chiral phase. We observe that flow creates stable-colored bands, which maintain their stability for months. The flow-structure relationships revealed by our study have potential relevance for applications such as additive manufacturing of liquid crystals.