(591c) Crystallization of Soft Cuboidal Blue Phase Liquid Crystals in Shells

Crystallization under curved geometrical constraints is governed by different parameters, including the degree of curvature, spatial restriction, and surface chemistry. The stress induced by the curved space can influence nucleation and growth pathways by forming topological defects. Here, we investigate the crystallization of soft blue phase (BP) liquid crystals under curved geometrical confinement. BPs are high chirality liquid crystals in which the chiral molecules are self-assembled into 3D nano-cuboidal lattices. BPs can adopt different crystalline symmetries named BPI with body-centered cubic structure and BPII with simple cubic structure. Moreover, due to their submicron crystalline lattices, BPs manifest Bragg reflection in visible light wavelength.

To study the effect of curved confinement on the crystallization of BPs, we employed a microfluidic device to fabricate BP core-shells with different degrees of curvature, shell thickness, and surface anchoring. Sodium dodecyl sulfate (SDS) and poly(vinyl alcohol) (PVA) were used to enforce homeotropic (normal) and planar surface alignment, respectively. Our results demonstrate that exposing BPI shells to homeotropic anchoring deforms the disclination lines at the interface, leading to a distinct blueshift in Bragg reflection. Moreover, strong confinement and high degrees of curvature can destabilize BPI, which can be attributed to its larger lattice size than BPII. Finally, our computational and experimental studies reveal that the coupling of curvature and confinement in shells with hybrid surface alignment initiates the formation of half-skyrmions excitation at larger thicknesses than those reported for flat geometries. This fundamental knowledge is particularly important for deploying these materials in flexible miniaturized devices such as display technologies and wearable sensors.