Sunset Yellow Confined in Curved Geometry: A Microfluidic Approach

Abstract

The behavior of lyotropic chromonic liquid crystals (LCLCs) in confined environments is an interesting research field that still awaits exploration, with multiple key variables to be uncovered and understood. Microfluidics is a highly versatile technique that allows us to confine LCLCs in micrometric spheres. As microscale networks offer distinct interplays between the surface effects, geometric confinement, and viscosity parameters, rich and unique interactions emerging at the LCLC–microfluidic channel interfaces are expected. Here, we report on the behavior of pure and chiral doped nematic Sunset Yellow (SSY) chromonic microdroplets produced through a microfluidic flow-focusing device. The continuous production of SSY microdroplets with controllable size gives the possibility to systematically study their topological textures as the function of their diameters. Indeed, doped SSY microdroplets produced via microfluidics, show topologies that are typical of common chiral thermotropic liquid crystals. Furthermore, few droplets exhibit a peculiar texture never observed for chiral chromonic liquid crystals. Finally, the achieved precise control of the produced LCLC microdroplets is a crucial step for technological applications in biosensing and anticounterfeiting.

Curvature-mediated programming of liquid crystal microflows

“…43,44 Confining the latter material into spherical structures is expected to be a promising avenue for novel flow control methods. 45 However, the flow behavior of chromonic phases in curved microfluidic channels, as well, remains to be investigated. In comparison, flows of isotropic fluids through curvilinear microchannels have received extensive attention for many decades, with distinct curvature-induced fluid dynamic outcomes.…”

Microfluidics-Based Drying–Wetting Cycles to Investigate Phase Transitions of Small Molecules Solutions

“…On the other hand, lyotropic liquid crystal droplets, including chromonic SSY and cellulose nanocrystals, have been produced in water-in-oil emulsion [68,69], and osmotic droplet shrinkage has been exploited to observe phase transitions or topological reconfigurations [70].…”