(252g) Microfluidic Flow of Blue Phase Liquid Crystal | AIChE

(252g) Microfluidic Flow of Blue Phase Liquid Crystal


Norouzi, S. - Presenter, University of South Carolina
De Pablo, J. - Presenter, University of Wisconsin-Madison
Martinez-Gonzalez, J. A., University of Chicago
Sadati, M., The University of South Carolina
In order to escape the high energy level, highly chiral liquid crystals spontaneously adopt the biaxial orientation, in which the molecules self-assemble into the double twisted cylindrical (DTC) structures to form the cubic symmetry. The DTC structures cannot fill out the entire lattice space, so, the amorphous area known as disclination lines form. These structures are so-called blue phase liquid crystals (BP). This class of liquid crystals exhibits selective Bragg reflections of incident light that makes them suitable for photonic applications. Along with fascinating optical properties, due to their fast and precise responsiveness, they have found potential applications in electro-optics and biosensing technologies. However, their narrow thermal stability limits their widespread applications. Ongoing research has widely focused on implementing heterogeneous materials such as polymers and nanoparticles to broaden the thermal stability of the blue phases. Geometrical confinement can also be considered as a viable approach to stabilize the blue phase structures. Confining the BPs into micro/nanoconfinement gives rise to fascinating optical phenomena, which are of critical importance from a practical point of view. In this study, we use the microfluidic technique to generate spherical droplets with controlled size and narrow dispersity. The droplets are produced in the jetting regime, where due to Rayleigh instability the surface tension wins over the viscous force. We have found that the structures of the blue phase liquid crystals are considerably affected by the extent of the forces acting on it. Our results show that the transition temperatures reduce as the droplet size decreases. Moreover, encapsulating the blue phase structures under shear flow results in a significant decrease in the transition temperatures but an increase in the stability of the blue phases compared to their bulk state. These structures are metastable, and transition temperature rates are droplet size correlated; the smaller droplets show sharper transition. This study demonstrates the fascinating prospects of stabilized blue phases, which can be used in the fields of mechano-optical metamaterials.