Dendritic patterns from shear-enhanced anisotropy in nematic liquid crystals

Abstract

Controlling the growth morphology of fluid instabilities is challenging because of their self-amplified and nonlinear growth. The viscous fingering instability, which arises when a less viscous fluid displaces a more viscous one, transitions from exhibiting dense-branching growth characterized by repeated tip splitting of the growing fingers to dendritic growth characterized by stable tips in the presence of anisotropy. We controllably induce such a morphology transition by shear-enhancing the anisotropy of nematic liquid crystal solutions. For fast enough flow induced by the finger growth, the intrinsic tumbling behavior of lyotropic chromonic liquid crystals can be suppressed, which results in a flow alignment of the material. This microscopic change in the director field occurs as the viscous torque from the shear flow becomes dominant over the elastic torque from the nematic potential and macroscopically enhances the liquid crystal anisotropy to induce the transition to dendritic growth.

Flow-induced periodic chiral structures in an achiral nematic liquid crystal

“…Indeed, in addition to the splay deformation in the x y -plane, the shear torques induced by the pressure-driven flow in the gap of the microfluidic cell induce a divergent splay deformation across the gap thickness, as shown in the inset of Fig. 2 c. The deformation of the director field is reflected in the value of the gap-averaged polar angle θ ≈ 45°, which deviates from the initial planar alignment as a result of the tumbling property of nematic LCLC solutions 38 , 40 , 42 , 43 , as shown in Fig. 2 c. The combination of the convergent splay deformation in the x y -plane and the divergent splay deformation in the x z -plane induces a biaxial-splay configuration in which the director field undergoes a twist deformation when rotating about the symmetry line of the splay deformations with a rotation angle, β , as schematically shown in Fig.…”

Anomalous‐Chern Steering of Topological Nonreciprocal Guided Waves

“…The other type of disorder, global phase disorder, has already been experimentally investigated elsewhere. [37,38] Thus, we randomly select 5 out of the 16 varactors in the active region and disconnect them.…”

“…The idea is based on the unique physics of unitary topological systems, [34][35][36] which are non-reciprocal topological insulators that support not only the Chern phase, but also a distinct, extremely robust anomalous phase. [37,38] Crucially, Region A is a honeycomb network of circulators connected by transmission lines (TLs) of phase delay 𝜑. Region S is similar to region A, except for the introduction of unitary scatterers at the middle of each TL (bottom inset, yellow boxes).…”