Viscous fingering in lyotropic chromonic liquid crystals

We studied the Saffman-Taylor instability in a Hele-Shaw cell containing nematic lyotropic chromonic liquid crystals. The coupling between the flow field and director field changes the effective viscosity of the liquid crystal, and therefore influences the patterns formed by the injected liquid. In particular, the hugely different viscosities for different distortion modes in chromonic liquid crystals play important roles in determining the patterns. Besides changing the viscosity of injected fluid and the injection rate, we can also control the pattern by changing the concentration of chromonics in water solution, which tunes the anisotropic viscosities. By quantitatively comparing the local director field with flow field, we show that the intrinsic anisotropy of the displaced liquid can lead to rich and controllable patterns in a Hele-Shaw cell setup.