This is a rotating disk shear cell with optically clear quartz plates as disks. The sample is a dilute charge stabilized colloidal particle suspension. The suspension crystallizes at equilibrium to a large collection of randomly oriented polycrystals. With the application of shear flow, the crystallization orients throughout the cell with a close packed direction in the crystal structure parallel to the local flow direction. The colors you see result from the Bragg scattering of white light from the ("single") oriented crystal in the sample. The size of the shear cell is ~25 cm in diameter.
We have a Bohlin constant stress rheometer for measuring the viscosity and elasticity of suspensions. Here we show the viscometer fitted with a glass concentric cylinder shear cell for combined light diffraction and shear measurements. Note the blue low order Bragg diffraction pattern on the paper screen mounted on an index matching bath. The shear cell is inside the bath.