Flow birefringence
In biochemistry, flow birefringence is a hydrodynamic technique for measuring the rotational diffusion constants. The birefringence of a solution sandwiched between two concentric cylinders is measured as a function of the difference in rotational speed between the inner and outer cylinders. The flow tends to orient an ellipsoidal particle in one direction, whereas rotational diffusion causes the molecule to become disoriented. The equilibrium between these two processes as a function of the flow provides a measure of the axial ratio of the ellipsoidal particle.
