Having characterized the strain rates generated by our microfluidic devices we next use retardance imaging to quantify the degree of alignment in our PII-2T solutions as a function of shear and extensional strain rate for different aggregation types and concentrations. The retardance was measured using a microscope with opposing, orthogonal right and left-handed circular polarizers placed before and after the microfluidic channels, respectively. A schematic of the retardance imaging experimental setup is shown in Figure . In order to accurately measure the retardance, we modeled the realistic imperfections of the optical setup using Mueller matrices and developed a procedure to cancel out contributions from imperfections using multiple images.