In order to investigate the effectiveness of both shear and extensional flow on the alignment of our conjugated polymer, we used microfluidic devices to access high strain rates necessary to achieve flow-induced alignment of conjugated polymer in solution. Narrow microchannels were required to reach extremely high shear rates up to ~10 6 s -1 and extensional strain rates up to ~10 5 s -1 in order to observe flow-induced retardance (birefringence). Such strain rates are significantly higher than those explored in prior work on microfluidic flow birefringence and required microchannels orders of magnitude smaller. Shear was achieved by flow through narrow straight channels and extension was achieved through the use of a cross-slot geometry with opposing inlets and outlets. For this work, the term shear rate refers to the shear rate at the walls of the straight channel and the term extensional strain rate refers to the extensional strain rate at the stagnation point of the cross-slot. Schematics of the shear and extensional microchannels used are shown in Figure and B, respectively. In order to verify the true, experimental shear and extensional strain rates produced in the microfluidic device we used high speed micro-particle tracking velocimetry (µ-PTV). An accurate measure of the strain rates is necessary to accurately quantify the relaxation time of the material. Due to the extremely high velocities, we were only able to characterize the shear rates at flowrates up to 20 µL/min instead of the full range up to 260 µL/min used in the retardance experiments. We emphasize that even with the use of a high speed camera we were limited by the frame rate (30,000 fps) due to the extremely high velocities and strain rates that were necessary. For a Newtonian fluid the theoretical wall shear rate ̇ for a rectilinear channel is ,