We have recently developed a flow-microscopy device for direct visualization of complex fluids in Couette flow. Although still under development, we hope to use the flow-microscope to study the structural evolution of colloidal suspensions under a variety of flow conditions, including shear startup/cessation, large amplitude oscillatory shear, and steady shear. Some of the intended capabilities of the instrument are depicted below, and include flow visualization under bright field and fluoresence conditions, as well as particle imaging velocimetry measurements.

Figure 1. Video micrograph of a suspension of 40 micron silica spheres suspended in a 30wt% solution of hydroxypropylcellulose in water at a shear rate of 0.14 s^-1.

Figure 2. Velocity profile constructed by tracking of particles in the movie at left. The deviation of the velocity from the expected Newtonian profile (dotted line) demonstrates shear thinning of the fluid.