Visualization of Individual DNA Chains In Entangled Solutions Using High-Speed Confocal Microscopy

Previous experiments in polymer rheology have produced monotonic relationships between the imposed shear rate and the resulting shear stress. These results guided the belief that shear flow of entangled polymers is homogeneous. However, recent experimental work has shown experimental evidence for steady-state shear banding and wall slip in entangled DNA solutions. In order to explain these unexpected flow phenomena and further the knowledge of polymer rheology it would be valuable to watch the molecular behavior of individual polymer chains during these rheological experiments where the shear banding occurred. We have conducted experiments studying the flow of entangled DNA solutions by visualizing individual chain behavior of stained DNA molecules during microchannel flows. We have reproduced the conditions leading to interesting flow behavior such as wall slip and shear banding and observed individual chain behavior that leads to such flow phenomena. These results offer valuable experimental evidence to explain and understand nonlinear flow behavior and its origins