''Over the horizon'' SANS: Measurements on near-surface Poiseuille shear-induced ordering of dilute solutions of threadlike micelles

Although the behavior of a fluid under shear near a surface can be expected to be critically important to its drag and lubrication properties, most shear measurements to date have been of the bulk. This paper outlines the use of a specially developed Poiseuille shear cell at grazing incidence to measure the small-angle neutron scattering (SANS) signal from the first few tens of microns in the interfacial region. We illustrate the technique with measurements made on the near-surface ordering in flow past a quartz surface of dilute surfactant solutions comprising highly extended self-assembling ''thread-like'' micelles.