A fundamental mechanistic understanding of material responses to flow fields is critical for many industrial applications, such as painting, drug delivery through thin needles, and 3D printing. Further, by controlling the flow conditions, different type of materials structures can be formed or tuned. These macroscopic responses are directly related to the microscopic structure in these complex fluids. We are currently particularly interested in 1) developing and/or applying rheological theories to model complex fluid systems, in particular for the analysis of their two-dimensional SAS patterns, to gain fundamental understanding of the relationship between structure and rheological response; and 2) utilizing shearing force to control or tune colloidal self-assembly for novel applications.
Small angle scattering (SAS) and particularly neutron scattering (SANS) has proven to be a powerful technique for probing the structures of complex fluids at the length scale from about one nanometer to hundreds of nanometers and the NIST Center for Neutron Research has a long history of studying shear induced structures. Over the past decade, the facility has built up a robust suite of RheoSANS (combining simultaneous rheology measurements with the SANS structural analysis) and FlowSANS capabilities allowing the probing of structures in all 3 planes of shear, in a variety of shear types (steady or oscillatory, shear or extensional etc.) and rates, and doing so in both a spatially and temporally resolved fashion.
Using these latest, state of the art capabilities, along with more traditional techniques such as light scattering, we are developing a program to take a fresh look at a variety of complex fluids known to be altered by shear, particularly those that exhibit shear-induced transitions of various descriptions.