CaIFF Webinar: Viviane Lütz Bueno
Soft Matter Under Flow: in Situ Neutron Scattering for 3D Structural Insights
The structure of soft materials, such as polymers, proteins, and complex fluids, can readily respond to stresses, particularly under flow. These materials often exhibit fascinating structural dynamics that govern their macroscopic properties, such as viscosity, elasticity, or solidification behavior.
To investigate these structure-function relationships, in situ small-angle neutron scattering (SANS) and imaging techniques are essential, as they enable probing the nanostructure of materials in real time while subjected to processing conditions such as shear and extensional flow. By combining SANS with tools like rheology, microfluidics, scanning methods, and real-space imaging, my research aims to capture the interplay between flow conditions and molecular organization with spatial and temporal resolution.
A major focus lies on flow-induced alignment, structural transitions, and phase behavior in systems such as surfactant micelles, colloids, and biopolymer solutions. I will discuss two main experimental achievements, which profit from novel ways to measure a Couette cell coupled to a rheometer:
- Using scanning-SANS under shear flow, we followed how Pluronic F-127 micelles undergo nanoscale hexagonal ordering when sheared. Through the modeling of 3D reciprocal space maps, we define the 3D structure and extract the structure factor of such micelles under shear.
This work innovates the interpretation of shear-induced order through rheoSANS and avoids the need for complementary rheometer types to fully characterize the flow. - Using single-grating dark-field neutron imaging (DFI), we could observe shear banding and deformation of glycerol droplets dispersed in silicone oil, forming a surfactant-free emulsion under shear.
This work demonstrates that DFI can successfully capture directional scattering information from emulsions under flow in a single shot, making it possible to analyze in situ anisotropic structural changes in a timely manner. Unlike conventional SANS, typically limited to nanometer scales, DFI accesses micrometer-scale structures while maintaining a large field of view, thus complementing SANS across broader length scales relevant in soft matter.
While exploring fundamental questions in soft matter systems, I aim to contribute to the methodological development of neutron scattering techniques to monitor dynamic processes, focusing on real-world processing conditions. This includes the development of novel sample environments for in situ measurements and integration of SANS with complementary methods typical in soft matter research.
This integrated approach enables us to connect fundamental insights with practical applications in biomaterials, food science, pharmaceuticals, cosmetics, soft robotics, and sustainable processing. Ultimately, my research aims to bridge molecular-scale understanding with overall material performance by uncovering how soft matter structures evolve under processing conditions. These methods are closely tied to the operation of the SANS-LLB instrument, attracting new users and expanding the soft matter research portfolio at PSI.
Speaker
Viviane Lutz-Bueno, Viviane.lutz-bueno@psi.ch - Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
Registration link to Zoom Event
https://ucph-ku.zoom.us/webinar/register/WN_dKOX_lg8QX6qjSeRb4wnkw