Probing flow-induced nanostructure of complex fluids in arbitrary 2D flows using a fluidic four-roll mill (FFoRM).

Area of Science:

• Materials Science
• Fluid Dynamics
• Neutron Scattering

Background:

• Engineering flow processes is crucial for controlling soft material microstructure.
• In situ small-angle neutron scattering under flow (flow-SANS) analyzes fluid microstructure during simulated processing.
• Current flow-SANS methods require diverse sample environments for comprehensive deformation analysis.

Purpose of the Study:

• To introduce a novel fluidic four-roll mill (FFoRM) for tunable 2D flow fields.
• To enable in situ SANS measurements within a single sample environment for complex flows.
• To characterize soft material nanostructure under arbitrary complex flows.

Main Methods:

• Computational fluid dynamics (CFD) simulations for FFoRM design.
• Particle tracking velocimetry (PTV) for flow characterization in FFoRM.
• Integration of FFoRM with SANS for in situ measurements.

Main Results:

• FFoRM design achieved spatially homogeneous and strong deformation fields.
• PTV experiments validated FFoRM flow characteristics for non-Newtonian fluids.
• FFoRM-SANS workflow successfully characterized flow-induced orientation in cellulose nanocrystal dispersions.

Conclusions:

• The FFoRM provides a versatile platform for studying soft matter under complex flows.
• Cellulose nanocrystals orient along the principal strain-rate axis in steady-state straining flows.
• The FFoRM-SANS approach advances the in situ characterization of fluid nanostructures.