Illuminating Complex Fluid Properties and Flow

Sticky gooey liquids, often called complex fluids, are an integral part of our lives from the plastics in consumer products to the surfactant solutions in pharmaceuticals. Despite their use in everyday life, the physical and flow properties of complex fluids are not yet fully understood. My work focuses on characterization of complex fluids and materials in diverse contexts using durometry [1], rheology [2,3,4,5,6] and transport phenomena [7,8].

Previously, I investigated the motion of polymeric and micellar solutions undergoing shearing flows. A common flow field for exploring complex fluid rheology is large-amplitude oscillatory shear (LAOS). From LAOS, we can learn how much memory (elasticity) a fluid has and how well it can dissipate energy (viscosity). The viscoelasticity of a fluid is a result of a material’s molecular structure and its interactions with other fluid components. Flow imparts an orientation on fluid elements (molecules, micelles, etc.), and this orientation is an integral part of molecular models used to predict fluid behavior [5]. We leverage light, X-ray, and neutron scattering techniques to observe complex fluid orientation during flow to inform our fluid viscoelasticity modeling [9].

Most recently, I have turned my attention toward characterizing the morphology of medically relevant surfactant solutions using scattering techniques. By exploring how these micelle suspensions organize themselves under different conditions, we can improve pharmaceutical product performance and deepen our fundamental understanding of these important fluids.

Figure 1. Small-angle light scattering of fluid sheared between parallel disks.

Figure 2. Anisotropic scattering from LAOS of worm-like micelles showing orientation and micelle disintegration.

Publications

1. Gilbert, P.H. and A.J. Giacomin, “Exact Analytical Durometer Hardness Scale Interconversion,” Journal of Testing and Evaluation, 46(5) 1995-2032 (Sept. 2018).
2. Giacomin, A.J., P.H. Gilbert, and A.M. Schmalzer, “Fourier decomposition of polymer orientation in large-amplitude oscillatory shear flow,” Structural Dynamics, 2(2), 024101 (March 2015).
3. Giacomin, A.J., P.H. Gilbert, D. Merger and M. Wilhelm, “Large-Amplitude Oscillatory Shear: Comparing Parallel-Disk with Cone-Plate Flow,” Rheologica Acta, 54(4), 263-285 (April 2015).
4. Gilbert, P.H. and A.J. Giacomin, “Complex Polymer Orientation,” Polymer, 104, 227-239 (Nov. 2016).
5. Gilbert, P.H. and A.J. Giacomin, “Molecular Origins of Higher Harmonics in Large-Amplitude Oscillatory Shear: Shear Stress Response,” Physics of Fluids, 28, 103101 (2016).
6. Giacomin, A.J., R. Pasquino, C. Saengow and P.H. Gilbert, “Degradation in Parallel-Disk Rheometry,” Rheologica Acta, 58(5) 1-15 (2019).
7. Gilbert, P.H., C. Saengow and A.J. Giacomin, “Transport Phenomena in Eccentric Cylindrical Coordinates,” AIChE Journal, 63(8), 3245-3623 (Aug. 2017).
8. Gilbert, P.H. and A.J. Giacomin, “Transport Phenomena in Bispherical Coordinates,” Physics of Fluids, 31(2), 1-17 (Jan. 2019).
9. Gilbert, P.H. and A.J. Giacomin, “Small-Angle Light Scattering in Large-Amplitude Oscillatory Shear,” Physics of Fluids, 31(10), 103104 (October, 2019).