The processing of materials plays a central role in the disciplines of chemical engineering and materials science. Materials often are in a liquid or liquid-like state while being processed, and have interfaces with other media. Many such materials also contain complex structural elements like colloidal particles, polymer chains, and surfactant aggregates whose size is much larger than that of typical solvent molecules.
Our research involves integration of transport phenomena, colloid and interface science, rheology, applied and computational mathematics, and experiments to address fundamental issues motivated by problems in materials processing. These fundamental investigations are frequently inspired by industrial applications in areas such as coating and printing processes, polymer processing, nanofluidics/microfluidics, and energy. Topics of current interest include:
Dynamic wetting: Dynamic wetting is crucial to processes where liquid displaces another fluid along a solid surface, such as the deposition of a liquid coating onto a moving substrate or the displacement of oil in rock pores. Our efforts are aimed at improving fundamental understanding of dynamic wetting, and harnessing that understanding to address materials-processing-related issues such as the transfer of liquid between two separating surfaces and the entrainment of air in high-speed coating processes.
Interfacial instabilities: Instabilities at interfaces are usually undesirable in materials processing operations, but can sometimes be exploited for scientific and technological purposes (e.g., creating a topographically patterned surface). These instabilities can be driven by a variety of sources, including hydrodynamic, electrostatic, and intermolecular forces. We are interested in characterizing when and how interfacial instabilities occur, and in developing ways to control them.
Interfacial flows of suspensions: The successful large-scale manufacture of emerging products in the energy and electronics industries requires that particulate suspensions be coated and printed at high speeds with minimal defects. By combining ideas from colloidal rheology and interfacial fluid mechanics, we are examining a number of model problems in this area.
Polymer dynamics near surfaces: The behavior of polymers near surfaces plays a key role in a variety of applications including biosensors, suspension rheology, and the development of novel nanostructured materials. In many cases, the surface may be patterned chemically and/or topographically, and fluid flows and electric fields may be present. We are applying Brownian dynamics simulations to study how fluid flow, electric fields, and surface patterning can be designed to manipulate the behavior of macromolecules near surfaces. Various molecular theories are leveraged to guide the simulations and to understand the results.
- Liquid Transfer in Printing Processes: Liquid Bridges with Moving Contact Lines, Annu. Rev. Fluid Mech. 47, 67-94 (2015).
- Characteristics of Air Entrainment during Dynamic Wetting Failure along a Planar Substrate (with E. Vandre and M. S. Carvalho), J. Fluid Mech. 747, 119-140 (2014).
- Electrohydrodynamic Deformation of Thin Liquid Films near Surfaces with Topography (with A. Ramkrishnan), Phys. Fluids 26, 122110 (2014).
- Forced Spreading of Films and Droplets of Colloidal Suspensions (with L. Espín), J. Fluid Mech. 742, 495-519 (2014).
- Sagging of Evaporating Droplets of Colloidal Suspensions on Inclined Substrates (with L. Espín), Langmuir 30, 11966-11974 (2014).
- On the Mechanism of Wetting Failure during Fluid Displacement along a Moving Substrate (with E. Vandre and M. S. Carvalho), Phys. Fluids 25, 102103 (19 pages) (2013).
- Dynamics of Polymer Adsorption from Dilute Solution in Shear Flow near a Planar Wall (with S. Dutta and K. D. Dorfman), J. Chem. Phys. 139, 174905 (8 pages) (2013).
- Electrohydrodynamic Instabilities in Thin Viscoelastic Films--AC and DC Fields (with L. Espín and A. Corbett), J. Non-Newtonian Fluid Mech. 196, 102-111 (2013).
- Onset of Whipping in the Melt Blowing Process (with C. Chung), J. Non-Newtonian Fluid Mech. 192, 37-47 (2013).
- Worst-case Amplification of Disturbances in Inertialess Couette Flow of Viscoelastic Fluids (with B. K. Lieu and M. R. Jovanovíc), J. Fluid Mech. 723, 232-263 (2013).