Research Interests

The objective of my research is to quantify the relationship between molecular-level interactions and macroscopic fluid behavior. We have developed experimental tools and techniques for systematically controlling molecular-level behavior, characterizing nanoscale and microscale structure in fluid systems and quantifying rheology and flow behavior of complex fluids.

Part of our research focuses on design and control of nanoscale structure in complex fluid systems. Using a combination of synthesis and manipulation of colloidal interactions, we are developing novel soft materials. An example is our work with elongated, or wormlike, micelles based on ionic surfactants. Variation of counterions allows us to control the rheology and phase behavior of these materials for a variety of applications. Further adaptation of counterion chemistry allows us to utilize these nanoscale structures as templates for generation of amphiphilic rod-like nanoparticles. Another example is our recent work on using the structure inherent in block copolymers to develop spatially-structured nanocomposities. Our understanding of the formation of these nanocomposites will allow for development of applications in separation, delivery and protein stabilization.

A second focus of my research is on the impact of viscoelasticity on deformable interfaces under flow. Many industrial processes including ink-jet printing, spraying, and blending involve deformable liquid-vapor or liquid-liquid interfaces. In all of these processes, colloidal and polymeric fluid additives add elasticity to fluids and, hence, add a second elastic behavior with very different timescales than those inherent to the interfacial process. We are working to determine the role of fluid elasticity on these complex processes. Current work focuses on a fundamental study of how polymeric solutions wet solid surfaces and on an applications-based study of how protein additives alter inkjet printing in the formation of three-dimensional biomimetic materials.

Representative Publications

"Shear orientation of nanoparticle arrays templated in a thermoreversible block copolymer micellar crystal," D. C. Pozzo and L. M. Walker, Macromolecules 40(16):5801-10 (2007)

"Solution behavior of rod-like polyelectrolyte surfactant aggregates polymerized from wormlike micelles," D.M. Kuntz and L. M. Walker, J. Physical Chemistry B 111(23):6417-6424 (2007)

"Dynamic Wetting of Boger Fluids," Y. Wei, G. K. Seevaratnam, S. Garoff, E. Ramé and L. M. Walker, JCIS 313:274-280 (2007)

"Quantifying Air-Atomization of Viscoelastic Fluids through Fluid Relaxation Times," Y. Christanti and L. M. Walker, Atomization & Sprays 16(7):777-790 (2006)

"Controlling Dimensions of Polymerizeable Micelles: Micelle Template versus Reaction Conditions," M. J. Gerber and L. M. Walker, Langmuir 22:941-948 (2006)

"Dose-Dependent Cell Growth in Response to Concentration Modulated Patterns of FGF-2 Printed on Fibrin," E. D. Miller, G. W. Fisher, L. M. Walker, L. E. Weiss and P. G. Campbell, Biomaterials 27:2213-2221 (2006)

"Shear Induced Gelation of Laponite-PEO Mixtures," J. Zebrowski, V. Prasad, W. Zhang, L. M. Walker and D. A. Weitz, Coll. Surf. A 213(2-3):189-197 (2003)

"The Formation of an Irreversibly Adsorbed and Organized Micelle Layer at the Solid-Liquid Interface," S. Biggs, S. R. Kline and L. M. Walker, Nanoletters 2(12):1409-1412 (2002)