Lynn M. Walker-Chemical Engineering - Carnegie Mellon University

Lynn M. Walker

Professor, Chemical Engineering and Chemistry (Courtesy) and Material Science and Engineering (Courtesy)

Office: Doherty Hall A220
Phone: 412-268-3020
Fax: 412-268-7139

Bio

Professor Lynn Walker is currently Professor of Chemical Engineering with courtesy appointments in Chemistry and in Materials Science & Engineering. Prof. Walker received her BS Chemical Engineering degree from the University of New Hampshire in 1990 and her PhD from the University of Delaware in 1995, under the supervision of Norman Wagner. After holding a postdoctoral position at Katholieke Universiteit Leuven, Leuven Belgium, Prof. Walker joined Carnegie Mellon's Department of Chemical Engineering in 1997. Prof. Walker was a Visiting Professor during a sabbatical at Polymer IRC, University of Leeds in 2007.

Education

Ph.D., 1995, University of Delaware
B.S., 1990, University of New Hampshire

Research

Research Interests

Research in the Complex Fluids Rheology group focuses on understanding and controlling complex, or structured, fluids in engineering applications. Our work is primarily experimental and involves rheometric characterization, classical colloid and macromolecular analytical techniques, small-angle scatterning and microfluidic tools. We collaborate closely with others in the Center for Complex Fluids Engineering. Two main themes, Impact of Nanoscale Structure on Rheology and Behavior of Complex Systems with Fluid-Fluid Interfaces, run through the group and our interests lie in applying fundamental knowledge and ideas to real engineering situations.

Impact of Nanoscale Structure on Rheology: Relatively weak forces at the molecular level dictate the macroscopic properties, particularly the flow properties, of complex fluids. To effectively process and control these fluids, we need to understand the flow-structure relationship for different types of structured fluids and how molecular structure influences this coupling. While the intermolecular forces of importance act over nanometers, the structures formed span nanometers through microns; the timescales associated with response of these structures fall in the range of most processing flows. Work in the group combines rheology with scattering techniques to tackle and quantify the flow-structure coupling. A number of structured fluids have been considered by the group; liquid crystal polymers, polymer blends, surfactant mesophases, wormlike micelles and block copolymers. 
Behavior of Complex Systems with Fluid-Fluid Interfaces: Fluid-fluid interfaces deform readily in external fields and are sensitive to molecular transport from the bulk. Molecular adsorption to interfaces changes the interfacial tension and constitutive behavior of those interfaces. The response of a system containing fluid-fluid interfaces (emulsions, foams, bubbly liquids) to mechanical or other deformation is dependent on these interfaces. Earlier work on sprays, atomization, microfluidic droplet formation and polymer blends convinced us that there needs to be improved understanding of the details of the interfaces and mechanics. We have been developing devices and approaches to the characterization of complex interfaces and interfaces in contact with complex (i.e., nonNewtonian) bulk phases. Tools include microscopy, device development, soft lithography, and rheology.

Research Websites

Complex Fluids Engineering
Energy Science and Engineering

Awards and Honors

  • 2016 Barbara Lazarus Award
  • AIChE Fellow, 2016
  • 2015 AIChE Woman's Initiatives Committee (WIC) Mentorship Award
  • NSF Career Award, 2001
  • Kun Li Award for Excellence in Education, Carnegie Mellon University, 2000 and 2003
  • DuPont Young Professor, 2000-2001
  • NSF Postdoctoral Fellow, Katholieke Universiteit Leuven, Belgium, 1996
  • Departmental Teaching Fellowship, University of Delaware, 1994
  • Women of Excellence Award, University of Delaware, 1991

Publications

Selected Publications

Selected Publications

  1.   “Interfacial Tension Dynamics, Interfacial Mechanics, and Response to Rapid Dilution of Bulk Surfactant of a Model Oil–Water-Dispersant System,” M. D. Reichert and L. M. Walker, Langmuir 29 (6): 1857–1867 (2013)
  2. “Interfacial Dynamics and Rheology of Polymer-Grafted Nanoparticles at Air-Water and Xylene-Water interfaces,’’ N. J. Alvarez, T. Saigal, R. D. Tilton, S. L. Anna and L. M. Walker, Langmuir 28(21):8052-8063 (2012)
  3. “Using bulk convection to approach kinetic-limited surfactant dynamics,”  N. J. Alvarez, D. R. Vogus, L. M. Walker, and S. L. Anna, J. Coll. Interface Sci. 372:183-191(2012)
  4. “Comparison between Viscoelastic and Surfactant Dynamics in Flow Focusing Microfluidics,” W. Lee, L. M. Walker and S. L. Anna, Macromolecular Materials & Eng. 296:203-213 (2011)
  5. “A Microtensiometer to Probe the Effect of Radius of Curvature on Surfactant Transport to a Spherical Interface,” N. J. Alvarez, L.M.Walker and S. L. Anna, Langmuir 26(16):13310-19 (2010)
  6. “Stabilizing Biomacromolecules in Nontoxic Nano-structured Materials,” M. M. Domach and L. M. Walker, J. Assoc. Lab. Automation 15:136-144 (2010)
  7. “Structural Transition of a Surfactant-Polyelectrolyte Aggregate from a Cylindrical to String-of-Pearls Structure Induced by pH,” V. D. Lam and L. M. Walker, Langmuir 26(13):10489-96 (2010)
  8. “Nematic phases observed in amphiphilic polyelectrolyte-surfactant aggregate solutions,” D. M. Kuntz and L. M. Walker, Soft Matter, 4:286-293 (2008)
  9. “Multisegmented Block Copolymers by “Click” Coupling of Polymers Prepared by ATRP,” P. L. Golas, N. V. Tsarevsky, B. S. Sumerlin, L. M. Walker and K. Matyjaszewski, Australian J. Chemistry 60(6):400-404 (2007)
  10. “Controlling Dimensions of Polymerizeable Micelles: Micelle Template versus Reaction Conditions,” M. J. Gerber and L. M. Walker, Langmuir 22:941-948 (2006)
  11. “Engineered Spatial Patterns of FGF-2 Immobilized on Fibrin Direct Cell Organization,” P. G. Campbell, E. D. Miller, G. W. Fisher, L. M. Walker and L. E. Weiss, Biomat 26:6762-6770 (2005)
  12. “Rheology and Phase Behavior of Copolymer-Templated Nanocomposite Materials,” D. C. Pozzo, K. R. Hollabaugh and L. M. Walker, J. Rheology 49(3):759-782 (2005)
  13. “Dynamic Wetting of Inelastic Polymer Melts,” G. K. Seevaratnam, L. M. Walker, E. Ramé and S. Garoff, J. Coll. & Interface Science 284:265-270 (2005)
  14. “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)
  15. “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)
  16. “Rheology and Structure of Wormlike Micelles,” L. M. Walker, Current Opinion in Coll. & Interface Science 6(5-6):451-456 (2001)
  17. “Surface Tension Driven Jet Break Up of Strain-Hardening Polymer Solutions,” Y. Christanti and L. M. Walker, J. NonNewtonian Fluid Mech. 100:9-26 (2001)
  18. “SALS Analysis of Morphology Development of a Model Immiscible Polymer Blend in Transient Slit-Contraction Flows,” B.E.Priore and L.M.Walker, J.Rheology 45:383-402 (2001)
  19. “Controlling the Shear-Induced Structural Transition of Rod-like Micelles Using Nonionic Polymer,” M. T. Truong and L. M. Walker, Langmuir 16:7991-7998 (2000)
  20. “Orthogonal and Parallel Superposition Measurements on Lyotropic Liquid Crystalline Polymers”, L. M. Walker, J. Vermant, P. Moldenaers and J. Mewis, Rheologica Acta 39:26-37 (2000)
  21. “Shear-Thickening Dilute Surfactant Solutions: the Equilibrium Structure as Studied by Small-Angle Neutron Scattering,” R. Gamez-Corrales, J.-F. Berret, L. M. Walker and J. Oberdisse, Langmuir 15:6755-6763 (1999)

Full Publications