Rheology, Interfacial Rheology, Microscopy, Microfluidics
National Research Council Fellowships
- Microfluidics for characterization of complex fluids
- colloid rheology of shaped particles
In the Fluid Suspensions and Emulsions Project, we are developing rheological measurement and data analysis methods to help take colloidal rheology beyond uniformly charged spheres to particles with more complex interactions.
Small Volume Rheology
The synergistic combination of morphology and rheology is instrumental for exploiting complex fluids, and is fundamental to polymer science. The Polymers and Complex Fluids Group is therefore developing methods to advance these measurement sciences. I am interested particularly in colloids, proteins, surfactants, interfacial phenomena and structure development. Through microfluidic device design, we (in the Fluid Suspensions and Emulsions project) control flow (type and strength) and measure fluid properties, aided by microscopic observations.
I also contribute to the Organic Electronics and Photovoltaics Project, in which we are exploring morphology development in organic electronic materials.
Liquid drops undergoing extensional flow and deformation. The interfacial tension is measured by tracking drop position and shape (with Joao Cabral, Lab on a Chip).
The flow inside droplets (indicated by particle tracers) measures the interfacial mobility to dilatational (1st schematic) and shear deformations. This work is the foundation of a micro interfacial rheology method (with Jeff Martin, Kendra Erk, Fred Phelan, and Jonathan Schwalbe, Soft Matter).
An orientation map derived from dark-field TEM showing half-integer disclinations (with Xinran Zhang and Dean Delongchamp, Advanced Functional Materials). The color wheel identifies the orientation, and dislcinations are points where all of the colors converge. At positive disclinations (schematic at right) the colors appear in the same sequence as the color wheel (e.g., mapping counter clockwise around the disclinations the colors appear in the sequence: yellow, red, purple, blue).For negative disclinations the sequence is opposite. Six disclinations are circled; others are also present. A recent review that highlighted this work appeared on the cover of the Journal of Polymer Science Polymer Physics, July 2011; (The cover image is from the author of the review, Christopher McNeill).
TEM micrograph of polyelectrolyte multilayers and particle adsorption, as part of a step-by-step process metrology for particle lithography. This process produces patchy particles which aggregate in fluid suspensions (with Thuy Chastek, Langmuir).
Recent Invited Presentations
"Thin Film Morphology of Organic Electronic Materials," Northwestern U., Materials Science Department, November 16, 2010
"Career at a Government Lab," U. Akron, Research Experience for Undergraduates Seminar, August 3, 2010
"Microfluidics to study transport phenomena," S. D. Hudson et al., U. Akron, Polymer Science Seminar, August 3, 2010
"Microfluidics to study transport phenomena," U. Maryland, Chemical and Biomolecular Engineering Seminar, April 27, 2010.
"Microfluidic methods to measure surfactant dynamics," Procter and Gamble, April, 2010.
"Thin film morphology of organic electronic materials," Symposium in honor of Andrew Lovinger, American Chemical Society, San Francisco, March, 2010.
"Interfacial rheology," Mid-Atlantic Soft Matter Workshop, Johns Hopkins U, November, 2009.
"Polyelectrolyte and particle adsorption to nanopatterned surfaces", American Chemical Society, National Meeting, Colloid & Surface Science, Washington, DC, August, 2009.
"Rolling and Stretching; dynamical characterization of complex fluids", Physics Colloquium, Georgetown University, February, 2008.
"Microfluidic Methods for Emulsion and Particle Characterization,"2nd International Symposium on Polymer Materials Science, December, 2007.
"Microfluidic Methods for Emulsion and Particle Characterization," Gordon Research Conference on Polymer Colloids, Tilton, NH, June, 2007.
"Structural Analysis and Fluid Properties of Supramolecular Assemblies," American Physical Society, March Meeting, Denver, CO, March, 2007.
Awards and Honors: