Complex Fluids/Nonlinear Dynamics Laboratory

Prof. Eric R. Weeks, Physics Department, Emory University

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Suspensions of densely packed colloidal particles are a simple model system which exhibits a glass transition, as the concentration of the particles is increased. We use confocal microscopy to look at the particles and determine how their motion changes as the glass transition occurs. We study these materials in situations including flow through tubes and being poked with tiny magnetic beads. These experiments give us insights into the glass transition in a fashion impossible for regular glasses.

We also study the properties of other complex materials, including foams and sand. See below for information about our various projects.

Current Projects:

Microscopic colloidal flow
Diffusion along interfaces
Poking colloids with magnets
Confined colloids
Aging of colloidal glass
Local structure in aging glasses
Diffusing rods
Emulsion glasses
Colloidal gels

Tutorials and other information:
Directions to our lab
Physics of colloidal glass
Pictures of our lab
Tutorial on particle tracking
How a confocal microscope works

Diffusing rods We look at the Brownian motion of rods tumbling and drifting in 3D. What does their motion tell us about the viscoelastic properties of their medium?	Confinement and the glass transition The glass transition is modified in confined spaces, but it's unclear why. We're studying colloidal particles confined between two parallel walls; we find their motion slows down.
Aging of colloidal glasses Glasses are nonequilibrium systems, and as such, their properties are constantly evolving. We look for the microscopic details of this evolution.	Tetrahedral structure in aging colloids As colloidal glasses age, does their structure change? We find not, but that the local structure is correlated with the dynamics of the particles.
Microrheology of interfaces Is the interface between oil and water a truly two dimensional object, or are three dimensional effects important for microscopic motion along the interface? What about soap films?	Microscopic behavior of flowing colloids We're studying the behavior of colloids as they flow through tiny tubes. As they flow faster, the apparent viscosity decreases. What is the microscopic behavior responsible for this?
Emulsion glasses We visualize how droplets deform in a concentrated emulsion. In some circumstances emulsions can act like a glass, and studying the deformed droplet shapes should help us understand the emulsion glass transition.	Poking colloids with magnets We put small magnetic beads into colloidal glasses and pull on them with really strong neodymium magnets. How does this disturb the particles?
Structure of colloidal gels We're studying the structure and dynamics of colloidal gels. How does the gel change when we vary the stickiness of the particles?

PAST PROJECTS
	Draining water from foam: As water flows between bubbles in a foam, does it flow like regular flow through a pipe? We found that it depends on the type of soap used to make the foam. Work done in collaboration with Stephan Koehler.
NASA PCS-3 -- study of aging

FUNDING:

University Research Committee of Emory University (Spring '07 award).
NASA microgravity fluid physics (NAG3-2728) & PECASE
CAREER grant from NSF (DMR-0239109)
Materials World Network grant from NSF (DMR-0603055)
2/02 - 8/04: The Petroleum Research Fund, administered by the American Chemical Society (37712-G7)

1/02 - 2/03: University Research Committee of Emory University (Fall '01 award).

Any opinions, findings, and conclusions or recommendations expressed in this website are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Nor anybody else's views, for that matter, just us.