Weeks Lab Home -- People -- Experimental facilities -- Publications -- Experimental pictures -- Links

Dr. Eric R. Weeks

Professor, Department Chair
Ph.D., University of Texas at Austin, 1997

My web pages:
Research: Lab home page
Vitae (PDF)
My research interests
Publications & past projects
Teaching: squishy materials, sci. ed. journal club, misc.
Pictures: computer generated, quasicrystals
Other: about me, software, particle tracking, links

Contact information:
Voice: (404) 727-4479
FAX: (404) 727-0873
Email: erweeks(at)emory.edu
USmail Department of Physics (use this for US or campus mail)
Mail stop 1131/002/1AB
400 Dowman Dr.
Emory University
Atlanta GA 30322-2430
Office: Math/Science Center N250 (do not use for campus mail)
Labs: 347, 350, & 360 Emerson Hall
(404) 712-8669, -8670

Useful links: Emory University | Emory College | Registrar | Directory
Physics Department | Directory | Colloquium | Class info


Research Interests

Microscopy of colloidal glasses

Suspensions of densely packed colloidal particles are a simple model system which exhibits a glass transition, as the packing of the particles is increased. I use confocal microscopy to directly see the motions of individual colloidal particles, in order to determine how the microscopic motion of the particles is constrained as the glass transition occurs. This allows me to gain unique insights into the glass transition in a fashion impossible for regular glasses.

My previous work studied the microscopic phenomena found in equilibrated "supercooled" colloids, that is, systems that were near the glass transition but not actually glassy. A new problem I study is aging: glassy systems are out of equilibrium, and are continually evolving, albeit extremely slowly. Moreover, this aging behavior is dependent on how the glass is formed (for example, it depends on the cooling rate; in a colloidal system this would be the rate at which the density is increased). This has relevance for problems such as the shelf-life of plastics (solid plastic objects are polymer glasses). By using confocal microscopy we directly look at the microscopic motions of the particles in an aging colloidal glass.

[confocal sketch]
(How a confocal
microscope works)

colloidal
particles
(2 micron diameter
colloidal particles)

Also, as a physicist, I enjoy poking systems to see how they respond. How does a colloidal glass respond when locally perturbed? This sort of question has been asked for theoretical glassy systems; I study this problem using colloids. This may also help shed light on experiments with molecular glasses where perturbations were indirectly studied, but where the microscopic details were unmeasurable.

Nonlinear dynamics, complex fluids, and granular media

Why does mayonnaise act both like a liquid and a solid? What causes shaving cream to flow differently from toothpaste? These types of questions are at the heart of soft condensed matter, the study of materials with both fluid and solid properties (often called "complex fluids"). Moreover, the mechanical properties and ability to flow are in fact the defining features of soft materials, and are key to the practical utility of soft materials. The answers to these questions relate the mesoscopic structure of a complex material to its macroscopic properties (such as its viscoelastic modulus). With the wide variety of mesoscopic structures, it might be expected that the answers would depend strongly on the details of each material, and that the study of such systems would be the study of many special cases. However, recently the analogy of jamming suggests the possibility of universal behavior of complex fluids under stress, and in particular, that such systems may behave like granular media. In each case, the material behaves in many ways like a solid. The analogy of jamming depends on the microscopic behavior of such systems, yet there is little experimental evidence to support the analogy apart from macroscopic similarities between these systems.

Jammed systems are defined as systems with random structures which internally rearrange under imposed stress, so that a subset of the internal structure resists the stress; the formation of these stress-supporting regions is entirely due to the external stress. I plan to use confocal microscopy to examine the structure of complex fluids and granular systems under shear flow, to see if indeed there are microscopic similarities, and to determine if jamming is an appropriate description for any or all of these systems. Moreover, the microscopic dynamics of shear thickening colloids, colloidal glasses, and shear flow of granular systems, are interesting problems in their own right. If the theory of jamming evolves to describe these diverse phenomena, it will be because of a comprehensive and detailed experimental understanding of the microscopic dynamics in each system.

Opportunities

Undergraduate and graduate students who are interested in working in my lab during the school year or the summer should contact me at weeks/physics.emory.edu if you have any questions. For people at Emory, I'm in Emerson 309/350, so come say hello. You may be interested in seeing pictures of our laboratory in Emerson Hall, which opened in January 2001.

[lab]


Links


©1996-2007 Physics Department, Emory University.
These pages may be freely distributed if unmodified.
For more information, contact: weeks/physics.emory.edu