NASA Physics of Colloids in Space - 3 (PCS-3) Project

Emory University (Atlanta, Georgia, USA) and Université Montpellier 2 (Montpellier, France)
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NASA

People involved:

    Emory/Montpellier collaboration:
  • Eric R. Weeks -- Principle Investigator (Emory University)
  • Luca Cipelletti -- Co-Investigator (Université Montpellier 2)
  • Gianguido Cianci (Emory)
  • Rachel Courtland (Emory)
  • Christina Wallace (Emory)

    Other PCS-3 Principle Investigators:

  • David A. Weitz (Harvard)
  • Michael J. Solomon (University of Michigan)
PCS-3 logo

Overview:

This project has been cancelled. The intention of these NASA-sponsored experiments was to study colloidal suspensions in microgravity conditions, on the International Space Station. Our particular question was the behavior of binary colloidal glasses in microgravity. Glasses show aging behavior: their properties slowly change over time, which we have been studying already on Earth. Our objectives for the microgravity studies were:
  1. Study the influence of microgravity on colloidal glasses. NASA's previous two microgravity studies of monodisperse colloidal glasses were thwarted by unexpected difficulties with crystallization. We planned to study a mixture of two sizes of particles, choosing the sizes and relative concentrations to prevent crystallization. This would highlight differences between colloidal glasses on Earth and in microgravity that were previously masked by the microgravity-related crystallization.
  2. Study heterogeneous dynamics in an aging system over a much longer range of time scales than previously accessible. Earth-based experiments are inherently limited by sedimentation effects; invariably the sample begins to change due to sedimentation before long time scales are reached. It is precisely the asymptotic, long-time behavior that is most interesting in studies of aging.
  3. Clarify similarities and differences of aging materials. Our current work (at Emory) focused on monodisperse colloidal glasses on Earth, and Dr. Cipelletti's work has studied colloidal gels. This proposal extended these studies to binary hard sphere samples.
There were two other projects associated with PCS-3; see the web pages of David A. Weitz and Michael J. Solomon for more details.

Experimental Apparatus:

The PCS-3 apparatus has been used before. Click here for details of the apparatus.

Questions:

  1. What are the ensemble dynamics associated with an aging colloidal glass?
  2. What is the nature of the glass?
  3. How do the properties depend on the details of the binary system?

Experiments:

  1. Look at aging dynamics -- LAD, DLS on peaks of structure factor
  2. Look at structure of glass -- LAS
  3. Look for crystallinity -- HAS, SLS, images