This dynamic data will help determine the boundary conditions for future models of critical
behavior. Present observations also include a determination of the shape of the interface and
which part of the sample wets the cell.
The long-term observation of which samples phase-separate will allow precise determination of
the critical point of this colloidal mixture and will allow inference of the fundamental physics
underlying critical point behavior.
The BCAT Critical Point samples are comprised of colloids and polymers diffusing in a
background solvent; this model system mimics the behavior of molecular liquids and gases in
microgravity. The network structure that appears in the phase separation images has a
characteristic length scale. How this length changes with time gives insight into the
thermodynamics driving the phase separation and can be quantified using image correlation
(an optical method that employs tracking and image registration techniques for accurate 2- and
3-dimension measurements of changes in the length) computer programs. By creating different
program coding, running in parallel with various computing platforms, many orders of
magnitude improvement in analysis speed were achieved over standard “off-the-shelf”
programs. The speed increases allow for very rapid analysis of images downlinked from the ISS
and quick advantageous feedback to astronauts in orbit in time to make changes while the
experiment is still running (Lu 2009, 2010).
PUBLICATION(S)
Lu PJ, Oki H, Frey CA, et al. Orders-of-magnitude performance increases in GPU-accelerated
correlation of images from the International Space Station. Journal of Real-Time Image
Processing. 2010;5(3):179-193. doi: 10.1007/s11554- 009 -0133-1.
Lu PJ, Weitz DA, Chamitoff GE, et al. Long-time observation of near-critical spinodal
decomposition of colloid-polymer mixtures in microgravity. 47th Aerospace Sciences Meeting
and Exhibit, Orlando, FL; 2009.
Lu PJ, Weitz DA, Foale CM, et al. Microgravity phase separation near the critical point in
attractive colloids. 45th Aerospace Sciences Meeting and Exhibit, Reno, NV; 2007.
This investigation is complete; however additional results are pending publication.