Crews were to photograph a two-component (binary) mixture of colloidal particles (tiny nanoscale spheres suspended in liquid) to document the formation of novel binary crystals not presently realizable on Earth. Results would help scientists develop fundamental physics concepts previously hindered by the effects of gravity. For example, binary alloy colloidal crystals are particularly promising candidates for photonic applications, in addition, they are of immense value as a model system for crystallization kinetics in multi-component systems. Unfortunately, this sample, number 7 of the ten BCAT-3 samples, dried out before crystallizing.Principal Investigator(s)
ZIN Technologies Incorporated, Cleveland, OH, United States
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)Research Benefits
Information PendingISS Expedition Duration
October 2003 - April 2004Expeditions Assigned
8Previous ISS Missions
The predecessor to BCAT-3, BCAT, flew on Mir in 1997 and 1998.
The Binary Colloidal Alloy Test-3 (BCAT-3) hardware supported three investigations in which ISS crews photographed samples of colloidal particles (tiny nanoscale spheres suspended in liquid) to document liquid/gas phase changes, growth of binary crystals, and the formation of colloidal crystals confined to a surface. Colloids are small enough that in a microgravity environment without sedimentation and convection, they behave much as atoms and so can be used to model all sorts of phenomena because their size, shape, and interactions can be controlled.
The BCAT-3 payload consists of ten small samples of colloid alloys in which the microscopic colloid particles are mixed together into a liquid. These ten samples are contained within a small case that is the size of a school textbook. At the start of an experiment run, all ten samples are shaken to completely remix the colloid samples, much in the same way that salad dressing must be shaken to remix oil and vinegar. After the samples are mixed, what remains is periodically photographed using a digital camera until the colloid and liquid components of those samples have separated or the polymers have formed crystals. The samples can be remixed to repeat the experiment.
The ten samples in BCAT-3 were selected as part of three separate experiments examining different physical processes: critical point, binary alloys, and surface crystallization. Sample 7 makes up the BCAT-3-BA part of the experiment and it is a binary alloy.
Colloids are also technologically interesting because they are the right size to manipulate light. Natural opal is likely the oldest and best known of the "photonic" crystals that direct light. Shine white light on the opal and a rainbow appears, demonstrating how colors of light are split up and sent in different directions. The ability to better control the movement of light is a major technological goal, not only to build computers operating on light instead of electricity but also to harness the full capabilities of existing fiber-optic networks for improving communications. Crystal structures built from only one building block, e.g., the arrangement of colloidal silica spheres in an opal, are well understood, but their optical properties are limited. More useful photonic crystals can be built from two different types of building blocks mixed together, yielding a binary alloy. The resulting structures and their optical properties are vast, as both the size and the proportion of the two building blocks can be varied. How crystallization is affected by these changes is only beginning to be explored. Theoretical studies suggest that desired optical properties require more complicated crystal structures, but this has not been well explored experimentally. Microgravity is crucial to the binary crystal experiments, allowing the growth of crystals far larger than those created on the surface of the Earth. The BCAT-3 binary alloy sample furthers previous investigations on binary growth in space.
This experiment addresses basic physics questions, but some of the areas may eventually have applications for space exploration. The binary alloy experiment provides information that may allow improvement of fiber optics and allow development of new computers that process data with light instead of electricity, thus avoiding deleterious heating, which enable higher component density.Earth Applications
Increased knowledge of some of the areas of this basic physical research may have future benefits in the application of the same physical processes on Earth. The binary alloy experiment provides information that may allow improvement of fiber optics and allow development of new computers that process data with light instead of electricity.
The BCAT-3-BA experiment is part of the BCAT-3 payload which consists of ten small samples of colloid alloys, the microscopic colloid particles all mixed together with a liquid. These ten samples are contained within a small case the size of a school textbook. The experiment requires a crew member taking digital photographs of the samples at close range. The pictures must then be downlinked to investigators on the ground for analysis.Operational Protocols
At the start of the experiment in Increment 8 all viable samples were mixed by using a magnet to run a magnetic stirbar up and down through the samples. This completely mixes and homogenizes the colloid samples. After the samples were mixed, the lights in the U.S. Lab are dimmed and photographs are taken to document the rate of crystallization for sample 7. These photographs are downlinked to the ground.
The sample dried out and was unavailable for experiments on ISS.
Manley S, Cipelletti L, Trappe V, Bailey AE, Christianson RJ, Gasser U, Prasad V, Segre PN, Doherty MP, Sankaran S, Jankovsky AL, Shiley B, Bowen JP, Eggers JC, Kurta CE, Lorik T, Weitz DA. Limits to Gelation in Colloidal Aggregation. Physical Review Letters. 2004; 93(10): 108302-1 - 108302-4. DOI: 10.1103/PhysRevLett.93.108302.