Binary Colloidal Alloy Test - 5: Three-Dimensional Melt (BCAT-5-3D-Melt) - 08.18.16
The Binary Colloidal Alloy Test 5: Three-Dimensional Melt (BCAT-5-3D-Melt) experiment crystallizes and melts tiny particles suspended in liquids, known as colloids, onboard the International Space Station where there is no gravity. The colloidal particles are designed to melt when the temperature of the liquid is raised. Crewmembers observe and photograph the particles as their sizes change when subjected to small temperature adjustments.
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Information Pending Experiment Details
Arjun Yodh, Ph.D., University of Pennsylvania, Philadelphia, PA, United States
ZIN Technologies Incorporated, Cleveland, OH, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
April 2009 - March 2010; September 2010 - March 2013
The predecessors to BCAT-5, BCAT-3 and BCAT-4 are in operation on the ISS.
- Binary Colloidal Alloy Test - 5: Three-Dimensional Melt (BCAT-5-3D-Melt) is one of four investigations in the BCAT-5 suite of experiments. BCAT-5-3D-Melt utilizes sample 10 in the BCAT-5 hardware.
- BCAT-5-3D-Melt takes advantage of the microgravity environment on the ISS to prevent the colloidal particles in these samples from encountering sedimentation, convection, and gravitational jamming utilizing temperature-sensitive polymers and microgel particles to tune soft matter through melting and crystallization transitions.
- The BCAT-5-3D-Melt documents changes in particle size and sample volume fraction which cause the sample to move in and out of the crystalline regime during International Space Station (ISS) cabin temperature changes over a two-week period.
The Binary Colloidal Alloy Test - 5 (BCAT-5) hardware supports four investigations. Samples 1 - 5, the Binary Colloidal Alloy Test - 5: Phase Separation (BCAT-5-PhaseSep) will study collapse (phase separation rates that impact product shelf-life). In microgravity the physics of collapse is not masked by being reduced to a simple top and bottom phase as it is on Earth. Samples 6 - 8, Binary Colloidal Alloy Test - 5: Compete (BCAT-5-Compete) will study the competition between phase separation and crystallization, which is important in the manufacture of plastics and other materials. Sample 9, Binary Colloidal Alloy Test - 5: Seeded Growth (BCAT-5-SeededGrowth) will study the properties of concentrated systems of small particles when 99.8% are identical 0.36 diameter micron spheres and 0.2% are 4.14 microns in diameter (11.5x larger); these seed particles may cause heterogeneous crystal growth. Sample 10, Binary Colloidal Alloy Test - 5: Three-Dimensional Melt (BCAT-5-3D-Melt) will look at the mechanisms of crystal formation and 3-dimensional melting using colloidal particles that change size with temperature.
The BCAT-5-3D-Melt sample will consist of a monodisperse nearly-hard-sphere colloidal suspension near its crystallization point. For this investigation small temperature changes that change the particle volume fraction will move the equilibrium system towards and away from the melting transition. The key ingredient in these samples is a thermosensitive polymer, poly(N-isopropylacrylamide (NIPA); the temperature-sensitive character of the samples stems from the temperature dependent solubility of NIPA polymer in water. Below its theta temperature (the temperature at which the coiled polymer molecules expand to their full contour lengths and become rod-shaped) of approximately 31 degrees C, water is a good solvent and NIPA polymer assumes a swollen coil form; in this regime a small increase of temperature increases monomer-monomer attractions and thus the size of the isolated polymer decreases. Above the theta temperature, water is a poor solvent and NIPA has a collapsed globule form.
The BCAT-5-3D-Melt experiment will simply record sample temperature and observe (by photography) whether the sample crystallizes, noting at what temperature the sample experiences the fluid-solid transition. This information will be also be useful for future experiments planned for ISS.
The BCAT experiments can only take place in a microgravity environment, because gravitational forces alter the nature of the crystallization and melting processes. BCAT-5 gives scientists insight into how the size of particles affects their ability to organize into crystal structures. A better understanding of this phenomenon could lead to manufacturing improved materials and products for space applications.
Colloidal engineering uses small particles suspended in liquid to create materials with new properties. A greater understanding of colloids could improve product designs for consumer products, household goods, food and industrial applications.
Operational Requirements and Protocols
Decadal Survey Recommendations
Applied Physical Science in Space AP5
Fundamental Physical Sciences in Space FP1
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Binary Colloidal Alloy Test - 3 (BCAT-3)
NIH BioMed-ISS Meeting Video Presentation, 2009—BCAT-5-3D-Melt
NIH BioMed-ISS Meeting, 2009—BCAT-5-3D-Melt
NASA Image: ISS016E027863 - Astronaut Dan Tani photographing the BCAT-3 Sample Module using his own design for a ceiling mount in Node 2 of the International Space Station. Great high contrast pictures of difficult-to-capture images resulted from using this setup (February 2008).
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NASA Image: ISS025E008239 - NASA astronaut Shannon Walker, Expedition 25 flight engineer, uses a digital still camera to photograph Binary Colloidal Alloy Test-5 (BCAT-5) experiment samples in the Kibo laboratory of the International Space Station.
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