Binary Colloidal Alloy Test-5: Phase Separation (BCAT-5-PhaseSep) - 08.27.15
The Binary Colloidal Alloy Test 5: Phase Separation (BCAT-5-PhaseSep) experiment studies how microscopic particles suspended in a liquid separate from the liquid over time. Crew members photograph mixed colloid samples to measure the rate at which they separate. Reducing undesirable phase separation increases the shelf lives of household goods and consumer products.
Science Results for Everyone
There are some special conditions of pressure and temperatures in which a compound, such as water, has all three phases of gas, liquid and solid existing together. Similar phenomenon occurs with particles 1000 bigger than atoms floating in a liquid mixture. On Earth, things are weighed down by gravity, and this force interferes with phase separation, thus hindering its study. The Binary Colloidal Alloy Test (BCAT)-5-PhaseSep experiment photographs the formation of coexisting gas, liquid and solid phases of a colloidal system in microgravity. Surprisingly, large-scale separation of liquid, gas, and solid phases did not occur in microgravity because the surface tension between these phases is too weak to break the crystalline strands. A new crystal gel structure has been observed with colloidal crystals growing within the liquid phase on board the International Space Station. Experiment Details
Matthew Lynch, Ph.D., Procter and Gamble, Cincinnati, OH, United States
David A. Weitz, Ph.D., Harvard University, Cambridge, MA, United States
Peter J. Lu, Ph.D., Harvard University, Cambridge, MA, 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 1
April 2009 - March 2010; September 2010 - March 2013
Previous ISS Missions
The predecessors to BCAT-5; BCAT-3 and BCAT-4 are in operation on the ISS.
- The Binary Colloidal Alloy Test - 5: Phase Separation (BCAT-5-PhaseSep) experiment uses microscopic spheres (described as colloids) suspended in a liquid to serve as a large scale representation of the atoms and small molecules which constitute liquids (like oil and water) so that scientists can visualize what happens at the individual particle level when liquids separate from one another after being mixed.
- Results allow scientists to see some of the fundamental physics concepts that are behind the separation of different liquids in commercial products; these observations have been cloaked by the effects of gravity up to now.
- The BCAT-5-PhaseSep samples will be formulated using key components found in products like DownyTM. Many such products require expensive additives to ensure that they last for the stated shelf-life. A fundamental understanding of the underlying physics that is needed to stabilize these everyday products may enable a formulation with enhanced performance and stability, while simultaneously lowering the cost of manufacture.
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.
BCAT-5-PhaseSep is a follow-on experiment to BCAT-3, which has been performed on several ISS increments, since increment 8, and BCAT-4, which was begun during Increment 17. Fabric enhancers are composed of mixtures of vesicle and polymers which, in some cases, form weak particle gels. These gels often coarsen exhibiting sintering, cracking or collapse, which significantly reduce the product shelf life. The factors that contribute to coarsening are enigmatic, as the processes are often concealed by the gravitational compression of the gel. Microgravity experiments offer a unique opportunity to elucidate coarsening mechanisms in these weak gel systems.
The BCAT-5-Phase Separation experiments explores multi-phase separation which can be potentially applied to liquid waste recycling, coolant operations, and controlling the flow behavior of rocket fuel in future spacecraft.
Many household products require expensive additives that ensure particles do not separate from the liquid. Understanding this phase separation helps make household goods, such as fabric softener, with longer shelf lives and fewer additives. In the long term, the experiment aids in the development of next-generation computer technology, advanced optics, and medical technology.
The BCAT-5 experiment consists of ten small samples of colloidal particles. The ten BCAT-5 samples are contained within a small case the size of a school textbook. The experiment requires a crewmember to set up on the Maintenance Work Area (MWA) or on a handrail/seat track configuration, ISS Laptop and utilize EarthKAM software to take digital photographs of Samples 1 - 8 at close range using the onboard Kodak DCS760 camera. Camera Control Files for running the EarthKAM software can be uploaded from Earth to control the photography intervals (how many photographs per hour) and spans (run for how many days) once it is running. Samples 6 - 10, which may form crystals, require manual photographs (at least initially) be taken by a crewmember. The pictures are down-linked to investigators on the ground for analysis.
A crewmember sets up the video camera and BCAT-5 hardware (Slow Growth Sample Module, DCS760 Camera, pen-light source, flash and SSC Laptop with EarthKAM software) in the Maintenance Work Area (MWA) to document the BCAT-5 operations as performed on-board the ISS. The crewmember homogenizes (mixes) the sample(s) and takes the first photographs manually. This helps them optimize the setup and shows that the samples were initially fully homogenized when publishing results later. The EarthKAM software automates the rest of the photography session over a period of a few days to a few weeks. The crewmember performs a daily status check once a day (when time is available) to assure proper alignment and focus. At the completion of the run, the crewmember tears down and stows all hardware.
The BCAT-5-PhaseSep experiment has revealed the fundamental behavior of how a colloid-polymer mixture system having three phases (gas, liquid, and crystals) coexisting in equilibrium on board the International Space Station (ISS). By direct imaging in microgravity, scientists observe a unique structure, a ‘‘crystal gel,’’ that occurs when gas-liquid phase separation is arrested, or stopped, by crystallite formations spanning the liquid volume of the test cell. Formation of a crystal network by a two-step process, where the system initially forms a bicontinuous structure by spinodal decomposition and, subsequently, crystal nucleation occurs within the liquid domains, has been predicted previously theoretically and by simulations. Attempts to observe such a structure have been foiled by the onset of gravitational effects before crystallization starts. The unique structure found in this experiment opens new paths for future investigation and for the development of novel materials in the fields of cosmetics, food technology and pharmaceutical products, and may provide new insight into the phase diagram and crystallization of proteins.^ back to top
Sabin J, Bailey AE, Espinosa G, Frisken B. Crystal-Arrested Phase Separation. Physical Review Letters. 2012 November 9; 109(19): 195701 (5). DOI: 10.1103/PhysRevLett.109.195701. PMID: 23215400.
Ground Based Results Publications
Gopalakrishnan V, Schweizer KS, Zukoski CF. Linking single particle rearrangements to delayed collapse times in transient depletion gels. Journal of Physics: Condensed Matter. 2006 December 20; 18(50): 11531-11550. DOI: 10.1088/0953-8984/18/50/009. [December 20th]
Bailey AE, Poon WC, Christianson RJ, Schofield AB, Gasser U, Prasad V, Manley S, Segre PN, Cipelletti L, Meyer WV, Doherty MP, Sankaran S, Jankovsky AL, Shiley WL, Bowen JP, Eggers JC, Kurta CE, Lorik T, Pusey PN, Weitz DA. Spinodal decomposition in a model colloid-polymer mixture in microgravity. Physical Review Letters. 2007 Nov; 99(20): 205701-1 - 205701-4. DOI: 10.1103/PhysRevLett.99.205701. PMID: 18233160.
Lu PJ, Weitz DA, Foale CM, Fincke EM, Chiao LN, McArthur WS, Williams JN, Meyer WV, Owens JC, Hoffmann MI, Sicker RJ, Rogers R, Frey CA, Krauss AS, Funk GP, Havenhill MA, Anzalone SM, Yee H. Microgravity Phase Separation near the Critical Point in Attractive Colloids. 45th Aerospace Sciences Meeting and Exhibit, Reno, NV; 2007 January 4 pp.
Blijdenstein TB, van der Linden E, van Vliet T. Scaling behavior of delayed demixing, rheology, and microstructure of emulsions flocculated by depletion and bridging. Langmuir. 2004 December 21; 20(26): 11321-11328. DOI: 10.1021/la048608z. PMID: 15595753.
Manley S, Skotheim JM, Mahadevan L. Gravitational collapse of colloidal gels. Physical Review Letters. 2005 June 5; 94(21): 218302. DOI: 10.1103/PhysRevLett.94.218302.
Huh J, Lynch M, Furst EM. Microscopic structure and collapse of depletion-induced gels in vesicle-polymer mixtures. Physical Review E. 2007 November; E 76(5 Pt 1): 051409. DOI: 10.1103/PhysRevE.76.051409. PMID: 18233661.
Lu PJ, Zaccarelli E, Ciulla F, Schofield AB, Sciortino F, Weitz DA. Gelation of particles with short-range attraction. Nature. 2008 May 22; 453(7194): 499-503. DOI: 10.1038/nature06931. PMID: 18497820.
ISS Research Project-BCAT-PhaseSep
Experimental Soft Condensed Matter Group
NIH BioMed-ISS Meeting Video Presentation, 2009—BCAT-5-PhaseSep
NIH BioMed-ISS Meeting, 2009—BCAT-5-PhaseSep
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).
+ View Larger Image
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.
+ View Larger Image