ISS Science for Everyone
Science Objectives for Everyone
Binary Colloidal Alloy Test Low Gravity Phase Kinetics-Critical Point (BCAT-KP-Critical Point) helps materials scientists develop new consumer products with unique properties and longer shelf lives. Colloids are mixtures of small particles distributed throughout a liquid, which include milk, detergents and liquid crystals. Gravity affects how the particles clump together and sink, making the International Space Station an ideal platform to study their fundamental behaviors.
Science Results for Everyone
The following content was provided by Peter J. Lu, Ph.D., and is maintained in a database by the ISS Program Science Office.
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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)
National Laboratory (NL)
Earth Benefits, Scientific Discovery
ISS Expedition Duration
- September 2015
This BCAT builds and expands upon previous BCAT design heritage that includes:
BCAT-3 launched January 2004 on Progress 13 (Flight 13P)
BCAT-4 launched March 11, 2008 on Flight 1 J/A
BCAT-5 launched 8/28/2009 on Flight 17A
BCAT-6 launched 2/24/2011 on Flight ULF5
BCAT-C1 launched 7/211/2012 on Flight HTV-3.
BCAT-KP builds on the foundation of a decade of successful results with the BCAT series of experiments, looking at liquid-gas phase separation in a model colloid-polymer system, near the critical point. Fundamentally, gases are generally less dense than liquids of the same material; therefore, in the presence of gravity, phase separation is almost inevitably affected, often significantly, by sedimentation. Because these processes are slow--phase separation takes an infinite amount of time at the critical point--there is no way to observe the full course of phase separation in the presence of gravity, without having the process significantly affected by sedimentation. On ISS, however, one can observe these processes, for weeks and months, undisturbed in a unique microgravity environment.
BCAT-KP introduces several significant improvements. Incremental improvements to lighting and photography come as a result of lessons learned from previous experiments, and researchers expect to continually improve these aspects as an easy derivative of normal improvements in COTS photography hardware. More importantly are the plans to incorporate the results of a decade of ground experiments in sample synthesis and separation, allowing some of the system properties to be tuned much more carefully. In particular, researchers can design the colloidal liquid and gas to be nearly the same density; the best one can achieve of earth minimizes sedimentation over hours. By flying these new samples, researchers reach an effective nanogravity regime, and should be able to run our experiments for far longer--enabling closer probing of the critical points--than all previous experiments.
By probing the fundamental physics, researchers hope to provide greater insight to industry working on several practical problems. Most closely related is the design of consumer products, like fabric softener at Proctor and Gamble, where product stability relies on avoiding phase separation. More generally, by understanding and controlling these processes, researchers should be able to inform a number of fields and physical problems, from the flow of complex fluids, to the arrest of phase separation in the form of gels, covering industries from oil/energy, to food and consumer products.
For the proposed phase separation samples, the objective is to measure phase separation rates in microgravity (µ-g) and to develop an underlying theory for predicting critical point and critical point mapping. The first set of samples investigate the critical point of colloids and aim to build upon previous research by allowing for terrestrial samples to be buoyancy matched for greater accuracy in correlations. Researchers intend to photograph initially randomized colloid samples to determine their resulting structure over time. Theory tells that the rate of phase separation can be adjusted by changing the amount of polymer in the solution of polymethyl methacrylate (PMMA) spheres. Doing this adjusts the depletion attraction force between particles. This gives a window into the underlying physics that is not open to scientists on Earth where only a top and bottom phase is visible. The results are of particular relevance to product manufacture and nano-phenomena such as self-assembly.
A fundamental understanding of the underlying physics that is needed to stabilize everyday commercial products may enable product formulations with enhanced performance and stability, while simultaneously lowering the cost of manufacture. That is, for commercial products, researchers can look at the rate of phase separation as a function of the vesicle concentration. Adding more vesicles inhibits phase separation and increases product shelf live, but at a price. It costs more to make the product and additional materials are being added for reasons other than which the product was created. Through the understanding and development of material formulation models one can determine the underlying physics of a product, and enhance its performance while decreasing its manufacturing cost (a win-win situation).
The work with ellipsoidal and platelet particles addresses geometry dependence of glasses and liquid, where scientists expect that work with non-spherical particles will lead to the discovery of new liquid crystalline phases and in general to new condensed phases of matter with various commercial applications. Traditional questions about the relative packing fractions, which crystallization phase is manifested, and the passing from one phase to the other, may be studied in these systems without the perturbing effects of sedimentation and gravitational jamming. With regard to the commercial potential of the proposed crystal samples, colloidal nucleation experiments seek to find an understanding of the most fundamental liquid/solid transition. Growth of ordered colloidal phases has attracted interest in a number of areas, e.g. ceramics, composites, optical filters and photonic band gap materials. Being able to test the enhanced strength and directional properties of ellipsoidal crystals that may only grow in microgravity will determine if it is worth pursuing microgravity production capability.
In addition to the commercialization potential and application of the information generated from the sample investigations, there is commercial potential of the microgravity colloidal or material sample hardware itself. P&G spent a considerable amount of time with LANL and UCSB with high-powered computers to try and model the behavior that is being explored during the BCAT investigation with no considerable success. This opportunity could provide empirical information to track and record the evolution of a colloidal sample behavior over time to anchor these models and verify predictions and new product solutions and performance to design expectations.
It is believed that the commercial value coupled with the ability to quickly fly samples in a cost competitive manner and on a continuous basis provides a commercially viable service to many industries developing or utilizing particle additives in their products. It is also believed that hardware such as the BCAT-LGP coupled with a reduction in launch cost and cycle times has tremendous commercial potential.
ZIN along with the research team believe there is commercial interest for soft matter investigators and commercial providers of these materials to pay for ISS investigation opportunities using the BCAT-LGP capability.
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Colloidal mixtures form small blobs in microgravity, rather than the clear separation between top and bottom layers that occurs on Earth. Studying the formation of these blobs can provide insight into the physics of colloids in a manner that would not be possible on Earth. The investigation also lays a foundation for future nanotechnology and nano-mechanical systems research in microgravity, as well as potential future microgravity production of colloidal mixtures.
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From milk to soap, colloidal mixtures can spoil when solid particles sink and clump together inside a liquid. Adding extra particles stabilizes the mixture, but this is expensive and inefficient. Changing particle shapes and sizes also affects a mixture’s stability, but it is important to study the influence of these particles without gravity interrupting the separation process. Investigations with the BCAT-KP hardware provide insight into the microgravity kinetics of different colloidal particle shapes and volumes. These results will improve computer models designed to simulate colloidal behavior in microgravity. The findings could also yield new consumer products, including some that might be manufactured in space, that will cost less to produce and last longer.
Operational Requirements and Protocols
BCAT consists of a set of ten small samples of colloidal particles. The BCAT samples are each contained within a small case the size of a school textbook. The experiment requires a crew member to set up the experiment using a handrail/seat track configuration, ISS Laptop and the Kodak 760 or Nikon D2Sx camera to take digital photographs of the samples at close range. The pictures are down-linked to investigators on the ground for analysis.
The current plan for this experiment is to conduct it over a 7 or 14-day session, each of which can be run incrementally and require a minimum amount of crew time due to powering the digital camera with the new AC power available through the inverter to be available in 2012; a third session to mix and photograph all 10 samples and then a fourth session, prior to the increment completion and bringing the samples down for the next increment set of hardware, to photograph all ten samples which is slotted to take a minimal amount of crew time. As such, new information will undoubtedly be learned, and the nature of the experiments conducted will evolve to take advantage of this new information.
Session 1: Set up hardware, take baseline photos of all ten samples; homogenize samples 6-10 then samples 9 and 10, then automatically photograph sample 1 (using EarthKAM software on laptop) every hour for 7 days. Perform sample 1 daily status check each day. After seven-day run, perform crystal search/photography on 6-10. Homogenize sample 2, automatically photograph sample 2 (using EarthKAM software on laptop) every hour for 7 days. Perform sample 1 daily status check each day. After seven-day run, perform crystal search/photography on 6-10. If necessary, tear down after operations are complete but keeping setup intact is preferred to save crew time.
Session 2: Set up hardware, homogenize samples 3, 4 and 5 one at a time then automatically photograph each sample (using EarthKAM software on laptop) every hour for 14 days each. Perform Crystal Check and Photography procedures on 6-10 if crystals not found/photographed in Session 1. If necessary, tear down after operations are complete but keeping setup intact is preferred to save crew time.
Session 3: Homogenize and photograph samples 1-10 (using EarthKAM software on laptop) and stow sample module for six months. The experiment is torn down after operations are complete.
Session 4: At end of increment after homogenization, manually photograph samples 1 through 10. Re-stow sample moduled tear down after operations are complete.
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Decadal Survey Recommendations
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Binary Colloidal Alloy Test (BCAT)
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NASA Image: ISS040E013856 - NASA astronaut Reid Wiseman conducts a session with the Binary Colloidal Alloy Test (BCAT) experiment.
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NASA Image: ISS038E031151 - Close-up view of a BCAT-KP hardware setup in the Japanese Experiment Module (JEM).
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