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Experiment Overview


Brief Summary

The Binary Colloidal Alloy Test - 6: Colloidal Disks (BCAT-6-Colloidal Disks) experiments use microscopic particles (known as colloids) as models for studying the fundamental physics of a theoretically predicted, but until now unseen liquid crystal phase. Liquid crystals have many useful physical properties, such as being useful for switching colors (light) on and off in the thin-screen monitors used for many computers, tablets, and cell phones. The use of anisotropic (asymmetric) particles, like the colloidal disks used in this experiment, should produce a new material (cubatic) phase that is predicted to have orientational (directional) order, but no translational (position dependent) order.

Principal Investigator(s)

Arjun Yodh, Ph.D., University of Pennsylvania, University Park, PA, United States

Co-Investigator(s)/Collaborator(s)

Peter Yunker, Ph.D., University of Pennsylvania, University Park, PA, United States

Zexin Zhang, Ph.D., University of Pennsylvania, University Park, PA, United States

Developer(s)

ZIN Technologies Incorporated, Cleveland, OH, United States

Sponsoring Space Agency

National Aeronautics and Space Administration (NASA)

Sponsoring Organization

Human Exploration and Operations Mission Directorate (HEOMD)

Research Benefits

Information Pending

ISS Expedition Duration:

September 2010 - March 2014

Expeditions Assigned

25/26,27/28,29/30,31/32,33/34,35/36,37/38

Previous ISS Missions

The BCAT predecessors; BCAT-3 operated on ISS, and BCAT, operated on Mir in 1997 and 1998. BCAT-4 launched March 11, 2008 on 1J/A, and BCAT-5 launched June 13, 2009 on 2J/A.

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Experiment Description

Research Overview

• Sun glasses that contain polarizing lenses allow one type of light through (vertically polarized light) and block the other type of light (horizontally polarized light). The type of light that is blocked is the type most often reflected off of car bumpers, windshields, and the like. Liquid crystals can change one type of polarization into another and by doing so can either block or allow light to go through a display like those used in iPods and iPhones.



• The Binary Colloidal Alloy Test-6 (BCAT-6), colloidal disks experiment tests the organization of the molecular constituents of a new type of liquid crystal capable of rotating the polarization of light.



• The experiments relate to applications in the design of nanomaterials, new leading edge materials designed with molecular precision at the nanoscale.

Description

Scientists at the University of Pennsylvania have two samples which consist of suspensions of colloidal disks. Colloidal disks in suspension behave in fundamentally different ways than their spherical analogs studied in other parts of BCAT. Colloidal disks self-assemble like liquid crystals, forming, for example, aligned (nematic) phases and columnar phases depending on sample volume fraction and disk thickness-to-diameter ratio. It is anticipated that the finite disk size and shape in the samples leads to even more interesting entropic (i.e. excluded volume driven) phase behavior in microgravity. In particular, calculations and simulations have clearly predicted the formation of a stable cubatic phase at relatively high volume fraction (i.e. ~0.5) for disk thickness-to-diameter ratios between 0.15 and 0.30. In this case the system is predicted to evolve from the one phase to another as a function of increasing volume fraction for a fixed thickness-to-diameter ratio. An aligned nematic phase has not been observed by the theorists in this regime.

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Applications

Space Applications

Binary Colloid Alloy Test (BCAT) experiments lays the foundation for nanotechnology and nanomechanical systems in space.

Earth Applications

Though direct applications of that understanding do not yet drive the research, growth of ordered colloidal phases has attracted interest in a number of areas, e.g., ceramics, composites, optical filters and photonic bandgap materials. The use of asymmetric particles may produce directionally dependent crystal properties, and the use of particles whose size depends upon temperature may afford temperature tunable crystals.

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Operations

Operational Requirements

The BCAT-6 consists of a set of ten small samples of colloidal particles. The BCAT-6 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 about 7 hours of crew time; a third session to mix and photograph all 10 samples (about 4.6 hours of crew time) and then a fourth session at six months to photograph all ten samples which is slotted to take about four hours 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.

Operational Protocols

BCAT-6 typical operations consists of:

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 six months after homogenization, manually photograph Ssamples 1 through 10. Re-stow sample module and tear down after operations are complete.

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Results/More Information

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Related Websites

ISS Research Project-BCAT-Colloidal-Disks

NIH BioMed-ISS Meeting Video Presentation, 2009-BCAT-6-Colloidal_Disks

NIH BioMed-ISS Meeting, 2009-BCAT-6-Colloidal_Disks

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Imagery

BCAT-6 - Colloidal Disks Samples 9 and 10. Sample 9 shows a thickness to diameter ratio: 0.20 volume fraction: approx. 10% (volume by weight). Sample 10 shows a thickness to diameter ratio: 0.20 volume fraction: approx. 50% (volume by weight).
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