Advanced Colloids Experiment-Microscopy-2 (ACE-M-2) - 07.14.16
Sometimes it's hard to tell a gas from a liquid. Advanced Colloids Experiment-Microscopy-2 (ACE-M-2) observes the microscopic behavior of liquids and gases separating from each other. The investigation examines the behavior of model (colloid rich) liquids and model (colloid poor) gases near the critical point, or the point at which there is no distinct boundary between the two phases. ACE-M-2 uses a new microscope to record micro-scale events on short time scales, while previous experiments observed large-scale behavior over many weeks. Liquids and gases of the same material usually have different densities, so they would behave differently under the influence of gravity, making the microgravity environment of the International Space Station ideal for these experiments.
Science Results for Everyone
Information Pending Experiment Details
David A. Weitz, Ph.D., Harvard University, Cambridge, MA, United States
Peter J. Lu, Ph.D., Harvard University, Cambridge, MA, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
March 2014 - September 2014
- Using a model system, ACE-M-2 is a fundamental investigation of the behavior of liquids and gases near the critical point, where sedimentation doesn't does not play a role. Because liquids (colloid rich sample portions) are almost always denser than gases (colloid poor sample portions) of the same material, earth-bound experiments are almost always affected by sedimentation. By going to ISS, these effects are eliminated, allowing a true picture of phase separation behavior, without the interfering effects of gravity.
- Observations of a number of samples corresponding to different densities and effective temperatures, around the critical point, is the goal. This allows the testing of a number of important theories in physics and chemistry surrounding the areas of critical phenomena, phase transitions, and statistical mechanics / thermodynamics.
- Fundamental studies are conducted, so the major impact will be a better understanding of these important processes. This understanding will have impact in a number of practical applications, for instance the development of household products by Procter & Gamble, worth billions of dollars to the US economy.
On Earth, gravity plays a big role in how liquids and gases interact: The heavier liquid phase settles beneath a lighter gas phase, and these differences in density enable easy separation. But the flow and behavior of complex fluids and phase separation where there is little or no gravity is not well understood. A greater understanding of liquid-gas interaction in microgravity could benefit a wide range of fluid storage, transport and processing systems for future spacecraft.
Particle separation and behavior in liquids, gels, and creams is important for developing consumer and household products, which are worth billions of dollars annually to the U.S. economy. Many consumer products are complex fluids, combining microscopic particles in gel or liquid, which are similar to the model colloidal system used in the ACE investigations which give insight into product formulations that could be used to maximize stability and shelf life.
Operational Requirements and Protocols
- Data bottlenecks on IPSU and IOP
- XY position repeatability (need to return to the same particle set or don’t move during experiment => one well position. This takes too long, so find a solution. Images can be registered in post-processing via port or stir bar location, or pattern of particles stuck to bottom of cover slip.
- Oil availability – available immersion oil limits runs to one strip at a time; air objective has no such constraints.
1. Inspect Samples
2. Ground to choose first of three sample strips and first Sample to test; feedback to crew.
3. Mix all samples in strip using drill BCAT magnet for 30 seconds.
4. Apply oil in (Auxiliary Fluids Container) AFC and install assembly. It may require more than one drop of oil be applied when initiating a run of five sample wells on a strip.
5. Define XYZ offsets (assembly alignment per ACE-1 method).
6. Adjust camera parameters using 2.5x objective and B/S cube.
7. Survey well at 2.5x; determine primary (and secondary?) test locations (select locations away from stir bar or bubble).
8. Adjust and record best camera parameters using 100x oil objective and Texas Red filter.
9. Survey and record best Z-depth at each primary test location.
10. Experiment on one well using 100x oil objective; each image set at highest frame-rate (6 to 8 fps), no binning (8 bpp highest supported), full frame images. Store 100 images using Texas Red filter.
11. Move to next good sample in strip of 5 samples and Repeat until all good samples in strip have been imaged as outlined above.
12. Repeat measurements for all good samples in strip using a time interval of 0, 2, 4, 8, and 16 hours. This means that an entire strip of 5 samples can be run in under 1 ½ days.
13. The goal is to successfully image 15 unique sample wells. 15 of the 30 wells are replicates and are flight spares.
Decadal Survey Recommendations
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Space Flight System
NASA Image: ISS039E016369 - Close-up view of an ACE-M-2 sample.
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NASA Image: ISS039E016376 - Close-up view of an ACE-M-2 sample.
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