The Physics of Colloids in Space (PCS) experiment is a Microgravity Fluids Physics investigation that is presently located in an Expedite the Process of Experiments to Space Station (EXPRESS) Rack on the International Space Station. PCS was launched to the International Space Station on April 19, 2001, activated on May 31, 2001, and will continue to operate about 90 hr per week through May 2002.
Physics of Colloids in Space (PCS) test section features.
Long description
PCS is concurrently gathering data on the basic physical properties of three different types of colloids to study how colloidal structures grow, the rates at which they grow, and the structures that they form. A colloidal suspension consists of fine particles (micrometer to submicrometer) suspended in a fluid, for example, paints, milk, salad dressings, and aerosols. The long-term goal of this investigation is to better understand how colloidal constituent properties affect the properties of a bulk colloidal suspension and to begin to probe the unique light-scattering properties of nanoengineered binary colloidal alloys. The potential payoffs of PCS are improvements in the properties of paints, coatings, ceramics, and food- and drug-delivery products; improved manufacturing of products requiring either colloidal suspensions for processing or as precursors; and important first steps in the research and development of an entirely new class of materials that can passively affect the properties of light passing through them. These materials may find uses as optical switches and lasers for advanced communications and displays. This experiment is the first part of a two-stage investigation conceived by Professor David Weitz of Harvard University along with Professor Peter Pusey of the University of Edinburgh.
Colloid polymer critical point sample--13 hr, 24 min
after being mixed. Sample shows a phase separation
never seen on Earth.
Long description
AB6 binary colloidal alloy sample--20 days, 11 hr
after being mixed. Bands of color can be seen that
were created by the diffraction of white light by
the crystallized sample.
Long description
PCS contains eight approximately 3-milliliter colloid samples, each contained by a glass cell stationed within a remotely controllable carousel inside the PCS test section. Experiment operations consist of mixing (or homogenizing) the colloid samples to eliminate any sedimentation and to produce a uniform distribution of particles in the solution. Once mixed, particles start to self-assemble, and the diagnostic measurements are initiated. Measurements are regularly made on each sample over 1 to 2 months as its substructures (either crystallines or gels) grow and evolve. Measurements include still color digital images, high-angle static laser light scattering (or Bragg scattering), low-angle static and low-angle dynamic light scattering, fiber static and fiber dynamic light scattering, and rheology. The diagnostic data provide growth information, the shape of the structures formed, and other physical properties of the structures.
PCS is being remotely operated from the NASA Glenn Research Center's Telescience Support Center in Cleveland, Ohio, and at an established remote site at Harvard University in Cambridge, Massachusetts. The two locations permit daily remote operation of the experiment. In real time via commands uplinked from Earth to the International Space Station, the PCS commanders control such activities as which sample to interrogate, when to homogenize the sample, which diagnostic technique to employ to perform the interrogation, as well as the sequencing of sample diagnostic runs.
PCS completed its checkout operations on June 22, 2001. During the subsequent 13 weeks, it did an initial survey of crystal nucleation and growth on six of the eight samples and then reinitiated more detailed investigations on the two binary colloidal alloy samples. The crystalline samples (AB6, AB13, colloid polymer crystal, and colloidal glass) are all behaving as hoped for, with the growth of the crystallites having been interrogated by a host of different state-of-the-art light-scattering techniques. The colloid polymer critical point sample, as hoped, exhibits, upon homogenization, a phase separation, or demixing process, that would never be seen in 1g. The colloid polymer gel sample, the last of the six samples to be homogenized, was verified to gel in microgravity, and aging of the gel was observed. Each of these six samples is to be rehomogenized to enable more detailed investigations to occur over the upcoming months on orbit.
Diffraction patterns from the AB13 binary colloidal alloy sample
(high-angle scattering). Intensity shown in arbitrary units; q is directly proportional to
the scattering angle. Growth of Bragg peaks over time indicates the presence
of crystals. Top: 0.48 hr after melting. Bottom: 255 hr after melting.
Long description
Overall, the initial survey was successful in determining the crystallization time and other characteristics of the samples, revealing exciting areas of interest for each and confirming the diagnostic techniques to be used for the much more detailed measurements to be conducted on each sample through May 2002. Two samples yet to be interrogated, composed of colloids that gel in an irreversible manner when a salt is added, will be initiated during future PCS experiment runs. To date, experiments performed by PCS have proceeded very well with the instrumentation exceeding Professor Weitz' expectations. The PCS experiment was developed and launched and is being operated by Zin Technologies under NASA contract NAS3-99154.
Find out more about this research:
Glenn's PCS research (includes data on a sample-by-sample basis--being updated)
Principal investigator group at Harvard (scientific focus areas
of interest) (external site)
Glenn's microgravity research
Glenn's fluid physics research
Glenn contacts: Michael P. Doherty, 216-433-6641,
Michael.P.Doherty@grc.nasa.gov; and Dr. Subramanian Sankaran, Subramanian.Sankaran@grc.nasa.gov
Author: Michael P. Doherty
Headquarters program office: OBPR
Programs/Projects: Microgravity Science
Last updated: June 2002
Responsible NASA Official:
Gynelle.C.Steele@nasa.gov
216-433-8258
Point of contact for NASA Glenn's Research & Technology reports:
Cynthia.L.Dreibelbis@nasa.gov
216-433-2912
SGT, Inc.
Web page curator:
Nancy.L.Obryan@nasa.gov
216-433-5793
Wyle Information Systems, LLC
