A NASA-funded study on fluids has yielded a discovery
that may significantly change the way electronics, paint,
cosmetics and pharmaceutical industries develop products.

Researchers discovered a new approach for suspending fine
particles in fluids. Such collections of particles, called
colloids or colloidal suspensions, may help researchers
better understand how to manipulate small particle assemblies
found in fluids such as water or organic solvents (e.g.,
ethanol).

According to a paper co-authored by a NASA researcher at the
University of Illinois at Urbana-Champaign, which will appear
today’s issue of the Proceedings of the National Academy of
Sciences, the authors have devised a process that stabilizes
particles in fluids to prevent them from otherwise organizing
themselves or coagulating into a disordered gel-like
structure. The authors have named this approach “nanoparticle
haloing.”

“Paint is an example of a fluid that contains suspended
colloidal particles. If such particles become unstable, they
clump together causing the paint to thicken substantially.
This limits the product’s shelf life. By using the
nanoparticle haloing approach, we can control the behavior
and structure of materials in fluids,” said Dr. Jennifer
Lewis, co-author, NASA researcher and professor at the
University of Illinois.

Lewis and her colleagues conducted the research under a grant
from NASA’s Office of Biological and Physical Research,
Washington, DC. The research program offers investigators the
opportunity to use a microgravity or low-gravity environment
to enhance understanding of fundamental physical and chemical
processes associated with materials science.

“NASA scientists are using microgravity to examine the
properties and structures of materials and the role
processing plays in creating the materials. By subtracting
gravity from the equation, we are better able to see what is
happening as a material is produced,” said Dr. Kathie Olsen,
Acting Associate Administrator for Biological and Physical
Research at NASA Headquarters.

By tailoring the interactions between particles, the
researchers were able to engineer the desired degree of
colloidal stability into the mixture. “That means we can
create designer colloidal fluids, gels and even crystals,”
Lewis said. “This designer capability will assist us in
developing improved materials such as photonics.” Photonics
are materials that control the flow of light.

For example, Lewis has teamed with co-author Paul Braun, a
professor of materials science and engineering at the
University of Illinois, to explore the use of these
nanoparticle-stabilized colloidal microsphere mixtures in
assembling robust periodic templates for photonic band gap
materials. The researchers recently were awarded funding by
the National Science Foundation to pursue such efforts.

Lewis and her students are also studying the structure and
flow behavior of colloidal fluids and gels assembled from
these microsphere-nanoparticle mixtures. By simply varying
composition, the researchers can produce systems whose
properties vary dramatically. Such studies provide the
foundation of ongoing efforts in the area of colloidal
processing of electrical ceramics.

In addition to Lewis and Braun, the research team included
University of Illinois doctoral students Valeria Tohver and
James Smay, from Lewis’ group, and graduate student Alan
Braem from Carnegie Mellon University, Pittsburgh.

More information on NASA’s Biological and Physical Research
Program is available at:
http://spaceresearch.nasa.gov

Additional information about this research is available at:
http://colloids.mse.uiuc.edu

NASA’s Marshall Space Flight Center, Huntsville, AL, manages
the Materials Science Program for the Office of Biological
and Physical Research. Marshall is also NASA’s lead center
for microgravity research — conducting unique scientific
studies in the near-weightlessness of space to improve life
on Earth.