- Welcome to building
colloidal crystals
under microgravity.
I will give this presentation
on behalf of a team
of researchers
from New Jersey
Institute of Technology,
New York University,
Universities
Space Research Association,
and Streamline Automation.
We present the results
of our recent experiment
conducted on colloids
of spherical
and ellipsoidal particles
on the International
Space Station.
This work was supported
by the NASA advanced
colloid experiments program
and funded by several,
NSF, Casis, and NASA.
Of course the first question
is why do we need to study
colloids in microgravity?
The reason is that on Earth
gravitational sedimentation
confirms most colloidal systems
to two dimensions
with numerous artifacts
due to the presence
of warps and bubbles.
The unique long range duration
microgravity environment
found on the space station
adds another dimension
to the program,
making available 3D motion,
3D processing,
3D fundamental science,
and 3D materials.
Hard sphere is a basic model
of particles in
a statistical mechanical theory
of fluid and solid
[ indistinct ]
the extremely strong repulsion
that atoms
and spherical molecules
experience
at very close distance.
The hard sphere model
is a cornerstone
of our understanding
of liquid crystalization.
However, due to
gravitational settling
of particles,
terrestrial experiments
failed to confirm
the crystalline phases
predicted by
computer simulation.
The hard ellipsoid model
provides a generic model for
the quasi-universal structure
and dynamics of liquid crystals.
Compared to molecules
in liquid crystals,
which are too small to be seen
with an optical microscope,
the colloidal particles
are huge in size
and can be used
to test predictions
of computer simulations.
And the conclusion of our talk
is that up until now
the theory of the simplest,
most common, most fundamental
crystalization transition
from liquid
to face-centered cubic,
FCC, crystal
had not been confirmed.
Now it is confirmed.
We demonstrate that simulations
of equilibrium phase transitions
work only when
gravitational effects
are unimportant.
Our results validate
that computer simlulations of
equilibrium material structure
can be used in microgravity.
In more details,
process to employ microgravity
to address grand challenges
in soft matter science
and application are summarized
in the recent NASA publication
listed on this slide.