The collected data was processed, enabling a quantitative assessment of the structural data,
including aggregate sizes and shapes. These are key parameters for defining the aggregate
kinetics and are used to test theoretical models of the microstructures. Furthermore,
understanding the complex properties of the fluids and the interaction of the microparticles will
enable the development of more sophisticated methods for controlling and use of these fluids.
Results suggest that InSPACE runs did not achieve steady-state structures. However, intriguing
data suggesting the onset of instability at low frequency was collected. Both of these
phenomena will be further addressed in InSPACE-2 (Vasquez 2008).
INSPACE-2 (FURST)
For the InSPACE-2 experiment, 2 distinct particle growth processes were observed: one where
particle-rich and particle-poor regions form and become “trapped,” and the other where the
system-spanning structure suddenly collapses and particle columns form. These 2 processes
are separated by a distinct boundary that depends on the magnetic field strength and magnetic
frequency, and results demonstrate how energy barriers preventing colloidal phase transition
can be overcome by changing the magnetic driving frequency and forces. As with other
experimental studies of colloids in microgravity, the results of the InSPACE-2 experiments show
that in these gel systems, gravity plays a dominant role and would slowly compress and deform
the gel structures when similar experiments are performed on Earth, whereas in space these
structures can be maintained as long as the magnetic forces are applied. Through better
understanding of the stable and unstable phase behavior in the absence of gravitational
stresses, these results demonstrate how colloidal suspensions may be harnessed in the creation
of unique materials and electro-mechanical devices by manipulating the magnetic forces
holding them intact (Swan 2012).
PUBLICATION(S)
Swan JW, Vasquez PA, Furst EM. Buckling instability of self-assembled colloidal columns.
Physical Review Letters. September 23, 2014;113:138301. doi:
10.1103/PhysRevLett.113.138301.
Structure evolution in an MR fluid over time while an alternating magnetic field is applied. The far left image
shows the fluid after 1 second of exposure to a high-frequency-pulsed magnetic field. The suspended particles
form a strong network. The images to the right show the fluid after 3 minutes, 15 minutes, and 1 hour of
exposure. The particles have formed aggregates that offer little structural support and are in the lowest energy
state. NASA Glenn Research Center, Cleveland, Ohio image.