Investigating the Structure of Paramagnetic Aggregates from Colloidal Emulsions

InSPACE is a series of microgravityThe condition of perceived weightlessness created when an object is in free fall, for example when an object is in orbital motion. Microgravity alters many observable phenomena within the physical and life sciences, allowing scientists to study things in ways not possible on Earth. The International Space Station provides access to a persistent microgravity environment. fluid physics experiments to obtain fundamental data of the complex properties of an exciting class of smart materials termed magnetorheological (MR) fluids. The objective of InSPACE was to determine the true three-dimensional equilibrium structure of an MR emulsion in a pulsed magnetic field. InSPACE conducted a microscopic video study of the MR fluid in a pulsed magnetic field to determine the effect of varying magnetic field, pulse frequency, and particle size on the equilibrium microstructures.

The InSPACE hardware consists of the vial assembly, coil assembly, optics assembly, light box assembly, and avionics assembly. The vial assembly consists of a commercial off-the-shelf (COTS) micro-slide (borosilicate capillary vial) with a 0.7 mm x 0.7 mm cross section, a 0.15 mm wall thickness, and a length of 50 mm. The capillary tube contains approximately 24.5 μL of fluid. For the original experiments, the fluid consisted of an aqueous solution of 0.52% volume fraction particles, 8 mM SDBS (sodium dodecyl benzenesulfonate, a surfactant), and deionized water. The particles were ellipsoid (2:4) polystyrene beads. A wide variety of alternate size capillary vials can be accommodated in the vial assembly, and modification to the vial assembly is possible. Alternative fluids and colloidal suspensions have already been flown in other investigations and can likely be used in InSPACE. The vial assembly is manually inserted into the coil assembly and is easily exchangeable. Science data is collected using two Hitachi HV-C20-S4 CCD cameras and an LED light source located in the light box assembly. The data is recorded on DVCAM and Hi-8 tapes. The avionics assembly is capable of supplying a steady or pulsed magnetic field ranging in intensity from 0 A/m to 2,700 A/m with a frequency of 0.66 Hz to 25 Hz.