Investigating the Structure of Paramagnetic Aggregates from Colloidal Emulsions - 3 (InSPACE-3) obtains data on fluids containing ellipsoid-shaped particles that change the physical properties of the fluids in response to magnetic fields.Principal Investigator(s)
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)ISS Expedition Duration:
March 2011 - March 2013
27/28,29/30,31/32,33/34Previous ISS Missions
InSPACE, the precursor to InSPACE-2 was performed on ISS Expeditions 6, 7, 12 and 13.
The use of external fields to control the microstructure of colloidal suspensions has long been recognized as a powerful means for tailoring the mechanical, optical and electronic properties of materials. Magnetorheological (MR) suspensions, in particular, provide a striking example. These normally stable fluids undergo a dynamic transition to a solid within milliseconds after the application of an external magnetic field. They are also important models for developing methods of bottom-up fabrication of micro- and nano-structured materials and devices using field-directed self-assembly.
Investigating the Structure of Paramagnetic Aggregates from Colloidal Emulsions-2 (InSPACE-2) experiments focused on the structure of magnetically-polarizable particle suspensions over long times in steady (DC) and pulsed magnetic fields. In pulsed fields especially, the long-time kinetics of the suspension micro-structural coarsening provided new and important results. The InSPACE-2 experiments were the first to yield information on the full, three-dimensional aggregation process over timescales much longer than those that are accessible on the ground, which are limited by catastrophic sedimentation. Furthermore, the experiments identified a novel and intriguing dynamic instability in which the suspension microstructures were observed to buckle at specific field frequencies and field strengths. For InSPACE-3, we will investigate the effect of particle shape on the micro-structural evolution of MR suspensions. Recent ground-based experiments demonstrate a startling effect that particle shape has on the interactions of dipolar chains and the resulting suspension microstructure. Specifically, we will investigate suspensions of paramagnetic ellipsoid-shaped particles. In combination with the results of InSPACE-2, we hypothesize that particle shape will dramatically alter the aggregation kinetics, microstructures and microscopic mechanics. This will potentially lead to the ability to engineer enhanced properties of these suspensions, including suppression of the lateral aggregation in magnetorheological fluid-based electromechanical devices or the ability to create new colloidal materials through field-directed self-assembly.
These fluids are used in electromechanical interfaces and devices in which the fluid is operationally exposed to similar fields which can affect their operation. Current commercial magnetorheological fluid products include tunable dampers and brakes, while future applications in robotics, clutches, and a host of vibration-control systems are envisioned.Earth Applications
After the magnetic field is applied to a MR fluid, the microstructures form a rigid lattice that causes the suspension to stiffen. The study of MR fluids on Earth is difficult as these paramagnetic particles sediment, or sink, while the magnetic field is applied, effecting the formation of aggregate structures. The low-gravity environment that is provided on the ISS will eliminate this sedimentation effect. The rapid transformation of these fluids have many possible technological applications on Earth, especially for actuator-type devices. This technology has promise to improve the ability to design structures, such as bridges and buildings, to better withstand earthquake forces.
InSPACE-3 will be conducted inside the MSG work volume. The fluid sample in the vial assembly must be uniformly mixed prior to test operations. Thirty-six tests will be performed, two or three per day. The Vial Assemblies may be reused indefinitely after restoring an even distribution to the particles within the fluid. Video downlink will be monitored on the ground during testing and provided to the PI as desired. Sample return of the Vial Assemblies is not required. Video imagery will be stored on 72 Mini-DVCAM tapes and 36 Hi-8 tapes for later return to the ground for more complete analysis.Operational Protocols
The crew will install the hardware into the MSG and as part of that uniformly distribute the particles in the fluid of the first Vial Assembly prior to installation in the hardware. Two DVCAM and one Hi-8 tape will be loaded into the video recorders in the video drawer. The crew member will next focus each optical train onto the particles in the center of the vial. A run is started by setting the current per the test matrix and then setting the pulse frequency of the current. Both are simple adjustments of dial pots by the crew while observing digital displays of the values of each. Note that the current level controls the strength of the magnetic field applied to the MR fluid. A Field of View sweep and a focus sweep are performed right away with each optical train and then again about 20 minutes later. The experiment will run autonomously with ground monitoring for the next two to three hours. Another FOV sweep and focus sweep for each optical train is performed prior to removing the magnetic field from the vial by setting the current to zero. Another run may be started with the same vial assembly after remixing the particles in the fluid, or a different vial assembly may be used. Upon completion of all testing, the hardware is removed from the MSG.