Advanced Colloids Experiment-Nanoparticle Haloing (ACE-T-12) involves design and assembly of complex three-dimensional (3D) structures from colloids, or particles of different sizes suspended in a fluid. It employs a recently discovered technique, Nanoparticle Haloing (NPH), which uses highly charged nanoparticles to stabilize much larger, non-charged particles. Allowing these structures to form in microgravity provides insight into the relationship between shape, surface charge, and concentration of particles and particle interactions.
The experiment has concluded, and science is being evaluated.
In the Advanced Colloids Experiment-Nanoparticle Haloing (ACE-T-12) investigation, fundamental insights can be gained into the interaction of smaller nanoparticles with larger colloids, i.e. the “nanoparticle haloing” (NPH) phenomenon, as a function of particle concentration. Crystallization behavior of the larger colloids can also be observed, whose structure is a function of the size and concentration of the nanoparticles. It is hoped that unobstructed NPH interactions, which would otherwise be significantly hindered by gravity on Earth due to sedimentation issues (high density contrast between particles and fluid), can be observed in the microgravity environment aboard the International Space Station.
Microgravity allows monitoring of particle behavior for longer time periods, and this experiment enables the first observation of 3D aggregations formed by NPH. The resulting structure and its stability address fundamental issues in the science of condensed matter. The use of the Light Microscope Module (LMM) enables insight into finer control of the assembly of such colloidal structures, continuing the move toward increased commercial use of the International Space Station.
Self-assembled colloidal structures are vital to the design of advanced materials. This investigation contributes to fundamental understanding of nanoparticle haloing and the colloidal structures it creates. That lays the foundation for applying this technique to creating next-generation colloidal materials, including optically-based energy platforms and sensors, for use on Earth.