The number of advanced materials manufactured by assembling colloidal particles is growing. The assembly can be controlled by applying external fields that affect the motion of the particles and their arrangement during assembly. This project will use facilities on board the International Space Station (ISS) to study the assembly of ellipsoidal magnetic particles in the presence of a toggled magnetic field. The microstructure of the suspension as the particles assemble will be characterized by light microscopy. Mechanical properties of the particle assemblies, especially buckling instabilities, will also be characterized. The microgravity environment of the ISS is important for these experiments, because the particles would sediment due to gravity with a sedimentation rate that increases as the they form large and complicated structures. The project will provide opportunities for students to participate in research, including K-12 students who participate in the University of Delaware's summer Young Engineers Camp and Exploring Engineering Camp. Undergraduates will be recruited to the project through the university's Undergraduate Research Program.
The ISS experiments in this project will be conducted using InSPACE hardware and microgravity sciences glovebox. Experiments will be performed with magnetic prolate ellipsoids with aspect ratios ranging from 2:1 to 4:1. Experiments involving spheres will also be conducted for comparison purposes. The particle orientation will be determined from birefringence measurements using crossed polarizers. The effects of particle shape, anisotropy, and magnetic field toggling frequency on the phase separation of particles will be examined. Relatively short duration, ground-based experiments will be conducted using the same magnetic particles to provide additional details about structure formation from particle-level to mesoscale structure. The colloidal ellipsoids examined in this project could serve as building blocks for phononic bandgap materials that control the propagation of sound and heat, ultra-low thermal conductivity coatings, and photonic crystals with rich structural color. The research team will use the project to engage the public by producing segments for a variety of media outlets, especially those that concentrate on space-based research.
