Patterned Hierarchies of Functional Materials

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Life, consciousness, replication, magnetism, liquid crystallinity and biological morphogenesis are what we call "emergent" properties. These can be said to evolve from hierarchies of patterns. A hierarchy can be understood as a kind of branched tree that shows how its different parts are connected. The “tree” functions as a tree only by virtue of how all the parts interact. The tree, like consciousness or biological morphogenesis, is really not reducible to atoms and molecules. Emergence refers to the way that parts come together (assemble) to yield some sort of pattern that is connected to a functional property, like the ability to conduct light or magnetism. It is from the patterning of the parts that such properties emerge. In Nature, micro-organisms like diatoms (phytoplankton) take up silicic acid from water. Silicic acid is a tetrahedral 4-atom molecule that is used by the diatom to build a very ornate “glass house” - a protective shell called the frustule. The frustule has a complex periodic pattern, though the glass itself is disordered at the molecular scale. Diatoms are responsible for the oxygen in every 4th breath one takes, so it is useful to understand the role that the frustule might play in harvesting light for photosynthesis. We suspect that diatoms use the frustule as a complex optical device to collect sunlight and channel it to its chloroplasts to fix carbon dioxide and make oxygen. In our research, we use theoretical models and conduct experiments to show how diatoms are photonic (optical) on a very small scale they are nanophotonic. We show how pattern formation leads to nanophotonic behavior. Magnetism too is the result of patterning of electrons in an ordered way (ferromagnetism is an example). There are unusual fluids ferrofluids that consist of magnetic nanoparticles like magnetite, Fe3O4. When a flat pool of such a fluid is exposed to a magnetic field, a pattern suddenly forms. This breaks the rotational symmetry of the pool, and we call this a phase transition. Symmetry-breaking leads to patterns. We are interested not only in how these patterns form, but how to make permanent records of them. We have discovered a way to do so, and we describe it in this research proposal. Permanent patterns of magnetic material will allow us to create new kinds of magnetism for things like tiny actuators that can be mobilized in magnetic fields to imitate the cilia of micro-organisms or in the human lung. Such a study can impact health research. In the end, the study of patterned structures will tell us something new about how to create new functions of matter that emerge from patterns. It is for these reasons that we entitle our research program, Patterned Hierarchies of Functional Materials.