Top-down nanopatterning is the most effective approach for creating nanostructures of complex geometries and therefore, usually the first step in nanomanufacturing. Unfortunately, conventional approaches to nanopatterning are extremely slow compared to pattern replication. This award supports research that combines a massively parallel architecture and a new method that allows light to define nanostructures far smaller than is otherwise possible. The result is to achieve fast nanopatterning of structures as small as a large molecule. When fast pattern generation is combined with fast pattern replication (such as roll-to-roll nanoimprint lithography), a new paradigm for nanomanufacturing arises. This paradigm has the potential to enable entirely new material and device functionalities as it provides exquisite control of structure at the nanoscale in conjunction with such control over macroscopic areas. When brought to fruition, this technology will enable new classes of devices and applications, e.g., light-trapping for thin-film solar-cells, large-area self-cleaning surfaces, anti-microbial surfaces, and large-area metamaterials (e.g., cloaking materials). This award will provide essential training in research that draws upon expertise in multiple disciplines including optics, chemistry, electrical engineering and materials science. The fundamental knowledge generated during this research will be widely disseminated via the commercialization of the new nanopatterning technology.
The far-field diffraction limit is a fundamental physical barrier that limits the size of a focused optical beam to approximately half its wavelength. When applied to nanopatterning with visible light, this limit prevents the generation of structures below ~200nm. This project will overcome this limit by using photochromic molecules that can be toggled between two isomeric forms. By exposing a monolayer of such molecules to a spatially varying intensity distribution, a chemical pattern of the two isomers is first formed. Using a stepping stage with nanometric precision, the substrate is then moved relative to the optics. A second exposure to the same illumination toggles the photochromic molecules. By appropriate displacement of the stage, it is possible to leave arbitrarily small regions of molecules (down to the single-molecule level) in one isomeric form compared to the surrounding region. A subsequent locking step may then be used to selectively modify this isomeric form such that it is no longer photochromic. Since everything else on the surface is photochromic, the entire sequence of steps can be repeated to create geometries of arbitrary complexity in a "dot-matrix" fashion. This award will support fundamental research into the design, synthesis and characterization of appropriate photochromic molecules, a new optical system, and related processes.
