Directional photofluidization lithography: Micro/nanostructural evolution by photofluidic motions of azobenzene materials

This review demonstrates directional photofluidization lithography (DPL), which makes it possible to fabricate a generic and sophisticated micro/nanoarchitecture that would be difficult or impossible to attain with other methods. In particular, DPL differs from many of the existing micro/nanofabrication methods in that the post-treatment (i.e., photofluidization), after the preliminary fabrication process of the original micro/nanostructures, plays a pivotal role in the various micro/nanostructural evolutions including the deterministic reshaping of architectures, the reduction of structural roughness, and the dramatic enhancement of pattern resolution. Also, DPL techniques are directly compatible with a parallel and scalable micro/nanofabrication. Thus, DPL with such extraordinary advantages in micro/nanofabrication could provide compelling opportunities for basic micro/nanoscale science as well as for general technology applications. Directional photofluidization enables structural evolution toward high resolution with various shapes, unprecedented complexity, and lower edge-roughness by virtue of the reversible and directional motions of azo-materials (a path-changing approach). This reversible and fluidic evolution of micro/nanostructures provides both micro/nanostructural designs beyond those that can be achieved using established lithographic approaches and excellent motivation for novel photonic properties.