Photopatterning via Photofluidization of Azobenzene Polymers

In current photo-based patterning techniques, an image is projected onto a photosensitive material to generate a pattern in the area where the light is focused. Thus, the size, shape, and periodicity of the pattern are determined by the features on the photomask or projected images, and the materials themselves generally do not play an active role in changing the features. In contrast, azobenzene polymers offer a unique type of photopatterning platform, where photoisomerization of the azobenzene groups can induce substantial material movements at the molecular, micro-, and macroscales. Stable surface relief patterns can be generated by exposure to interference light beams. Thus, periodic nanoand microstructures can be fabricated with both twoand three-dimensional spatial control over a large area in a remarkably simple way. Polarized light can be used to guide the flow of solid azobenzene polymers along the direction of light polarization via an unusual solid-to-liquid transition, allowing for the fabrication of complex structures using light. This review summarizes the recent progress in advanced manufacturing using azobenzene polymers. This includes a brief introduction of the intriguing optical behaviors of azobenzene polymers, followed by discussions of the recent developments and successful applications of azobenzene polymers, especially in microand nanofabrication.