Spatiotemporal light modulation of as-wrinkled azopolymer film enabling reconfigurable hierarchical micropatterns for advanced photonics
摘要
Azobenzene polymers (azopolymers) have emerged as promising photosensitive building blocks for dynamically controllable surface patterning. Exploiting their multiple photoresponses, in combination with post-wrinkling light modulation, remains challenging for fabricating reconfigurable hierarchical micro/nanotextures. In this study, we propose a simple combined exposure strategy (i.e., pre-exposure followed by selective exposure) to modulate the as-wrinkled azopolymer surfaces, resulting in diverse, unprecedented hierarchical wrinkling microstructures. It is found that pre-exposure can lock the original wrinkle orientation and prevent wrinkle reorientation in unexposed regions during subsequent selective exposure. Consequently, a smart combination of pre-exposure duration and selective exposure size factor enables the creation of wrinkling wavelength-customized patterns with singly oriented, dually oriented, disordered, or ordered/disordered hybrid microstructures. Systematic experiments and theoretical analysis demonstrate that the reconfigurable wrinkling behavior is governed by the synergy and antagonism among photo-induced stress release, the photosoftening effect, and the boundary effect in azopolymer films. As demonstrated, the combined exposure strategy, applicable to other optically responsive as-wrinkled systems, such as poly(methyl methacrylate) and poly(lactic acid), facilitates reconfigurable hierarchical wrinkling micropatterns for advanced applications in information display/storage, anticounterfeiting, and optical gratings.