Tuning and Erasing Surface Wrinkles by Reversible Visible-Light-Induced Photoisomerization

• Published in: Angewandte Chemie International Edition 2016-03, Vol.55 (12), p.3931-3935
• Main Authors: Zong, Chuanyong, Zhao, Yan, Ji, Haipeng, Han, Xue, Xie, Jixun, Wang, Juanjuan, Cao, Yanping, Jiang, Shichun, Lu, Conghua
• Format: Article
• Language: English
• Subjects: azopolymers; Devices; Evolution; Evolutionary design method; Exposure; Failure; Functional anatomy; isomerization; Light effects; mechanical properties; Nonlinear dynamics; photochemistry; Stresses; Tuning; Wrinkling
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201510796

Periodic wrinkling across different scales has received considerable attention because it not only represents structure failure but also finds wide applications. How to prevent wrinkling or create desired wrinkling patterns is non‐trivial because the dynamic evolution of wrinkles is a highly nonlinear problem. Herein, we report a simple yet powerful method to dynamically tune and/or erase wrinkling patterns with visible light. The light‐induced photoisomerization of azobenzene units in azopolymer films leads to stress release and consequently to the erasure of the wrinkles. The wrinkles in unexposed regions are also affected and oriented perpendicular to the exposed boundary during the stress reorganization. Theoretical models were developed to understand the dynamics of the reversible photoisomerization‐induced wrinkle evolution. This method can be applied for designing functional materials/devices, for example, for the reversible optical writing/erasure of information as demonstrated here. Surface wrinkles on azopolymer films can be optically erased by visible‐light irradiation. The rapid reversible photoisomerization of the azobenzene units generates a significant local nanoscale force throughout the film, which leads to stress release and erasure of the wrinkles. Highly ordered wrinkling patterns with well‐defined microstructures were fabricated by selective light exposure.