Researchers at Tianjin University have demonstrated both empirically and theoretically the effectiveness of a simple yet powerful method of modifying and/or erasing the surface wrinkles on a poly film bonded to a poly substrate with visible light.They showed that light irradiation leads to the release of the internal stress and as the continuous variation of the stress field decreases the wrinkle amplitude changes and finally erases the wrinkling patterns in the exposed region. Moreover, the wrinkles around the unexposed region are modified during selective exposure. They demonstrated that this optically controlled wrinkling system can be used for the reversible optical writing and erasure of (classified) information. Furthermore, the current strategy may be applied for eliminating undesired surface wrinkles and fabricating functional surfaces with tunable friction, adhesion, wetting, and optical properties.
Although commonplace in nature, this research is important as it has proved difficult to precisely and cost-effectively control or obtain consistent wrinkle patterns. Surface wrinkling has a variety of applications ranging from achieving gloss and matt and non-slip surface finishes to film mechanical characterization, structured templates, to flexible devices. Periodic patterns show special hydrodynamic, aerodynamic and wetting/self-cleaning properties, which have many potential applications in wettability modulation, optical devices with many applications in modern microfluidics, microelectronics or combinatorial chemistry for sensing, analysis or synthesis that require array type structures as building blocks.
Lu Conghua’s research group from Polymer Research Institute of School of Materials Science and Engineering in Tianjin University, together with Cao Yanping’s research group from Department of Engineering Mechanics in Tsinghua University, published the research on surface wrinkling control, “Tuning and Erasing Surface Wrinkles by Reversible Visible-Light-Induced Photoisomerization” in the form of VIP article in the international authoritative journal Angewandte Chemie (Angew. Chem. Int. Ed. 2016，128，3999-4003).
Zong Chuanyong, a PHD student from the School of Materials Science and Engineering in Tianjin University, and Zhao Yan, a PHD student supervised by Professor Cao Yanping from Department of Engineering Mechanics in Tsinghua University, were the first co-authors and collaborated to complete the ground-breaking research. This achievement is supported by the Natural Science Foundation of China.
