Light-printable epoxy oligomer wrinkle-forming surface for rewritable information storage

Smart surfaces with controlled topography show broad and fantastic applications in optics, biology and information science. Herein, we report a simple visible-light-illumination approach to fabricate a smart wrinkle-forming surface with photo-controllable hierarchical surface patterns as well as rewritable high-resolution patterns of information by using an azobenzene-containing epoxy-based oligomer. The epoxy oligomer was synthesized via the ring-opening polymerization of bisphenol AF diglycidyl ether (BADFGE) with p-aminoazobenzene (AAB) and characterized using FTIR, H-1 NMR and F-19 NMR spectroscopies. When the epoxy oligomer film was deposited on an elastic substrate, the formation of surface wrinkles was triggered via a circulation of heating/cooling and photo-tailored due to photo-softening together with the release of stress induced by cycles of photoisomerization of azobenzene in the oligomer. The wrinkles in selectively light-exposed regions could be photo-erased within tens of seconds, yielding a different pattern of information. The high-resolution photo-printed images were shown to be rewritable for multiple cycles and legible for over 3 months in dark ambient conditions. The as-formed epoxy oligomer wrinkle-forming surface was found to be inexpensive and its fabrication was easily amenable to scale up, indicating its great potential as ink-free light printable media for rewritable information storage.