Buckling-Induced Angular-Switchable Diffraction Images on Polyurethane Film for Optical Encryption and Anti-Counterfeiting.

Abstract

Diffractive security images, constructed with micro-nano structures, are widely used in anti-counterfeiting due to their inherent high spatial frequency resolution and dynamic color variation. However, traditional diffraction anti-counterfeiting labels (DALs), typically based on acrylic ester materials, are susceptible to counterfeiting due to their simple encryption structures and the limited information capacity of single-channel encryption. Furthermore, in harsh environments such as high temperature or high humidity, they are prone to deformation, which can lead to loss of verification functionality. To address these limitations, we propose constructing eight high-resolution, angular-switchable, independent diffraction images on photosensitive polyurethane (Pho-PU) films through buckling structures that reveal different encrypted images as the viewing angle changes, through sample rotation, or varied illumination. We discuss the designability and controllability of periodic buckling structures and demonstrate how common information and secret keys can be integrated through this angle-multiplexing strategy. This systematic approach to multi-image encryption based on buckling structures provides an effective alternative for fabricating high-security DALs.