Daoming Sun

Optical encryption using nanostructured materials provides a powerful route for secure data encoding. In this work, an electrically reconfigurable colloidal photonic platform based on covalent organic framework (COF) particles is described, enabling dynamic and bistable data encryption. Spatially controlled electrophoretic assembly of monodisperse COF particles within patterned cells produces Bragg reflections that are visible only under bright-field (BF) microscopy as strong broadband scattering from nanoscale particle surface roughness conceals the encoded states from the naked eye. By tuning the synthesis time, the particle surface roughness and, thus, the degree of concealment can be precisely controlled. Unlike conventional optical systems, where scattering degrades visibility, we report it as an intrinsic security feature, transforming a loss mechanism into a tool for optical masking. The demonstrated platform combines electrical addressability, conditional optical visibility, and algorithmic decoding to deliver a compact, multifactor encryption system. These results demonstrate colloidal COF dispersions as a versatile class of photonic materials for secure displays, anticounterfeiting, and adaptive optical communication technologies.

Optical encryption based on nanostructured materials offers an innovative approach to secure data encoding. Here, we report an electrically addressable, colloidal photonic platform using covalent organic framework (COF) particles that enables dynamic, bistable image encryption. Through the electrophoretic self-assembly of size-controlled COF particles within patterned cells, we achieve spatially resolved Bragg reflections visible only under bright-field (BF) microscopy. The encrypted optical states remain hidden to the naked eye due to strong broadband scattering caused by nanoscale surface roughness—a feature tunable via synthesis time. Notably, the system exhibits bistability, maintaining the encoded state even after the removal of the electric field (EF) and enabling full reversibility by field polarity switching. The combination of electrical control, conditional visibility, and algorithmic decoding results in a multi-factor encryption strategy within a single material system. This work positions colloidal COF dispersions as a new class of multifunctional photonic materials for secure displays, anti-counterfeiting, and adaptive optical technologies.