Multi-color inkless UV printing using angle-independent structural color paper

Abstract

Inkless photonic paper has shown great potential as an alternative to traditional paper due to its unique structural color, which is dye-free and non-photobleaching. However, it is still highly challenging to produce large-area photonic crystal paper, and its angle dependence, complicated printing procedure, and difficulty of high-resolution printing have greatly limited its applications. To address these challenges, we developed a new UV printing strategy using amorphous structured inverse opal PEGDA photonic paper. The photonic paper is prepared using an amorphous assembly of colloidal SiO₂ particles as templates, which are fabricated by spray coating dispersions of SiO₂ particles with the addition of carbon black. The photonic paper possesses structural color with low angle independency when the observation angle varies from 0° to 40°, and the unvivid structural color can be tuned in the whole visible region by exposure to UV radiation for different amounts of time, providing a fast, convenient and high-resolution printing technique. Through a chromatic-printing-like method using a series of different masks, multi-color printing is also realized. The printed images can be further protected from UV irradiation using a layer of PET film, which provides a method to store the printings for a longer time in a harsh environment.