A Self-Color-Changing Film with Periodic Nanostructure for Anti-Counterfeit Application

A self-color-changing film aimed at enhanced security and anti-counterfeit packaging is presented. Its function is to change color automatically when flipped under visible light. It is low-cost, takes a few seconds to check by the naked eye, and does not need any special tools to evaluate.
The design of the color-changing, anti-counterfeiting film is based on a frequency-selective surface
(FSS). The film is designed with aluminum nanocubes. They are laid out as an array in a plane with
equal distance from one another. This arrangement allows us to select certain wavelengths of light to
pass through by the size of the cubes and the separation distance between them. The performance
is evaluated by a finite element analysis (FEA) method. The results show that the intersection of
transmittance and the reflectance curves cause the film to change its color automatically when flipped.
We also propose a method to predict the color of the film based on the transmittance values. The
accuracy of this method is verified by actual colors from experiments with an error of no more than
12.8%, analyzed by the CIE chromaticity diagram.