No abstract

A greenhouse covering film is an essential part of any greenhouse. Its function is to filter solar radiation in the ultraviolet (UV) and the near-infrared (NIR) bands while allowing a great amount of photosynthetically active radiation (PAR) to transmit. This paper proposes a design of the greenhouse covering film based on a frequency selective surface (FSS). Aluminum is made into fibers in the nanoscale. They are laid out in an array, in-plane at equidistance from one another. This arrangement induces the wavelength selectivity of light via adjustment to the fiber sizes and spacings. The performance is evaluated by a finite element analysis (FEA) method. The results show less than 26% transmittance of UV and NIR while allowing more than 94% transmittance in the PAR regime.

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.