# Multimodal, Multiband, and Multiple Anticounterfeiting Devices with Angle-Dependent Structural Color Highly Sensitive to Temperature

## TL;DR

This paper introduces a new anticounterfeiting device that uses temperature-sensitive materials to display changing colors and multiple optical signals for enhanced security.

## Contribution

A thermoresponsive magnetic photonic crystal hydrogel film is developed for multimodal, multiband anticounterfeiting devices.

## Key findings

- The device shows optical responses in reflection, transmission, and emission modes across visible to near-infrared wavelengths.
- The structural color changes across the full visible spectrum with temperature, achieving a sensitivity of 11.5 nm/0.1 °C.
- The device offers stable repeatability and wide-angle dependence for advanced anticounterfeiting applications.

## Abstract

Conventional anticounterfeiting devices rely on high-resolution equipment and only provide limited encrypted information, which greatly constrain the efficacy of ever-increasing high-end counterfeiting functionalities. In this study, we propose a simple solution method to fabricate an arbitration anticounterfeiting device with multimodal, multiband, and multiple optical properties, where a thermoresponsive magnetic photonic crystal hydrogel film is in situ chemically anchored onto a modified glass and sealed with a gasket and single-sided indium-tin oxide glass. The resulting device exhibits distinguishable optical responses in terms of reflection, transmission, and emission modes, covering a wide range of wavelengths from visible to near-infrared and long-wave infrared. Notably, the wide-angle dependent structural color of the device may change in the full visible spectrum (red to blue) with temperature, and the sensitivity is up to 11.5 nm/0.1 °C with stable repeatability. This study presents a promising avenue for the design and development of high-end anticounterfeiting devices for advanced applications.