Information security is closely related to people's lives, social stability and even national security. In the past few decades, in response to increasingly powerful counterfeiting technology, various anti-counterfeiting materials and related anti-counterfeiting technology have developed rapidly. However, information stored based on traditional dry or hard materials is often displayed in a static form and is easily cracked. Therefore, there is an urgent need to develop new information anti-counterfeiting materials and corresponding encryption-decryption strategies to improve the security level of information. Smart polymer gels have a three-dimensional network structure that can be designed and modified. Through the endowment of functions, this type of material has huge application prospects and research value in various fields such as soft robotics, tissue engineering, and bionic skin. Especially when exposed to specific external stimuli such as light, heat, electricity, magnetism, mechanical force or chemical substances, the color or shape changes of smart polymer gels make this type of material promising for application in the field of information anti-counterfeiting.
The Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences Intelligent Polymer Materials Team has long been engaged in the bionic controllable construction of polymer hydrogels and its application in flexible actuation and sensing, fluorescent anti-counterfeiting and other fields. . Recently, Researcher Chen Tao and Associate Researcher Le Xiaoxia published a review titled "Recent Progress in Smart Polymeric Gel-based Information Storage for Anti-counterfeiting" on Advanced Materials (DOI: 10.1002/adma.202201262, as shown in Figure 1).
Figure 1 Construction and application of intelligent polymer gel-based information anti-counterfeiting materials
The key to constructing information storage devices based on polymer gel is how to realize the adjustable optical properties of intelligent gel (Figure 2). The optical properties of materials are mainly reflected in their ability to absorb, reflect and transmit light, that is, differences in transparency, color, luminescence, etc. According to the design method, polymer gel-based information storage devices can be roughly divided into two major categories according to different optical forms: chemical color-based information storage and physical color-based information storage. Chemical colors (mainly fluorescence) are usually achieved by introducing carbon dots, organic dyes and lanthanide elements into polymer gels through physical doping or chemical grafting, while physical colors are mainly caused by the interaction between the gel and light. Interactions occur (interference/diffraction, refraction/scattering, reflection/transmission). Under certain external stimulation conditions, the corresponding optical properties change, and information can be encrypted and decrypted.
Figure 2 Optical properties (fluorescence, physical color) adjustable information storage smart polymer gel
Through multi-functional synergy, including shape memory, self-healing, and actuation, polymer gel-based information storage devices can be realized The rich changes of encrypted information from single color to multi-color, and the encryption-decryption form is further improved from single dimension to multi-dimensional. Although current gel-based smart anti-counterfeiting systems exhibit unique properties compared with other anti-counterfeiting materials, they still have some flaws that limit their further application in actual production and daily life. The information storage capacity and resolution of such materials need to be improved. To address this, existing technologies, such as inkjet printing, 4D printing and other printing technologies, can be combined. During the production process, the gel can act as "paper" or "ink" . On the other hand, gel material will inevitably swell easily when exposed to solvents and lose water and shrink in the air, causing the encrypted information to be distorted or even disappear. To address the above shortcomings, developing gels that resist swelling or water loss may be a good choice.
For anti-counterfeiting, using the simplest decryption method to identify the highest security level of encrypted information is an eternal pursuit. On the one hand, the combination of different optical properties and the synergy of other functions (such as shape memory, shape deformation, self-healing, etc.) can give the gel anti-counterfeiting system more complex and diverse encryption forms, thereby improving the level of information security. On the other hand, the use of simple stimuli (such as light, humidity and temperature) can simplify the decryption process, which will also become the future development trend of anti-counterfeiting applications.
This research was supported by National Natural Science Foundation of China (52103246), National Key Research and Development Program (2018YFC0114900), Zhejiang Provincial Natural Science Foundation (LQ22E030015), Chinese Academy of Sciences Frontier Science Key Research Program (QYZDB-SSW-SLH036) , Sino-German Cooperation International Exchange Project (M-0424) and Wang Kuancheng Education Fund (GJTD-2019-13) and other projects.
Paper link
https://doi.org/10.1002/adma.202201262
