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Integrating responsive photonic crystals (RPCs) and quantum dots (QDs) effectively to realize multimode dynamic color regulation is of great significance for promoting advances in color display science. Herein, a new type of flexible dynamic color display with multimode reversible switching between transparent and colorful states based on the combination of RPCs and CdTe QDs is designed. This unique system is fabricated by encapsulating a thin layer of ordered arrays of SiO2@CdTe@SiO2 (SQS) colloids with poly(dimethylsiloxane) (PDMS), which generates an elastic film with sandwiched structure of PDMS/SQS/PDMS. Owing to the similarity in the optical properties of PDMS and SQS, the display is highly transparent in the normal state. Moreover, the resultant flexible display exhibits obvious change in color by mechanical stimuli or UV exposure. Finally, the ability to display joints motion amplitudes of human body as well as the applications in advanced security is demonstrated. [ABSTRACT FROM AUTHOR]

Counterfeiting is a growing global issue causing severe negative impacts on the social economy and posing serious security threats to individuals and communities. However, the current anticounterfeiting technologies are relatively well known to fakers and lack sufficient security owing to the development and commercialization of high‐resolution equipment. Thus, designing new anticounterfeiting materials and systems is urgently needed. Photonic crystals (PCs) with vivid structural colors are promising materials for advanced security applications because of their unique optical characteristics. In particular, responsive PCs (RPCs), whose optical signals can be readily adjusted by external stimuli, are expected to provide improved security and may be used to determine the authenticity of banknotes, documents, and drugs. In this review, the strategies are summarized for designing RPCs, including filling responsive materials into the interstitial space of periodic photonic structures and using responsive materials as construction blocks of PCs. Subsequently, the latest progress in developing RPCs constructed for optical encryption and information security is discussed in detail. Finally, the challenges and outlook of using RPCs for optical encryption technologies are presented. [ABSTRACT FROM AUTHOR]

Abstract: As an external stimulus for stimuli‐responsive chromic materials, a magnetic field has the benefits of contactless control, instant action, and ease of integration into electronic devices. Hence, the development of a magnetically responsive photonic crystal provides a new platform for color displays. However, magnetically controlled display systems have been primarily limited to liquid systems of colloidal crystals; their application to solid chromic systems has been difficult because the ordered array structure is fixed by a polymer network. A novel solid magnetochromic photonic hydrogel is developed that enables colorimetric responses to an alternating magnetic field (AMF). This notable magnetochromic performance is attributed to the superior magnetothermal effect of 1D aggregates of magnetic chains fixed in a thermosensitive hydrogel. The AMF‐responsive magnetic hydrogel exhibits excellent stability for repeated use. This study presents a basis for the development of responsive solid materials with new optical effects for future chromatic applications. [ABSTRACT FROM AUTHOR]