Freeze-casted nanofiber based sponges or aerogels exhibit a hierarchical porous structure. Pore formation is only partially understood. Therefore, we studied the underlying solid templating mechanism. We were able to tailor the secondary pore size between 9.5 and 123 µm while retaining the smaller primary pores known from electrospun nanofiber membranes. To understand the effect of microstructure on the sponges' bulk properties, mass flow through the pores and interaction with the sponges' internal surface were investigated. By solely altering the sponges' microstructure we indeed found tunability in permeability by a factor 7 and in filtration efficiency by a factor of 220. Hence, pore architecture of nanofiber based sponges is a key element for their performance. The selected pullulan/PVA polymer blends and aqueous electrospinning conditions are benign and allow the facile adaptation of these ultralight highly porous sponges for a large number of applications.

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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.

Structural color caused by thin‐film interference is widespread and simple in nature. Many researchers have already showed the reversible color change of structural color system, but it is difficult to regulate dynamically with tunable intensity and viewable angle. Herein, a dynamic structural color platform is reported by combining spontaneous thin film interference and wrinkling phenomenon in nature. This robust yet low cost strategy enables large‐scale and spatially arbitrary preparation of a uniform structural color surface through the whole visible spectral range. Furthermore, the prepared isotropic and anisotropic structural colors on disordered and ordered wrinkled thin films (WTFs) exhibit different optical properties that can be precisely and reversibly regulated by ultraviolet (UV) light and near‐infrared (NIR) light irradiation. This exquisite and tunable structural color platform may find applications in information storage, smart display, anticounterfeiting and encryption.

Summary: A new superabsorbent polymer, PAMA, has been prepared in an aqueous solution using acrylamide (AM) and 2‐acrylamido‐2‐methyl‐propanesulfonic acid (AMPS) as monomers, potassium persulfate (PPS) as initiator, and N,N′‐methylenebisacrylamide (NMBA) as cross‐linker. The absorbing properties and water retention of PAMA have been investigated. It is found that the absorbency of PAMA can reach 2 451 and 119 g · g−1 in distilled water and in 0.9 wt.‐% NaCl solution, respectively. This copolymer also can absorb a large amount of pure methanol (277 g · g−1), a property that has not been reported for the other superabsorbent polymers in the literature. The swelling behavior of PAMA in some water/organic solvent mixtures and water retention of PAMA in sand have been investigated.