Dynamic metal-ligand coordination enables a hydrogel with rewritable dual-mode pattern display.

The realization of dual-mode information display in the same material is of great significance to the expansion of information capacity and the improvement of information security. However, the existing systems lose the ability to re-encode information once they are constructed. Here, dynamic metal-ligand coordination is introduced into a novel hydrogel-based optical platform that allows rewritable dual-mode information display.

Brush-Like Polymeric Gels Enabled Photonic Crystals toward Ultrasensitive Cosolvent Chromism.

Responsive photonic crystals (RPCs) exhibit dynamic chromism upon trigger by various solvents, showing potential applications in qualitative identification and quantitative analysis of multicomponent solvents. However, distinguishing similar solvents, especially traces of cosolvents, remains challenging due to the limited sensitivity of RPCs. To address this, we herein introduce brush-like polymeric gels inside photonic crystals, forming a brush-like polymeric photonic gel (BPPG) that can trace tiny component changes.

Water-sensitive fluorescent microgel inks to produce verifiable information for highly secured anti-counterfeiting.

The decryption and verification of encrypted information a simple and efficient method is always difficult and challenging in the field of information security. Herein, a series of water-sensitive fluorescent microgels are fabricated for highly secured anti-counterfeiting with authenticity identification. The initial negatively charged microgels (MG) are made up of -isopropylacrylamide (NIPAM), acrylic acid (AAc) and anthracen-9-yl acrylate (9-ANA, blue fluorescent monomer).

Dual-Mode Hydrogels with Structural and Fluorescent Colors toward Multistage Secure Information Encryption.

Constructing an anti-counterfeiting material with non-interference dual optical modes is an effective way to improve information security. However, it remains challenging to achieve multistage secure information encryption due to the limited stimulus responsiveness and color tunability of the current dual-mode materials. Herein, a dual-mode hydrogel with both independently tunable structural and fluorescent colors toward multistage information encryption, is reported.

Stimulus-responsive polymer materials toward multi-mode and multi-level information anti-counterfeiting: recent advances and future challenges.

Information storage and security is one of the perennial hot issues in society, while the further advancements of related chemical anti-counterfeiting systems remain a formidable challenge. As emerging anti-counterfeiting materials, stimulus-responsive polymers (SRPs) have attracted extensive attention due to their unique stimulus-responsiveness and charming discoloration performance. At the same time, single-channel decryption technology with low-security levels has been unable to effectively prevent information from being stolen or mimicked.

Editorial for Special Issue: Advances in Smart and Tough Hydrogels.

Smart hydrogels possess both intelligent and responsive properties, which are designed to exhibit specific responses to external stimuli such as changes in temperature, pH, or the presence of specific ions/counterions, making them "smart" or "responsive" materials [...

Transcranial Acoustic Metamaterial Parameters Inverse Designed by Neural Networks.

The objective of this work is to investigate the mapping relationship between transcranial ultrasound image quality and transcranial acoustic metamaterial parameters using inverse design methods. Our study provides insights into inverse design methods and opens the route to guide the preparation of transcranial acoustic metamaterials. The development of acoustic metamaterials has enabled the exploration of cranial ultrasound, and it has been found that the influence of the skull distortion layer on acoustic waves can be effectively eliminated by adjusting the parameters of the acoustic metamaterial.

Light-Writing and Projecting Multicolor Fluorescent Hydrogels for On-Demand Information Display.

Intelligent rewritable display systems have been long expected to reduce the heavy consumption of single-use or transient devices in the age of Internet-of-Things. However, it remains challenging to construct such systems with integrated functionality of remote control, rapid activation, multicolor and multimode display. Herein, by learning from the unique multilayer arrangement of chromatophores in chameleon skins, a promising kind of rewritable hydrogel multicolor systems is presented that can combine the merits of near-infrared (NIR) light-writing and projecting modes for on-demand information display.

Organohydrogel Actuators with Adjustable Stimulus Responsiveness for On-Demand Morphing.

Hydrogel actuators showing shape morphing in response to external stimuli are of significant interest for their applications in soft robots, artificial muscles, etc. However, there is still a lack of hydrogel actuators with adjustable stimulus responsiveness for on-demand driving. In this study, an organohydrogel actuator was prepared by a two-step interpenetrating method, resulting in the coexistence of poly(-isopropylacrylamide--4-(2-sulfoethyl)-1-(4-vinylbenzyl) pyridinium betaine) (p(NIPAM-SVBP)) hydrophilic networks and poly(lauryl methacrylate) (pLMA) hydrophobic networks with gradient distribution.

Regulating Aggregated Structures in Organohydrogels for On-Demand Information Encryption.

As one of the most promising candidates for dynamic information storage, intelligent gels with tunable optical properties under external stimuli have received great attention. The implementation of transparency variation for information display is a favorable and versatile strategy but still faces the challenge of on-demand encryption-decryption. Herein, an optical tunable organohydrogel is prepared, which has interpenetrating heterogeneous networks consisting of hydrophilic poly(,-dimethylacrylamide) (PDMA) and hydrophobic polyoctadecyl methacrylate (PSMA).

Mimicking Color-Changing Organisms to Enable the Multicolors and Multifunctions of Smart Fluorescent Polymeric Hydrogels.

Fluorescent polymer hydrogels (FPHs) are of significant interest for diverse emerging applications such as visualized sensing, smart display, camouflaging skins, soft actuators/robots, because they can synergize the features of classic fluorescent polymers and hydrogels. With great efforts in the past decades, the major challenge in this field has been believed to be not whether a given FPH of interest can be prepared but how to fabricate robust FPHs with multicolor tunability and multifunctional synergy. Such materials will conceptually minimize the contribution of passive materials to the mass and size of the final system, holding great potential to facilitate multiple applications.

Recent Progress in Smart Polymeric Gel-Based Information Storage for Anti-Counterfeiting.

Information security protection has a tremendous impact on human life, social stability and national security, leading to the rapid development of anti-counterfeiting materials and related techniques. However, the traditional stored information on hard or dry media is often static and lacks functions, which makes it challenging to deal with increasing and powerful counterfeiting technologies. Modified intelligent polymeric gels exhibit color changes and shape morphing under external stimuli, which give them great potential for applications in information storage.

Supramolecular Assembly of Shape Memory and Actuating Hydrogels for Programmable Shape Transformation.

The deformable diversity of organisms in nature has inspired the development of bionic hydrogel actuators. However, the anisotropic structures of hydrogel actuators cannot be altered after the fabrication process, which restricts hydrogel actuators to provide complex and diverse shape deformations. Herein, we propose a dual programming method to generate numerous anisotropic structures from initial isotropic gelatin-containing hydrogels; the isotropic hydrogel blocks could be first assembled into anisotropic structures based on the coil-triple helix transition of gelatin, and then, the assembled hydrogels could further be fixed into various temporary anisotropies, so that they can produce complex and diverse deformations under the stimulation of pH.

Aggregation-Induced Emissive Carbon Dots Gels for Octopus-Inspired Shape/Color Synergistically Adjustable Actuators.

Some living organisms such as the octopus have fantastic abilities to simultaneously swim away and alter body color/morphology for disguise and self-protection, especially when there is a threat perception. However, it is still quite challenging to construct artificial soft actuators with octopus-like synergistic shape/color change and directional locomotion behaviors, but such systems could enhance the functions of soft robotics dramatically. Herein, we proposed to utilize unique hydrophobic carbon dots (CDs) with rotatable surficial groups to construct the aggregation-induced emission (AIE) active glycol CDs polymer gel, which could be further employed to be interfacially bonded to an elastomer to produce anisotropic bilayer soft actuator.

Recent progress in the shape deformation of polymeric hydrogels from memory to actuation.

Shape deformation hydrogels, which are one of the most promising and essential classes of stimuli-responsive polymers, could provide large-scale and reversible deformation under external stimuli. Due to their wet and soft properties, shape deformation hydrogels are anticipated to be a candidate for the exploration of biomimetic materials, and have shown various potential applications in many fields. Here, an overview of the mechanisms of shape deformation hydrogels and methods for their preparation is presented.

A Urease-Containing Fluorescent Hydrogel for Transient Information Storage.

The improper handling of decrypted information can lead to the leakage of confidential data. Thus, there is increasing interest in the development of self-erasing decrypted data. Herein, we report a urease-containing fluorescent hydrogel for multistage information security protection.

Ionic Strength and Thermal Dual-Responsive Bilayer Hollow Spherical Hydrogel Actuator.

As one of the most promising intelligent materials, polymeric hydrogel actuators could produce reversible shape change upon external stimuli. Although complex shape deformation from 2D to 3D have been achieved, the realization of actuating behavior from 3D to 3D is still a significant challenge. Herein, an effective strategy to develop a novel bilayer hollow spherical hydrogel actuator is proposed.

Antifreezing and Stretchable Organohydrogels as Soft Actuators.

Inspired by the freezing tolerance performances found in living creatures, an effect approach is presented to develop novel antifreezing polymeric organohydrogel actuators. Through construction of a bilayer hydrogel including a nonresponsive polyacrylamide (PAAm) layer and a pH-responsive polyacrylic acid (PAA) layer in the presence of a mixed solvent of water and glycerol, organohydrogel actuators that could produce various shape deformations at subzero temperatures have been achieved, and the actuating speed could be tuned by adjusting the temperature and the ratio between glycerol and water. Moreover, a series of application demonstrations including a weightlifting robot, artificial valve, and robotic arm have been displayed.

Supramolecular Fabrication of Complex 3D Hollow Polymeric Hydrogels with Shape and Function Diversity.

Inspired by the high importance of hollow structures in nature such as blood vessels and bamboos in matter transportation, properties enhancement, or even survival of living creatures, the creation of hollow materials remains of considerable interest. However, constructing hollow unique living-like soft and wet polymeric hydrogels with desirable structures and functionalities is still a big challenge. Here, we reported a robust and effective strategy to fabricate complex three-dimensional (3D) hollow polymeric hydrogel with designed shape and function diversity on the basis of supramolecular interactions.

Bioinspired Synergistic Fluorescence-Color-Switchable Polymeric Hydrogel Actuators.

Many living organisms have amazing control over their color, shape, and morphology for camouflage, communication, and even reproduction in response to interplay between environmental stimuli. Such interesting phenomena inspire scientists to develop smart soft actuators/robotics via integrating color-changing functionality based on polymer films or elastomers. However, there has been no significant progress in synergistic color-changing and shape-morphing capabilities of life-like material systems such as hydrogels.

Recent Progress in Biomimetic Anisotropic Hydrogel Actuators.

Polymeric hydrogel actuators refer to intelligent stimuli-responsive hydrogels that could reversibly deform upon the trigger of various external stimuli. They have thus aroused tremendous attention and shown promising applications in many fields including soft robots, artificial muscles, valves, and so on. After a brief introduction of the driving forces that contribute to the movement of living creatures, an overview of the design principles and development history of hydrogel actuators is provided, then the diverse anisotropic structures of hydrogel actuators are summarized, presenting the promising applications of hydrogel actuators, and highlighting the development of multifunctional hydrogel actuators.

pH and Thermo Dual-Responsive Fluorescent Hydrogel Actuator.

As one of the most important smart materials, fluorescent hydrogel actuators can produce both color and shape changes under external stimuli. In the present work, an effective approach to develop a novel fluorescent hydrogel actuator with pH and thermo dual responsiveness is proposed. Through incorporating pH-responsive perylene tetracarboxylic acid (PTCA), which is a typical fluorescent moiety with aggregation-caused quenching (ACQ) effect, into an anisotropic poly(N-isopropylacrylamide)-polyacrylamide (PNIPAm-PAAm) structure, the obtained hydrogel exhibits stable thermoresponsive shape deformation and switchable fluorescence performance upon a pH trigger.

Shape Memory Hydrogels with Simultaneously Switchable Fluorescence Behavior.

Realization of shape memory process in polymeric hydrogels at ambient condition is a significant development to shape memory materials. The sound understanding of the dynamic shape memory process is fundamentally important but limited. Here, a novel shape memory hydrogel with simultaneously switchable fluorescence behavior is developed.

A Novel Anisotropic Hydrogel with Integrated Self-Deformation and Controllable Shape Memory Effect.

Although shape memory polymers have been highlighted widely and developed rapidly, it is still a challenging task to realize complex temporary shapes automatically in practical applications. Herein, a novel shape memory hydrogel with the ability of self-deformation is presented. Through constructing an anisotropic poly(acrylic acid)-polyacrylamide (PAAc-PAAm) structure, the obtained hydrogel exhibits stable self-deformation behavior in response to pH stimulus, and the shapes that formed automatically can be fixed by the coordination between carboxylic groups and Fe ; therefore, self-deformation and shape memory behaviors are integrated in one system.