A Multiresponsive Anisotropic Hydrogel with Macroscopic 3D Complex Deformations

As one of the most promising smart materials, stimuli‐responsive polymer hydrogels (SPHs) can reversibly change volume or shape in response to external stimuli. They thus have shown promising applications in many fields. While considerable progress of 2D deformation of SPHs has been achieved, the realization of 3D or even more complex deformation still remains a significant challenge. Here, a general strategy towards designing multiresponsive, macroscopically anisotropic SPHs (MA‐SPHs) with the ability of 3D complex deformations is reported. Through a local UV‐reduction of graphene oxide sheets (GOs) with a patterned fashion in the GO‐poly(N‐isopropylacrylamide) (GO‐PNIPAM) composite hydrogel sheet, MA‐SPHs can be achieved after the introduction of a second poly(methylacrylic acid) network in the unreduced part of GO‐PNIPAM hydrogel sheet. The resulting 3D MA‐SPHs can provide remote‐controllable light‐driven, as well as thermo‐, pH‐, and ionic strength‐triggered multiresponsive 3D complex deformations. Approaches in this study may provide new insights in designing and fabricating intelligent soft materials for bioinspired applications.     

Dual Functional Titanium Hydride Particles for Anti-Ultraviolet and Anti-Oxidant Applications

TiO₂ is a typical anti-ultraviolet agent in sunscreen cream, but it suffers from a lack of anti-oxidant activity for scavenging reactive oxygen species. Other traditional sunscreen ingredients, such as C₆₀ and ferulic acid, have moderate antioxidant and UV protection capabilities, and the products do not provide further UV protection. Herein, titanium hydride (TiH_1.97) particles with dual functions of anti-oxidant and anti-ultraviolet are presented as an active material to remove the highly oxidizing and harmful hydroxide free radicals from the skin surface. Owing to the active hydrogen in TiH₂, it shows great potential to eliminate hydroxyl radicals, and the rate is roughly proportional to the exposed surface area (50% /20 min). Together with the biocompatibility of the in situ formed TiO₂, which has a strong ability to absorb ultraviolet light during OH radical scavenging. At the same time, adding titanium hydride to sunscreen also enhances sun protection. The SPF value of sunscreen containing 1% titanium hydride and 20% titanium dioxide can reach 31.8, which exceeds the 20% titanium dioxide (15) by more than twofold. Therefore, titanium hydride with anti-ultraviolet and antioxidant functions can be regarded as a promising and safe ingredient for sunscreen cream.     

Inkjet‐Printable Amphiphilic Polydiacetylene Precursor for Hydrochromic Imaging on Paper

Hydrochromic materials find great utility in a wide range of applications including humidity sensing and measuring the water contents of organic solvents, as well as substrates for rewritable paper and human sweat pore mapping. Herein, an inkjet printable diacetylene (DA) is described that can be transformed by UV irradiation to a hydrochromic‐conjugated polymer on conventional paper. Specifically, an amphiphilic DA that contains an ­imidazolium ion head‐group is found to be compatible with a common office inkjet printer. Various computer‐designed images are printed on paper using this substance. UV irradiation of the printed images results in the generation of blue‐colored images associated with formation of a polydiacetylene (PDA). The resolutions of the images are almost identical to those generated using a conventional black ink. Importantly, the printed images undergo a blue‐to‐red color change upon exposure to water and the hydrochromism is found to be temperature dependent. The facile color change that occurs near body ­temperatures enables use of the hydrochromic PDA‐coated paper for rapid and precise mapping of human sweat pores from fingers, palms, and feet.     

Colorimetric Detection of Warfare Gases by Polydiacetylenes Toward Equipment‐Free Detection

Rationally designed polydiacetylene (PDA) molecules have been developed for rapid, selective, sensitive, and convenient colorimetric detection of organophosphate (OP) nerve agents, a mass destruction weapon. Oxime (OX) functionality was incorporated into diacetylene molecules to utilize its strong affinity toward organophosphates. The diacetylene molecules having an OX functional group (OX‐PDA) were self‐assembled to form PDA liposomes in an aqueous solution. Upon exposure to organophosphate nerve agent simulants, OX at the OX‐PDA liposome surface interacts with nerve agent simulants, which results in intraliposomal repulsive stress due to steric repulsion between OP‐occupied OX units at the liposome surface as well as interliposomal aggregation induced by increased hydrophobicity of the liposome surface via OP‐OX complex formation. The resulting intra‐ and interliposomal stress causes disturbance of the conjugated backbone of OX‐PDA, producing color change as a label‐free and sensitive sensory signal. The effects of molecular structure on selectivity and sensitivity of OX‐PDA liposome solution, OX‐PDA liposome‐embedded agarose gels, and OX‐PDA liposome‐coated cellulose acetate membranes were systematically investigated. The optimized OX‐PDA liposome in the solid state showed selective and rapid optical transition upon exposure down to 160 ppb of diisopropylfluorophosphate (DFP), a nerve agent simulant. The results provide an insightful molecular design principle of PDA‐based colorimetric sensor and suggest portable sensory patches for rapid, selective, sensitive, and convenient colorimetric detection of organophosphate nerve agents.     

Bio‐Inspired Photonic Materials: Prototypes and Structural Effect Designs for Applications in Solar Energy Manipulation

Natural creatures have evolved elaborate photonic nanostructures on multiple scales and dimensions in a hierarchical, organized way to realize controllable absorption, reflection, or transmitting the desired wavelength of the solar spectrum. A bio‐inspired strategy is a powerful and promising way for solar energy manipulation. This feature article presents the state‐of‐the‐art progress on bio‐inspired photonic materials on this particular application. The article first briefly recalls the physical origins of natural photonic effects and catalogues the typical natural photonic prototypes including light harvesting, broadband reflection, selective reflection, and UV/IR response. Next, typical applications are categorized into two primary areas: solar energy utilization and reflection. Recent advances including solar‐to‐electricity, solar‐to‐fuels, solar‐thermal (e.g., photothermal converters, infrared detectors, thermoelectric materials, smart windows, and solar steam generation) are highlighted in the first part. Meanwhile, solar energy reflection involving infrared stealth, radiative cooling, and micromirrors are also addressed. In particular, this article focuses on bioinspired design principles, structural effects on functions, and future trends. Finally, the main challenges and prospects for the next generation of bioinspired photonic materials are discussed, including new design concepts, emerging ideas, and possible strategies.     

Near‐Infrared Light‐Driven,Highly Efficient Bilayer Actuators Based on Polydopamine‐Modified Reduced Graphene Oxide

Near‐infrared (NIR) light‐driven bilayer actuators capable of fast, highly efficient, and reversible bending/unbending motions toward periodic NIR light irradiation are fabricated by exploiting the photothermal conversion and humidity‐sensitive properties of polydopamine‐modified reduced graphene oxide (PDA‐RGO). The bilayer actuator comprises a PDA‐RGO layer prepared by a filtration method, and this layer is subsequently spin‐coated with a layer of UV‐cured Norland Optical Adhesive (NOA)‐63. Given the hydrophilicity of PDA, the PDA‐RGO layer can absorb water to swell and lose water to shrink. The intrinsic NIR absorbance of RGO sheets convertes NIR light into thermal energy, which transfers the humidity‐responsive PDA‐RGO layer to be NIR light‐responsive. Considering that the shape of the NOA‐63 layer remains unchanged under NIR light, periodic NIR light irradiation leads to asymmetric shrinkage/expansion of the bilayer, which enables fast and reversible bending/unbending motions of the bilayer actuator. We demonstrate that compared with a poly(ethylenimine)‐modified graphene oxide layer, the PDA‐RGO layer is unique in fabricating highly efficient bilayer actuators. A NIR light‐driven walking device capable of performing quick worm‐like motion on a ratchet substrate is built by connecting two polyethylene terephthalate plates as claws on opposite ends of the PDA‐RGO/NOA‐63 bilayer actuator.     

UV‐Triggered Polydopamine Secondary Modification: Fast Deposition and Removal of Metal Nanoparticles

Since the first report in 2007, polydopamine (PDA) coating has shown great potential as a general and versatile method to create functional nanocoatings on arbitrary substrates. Slow kinetics and poor controllability of the coating and secondary modification processes, however, have limited the further development of this attractive method. In this work, it is demonstrated that UV irradiation at 365 nm significantly accelerates the process of secondary modification of a PDA‐coated surface. The kinetics of both thiol and amine modifications of PDA are increased 12‐fold via UV irradiation, while the kinetics of metal ion reduction at the PDA interface is increased more than 550 times. Moreover, it is demonstrated that irradiating a PDA/metal nanoparticle composite surface with UV light at 254 nm leads to dissolution of the deposited metal nanoparticles (MNPs). Finally, grayscale metallic patterns, dynamic deposition, and removal of MNPs on PDA surface are realized with the proposed method.     

Mechanically Drawable Thermochromic and Mechanothermochromic Polydiacetylene Sensors

Recently, the development of directly writable techniques for depositing functional materials on solid substrates has received great attention. These pen‐on‐paper approaches enable generation of diverse patterned images on solid substrates in a flexible, easy handling, and inexpensive manner. Herein, the development of a directly writable conjugated polymer is described. Mechanically, drawable colorimetric polydiacetylene (PDA)–wax composites are readily fabricated by using a simple mixing‐molding method. Images are mechanically drawn on a paper substrate using the PDA–wax composites, display thermochromism, and mechanothermochromism. The thermochromic transition temperature is dependent on the melting point of the wax and, as a result, can be precisely controlled by the type of wax used. Optical microscopic analysis shows that formation of the DA–wax composite involves movement of wax molecules into a single diacetylene (DA) crystal. This process results in growth of the crystal. Importantly, the PDA crystal, obtained after UV light irradiation, undergoes significant shrinkage upon heating because of the release of monomers and the embedded wax molecules from the crystal. The release of these molecules creates void in the PDA supramolecules, allowing the PDA chains to undergo C–C bond rotation and hence the blue‐to‐red color transition.     

Mimicking Drug–Substrate Interaction: A Smart Bioinspired Technology for the Fabrication of Theranostic Nanoprobes

Versatile bioinspired strategies are urgently needed to fabricate high‐performance nanoprobes for biomedical application. Herein, a novel bioinspired technology of mimicking drug–substrate interaction is reported for the fabrication of high‐performance nanoprobes. As a proof of concept, a multifunctional bovine serum albumin (BSA)‐MnO₂ nanoparticle‐based nanoplatform is strategically engineered via mimicking the disinfection process of KMnO₄ in an extremely facile way. The prepared BSA‐MnO₂ nanoparticles possess sub‐10 nm and uniform size, excellent colloidal stability, and impressive T ₁ relaxivity of 7.9 mm ^?1 s^?1. The proposed nanoprobe could not only be employed as a high‐performance magnetic resonance imaging (MRI) agent for tumor and renal imaging but can also provide a platform for integrating therapeutic strategies toward tumors. The universal strategy could also be easily extended to the fabrication of other nanoprobes for MR imaging in vivo using other bioactive proteins including ovalbumin and transferrin. This work will open a new way for the development of biomaterials in biomedicine applications.     

基于PDA的公路养护巡检数据采集系统的研制

人工采集公路养护巡检数据不仅效率低、及时性差、数据易出错且不能获得GPS（全球定位系统）、路况图像等信息。文中提出的基于PDA（个人数字助理）的公路养护巡检数据采集系统设计方案,可解决人工采集巡检数据所存在的问题。该系统经实际应用证明,巡检数据不仅能及时传送,且数据准确性高。该系统还具有适应性强、功能强大、操作简便等特点,可在行业内推广应用。     

Non‐Equilibrium,Light‐Adaptive,Steady‐State Reconfiguration of Mechanical Patterns in Bioinspired Nanocomposites

Bioinspired nanocomposites have made great progress for the fabrication of mechanical high‐performance structural materials, but their properties have thus far been engineered with a focus on static behavior. This contrasts profoundly with the dynamic reconfiguration often observed in living tissues. Here, a first concept is introduced for steady‐state, light‐adaptive reconfiguration of mechanical patterns in bioinspired nanocomposites under dissipative out‐of‐equilibrium conditions. This is realized for green, waterborne cellulose nanofibril/polymer nanopapers by achieving a heterogeneous activation of a photothermal effect. To this end, predefined mechanical patterns are designed by top‐down lamination of bottom‐up engineered bioinspired nanocomposites containing thermoreversible hydrogen bonds, as well as spatially selectively incorporated single‐walled carbon nanotubes for photothermal response. Global irradiation leads to localized photothermal softening by cascading light to heat, and to the dynamization and breakage of the thermoreversible supramolecular bonds, leading to macroscopic reconfiguration and even inversion of mechanical stiff/soft patterns. The altered configuration is only stable in a dissipative steady state and relaxes to the ground state once light is removed. The strategy presents a new approach harnessing the capabilities from top‐down and bottom‐up structuring, and by interfacing it with non‐equilibrium adaptivity concepts, it opens avenues for hierarchical bioinspired materials with anisotropic response in global fields.     

Network Polydiacetylene Films: Preparation,Patterning, and Sensor Applications

The synthesis, characterization, and functionalization of polydiacetylene (PDA) networks on solid substrates is presented. A highly transparent and cross‐linked diacetylene film of DCDDA‐bis‐BA on a solid substrate is prepared first by tailoring the monomers with organoboronic acid moieties as pendant side groups and consequent drop‐casting and dehydration steps. Precisely controlled thermal curing plays a key role to obtain properly aligned diacetylene monomers that are closely packed between the boronic acid derived anhydride structures. A second cross‐linking, which occurs by polymerization of the diacetylene monomers with UV irradiation, induces a transparent to blue color shift. Accordingly, colored image patterns are readily available by polymerization through a photomask. The color change that takes place as a response to various organic solvents can be simply detected by naked eyes. The thermofluorescence change of PDA networks is demonstrated to be an effective method by which to obtain the microscale temperature distribution of thermal systems. The ease of film formation and stress‐induced blue‐to‐red color change with a simultaneous fluorescence generation features of the network structure should find a great utility in a wide range of chemical and thermal sensing platforms.     

Reversible Quadruple Switching with Optical,Chiroptical, Helicity,and Macropattern in Self‐Assembled Spiropyran Gels

Enantiomeric glutamate gelators containing a spiropyran moiety are designed and found to self‐assemble into a nanohelix through gelation. Upon alternating UV and visible light irradiation, the spiropyran experiences a reversible change between a blue zwitterionic merocyanine state and a colorless closed ring state spiropyran in supramolecular gels. This photochromic switch causes a series of subsequent changes in the optical, chiroptical, morphological properties from supramolecular to macroscopic levels. While the solution of the gelator molecules does not show any circular dichroism (CD) signal in the region of 250–700 nm due to the fact that the chromophore is far from the chiral center, the gel shows chiroptical signals such as CD and circularly polarized luminescence (CPL) because of the chirality transfer by the self‐assembly. These signals are reversible upon alternating UV/vis irradiation. Therefore, a quadruple optical and chiroptical switch is developed successfully. During such process, the self‐assembled nanostructures from the enantiomeric supramolecular gels also undergo a reversible change between helices and fibers under the alternating UV and visible light trigger. Furthermore, a rewritable material fabricated from their xerogels on a glass is developed. Such rewritable material can be efficiently printed over 30 cycles without significant loss in contrast and resolution using UV and visible light.     

Materials and Device Designs for an Epidermal UV Colorimetric Dosimeter with Near Field Communication Capabilities

Ultraviolet (UV) solar radiation is a leading cause of skin disease. Quantitative, continuous knowledge of exposure levels can enhance awareness and lead to improved health outcomes. Devices that offer this type of measurement capability in formats that can seamlessly integrate with the skin are therefore of interest. This paper introduces materials, device designs, and data acquisition methods for a skin‐like, or “epidermal,” system that combines colorimetric and electronic function for precise dosimetry in the UV‐A and UV‐B regions of the spectrum, and for determination of instantaneous UV exposure levels and skin temperature. The colorimetric chemistry uses (4‐phenoxyphenyl)diphenylsulfonium triflate (PPDPS‐TF) with crystal violet lactone (CVL) and Congo red for UV‐A and UV‐B operation, respectively, when integrated with suitable optical filters. Coatings of poly(ethylene‐vinylacetate) (PEVA) protect the functional materials from sunscreen and other contamination. Quantitative information follows from automated L*a*b* color space analysis of digital images of the devices to provide accurate measurements when calibrated against standard nonwearable sensors. Techniques of screen printing and lamination allow aesthetic designs and integration with epidermal near field communication platforms, respectively. The result is a set of attractive technologies for managing UV exposure at a personal level and on targeted regions of the body.     

Polydopamine‐Graphene Oxide Flame Retardant Nanocoatings Applied via an Aqueous Liquid Crystalline Scaffold

A highly effective flame retardant (FR) nanocoating was developed by conducting oxidative polymerization of dopamine monomer within an aqueous liquid crystalline (LC) graphene oxide (GO) scaffold coating. Due to its high water content, the LC scaffold coating approach facilitated fast transport and polymerization of dopamine precursors into polydopamine (PDA) within the water swollen interlayer galleries. Uniform and periodically stacked (14.5 Å d‐spacing) PDA/GO nanocoatings could be universally applied on different surfaces, including macroporous flexible polyurethane (PU) foam and flat substrates such as silicon wafers. Remarkably, PDA/GO coated PU foam exhibited highly efficient flame retardant performance reflected by a 65% reduction in peak heat release rate at 5 wt% PDA/GO loading in an 80 nm thick coating. While many physically mixed flame retardants are usually detrimental to the mechanical properties of the foam, the PDA/GO coating did not affect mechanical properties substantially. In addition, the PDA/GO coatings were stable in water due to the intrinsic adhesion capability of PDA and the transformation of GO to the more hydrophobic reduced GO form. Given that PDA is produced from dopamine, a molecule prevalent in nature, these findings suggest that significant opportunities exist for new polymeric FRs derived from other natural catechols.     

Multidimension‐Controllable Synthesis of Ant Nest‐Structural Electrode Materials with Unique 3D Hierarchical Porous Features toward Electrochemical Applications

Hierarchical porous materials (HPM) have been widely used to enhance electrochemical performance in different fields of application, since their porous structures benefit electrolyte infiltration and ion diffusion. However, the realization of multidimension‐controllable synthesis of HPM, including material category, material components, supporting substrates, as well as pore sizes/distributions, is still a huge challenge. Herein, a novel concept is proposed, for the first time, on the geometry structure of HPM bioinspired by natural ant nests, which features 3D interlaced and well‐interconnected porous structures. Moreover, a facile and universal approach is developed to the multidimension‐controllable synthesis of ant nest‐structural HPM. Further investigation shows that the in situ construction of carbon‐based ant nests onto porous current collectors to fabricate the integrated electrode for supercapacitors could induce nearly 70% and 45% enhancement on the specific capacitance compared to the common powder and freestanding materials, respectively. Moreover, this synthesis route can be facilely extended to obtain the ant nest‐structural CuO_x, which exhibits fivefold enhancement in sensitivity for glucose detection. Such biomimetic hierarchical porous architectures are of great significance in the field of electrochemical applications.     

A Direct,Multiplex Biosensor Platform for Pathogen Detection Based on Cross‐linked Polydiacetylene (PDA) Supramolecules

This study focuses on the development of a multiplex pathogen‐detection platform based on polydiacetylene (PDA) using a novel immobilization procedure. PDA liposome‐based solid sensors have a critical drawback as the PDA liposomes are not stably immobilized onto the solid substrate. Therefore, to overcome this problem, an interlinker, ethylenediamine, is introduced, which acts as a cross‐linker between individual PDA liposomes. The quantity of ethylenediamine added was optimized to 1 mM, as measured by the fluorescence signal emitted by the stably immobilized PDA liposomes, a concentration at which the fluorescence signal is 10 times higher than for the resulting PDA chips made without the interlinker. This procedure is used to manufacture PDA liposome‐based multiplex biosensor arrays for well‐known water and food‐borne pathogens. The fabricated biosensor was able to perform the simultaneous and quantitative detection of 6 species of pathogens. As such, the results demonstrated from this research can be exploited for the development of more advanced PDA‐based biosensors and diagnostics.     

Universal Colorimetric Detection of Nucleic Acids Based on Polydiacetylene (PDA) Liposomes

A universal colorimetric method for the detection of nucleic acids, based on ionic interactions by polydiacetylene (PDA) liposomes, is described. Primary and quaternary amine‐modified diacetylene monomers were synthesized and used to generate positively charged PDA liposomes. The resulting PDA sensors showed a dramatic color change from blue to red upon the addition of nucleic acids amplified by using the polymerase chain reaction (PCR) due to the stimuli caused by ionic interactions between the positively charged PDA and negatively charged phosphate backbone of the nucleic acids. The color change that takes place can be simply detected by the naked eye. Compared with quaternary amine‐functionalized PDA vesicles, the primary amine‐functionalized PDA underwent a more intense color transition under optimized conditions. By using the PDA‐based colorimetric sensor, nucleic acids amplified by common PCR reaction, whose typical concentration is around 100 nM, can be readily detected. Since implementation of this universal colorimetric method is simple, rapid and does not require any sophisticated instrumentation, it should have greatly enhanced applications as a technology for DNA diagnosis.     

Pressure/Temperature Dual-Responsive Cellulose Nanocrystal Hydrogels for On-Demand Schemochrome Patterning

Cellulose nanocrystal (CNC) based optical devices with adjustable schemochrome have attracted immense interest. However, most of the previously reported structural colored CNC-based materials can only achieve simple stress-induced color change, which have difficulty achieving multimode control of complex patterning that can be accurately identified. Here, inspired by the nanostructure-based color-changing mechanism of neon tetra, this study presents a pressure/temperature dual-responsive CNC-based schemochrome hydrogel with adjustable dynamic chiral nematic structure. By incorporating abundant interfacial noncovalent interactions, dynamic correlations between adjustable helical pitch of the vertically stacked cholesteric liquid crystalline (LC) phase and responsiveness of flexible thermosensitive substrate are established, which further enable wide-range optical characteristic (12°–213° in HSV color model and 421–734 nm in the UV–Vis spectra) and identifiable visualized patterning. The resultant hydrogels are applied in proof-of-concept demonstrations of on-demand schemochrome patterning, including customizable patterned dual-encryption label, smart digital display, temperature monitor, and intelligent recognition/control system. This study envisages that the bioinspired construction of structural colored nanomaterials will have promising applications in smart responsive photonic equipment including smart display, anticounterfeiting, and intelligent control systems.     

Transparent Nacre‐like Composites Toughened through Mineral Bridges

Bulk materials with remarkable mechanical properties have been developed by incorporating design principles of biological nacre into synthetic composites. However, this potential has not yet been fully leveraged for the fabrication of tough and strong materials that are also optically transparent. In this work, a manufacturing route that enables the formation of nacre‐like mineral bridges in a bioinspired composite consisting of glass platelets infiltrated with an index‐matching polymer matrix is developed. By varying the pressure applied during compaction of the glass platelets, composites with tunable levels of mineral bridges and platelet interconnectivity can be easily fabricated. The effect of platelet interconnectivity on the mechanical strength and fracture behavior of the bioinspired composites is investigated by performing state‐of‐the‐art fracture experiments combined with in situ electron microscopy. The results show that the formation of interconnections between platelets leads to bulk transparent materials with an unprecedented combination of strength and fracture toughness. This unusual set of properties can potentially fulfill currently unmet demands in electronic displays and related technologies.