Highly Stable Graphene‐Based Multilayer Films Immobilized via Covalent Bonds and Their Applications in Organic Field‐Effect Transistors

Highly stable graphene oxide (GO)‐based multilayered ultrathin films can be covalently immobilized on solid supports through a covalent‐based method. It is demonstrated that when (3‐aminopropyl) trimethoxysilane (APTMS), which works as a covalent cross‐linking agent, and GO nanosheets are assembled in an layer‐by‐layer (LBL) manner, GO nanosheets can be covalently grafted on the solid substrate successfully to produce uniform multilayered (APTMS/GO)N films over large‐area surfaces. Compared with conventional noncovalent LBL films constructed by electrostatic interactions, those assembled using this covalent‐based method display much higher stability and reproducibility. Upon thermal annealing‐induced reduction of the covalent (APTMS/GO)N films, the obtained reduced GO (RGO) films, (APTMS/RGO)N, preserve their basic structural characteristics. It is also shown that the as‐prepared covalent (APTMS/RGO)N multilayer films can be used as highly stable source/drain electrodes in organic field‐effect transistors (OFETs). When the number of bilayers of the (APTMS/RGO)N film exceeds 2 (ca. 2.7 nm), the OFETs based on (APTMS/RGO)N electrodes display much better electrical performance than devices based on 40 nm Au electrodes. The covalent protocol proposed may open up new opportunities for the construction of graphene‐based ultrathin films with excellent stability and reproducibility, which are desired for practical applications that require withstanding of multistep post‐production processes.     

Hierarchical Chemical Bonds Contributing to the Intrinsically Low Thermal Conductivity in α‐MgAgSb Thermoelectric Materials

Understanding the lattice dynamics and phonon transport from the perspective of chemical bonds is essential for improving and finding high‐efficiency thermoelectric materials and for many applications. Here, the coexistence of global and local weak chemical bonds is elucidated as the origin of the intrinsically low lattice thermal conductivity of non‐caged structure Nowotny–Juza compound, α‐MgAgSb, which is identified as a new type of promising thermoelectric material in the temperature range of 300–550 K. The global weak bonds of the compound lead to a low sound velocity. The unique three‐centered Mg? Ag? Sb bonds in α‐MgAgSb vibrate locally and induce low‐frequency optical phonons, resulting in “rattling‐like” thermal damping to further reduce the lattice thermal conductivity. The hierarchical chemical bonds originate from the low valence electron count of α‐MgAgSb, with the feature shared by Nowotny–Juza compounds. Low lattice thermal conductivities are therefore highly possible in this series of compounds, which is verified by phonon and bulk modulus calculations on some of the compositions.     

Rational Design of Spider Silk Materials Genetically Fused with an Enzyme

Enzyme immobilization is an attractive route for achieving catalytically functional surfaces suitable for both continuous and repeated use. Herein, genetic engineering is used to combine the catalytic ability of a xylanase with the self‐assembly properties of recombinant spider silk, realizing silk materials with enzymatic activity. Under near‐physiological conditions, soluble xylanase‐silk fusion proteins assembled into fibers displaying catalytic activity. Also, a xylanase‐silk protein variant with the silk part miniaturized to contain only the C‐terminal domain of the silk protein formed fibers with catalytic activity. The repertoire of xylanase‐silk formats is further extended to include 2D surface coatings and 3D foams, also being catalytically active, showing the versatile range of possible silk materials. The stability of the xylanase‐silk materials is explored, demonstrating the possibility of storage, reuse, and cleaning with ethanol. Interestingly, fibers can also be stored dried with substantial residual activity after rehydration. Moreover, a continuous enzymatic reaction using xylanase‐silk is demonstrated, making enzymatic batch reactions not the sole possible implementation. The proof‐of‐concept for recombinantly produced enzyme‐silk, herein shown with a xylanase, implies that also other enzymes can be used in similar setups. It is envisioned that the concept of enzyme‐silk can find its applicability in, for example, multienzyme reaction systems or biosensors.     

Electric‐Field‐Assisted Growth of Vertical Graphene Arrays and the Application in Thermal Interface Materials

Owing to the development of electronic devices moving toward high power density, miniaturization, and multifunction, research on thermal interface materials (TIMs) is become increasingly significant. Graphene is regarded as the most promising thermal management material owing to its ultrahigh in‐plane thermal conductivity. However, the fabrication of high‐quality vertical graphene (VG) arrays and their utilization in TIMs still remains a big challenge. In this study, a rational approach is developed for growing VG arrays using an alcohol‐based electric‐field‐assisted plasma enhanced chemical vapor deposition. Alcohol‐based carbon sources are used to produce hydroxyl radicals to increase the growth rate and reduce the formation of defects. A vertical electric field is used to align the graphene sheets. Using this method, high‐quality and vertically aligned graphene with a height of 18.7 µm is obtained under an electric field of 30 V cm^?1. TIMs constructed with the VG arrays exhibit a high vertical thermal conductivity of 53.5 W m^?1 K^?1 and a low contact thermal resistance of 11.8 K mm² W^?1, indicating their significant potential for applications in heat dissipation technologies.     

All‐Plastic‐Materials Based Self‐Charging Power System Composed of Triboelectric Nanogenerators and Supercapacitors

Triboelectric nanogenerators (TENG) are a possible power source for wearable electronics, but the conventional electrode materials for TENG are metals such as Cu and Al that are easy to be oxidized or corroded in some harsh environments. In this paper, metal electrode material is replaced by an electrical conducting polymer, polypyrrole (PPy), for the first time. Moreover, by utilizing PPy with micro/nanostructured surface as the triboelectric layer, the charge density generated is significantly improved, more superior to that of TENG with metals as the triboelectric layer. As this polymer‐based TENG is further integrated with PPy‐based supercapacitors, an all‐plastic‐materials based self‐charging power system is built to provide sustainable power with excellent long cycling life. Since the environmental friendly materials are adopted and the facile electrochemical deposition technique is applied, the new self‐charging power system can be a practical and low cost power solution for many applications.     

Understanding the Mechanical Properties of Antheraea Pernyi Silk—From Primary Structure to Condensed Structure of the Protein

Antheraea pernyi (A. pernyi) silk is produced and used by “wild” silkworms to construct a cocoon, but the primary structure of its protein is rather similar to that of spider major ampullate silk used to build web and dragline. Studies on this specific silk may provide valuable knowledge about the structure‐property relationship for the whole animal silk family. In this work, A. pernyi silk fibers with few macroscale defects are obtained by forcibly reeling, and are investigated in detail. It is found that such silk fibers display breaking stress and toughness of the same magnitude as spider major ampullate silks and forcibly reeled mulberry silk. The other mechanical properties, such as elasticity, supercontraction, and the effect of water on modulus are between those of spider major ampullate silks and mulberry silk. Therefore, an interpretation of the connection between the primary structures of silk proteins and the mechanical properties of silks is proposed here based on the ordered fraction, which in turn is determined by both the protein sequence and spinning process of the silk.     

Self‐Healing Materials via Reversible Crosslinking of Poly(ethylene oxide)‐Block‐Poly(furfuryl glycidyl ether) (PEO‐b‐PFGE) Block Copolymer Films

The application of well‐defined poly(furfuryl glycidyl ether) (PFGE) homopolymers and poly(ethylene oxide)‐b‐poly(furfuryl glycidyl ether) (PEO‐b‐PFGE) block copolymers synthesized by living anionic polymerization as self‐healing materials is demonstrated. This is achieved by thermo‐reversible network formation via (retro) Diels‐Alder chemistry between the furan groups in the side‐chain of the PFGE segments and a bifunctional maleimide crosslinker within drop‐cast polymer films. The process is studied in detail by differential scanning calorimetry (DSC), depth‐sensing indentation, and profilometry. It is shown that such materials are capable of healing complex scratch patterns, also multiple times. Furthermore, microphase separation within PEO‐b‐PFGE block copolymer films is indicated by small angle X‐ray scattering (lamellar morphology with a domain spacing of approximately 19 nm), differential scanning calorimetry, and contact angle measurements.     

Highly Efficient Mechanoelectrical Energy Conversion Based on the Near‐Tip Stress Field of an Antifracture Slit Observed in Scorpions

In the field of engineering, a crack, inducing enormous mechanical energy concentration at a tip, is considered a typical kind of defect. However, it is found that, to maximize the sensitivity of slit‐based mechanoreceptors, the near‐tip stress field of “risky” crack‐shaped slits is ingeniously used by scorpions to precisely detect the cyclic loads acting on walking legs without the crack nucleation from the flaw‐like tip. As a sophisticated biological mechanoelectrical transducing microsystem, the mechanoreceptor can effectively collect mechanical energy contained in the mechanical signal through antifracture slit allays and then convert the mechanical energy into electrical energy through mechanosensory neuron. The highly efficient mechanoelectrical energy conversion mechanism is theoretically analyzed and experimentally verified in a bioinspired artificial mechanoreceptor. The results demonstrate the potential of basic “design” principles, underlying the slit‐dependent mechanoreceptor, for maximizing the electromechanical conversion efficiency of the industrial mechanoelectrical transducing microsystem such as nanogenerators, ultrasensitive mechanical sensors, self‐powered portable, and wearable electronics.     

Peptide‐Based Nanostructured Materials with Intrinsic Proapoptotic Activities in CXCR4+ Solid Tumors

Protein materials are gaining interest in nanomedicine because of the unique combination of regulatable function and structure. A main application of protein nanoparticles is as vehicles for cell‐targeted drug delivery in the form of nanoconjugates, in which a conventional or innovative drug is associated to a carrier protein. Here, a new nanomedical approach based on self‐assembling protein nanoparticles is developed in which a chemically homogeneous protein material acts, simultaneously, as vehicle and drug. For that, three proapoptotic peptidic factors are engineered to self‐assemble as protein‐only, fully stable nanoparticles that escape renal clearance, for the multivalent display of a CXCR4 ligand and the intracellular delivery into CXCR4⁺ colorectal cancer models. These materials, produced and purified in a single step from bacterial cells, show an excellent biodistribution upon systemic administration and local antitumoral effects. The design and generation of intrinsically therapeutic protein‐based materials offer unexpected opportunities in targeted drug delivery based on fully biocompatible, tailor‐made constructs.     

Femto‐Second Laser‐Based Free Writing of 3D Protein Microstructures and Micropatterns with Sub‐Micrometer Features: A Study on Voxels,Porosity, and Cytocompatibility

Femto‐second laser‐based free‐writing of complex protein microstructures and micropatterns, with sub‐micrometer features and controllability over voxel dimension, morphology, and porosity, is reported. Protein voxels including lines, spots, and micropillars are fabricated. Laser power, exposure time, z‐position, protein and photosensitizer concentrations, but not scanning speed, are important controlling parameters. A lateral fabrication resolution of ≈200 nm is demonstrated in 2D line voxels. 3D spot voxels are ellipsoids with 400 nm lateral and 1.5 μm axial dimensions. An ascending z‐stack scanning method to verify the theoretical axial optical resolution, delineate and enhance the axial fabrication resolution of 3D structures, including square prism and cylinder micropillars, is also reported. The micropillar array presents a simple “write‐and‐seed” and table platform for cell niche studies. Fibroblasts attach to, grow on, and express adhesion to molecules on micropillar arrays without the need of matrix coating. They exhibit a more “3D” morphology comparing with that in 2D monolayer cultures and physiological functions such as matrix deposition. This work presents an important milestone in engineering complex protein microstructures and micropatterns with sub‐micrometer topological features to mimic the native matrix niche for cell‐matrix interaction studies.     

Assessment of Novel Long‐Lasting Ceria‐Stabilized Zirconia‐Based Ceramics with Different Surface Topographies as Implant Materials

The development of long‐lasting zirconia‐based ceramics for implants, which are not prone to hydrothermal aging, is not satisfactorily solved. Therefore, this study is conceived as an overall evaluation screening of novel ceria‐stabilized zirconia–alumina–aluminate composite ceramics (ZA₈Sr₈‐Ce11) with different surface topographies for use in clinical applications. Ceria‐stabilized zirconia is chosen as the matrix for the composite material, due to its lower susceptibility to aging than yttria‐stabilized zirconia (3Y‐TZP). This assessment is carried out on three preclinical investigation levels, indicating an overall biocompatibility of ceria‐stabilized zirconia‐based ceramics, both in vitro and in vivo. Long‐term attachment and mineralized extracellular matrix (ECM) deposition of primary osteoblasts are the most distinct on porous ZA₈Sr₈‐Ce11_p surfaces, while ECM attachment on 3Y‐TZP and ZA₈Sr₈‐Ce11 with compact surface texture is poor. In this regard, the animal study confirms the porous ZA₈Sr₈‐Ce11_p to be the most favorable material, showing the highest bone‐to‐implant contact values and implant stability post implantation in comparison with control groups. Moreover, the microbiological evaluation reveals no favoritism of biofilm formation on the porous ZA₈Sr₈‐Ce11_p when compared to a smooth control surface. Hence, together with the in vitro in vivo assessment analogy, the promising clinical potential of this novel ZA₈Sr₈‐Ce11 as an implant material is demonstrated.     

Organosilica Materials with Bridging Phenyl Derivatives Incorporated into the Surfaces of Mesoporous Solids

An interesting class of materials is mesoporous organosilica materials containing a bridging, organic group along the pore‐surface. Such materials are prepared from silsesquioxane precursors of the type (R′O)₃Si‐R‐Si(OR′)₃ where R is the bridging organic group of interest, in combination with a lyotropic phase as a template for the generation of the pores. A new silsesquioxane precursor, 1,3‐bis‐(trialkoxysilyl)‐5‐bromobenzene, and the related mesoporous organosilica material containing bromobenzene groups located at the pore walls are presented in the current publication. The latter precursor allows access to the derivatization reactions known for halogenated aromatic compounds. Materials containing phenyl derivatives can be obtained either by chemical modifications starting from the mentioned precursor on the molecular scale, or the modifications can be performed directly at the surfaces of the porous material. Materials with surfaces containing benzoic acid, styrene, and phenylphosphonic acid are described.     

PMN-PZN-PZT四元系压电陶瓷材料的研究

采用传统的氧化物混合烧结工艺制备了Pb(Mn1/3Nb2/3)x(Zn1/3Nb2/3)y(ZrzTi1z)1xyO3四元系压电陶瓷材料。研究了成分及预烧温度对该四元系材料组织结构与性能的影响规律。研究结果表明:随着Pb(Mn1/3Nb2/3)O3含量的增多,陶瓷的相结构由四方相转变为三方相,准同型相界位于0.025 PMN～0.075 PMN之间,且Pb(Mn1/3Nb2/3)O3增加至7.5 %(摩尔分数),可以同时提高机电耦合系数kp和机械品质因数Qm,使kp达到0.575,Qm达到1 621;提高预烧温度可以改善陶瓷的烧结特性,同时可以改善陶瓷的介电、压电性能。     

BaO含量对一种微电子封装材料性能的影响

采用传统固相反应法,制备了一种微电子封装材料,并对其进行了电、力、热性能测试,及XRD、SEM分析表征,具体研究了BaO含量对该材料性能的影响。结果表明:BaO对主晶相石英没有太大的影响,促进钡长石的形成,抑制方石英相的析出,其含量增加能在一定程度上改善材料的介电性能,但会逐渐破坏玻璃网络,影响到材料的力学和热学性能,导致抗弯强度降低,热膨胀系数减小。     

Multiresponsive PEDOT–Ionic Liquid Materials for the Design of Surfaces with Switchable Wettability

Among the different types of stimuli‐responsive polymers, conjugated polymers reveal unique multiresponsive behavior. In this work, the synthesis and characterization of new functional poly(3,4‐ethylenedioxythiophenes) (PEDOT) bearing imidazolium ionic‐liquid moieties (PEDOT‐Im) is reported. PEDOT‐Im polymers show multiresponsive properties to a variety of stimuli, such as temperature, pH, oxidative doping, and presence of anions. These stimuli provoke different changes in PEDOT‐Im, such as changes in color, oxidation state, and, wetting behavior. In all cases, a reversible effect is observed, and the polymers reveal responsive properties in solution as well as in the form of thin films. Whereas sensitiveness to pH and oxidative doping are known phenomena for other PEDOT derivatives, responsiveness to temperature and to anions is a unique property of PEDOT‐Im. The anion exchange is further investigated by means of the Quartz Crystal Microbalance with dissipation. Anion exchanges induce fast, adjustable, and reversible contact angle changes between 24° and 107°. As a potential application, surfaces with switchable wettability triggered by anion solutions are prepared by spin‐coating PEDOT‐Im films onto different substrates.