Double-Layer Nacre-Inspired Polyimide-Mica Nanocomposite Films with Excellent Mechanical Stability for LEO Environmental Conditions

Silane modified Cr2O3/polyimide nanocomposite films with excellent surface insulation performance for space applications

The exploration of deep space significantly increases the probability of spacecraft failures due to surface electrostatic discharge, which imposes higher vacuum insulation protection requirements on polyimide (PI), the external insulation material of spacecrafts. To address this challenge, this study proposes using silane coupling agent KH550 for organic grafting treatment of Cr2O3nanoparticles, which are then used to dope and modify PI to enhance the vacuum surface insulation of PI films. The KH550 grafting improves the interface strength between the fillers and the matrix, allowing the fillers to be uniformly dispersed in the matrix. Compared to pure PI films, the prepared PI-Cr2O3@KH550 composite films exhibit significantly enhanced vacuum surface flashover voltage, improved surface/volume resistivity, and dielectric properties. The results demonstrate that PI composite films with 0.8% by mass of Cr2O3@KH550 show the most notable performance improvement, with the DC flashover voltage and impulse flashover voltage in vacuum increasing by 20.7% and 27.8%, respectively. The doping of chromium oxide nanoparticles introduces more deep traps into the PI films and reduce the surface resistivity. The higher deep trap density inhibits charge migration, thereby alleviating secondary electron emission and surface electric field distortion. Simultaneously, the lower surface resistivity facilitates dissipating surface charges and improves the surface insulation. These findings are of significant reference value for promoting the enhancement of aerospace insulation performance.

Polyimide as a biomedical material: advantages and applications

Polyimides (PIs) are a class of polymers characterized by strong covalent bonds, which offer the advantages of high thermal weight, low weight, good electronic properties and superior mechanical properties. They have been successfully used in the fields of microelectronics, aerospace engineering, nanomaterials, lasers, energy storage and painting. Their biomedical applications have attracted extensive attention, and they have been explored for use as an implantable, detectable, and antibacterial material in recent years. This article summarizes the progress of PI in terms of three aspects: synthesis, properties, and application. First, the synthetic strategies of PI are summarized. Next, the properties of PI as a biological or medical material are analyzed. Finally, the applications of PI in electrodes, biosensors, drug delivery systems, bone tissue replacements, face masks or respirators, and antibacterial materials are discussed. This review provides a comprehensive understanding of the latest progress in PI, thereby providing a basis for developing new potentially promising materials for medical applications.

A Bioinspired Design of Protective Al2O3/Polyurethane Hierarchical Composite Film Through Layer-By-Layer Deposition

Structural materials such as ceramics, metals, and carbon fiber-reinforced plastics (CFRP) are frequently threatened by large compressive and impact forces. Energy absorption layers, i.e., polyurethane and silicone foams with excellent damping properties, are applied on the surfaces of different substrates to absorb energy. However, the amount of energy dissipation and penetration resistance are limited in commercial polyurethane foams. Herein, a distinctive nacre-like architecture design strategy is proposed by integrating hard porous ceramic frameworks and flexible polyurethane buffers to improve energy absorption and impact resistance. Experimental investigations reveal the bioinspired designs exhibit optimized hardness, strength, and modulus compared to that of polyurethane. Due to the multiscale energy dissipation mechanisms, the resulting normalized absorbed energy (≈8.557 MJ m-3) is ≈20 times higher than polyurethane foams under 50% quasi-static compression. The bioinspired composites provide superior protection for structural materials (CFRP, glass, and steel), surpassing polyurethane films under impact loadings. It is shown CFRP coated with the designed materials can withstand more than ten impact loadings (in energy of 10 J) without obvious damage, which otherwise delaminates after a single impact. This biomimetic design strategy holds the potential to offer valuable insights for the development of lightweight, energy-absorbent, and impact-resistant materials.

Guidelines derived from biomineralized tissues for design and construction of high-performance biomimetic materials: from weak to strong

Living organisms in nature have undergone continuous evolution over billions of years, resulting in the formation of high-performance fracture-resistant biomineralized tissues such as bones and teeth to fulfill mechanical and biological functions, despite the fact that most inorganic biominerals that constitute biomineralized tissues are weak and brittle. During the long-period evolution process, nature has evolved a number of highly effective and smart strategies to design chemical compositions and structures of biomineralized tissues to enable superior properties and to adapt to surrounding environments. Most biomineralized tissues have hierarchically ordered structures consisting of very small building blocks on the nanometer scale (nanoparticles, nanofibers or nanoflakes) to reduce the inherent weaknesses and brittleness of corresponding inorganic biominerals, to prevent crack initiation and propagation, and to allow high defect tolerance. The bioinspired principles derived from biomineralized tissues are indispensable for designing and constructing high-performance biomimetic materials. In recent years, a large number of high-performance biomimetic materials have been prepared based on these bioinspired principles with a large volume of literature covering this topic. Therefore, a timely and comprehensive review on this hot topic is highly important and contributes to the future development of this rapidly evolving research field. This review article aims to be comprehensive, authoritative, and critical with wide general interest to the science community, summarizing recent advances in revealing the formation processes, composition, and structures of biomineralized tissues, providing in-depth insights into guidelines derived from biomineralized tissues for the design and construction of high-performance biomimetic materials, and discussing recent progress, current research trends, key problems, future main research directions and challenges, and future perspectives in this exciting and rapidly evolving research field.

Bottom-Up Film-to-Bulk Assembly Toward Bioinspired Bulk Structural Nanocomposites

Biological materials, although composed of meager minerals and biopolymers, often exhibit amazing mechanical properties far beyond their components due to hierarchically ordered structures. Understanding their structure-properties relationships and replicating them into artificial materials would boost the development of bulk structural nanocomposites. Layered microstructure widely exists in biological materials, serving as the fundamental structure in nanosheet-based nacres and nanofiber-based Bouligand tissues, and implying superior mechanical properties. High-efficient and scalable fabrication of bioinspired bulk structural nanocomposites with precise layered microstructure is therefore important yet remains difficult. Here, one straightforward bottom-up film-to-bulk assembly strategy is focused for fabricating bioinspired layered bulk structural nanocomposites. The bottom-up assembly strategy inherently offers a methodology for precise construction of bioinspired layered microstructure in bulk form, availability for fabrication of bioinspired bulk structural nanocomposites with large sizes and complex shapes, possibility for design of multiscale interfaces, feasibility for manipulation of diverse heterogeneities. Not limited to discussing what has been achieved by using the current bottom-up film-to-bulk assembly strategy, it is also envisioned how to promote such an assembly strategy to better benefit the development of bioinspired bulk structural nanocomposites. Compared to other assembly strategies, the highlighted strategy provides great opportunities for creating bioinspired bulk structural nanocomposites on demand.

Effects of various types of organo-mica on the physical properties of polyimide nanocomposites

Poly(amic acid) (PAA) was synthesized using dianhydride 4,4'-oxydiphthalic anhydride and diamine 3,3'-dihydroxybenzidine, and polyimide (PI) hybrid films were synthesized by dispersing organo-mica in PAA through a solution intercalation method. Hexadimethrine-mica (HM-Mica), 1,2-dimethylhexadecylimidazolium-mica (MI-Mica), and didodecyldiphenylammonium-mica (DP-Mica), which were obtained via the organic modification of pristine mica, were used as the organo-micas for the PI hybrid films. The organo-mica content was varied from 0.5 to 3.0 wt% with respect to the PI matrix. The thermomechanical properties, morphology, and optical transparency of the resultant PI hybrid films were measured and compared. Dispersion of even small amounts of organo-mica effectively improved the physical properties of the PI hybrids, and maximum enhancements in physical properties were observed at a specific critical content. Electron microscopy of the hybrid films revealed that the organo-mica uniformly dispersed throughout the polymer matrix at the nanoscale level when added at low contents but aggregated in the matrix when added at levels above the critical content. Structural changes in the organo-mica closely influenced the changes in the physical properties of the hybrid films. All PI hybrid films with various organo-mica contents showed similar optical properties, but that prepared with MI-Mica demonstrated the best thermomechanical properties. All synthesized PI hybrid films were transparent regardless of the type and content of organo-mica used.

A synergistic interfacial and topological strategy for reinforcing aramid nanofiber films

While nanomaterials possess impressive mechanical properties at the microscale level, their macroscopic assemblies usually exhibit inferior properties due to ineffective stress transfer among individual nanomaterials. This issue is addressed in this work by achieving strong interfacial interactions between aramid nanofibers and graphene oxide nanosheets through a neutralization reaction in a dipolar solvent and regulating the topological properties using polymer micelles to form a compact structure, leading to the formation of a super-strong and super-tough nanofiber film. The film was prepared through a sol-gel-film transition process and possesses a nacre-like microstructure that deflects microcracks and prevents them from propagating straight through the film. Remarkably, it demonstrates a tensile strength of 599.0 MPa and a toughness of 37.7 MJ m-3, which are 491.0% and 1094.5% that of a pristine aramid nanofiber film, respectively. In addition, it exhibits excellent tolerance to extreme temperatures (-196 to 300 °C) and fatigue resistance to folding 10 000 times. Overall, this study presents a synergistic interfacial and topological enhancement strategy for constructing nanomaterial-based composites with inherited properties from the nanoscale building blocks to the macroscale structural material.

Scalable Production of 2D Minerals by Polymer Intercalation and Adhesion for Multifunctional Applications

Natural and sustainable 2D minerals have many unique properties and may reduce reliance on petroleum-based products. However, the large-scale production of 2D minerals remains challenging. Herein, a green, scalable, and universal polymer intercalation and adhesion exfoliation (PIAE) method to produce 2D minerals such as vermiculite, mica, nontronite, and montmorillonite with large lateral sizes and high efficiency, is developed. The exfoliation relies on the dual functions of polymers involving intercalation and adhesion to expand interlayer space and weaken interlayer interactions of minerals, facilitating their exfoliation. Taking vermiculite as an example, the PIAE produces 2D vermiculite with an average lateral size of 1.83 ± 0.48 µm and thickness of 2.40 ± 0.77 nm at a yield of ≈30.8%, surpassing state-of-the-art methods in preparing 2D minerals. Flexible films are directly fabricated by the 2D vermiculite/polymer dispersion, exhibiting outstanding performances including mechanical strength, thermal resistance, ultraviolet shielding, and recyclability. The representative application of colorful multifunctional window coatings in sustainable buildings is demonstrated, indicating the potential of massively produced 2D minerals.

Tailoring Organic/Inorganic Interface Trap States of Metal Oxide/Polyimide toward Improved Vacuum Surface Insulation

High-voltage and high-power devices are indispensable in spacecraft for outer space explorations, whose operations require aerospace materials with adequate vacuum surface insulation performance. Despite persistent attempts to fabricate such materials, current efforts are restricted to trial-and-error methods and a universal design guideline is missing. The present work proposes to improve the vacuum surface insulation by tailoring the surface trap state density and energy level of the metal oxides with varied bandgaps, using coating on a polyimide (PI) substrate, aiming for a more systematical workflow for the insulation material design. First-principle calculations and trap diagnostics are employed to evaluate the material properties and reveal the interplay between trap states and the flashover threshold, supported by dedicated analyses of the flashover voltage, secondary electron emission (SEE) from insulators, and surface charging behaviors. Experimental results suggest that the coated PI (i.e., CuO@PI, SrO@PI, MgO@PI, and Al2O3@PI) can effectively increase the trap density and alter the trap energy levels. Elevated trap density is demonstrated to always yield lower SEE. In addition, increasing shallow trap density accelerates surface charge dissipation, which is favorable for improving surface insulation. CuO@PI exhibits the most remarkable increase in shallow trap density, and accordingly, the highest flashover voltage is 42.5% higher than that of pristine PI. This study reveals the critical role played by surface trap states in flashover mitigation and offers a novel strategy to optimize the surface insulation of materials.

Low-Temperature Assembling Strategy of a Nacre-Inspired Lamellar Configuration to Upcycling Biaxially Oriented Polypropylene Film Waste

The efficient recycling and utilization of plastic waste have become a hot topic of global concern, but conventional mechanical recycling not only deteriorates the performance of recycled plastic but also loses the intrinsic structure and properties of the original product. Herein, an upcycling strategy of a biaxially oriented polypropylene (BOPP) film was proposed by duplicating the lamellar configuration established in nature nacre. Especially the suspension of PP wax was deposited on the surface of the BOPP film by spray-coating, followed by layer-by-layer assembling and hot-pressing at 160 °C above the melting temperature of PP wax but below the initial melting temperature of the BOPP film. In this case, PP wax not only functioned as a binder to enable strong interfacial adhesion between the BOPP films via interfacial diffusion but also acted as a soft phase to insert between the rigid BOPP films, constructing a soft-hard alternatively aligned configuration similar to brick-and-mortar architecture in nature nacre. As a result, the mechanical properties of the lamellar sample markedly outperformed those of the conventional mechanically recycling sample, evidenced by 113 and 1141% increases in tensile strength and impact strength, respectively. This simple and effective method provides a new strategy for efficient upcycling of oriented packaging films, which is important to realize the sustainable recycling of plastic waste.

Fluorinated Polyimide/Allomelanin Nanocomposites for UV-Shielding Applications

A series of highly fluorinated polyimide/allomelanin nanoparticles (FPI/AMNPs) films were prepared with FPI as the matrix and AMNPs as the filler. Due to the formation of hydrogen bonds, significantly reinforced mechanical and UV-shielding properties are acquired. Stress-strain curves demonstrated a maximum tensile strength of 150.59 MPa and a fracture elongation of 1.40% (0.7 wt.% AMNPs), respectively, 1.78 and 1.56× that of pure FPI. The measurements of the UV-vis spectrum, photodegradation of curcumin and repeated running tests confirmed the splendid UV-shielding capabilities of FPI/AMNPs films. The enhancement mechanisms, such as synergistic UV absorption of the charge transfer complexes in FPI and AMNPs and photothermal conversion, were the reasons for its exceptional UV shielding. The excellent comprehensive properties above enable FPI/AMNPs nanocomposites to be potential candidates in the field of UV shielding.

Nacre-Inspired Bacterial Cellulose/Mica Nanopaper with Excellent Mechanical and Electrical Insulating Properties by Biosynthesis

The exploration of extreme environments has become necessary for understanding and changing nature. However, the development of functional materials suitable for extreme conditions is still insufficient. Herein, a kind of nacre-inspired bacterial cellulose (BC)/synthetic mica (S-Mica) nanopaper with excellent mechanical and electrical insulating properties that has excellent tolerance to extreme conditions is reported. Benefited from the nacre-inspired structure and the 3D network of BC, the nanopaper exhibits excellent mechanical properties, including high tensile strength (375 MPa), outstanding foldability, and bending fatigue resistance. In addition, S-Mica arranged in layers endows the nanopaper with remarkable dielectric strength (145.7 kV mm^-1 ) and ultralong corona resistance life. Moreover, the nanopaper is highly resistant to alternating high and low temperatures, UV light, and atomic oxygen, making it an ideal candidate for extreme environment-resistant materials.

Ready-to-use interactive dual-readout differential lateral flow biosensor for two genotypes of human papillomavirus

Ready-to-use in vitro diagnosis of multiple genotypes is vital for the prevention and treatment of cervical cancer. Herein, a paper-film-based interactive dual readout differential lateral flow biosensor is proposed to simultaneously assay two high-risk types of human papillomavirus (HPV) within the body-fluid. The CuCo₂S₄/ZnIn₂S₄ heterostructure is fabricated on the paper-film compound chip with high thermostability, and surface sulfur vacancy is introduced by mild annealing treatment to endow unexceptionable photoexcitation activity, such structure can be served as an initial energy harvester and converter. With the assistance of differential channels, the dual-target-propelled self-assembly of annular DNA and the cleavage activity of CRISPR-Cas12a are stepwise activated by sequential solution transfer. Accordingly, the input and release of polydopamine-coated gold nanoparticles with photothermal/photoelectric characteristic were implemented. The fabricated biosensor not only realized intelligent thermal-response without large instruments, but also actuated dynamic interfacial charge separation and transfer kinetics to further transmit photoelectric-signal, resulting in desirable interactive dual-signal with low limit-of-detection (0.21 pM for HPV-18 and 42.92 pM for HPV-16). Thanks to the sophisticated design of differential lateral flow paper-film compound chip and interactive dual-signal amplification strategy, sensitive detection of two HPV genotypes is realized, which provides a promising candidate for home medical intelligent diagnosis.

Enhancing the Toughness of Free-Standing Polyimide Films for Advanced Electronics Applications: A Study on the Impact of Film-Forming Processes

High-quality and free-standing polyimide (PI) film with desirable mechanical properties and uniformity is in high demand due to its widespread applications in highly precise flexible and chip-integrated sensors. In this study, a free-standing PI film with high toughness was successfully prepared using a diamine monomer with ether linkages. The prepared PI films exhibited significantly superior mechanical properties compared to PI films of the same molecular structure, which can be attributed to the systematic exploration of the film-forming process. The exploration of the film-forming process includes the curing procedures, film-forming substrates, and annealing treatments. Additionally, the thickness uniformity and surface homogeneity of free-standing films were crucial for toughness. Increasing the crystallinity of the PI films by eliminating residual stress also contributed to their high strength. The results demonstrate that by adjusting the above-mentioned factors, the prepared PI films possess excellent mechanical properties, with tensile strength and elongation at break of 194.71 MPa and 130.13%, respectively.

Molecular Orientation-Regulated Bioinspired Multilayer Composites with Largely Enhanced Mechanical Properties

Natural nacre's hierarchical brick-and-mortar architecture motivates intensive studies on inorganic platelet/polymer multilayer composites, targeting mechanical property enhancement only by two strategies: optimizing the size and alignment of inorganic platelets and improving the interfacial interaction between inorganic platelets and polymers. Herein, a new strategy of polymer chain orientation to enhance the property of bioinspired multilayered composites is presented, which facilitates more stress to be transferred from polymer layers to inorganic platelets by simultaneous stiffening of multiple polymer chains. To this end, bioinspired multilayer films consisting of oriented sodium carboxymethyl cellulose chains and alumina platelets are designed and fabricated by three successive steps of water evaporation-induced gelation in glycerol, high-ratio prestretching, and Cu²⁺ infiltration. Regulating the orientation state of sodium carboxymethyl cellulose leads to a large enhancement of mechanical properties, including Young's modulus (2.3 times), tensile strength (3.2 times), and toughness (2.5 times). It is observed experimentally and predicted theoretically that the increased chain orientation induces failure mode transition in the multilayered films from alumina platelet pull-out to alumina platelet fracture because more stress is transferred to the platelets. This strategy opens an avenue toward rational design and manipulation of polymer aggregation states in inorganic platelet/polymer multilayer composites and allows a highly effective increase in modulus, strength, and toughness.

Dual-Phase Inspired Soft Electronic Sensors with Programmable and Tunable Mechanical Properties

Wearable and stretchable sensors are important components to strictly monitor the behavior and health of humans and attract extensive attention. However, traditional sensors are designed with pure horseshoes or chiral metamaterials, which restrict the biological tissue engineer applications due to their narrow regulation ranges of the elastic modulus and the poorly adjustable Poisson's ratio. Inspired by the biological spiral microstructure, a dual-phase metamaterial (chiral-horseshoes) is designed and fabricated in this work, which possesses wide and programmable mechanical properties by tailoring the geometrical parameters. Experimental, numerical, and theoretical studies are conducted, which reveal that the designed microstructures can reproduce mechanical properties of most natural animals such as frogs, snakes, and rabbits skin. Furthermore, a flexible strain sensor with the gauge factor reaching 2 under 35% strain is fabricated, which indicates that the dual-phase metamaterials have a stable monitoring ability and can be potentially applied in the electronic skin. Finally, the flexible strain sensor is attached on the human skin, and it can successfully monitor the physiological behavior signals under various actions. In addition, the dual-phase metamaterial could combine with artificial intelligence algorithms to fabricate a flexible stretchable display. The dual-phase metamaterial with negative Poisson's ratio could decrease the lateral shrinkage and image distortion during the stretching process. This study offers a strategy for designing the flexible strain sensors with programmable, tunable mechanical properties, and the fabricated soft and high-precision wearable strain sensor can accurately monitor the skin signals under different human motions and potentially be applied for flexible display.

Anticorrosion Coating with Heterogeneous Assembly of Nanofillers Modulated by a Magnetic Field

An anticorrosive coating with randomly distributed passive barriers and regionally enriched active corrosion inhibitors is developed by integrating mica nanosheets (MNSs) and magnetic-responsive core-shell mesoporous nanoparticles with 2-mercaptobenzothiazole (Fe₃O₄@mSiO₂/MBT) under magnetic field incubation. The bottom enriched Fe₃O₄@mSiO₂/MBT rapidly releases the MBT to form a passivation layer on corrosion sites, enhancing the corrosion inhibition efficiency by 30.36% compared with the control (NP_0.7EP-R). The impedance modulus |Z|_0.01 Hz of the sample (NP_0.7/MNS_0.5/EP) increases by five orders of magnitude compared with that of its control (NP_0.7/MNS₀EP) after 30 days of corrosion immersion. NP_0.7/MNS_0.5/EP exhibited the lowest corrosion rate (3.984 × 10^-5 mm/year) as compared to the other samples. Notably, the coating in a fractured state still maintains superior corrosion inhibition even after 40 day salt spray testing. The differentiated distribution of nanofillers was well confirmed by optical microscopy and SEM-EDS, and the synergistic effect of the active/passive integrated anticorrosive coating with merits of both comprehensive protection and fast responsiveness was systematically explored.

Multifunctional Thermally Conductive Composite Films Based on Fungal Tree-like Heterostructured Silver Nanowires@Boron Nitride Nanosheets and Aramid Nanofibers

Thermal conduction for electronic equipment has grown in importance in light of the burgeoning of 5G communication. It is imperatively desired to design highly thermally conductive fillers and polymer composite films with prominent Joule heating characteristics and extensive mechanical properties. In this work, "solvothermal & in situ growth" method is carried out to prepare "Fungal tree"-like hetero-structured silver nanowires@boron nitride nanosheet (AgNWs@BNNS) thermally conductive fillers. The thermally conductive AgNWs@BNNS/ANF composite films are obtained by the method of "suction filtration self-assembly and hot-pressing". When the mass fraction of AgNWs@BNNS is 50 wt%, AgNWs@BNNS/ANF composite film presents the optimal thermal conductivity coefficient of 9.44 W/(m ⋅ K) and excellent tensile strength of 136.6 MPa, good temperature-voltage response characteristics, superior electrical stability and reliability, which promise a wide application potential in 5G electronic devices.

A Bioinspired Ultratough Composite Produced by Integration of Inorganic Ionic Oligomers within Polymer Networks

The nacre-inspired laminates are promising materials for their excellent mechanics. However, the interfacial defects between organic-inorganic phases commonly lead to the crack propagation and fracture failure of these materials under stress. A natural biomineral, bone, has much higher bending toughness than the nacre. The small size of inorganic building units in bone improves the organic-inorganic interaction, which optimizes the material toughness. Inspired by these biological structures, here, an ultratough nanocomposite laminate is prepared by the integration of ultrasmall calcium phosphate oligomers (CPO, 1 nm in diameter) within poly(vinyl alcohol) (PVA) and sodium alginate (Alg) networks through a simple three-step strategy. Owing to the small size of inorganic building units, strong multiple molecular interactions within integrated organic-inorganic hierarchical structure are built. The resulting laminates exhibit ultrahigh bending strain (>50% without fracture) and toughness (21.5-31.0 MJ m^-3), which surpass natural nacre and almost all of the synthetic laminate materials that have been reported so far. Moreover, the mechanics of this laminate is tunable by changing the water content within the bulk structure. This work provides a way for the development of organic-inorganic nanocomposites with ultrahigh bending toughness by using inorganic ionic oligomers, which can be useful in the fields of tough protective materials and energy absorbing materials.

A Constrained Assembly Strategy for High-Strength Natural Nanoclay Film

Developing high-performance materials from existing natural materials is highly desired because of their environmental friendliness and low cost; two-dimensional nanoclay exfoliated from layered silicate minerals is a good building block to construct multilayered macroscopic assemblies for achieving high mechanical and functional properties. Nevertheless, the efforts have been frustrated by insufficient inter-nanosheet stress transfer and nanosheet misalignment caused by capillary force during solution-based spontaneous assembly, degrading the mechanical strength of clay-based materials. Herein, a constrained assembly strategy that is implemented by in-plane stretching a robust water-containing nanoclay network with hydrogen and ionic bonding is developed to adjust the 2D topography of nanosheets within multilayered nanoclay film. In-plane stretching overcomes capillary force during water removal and thus restrains nanosheet conformation transition from nearly flat to wrinkled, leading to a highly aligned multilayered nanostructure with synergistic hydrogen and ionic bonding. It is proved that inter-nanosheet hydrogen and ionic bonding and nanosheet conformation extension generate profound mechanical reinforcement. The tensile strength and modulus of natural nanoclay film reach up to 429.0 MPa and 43.8 GPa and surpass the counterparts fabricated by normal spontaneous assembly. Additionally, improved heat insulation function and good nonflammability are shown for the natural nanoclay film and extend its potential for realistic uses.

Progress in Aromatic Polyimide Films for Electronic Applications

Aromatic polyimides have excellent thermal stability, mechanical strength and toughness, high electric insulating properties, low dielectric constants and dissipation factors, and high radiation and wear resistance, among other properties, and can be processed into a variety of materials, including films, fibers, carbon fiber composites, engineering plastics, foams, porous membranes, coatings, etc. Aromatic polyimide materials have found widespread use in a variety of high-tech domains, including electric insulating, microelectronics and optoelectronics, aerospace and aviation industries, and so on, due to their superior combination characteristics and variable processability. In recent years, there have been many publications on aromatic polyimide materials, including several books available to readers. In this review, the representative progress in aromatic polyimide films for electronic applications, especially in our laboratory, will be described.

Silk-based bioinspired structural and functional materials

Natural biological materials provide a rich source of inspiration for building high-performance materials with extensive applications. By mimicking their chemical compositions and hierarchical architectures, the past decades have witnessed the rapid development of bioinspired materials. As a very promising biosourced raw material, silk is drawing increasing attention due to excellent mechanical properties, favorable versatility, and good biocompatibility. In this review, we provide an overview of the recent progress in silk-based bioinspired structural and functional materials. We first give a brief introduction of silk, covering its sources, features, extraction, and forms. We then summarize the preparation and application of silk-based materials mimicking four typical biological materials including bone, nacre, skin, and polar bear hair. Finally, we discuss the current challenges and future prospects of this field.

Pistachio-Inspired Bulk Graphene Oxide-Based Materials with Shapeability and Recyclability

Nowadays, despite the fact that recent progress has been reported to mimic natural structural materials (especially nacre), designing bioinspired ultrastrong composites in a universal, viable, and scalable manner still remains a long-standing challenge. In particular, pistachio shells show high tissue strength attributed to the cellulose sheet laminated microstructures. Compared with nacre, pistachio shells own interlocking mortise-tenon joints in their structure, which offer higher energy dissipation and deformability. Here we present a strategy to produce nanocomposites with pistachio-mimetic structures through repeated kneading of graphene oxide (GO) in a dynamic covalent and supramolecular poly(sodium thioctic) (pST) system. The dynamic nature of the polymeric backbones endows the resultant GO-based composite with full recyclability and three-dimensional shapeability. The superior mechanical properties of the pistachio-mimetic composite can be attributed to the mortise-tenon joints design in the structure, which has not been achieved in the nacre-mimetic composite. The resulting composite also exhibits high thermal conductivity (15.6 W/(m·K)), yielding an alternative approach to design in engineered and thermal management materials.