Outstanding Mechanical Robustness Research Articles

Self-encapsulating Ag nanospheres in amorphous carbon: a novel ultrathin selective absorber for flexible solar-thermal conversion

Ag nanospheres encapsulated in amorphous carbon (ANEAC) multilayer solar selective absorbers (SSAs) with a whole thickness of only 130 nm, which possess impressive flexible solar-thermal conversion and outstanding mechanical robustness.

Robust substrate anchorages of silk lines with extensible nano-fibres.

Living systems are built of multiscale-composites: materials formed of components with different properties that are assembled in complex micro- and nano-structures. Such biological multiscale-composites often show outstanding physical properties that are unachieved by artificial materials. A major scientific goal is thus to understand the assembly processes and the relationship between structure and function in order to reproduce them in a new generation of biomimetic high-performance materials. Here, we tested how the assembly of spider silk nano-fibres (i.e. glue coated 0.5 μm thick fibres produced by so-called piriform glands) into different micro-structures correlates with mechanical performance by empirically and numerically exploring the mechanical behaviour of line anchors in an orb weaver, a hunting spider and two ancient web builders. We demonstrate that the anchors of orb weavers exhibit outstanding mechanical robustness with minimal material use by the indirect attachment of the silk line to the substrate through a soft domain ('bridge'). This principle can be used to design new artificial high-performance attachment systems.

Mechanically robust, intrinsically self-healing crosslinked polymer enabled by dynamic urea bond exchange reaction

Designing a crosslinked polymer with self-healing, recyclable, and mechanical properties is a significant challenge in the field of self-healing chemistry. Herein, robust, intrinsically self-healing, crosslinked polyureas (C-PUs) are prepared via a facile one-pot photo-induced copolymerization to address the aforementioned limitation. The key strategy involves the introduction of a synthetic monomer with reversible urea bonds into the polymer network as a versatile dynamic crosslinker. The resultant C-PUs are a class of resource-saving materials with a combination of excellent intrinsic self-healing capability with outstanding mechanical robustness. Notably, the properties of the materials can be easily tuned by simply adjusting the dynamic crosslinker content. In addition, an environmentally friendly polymer reprocessing is achieved and the potential of the materials in the smart anticorrosion application is investigated. These desirable properties are attributed to the underlying topological network rearrangement enabled by the dynamic urea bond exchange reaction, which is confirmed by stress relaxation tests. Therefore, the resulting self-healing C-PUs can serve as models to extend the scope of applications in smart protective materials or ocean engineering.

Three-Dimensional Structured Dual-Mode Flexible Sensors for Highly Sensitive Tactile Perception and Noncontact Sensing.

This work reports a three-dimensional (3D) structured multifunctional sensor by connecting a magnetowhisker with a superflexible patterned skin film. Composed of percolation networks of silver nanowires, the patterned skin film is integrated via a simple template manufacturing method without increasing the complexity and sacrificing the flexibility. The as-prepared 3D structured sensor can realize the multimodal detection of out-of-plane tactile stimuli and details of noncontact environmental obstacles in multiple directions. Here, the sensor's perception behaviors on compression, pulling, magnetic field, sound waves, airflow, water level, water flow, and backwash are presented. Furthermore, the 3D structured sensor obtains outstanding mechanical robustness and stability for 8000 cycles, excellent sensitivity (12 800% when the applied pulling displacement was 3.5 mm; 152% T-1 when the magnetic flux density variation was 40.6 mT), ultrahigh response time, and ultrahigh recovery time (∼5 ms), which may meet the industrial sensing requirement for artificial tactile electronics. Facile manufacturing processes and outstanding multimodal sensing characteristics make the 3D structured sensor to possess great potential to be implemented in the next-generation intelligent bionic equipment or systems.

Flexible Organic Solar Cells Over 15% Efficiency with Polyimide-Integrated Graphene Electrodes

Summary The performance of organic solar cells (OSCs) has been steadily increasing, surpassing 16% power conversion efficiency (PCE) with advances in photoactive and charge transport materials. Nonetheless, the performance of flexible OSCs still falls behind that of their rigid counterparts. Furthermore, commonly used plastic substrates are vulnerable to high-temperature annealing processes. Herein, a highly flexible and durable electrode with thermal stability achieved through direct integration of polyimide (PI) on graphene is introduced. The PI-assisted graphene electrode exhibits an ultra-clean surface together with an optical transmittance exceeding 92%, a sheet resistance of 83 Ω/sq, and thermal stability. Moreover, direct integration of PI improved the durability of the graphene electrode by inhibiting delamination of the graphene under mechanical stress. Using the PI-assisted graphene electrode, flexible OSC with a PCE of 15.2% was obtained with outstanding mechanical robustness. The proposed electrode is promising for use in various optoelectronic devices requiring high efficiency and flexibility.

Directly grown Sr–Co layered double hydroxide (LDH) entangled two dimensional nanosheet film with superior performances

Designing of electrode with electrochemically rich structure, outstanding mechanical robustness and high electrical conductivity remains a challenge. We report a design of entangled Sr–Co Layered double hydroxides (LDHs) two-dimensional structure for such electrode. The hierarchical electrode with entangled nanosheet exhibit high specific capacitance of 1415 F g-1 at 5 A g-1 current density, excellent rate capability, high energy (12.28Whkg−1) and power density (567.788 W kg-1) and outstanding stability (80% capacity retention over 5000 cycles). The asymmetric device cell of Sr–Co LDH/ACC gives high energy density (27.78 Whkg-1) and power density (499.96Wkg-1) with cyclic performance of 1000 cycles with 95.24% capacitance retention. Further, we provide a detailed analysis of the various electrolyte environment experienced by the electrode and their effect on electrochemical properties. We pick out three different electrolytes; LiOH, NaOH, KOH and show that both selected electrolyte and metal combination for LDHs paves the way for outstanding electrochemical performance.

Fabrication of multifunctional closed-surface SiO2-TiO2 antireflective thin films

Multifunctional thin films with superhydrophilicity, broadband antireflective performance, humidity resistance and outstanding mechanical robustness are essential as for their wide applications. However, so far, it remains a big challenge to take into consideration all these properties simultaneously due to the structural contradiction. Herein, we develop an effective dip-coating process to prepare hybrid thin films with mechanical robustness, high transmittance, super-durable moisture resistance, excellent photocatalytic activity and durable superhydrophilicity. Three different nanoparticles were deposited sequentially to construct the above thin film and the maximum transmittance of this particular thin film reached ∼96.0%. The film surface showed an excellent superhydrophilicity (water contact angle ≈3.0°), and antifogging property. The superhydrophilic thin film could keep its property for more than 20 days. The transformation from hydrophilicity to superhydrophilicity of the thin film could be readily realized by UV irradiation. Moreover, its self-cleaning property could be retained after reduplicative storage and UV illumination cycles. Sponge washing test, water drop impact, pencil hardness test and tape peeling test revealed that the thin film possessed outstanding mechanical robustness. Methylene blue photodegradation was chose to weigh the photocatalytic activity of the hybrid thin film. In addition, the thin film shows excellent humidity-resistance at high temperature, and the excellent performance is due to its closed-surface structure. The closed-surface multifunctional thin films pave way toward use in solar cells, high-rise architecture windows under severe climate conditions.

Wirelessly destructible MgO-PVP-Graphene composite based flexible transient memristor for security applications

Transient electronics fabricated using low cost, abundant, biodegradable materials is one of the promising solutions to address the issue of e-waste. This work is the first demonstration of an ultra-fast wirelessly destructible non-volatile memory using a novel MgO-PVP-Gr composite material synthesized by a low cost solution processed method. Optimized synthesis conditions result in the composite based memristor device which exhibits bipolar resistive switching with excellent device performances viz., on/off ratio of 8.5 × 103, switching endurance of 500 cycles, data retention of >104 s at lower set and reset voltages of +4 V, -4 V. The mechanism for conduction bridging based resistive switching (RS) is discussed in terms of the formation and rupture of the electrochemically active silver metal clusters. Furthermore, the composite is used to fabricate crossbar memory architecture that finds wide applications in non-volatile memories. Modelling and bending studies on the memristor reveal outstanding mechanical robustness along with stability, primarily attributed to high young's modulus of graphene. Due to the high hydro-dissolution rates of MgO and PVP, the device dissolves completely in water (within 3 s). Finally, wirelessly controlled memory deletion using the mobile application is demonstrated which offers better control for the end user to handle memory devices useful in security applications.

Design and preparation of a multi-fluorination organic superhydrophobic coating with high mechanical robustness and icing delay ability

Biomimetic superhydrophobic coatings have attracted significant attention from academia and industry. However, superhydrophobic surfaces become vulnerable and lose water-repellency due to their poor mechanical stability in complex environments. Herein, a novel fluorinated resin matrix and perfluoro mercaptopropionate hydrophobic agent were designed and fabricated based on thiol-ene click reaction, which were used to prepare a multi-fluorination organic superhydrophobic coating by mixing polytetrafluoroethylene (PTFE) particles and triethylenetetramine. In addition to the high superhydrophobicity and self-cleaning performance, the coatings exhibited outstanding mechanical robustness under sandpaper abrasion for 100 cycles, which could be attributed to the high adhesion of the fluorinated resin matrix. The organic superhydrophobic coating maintained excellent superhydrophobicity after exposure to acid corrosion, knife-scratching, and finger-wiping damage. Moreover, the coatings exhibited good icing delay ability outdoors at −10 °C. This paper presents a novel preparation method and application for superhydrophobic coatings.

Versatile N‐Doped MXene Ink for Printed Electrochemical Energy Storage Application

AbstractPrinting is regarded as a revolutionary and feasible technique to guide the fabrication of versatile functional systems with designed architectures. 2D MXenes are nowadays attractive in printed energy storage devices. However, owing to the van der Waals interaction between the MXene layers, the restacking issues within the printed electrodes can significantly impede the ion/electrolyte transport and hence handicap the electrochemical performances. Herein, a melamine formaldehyde templating method is demonstrated to develop crumpled nitrogen‐doped MXene (MXene‐N) nanosheets. The nitrogen doping boosts the electrochemical performances of MXene via enhanced conductivity and redox activity. Accordingly, two types of MXene‐N inks are prepared throughout the optimization of the ink viscosity to fit the 2D screen printing and 3D extrusion printing, respectively. As a result, the screen printed MXene‐N microsupercapacitor delivers an areal capacitance of 70.1 mF cm−2 and outstanding mechanical robustness. Furthermore, the 3D‐printed MXene‐N based supercapacitor manifests an areal capacitance of 8.2 F cm−2 for a three‐layered electrode and readily stores a high areal energy density of 0.42 mWh cm−2. The approach to harnessing such versatile MXene‐N inks offers distinctive insights into the printed energy storage systems with high areal energy density and large scalability.

Nanoscale Parallel Circuitry Based on Interpenetrating Conductive Assembly for Flexible and High‐Power Zinc Ion Battery

AbstractHigh‐rate capability has become an important feature for energy storage devices, but it is often accompanied with a significant reduction in energy density. Therefore, developing an energy storage technology that combines high‐rate capability with high energy density is a great challenge for next‐generation electronic devices. Here, parallel circuitry is constructed at the nanoscale to lower the resistance for ion and electron transport that largely determines the rate performance. The parallel circuitry is constructed through intertwining continuous carbon nanotubes with an interpenetrating conductive assembly based on hierarchically layered MXene (Ti3C2Tx ) functionalized by KMnO4 (MnOx @Ti3C2Tx ). The assembly shows ultrafast rate capability, e.g., maintaining 50% capacity when the current density increases from 0.1 to 10 A g−1. Investigations of the kinetics and charge storage mechanisms confirm the efficiency of the designed parallel circuitry in improving rate capability by providing rapid pathways for ions and electrons, as well as dividing the current flow evenly into individual MnOx @Ti3C2Tx flakes in the assembly. The flexible MnOx @Ti3C2Tx based electrode endows zinc ion batteries with outstanding mechanical robustness and good power delivering performance. The paradigm presented here paves a new way for designing electrodes with high‐rate capability toward next‐generation energy storage technologies.

Robustly Superhydrophobic Conductive Textile for Efficient Electromagnetic Interference Shielding.

Superhydrophobic electromagnetic interference (EMI) shielding textile (EMIST) is of great significance to the safety and long-term service of all-weather outdoor equipment. However, it is still challenging to achieve long-term durability and stability under external mechanical deformations or other harsh service conditions. Herein, by designing and implementing silver nanowire (AgNW) networks and a superhydrophobic coating onto a commercial textile, we demonstrate a highly robust superhydrophobic EMIST. The resultant EMIST shows a synergy of high water contact angle (160.8°), low sliding angle (2.9°), and superior EMI shielding effectiveness (51.5 dB). Remarkably, the EMIST still maintains its superhydrophobic feature and high EMI shielding level (42.6 dB) even after 5000 stretching-releasing cycles. Moreover, the EMIST exhibits strong resistance to ultrasonic treatment up to 60 min, peeling test up to 100 cycles, strong acidic/alkaline solutions, and different organic solvents, indicating its outstanding mechanical robustness and chemical durability. These attractive features of the EMIST are mainly a result of the joint action of AgNWs, carbon nanotubes, polytetrafluoroethylene nanoparticles, and fluoroacrylic polymer. This work offers a promising approach for the design of future durable, superhydrophobic EMISTs, which are capable of remaining fully functional against long-time exposure to extreme conditions, for example, wet and corrosive environments.

Bending Durable and Recyclable Mesostructured Perovskite Solar Cells Based on Superaligned ZnO Nanorod Electrode

Though high‐quality perovskite films can be achieved under low‐temperature, the efficient charge selective materials, such as the most widely used TiO2, require high‐temperature sintering process, hindering mass production with roll‐to‐roll process by using flexible substrate. Here, a low‐temperature (90 °C) process is developed for preparing superaligned ZnO nanorods (SAZNRs), serving as mesostructured scaffold in direct contact with the perovskite layer. By rational design of the length of the SAZNRs, the perovskite solar cell (PSC), reaches a highest power conversion efficiency of ≈13.8% with largely suppressed hysteresis behavior. More importantly, this nano‐array design demonstrates outstanding mechanical robustness after being incorporated onto the flexible substrate, resulting in a performance preservation of 90% after 1000 bending cycles with a curvature radius of 4 mm. Finite element analysis indicate that the reduction of device performance after bending is ascribed to the cracks occurred in AZO stress concentration layer, which is attested by experiment as well. Besides, the SAZNRs ETM can be reused for fabricating new perovskite solar cells with comparable photovoltaic performance in a time‐saving and scalable manner, paving the way for industrial production of PSCs.

Bioinspired leaves-on-branchlet hybrid carbon nanostructure for supercapacitors

Designing electrodes in a highly ordered structure simultaneously with appropriate orientation, outstanding mechanical robustness, and high electrical conductivity to achieve excellent electrochemical performance remains a daunting challenge. Inspired by the phenomenon in nature that leaves significantly increase exposed tree surface area to absorb carbon dioxide (like ions) from the environments (like electrolyte) for photosynthesis, we report a design of micro-conduits in a bioinspired leaves-on-branchlet structure consisting of carbon nanotube arrays serving as branchlets and graphene petals as leaves for such electrodes. The hierarchical all-carbon micro-conduit electrodes with hollow channels exhibit high areal capacitance of 2.35 F cm−2 (~500 F g−1 based on active material mass), high rate capability and outstanding cyclic stability (capacitance retention of ~95% over 10,000 cycles). Furthermore, Nernst–Planck–Poisson calculations elucidate the underlying mechanism of charge transfer and storage governed by sharp graphene petal edges, and thus provides insights into their outstanding electrochemical performance.

Mechanically robust and electrically conductive graphene-paper/glass-fibers/epoxy composites for stimuli-responsive sensors and Joule heating deicers

In this article, by composing three functional constituents into a multilayered structure with well-bonded interfaces, a conductive graphene-papers (GPs)/glass-fibers (GFs) reinforced epoxy composite (GPs-GE) with outstanding mechanical robustness, high electrical conductivity and sensitive stimuli-responsive performance is highlighted. Thereinto, GPs serves as a stimuli-responsive and Joule heating chip due to its superiorities on both of mechanical and electrical properties, while GFs possessing mechanically protective and strengthening functionality. The stimuli-responsive characterizations by electrical resistance change reveal the synchronous sensing properties of GPs-GE to different stimuli inputs such as mechanical deformation, temperature fluctuation and humidity. Subsequently, Joule heating and de-icing/anti-icing properties of GPs-GE are investigated symmetrically, indicating its large heating rate, high efficiency of energy conversion and low cost. Such superior performance of GPs-GE confirms that the design of multilayer microstructure to achieve multi-functionalization paves a novel way to scale-up fabrication of advanced graphene composites, indicating promising applications as mechanically reinforcing elements, stimuli-responsive sensors and electrical Joule heating chips in intelligent engineering monitoring and icing-induced disaster prevention at low-temperature environment.

Flyweight 3D Graphene Scaffolds with Microinterface Barrier-Derived Tunable Thermal Insulation and Flame Retardancy.

In this article, flyweight three-dimensional (3D) graphene scaffolds (GSs) have been demonstrated with a microinterface barrier-derived thermal insulation and flame retardancy characteristics. Such 3D GSs were fabricated by a modified hydrothermal method and a unidirectional freeze-casting process with hierarchical porous microstructures. Because of high porosity (99.9%), significant phonon scattering, and strong π-π interaction at the interface barriers of multilayer graphene cellular walls, the GSs demonstrate a sequence of multifunctional properties simultaneously, such as lightweight density, thermal insulating characteristics, and outstanding mechanical robustness. At 100 °C, oxidized GSs exhibit a thermal conductivity of 0.0126 ± 0.0010 W/(m K) in vacuum. The thermal conductivity of oxidized GSs remains relatively unaffected despite large-scale deformation-induced densification of the microstructures, as compared to the behavior of reduced GSs (rGSs) whose thermal conductivity increases dramatically under compression. The contrasting behavior of oxidized GSs and rGSs appears to derive from large differences in the intersheet contact resistance and varying intrinsic thermal conductivity between reduced and oxidized graphene sheets. The oxidized GSs also exhibit excellent flame retardant behavior and mechanical robustness, with only 2% strength decay after flame treatment. In a broader context, this work demonstrates a useful strategy to design porous nanomaterials with a tunable heat conduction behavior through interface engineering at the nanoscale.

Interlayer growth of borates for highly adhesive graphene coatings with enhanced abrasion resistance, fire-retardant and antibacterial ability

Surface coatings to protect materials from mechanical abrasion, fire and microbial colonization are associated with billion dollars of expenses across broad range of industrial, domestic and defence applications. Currently used protective coatings based on heavy metals, halogenated fire-retardation, and biocide agents have considerable environmental concerns due their toxicity, and lack of effectiveness with limited functionality. In this paper, we present engineering of new multifunctional coating based on graphene composites with the ability to provide “3-in-1” protective properties. These multiple functionalities were created with specially designed graphene composite by growing sodium metaborate (NaBO2·xH2O) crystals into graphene oxide (GO) layer during their reduction, which works synergistically as a surface binder, a flame-retardant additive, and an antibacterial agent. The testing of protective coating performances revealed an outstanding mechanical robustness (ASTM-class 4B), and the reduction of bacterial colonization up to ∼99.92%. The high flame retardant performance of the coated wood, and paper showed non-flammability, strong intumescent effect, and self-extinguishing ability during fire. These protective coatings based on graphene composites due the simplicity of their formulations, scalability, and outstanding performance offer a great potential for their industrial, structural, and environmental applications.

Hierarchical Ni–Co Hydroxide Petals on Mechanically Robust Graphene Petal Foam for High‐Energy Asymmetric Supercapacitors

A hierarchical structure consisting of Ni–Co hydroxide nanopetals (NCHPs) grown on a thin free‐standing graphene petal foam (GPF) has been designed and fabricated by a two‐step process for pseudocapacitive electrode applications. The mechanical behavior of GPFs has been, for the first time to our knowledge, quantitatively measured from in situ scanning electron microscope characterization of the petal foams during in‐plane compression and bending processes. The Young's modulus of a typical GPF is 3.42 GPa, indicating its outstanding mechanical robustness as a nanotemplate. The GPF/NCHP electrodes exhibit volumetric capacitances as high as 765 F cm−3, equivalent to an areal capacitance of 15.3 F cm−2 and high rate capability. To assess practical functionality, two‐terminal asymmetric solid‐state supercapacitors with 3D GPF/NCHPs as positive electrodes are fabricated and shown to exhibit outstanding energy and power densities, with maximum average energy density of ≈10 mWh cm−3 and maximum power density of ≈3 W cm−3, high rate capability (a capacitance retention of ≈60% at 100 mA cm−2), and excellent long‐term cyclic stability (full capacitance retention over 15 000 cycles).

Cystine oligomers successfully attached to peptide cysteine-rich fibrils

Amyloid peptides are renowned to be related to neurodegenerative diseases, however, a fruitful avenue is to employ them as high-performance nanomaterials. These materials benefit from the intrinsic outstanding mechanical robustness of the amyloid backbone made of β-strands. In this work, we exploited amyloid-like fibrils as functional material to attach pristine L-cysteine aggregates (cystine oligomers) and gold nanoparticles, without the need of templating compounds. This work will open new avenues on functional materials design and their realisation.

A novel micro glow plug fabricated from polymer-derived ceramics: in situ measurement of high-temperature properties and application to ultrahigh-temperature ignition

Abstract This work describes the design, fabrication, modeling, characterization and testing of a new class of MEMS: micro igniters for ultrahigh-temperature (exceeding 1000 °C) ignition applications. Micro glow plugs (MGPs) were fabricated from polymer-derived silicon carbon–nitride (SiCN), which is a recently-developed and highly refractory ceramic derived from a liquid polymer precursor. SiCN has been shown to possess outstanding mechanical robustness, corrosion resistance, and thermal shock resistance at ultrahigh-temperatures, making it an ideal material for harsh environment applications. The micro glow plug achieved temperatures of up to 1450 °C, with a response time of