Excellent Mechanical Robustness Research Articles

Reducing the reprocessing and healing temperature of polyurea with piperazine-based hindered urea bonds

With a novel hindered urea bond, excellent mechanical robustness and recycling ability are well balanced in piperazine-based polyureas.

Mechanically robust multifunctional antifogging coating on transparent plastic substrates

A facile preparation method to form a transparent self-cleaning antifogging coating on polycarbonate substrates is reported. The coating uses a thin double layered SiO2/TiO2 structure, which has an additional advantage of reduced visible light reflection. A two-step protocol is developed for enhanced mechanical durability, which comprises a room temperature oxygen plasma treatment of the polycarbonate substrate, followed by deposition of the SiO2/TiO2 films using pulse laser deposition. The oxygen plasma treatment changes the polymer surface chemistry to allow strong adhesion with the antifogging coatings. The SiO2/TiO2 coating exhibits superhydrophilicity even without the previously claimed necessary ultraviolet irradiation. The self-cleaning capability is demonstrated via photocatalytic degradation of methylene blue and oleic acid. Excellent adhesion and mechanical robustness of the coating is exhibited by crosshatch and abrasion tests. The multifunctional coating on polymer substrates provides an avenue for practical applications for optical lenses and displays.

Low-Temperature Deposited Highly Flexible In–Zn–V–O Transparent Conductive Electrode for Perovskite Solar Cells

Inorganic–organic hybrid perovskite solar cells (PSCs) typically embrace Sn-doped In2O3 (ITO) and F-doped SnO2 (FTO) as transparent electrodes, which are rigid and brittle, retarding the commercialization of flexible PSCs (FPSCs). Here, we fabricated flexible amorphous transparent V-doped In–Zn–O (IZVO) thin films with varied concentrations of V atoms at room temperature. The impacts of V concentration on the chemical, electrical, and optical properties of IZVO thin films were thoroughly investigated. The incorporation of V into IZO was demonstrated to suppress the formation of oxygen vacancies and thus reduce the carrier concentration in IZO. The IZVO thin film affords the best electrode performance with an optimum V concentration of 0.46 atom %. In contrast to the conventional ITO transparent electrodes that require a high processing temperature, the amorphous transparent IZVO electrode deposited at a low temperature without any heating and postannealing process showed a low sheet resistance (∼22.6 Ω/□), high conductivity (∼2210 S/cm), high optical transmittance (∼88.8%), and in particular, excellent mechanical flexibility and fatigue robustness. Therefore, the amorphous transparent IZVO electrode-based perovskite solar cells (PSCs) showed superior performance (14.57%) compared to the amorphous ITO electrode-based PSCs (11.96%), due to the significantly improved short-circuit current density (JSC), open-circuit voltage (VOC), and fill factor (FF). Moreover, the IZVO electrode-based FPSC device retained 77% of its initial power conversion efficiency (PCE) after 100 bending cycles, while the PCE of the amorphous ITO electrode-based FPSC dropped by 80% after only 30 bending cycles. Combining the excellent mechanical flexibility and fatigue robustness, the flexible amorphous IZVO electrode shows great potential for highly efficient flexible photovoltaic applications.

Nanocomposite block copolymer membranes with enhanced permeance and robustness by carbon nanotube doping

Block copolymers (BCPs) have received extensive attention in the preparation of advanced membranes for precise separations. However, BCP-derived membranes usually suffer from insufficient mechanical robustness, especially for the most extensively studied polystyrene-based ones. Herein, carbon nanotubes (CNTs) are incorporated into polystyrene-block-poly (2-vinyl pyridine) (S2VP) membranes to enhance the mechanical robustness and water permeance. It is found that mild oxidation is enough to enable the homogeneous dispersion of CNTs in the S2VP solution. The CNT/S2VP mixture is directly coated on macroporous substrates, followed by selective swelling-induced pore generation to produce the CNT-doped S2VP nanocomposite membranes. The as-prepared membranes are featured with two sets of pores: swelling-induced pores and incompatibility-induced nanoscale gaps between CNTs and the S2VP matrix, leading to improved permeances without any decrease of the retention performances. Also, owing to the presence of CNTs in the polymer matrix, the membranes show excellent mechanical robustness and exhibit better pressure resistance than neat S2VP membrane without CNT doping. This work demonstrates a simple yet efficient strategy to prepare BCP-based nanocomposite membranes with enhanced permeance and robustness at no expense of retention.

Improving the bending resistance of double-layer printed flexible OLEDs with PEDOT: PSS-PEO composite HIL films

Flexible organic light-emitting diodes (OLEDs) are expected to have excellent device performance and mechanical robustness in many areas, such as wearable electronics and display devices. For the traditional materials of OLED anode, indium tin oxide (ITO) is undoubtedly the most mature transparent conductive electrode available. However, the brittle and rigid nature of ITO severely limit the development of flexible OLED (FOLED). In this work, a solution blending film consisting of poly (3,4 ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) and poly (ethylene oxide) (PEO) was used as a hybrid hole injection layer, where PEO polymer in the composite films can greatly improve the bending resistance of device. The printed FOLEDs doped with PEO exhibit impressive mechanical durability, maintaining 80.4% of its maximum external quantum efficiency after 1000 bends at a radius of curvature of 10 mm, compared to 46.3% for the counterpart without PEO doping.

Rational Design of Li-Wicking Hosts for Ultrafast Fabrication of Flexible and Stable Lithium Metal Anodes.

The ever-increasing development of flexible and wearable electronics has imposed unprecedented demand on flexible batteries of high energy density and excellent mechanical stability. Rechargeable lithium (Li) metal battery shows great advantages in terms of its high theoretical energy density. However, the use of Li metal anode for flexible batteries faces huge challenges in terms of its undesirable dendrite growth, poor mechanical flexibility, and slow fabrication speed. Here, a highly scalable Li-wicking strategy is reported that allows ultrafast fabrication of mechanically flexible and electrochemically stable Li metal anodes. Through the rational design of the interface and structure of the wicking host, the mean speed of Li-wicking reaches 10 m2 min-1 , which is 1000 to 100000 fold faster than the reported electrochemical deposition or thermal infusion methods and meets the industrial fabrication speed. Importantly, the Li-wicking process results in a unique 3D Li metal structure, which not only offers remarkable flexibility but also suppresses the dendrite formation. Paring the Li metal anode with lithium-iron phosphate or sulfur cathode yields flexible full cells that possess a high charging rate (8.0mA cm-2 ), high energy density (300-380Wh kg-1 ), long cycling stability (over 550 cycles), and excellent mechanical robustness (500 bending cycles).

Printable and stable all-polymer solar cells based on non-conjugated polymer acceptors with excellent mechanical robustness

Printable and stable all-polymer solar cells based on non-conjugated polymer acceptors with excellent mechanical robustness

Mechanically and environmentally stable triboelectric nanogenerator based on high-strength and anti-compression self-healing ionogel

Using supramolecular chemistry to develop ionogels that can restore their mechanical performance and functionality is of great interest for flexible electronic applications. In particular, self-healing ionogels with high strength and compression resistance are highly attractive for the fabrication of self-healing triboelectric nanogenerators (TENGs) as the power supply for next-generation electronics. Herein, ZnO nanoparticle-reinforced poly(acrylic acid)-based self-healing ionogels are synthesized with high mechanical strength, compression resistance, transparency, good ionic conductivity, and a wide operating temperature range. By sandwiching the self-healing ionogel between 3 M tape, a self-healing ionogel-based TENG (SI-TENG) with a high output power density of 3.15 W m−2 is obtained. Due to the excellent mechanical robustness and environmental stability of the self-healing ionogel, the SI-TENG exhibits a reliable electrical output performance in the range of − 30–80 °C after being folded, twisted, stretched, and trampled. Thus, the SI-TENG can be used to harvest energy from human motions such as tapping, walking, and running. After mechanical damage, the SI-TENG can be healed at room temperature to completely restore its electrical output performance, ensuring its longevity and reliability.

High Tg Norbornene-Based Aems with Excellent Hydroxide Conductivity and Mechanical Robustness

Anion exchange membranes (AEMs) are a key component in many electrochemical energy devices such as fuel cells, electrolyzers, and flow batteries. Though much progress has been made in the development of AEMs, the chemical and mechanical stability of the membrane remains an issue for long-term operation. Studies have demonstrated that the absence of heteroatom linkages such as ether, sulfide, and sulfone in the backbone improve the long term alkaline and mechanical stability of AEMs. Here we report our study on the development of highly robust and chemically stable polyolefin membranes and ionomers. The norbornene-based membranes and ionomers were successfully synthesized by vinyl-addition polymerization of norbornene derivatives. They exhibit a high glass temperature (Tg>200°C) that provides mechanical stability at elevated temperatures. The length of the pendant quaternary ammonium group greatly influences ease of quaternarization, conductivity, and water uptake. Thin stable membranes can be fabricated at 20-30 µm, to assure low ASR values. The membranes exhibit excellent hydroxide conductivity (>120 mS/cm at 80°C, in water) and stability towards hydroxide ions. The fuel cell performance of the AEMs will also be discussed.

Flexible Conductive Polyimide Fiber/MXene Composite Film for Electromagnetic Interference Shielding and Joule Heating with Excellent Harsh Environment Tolerance.

The development of flexible MXene-based multifunctional composites is becoming a hot research area to achieve the application of conductive MXene in wearable electric instruments. Herein, a flexible conductive polyimide fiber (PIF)/MXene composite film with densely stacked "rebar-brick-cement" lamellar structure is fabricated using the simple vacuum filtration plus thermal imidization technique. A water-soluble polyimide precursor, poly(amic acid), is applied to act as a binder and dispersant to ensure the homogeneous dispersion of MXene and its good interfacial adhesion with PIF after thermal imidization, resulting in excellent mechanical robustness and high conductivity (3787.9 S/m). Owing to the reflection on the surface, absorption through conduction loss and interfacial/dipolar polarization loss inside the material, and the lamellar structure that is beneficial for multiple reflection and scattering between adjacent layers, the resultant PIF/MXene composite film exhibits a high electromagnetic interference (EMI) shielding effectiveness of 49.9 dB in the frequency range of 8.2-12.4 GHz. More importantly, its EMI shielding capacity can be well maintained in various harsh environments (e.g., extreme high/low temperature, acid/salt solution, and long-term cyclic bending), showing excellent stability and durability. Furthermore, it also presents fast, stable, and long-term durable Joule heating performances based on its stable and excellent conductivity, demonstrating good thermal deicing effects under actual conditions. Therefore, we believe that the flexible conductive PIF/MXene composite film with excellent conductivity and harsh environment tolerance possesses promising potential for electromagnetic wave protection and personal thermal management.

Design of mechanical robust superhydrophobic Cu coatings with excellent corrosion resistance and self-cleaning performance inspired by lotus leaf

Various strategies have been developed to fabricate mechanical robust superhydrophobic membranes on the original substrates. However, for superhydrophobic coatings that have to be homologous to the inherently fragile substrate, their mechanical stability problems have not been satisfactorily solved. Herein, we prepared three hierarchical superhydrophobic Cu coating via facile pulse electrodeposition with microstructure size of 10–15, 30–40, and 60–70 µm, respectively. The resulting superhydrophobic coatings simultaneously exhibit excellent self-cleaning, mechanical robustness, and corrosion resistance. A hydrophobic mechanism suitable for worn superhydrophobic surfaces was proposed, which can well analyze the influence of microstructure changes on wettability. Moreover, these three coatings can withstand 15, 50, and 100 cycles of sandpaper abrasion, respectively, as the size of the microstructure increases. The results demonstrate a size effect of microstructure, which means surfaces with larger-sized microstructures can better maintain their superhydrophobicity under mechanical damage. Our findings offer a reference for improving the mechanical robustness of other superhydrophobic coatings that are homologous to the substrate.

A novel intrinsic semi-aromatic polyamide dielectric toward excellent thermal stability, mechanical robustness and dielectric performance

The development of aliphatic polyamide as dielectric polymer is limited due to relatively high dielectric loss, low breakdown strength and low servicing temperature. Different from the traditional ways for enhancing the dielectric properties of aliphatic polyamides by compositing with inorganic materials, here an alternative strategy is reported via random copolymerizing aliphatic polyamide with semi aromatic polyamides as functional segments. The designed co-polyamide shows decreased dielectric loss of 0.04 and enhanced breakdown strength of 319 MV/m with a low content of semi aromatic polyamides. Moreover, taking advantage of the inherent rigid benzene ring and flexible aliphatic chain, high glass transition temperature and great toughness are achieved simultaneously in the prepared semi aromatic polyamides. The introduction of aromatic segments has also improved dielectric and mechanical properties of co-polyamide at elevated temperature (150 °C), which is desirable and crucial for polymer dielectrics. The strategy provides new possibilities for the development of high-performance intrinsic polymer dielectrics.

Roll-to-roll 3D printing of flexible and transparent all-solid-state supercapacitors

Roll-to-roll (R2R) fabrication of flexible and transparent all-solid-state supercapacitors (FT-ASSCs) is extremely challenging because of the classic trade-off between transparency and capacitance. In this work, we develop fully three-dimensional (3D)-printed, sandwich-type FT-ASSCs comprised of 3D line-patterned carbon black (CB)/Ag/CB electrodes on a transparent dialysis membrane (DM) separator. By tailoring the line pitch of the 3D electrodes, our FT-ASSC is able to achieve more than 80% optical transmittance and significantly higher areal capacitance than an opaque ASSC. More importantly, the performance of 3D-printed FT-ASSCs is unrestricted by the transparency-capacitance trade-off, and they exhibit a superior capacitive figure of merit value compared with state-of-the-art FT-ASSCs reported in the literature. Additionally, our FT-ASSCs demonstrate excellent cyclic stability and mechanical robustness because of the chemical and mechanical stability of the DM separator and effective encapsulation of polyurethane. The single-flow 3D printing technique introduced here can meet the requirements for industrial-scale R2R manufacturing of energy storage devices.

Superhydrophilic-underwater superoleophobic NiO nanostructured surfaces: Assessment of PVP concentration effect

In this research, superhydrophilic-underwater superoleophobic NiO and nickel oxalate micro/nano structured thin films on the stainless steel (SS) meshes have been fabricated via chemical bath deposition (CBD) as a facile route. Taguchi L16 experimental design was used for optimization the effects of six important influential parameters affecting the surface wettability including molar ratio of alkaline to metallic precursor salt, alkaline agent type, NiO seed layer solution concentration, seed layer type, Polyvinylpyrrolidone (PVP) concentration and precursor type. Effect of the PVP concentration (as additive) on the oil contact angle was evaluated for the first time. The molar ratio of the alkaline to metallic salt and PVP concentration were the two most important factors having the highest impact on the underwater oil repellency behavior. The sample prepared under the optimum conditions exhibited underwater superoleophobicity with the oil contact angle (OCA) of 156.15 ± 7.5° and oil contact angle hysteresis (OCAH) of 4.3°. The X-ray diffraction (XRD) analysis, Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FE-SEM), and roughness measurements were applied for characterization of the fabricated samples. Based on the FESEM analysis, the spherical nano- ZnO seeds have diameters of ~30–50 nm. In addition, the abrasion test was accomplished (12 cycles under 4.7kPa). The obtained results showed an excellent mechanical robustness. Moreover, an acceptable chemical durability (after 240 h) in acidic and alkaline environments with pH values of 4, 6 and 12 was observed.

Large-area fabrication of colorful superhydrophobic coatings with high solar reflectivity

In the present work, the colorful superhydrophobic coating with high solar reflectivity was prepared using WPC (White Portland cement), color pigments, Polymethylhydrosiloxane and water as raw materials. The superhydrophobicity of the coating surface comes from the combination of the micron/sub-micron rough structure formed by the accumulation of cement hydration products and pigment particles and the low surface energy provided by PMHS (Polymethylhydrosiloxane). The superhydrophobic coating exhibits excellent resistance to corrosion of aggressive solutions, pollution of liquid foods, and accumulation of dust. The SR (Solar reflectance) of superhydrophobic coatings was optimized by changing the type, content and collocation of pigments. The results show that the superhydrophobic coating filled WP (with white pigment) and YP (yellow pigment) has the best performance. The optimized coating is yellowish brown with IR reflectance of 0.8191 and SR of 0.6569, which meets the building energy saving standard. The results of solar radiation experiments show that the surface temperature of the yellow–brown superhydrophobic coating is reduced by 5.7 °C compared with the ordinary Portland cement coating, which has a significant cooling effect. The colorful superhydrophobic coatings also possessed excellent weatherability and high mechanical robustness. Therefore, the coating developed in this work can be used on the exterior wall and roof of the building to reduce the energy consumption of the building in summer.

Covalently bonded silica interfacial layer for simultaneously improving thermal and dielectric performance of copper/epoxy composite

Copper/epoxy (Cu/epoxy) composite is a kind of important thermal management material due to its high thermal conductivity, excellent mechanical robustness and low cost. However, susceptibility of Cu to oxygen and high electric leakage loss of Cu urgently require a protective interfacial layer with anti-oxidation and electric insulation properties. Currently, the reported interfacial layers for Cu fillers either are prepared under harsh condition or possess inferior insulation/thermal resistant properties. Here, we propose a strategy to prepare dense silica interfacial layer containing Si-NH-Si/Si-H reactive groups for Cu/epoxy composite, which not only protects Cu from oxidation but also tethers Cu and epoxy with covalent bonds. Compared with Cu/epoxy composite, the as-prepared Cu@silica/epoxy composite exhibits enhanced thermal conductivity, high temperature stability without decrease of thermal conductivity at 150 °C for 200 h, and improved dielectric performance with dielectric permittivity and loss of 13.1 and 0.1 at 100 Hz, respectively. This work provides an efficient approach to covalently bond interfacial layer for simultaneously improving thermal and dielectric property of Cu/epoxy composite, showing high potential for real application.

Mechanical Robust Flexible Single-Component Organic Solar Cells.

Owing to the advantages of being lightweight and compatible with surfaces with different deformations, flexible organic solar cells (OSCs) have broad scopes of applications, including wearable electronics and portable devices. Most flexible OSCs focus on the two-component bulk-heterojunction (BHJ) photo-active layers, but they usually suffer from degradation problems both in efficiency and mechanical durability derived from the limited phase stability under mechanical and thermal stress. Whereas, single-component organic solar cells (SCOSCs) based on the double-cable conjugated polymer are supposed to possess excellent mechanical robustness and long-term stability. Here, the first flexible SCOSCs based on a double-cable polymer are fabricated on a transparent silver nanowires (AgNWs) electrode on a plastic foil. Impressively, the obtained flexible SCOSCs exhibited a power conversion efficiency (PCE) of 7.21%. The flexible SCOSCs are further demonstrated to possess superior mechanical robustness (>95% retention after 1000 bending cycles) and storage stability (>97% retention after 430 h in nitrogen atmosphere) compared to several BHJ-type flexible OSCs. The pseudo-free-standing tensile test and morphology investigation are conducted to reveal the distinction in mechanical durability of the single-component polymer film and the BHJ-type films. Besides, ultraflexible SCOSCs are also fabricated, indicating the application prospect and superiority in flexible devices and wearable electronic products.

Water-Sintered Transient Nanocomposites Used as Electrical Interconnects for Dissolvable Consumer Electronics.

Rapid development of electronic technology shortens the development time for new products and accelerates the obsolescence of consumer electronics, resulting in the explosive growth of electronic waste that is difficult to recycle and hazardous to the environment and human health. Transient electronics that can dissolve in water may potentially be adopted to tackle the issues of electronic waste; however, promising approaches to yield large-scale and high-performance transient consumer electronics have not yet been developed. Here, the joint effect of galvanic corrosion and redeposition has been utilized to develop bimetallic transient nanocomposites, which can be printed and water-sintered to yield high-performance transient PCB circuits with excellent electrical conductivity and mechanical robustness. The entire sintering process requires no external energy and strict environmental conditions. The achieved PCB circuits offer a conductivity of 307,664.4 S/m that is among the highest in comparison with other printed transient circuits. The supreme performance of the transient circuits eventually leads to the first dissolvable smartwatch that offers the same functions and similar performance as conventional smartwatches and dissolves in water within 40 h. The joint effect of galvanic corrosion and redeposition between two metals with distinct activities leads to novel nanocomposites and processing techniques of transient electronics. The resulting high-performance transient devices may reshape the appearance of consumer electronics and reform the electronics recycling industry by reducing recycling costs and minimizing environmental pollution and health hazard.

One‐step fabrication of wear‐resistant superhydrophobic coating based on aminosilane‐functionalized diatomaceous earth

AbstractFacile fabrication of superhydrophobic coatings with excellent mechanical robustness is highly desired in practical application. Herein, a convenient and effective strategy for one‐step fabrication of robust volumetric superhydrophobic coating was developed containing aminosilane‐functionalized cylindrical diatomaceous earth (DE) particles and a polyurethane (PU) resin. Due to the strong chemical cross‐linking between the amino groups and the isocyanates, the superhydrophobic DE particles were strongly anchored to the PU resin, thus improving the wear resistance of the coating. The coating could withstand 20 m sandpaper abrasion under a constant pressure of 2.6 kPa. The wear resistance of the coating improved nearly 471% compared with the superhydrophobic DE/PU composite coating prepared by physical‐blending. Moreover, the coating also demonstrated great self‐cleaning performance, excellent chemical stability and underwater durability. Additionally, the as‐prepared coating could be easily applied to various substrates and exhibited high rigidity (3H‐4H), good adhesion (4B‐5B), and great flexibility (impact resistance of 1 Kg·m).

Grafting of epoxidized natural rubber chains with BN platelets to obtain flexible and thermally conductive papers

Owing to the rapid development of high-power and minimized electronic devices, the materials with ultra-flexibility and effective heat dissipation have attracted much interest. Herein, the high thermally conductive epoxidized natural rubber (ENR) papers with layered structures based on boron nitride (BN) platelets are reported. First, polyrhodanine (PRd) was coated on the surface of BN platelets via oxidative polymerization of rhodanine (Rhd), which was initiated by the absorbed (S2O8)2- ions. Then, BN-PRd platelets were grafted with ENR chains using a mechanochemical method due to the presence of N–CS groups in PRd, allowing the combination of PRd and ENR chains with stable covalent bonds. Moreover, the grafted ENR chains acted as bridges between adjacent BN platelets and improved the heat transfer ability of BN-PRd/ENR thermally conductive composite papers. The as-prepared ultra-flexible 30 wt% BN-PRd/ENR thermally conductive composite papers rendered high in-plane (λ∥) and through-plane (λ⊥) thermal conductivity of 14.57 and 0.52 W/(mK), respectively, which were correspondingly 8094% and 289% of pure ENR paper (0.18 W/(mK)). Also, Young's modulus of the 30 wt% BN-PRd/ENR thermally conductive composite paper was 25.90 MPa. Overall, the as-fabricated BN-PRd/ENR thermally conductive composite papers demonstrated high flexibility, excellent mechanical robustness, outstanding thermal conductivity, and superior electronic illustration, indicating potential applications in areas of electronic components as thermal interface materials.