Good Mechanical Robustness Research Articles

A non-fluorinated, in-situ self-healing electrothermal/superhydrophobic coating on Mg alloy for anti-icing and anti-corrosion

The superhydrophobic surface has become a smart strategy for boosting the application of Mg alloy due to its anti-icing and anti-corrosion abilities. However, its application has been limited due to some drawbacks, such as harmful fluorinated materials, poor mechanochemical robustness, and unsatisfactory anti-icing performance in extreme environments. Herein, a non-fluorinated electrothermal/superhydrophobic coating, including bottom insulation and top superhydrophobic films, is prepared on Mg alloy by spray method. The superhydrophobic coating exhibits good mechanical robustness, chemical stability, and in-situ electrothermal-healing ability against plasma and chemical etchings. The electrothermal characteristic and superhydrophobicity endow the coating with excellent static and dynamic anti-icing, de-frosting, and de-icing performances. Moreover, the superhydrophobic coating exhibits a long-term anti-corrosion effect due to a durable air layer and organic coating, and can recover the coating's corrosion resistance by repairing superhydrophobicity. We expect that this research provides a wise strategy for designing superhydrophobic coating with good mechanical robustness, good chemical stability, electrothermal, in-situ self-healing, outstanding anti-icing, and long-term corrosion protection abilities to meet functional needs of Mg alloy as well as other metal materials.

Highly sensitive piezoresistive and thermally responsive fibrous networks from the in situ growth of PEDOT on MWCNT-decorated electrospun PU fibers for pressure and temperature sensing

Flexible electronics have demonstrated various strategies to enhance the sensory ability for tactile perception and wearable physiological monitoring. Fibrous microstructures have attracted much interest because of their excellent mechanical properties and fabricability. Herein, a structurally robust fibrous mat was first fabricated by electrospinning, followed by a sequential process of functionalization utilizing ultrasonication treatment and in situ polymerization growth. Electrospun polyurethane (PU) microfibers were anchored with multi-walled carbon nanotubes (MWCNTs) to form conductive paths along each fiber by a scalable ultrasonic cavitation treatment in an MWCNT suspension. After, a layer of poly(3,4-ethylene dioxythiophene) (PEDOT) was grown on the surface of PU fibers decorated with MWCNTs to enhance the conductive conjunctions of MWCNTs. Due to the superior electromechanical behaviors and mechanical reinforcement of PEDOT, the PEDOT/MWCNT@PU mat-based device exhibits a wide working range (0–70 kPa), high sensitivity (1.6 kPa−1), and good mechanical robustness (over 18,000 cycles). The PEDOT/MWCNT@PU mat-based sensor also demonstrates a good linear response to different temperature variations because of the thermoelectricity of the PEDOT/MWCNT composite. This novel strategy for the fabrication of multifunctional fibrous mats provides a promising opportunity for future applications for high-performance wearable devices.

Surface Plasmon Resonance Sensor Based on Waveguides Inscribed in No-Core Fiber

We present a surface plasmon resonance (SPR) refractive index sensor based on femtosecond laser inscribed waveguides in a no-core fiber sandwiched between two sections of single mode fibers. The waveguides inscribed have a trapezoidal structure which consists of three sections: two slant waveguides to direct light out and back into the core of single mode fiber and a straight waveguide close to and in parallel with the surface of no-core fiber. A thin layer of Cr+Ag is coated on the surface of NCF to cover the straight waveguide region. The device is compact and has good mechanical robustness. The experimental results obtained show that the device has a refractive index sensitivity of ~3234 nm/RIU in the refractive index range of 1.34-1.37, and is expected to have practical applications in the fields of bio-medicine and environmental monitoring.

Superflexible Artificial Soft Wood.

Soft woods have attracted enormous interest due to their anisotropic cellular microstructure and unique flexibility. The conventional wood-like materials are usually subject to the conflict between the superflexibility and robustness. Inspired by the synergistic compositions of soft suberin and rigid lignin of cork wood which has good flexibility and mechanical robustness, an artificial soft wood is reported by freeze-casting the soft-in-rigid (rubber-in-resin) emulsions, where the carboxy nitrile rubber confers softness and rigid melamine resin provides stiffness. The subsequent thermal curing induces micro-scale phase inversion and leads to a continuous soft phase strengthened by interspersed rigid ingredients. The unique configuration ensures crack resistance, structural robustness and superb flexibility, including wide-angle bending, twisting, and stretching abilities in various directions, as well as excellent fatigue resistance and high strength, overwhelming the natural soft wood and most wood-inspired materials. This superflexible artificial soft wood represents a promising substrate for bending-insensitive stress sensors.

The Glaze Icing Performance of a Robust Superhydrophobic Film Composed of Epoxy Resin and Polydimethylsiloxane

Ice accretion on transmission lines can cause operational difficulties and disastrous events. In this study, a micro/nano-structured epoxy resin/polydimethylsiloxane (EP/PDMS) film on glass, with water droplet contact angles (CA) observed as high as 160° and the water droplet sliding angle (SA) < 1° was fabricated by aerosol-assisted chemical vapor deposition (AACVD). The glaze icing performance of the superhydrophobic EP/PDMS films have been investigated by comparing the bare glass and room temperature vulcanized (RTV) silicon rubber-coated glass substrate representing the glass insulators and silicone rubber insulators, respectively. Compared with the bare glass and the RTV silicon rubber coating, the EP/PDMS superhydrophobic coating showed excellent performance in delaying glaze icing, especially in the early stages of icing. After 20 min of glaze icing with tilting angle of 90° at −5 and −10 °C, 38.9% and 85.7% of the RTV silicon rubber coating were covered, respectively, and less than 3% of the EP/PDMS coating was covered by ice when the blank glass sheet was completely covered. The EP/PDMS films also showed good mechanical robustness and long-term stability, which are important considerations in their widespread real-world adoption.

Neuron-Inspired Sticky Artificial Spider Silk for Signal Transmission.

Neurons exhibit excellent signal transmission capacity, which inspire artificial neuron materials for applications in the field of wearable electronics and soft robotics. In addition, the neuron fibers exhibit good mechanical robustness by sticking to the organs, which currently has rarely been studied. Here, a sticky artificial spider silk was developed by employing a proton donor-acceptor (PrDA) hydrogel fiber for application as artificial neuron fibers. Tuning the molecular electrostatic interactions by modulating the sequences of proton donors and acceptors, enables combination of excellent mechanical properties, stickiness, and ion conductivity. In addition, the PrDA hydrogel exhibits high spinning capacity for a wide range of donor-acceptor combinations. The PrDA artificial spider silk would shed light on the design of new generation of artificial neuron materials, bio-electrodes, and artificial synapses. This article is protected by copyright. All rights reserved.

Stable Superhydrophobic and Antimicrobial ZnO/Polytetrafluoroethylene Films via Radio Frequency (RF) Magnetron Sputtering.

In this study, superhydrophobic ZnO/Polytetrafluoroethylene (ZnO/PTFE) films with water droplet contact angles (CA) observed as high as 165° and water droplet sliding angles of (SA) <1° have been prepared on glass substrates by RF magnetron sputtering. The PTFE was wrapped on a nano-rod made of a ZnO film with superhydrophobic properties while providing excellent UV resistance compared to hexadecyltrimethoxysilane (HDTMS) hydrophobic agents. The upper surface of the rough ZnO film was coated with PTFE, and most of the underlying coating was bare ZnO, which could well make contact with bacteria. For the Gram-negative strain, E. coli, the cell viability count of the ZnO/PTFE sample (3.5 log reduction, 99.96%) was conspicuously lower than that of the ZnO/HDTMS sample (1.2 log reduction, 93.87%) under 1 h illumination of UV light, which showed that the ZnO/PTFE sample has a better photocatalytic property than the ZnO/ HDTMS films. The ZnO/PTFE films also showed good mechanical robustness, which is an important consideration in their widespread real-world adoption.

A Wideband Millimeter-Wave Corrugated Horn at 30–50 GHz Taking Advantage of All-Metal 3-D Printing Fabrication

The development of commercial all-metal 3D-printing technology provides a new fabrication method for wideband millimeter-wave corrugated horns up to 50 GHz. Compared with conventional fabrication techniques, such as direct machining, electroforming or recently developed methods relying on the assembly of platelets, all-metal 3D-printing has advantages of low cost, fast delivery, possibility of mass production, flexibility in fabrication of complicated geometries and good mechanical robustness. In this letter, we report the development of a wideband millimeter-wave corrugated horn at 30-50 GHz (50% fractional bandwidth) based on commercial all-metal 3D-printing technology. Measurement results reported in this letter show good performance in terms of both return loss and cross-polarization.

Robust, anti-icing, and anti-fouling superhydrophobic coatings enabled by water-based coating solution

Superhydrophobic coatings have a wide range of applications in all areas of our lives, however, poor mechanical robustness limits their practical use. The use of organic solvents to prepare coatings can pose safety and environment pollution problems, also increase the cost of production. Water-based coating solution is used to prepare superhydrophobic coatings, which are safe and easy to scale. Thus, we demonstrate that silica nanoparticles, fluorinated alkyl silanes (FAS), fluorocarbon surfactants (FS-3100), and water can form stable system for preparation of superhydrophobic coatings on soft and hard substrates. After coating treatment, the superhydrophobic coatings exhibit excellent chemical stability (resistant to acid, alkali, salt, and ultraviolet radiation) and good mechanical robustness due to superhydrophobicity and crosslinking effects of FAS and FS-3100. Furthermore, the superhydrophobic coatings can delay water freezing time and poses superior anti-icing performance. This simple water-based coating solution may provide a new way of thinking for the later development of new coating technologies that are economical for all applications.

Durable superhydrophobic coatings for prevention of rain attenuation of 5G/weather radomes

Superhydrophobic coatings are expected to solve the rain attenuation issue of 5G radomes. However, it is very challenging to design and construct such superhydrophobic coatings with good impalement resistance, mechanical robustness, and weather resistance, which remains as one of the main bottlenecks hindering their practical applications. Here, we report the design of superhydrophobic coatings with all these merits mentioned above by spray-coating a suspension of adhesive/fluorinated silica core/shell microspheres onto substrates. The core/shell microspheres are formed by phase separation of the adhesive and adhesion between the adhesive and fluorinated silica nanoparticles. The coatings have an approximately isotropic three-tier hierarchical micro-/micro-/nanostructure, a dense but rough surface at the nanoscale, and chemically inert composition with low surface energy. Consequently, the coatings show excellent impalement resistance, mechanical robustness and weather resistance compared with previous studies, and the mechanisms are revealed. Furthermore, we realize large-scale preparation, extension, and practical application of the coatings for efficiently preventing rain attenuation of 5G/weather radomes. By taking these advantages, we believe that the superhydrophobic coatings have great application potential and market prospect. The findings here will boost preparation and real-world applications of superhydrophobic coatings.

Economical preparation of fluorine‐containing thermoplastic elastomer with good phase miscibility and elasticity based on dynamic vulcanization

AbstractThermoplastic elastomers are a green and sustainable category of high performance polymers and show the great advantage of easy processability relative to conventional rubbers. In this work, a fluorine‐containing thermoplastic elastomer was prepared through dynamic crosslinking of poly(vinylidene fluoride)/poly(ethylene−methyl acrylate−glycidyl methacrylate) (PVDF/EGMA) blends with the aid of amino‐terminated crosslinker (KH602). The reaction kinetics of EGMA with KH602 were evaluated by the DSC Kissinger method with an activation energy (Ea) of 103.04 kJ mol−1. The increased ‘S‐type’ torque curve during dynamic crosslinking indicates the occurrence of chemical crosslinking while Fourier transform infrared spectra further demonstrate the dehydrofluorination of PVDF and the reaction between the amino group of KH602 and the epoxy group in EGMA. The prepared PVDF/EGMA (30/70) thermoplastic vulcanizate shows good reprocessability, mechanical robustness and elasticity. With increasing content of crosslinker, the stress at 300% increases from 2.3 MPa to 3.5 MPa while elongation at break decreases from 1150% to 380%. The PVDF/EGMA blend has a typical ‘sea‐island’ morphology with ca 7 μm dispersed phase while PVDF/EGMA thermoplastic vulcanizates have gradually elongated disperse phases due to improved interfacial miscibility as evidenced by quantitative nanomechanical mapping AFM modulus analysis. Therefore, dynamic vulcanization is an effective and economical approach to integrate thermoplasticity and rubber elasticity into plastic/rubber pairs with good phase miscibility. © 2023 Society of Industrial Chemistry.

Improved photovoltaic performance and robustness of all-polymer solar cells enabled by a polyfullerene guest acceptor

Fullerene acceptors typically possess excellent electron-transporting properties and can work as guest components in ternary organic solar cells to enhance the charge extraction and efficiencies. However, conventional fullerene small molecules typically suffer from undesirable segregation and dimerization, thus limiting their applications in organic solar cells. Herein we report the use of a poly(fullerene-alt-xylene) acceptor (PFBO-C12) as guest component enables a significant efficiency increase from 16.9% for binary cells to 18.0% for ternary all-polymer solar cells. Ultrafast optic and optoelectronic studies unveil that PFBO-C12 can facilitate hole transfer and suppress charge recombination. Morphological investigations show that the ternary blends maintain a favorable morphology with high crystallinity and smaller domain size. Meanwhile, the introduction of PFBO-C12 reduces voltage loss and enables all-polymer solar cells with excellent light stability and mechanical durability in flexible devices. This work demonstrates that introducing polyfullerenes as guest components is an effective approach to achieving highly efficient ternary all-polymer solar cells with good stability and mechanical robustness.

Facile preparation of robust microgrooves based photonic crystals film for anti-counterfeiting

Photonic crystals structural colors have many advantages (e.g., environmentally friendly, nonfading, etc.), showing great potential application in some emerging fields of display, detection and anti-counterfeiting. Unfortunately, they are easily damaged because of the poor mechanical robustness origined from the weak interfacial adhesion between film substrate and nanoparticles. Although some photonic crystals show good mechanical robustness, they are often suffered from complex methods. Therefore, it is still a huge challenge to prepare photonic crystals with good mechanical robustness via facile methods. Herein, an efficient and facile strategy to prepare polycarbonate (PC)/silica nanoparticles (SNPs) photonic crystals film based on microgrooves is proposed. That is, with the help of micromilling and vacuum-assisted hot-pressor, microgrooves were prepared onto PC film surface, and SNPs can be spontaneously deposited into the as-prepared microgrooves via capillary force. Such PC/SNPs photonic crystals film exhibits excellent mechanical robustness, vivid structural color, and color can change with the viewing angle. Interestingly, such films with quick response (QR) code pattern can store information and can be used as anti-counterfeiting labels. This work proposes a facile strategy to prepare microgrooves based photonic crystals film with good mechanical robustness, which can further expand its applications in anti-counterfeiting.

Unidirectional Nanopore Dehydration Induces a Highly Stretchable and Mechanically Robust Silk Fibroin Membrane Dominated by Type II β-Turns.

Aqueous silk fibroin solution is dehydrated by evaporation into a water-soluble cast film (SFME) with poor mechanical properties but becomes by unidirectional nanopore dehydration (UND) into silk fibroin membrane (SFMU) with water-stable and good mechanical robustness. The thickness and tensile force of the SFMU are almost twice those of the MeOH-annealed SFME. The UND-based SFMU has a tensile strength of 15.82 MPa, an elongation of 665.23%, and a type II β-turn (Silk I) that accounts for 30.75% of the crystal structure. Mouse L-929 cells adhere, grow, and proliferate well on it. The UND temperature can be used to tune the secondary structure, mechanical properties, and biodegradability. UND induced the oriented arrangement of the silk molecules, which led to the formation of the SFMU dominated with Silk I structure. The silk metamaterial by controllable UND technology has great potential in medical biomaterials, biomimetic materials, sustained drug release, and flexible electronic substrates.

A Flytrap‐Inspired Bistable Origami‐Based Gripper for Rapid Active Debris Removal

Space debris is considered an increasingly serious threat to on‐orbit spacecrafts. There are several potential solutions to this problem, including active debris removal. Flexible robots have shown promising adaptability and dexterity in soft manipulation owing to their inherent compliance. This compliance allows them to interact safely and efficiently during space missions such as active debris removal. Herein, inspired by the bistable structure and energy‐release mechanism of the Venus flytrap, a bistable origami‐based gripper is developed. The flexible gripper, which can rapidly achieve stable state switching, is in the form of a biomimetic flytrap leaf curvature and is actuated using a shape memory alloy actuator. Subsequently, a flytrap bristle‐like locking structure is used to ensure locking via the action of a dielectric elastomer actuator to alleviate the vibration instability of the flexible robot under rapid actuation. The experimental results showed that the flexible gripper can achieve effective capture within approximately 300 ms. In addition, it exhibits good adaptability and mechanical robustness with targets having complex shapes and sizes, indicating its potential applications in the space capture and sampling fields.

Flexible self-powered DUV photodetectors with high responsivity utilizing Ga2O3/NiO heterostructure on buffered Hastelloy substrates

In this research, β-Ga2O3/NiO heterostructures were grown directly on CeO2 buffered Hastelloy flexible substrates. With pulsed laser deposition under high temperatures, as-grown β-Ga2O3 and NiO thin films have a preferred out-of-plane orientation along the ⟨−201⟩ and ➎111➉ directions. This is due to the ideal epitaxial ability of the CeO2 buffer layer, which serves as a perfect template for the epitaxial growth of single-oriented NiO and β-Ga2O3 by creating a constant gradient from CeO2 (2.7 Å along ➎001➉) to NiO (2.9 Å along ➎110➉), and eventually to β-Ga2O3 (3.04 Å along ➎010➉). The Hastelloy substrates endow photodetectors with good deformability and mechanical robustness. Moreover, owing to the type-II band alignment of β-Ga2O3/NiO heterostructures, the photodetectors have a good photocurrent at zero bias under 284 nm of light illumination. In addition, the photocurrent is significantly higher than when using an analogous heterostructure (as described in some previous reports), because the β-Ga2O3 and NiO thin films are crystalized along a single orientation with fewer defects.

Highly Flexible Triboelectric Nanogenerator Using Porous Carbon Nanotube Composites.

The rapid development of portable and wearable electronic devices has led researchers to actively study triboelectric nanogenerators (TENGs) that can provide self-powering capabilities. In this study, we propose a highly flexible and stretchable sponge-type TENG, named flexible conductive sponge triboelectric nanogenerator (FCS-TENG), which consists of a porous structure manufactured by inserting carbon nanotubes (CNTs) into silicon rubber using sugar particles. Nanocomposite fabrication processes, such as template-directed CVD and ice freeze casting methods for fabricating porous structures, are very complex and costly. However, the nanocomposite manufacturing process of flexible conductive sponge triboelectric nanogenerators is simple and inexpensive. In the tribo-negative CNT/silicone rubber nanocomposite, the CNTs act as electrodes, increasing the contact area between the two triboelectric materials, increasing the charge density, and improving charge transfer between the two phases. Measurements of the performance of flexible conductive sponge triboelectric nanogenerators using an oscilloscope and a linear motor, under a driving force of 2-7 N, show that it generates an output voltage of up to 1120 V and a current of 25.6 µA. In addition, by using different weight percentages of carbon nanotubes (CNTs), it is shown that the output power increases with the weight percentage of carbon nanotubes (CNTs). The flexible conductive sponge triboelectric nanogenerator not only exhibits good performance and mechanical robustness but can also be directly used in light-emitting diodes connected in series. Furthermore, its output remains extremely stable even after 1000 bending cycles in an ambient environment. In sum, the results demonstrate that flexible conductive sponge triboelectric nanogenerators can effectively power small electronics and contribute to large-scale energy harvesting.

A fast-setting and eco-friendly superhydrophobic high belite sulphoaluminate cement mortar

High belite sulphoaluminate cement (HBSC) has shown great potential as new lower CO2 footprint cementitious material. It makes sense to improve the hydrophobic property of HBSC to obtain high durability performance. In this paper, nontoxic short carbon chain lauric acid (LA) is used to match the early strength characteristic of HBSC to prepare fast-setting and eco-friendly LA-modified HBSC mortar (M-HBSCM). Sands modified with LA provide low surface energy for an integral hydrophobic effect. M-HBSCM exhibits superhydrophobicity even after hammering to expose the fractured internal structure, with a contact angle of 153.2°. And it shows outstanding self-cleaning property against contaminants such as sand and wet mud and a reduction in water absorption to around 23% of the ordinary HBSCM (O-HBSCM). The fabricated M-HBSCM has fast-setting property with an initial setting time of 29 min and a final setting time of 36 min. The abrasion test displays that the scratched area remains well superhydrophobic with high mechanical robustness when the droplets roll off on the inclined surface. Field-emission scanning electron microscope (FESEM) indicates that M-HBSCM contains more pores and coarser hydration products. The system of calcium alumina and pores exhibits a distinct hierarchical structure, providing the multilevel roughness required for the superhydrophobic surface. Fourier transform infrared (FTIR) spectrometer indicates that low surface energy functional groups have been successfully grafted onto M-HBSCM. The superhydrophobic concrete has good mechanical robustness, corrosion resistance, and fast-setting property, which can meet the demands of grouting reinforcement projects, the repair of various concrete structures, corrosion protection of marine structures and other projects.

Flexible, robust, sandwich structure polyimide composite film with alternative MXene and Ag NWs layers for electromagnetic interference shielding

The design and fabrication of electromagnetic interference shielding films with a novel structure to eliminate undesirable electromagnetic pollution is an important research direction. However, it is still a challenge to combine and organize nanofillers in different dimensions into the structured network in polymer-based electromagnetic interference (EMI) shielding composites. In this work, a sandwich structure polyimide (PI) composite film with alternative 2D-MXene network and 1D-Silver nanowires (Ag NWs) network was prepared through the “electrospinning-immersion-hot pressing” method. With the increase of Ag NWs content, the EMI shielding effectiveness (SE) gradually increases while maintaining good flexibility and mechanical robustness. The EMI SE and the tensile strength of 150 μm thick sandwich composite film can reach up to 79.54 dB and 39.82 MPa, respectively. The prepared flexible and robust PI composite film with a sandwich structure has high EMI SE with less metal content, which can provide guidelines for the development of high-performance EMI polymeric films with potentials in wearable devices and equipment.

Large‐Area and Flexible Plasmonic Metasurface for Laser–Infrared Compatible Camouflage

AbstractDue to interminable surveillance and reconnaissance through various sophisticated multispectral detectors, the need for multispectral compatible camouflage is now more than ever. Here, a flexible plasmonic metasurface is proposed to simultaneously realize low reflection at representative lasers (i.e., 1.06, 1.55, and 10.6 µm) and low emission in the atmosphere windows of both 3–5 and 8–14 µm. High absorption for both 1.06 and 1.55 µm lasers is realized by the destructive‐interference design of the multilayer Au/Ge/Ti/Ge films, while low reflection for the 10.6 µm laser results from the coding metasurface design, and low emission is attributed to ultrahigh reflection of the continuous Au/Ge/Ti/Ge films in the atmosphere windows. As a proof of concept, a flexible metasurface sample (10 cm × 10 cm) is prepared by the soft‐lithography technology. The measured specular reflectivities are 0.017, 0.13, and 0.17 at wavelengths 1.06, 1.55, and 10.6 µm, respectively. Meanwhile, the average emissivities are 0.19 and 0.11 in 3–5 and 8–14 µm, respectively. Additionally, the flexible metasurface also exhibits integrated advantages including easy mass fabrication, good mechanical flexibility and robustness, super‐hydrophobic characteristic, unambiguously demonstrating the success of the design strategy for promoting multispectral compatible camouflage.