Self-healing Effect Research Articles

Structurally Dynamic Gelatin-Based Hydrogels with Self-Healing, Shape Memory, and Cytocompatible Properties for 4D Printing.

Three-dimensional (3D) printable hydrogels with a shape memory effect have emerged as a new class of 4D printing materials recently and found wide applications in various fields. However, synergistically endowing such materials with good mechanical strength and biocompatibility for biomedical uses remains challenging. In this study, a series of multiresponsive hydrogels have been prepared through a dynamic covalent imine/Diels-Alder network from biocompatible starting materials of modified gelatin and poly(ethylene glycol)-based polymers. By further secondary crosslinking with a hyperbranched triethoxysilane reagent (HPASi) that contains multiple supramolecular hydrogen bonding, the hydrogels presented a strengthened self-healing and temperature-responsive shape memory effect. With the additional features of superior stretchability (elongation at break up to 523%), good cytocompatibility, and 3D printable properties, these multifunctional hydrogels showed great potential for broad biomedical applications.

Effect of types of curing environments on the self-healing capacity of mortars incorporating crystalline admixture

The presence of microcracks can lead to a reduction in the durability of concrete structures. In recent years, crystalline admixture has been used to repair microcracks in concrete. In this study, the effect of different amounts of crystalline admixture on the performance of mortar was firstly determined. In order to reveal the purpose of this study, a mortar with 4% crystalline admixture has been healed under three types curing environments (standard curing, water immersion, and saturated calcium hydroxide solution). The self-healing effect of the specimens was characterized macroscopically by water absorption tests and visualized crack images after repair. The type of crack filler was determined by microscopic analysis experiments XRD and SEM-EDX. The experimental results show that, firstly, the self-healing effect of mortar with crystalline admixture is limited by standard curing environments. Secondly, water immersion environment plays a weak role in promoting crack healing of mortars without crystalline admixture, and the addition of crystalline admixture leads to self-healing of the mortar due to a large amount of production of hydrated calcium silicate. Finally, the saturated calcium hydroxide solution has a beneficial effect on the self-healing of cracks in mortars without crystalline admixture due to the precipitation of calcium hydroxide from the healing solution. After the addition of crystalline admixture to the mortar, calcium ions and water promote the generation of calcium silicate hydrate, and the precipitation of calcium hydroxide acts together to fill the crack, resulting in the crack being completely healed.

A Metal Coordination-Based Supramolecular Elastomer with Shape Memory-Assisted Self-Healing Effect.

Rubber materials are widely used in aerospace, automotive, smart devices and artificial skin. It is significant to address the aging susceptibility of conventional vulcanized rubber and to impart it rapid self-healing performance for destructive crack damage. Herein, a novel supramolecular rubber elastomer is prepared by introducing metal coordination between carboxyl-terminated polybutadiene and polystyrene-vinylpyridine copolymer. Based on the metal coordination interaction, the elastomer exhibits shape memory and self-healing properties. Moreover, a rapid closure-repair process of destructive cracks is achieved by presetting temporary shapes. This shape memory-assisted self-repair model is shown to be an effective means for rapid repair of severe cracks. An approach to enhance the mechanical and self-healing properties of elastomer was demonstrated by adding appropriate amounts of oxidized carbon nano-onions (O-CNO) into the system. The tensile strength of the elastomer with an O-CNOs content of 0.5 wt% was restored to 83 ± 10% of the original sample after being repaired at 85 °C for 6 h. This study confirms that metal coordination interaction is an effective method for designing shape memory self-healing rubber elastomer. The shape memory-assisted self-healing effect provides a reference for the rapid self-repairing of severe cracks.

Effect of Superabsorbent Polymers on the Self-Healing Properties of Pre-Damaged Concrete

Cracks in concrete structures reduce bearing capacity, durability, and safety. This paper reveals the effect of superabsorbent polymers (SAP) on the self-healing property of pre-damaged concrete based on mechanical properties tests, mercury intrusion porosimetry, scanning electron microscopy, and energy dispersive spectrometer. The experimental results show that SAP reduces the mechanical properties of the SAP-modified concrete under the same W/C ratio, but a small amount of SAP can improve the later strength under the 0.35 W/C ratio. The addition of SAP increased the volume of small capillary pores (<20 μm) and large capillary pores (>100 μm) and significantly reduced the former with an increase in age. The SEM-EDS analysis indicates that the water released by SAP promotes the formation of C-S-H gel. AFt in the cracks is the main reason for self-healing, and the addition of CO2 to produce calcium carbonate is another one. Furthermore, this study finds that SAP-modified concrete has the best self-healing effect and the densest structure when the W/C ratio is 0.35 and the SAP content is 0.25%. The self-healing performance makes the SAP-modified concrete have broad application prospects.

Experimental and numerical investigation of magnetic converge effect of magnetically conductive asphalt mixture

Nowadays, although the technical bottleneck of the poor self-healing effect of the inductive healing asphalt mixture (IHAM) caused by uneven temperature distribution in the lower part has been found, it has not been properly solved until now. Given that, this paper innovatively proposes to design the magnetically conductive asphalt mixture (MCAM) containing waste ferrites, and use its magnetic converge effect to improve the temperature field distribution of the lower part of the IHAM. Firstly, four kinds of MCAMs were designed based on the magnetic circuit model. Then the magnetic permeability tests, volumetric and mechanical performance tests of the MCAMs were conducted. Finally, the 2D electro-magneto-thermal coupling model of the MCAM composite IHAM at different heating frequencies and power was established. Test results show that the relative magnetic permeability of the MCAM is close to 60 when all aggregates and fillers are substituted by waste ferrites. Further, simulation results show that MCAM’s magnetic converge effect can guide and concentrate the magnetic field to greatly improve the temperature of the lower part of IHAM, and the higher the heating power or frequency, the better the temperature improvement effect of the lower part of the IHAM. Finally, the optimal scheme for substituting coarse aggregate with waste ferrites is recommended for MCAM preparation based on the simulation and experimental results.

Benzotriazole corrosion inhibitor loaded nanocontainer based on g-C3N4 and hollow polyaniline spheres towards enhancing anticorrosion performance of waterborne epoxy coatings

Multi-dimensional composite nanocontainers provided an opportunity to prolong the service life of waterborne self-healing coatings through combining intelligent protection with physical barrier. Herein, we constructed a benzotriazole (BTA) corrosion inhibitor loaded nanocontainer with barrier/controlled release/corrosion inhibition properties by assembling graphitic (g)-C3N4 lamella, hollow polyaniline capsule and outer polydopamine wall. Hollow polyaniline and g-C3N4 lamella with adsorption properties provide effective space and sites for loading BTA corrosion inhibitor. Outer polydopamine wall can not only realize the controlled release of corrosion inhibitor, but also ensure the good compatibility between the composite container and the water-based epoxy resin. In addition, polydopamine (PDA) and polyaniline (PANI) as a container frame can also serve as active inhibitors after the release of corrosion inhibitor to enhance the self-healing protection effect of waterborne coatings. In comparative evaluation, the composite coatings containing BTA-loaded nanocontainers (0.5 wt.%) exhibit obviously physical barrier effect after soaking in 3.5 wt.% NaCl solution for 40 days, and maintains good protective performance after immersion for 80 days. Meanwhile, the artificial scratch experiment verified the effective self-repair protection of the composite container to the coating under the condition of damage. To be sure, it will provide an effective improvement idea for the long-term application of waterborne epoxy coating in marine environment.

Aptamer-Gated Mesoporous Silica Nanoparticles for N Protein Triggered Release of Remdesivir and Treatment of Novel Coronavirus (2019-nCoV).

Since the 2019-nCoV outbreak was first reported, hundreds of millions of people all over the world have been infected. There is no doubt that improving the cure rate of 2019-nCoV is one of the most effective means to deal with the current serious epidemic. At present, Remdesivir (RDV) has been clinically proven to be effective in the treatment of SARS-CoV-2. However, the uncertain side effects make it important to reduce the use of drugs while ensuring the self-healing effect. We report an approach here with targeted therapy for the treatment of SARS-CoV-2 and other coronaviruses illness. In this study, mesoporous silica was used as the carrier of RDV, the nucleocapsid protein (N protein) aptamer was hybridized with the complementary chain, and the double-stranded DNA was combined with gold nanoparticles as the gates of mesoporous silica pores. When the RDV-loaded mesoporous silica is incubated with the N protein, aptamer with gold nanoparticles dissociate from the complementary DNA oligonucleotide on the mesoporous silica surface and bind to the N protein. The releasing of RDV was determined by detecting the UV-vis absorption peak of RDV in the solution. These results show that the RDV delivery system designed in this work has potential clinical application for the treatment of 2019-nCoV.

Self-healing characteristics of cement concrete containing expansive agent

Many studies have been conducted to identify the self-healing effect in cementitious materials. However, the knowledge regarding the self-healing effect is insufficient to utilize this effect for design purposes. This study examined the influence of numerous admixtures such as expansive agents (EA), ultra-fine fly ash (UFFA), finely ground granulated blast furnace slag (FGGBS), and silica fume (SF) on the self-healing capacity of Portland cement concrete. Here, focused on investigating the effect of the expansive agent (EA) used in concrete mixtures to identify whether the EA could act as a self-healing trigger in concrete materials that are frequently used in a bridge deck overlay. Ordinary Portland cement concrete (OPC), latex-modified concrete (LMC), and silica fume concrete (SFC) was used to compare the effect of the EA (0,4,8%, and 12%) in the ternary blended cement concrete on each material for bridge deck overlay concrete. In this study, the crack width was examined at 0,7,14 and 28 days respectively which were inducement at 3 and 7 days age of concrete specimens by the microscopic image analysis system. Samples with healed cracks with a width range of 100–200 µm and EA ≥ 8% on day 28 exhibited faster self-healing performance. Additionally, we calculated the self-cracking closing ratio and performed a microstructure analysis by SEM/EDS. Moreover, the compressive strength was examined at 7, 28,56, and 90 days for understanding the improved performance of all concrete mixtures.

Quantification of Self-Healing Effect of Bacillus Subtilis on Cementitious Material

The creation of smart self-healing materials and preventativerepair techniques is required due to the growing concern for the safety and sustainability of buildings. Although the development of microcracks rarely affects a building's structural qualities, the increased permeability caused by microcrack networking poses a significant threat to the durability of concrete structures by increasing the likelihood that aggressive materials will enter the structure. This studyevaluates the self-healing capacity of bacterial concrete with that of traditional concrete. Bacterial spores and calcium lactate, a two-component biochemical agent, are released from the particle by crack ingress water upon fracture development. The self-healing agent is embedded into the cement mortar and its behavior is studied. Control and bacterial specimens are cast and the tests like compressive strength, porosity, UPV test, ESEM, EDAX are done. The results were studied for 15,30 and 45 days of healing. After 45 days submerged in water, experimental results revealed crack-healing of up to 7.6% of cracks in bacterial concrete but only up to 2.46% of cracks in control specimens.

Self-healing mechanism of deposited carbonates in cement cracks under CO2 storage well conditions

In CO2 geological storage wells, the leakage of CO2 along the micro-cracks of the cement sheath of abandoned wells is one of the main risks of CO2 leakage. The chemical reaction between CO2 and oil well cement can realize self-healing of micro-cracks in the cement sheath. In this study, self-healing experiments of artificial cracks in cement-based materials were carried out by simulating the working conditions of high temperature, high pressure and CO2-rich CCS. The formation process and self-healing effect of calcium carbonate (CaCO3) in oil well cement-based materials induced by CO2 under different exposure environments were explored, and the self-healing products were analyzed by X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM and EDX). X-ray computed tomography (μ-CT) was used to reconstruct the changes of cracks in 3D, and compressive strength, porosity, and permeability were used to evaluate the self-healing properties of cement-based material cracks. The results indicated that for the CS-28 (the samples reacted with humid CO2 for 28 days) and AS-28 (the samples reacted with humid air for 28 days) samples, the compressive strength increased by 56.67% and 10.38%, the porosity decreased by 59.37% and 18.19%, and the permeability decreased by 59.91% and 28.07%, respectively. The crack-volume reduction rate of the CS-28 specimen was 57.08%, and the pore-volume reduction rate was 69.20%. Many massive, needle shaped CaCO3 crystals were formed in the pores and cracks of the sample. The reconstruction of the 3D structure of self-healing cement shows that the micro-cracks of the cement are sealed but the pores are increased. The damage prediction based on von Mises stress shows that under the axial force, the healing layer is not prone to damage. This study provides a theoretical and experimental basis for applying self-healing technology in CCS downhole environment, improving the service life of cement sheath and preventing the leakage of stored CO2.

Self-healing and enhanced anticorrosion coatings based on graphene-reinforced brominated butyl rubber ionomer

Heavy-duty anticorrosive applications usually require coatings to possess self-healing ability and high protection efficiency. In this paper, we propose a self-healing anticorrosion coating based on graphene (GP)-reinforced brominated butyl rubber (BIIR) ionomer. An ionomer with a reversible ionic network is fabricated by crosslinking BIIR with tert-butylpyridine and then compounded with GP nanosheets. The π-cationic interactions between GP nanosheets and pyridyl groups result in high interfacial contact. The interfacial contact promotes the dispersion of GP nanosheets in the polymer matrix, increasing the difficulty of corrosive chemical diffusion. Such material design enables the protection efficiency of the coating for a steel substrate to exceed 99 % in strong acid, strong alkali or high salt corrosive solutions. Furthermore, the coating exhibits high self-healing effectiveness in corrosive solutions. The recovered protection effectiveness is as high as 97.7 % after 24 h of self-healing. The coatings' remarkable anticorrosive and self-healing properties allow them to improve the service life of metallic equipment and components under harsh working situations.

Infrared-light-driven self-healing MoS2/polyvinyl alcohol hydrogel with simultaneous enhancement of strength and ductility

Self-healing hydrogels exhibit special self-healing or self-recovery function like human skin after injuring, thereafter, draw lots of attention in biomedical applications. However, self-healing hydrogels with strong mechanical and rapid self-healing properties are not fully realized. MoS 2 /polyvinyl alcohol (PVA) hydrogels are developed to achieve rapid self-healing function by utilizing the excellent photothermal conversion effect of MoS 2 under near-infrared (NIR) light. Effects of microstructure and content of MoS 2 on self-healing and mechanical properties of MoS 2 /PVA hydrogels are investigated, including flower-like MoS 2 spheres by bottom-up hydrothermal reaction and MoS 2 sheets by liquid-phase stripping method. The MoS 2 /PVA hydrogels embodied with the two types of MoS 2 were produced by simple freezing/thawing method, and exhibited rapid self-healing function, together with simultaneous enhancement of strength and ductility. The MoS 2 /PVA hydrogel modified by flower-like MoS 2 spheres with a content of 0.5 wt% presents a significant self-healing function with a healing efficiency up to 90.0% within 5 min, and an enhancement of tensile strength of 9.1 MPa (190% to blank PVA) and a ductility of 162.5% (290% to blank PVA). Furthermore, the MoS 2 /PVA gel with flower-like MoS 2 spheres into the PVA networks produces a significant enhancement of fracture strength (58.4 MPa) after fully curing, characterized by an increases of 612% compared with the pure PVA. The photo-induced self-healing and strengthening effects of the MoS 2 /PVA hydrogels are discussed. • A rapid self-healing MoS 2 /PVA hydrogels is developed under near-infrared light. • Photo-thermal conversion effect of MoS 2 produces the self-healing property. • Flower-like MoS 2 spheres exhibit better healing efficiency than MoS 2 sheets. • MoS 2 /PVA hydrogels present a simultaneous increase of strength and plasticity. • 2D and 3D strengthening effects of the MoS 2 /PVA composites are discussed.

Trigger and response mechanisms for controlled release of corrosion inhibitors from micro/nanocontainers interpreted using endogenous and exogenous stimuli: A review

• Review triggering mechanisms of corrosion inhibitor release from containers • Introduce three aspects of endogenous, exogenous, and multiple stimuli • Classify corrosion inhibitor-containers into inorganic, organic, and hybrid • Discuss development prospect and research strategy of micro/nanocontainers Metallic corrosion can lead to both economic losses and environmental pollution due to undesired chemical and biochemical reactions. Furthermore, there are a number of drawbacks associated with different corrosion prevention and mitigation techniques. In view of these challenges, corrosion inhibitor-based smart micro/nanocontainers (CISCs) with stimuli-responsive functionality emerge as an important alternative technical approach in dealing with metallic corrosion. The development of CISCs involves controlled release corrosion inhibitors and self-healing coatings. This review focuses on the trigger and response mechanisms of controlling the discharge of corrosion inhibitors from micro/nanocontainers (a core–shell or layered structure) into aqueous solution under endogenous (pH, redox, and ion-exchange), exogenous (temperature, magnetic field, and light), and multiple stimuli. When these CISCs are embedded into coating materials, the self-healing effect of the coating can manifest to protect various types of metals. In this review effort, different types of CISCs are classified for the first time into the following three categories: inorganic, organic, and organic-inorganic hybrid. We also discuss application scope, future perspectives, and research strategies for CISCs in the hopes of increasing the life of corrosion protection and providing inspiration in related fields.

Effect of SiCnws@BN core shell upon impact-ablation performance of HfC coating on C/C composites

To improve the thermal protection performance of HfC coating subject to impact, SiCnws@BN core-shell nanowire reinforced HfC coating was fabricated by chemical vapor deposition and compared to the SiCnws@PyC/HfC coating. The experiments showed that the ablation resistance of SiCnws@PyC/HfC coating decreased significantly. In comparison, the ablation resistance of SiCnws@BN/HfC coating was barely affected by impact. A dense oxide layer was formed on the surface of SiCnws@BN/HfC coating after impact and ablation. The shrinking and self-healing effect of SiCnws@BN during oxidation process was investigated, which explained the formation process of dense oxide layer.

Polymer coatings’ long-term adaptation and self-healing effects in corrosive media

Polymer coatings’ long-term adaptation and self-healing effects in corrosive media

Near-Infrared Responsive Smart Superhydrophobic Coating with Self-Healing and Robustness Enhanced by Disulfide-Bonded Polyurethane.

Synergistic self-healing materials and inorganic particles to create self-healing superhydrophobic surfaces for improving their robustness is a common technique, but the suitability between the two is rarely mentioned. In this work, we developed a multifunctional superhydrophobic coating with room-temperature stability, mechanical stability, self-healing, and NIR stimuli response, in which self-healing polyurethane (PU) serves as the interface reinforcement layer and poly(dopamine) (PDA)-coated flower-like ZnO composite particles serve as the hydrophobic layer. A series of temperature-dependent self-healing PU materials were designed and synthesized by regulating the ratio of hard and soft chain segments in PU, and the relationship between the healing temperature of PU and the hydrophobic stability of the composite coatings was investigated. Based on dynamic hydrogen and disulfide bonds, PUs displayed excellent self-healing performance. Thanks to the self-healing and interfacial strengthening effect of PU and the photothermal properties of PDA, the composite coating exhibits not only excellent mechanical stability but also rapid self-healing ability in response to NIR stimuli. Furthermore, the smart coating demonstrated superior self-cleaning and corrosion resistance. This work provides a reference for developing strong and stable water-repellent reversible superhydrophobic coatings with great potential and promising future.

Microstructure and Mechanical Properties of Ni-Based Complex Concentrated Alloys under Radiation Environment

The rapid development of fusion-reactor technology calls for excellent anti-irradiation materials. Complex concentrated alloy (CCA) is a newly proposed alloy concept which is a promising candidate of nuclear fusion materials by virtue of its great phase stability under irradiation. This article summarizes anti-radiation mechanism and the microstructure evolution in HEAs. The effective factors on irradiation behavior of HEAs, including entropy, sample size and temperature, are discussed. Finally, the article introduces the potential ways to solve the economic and environmental problems which the HEAs faced for their applications in the future. In summary, the HEAs usually show better irradiation resistance than traditional alloys, such as less swelling, smaller size of defects, and more stable mechanical properties. One possible reason for the irradiation resistance of HEA is the self-healing effect induced by the high-entropy and atomic-level stress among the metal atoms. The activation of the principal element should be considered when selecting components of HEA, and the high throughput technique is a potential way to reduce the design and fabrication cost of HEAs. It is reasonable to expect that coming years will see the application of novel HEAs in fusion reactors.

The self-healing of marine concrete cracks based on the synergistic effect of microorganisms and inorganic minerals

To achieve the goal of self-healing of marine concrete cracks and fixation of harmful ions invading the cracks, researches on the synergy of microbial mineralization and inorganic mineral hydration were carried out. The fixation effects of Cl−, SO42− and OH− in simulated solution with different inorganic mineral dosages were tested by experiments. Further, the growth performances of microorganisms in the modified simulated solution were also tested. Finally, the self-healing effect of cracks in cement-based materials was experimentally verified. The results showed that the Cl− and SO42− in the simulated solution can be effectively fixed by the double metal hydroxide, and combined with a part of H2O to form hydration products that accumulated in the deep region of the crack. A large amount of OH− were also consumed for the formation of double metal hydroxides, which greatly lowered the pH of the simulated solution. Thus, the chemical environment of the simulated solution became suitable for the growth of microorganisms, and the number of microorganisms in the solution increased significantly. Eventually, the hydration product and the mineralization product area were connected to form a superimposed repair zone, thereby expanding the repair scope. The test results could provide reference for concrete crack self-healing and anti-corrosion of buildings applied on marine environment.

Enhanced corrosion resistance and self-healing effect of sol–gel coating incorporating one-pot-synthesized corrosion inhibitor-encapsulated silica nanocontainers

Enhanced corrosion resistance and self-healing effect of sol–gel coating incorporating one-pot-synthesized corrosion inhibitor-encapsulated silica nanocontainers

Nano-sized cerium vanadium oxide as corrosion inhibitor: A microstructural and release study

• A simple chemical route to synthesize cerium vanadate. • Mixed nanostructure. • Cerium vanadate is an effective corrosion inhibitor for ferrous alloys. • It forms a layer on the steel surface. • Self-healing and smart corrosion inhibitor. The synthesized, nano-sized cerium vanadate is proposed as a self-healing corrosion inhibitor for ferrous alloys (e.g., automotive high strength steel (HSS) and mild steel (MS)). Cerium vanadate prepared at two different pH conditions (neutral and basic) showed similar corn-like morphology with nanorod structure. UV-Vis spectroscopy studies revealed that the release rate of cerium vanadate-B (basic condition) was higher than cerium vanadate-N (neutral condition) in 0.1 M NaCl solution. The specimen exposed to 0.1 M NaCl containing a supersaturated solution of cerium vanadate-B (1000 ppm) revealed 8 times and 6 times lower corrosion current density values for HSS and MS respectively than that of the one without corrosion inhibitor. There was a gradual increase in the film resistance ( R film ) on both HSS and MS observed as a function of exposure time in corrosive medium containing cerium vanadate-B inhibitor. An order higher impedance values were observed for both HSS and MS immersed for 168 h, highlighting the self-healing effect of the cerium vanadate compound. The X-ray photoelectron spectroscopy results showed the presence of multivalent oxidation states of both cerium and vanadium species. The inhibiting action is attributed to the high solubility of cerium vanadate in the corrosive medium to form a film on the metal surface. The dissolution/solubility of the corrosion inhibitor was more favorable in neutral to alkaline conditions than in acidic conditions.