Self-healing Mechanism Research Articles

Polymer Composites in 3D/4D Printing: Materials, Advances, and Prospects.

Additive manufacturing (AM), commonly referred to as 3D printing, has revolutionized the manufacturing landscape by enabling the intricate layer-by-layer construction of three-dimensional objects. In contrast to traditional methods relying on molds and tools, AM provides the flexibility to fabricate diverse components directly from digital models without the need for physical alterations to machinery. Four-dimensional printing is a revolutionary extension of 3D printing that introduces the dimension of time, enabling dynamic transformations in printed structures over predetermined periods. This comprehensive review focuses on polymeric materials in 3D printing, exploring their versatile processing capabilities, environmental adaptability, and applications across thermoplastics, thermosetting materials, elastomers, polymer composites, shape memory polymers (SMPs), including liquid crystal elastomer (LCE), and self-healing polymers for 4D printing. This review also examines recent advancements in microvascular and encapsulation self-healing mechanisms, explores the potential of supramolecular polymers, and highlights the latest progress in hybrid printing using polymer-metal and polymer-ceramic composites. Finally, this paper offers insights into potential challenges faced in the additive manufacturing of polymer composites and suggests avenues for future research in this dynamic and rapidly evolving field.

Nanoceramic-based coatings for corrosion protection: a review on synthesis, mechanisms, and applications.

Corrosion is a pervasive issue with significant economic and safety implications across various industries. Nanoceramic-based coatings have emerged as a promising solution for corrosion protection due to their unique properties and mechanisms. This review aims to comprehensively examine the synthesis, mechanisms, and applications of nanoceramic-based coatings for corrosion protection. The review begins by highlighting the importance of corrosion protection and its impact on different industries. It introduces nanoceramic-based coatings as a potential solution to address this challenge. The objective is to provide a thorough understanding of the synthesis methods, mechanisms, and applications of these coatings. The fundamental principles of corrosion and different corrosion mechanisms are discussed, along with the limitations of traditional corrosion protection methods. The review emphasizes how nanoceramic-based coatings can overcome these limitations and provide superior corrosion resistance. Various synthesis methods, including sol-gel, electrodeposition, and physical vapor deposition, are described in detail, along with the factors influencing the synthesis process. Recent advancements and innovations in nanoceramic coating synthesis techniques are also highlighted. This looks at how coatings made with tiny ceramic particles protect against corrosion. It examines the importance of small-scale details like particle size, shape, and what the particles are made of. The formation of passive layers, self-healing mechanisms, and barrier properties of nanoceramic coatings are explained. The diverse applications of nanoceramic coatings for corrosion protection in industries such as automotive, aerospace, and marine are comprehensively discussed. Case studies and examples demonstrating the significant corrosion resistance and improved performance achieved with nanoceramic coatings are presented.

The effect of micromechanical stresses on vacancy formation and stress-driven mass-transport in polycrystalline Fe–Au alloy

In recent years, a new class of super saturated binary and ternary alloys have demonstrated the ability for the self-healing of creep-induced voids formed at the grain boundaries. However, a clear understanding of the parameters affecting the self-healing mechanism is still not yet complete. One of the main challenges is understanding the effect of microstructure and micromechanical stresses on the redistribution of the healing-solute and vacancies. To this end, we address this issue using a CALPHAD-informed diffusion model coupled with crystal plasticity. In principle, the approach is general and can be used for any binary Fe–X alloy, but in this work Fe–Au binary system is used since it experimentally showed the best healing efficiency. First, we present a multicomponent diffusion model considering cross and stress-driven diffusion. The effect of stress was also considered on the equilibrium vacancy concentration. To investigate the effect of the micromechanical stresses, a representative volume element (RVE) was obtained using the phase-field method. The results showed that the maximum vacancy concentration is at the grain boundaries (GBs) with the highest hydrostatic tensile stresses. These were also the regions of the highest Au enrichment. A crucial factor to achieve this is the high diffusivity of Au compared to the Fe matrix. Increasing the stresses, lead to an increase both in vacancy and Au concentration. The accompanying increased stress triaxiality is suggested to be the reason for the reduced self-healing efficiency observed in previous experimental studies.

Molecular hard-segment engineered polyurethane with thermochromism, shape memory, humidity-driven, and self-healing capabilities

In nature, complex camouflage, locomotion, and self-healing mechanisms are key instinctive abilities that give organisms a survival advantage. Imitating these fascinating multi-stimulus responses has significant implications for scientists developing novel bionic smart materials. Here, we have developed a new polyurethane material (TASNPU30) by copolymerizing dihydroxy-functionalized tetraarylsuccinonitrile (TASN-diol), polyethylene glycol (PEG 400), and diphenylmethane-4,4′-diisocyanate (MDI) via a one-pot method. The TASNPU30 material not only exhibits discoloration and programmable behaviors under thermal stimulation, but also shows good humidity-stimulated deformation movement as well as excellent self-healing abilities. We hope that such a TASNPU30 system will provide an effective strategy for designing multi-functional actuators and pave a new avenue for the development of biomimetic responsive devices.

Encapsulating immobilized ureolytic bacteria yields self-healing concrete apropos sustainable transportation materials: A review

Transportation networks must be resilient to withstand the effects of climate change and natural calamities. Concrete infrastructure must endure extreme weather, flooding, and seismic catastrophes better than many other types of construction to guarantee the sustainability of transportation services. Self-healing concrete is unquestionably the material of the future that could address these issues. Researchers have discovered a self-healing process in automatic repairing the concrete cracks up to 1.8 mm width. This is made possible by ureolytic and non-ureolytic microorganisms from Bacillus family that cause bacterial precipitation and production of calcite that seal cracks, which could extend the serviceability of concrete. Concrete structures can be restored, and damage prevented through different self-healing mechanisms, such as microvascular healing, bacterial healing, capsule-based healing, and autogenous repair. Research reveals that concrete's capacity to repair itself is greatly enhanced by a mixture of self-healing mechanisms. Moreover, the encapsulation of immobilized bacteria with expanded clay, calcium alginate beads, or other porous materials that can hold onto nutrients and bacteria for an extended period resulted in a considerable improvement in the healing ratio. The main objective of this study is to enumerate all the potential challenges and limitations of the recent studies in self-healing concrete to draw a viable conclusion which is necessary for establishing rules and testing procedures for up-scale implementation.

Evaluating the Efficacy and Safety Profile of Good Morning™ Constipation Drops in a Loperamide-Induced Rat Model

Introduction: Constipation is a prevalent gastrointestinal condition globally, often managed with conventional laxatives that may cause side effects and dependency. Homeopathy, offering a holistic approach through diluted natural substances, aims to stimulate the body's self-healing mechanism. This study evaluates Good Morning™ drops, an innovative homeopathic formulation designed to safely and effectively manage constipation. Using a rat model of Loperamide-induced constipation, we evaluated its safety and efficacy, unveiling promising results.Materials and Methods: A rat model of Loperamide induced constipation was utilized to assess the efficacy and safety of Good Morning™ Constipation Drops. 3 unique formulations were prepared and employed to the animal model in 3 different doses. 72 rats were randomly assigned to 12 groups (3 control groups plus 3 formulations in 3 different doses totalling 9 groups), receiving specific variants or control treatments over the period of 21 days. Parameters including body weight, water intake, stool count, intestinal function, haematology, bleeding and clotting time, blood biochemistry, and organ weight were evaluated. Results and discussion: The results showed that all homeopathic formulations, particularly Variant 2, exhibited significant effects in Loperamide induced constipated rats. Across various parameters, Variant 2 consistently influenced food intake, stool characteristics, and small intestine motility. Safety assessments indicated overall well-being, withVariant 2 demonstrating superior survival outcomes. These findings position Variant 2 as a promising candidate for constipation management, emphasizing its consistent efficacy and safety in the rat model. Conclusion: In conclusion, Good Morning™ Constipation Drops exhibited a promising blend of safety, efficacy, and a multifaceted mechanism of action. The formulation, rich in botanical ingredients, demonstrates high safety with favorable survival rates. Efficacy is evident in improved stool counts, stool weights, Small Intestine Transition percentages, and impacts on lipid profiles and liver enzymes, highlighting its potential as a comprehensive solution for constipation relief.

Evaluation on the fatigue and self-healing properties of aged and rejuvenated SBS-modified asphalt

To investigate the fatigue and self-healing properties of aged and rejuvenated SBS-modified asphalt, soybean oil (SBO), epoxidized soybean oil (ESO), and commercial rejuvenators (LBS) were selected as asphalt rejuvenators. The fatigue performance of the asphalt was assessed through a time sweep procedure using a dynamic shear rheometer (DSR) instrument. Subsequently, a series of fatigue-healing-fatigue tests were conducted with varying healing times and damage degrees to analyze the self-healing characteristics of the asphalt. The rejuvenation and self-healing mechanisms were elucidated through a fluorescence microscope, Fourier transform infrared spectroscopy (FTIR), and thin-layer chromatography with flame ionization detection (TLC-FID) tests. The results revealed that the fatigue life of aged SBS asphalt deteriorated by more than 17% compared to unaged asphalt, and the self-healing properties were also weakened. However, both the fatigue life and self-healing properties could be significantly restored through the addition of rejuvenators, with SBO exhibiting the most pronounced effect in their restoration, followed by LBS and ESO. Furthermore, the self-healing capacity of the asphalt was notably affected by both the healing time and damage degree. Microstructure test results showed that in aged SBS-modified asphalt, lighter components dissipated, and the polymer deteriorated, contributing to the decline in self-healing performance. The presence of a substantial quantity of lightweight components in SBO expedited wetting and molecular diffusion at the damaged interface within the asphalt, thereby restoring the self-healing properties of the aged asphalt.

Reliability analysis for systems with self-healing mechanism in degradation-shock dependence processes with changing degradation rate

Reliability analysis for systems with self-healing mechanism in degradation-shock dependence processes with changing degradation rate

Bioinspired self-healing nickel coating.

We present a study of self-healing mechanisms including their kinetics and thermodynamics in nickel coatings. The bioinspired self-healing coating is designed to enhance the durability of structural metal components exposed to harsh conditions. Microcapsules, reminiscent of natural healing reservoirs, were synthesized via in situ polymerization in an oil-in-water emulsion to encapsulate linseed oil, a healing agent, within poly(urea-formaldehyde) (PUF) shells. Nickel coatings incorporating PUF shell microcapsules were electrodeposited on mild steel substrates to assess their effectiveness in self-healing, mimicking nature's ability to provide on-demand healing. Comprehensive characterization of the microcapsules and coating was performed using techniques including Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and Thermogravimetric Analysis (TGA). The self-healing performance of the coating was evaluated using SEM and EDS after scratches simulating damage were made on the surfaces of the samples. Corrosion resistance and self-healing ability were evaluated through an immersion test, and additional corrosion resistance tests such as Open Circuit Potential (OCP) and Linear Polarization (LP) were conducted. The results indicate that the nickel coating containing PUF shell microcapsules confers corrosion resistance to the substrate and, upon damage to that coating, induces a self-healing response analogous to natural systems, highlighting the potential of bioinspired designs in advanced material solutions.

Study on self-healing mechanism of magnetic nano-powders functionalized fiber reinforced thermoplastic composites

At present, a variety of methods have been developed to realize the self-healing function of fiber-reinforced composites. However, the intrinsic mechanism of material damage recognition and self-healing initiation still lacks systematic research. In this paper, GF/(FeNip/PP) composites with multistage structures were prepared to study the self-healing properties and the mechanism of fiber-reinforced thermoplastic composites. The addition of a small amount of FeNip without affecting the melting peak temperature of the PP matrix (i.e., without reducing the use temperature of PP) can increase the electromagnetic loss (tanδ) of the composites by about 40% and the thermal conductivity by 36%. The cyclic stretching times of GF/(FeNip/PP) composites after microwave healing are doubled at 50% to 60%σmax load. It is indicated that FeNip endows the GF/PP composites with good microwave healing performance, and the purposeful repair can effectively extend the service life of the material. In addition, the self-healing mechanism of GF/(FeNip/PP) composites is discussed in detail from the aspects of microstructure change, multiphase interface effect, entropy enthalpy effect, starting and ending of self-healing procedures, etc. The magnetothermal effect, “entropy consumption” effect, and polymer chain diffusion are the fundamental reasons for the self-healing function of fiber reinforced thermoplastic composites.

Perovskite-based detector for reactor dosimetry monitoring

Hybrid halide perovskites have demonstrated significant efficiency in detecting a broad spectrum of high-energy radiation, including X-rays, gamma rays (γ-rays), and neutrons. Given the common occurrence of mixed radiation fields, we investigated the performance of a perovskite-based detector in a neutron-gamma mixed field. A large methylammonium lead tribromide (MAPbBr3) single crystal (SC) was synthesized via the oriented crystal-crystal intergrowth method. This SC was used to fabricate a gamma detector with carbon electrodes, which was tested in the CROCUS zero-power reactor cavity. The detector’s photocurrent response exhibited a strong correlation with known gamma dose rates, as measured by an ambient Berthold LB 112 gamma probe, facilitating the accurate conversion of photocurrent to dose rate. Notably, the device did not exhibit degradation under neutron radiation exposure. To further assess the impact of neutrons, X-ray diffraction and electron paramagnetic resonance analyses were performed on small MAPbBr3 SCs grown by inverse temperature crystallization. These SCs were irradiated within the CROCUS reactor core and by a Pu-Be neutron source at liquid nitrogen temperature. Our findings indicate that the perovskite material can withstand the nominal in-core operation conditions of the CROCUS reactor. Additionally, it endures irradiation at liquid nitrogen temperature, corresponding to a fast neutron fluence of approximately 1010 cm-2 and a gamma radiation dose of about 50 Gy, confirming only the temporary creation of defects. No signs of long-term deterioration were observed, suggesting a potential self-healing mechanism. This resilience positions perovskite SCs as viable candidates for in-core radiation detection, supporting the further development of miniaturized MAPbBr3 SC devices for such applications.

Data center temperature prediction and management based on a Two-stage self-healing model

While providing efficient and convenient cloud services, data center also brings great pressure to energy consumption and environment. The rise of server temperature not only increases the refrigeration cost, but also seriously affects the operation safety of the data center. Effective analysis and prediction of data center temperature is not only conducive to preventing server overheating and shutdown, but also crucial to data center task scheduling, resource allocation optimization and energy efficiency improvement of data center. Therefore, this article proposes a Two-stage Gated Recurrent Unit (GRU) temperature prediction algorithm with self-healing mechanism. The algorithm establishes a prediction model for the important parameters affecting temperature prediction - CPU utilization, and takes the output of the model as the input parameter of the server temperature prediction model, which fits the changes of each parameter more accurate. To avoid the decrease in prediction accuracy caused by new operating conditions that have not been learned before and changes in physical environmental factors during the operation of the model, a self-healing mechanism is proposed to ensure the prediction accuracy of the model. Experiments show that our prediction model can accurately predict the inlet temperature evolution of the server with dynamic workload. It reduces the prediction error (RSME) to 0.280, and the average prediction temperature difference is only 0.675, which is 10 % higher than the single stage prediction accuracy. The use of Two-stage prediction methods in other machine learning methods can also improve prediction accuracy. Based on the prediction model, this paper proposes a task scheduling algorithm that minimizes temperature difference. The algorithm can make the temperature between servers more balanced after task allocation, effectively reducing the number of servers running at high and low temperatures in the data center, avoiding refrigeration waste, and achieving energy conservation in the data center.

Water-Triggered Self-Healing of Ti3C2Tx MXene Standalone Electrodes: Systematic Examination of Factors Affecting the Healing Process.

MXenes, with their remarkable attributes, stand at the forefront of diverse applications. However, the challenge remains in sustaining their performance, especially concerning Ti3C2Tx MXene electrodes. Current self-healing techniques, although promising, often rely heavily on adjacent organic materials. This study illuminates a pioneering water-initiated self-healing mechanism tailored specifically for standalone MXene electrodes. Here, both water and select organic solvents seamlessly mend impaired regions. Comprehensive evaluations around solvent types, thermal conditions, and substrate nuances underline water's unmatched healing efficacy, attributed to its innate ability to forge enduring hydrogen bonds with MXenes. Optimal healing environments range from ambient conditions to a modest 50°C. Notably, on substrates rich in hydroxyl groups, the healing efficiency remains consistently high. The proposed healing mechanism encompasses hydrogen bonding formation, capillary action-induced expansion of interlayer spacing, solvent lubrication, Gibbs free energy minimizing MXene nanosheet rearrangement, and solvent evaporation-triggered MXene layer recombination. MXenes' resilience is further showcased by their electrical revival from profound damages, culminating in the crafting of Joule-heated circuits and heaters.

The novel damage-reporting and self-healing coatings prepared by electrospinning technology based on AIE agents and photothermal shape memory polymer

The self-healing coatings for metals aroused researchers' interest due to their spontaneous repair of coating damage. In this study, intelligent damage-reporting and self-healing anti-corrosion coatings were developed using electrospun fiber as the core functional materials. The fibers exhibited core–shell structures, with the core materials being the solutions of the composite fluorescence probe RTPE. The shell materials consisted of the photothermal shape memory polymer, namely, phosphotungstic acid modified polyaniline-polyurethane composite polymer. Rhodamine Tetraphenylethylene (RTPE) demonstrated water-triggered aggregation-induced emission (AIE) effects and also exhibited fluorescence response to corrosive factors such as hydrogen ions and iron ions at the damaged area of the coatings. Under the trigger of the infrared laser, the modified polyaniline converted light energy into heat, causing the softening of epoxy and the shape memory effect of polyurethane. These processes facilitated the closure and repair of the damage, thus restoring their anti-corrosion functionality. Phosphotungstic acid played a role in enhancing the photothermal efficiency. The self-healing mechanism reinforced the corrosion resistance of the coatings. The self-indicating feature for damaged areas provided guidance for artificial repair in regions that did not self-heal satisfactorily. The synergistic and intelligent functionalities of the prepared coatings foreshadowed the significant potential applications in marine and aerospace corrosion protection fields.

The application of self-healing concept in Ni superalloys: Theoretical design and experimental validation

The self-healing mechanism has been newly applied in Ni superalloys to extend the creep lifetime during service. Quantitative selection criteria are proposed to screen the potential self-healing elements in Ni alloying system. Ti atoms and η-Ni3Ti precipitates are thus selected as the candidate healing atoms and the healing agent, respectively. The ideal composition interval for Ti to achieve the effective healing effects is computationally calculated as 0.076–0.1 mol fraction. On this basis, SHNi (self-healing Ni alloy) has been developed and compared with nSHNi (no self-healing Ni alloy). The creep lifetimes of SHNi alloys are observed 8–10 times higher than that of nSHNi alloys. Microstructure characterizations have shown that η-Ni3Ti healing agents in SHNi alloys can form site-specifically at the cavity sites during service. Meanwhile, the creep cavities in SHNi alloys present much smaller average sizes during creep, and the cavity growth rates are generally one magnitude lower compared to that of nSHNi alloys. The excellent creep properties of SHNi alloys can be well ascribed to their creep cavitation resistance brought by the self-healing behavior. The effectiveness of self-healing mechanism in improving the creep properties has proposed a new strategy in developing novel Ni superalloys.

Review on aviation intelligent self-healing anti-corrosion coating

Purpose This paper aims to focus on the research progress of intelligent self-healing anti-corrosion coatings in the aviation field in the past few years. The paper provides certain literature review supports and development direction suggestions for future research on intelligent self-healing coatings in aviation. Design/methodology/approach This mini-review uses a systematic literature review process to provide a comprehensive and up-to-date review of intelligent self-healing anti-corrosion coatings that have been researched and applied in the field of aviation in recent years. In total, 64 articles published in journals in this field in the last few years were analysed in this paper. Findings The authors conclude that the incorporation of multiple external stimulus-response mechanisms makes the coatings smarter in addition to their original self-healing corrosion protection function. In the future, further research is still needed in the research and development of new coating materials, the synergistic release of multiple self-healing mechanisms, coating preparation technology and corrosion monitoring technology. Originality/value To the best of the authors’ knowledge, this is one of the few systematic literature reviews on intelligent self-healing anti-corrosion coatings in aviation. The authors provide a comprehensive overview of the topical issues of such coatings and present their views and opinions by discussing the opportunities and challenges that self-healing coatings will face in future development.

Self-Healing Polymers Designed for Underwater Applications

Polymeric materials have been employed in a wide range of applications in both dry and wet environments. When these materials suffer damage, it becomes crucial to initiate repairs in order to mitigate further losses. The use of self-healing materials emerges as a promising strategy not only to address this issue but also possess the advantage of prolonging the product’s lifespan. Nevertheless, the development of self-healing materials tailored for wet environments presents a set of obstacles and complexities. The review examines the current state of research in the field and highlights the challenges associated with developing self-healing materials that can effectively repair damage in such environments. We discuss the self-healing mechanisms and various polymers that are extensively employed in the advancement of self-healing materials. We study the progress made in the research and development of self-healing materials specifically designed for wet environments. Furthermore, it provides a summary of various applications of self-healing materials in wet environments.

An oxidized dextran-composite self-healing coated magnesium scaffold reduces apoptosis to induce bone regeneration

Self-healing coatings have shown promise in controlling the degradation of scaffolds and addressing coating detachment issues. However, developing a self-healing coating for magnesium (Mg) possessing multiple biological functions in infectious environments remains a significant challenge. In this study, a self-healing coating was developed for magnesium scaffolds using oxidized dextran (OD), 3-aminopropyltriethoxysilane (APTES), and nano-hydroxyapatite (nHA) doped micro-arc oxidation (MHA), named OD-MHA/Mg. The results demonstrated that the OD-MHA coating effectively addresses coating detachment issues and controls the degradation of Mg in an infectious environment through self-healing mechanisms. Furthermore, the OD-MHA/Mg scaffold exhibits antibacterial, antioxidant, and anti-apoptotic properties, it also promotes bone repair by upregulating the expression of osteogenesis genes and proteins. The findings of this study indicate that the OD-MHA coated Mg scaffold possessing multiple biological functions presents a promising approach for addressing infectious bone defects. Additionally, the study showcases the potential of polysaccharides with multiple biological functions in facilitating tissue healing even in challenging environments.

3D Printing of Self-Healing Materials.

This review article presents a comprehensive overview of the latest advances in the field of 3D printable structures with self-healing properties. Three-dimensional printing (3DP) is a versatile technology that enables the rapid manufacturing of complex geometric structures with precision and functionality not previously attainable. However, the application of 3DP technology is still limited by the availability of materials with customizable properties specifically designed for additive manufacturing. The addition of self-healing properties within 3D printed objects is of high interest as it can improve the performance and lifespan of structural components, and even enable the mimicking of living tissues for biomedical applications, such as organs printing. The review will discuss and analyze the most relevant results reported in recent years in the development of self-healing polymeric materials that can be processed via 3D printing. After introducing the chemical and physical self-healing mechanism that can be exploited, the literature review here reported will focus in particular on printability and repairing performances. At last, actual perspective and possible development field will be critically discussed.

Characterizing imbibition and void structure evolution in damaged rock salt under humidity cycling by low-field NMR

The excavation damaged zone (EDZ) of salt cavities for compressed air energy storage (CAES) undergoes daily humidity cycling. This study investigated moisture imbibition and its impact on void structures in differently damaged rock salt in a cyclic humidity environment using periodic low-field nuclear magnetic resonance (NMR) tests. NMR tests were also conducted on centrifuged and saturated specimens to assist with the analysis. Fluid-accessible voids in rock salts encompass mesovoids (2–50 nm) and macrovoids (>50 nm). In the wet stage of the first cycle, imbibition in the mesovoids lagged behind that in the macrovoids, whereas dehydration in the mesovoids was more pronounced and rapid in the subsequent dry stage than in the macrovoids. Throughout the long-term treatment, imbibition persisted, and the macrovoid volume in all three specimens notably decreased, whereas those of the mesovoids slightly increased. Collectively, these effects significantly reduced the fluid-accessible porosity. In our interpretation, the greater viscous force in the mesovoids impeded their imbibition and brine supplementation, resulting in a difference in the tests of the first cycle. The continuous imbibition of brine activated two self-healing mechanisms in the macrovoids: diffusion mass transfer and recrystallization. These mechanisms transformed consecutive macrocracks into isolated voids filled with recrystallized microstructures, effectively transforming macrovoids into mesovoids. In summary, this study characterized the complex imbibition and void structure evolution affected by self-healing mechanisms of rock salt under humidity cycling, offering new insights for evaluating the long-term stability and integrity of CAES salt cavities.