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Dehydration has been a key limiting factor for the operation of conductive hydrogels in practical application. Here, we report self-healable ionic skins that can self-regulate their internal moisture level by capturing extenral moistures via hygroscopic ion-coordinated polymer backbones through antipolyelectrolyte effect. Results show the ionic skin can maintain its mechanical and electrical functions over 16 months in the ambient environment with high stretchability (fracture stretch ∼2216 %) and conductivity (23.5 mS/cm). The moisture self-regulating capability is further demonstrated by repeated exposures to harsh environments such as 200°C heating, freezing, and vacuum drying with recovered conductivity and stretchability. Their reversible ionic and hydrogen bonds also enable self-healing feature as a sample with the fully cut-through damage can restore its conductivity after 24 h at 40 % relative humidity. Utilizing the ionic skin as a building block, self-healing flexible piezoelecret sensors have been constructed to monitor physiological signals. Together with a facile transfer-printing process, a self-powered sensing system with a self-healable supercapacitor and humidity sensor has been successfully demonstrated. These results illustrate broad-ranging possibilities for the ionic skins in applications such as energy storage, wearable sensors, and human-machine interfaces.

Hydrogels endure various dynamic stresses, demanding robust mechanical properties. Despite significant advancements, matching hydrogels’ strength to biological tissues and plastics is often challenging without applying potentially harmful crosslinkers. Using hydrogen bonds as sacrificial bonds offers a promising strategy to produce tough, versatile hydrogels for biomedical and industrial applications. Poly(methacrylic acid) (PMA)/gelatin hydrogels were synthesized by thermally induced free-radical polymerization and crosslinked only by physical bonds, without adding any chemical crosslinker. The addition of gelatin increased the formation of hydrophobic domains in the structure of the hydrogels, which acted as permanent crosslinking points. The increase in PMA and gelatin contents generally led to a lower equilibrium water content (WC), higher thermal stability and better mechanical properties. The values of tensile strength and toughness reached up to 1.44 ± 0.17 MPa and 4.91 ± 0.51 MJ m−3, respectively, while the compressive modulus and strength reached up to 0.75 ± 0.06 MPa and 24.81 ± 5.85 MPa, respectively, with the WC being higher than 50 wt.%. The obtained values for compressive mechanical properties are comparable with super-strong hydrogels reported in the literature. In addition, hydrogels exhibited excellent fatigue resistance and biocompatibility, as well as great shape memory properties, which make them prominent candidates for a wide range of biomedical applications.

Self-healing approaches are increasingly being explored in various fields as a potential method to recover damaged material properties. By self-recovering without external intervention, self-healing techniques emerge as a potential solution to arrest or prevent the development of large strains problems in soils (e.g., landslides) and other ground effects that influence the serviceability of structures (e.g., differential settlement). In this study, a microcapsule-based self-healing sand was developed, and its performance during mixing and compaction, shearing, and recovery of shear strength was demonstrated. The cargo used for sand improvement, a hardening oil, tung oil, was encapsulated in calcium alginate capsules by the ionic gelation method. The surface properties, internal structure, thermal stability and molecular structure of the capsules were evaluated by advanced material characterization techniques. The survivability of capsules during mixing and compaction was assessed by measuring the content of tung oil released into the sand, while their influence on sand shear strength and its recovery was assessed with shear box tests. The results showed that the capsules could rupture due to movement of the sand particles, releasing the tung oil cargo, leading to its hardening and minimizing its strain-softening response and enhancing up to 76% of the sand shear strength (at a normal stress of 10 kPa and capsules content of 4%). This study demonstrates the potential of a capsules-based self-healing system to provide ‘smart’ autonomous soil strength recovery and thus with potential to actively control the large strain behavior of soils. © The Author(s) 2024.

The development of materials with self-healing capabilities has garnered considerable attention due to their potential to enhance the durability and longevity of various engineering and structural applications. In this review, we provide an overview of recent advances in materials with self-healing properties, encompassing polymers, ceramics, metals, and composites. We outline future research directions and potential applications of self-healing materials (SHMs) in diverse fields. This review aims to provide insights into the current state-of-the-art in SHM research and guide future efforts towards the development of innovative and sustainable materials with enhanced self-repair capabilities. Each material type showcases unique self-repair mechanisms tailored to address specific challenges. Furthermore, this review investigates crack healing processes, shedding light on the latest developments in this critical aspect of self-healing materials. Through an extensive exploration of these topics, this review aims to provide a comprehensive understanding of the current landscape and future directions in self-healing materials research.

Today, a significant public health challenge is the global shortage of organs needed for transplantation, with only 10 percent of the demand being met according to the World Health Organization. Moreover, there is a pressing need for new in vitro research models to replace or supplement existing models with ones of better relevance and reliability in human translation. In vitro models with tissue equivalents offer promising alternatives. An emerging solution is to create living tissue that resembles the structure of the body's natural tissues using bioprinting (3Dprinting with bioink). This thesis investigates the potential of utilizing a Schiff-based self-healing hyaluronic acid hydrogel with three different crosslinkers as a bioink, focusing on evaluating its printability attributes to address mentioned challenges. The thesis project involved a comprehensive literature study, which included compiling information from scientific papers to establish the background and theoretical framework. Additionally, insights gained from the literature study, coupled with discussions with experts in the field, were used to develop a laboratory protocol. This protocol served as a structured guide for carrying out all experimental procedures. The practical work was divided into four main categories: coding and designing 3D-construct with computer-aided design (CAD), hydrogel preparation, bioprinting and imaging and microscopic observation. All images were compiled into a result, and the result was analyzed and discussed. It was found that the bioink properties differed between the three hydrogels, adipic acid dihydrazide (ADH), propanediylbishydroxylamine dihydrochloride (PDO) and diaminobutane (DAB). Among them, the ADH hydrogel displayed the most favorable and reliable characteristics. Based on the analysis, a conclusion was drawn that the self-healing hydrogel showed promise for bioprinting applications. However, further testing and modification are necessary to optimize its pr

Engineered cementitious composite (ECC) possesses promising application potential in three aspects including earthquake-resistant or impact-resistant structures, repairing and reinforcement of old infrastructure, and 3D printing of digital construction due to its favorable mechanical properties, durability, and suitable workability. Despite the significant advantages of ECC, the technology still faces certain limitations, such as substantial shrinkage, large carbon emissions, and increased construction expenses. However, the feasibility of expanding ECC's utilization in high-rise building structures, long-span bridges, and urban overpasses can be achieved if the material's lightweight property is realized. This would reduce the requirement for steel bars and the thickness of structures or prefabricated parts, consequently lowering the engineering costs and carbon emissions. In addition, the lightweight characteristic of ECC enhances the performance and application prospects of 3D-printed prefabricated parts due to the reduction of layer deformations. Moreover, the incorporation of porous lightweight materials with an internal curing effect mitigates ECC shrinkage. Consequently, the study of lightweight ECC has the potential to address the current challenges associated with ECC, broaden its application fields, and enhance its value proposition. In Chapter 2, a novel eco-friendly lightweight, high-strength engineered cementitious composite (ELH-ECC) using lightweight sand fines (LSF) and fly ash cenospheres (FAC) was developed based on the theory of micromechanics, dense packing theory and method of performance-driven design. The mechanical properties, microstructures, and micromechanism of ELH-ECC are examined. The results indicate that the accumulation compactness between different particles in ELH-ECC is optimized due to the appropriate particle size range brought by LSF and FAC. LSF and FAC slightly reduced the mechanical strength of ELH-ECC matrix but had a signi

Supplementary cementing materials (SCMs) have proven effective in minimizing alkali-silica reaction (ASR) development. In addition, crystalline admixtures (CAs) have been identified as potential solutions to counteract damage in concrete. However, limited data on this topic is available in the literature. This study investigates the impact of CA on concrete damage and is divided into two phases: 1) the effectiveness of CA in self-healing cracks and restoring the mechanical properties of mechanically damaged concrete; 2) it explores concrete mixtures incorporating a wide range of binder compositions (i.e., general use type cement, silica fume, fly ash, slag and Metakaolin) and chemical admixtures (i.e., commercially available CAs and modified versions) in conditions enabling ASR development. Both phases involve microscopic/mechanical analyses to assess the effects of CA on damage, and comparisons with concrete mixtures without CAs are made. The results reveal that CA enhanced the self-healing of cracks up to 82 % of cracks in cement paste (115 % higher values than concrete mixtures without CA) and restored 69 % of compressive strength. Furthermore, although CAs could change the damage mechanism of ASR, they did not “safely” mitigate it. However, combining SCMs and CAs effectively reduces ASR-induced expansion.

Alkali-activated materials (AAM) are considered as promising alternative to Portland cement, as they can utilize industrial by-products or wastes as precursors and contribute to reducing CO2 emissions. However, poor volume stability, especially in the case of alkali-activated slag (AAS) systems, remains a significant obstacle in their large-scale application. In recent years, internal curing has gained increasing attention and has been introduced into the AAM system. This review paper provides an overview of the mechanism of internal curing, common internal curing agents, with a particular focus on the most promising agent—superabsorbent polymers. It also explores the limitations associated with the AAM systems and the advancements made in the internal curing technique within AAM systems. The introduction of voids by internal curing agents typically has a negative impact on mechanical properties. However, this can be (partially) counteracted by the continuous water release during internal curing which promotes hydration. While the effect of internal curing in reducing autogenous shrinkage of AAM systems has been well-established, the effect on drying shrinkage described in different studies varies widely, with some articles even suggesting a negative impact., SCOPUS: ar.j, info:eu-repo/semantics/published

The huge benefits brought by the use of Ultra High-Performance Fibre-Reinforced Cementitious Composites (UHPFRCCs) include their high “intrinsic” durability, which is guaranteed by (1) the compact microstructure and (2) the positive interaction between stable multiple-cracking response and autogenous self-healing capability. Hence, self-healing capability must be properly characterized addressing different performances, thus providing all the tools for completely exploiting such large potential. Within this context, the need is clear for a well-established protocol for self-healing characterization. To this end, in the framework of the Cost Action CA15202 SARCOS, six Round Robin Tests involving 30 partners all around Europe were launched addressing different materials, spanning from ordinary concrete to UHPFRCC, and employing different self-healing technologies. In this paper, the tailored experimental methodology is presented and discussed for the specific case of autogenous and crystalline-admixture stimulated healing of UHPFRCC, starting from the comparison of the results from seven different laboratories. The methodology is based on chloride penetration and water permeability tests in cracked disks together with flexural tests on small beams. The latter ones are specifically aimed at assessing the flexural performance recovery of UHPFRCCs, which stands as their signature design “parameter” according to the most recent internationally recognized design approaches. This multi-fold test approach allows to address both inherent durability properties, such as through-crack chloride penetration and apparent water permeability, and more structural/mechanical aspects, such as flexural strength and stiffness., SCOPUS: ar.j, info:eu-repo/semantics/inPress

Vascular self-healing concrete (SHC) has great potential to mitigate the environmental impact of the construction industry by increasing the durability of structures. Designing concrete with high initial mechanical properties by searching a specific arrangement of vascular structure is of great importance. Herein, an automatic optimization method is proposed to arrange vascular configuration for minimizing the adverse influence of vascular system through a reinforcement learning (RL) approach. A case study is carried out to optimize a concrete beam with 3 pores (representing a vascular network) positioned in the beam midspan within a design space of 40 possibilities. The optimization is performed by the interaction between RL agent and Abaqus simulation environment with the change of target properties as a reward signal. The results illustrates that the RL approach is able to automatically enhance the vascular arrangement of SHC given the fact that the 3-pore structures that have the maximum target mechanical property (i.e., peak load or fracture energy) are accessed for all of the independent runs. The RL optimization method is capable of identifying the structure with high fracture energy in the new optimization task for 4-pore concrete structure., Materials and Environment

The profound impact of childhood experiences on an individual's mindset, emotional well-being, and transition into adulthood is a compelling problem addressed in this thesis paper titled “Forgiving Childhood Hurt Biblically.” This DMIN action research project is to implement biblical forgiveness as a transformative tool to address the physical, mental, and emotional wounds inflicted by childhood trauma. Adverse childhood experiences (ACEs), marked by early-life toxic stress, establish a foundation for the intergenerational transmission of trauma, significantly affecting the health and lives of adults. Given the vulnerability of childhood, addressing and forgiving the sources of trauma is crucial for effectively reprogramming and renewing the human brain. Furthermore, understanding the impact of family history on an individual's physical and psychological health is essential, as childhood experiences often underlie adult psychological issues. This research highlights the vital role of biblical forgiveness in overcoming hindrances caused by childhood trauma to spiritual, mental, and physical health. The thesis unfolds across five chapters: Chapter One articulates the problem and purpose of the study. Chapter Two provides a robust foundation by exploring relevant literature and theology, highlighting the effects of trauma and the advantages of forgiveness. Chapter Three details the research methodology employed, while Chapter Four analyzes collected quantitative and qualitative data. Chapter Five assesses the data and proposes strategies for further exploration among individuals with adverse childhood experiences. The thesis concludes by summarizing the project and drawing essential implications from this doctoral study, underscoring the transformative potential of biblical forgiveness in healing childhood wounds.

The ingress of chloride ions is a serious threat for concrete structures. Superabsorbent polymers (SAPs) are interesting additions to cementitious systems due to their property of absorbing water during mixing and releasing it at a later time to provide internal curing, thereby reducing shrinkage and promoting durability. In addition, SAPs can improve the regain in impermeability of cracks by swelling and blocking the crack and promoting autogenous healing. The current study investigates the influence of the addition of SAPs without additional mixing water to the chloride ingress in cracked mortar via diffusion and quasi-steady-state migration testing. Filtration tests showed that the charge-screening effect in a NaCl solution is more dominant than for cement filtrate solution during swelling of SAPs. After wet/dry cycling for a month, subsequent chloride diffusion tests with 2 and 6 weeks of exposure showed that the addition of SAPs improved the performance with respect to a reference mix with the same total water-to-cement ratio. A reference mix with the same effective water-to-cement ratio as the SAP mix had a comparable performance to the SAP mix. One set of chloride diffusion experiments showed that the SAP mix was the only one successfully preventing chloride ingress into the deepest zone of the crack. The superior performance of the series with SAPs was also confirmed by migration testing where cracked and healed specimens obtained a migration coefficient which was only 12 % higher than uncracked specimens., SCOPUS: ar.j, info:eu-repo/semantics/inPress

Vascular self-healing concrete (SHC) has great potential to mitigate the environmental impact of the construction industry by increasing the durability of structures. Designing concrete with high initial mechanical properties by searching a specific arrangement of vascular structure is of great importance. Herein, an automatic optimization method is proposed to arrange vascular configuration for minimizing the adverse influence of vascular system through a reinforcement learning (RL) approach. A case study is carried out to optimize a concrete beam with 3 pores (representing a vascular network) positioned in the beam midspan within a design space of 40 possibilities. The optimization is performed by the interaction between RL agent and Abaqus simulation environment with the change of target properties as a reward signal. The results illustrates that the RL approach is able to automatically enhance the vascular arrangement of SHC given the fact that the 3-pore structures that have the maximum target mechanical property (i.e., peak load or fracture energy) are accessed for all of the independent runs. The RL optimization method is capable of identifying the structure with high fracture energy in the new optimization task for 4-pore concrete structure.

In this study, hydrogels were produced using a Schiff base reaction between two hyaluronic acid derivatives: one containing aldehyde groups (HA-Ald) and the other holding a diethylenetriamine with terminal amino groups (HA-DETA). The DETA portion promotes the in situ growth, complexation, and stabilization of silver nanoparticles (AgNPs), eliminating the need for external reducing agents. The reaction between HA-DETA and HA-Ald leads to the formation of imine bonds, which results in dynamically pH-responsive cross-linking. While the DETA capping ability helped in embedding the AgNPs, the on/off pH environmental responsivity of the hydrogel allows for a controlled and on-demand release of the drug, mainly when bacterial infections cause pH variation of the wound bed. The injectable hydrogels resulted in being highly compatible in contact with blood red cells, fibroblasts, and keratinocytes and capable of having a proliferative effect on an in vitro wound scratch model. The pH-responsive hydrogels showed proper antibacterial activity againstPseudomonas aeruginosaandStaphylococcus aureus, common bacterial strains presented in wound infections. Finally, in vivo wound model studies demonstrated an overall speeding up in the wound healing rate and advanced wound conditions in the experimental group treated with the hydrogels compared to control samples.

Current methods for making and disposing synthetic polymers have been widely pursued and are largely unsustainable. As a part of the solution, the reversible nature of dynamic covalent bonds emerges as an extraordinarily diverse and valuable feature in the development of exotic molecules and extended structures. With these bonds, it should be possible to construct recyclable and mechanically interlocked molecular structures using relatively simple precursors with preorganized geometries. A new helicide-based elastomer network is developed here with self-healing, recycling, and degradation features using a similar concept. The best self-healing performance (100%) was noted over 10-20 min, with various H2O, HCl, and NaOH solutions that delivered mechanical properties in the 1-1.4 MPa range. For hydrolytic degradation, the parameters are defined based on the type of binding, the pH of the solutions, and the copolymer network, which endowed a degradation time of approximately 4-11 h for each prepared sample. However, due to the reversible nature of the dynamic bonds, the material showed good recyclable mechanical properties compared to the pristine samples after five consecutive cycles, which meet the requirements of recyclable materials and recyclable packaging., QC 20231031

This document contemplates a critical reflection of the technological advances in biological and chemical tests that concrete is subjected to through the incorporation of bacteria, with the aim of knowing the different microbial elements that have biomineralization properties capable of self-healing in concrete. Likewise, the methods and applications of bacteria in concrete were reviewed in order to improve its mechanical properties to the different demands placed on modern structures, and at the same time contribute to the reduction of gases that are harmful to the environment. In the development of this manuscript, 80 articles indexed between the years 2017 to 2021 were reviewed, distributed as follows, 51 in Scopus, 17 in Ebsco, and 12 in SciencieDirect, pointing out and describing that microbial concrete has a promising approach in the future. Near. The results achieved with the incorporation of the different Bacillus bacteria, such as Bacillus subtillis, B, cohnii, B. pasteurii, B. pseudofirmus, B. megaterium among others, in different concentrations of cells / ml., Showed great effectiveness in the crack healing, also increasing resistance to compression, bending and traction in concrete. Based on the literary review, it is concluded that the microbial precipitation of calcium carbonate by ureolysis in the concrete matrix mitigates cracking, improves strength, increases durability and, therefore, reduces costs in repairing structures., El presente documento contempla una reflexión crítica de los avances tecnológicos en ensayos biológicos y químicos que es sometido el concreto mediante la incorporación de bacterias, con el objetivo de conocer los distintos elementos microbianos que poseen propiedades de biomineralización capaces de realizar la autocuración en el concreto, asimismo, se revisaron métodos y aplicaciones de las bacterias en el concreto con el fin de mejorar sus propiedades mecánicas a las diferentes exigencias sometidas las estructuras modernas, y al mismo tiempo contribuir con la reducción de gases dañinos al medio ambiente. En el desarrollo de este manuscrito se revisaron 80 artículos indexados entre los años 2017 al 2021 distribuidos de la siguiente manera, 51 en Scopus, 17 en Ebsco, y 12 en SciencieDirect, señalando y describiendo que el concreto microbiano tiene un enfoque prometedor en un futuro cercano. Los resultados alcanzados con la incorporación de las diferentes bacterias de Bacillus, como son Bacillus subtillis, B, cohnii, B. pasteurii, B. pseudofirmus, B. megaterium entre otros, en diferentes concentraciones de células/ml., mostraron gran efectividad en la cicatrización de grietas, aumentando también la resistencia a la compresión, flexión y tracción en el concreto. Sobre la base de la revisión literaria se concluye que la precipitación microbiana de carbonato de calcio mediante ureólisis en la matriz del concreto, mitiga el agrietamiento, mejora la resistencia, aumenta la durabilidad y, por lo tanto, disminuye los costes en reparación de las estructuras.

Paints are coatings which serve to both protect surfaces from damage and impart a variety of aesthetic qualities. They are composed of a matrix of interlocking hydrophobic acrylic polymers which constitute the body of the coating, while binding together a myriad of other additives including pigment particles. Paints represent the majority fraction of a vast global coatings market, and, like all coatings, are exposed to a variety of stresses that can lead to long term damage in the form of microcracks. To date, the only method to repair such damage is to simply replace the paint with a new coat, which is expensive and time consuming. Self-healing technology is perhaps the most promising solution to this problem, as it offers the ability to heal damage spontaneously and without external diagnosis. However, neither a self-healing paint, nor any viable self-healing acrylic coating currently exists. The work presented herein represents a 3-and-a-half-year research effort to successfully design both a self-healing acrylic coating and a feasible self-healing paint. The strong quadruple hydrogen bonding unit 2-ureido-4[1H]-pyrimidinone (UPy) was incorporated into an acrylic coating to form a hydrogen bonding network. Upon damage to the coating, the strong attractive forces between the broken UPy units in the network prompted self-healing through polymer rearrangement and the reformation of UPy–UPy bonds. This was achieved first through the design of an UPy functionalized acrylic monomer with a long amphiphilic spacer. This monomer, at a concentration of only 2.5 wt%, was able to successfully imbue a typical acrylic coating with efficient self-healing (~25%) at room temperature. Then, in order to enhance self-healing efficiency, a UPy functionalized crosslinker system with exotic architecture was designed. One crosslinker design in particular successfully enhanced self- healing efficiency by over 10%. Finally, in collaboration with the international paint company DuluxGroup

In response to environmental concerns and restrictions on isocyanate-based materials, researchers and the coatings industry are focused on developing eco-friendly isocyanate-free polyurethanes. This article introduces a novel class of environmentally-friendly, initiator/catalyst-free, UV-curable, self-healing non-isocyanate polyurethanes (NIPUs) synthesized from bio-based carbonated soybean oil (CSO) and non-toxic coumarin. The synthesis of these polymers is based on using a photo-reactive coumarin that undergoes a reversible [2 + 2] cycloaddition upon exposure to the wavelength of UV light. UV-curable three coumarin-terminated isocyanate-free polyurethane prepolymers were synthesized using CSO and three different amines and epoxy coumarin. Subsequently, a set of cross-linked NIPU polymers were obtained with exposure of 365 nm UV irradiation. The photo-reversible nature of these polymers was investigated in response to various wavelengths of UV radiation. Additionally, their self-healing ability and the thermal and mechanical properties of NIPU coatings were studied using optical microscopy, thermogravimetric analysis, differential scanning calorimetry, and a universal testing machine. The outcomes demonstrate that this polyurethane has the potential to provide a sustainable alternative to isocyanate-based materials. Two examples of stimulated healing are given, that of healing a scratch and the other being the healing of a sample that has been mechanically stressed to failure in a tensile mode.

The design of crosslinking domains is a vital factor to create functional hydrogels with controlled physical, mechanical, and adhesive properties. This paper demonstrates versatile synthetic systems of micelle-crosslinked hydrogels with highly stretchable, self-healing, and selectively adhesive properties. For this, methacrylate-bearing random copolymer micelles are designed as physical and covalent crosslink domains via the self-assembly of amphiphilic random copolymers carrying hydrophilic poly(ethylene glycol) (PEG), hydrophobic butyl or dodecyl groups, and methacrylate-terminal PEG in water. The size, aggregation number, and pendant methacrylate number of the micelles are controlled by the composition and degree of polymerization. Hydrogels are efficiently obtained from the free radical polymerization of hydrophilic monomers such as PEG acrylate and acrylamide in the presence of the micelle crosslinkers in water. Owing to the dynamic yet selective chain exchange properties of the micelle domains, the hydrogels are highly stretchable up to over 1000% and show self-healing and selectively adhesive properties. The self-healing of hydrogels is promoted upon heating due to the fast chain exchange of the micelle domains, whereas hydrogels consisting of micelles with different alkyl groups are never adhesive because of their self-sorting properties.

Aluminium alloys produced by additive manufacturing are largely used in aerospace and aeronautical fields where damage may occur due to overloads experienced in service. Instead of replacing damaged parts and producing new one, materials able to heal their damage sites have great potential. This research aims at developing a new high strength healable Al alloy manufactured by Laser Powder Bed Fusion (LPBF). Zr is introduced as an alloying element into an Al-Mg alloy to form a high strength alloy through the formation of strengthening precipitates. An Al matrix surrounded by Mg-rich low melting point eutectic network, similar to a vascular network, composed the microstructure. Once damage nucleates, a healing heat treatment (HHT) with or without additional pressure (Hot Isostatic Pressing) is applied to trigger the melting of the low melting point phase which flows into the voids and seals them during solidification. The influence of the additional pressure on the healing efficiency is studied. In this work, the healing ability of the new Al-Mg-Zr alloy, and the influence of pressure addition during HHT has been characterized in 3D by a correlative X-ray tomography and electron microscopy methodology. The damage regions before and after healing were imaged with a voxel size of 35 nm by X-ray nano-tomography technique at beamline ID16B ESRF. In a second time, according to the ESRF data, a specific sample sub-volume containing the healed damage has been further investigated using PFIB-SEM serial sectioning tomography and TEM analysis combined with EDX elemental material composition analysis.

This paper proposes a bifilar coil numerical analysis for asphalt induction heating. The software utilized in this research was ANSYS Electronics Desktop and ANSYS Transient Analysis. The asphalt has been modified by adding a certain amount of iron flakes. The asphalt containing magnetic substances is modeled and subjected to an electromagnetic field, thus a comparative temperature distribution between bifilar and monofilar coils is achieved. The bifilar coil has a slight increase in output than the monofilar coil under conditions of equal current and frequency. However, bifilar coil provides less power consumption and self-capacitance compared to the counterpart.

A new device and procedure for the in situ quantification of the extent of the self-healing and the kinetics of self-healing of polymeric materials were proposed. The device consisted of flowing an inert gas below the sample placed in a hermetically closed chamber. When the sample was perforated/damaged, the gas passed through the hole made in the polymeric material and the gas flow rate declined as the self-healing was produced. Once the gas flow rate stopped, the self-healing was completed. The proposed method was simple, quick, and reproducible, and several in situ self-healing experiments at different temperatures could be performed in the same sample. As a proof of concept, the new device and method have been used for measuring the self-healing ability of different polyurethanes.

Triboelectric nanogenerators (TENGs) have attracted great interests in the development of sustainable energies and intelligent society. However, a big challenge for TENGs in practical applications is the unavoidable external mechanical abrasion and/or contaminant adsorption on the triboelectric materials, which leads to the significant decrease of the durability of TENGs and is urgently needed to be addressed. There are already a series of interesting progresses on the topic of the TENGs’ durability. In this study, reviewing the durability of TENGs via both the advanced materials/structure designing and the novel surface/interface engineering is focused upon, which includes choosing basic TENG materials, improving composites performance, optimizing structures, and designing triboelectric surfaces and interfaces. To get a better understanding of the durability of TENGs in published studies, the quantifiable levels of service life are also summarized including operation cycles, time, friction coefficient, and wear loss of triboelectric materials, where the boosting mechanisms are also discussed and summarized. Finally, the challenges as well as key strategies toward high durable TENGs are presented., Validerad;2023;Nivå 2;2023-04-18 (joosat);Funder: National Natural Science Foundation of China (52275170, 51905027)Licens fulltext: CC BY License

Technological advancements in electronic device scaling has led to the use of smaller spacecraft that can travel at higher speeds and lower costs associated with launch weight and propulsion. Traditional counter-radiation methods for space electronics involve hardened chip designs that negate the benefits of using smaller, lighter spacecraft. A self-healing counter-radiation approach, using a micro-heater to thermally anneal commercial-off-the-shelf (COTS) chips, is an attractive alternative due to performance enhancement and reduced cost and weight. In this research, the degradation of COTS transistors via gamma radiation and their subsequent recovery in the laboratory is experimentally proven. Through an iterative process, an annealing protocol is developed that successfully recovered damaged bipolar junction transistors (BJT) exposed to 5–10 Mrad radiation doses in approximately two hours at 200°C. Additionally, finite element modeling is used to create an annealing micro-heater, adjust heater parameters to optimize performance, and explore heater integration with a ceramic chip package, lid, and transistor. The annealing protocol and model results in this research provide the foundation for future self-healing efforts using more complex electronics, such as logic units. Furthermore, this research can serve to enhance the robustness of space electronics for future space missions executed by the DOD and subordinate organizations, such as the U.S. Space Force., DoD Space, Captain, United States Army, Approved for public release. Distribution is unlimited.

The need for exceptional grid reliability and resiliency has become ever more important with the increasing dependence on electrical power in the digital age and more frequent and severe weather events resulting in a disturbance in power delivery. Using on-site energy sources, microgrids have been proven to enhance the reliability and resiliency of critical loads and overall protection during grid outages. With the focused attention on microgrid implementation, this dissertation addresses achieving high reliability and resiliency for two distinct applications: (1) a classic microgrid, and (2) utility distribution feeders operated as a microgrid, both of which are modeled with an IEEE 2030.7 compliant microgrid controller enhanced with self-healing capabilities. The University of California Irvine Microgrid serves as the classic microgrid, and two 12kV circuit feeders at the Southern California Edison 66kV MacArthur substation serve as utility distribution feeder microgrids.The study first enhances and tests the self-healing capabilities of the controller. Second, the efficacy of the enhanced controller is tested for the classic microgrid to assess the impact on reliability and resiliency while islanded, including the utility of battery electric buses as a resiliency attribute during islanded operations. Third, the of the concept of managing utility distribution feeders is assessed in terms of energy sustainability, restoration, and energization with various distributed energy resources within the system including a fuel cell generator, demand response, and vehicle-to-grid energy support. The results show that (1) the reliability and resiliency of critical loads can be enhanced by interconnected circuits with rapidly dispatched switching, (2) firm power generation in combination with demand response are essential in supporting an islanded microgrid, and (3) plug-in electric vehicles including battery electric buses can both enhance resiliency and serve as a flexible

The production and engineering of sustainable materials through green chemistry will have a major role in our mission of transitioning to a more sustainable society. Here, combined catalysis, which is the integration of two or more catalytic cycles or activation modes, provides innovative chemical reactions and material properties efficiently, whereas the single catalytic cycle or activation mode alone fails in promoting a successful reaction. Polyphenolic lignin with its distinctive structural functions acts as an important template to create materials with versatile properties, such as being tough, antimicrobial, self-healing, adhesive, and environmentally adaptable. Sustainable lignin-based materials are generated by merging the catalytic cycle of the quinone-catechol redox reaction with free radical polymerization or oxidative decarboxylation reaction, which explores a wide range of metallic nanoparticles and metal ions as the catalysts. In this review, we present the recent work on engineering lignin-based multifunctional materials devised through combined catalysis. Despite the fruitful employment of this concept to material design and the fact that engineering has provided multifaceted materials able to solve a broad spectrum of challenges, we envision further exploration and expansion of this important concept in material science beyond the catalytic processes mentioned above. This could be accomplished by taking inspiration from organic synthesis where this concept has been successfully developed and implemented., QC 20230704

Cracks are one of the most common expressions of damage in masonry structures. Aside from aesthetic issues, they can compromise the overall behaviour of the structure; therefore, they are undesirable and need to be repaired. The repointing technique is traditionally implemented in this context, especially in historical masonry. Nevertheless, future damage is not prevented and may arise again, thus requiring renewed repointing interventions. The paper describes a preliminary study conducted at Delft University of Technology to investigate the applicability of the innovative self-healing technology to enable an automatic repair of masonry cracks. A bacteria-based self-healing mortar, developed to repair existing concrete structures, was implemented to explore the capacity of couplets to recover their original strength and aesthetic aspect after multiple damaging events. Specimens built with calcium-silicate and clay bricks were subjected to subsequent cracking cycles using a crack-mouth-opening-displacement controlled bond-wrench test. Experimental results showed that self-repair, in terms of strength restoration and aesthetic filling of cracks, occurs even after multiple cracking cycles when the self-healing mortar is used with both types of bricks, optimizing the autogenous healing of cement-based mortars. In this context, the healing effectiveness tended to decrease as the crack width and the number of cycles increased. The effectiveness varied also according to the types of brick and healing environment used, e.g. under humid conditions (RH ~ 95%), 50% vs 80% of the original capacity was regained in fully separated couplets made respectively with clay and calcium-silicate bricks. This outcome provides the ground to delineate the remaining testing campaign., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Applied Mechanics

(English) Nowadays, distributed energy resources are widely used to supply demand in micro grids especially in green buildings. These resources are usually connected by using power electronic converters, which act as actuators, to the system and make it possible to inject desired active and reactive power, as determined by smart controllers. The overall performance of a converter in such system depends on the stability and robustness of the control techniques. This thesis presents two bottom­up smart control approaches to manage energy in DC microgrids (MG) that split the demand among several generators. Firstly, an energy management system (EMS) based on multi-agent system (MAS) controllers is developed to manage energy, control the '.

Self-healing cementitious composites including superabsorbent polymers (SAPs) have been studied as an alternative to costly, labour-intensive repairs. Whereas the assessment of the healing ability can be performed through a variety of testing methodologies, an in-situ evaluation requires the adoption of a non-destructive technique in order to maintain the present infrastructure. Additionally, the assessment method should be easily applicable for reasons of time efficiency. Thanks to their sensitivity to the elastic properties, ultrasonic waves have enabled the evaluation of the regained mechanical performance, without interfering with the microstructure. While coupled ultrasonic measurements are an established procedure, the use of air-coupled ultrasound provides the advantage of omitting the transducers’ coupling. As the coupling is a time-consuming task and imposes a certain variability between performed measurements, the adoption of air-coupled ultrasound would lead to a significant improvement of the evaluation method. Therefore, a comparison between both techniques using various mortar mixtures was performed., SCOPUS: ar.j, info:eu-repo/semantics/inPress

Self-healing concrete has great potential to enhance the durability of concrete structures without significantly increasing the initial costs. Among the self-healing approaches, vascular self-healing cementitious composite is capable of supplying healing agents to the cracked region in a continuous way or multiple times. However, the use of brittle materials as vascular makes it difficult to create vascular networks with complicated geometry. The recent development of additive manufacturing (AM, also known as 3D printing) promotes the fabrication of complicated vascular system for vascular self-healing materials. However, the application of AM in vascular self-healing cementitious materials is relatively rare. Therefore, this study focuses on understanding the behavior of 3D-printed vascular self-healing concrete with different printing parameters or vascular configurations....., Materials and Environment

The interaction of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) with the AA2024-T3 local microstructure (S-phase, secondary phases and matrix) as function of the NaCl concentration is studied. The inhibiting power and the local interaction of DMTD with the metal were studied by in–situ opto-electrochemistry, XPS and Raman spectroscopy. The stability of the inhibiting layers was evaluated by re-exposing the samples to NaCl solutions without inhibitor. The amount of DMTD and its interaction state (chemisorption/physisorption) vary with the local microstructural composition and NaCl concentration. Higher stability of the inhibiting layers is obtained when these are formed in presence of small amounts of NaCl (0.025–0.25 M)., Novel Aerospace Materials, ChemE/Product and Process Engineering

Direct ink writing of cementitious materials can be an alternative way for creating vascular self-healing concrete by intentionally incorporating hollow channels in the cementitious matrix. In this study, a 3D-printable fibre reinforced mortar was first developed. Three groups of specimens were fabricated using direct ink writing, where the two top and bottom printing layers were printed with different printing directions. The macrostructure of the hardened specimens was studied using CT scanning. Four-point bending tests were carried out to investigate the initial flexural strength and the strength recovery after healing with injected epoxy resin. Furthermore, water permeability test was used to evaluate the healing potential of the samples. The results from CT scanning show that printing direction influences the actual volumes of hollow channels and the volume of small pores which are a consequence of the deposition process. The hollow channels of all samples were squeezed by the upper layers during the printing process, and the longitudinally printed samples were the most affected. When printing direction changes from longitudinal to transverse, the initial flexural strength decreases. Similarly, the average permeability of the cracked samples increases when the printing direction changes from longitudinal to transverse. Although the healing effectiveness regarding flexural strength is remarkable for all specimens, it was only possible to perform a single healing process as hollow channels were then blocked by the epoxy resin. The rough surface of the hollow channels is inferred to make it difficult to extract the epoxy resin out of the specimens., Materials and Environment

This paper describes the development of a discrete lattice model for simulating structures formed from self-healing cementitious materials. In particular, a new approach is presented for simulating time dependent mechanical healing in lattice elements. The proposed formulation is designed to simulate the transient damage and healing behaviour of structures under a range of loading conditions. In addition, multiple and overlapping damage and healing events are considered. An illustrative example demonstrates the effects of varying the healing agent curing parameters on the computed mechanical response. The model is successfully validated using published experimental data from two series of tests on structural elements with an embedded autonomic self-healing system. The meso-scale model gives detailed information on the size and disposition of cracking and healing zones throughout an analysis time history. The model also provides an accurate means of determining the volume of healing agent required to achieve healing for all locations within a structural element. The importance of the information provided by the model for the design of self-healing cementitious material elements is highlighted., Materials and Environment

The ongoing energy crisis and increasing consumption of fossil-based feedstock have raised the awareness of researchers about the need to develop sustainable alternatives for conventional plastic materials. A great potential is attributed to vitrimers, a newly emerging class of polymer materials that, despite being covalently cross-linked, can be easily repaired, reprocessed, or recycled with minimal environmental impact. Such properties are achieved due to dynamic cross-links that enable the reversible reactions within their network structure. Here, we report on the development of a novel bio-based magnetic composite by adopting the catalyst-free vitrimer as a host matrix for embedding the magnetic micro-filler. The employed matrix uses a recent generation of the exchange reactions ensured by boronic ester metathesis, following the principles of “green” chemistry. The final composite is endowed with various useful, programmable, and unique features, such as hardening in magnetic fields, electromagnetic shielding capability, and directional self-healing capability, while also being reprocessable multiple times and easily recyclable.

For the ferritic self-healing (FSH) steel, it remains challenging to solve the low healing efficiency problem, due to the mismatch between the formation kinetics of creep cavities and the precipitation kinetics of healing agents. In this research, an offline healing treatment has been proposed to stimulate the formation of the Laves phase precipitates as self-healing agents to retard creep cavity growth at elevated temperatures. The corresponding treatment parameters were determined by the precipitation behaviors of Laves phases on the external free surfaces and internal cavity surfaces of FSH steels. Results have shown that the creep lifetime of the offline healing treated samples can be extended more than 30% compared to that of non-healed sample, while the creep rates can be reduced by one order of magnitude. The formation kinetics of Laves phases and creep cavities have been quantitatively analyzed. It was found that after the offline healing treatments, the average cavity sizes of the samples decreased significantly, while the growth rates of creep cavities rather than the nucleation kinetics are compensated by the healing phenomena of Laves phase formation. The relationship between the extended lifetime and filling ratios of creep cavities by the healing agents was established as well. The demonstrated potential of offline healing treatments provides a new strategy to cultivate the self-healing capabilities of heat resistant steels.

This research work studies the self-healing ability, mechanical properties, and shape memory of the polymer Surlyn® 8940 with and without multiwall carbon nanotubes (MWCNTs) as a nanoreinforcement. This polymer comes from a partially neutralized poly(ethylene-co-methacrylic acid) (EMAA) ionomer copolymer. MWCNTs and the polymer went through a mixing process aimed at achieving an excellent dispersion. Later, an optimized extrusion method was used to produce a uniform reinforced filament, which was the input for the 3D-printing process that was used to create the final test samples. Various concentrations of MWCNTs (0.0, 0.1, 0.5, and 1.0 wt.%) were used to evaluate and compare the mechanical properties, self-healing ability, and shape memory of unreinforced and nanoreinforced materials. Results show an enhancement of the mechanical properties and self-healing ability through the addition of MWCNTs to the matrix of polymer, and the specimens showed shape memory events.

Among the ways to counter the effects of concrete cracking, self-healing appears to be very promising. This research aims to appraise the effect of autogenous and autonomous self-healing on the condition recovery of mechanically loaded concrete specimens proportioned with distinct raw materials. A commercially available crystalline admixture (CA), different types of SCMs, and chemically modified versions of CA were combined with cement to proportion distinct mixtures. Ninety-six specimens from each mixture were manufactured and cured for 28 and 180 days at 20 °C and 100 % RH, after which they were pre-loaded using up to 90 % of their corresponding compressive strength and restored at the same curing conditions for 90 days. Non-destructive, microscopic, and mechanical test procedures were conducted on the samples after the secondary curing; results indicate that SCMs enhanced the natural healing. However, mixtures to which CA was added demonstrated the highest healing ratios, indicating promising recovery of mechanical properties.