Self-healing Approach Research Articles

Self-Healing Polymer Nanocomposite Materials by Joule Effect.

Nowadays, the self-healing approach in materials science mainly relies on functionalized polymers used as matrices in nanocomposites. Through different physicochemical pathways and stimuli, these materials can undergo self-repairing mechanisms that represent a great advantage to prolonging materials service-life, thus avoiding early disposal. Particularly, the use of the Joule effect as an external stimulus for self-healing in conductive nanocomposites is under-reported in the literature. However, it is of particular importance because it incorporates nanofillers with tunable features thus producing multifunctional materials. The aim of this review is the comprehensive analysis of conductive polymer nanocomposites presenting reversible dynamic bonds and their energetical activation to perform self-healing through the Joule effect.

The ecology of medical care in Shanghai

BackgroundTo better understand the distribution and consumption patterns of resources in different ethnic groups and at different levels of economic development, this paper chose to describe the healthcare seeking behavior in Shanghai.MethodsThe data are from the Sixth Health Service Survey of Shanghai, which encompasses 23,198 permanent residents. Descriptive analyses were conducted to estimate the number of patients who reported health-related symptoms and healthcare-seeking behaviors per 1,000 residents. Logistic regression analyses were conducted to examine differences in reporting health-related symptoms and healthcare-seeking behaviors by age, gender and area of residence.ResultsThis paper have mapped the ecology of healthcare in Shanghai in 2018. Of 1000 individuals considered during a 1-month period, 444 reported sickness, 433 received treatment, 288 went to medical institutions, 195 went to primary medical institutions, 86 took a self-healing approach, 26 received TCM services, 7 were hospitalized, and 3 underwent surgery.ConclusionsAge is a risk factor leading to disease, medical treatment, self-medication, medical institution visits, TCM service, hospitalization and surgery. But age is a protective factor in the use of primary health care services. By gender, the number of people receiving medical services was similar, but women were statistically more likely to have surgery. As the income level increased, the number of patients and people receiving medical services showed a decreasing trend. Compared with the local population, the probability of non-local people visiting medical institutions was lower and statistically significant. Compared with the people who had health insurance, fewer uninsured people reported sickness and utilized healthcare services.

Self-Healing Router Approach for High-Performance Network-on-Chip

Network-on-Chip (NoC) is used as the communication network in many applications that use multiple cores or Processing Elements (PEs). Routers play a crucial role as connectors since a faulty router can degrade the NoC’s performance and cause miscommunication between the network’s components. Thus a faulty router may cause the system to fail. To avoid failure in routers in NoCs, a novel self-healing technique is proposed. Self-healing serves to recover hardware faults, and it is defined as the ability of a system to recover from its faults without any external intervention. The proposed self-healing method is to heal faulty routers and their port buffers of faults as they occur. The proposed method uses the neighboring routers of a faulty router for computation. The data packet includes three bits for routing. A neighbor’s active router updates these bits according to the destination of the packet. A self-healing block is added inside each router. The proposed method also covers faulty buffers, and it uses active buffers to store the packet of a faulty one. It has been implemented and tested using VHDL and Altera Arria 10 GX FPGA. It has been found to attain improved reliability and Mean Time to Failure (MTTF) at an area overhead of 27%. It has been tested for complex NoC structure, and the results show it is practical, scalable, stable, and robust.

A decentralised self-healing approach for network topology maintenance

In many distributed systems, from cloud to sensor networks, different configurations impact system performance, while strongly depending on the network topology. Hence, topological changes may entail costly reconfiguration and optimisation processes. This paper proposes a multi-agent solution for recovering networks from node failures. To preserve the network topology, the proposed approach relies on local information about the network's structure, which is collected and disseminated at runtime. The paper studies two strategies for distributing topological data: one based on Mobile Agents (our proposal) and the other based on Trickle (a reference gossiping protocol from the literature). These two strategies were adapted for our self-healing approach to collect topological information for recovering the network; and were evaluated in terms of resource overheads. Experimental results show that both variants can recover the network topology, up to a certain node failure rate, which depends on the network topology. At the same time, Mobile Agents collect less information, focusing on local dissemination, which suffices for network recovery. This entails less bandwidth overheads than when Trickle is used. Still, Mobile Agents utilise more memory and exchange more messages, during data-collection, than Trickle does. These results validate the viability of the proposed self-healing solution, offering two variant implementations with diverse performance characteristics, which may suit different application domains.

Dual-action self-healing protective coatings with photothermal responsive corrosion inhibitor nanocontainers

This work introduces a novel nanocomposite coating with dual-action self-healing corrosion protection activated by the photothermal response of plasmonic titanium nitride nanoparticles (TiN NPs). TiN@mesoporous SiO2 core–shell nanocontainers were developed as reservoirs for benzotriazole (BTA) corrosion inhibitors and incorporated into the shape memory epoxy coating matrix. Under near-infrared (NIR) light irradiation, the thermogenesis effect of TiN could not only promote the release of corrosion inhibitors from nanocontainers into the crevice, but also trigger the shape memory effect of damaged epoxy to merge the coating scratch. As such, the dual-action self-healing mechanisms combining the formation of an inhibitor-based protective layer and the scratch closure efficiently suppressed the corrosion process at the exposed metal surface. Surface characterization and electrochemical measurement results proved that the nanocomposite coating incorporated with 2 wt% of TiN-BTA@SiO2 exhibited the optimal corrosion protection as well as an excellent self-healing performance that can be initiated within 30 s of NIR illumination. This photo-controlled self-healing approach is potentially useful in designing next-generation self-healing coatings with ultrafast response time and high healing efficiency.

Energy management system of networked microgrids through optimal reliability-oriented day-ahead self-healing scheduling

Abstract This paper proposes a day-ahead self-healing scheduling approach in isolated networked microgrid (NMG) systems. The proposed approach is based on a two-level flexible energy management system (EMS). The upper-level EMS is responsible for optimal scheduling of the normal-operated MGs, while the lower-level help the MGs for operating on-fault in self-healing and islanded modes. When a fault occurs in an MG, it divides the on-fault MG into two zones. The grid-connected zone receives power support from the other normal-operated MGs. Furthermore, a secure optimization problem is presented to operate the separated zone in an islanded operation. The proposed approach is implemented on a test system with five NMGs. To cope with the operational uncertainties, a stochastic programming approach is applied. The simulation is run over a 24-hour scheduling time horizon. The results of the simulations in the normal, self-healing, and islanded operation modes for normal-operated and on-faulted MGs in cases without and with DRP are presented. The results reveal the effectiveness of the proposed stochastic EMS model in enhancing the performance of the network and decreasing the operational costs of the MGs.

Addition of poly (ethylene-co-methacrylic acid) (EMAA) as self-healing agent to carbon-epoxy composites

Among several self-healing approaches to improve the durability of polymer-based materials during service, the addition of thermoplastics to a thermoset matrix has emerged as a promising self-healing alternative. In this study, poly (ethylene-co-methacrylic acid) (EMAA) was added to the mid-plane of carbon fiber-epoxy composite laminates to produce a self-healing system. Composite plates were manufactured with the addition of 5 wt%, 10 wt% and 15 wt% of EMAA as related to the matrix weight in the prepreg laminate. Interlaminar shear strength (ILSS) tests, dynamic mechanical analysis (DMA), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and field-emission gun scanning electron microscopy (FEG-SEM) were employed to evaluate the self-healing effect and composite properties before and after a healing cycle. Storage modulus was found to decrease with increasing content of EMAA in the laminate. Samples with EMAA showed complete recovery of interlaminar shear strength after healing.

Self-Healing Besides Restoration Methods in Smart Grid Distribution Networks

The Smart grid refers to a next-generation power grid which is a two-way information flow where electricity and information switch over between the service and its customer’s. The power system becomes smart by applying intelligence by way of multidirectional flow of electricity and information to create an extensive distribution network through smart grid technology. It made smarter power system by developing a networking communication, controls, automation, new technologies and tools working together to make the great efficient and more secure environment. For an effective integration and quality of the service to the consumer's smart grid technology is needed due to working with the electrical distribution system and quickly to respond digitally for rapidly changing electric demand. At this point, an electricity disruption such as a blackout can affect a series of failures that can affect several areas such as banking, traffic, and security. To address the power restoration, smart grid makes use of self-healing strategy which will allow automatic switching when equipment failure or outages occur. There have been numerous studies in the last decade or so in to even out the fundamental and mathematical challenges of making a smart self-healing grid a reality. In this paper, we explore the Self-healing approach for Smart grid Communications likewise discusses the service restoration methods in Distribution Networks of Smart Grid Environment.

Self-Healing Besides Restoration Methods in Smart Grid Distribution Networks

The Smart grid refers to a next-generation power grid which is a two-way information flow where electricity and information switch over between the service and its customer’s. The power system becomes smart by applying intelligence by way of multidirectional flow of electricity and information to create an extensive distribution network through smart grid technology. It made smarter power system by developing a networking communication, controls, automation, new technologies and tools working together to make the great efficient and more secure environment. For an effective integration and quality of the service to the consumer's smart grid technology is needed due to working with the electrical distribution system and quickly to respond digitally for rapidly changing electric demand. At this point, an electricity disruption such as a blackout can affect a series of failures that can affect several areas such as banking, traffic, and security. To address the power restoration, smart grid makes use of self-healing strategy which will allow automatic switching when equipment failure or outages occur. There have been numerous studies in the last decade or so in to even out the fundamental and mathematical challenges of making a smart self-healing grid a reality. In this paper, we explore the Selfhealing approach for Smart grid Communications likewise discusses the service restoration methods in Distribution Networks of Smart Grid Environment

Nested Formation Approach for Networked Microgrid Self-Healing in Islanded Mode

This paper proposes a novel nested restoration decision system (NRDS), which aims to minimize unused capacity of distributed generation (DG) for service restoration due to contingency during islanding stage. The proposed algorithm is based on the concept of nested microgrid formation, where the network control schemes are framed on a layered structure. The power-sharing strategy between neighboring microgrids in the network is from outer to inner microgrid loads, where the outermost microgrid exchanges power with utility grid only. The first stage refers to pre-fault scenario, which finds a solution for networked microgrid distributed generation as the initial setting. Furthermore, the second stage calculates additional redistribution requirements based on respective microgrid's deficiency using a solution index matrix. The proposed control has been evaluated on a networked microgrid system, while performing islanding.

Evaluation of Self-Healing Systems: An Analysis of the State-of-the-Art and Required Improvements

Evaluating the performance of self-adaptive systems is challenging due to their interactions with often highly dynamic environments. In the specific case of self-healing systems, the performance evaluations of self-healing approaches and their parameter tuning rely on the considered characteristics of failure occurrences and the resulting interactions with the self-healing actions. In this paper, we first study the state-of-the-art for evaluating the performances of self-healing systems by means of a systematic literature review. We provide a classification of different input types for such systems and analyse the limitations of each input type. A main finding is that the employed inputs are often not sophisticated regarding the considered characteristics for failure occurrences. To further study the impact of the identified limitations, we present experiments demonstrating that wrong assumptions regarding the characteristics of the failure occurrences can result in large performance prediction errors, disadvantageous design-time decisions concerning the selection of alternative self-healing approaches, and disadvantageous deployment-time decisions concerning parameter tuning. Furthermore, the experiments indicate that employing multiple alternative input characteristics can help with reducing the risk of premature disadvantageous design-time decisions.

A novel biomimetic design of a 3D vascular structure for self-healing in cementitious materials using Murray's law

Nature has always been a source of inspiration in engineering applications and vascular networks, as in human skin and in a tree leaf, are one attribute that has received attention in the design of resilient structures. A vascular system houses healing agents within its hollow channels or interconnected networks which are incorporated within a cement matrix. It is the only self-healing approach that has the capability to address different scales of damage in cementitious materials. The main aim of this work is to develop a novel vascular network inspired by nature for self-healing in cementitious systems. To achieve this, a biomimetic three-dimensional (3D) vascular network was designed and generated following Murray's law for circulatory blood volume transfer. The designed structures were constructed through 3D printing and assessed in a cement-based matrix. One-dimensional (1D) and two-dimensional (2D) models were also designed, printed and embedded into cement prisms to compare with the 3D vascular system. Load recovery was used to assess recovery in mechanical properties after the sample was cracked and pumped with sodium silicate for 28 days. Mechanical testing assessed the compatibility of the system with the surrounding matrix as well as the functionality of the network in delivering and releasing the healing agent at the location of damage. This initial proof of concept work confirmed the ability of all vascular systems to deliver the healing agent after a damage event, and the 3D vascular system demonstrated a significantly enhanced healing performance.

Design Strategy for Self-Healing Epoxy Coatings

Self-healing strategies including intrinsic and extrinsic self-healing are commonly used for polymeric materials to restore their appearance and properties upon damage. Unlike intrinsic self-healing tactics where recovery is based on reversible chemical or physical bonds, extrinsic self-healing approaches rely on a secondary phase to acquire the self-healing functionality. Understanding the impacts of the secondary phase on both healing performance and matrix properties is important for rational system design. In this work, self-healing coating systems were prepared by blending a bio-based epoxy from diglycidyl ether of diphenolate esters (DGEDP) with thermoplastic polyurethane (TPU) prepolymers. Such systems exhibit polymerization induced phase separation morphology that controls coating mechanical and healing properties. Structure–property analysis indicates that the degree of phase separation is controlled by tuning the TPU prepolymer molecular weight. Increasing the TPU prepolymer molecular weight results in a highly phase separated morphology that is preferable for mechanical performances but undesirable for healing functionality. In this case, diffusion of TPU prepolymers during healing is restricted by the epoxy network rigidity and chain entanglement. Low molecular weight TPU prepolymers tend to phase mix with the epoxy matrix during curing, resulting in the formation of a flexible epoxy network that benefits TPU flow while decreasing Tg and mechanical properties. This work describes a rational strategy to develop self-healing coatings with controlled morphology to extend their functions and tailor their properties for specific applications.

A review and current state of autonomic self-healing microcapsules-based dental resin composites

ObjectiveThis study systematically reviews the literature on self-healing microcapsule technology and evaluates the biocompatibility of self-healing microcapsules and the efficiency of crack repair within resin-based dental composites. MethodsAn electronic search was carried out using the following databases: MedLine (PubMed), Embase, the Cochrane Library and Google Scholar. All titles and abstracts of the articles and patents found were analysed and selected according to the eligibility criteria. Only studies published in English were included; the outcomes sought for this review were dental resin composites with self-healing potential. There were no restrictions on the type of self-healing system involved in dental resin composites. ResultsThe search yielded 10 studies and 2 patents involving self-healing approaches to dental resin composites. According to the current literature on self-healing dental resin composites, when a crack or damage occurs to the composite, microcapsules rupture, releasing the healing agent to repair the crack with a self-healing performance ranging from 25% to 80% of the virgin fracture toughness. SignificanceSelf-healing strategies used with resin composite materials have, to date, been bioinspired. So far, self-healing microcapsule systems within dental composites include poly urea-formaldehyde (PUF) or silica microcapsules. The main healing agents used in PUF microcapsules are DCPD monomer and TEGDMA-DHEPT, with other agents also explored. Silica microcapsules use water/polyacid as a healing agent. All self-healing systems have shown promising results for self-repair and crack inhibition, suggesting a prolonged life of dental composite restorations. More investigations and mechanical enhancements should be directed toward self-healing technologies in dental resin composites.

Autonomous Self-Healing of Electrical Degradation in Dielectric Polymers Using In Situ Electroluminescence

Summary Dielectric polymers are ubiquitous as electrical insulation in electrical power systems and electronic devices. Electrical treeing is typically regarded as an irreversible degradation process of dielectric polymers subjected to high electric stresses, which significantly limits their lifespan and endangers the reliability of electronics and electrical power systems. Here, we report self-healing polymers consisting of microcapsules that are capable of completely restoring the dielectric properties as a direct response to electrical tree degradation. We design the microcapsules with a relatively higher dielectric constant than polymer matrix to guide the propagation of electrical trees. The electroluminescence generated in situ during electrical treeing of polymers triggers crosslinking of the healing agents released from the capsules to repair the electrically damaged areas under ambient conditions. Notably, the breakdown strength of the mended region is largely enhanced upon healing, which was initiated at different locations. The integration of autonomous healing capability into dielectric materials opens new avenues to smart polymers for electronics and energy applications.

Rheological behaviour of bitumen blending with self-healing microcapsule: Effects of physical and chemical interface structures

Rejuvenator-containing microcapsules for spontaneously healing microcracks in bitumen have been developed and are already commercially available. Such smart self-healing approaches are promising for use in developing long-life pavements. The aim of this work was to investigate the rheological behavior of bitumen blended with self-healing microcapsules effected by physical and chemical interface structures. Based on a point of colloids, three self-healing microcapsule samples were used, with average diameters of 10, 20, and 30 μm. Bitumen composites with various microcapsule contents (1%, 2%, 3%, 4%, and 5%) were produced. Morphological analysis showed that the microcapsules were spherical and did not agglomerate. Fluorescence microscopy and X-ray transmission computed tomography showed that the microcapsules were homogeneously dispersed in the bitumen and did not rupture or agglomerate. The smaller microcapsules had larger specific surface areas. The size and content of the microcapsules affected the physical parameters of the bitumen, e.g., penetration, softening point, and ductility. Fourier-transform infrared spectroscopy showed that the bitumen was chemically linked with the microcapsules via functional group reactions. A dynamic shear rheometer was used to investigate the rheological behaviors of the bitumen/microcapsule samples. The complex shear modulus and phase angle data showed that the microcapsule content and size greatly affected the rheological behavior of the bitumen. The bitumen viscoelasticity depended strongly on the contact area and chemical bonds. A mechanistic analysis was performed to clarify the rheological behavior changes in terms of physics and chemistry. This result of this preliminary analysis will be helpful in the screening and application of self-healing microcapsule products.

Evaluation of nano-graphene effect on mechanical behavior of clayey sand with microstructural and self-healing approach

This study investigated the effect of nano-graphene on the mechanical properties and the self-healing process of clayey sand using the uniaxial test. Based on the results of the experiments in this research, the self-healing of samples with 0.06% nano-graphene at 28 days was ∼73% higher than that of the samples without additive at the same time. According to the SEM images, it can be assured that the added nano-graphene plays an active role in the self-healing process. In the final step, the undrained shear strength of clayey sand was considered as the output variable in terms of the percentage of fine grains and the nano-graphene as the input variables using the obtained network structure. In this way, the highest undrained shear strength in the clayey sand was estimated at 22% fine grain and 0.06% nano-graphene additive to be approximately equal to 0.64 kg/cm2.

Self-healing hardware systems: A review

Self-healing is increasingly becoming a promising approach to designing reliable digital systems, and it refers to the ability of a system to detect faults or failures and fix them through healing or repairing. Digital systems with architecture for self-healing are expected to compensate faults. However, there are a few research challenges that need to be overcome before self-healing becomes a mainstream approach. For example, current self-healing techniques face challenges such as scalability, reliability, area overhead, and mapping. This paper explains the self-healing concept and investigates the self-healing approaches related to digital design in the literature. It gives a general overview of the topic and explains levels of abstraction at which self-healing can be used: hardware level, application level, and system level. The paper presents multiple related works at each level of abstraction. In the faulted phase, different types of faults and fault detection methods are described. For the evaluation of a self-healing technique, this paper presents the parameters which can be used to evaluate a self-healing method. These parameters are redundancy rate, the maximum ratio of repair, self-healing time consumption, reliability, and area overhead. The paper also presents a comparison between previous works of self-healing in terms of evaluation techniques. Implementations using VHDL and ISE Xilinx Vertex-5 for self-healing on Embryonic Hardware (EmHW) and Network-on-Chip (NoC) are also presented. The simulation results show the contribution of self-healing to improve system reliability and mean time to failure.

An investigation of the compatibility of different approaches to self-healing concrete: The superabsorbent polymers and microbially induced calcite precipitation

The concept of the self-healing concrete, thus an improvement of the durability of concrete structures, has become a widely investigated topic in recent decades. The aim of this study is to examine a possible combination of two existing approaches to the spontaneous crack-sealing – the biologically driven calcite precipitation and the addition of superabsorbent polymers (SAP) into the concrete matrix. Firstly, the paper compares the absorption rate of SAP in various solutions, including a nutrient-based solution which is used in the bio-concrete. The results show that the ionic composition of the liquid influence the swelling capacity greatly. In this study, the absorption rate of SAP in the nutrient-based solution is as low as 6% of the rate in distilled water. Thus, this finding could indicate a possible drawback of the combination of the proposed self-healing approaches. Further, this paper determines the impact of the SAP addition to cement paste with different water/cement ratios. In this experiment, the SAP is applied in various dosages (1% and 0.5% by c. w.) and states (a dry state or a fully swollen state). The conducted flowability and mechanical properties tests indicate a profound, generally negative, impact of the SAP addition on the cement paste characteristics. The paper then discusses possible adjustments of the SAP-cement paste composition and compares the present results with previous studies.

Autonomous Supramolecular Interface Self-Healing Monitored by Restoration of UV/Vis Absorption Spectra of Self-Assembled Thiazole Layers.

Longevity of complex organic devices critically depends on the supramolecular integrity of the constituting layers and interfaces. Because the latter are soft matter, they can structurally respond to perturbation of their supramolecular structure by relaxing back to a thermodynamically favorable state. To use this response for self-healing of optoelectronically active layers and particularly interfaces, the degraded dyes in these layers need to be exchanged with non-degraded ones. Here, we present a dye layer interfaced between a solid surface and a dye reservoir that autonomously self-heals after photo-degradation of single molecules to restore its optical function. Surface sensitive in situ photothermal deflection spectroscopy reveals that this supramolecular self-healing approach critically depends on the thermodynamic stability of the layer, the chemical change of the dye upon degradation, and the medium dissolving the degraded dye and providing the reservoir dyes. Hence, the interplay of these parameters is key to successfully using this supramolecular self-healing approach to thin layers and interfaces in organic device for increased sustainability of organic optoelectronics and related fields.