Self-Healing Materials Hager, Martin D.; Greil, Peter; Leyens, Christoph ...
Advanced materials (Weinheim),
December 14, 2010, Volume:
22, Issue:
47
Journal Article
Peer reviewed
Self‐healing materials are able to partially or completely heal damage inflicted on them, e.g., crack formation; it is anticipated that the original functionality can be restored. This article covers ...the design and generic principles of self‐healing materials through a wide range of different material classes including metals, ceramics, concrete, and polymers. Recent key developments and future challenges in the field of self‐healing materials are summarised, and generic, fundamental material‐independent principles and mechanism are discussed and evaluated.
Self‐healing materials are able to partially or completely heal damage inflicted on them, e.g., crack formation; it is anticipated that the original functionality of self‐healed materials can be restored. This behavior can be applied across a wide range of different material classes including metals, ceramics, concrete, and polymers.
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•An overview of the corrosion protection in extrinsic self-healing materials.•The existing and recent corrosion-protection self-healing techniques are reviewed.•Various fabrication ...methods of microcapsules and hollow fibers are discussed.•Directions for the further improvements are highlighted.
Corrosion is a natural phenomenon which significantly deteriorates metal properties. The existing corrosion protection methods are costly and require a regular replacement of sacrificial metals or inevitable use of toxic chemicals. So far, various extrinsic self-healing approaches have been attempted to prevent metal corrosion, which have facilitated the corrosion protection at a reasonable cost and non-toxicity level. Here, we review the existing and the recent novel corrosion-protective extrinsic self-healing technologies, focusing on the capsule-based and the fiber-based self-healing approaches, while looking at the pros and cons of these methods. In addition, by introducing potential ways, this review aims to provide insights for the further development of extrinsic self-healing technologies.
Self-healing materials have been attracting the attention of the scientists over the past few decades because of their effectiveness in detecting damage and their autonomic healing response. ...Self-healing materials are an evolving and intriguing field of study that could lead to a substantial increase in the lifespan of materials, improve the reliability of materials, increase product safety, and lower product replacement costs. Within the past few years, various autonomic and non-autonomic self-healing systems have been developed using various approaches for a variety of applications. The inclusion of appropriate functionalities into these materials by various chemistries has enhanced their repair mechanisms activated by crack formation. This review article summarizes various self-healing techniques that are currently being explored and the associated chemistries that are involved in the preparation of self-healing composite materials. This paper further surveys the electronic applications of self-healing materials in the fields of energy harvesting devices, energy storage devices, and sensors. We expect this article to provide the reader with a far deeper understanding of self-healing materials and their healing mechanisms in various electronics applications.
An extrinsic self‐healing coating system containing tetraphenylethylene (TPE) in microcapsules was monitored by measuring aggregation‐induced emission (AIE). The core healing agent comprised of ...methacryloxypropyl‐terminated polydimethylsiloxane, styrene, benzoin isobutyl ether, and TPE was encapsulated in a urea‐formaldehyde shell. The photoluminescence of the healing agent in the microcapsules was measured that the blue emission intensity dramatically increased and the storage modulus also increased up to 105 Pa after the photocuring. These results suggested that this formulation might be useful as a self‐healing material and as an indicator of the self‐healing process due to the dramatic change in fluorescence during photocuring. To examine the ability of the healing agent to repair damage to a coating, a self‐healing coating containing embedded microcapsules was scribed with a razor. As the healing process proceeded, blue light fluorescence emission was observed at the scribed regions. This observation suggested that self‐healing could be monitored using the AIE fluorescence.
An extrinsic self‐healing coating containing tetraphenylethylene in microcapsules is monitored by aggregation‐induced emission (AIE). As the healing process proceeds, blue fluorescence is observed at scribed region. Self‐healing can be monitored using the AIE.
The utilization of dynamic covalent and noncovalent bonds in polymeric materials offers the possibility to regenerate mechanical damage, inflicted on the material, and is therefore of great interest ...in the field of self‐healing materials. For the design of a new class of self‐healing materials, methacrylate containing copolymers with acylhydrazones as reversible covalent crosslinkers are utilized. The self‐healing polymer networks are obtained by a bulk polymerization of an acylhydrazone crosslinker and commercially available methacrylates as comonomers to fine‐tune the Tg of the systems. The influence of the amount of acylhydrazone crosslinker and the self‐healing behavior of the polymers is studied in detail. Furthermore, the basic healing mechanism and the corresponding mechanical properties are analyzed.
Acylhydrazone crosslinked polymer films are synthesized by the copolymerization of a new acylhydrazone crosslinker with different commercially available methacrylates. The self‐healing behavior of the damaged material is studied in detail with the help of differential scanning calorimetry, scratch testing experiments, profilometry, dynamic‐mechanical thermal analysis, and temperature dependent FT‐IR as well as solid state NMR measurements.
Traditional electronic devices inevitably undergo degradation over time due to deformation, fatigue, or mechanical damage, ultimately resulting in device failure. To overcome this issue, researchers ...have pioneered the field of elastic electronics, incorporating higher mechanical tensile properties or strain resistance into electronic devices. Elastic materials, especially self‐healing elastomers (SHEs) are regarded as a crucial component in elastic electronics, offering the potential for restoring functionality and prolonging the lifespan of electronic devices. SHEs possess remarkable ability to tolerate significant deformation and utilize intrinsic dynamic chemical bonds to autonomously repair themselves from varying degrees of damage. The acquisition of intrinsic SHEs is key to the development of self‐healing elastic electronics and has attracted global attention. This review offers a comprehensive overview of the current advancements in self‐healing elastic electronics. First, the various self‐healing mechanisms present in elastomeric material systems are summarized. Second, the design strategies for constructing SHEs based on self‐healing mechanisms are reviewed in detail, with a particular emphasis on dynamic covalent and non‐covalent bonds. Subsequently, various optoelectronic applications of SHEs in elastic electronics are summarized. Finally, the challenges and prospects that lie ahead in order to foster further development in this rapidly growing field are outlined.
In recent years, significant advancements have been made in self‐healing elastic electronics, including the design of self‐healing elastomers and corresponding elastic optoelectronic devices. Herein, a detailed and comprehensive overview of material design strategies including dynamic covalent/non‐covalent bonds is provided, and various optoelectronic applications including e‐skins, field effect transistors, energy storage devices, perovskite solar cells, and electroluminescent devices.
Self-healing polymer composites possess the inherent ability to heal the damage event autonomically or non-autonomically with external intervention. These advanced materials can be commercialized if ...the challenges and limitations of different self-healing mechanisms are well known and considered. These include capsule-based healing systems, vascular healing systems, and intrinsic healing systems. To date, most of the reviews have studied and reported on different self-healing mechanisms including their response to impact, fatigue, and corrosion tests. This review focuses mostly on extrinsic and intrinsic self-healing polymer composites which have been reported during the past five years by comparing their healing efficiency, advantages, and challenges in the prospect of their future development as well as their possible applications across various industries such as aerospace, automobile, coating, electronics, energy, etc.
The effect of structural parameters such as hard segment content and cross‐linking degree on the mechanical properties of waterborne self‐healing polyurethane and the effect of tensile strength, ...self‐healing conditions (temperature, time) on the self‐healing properties were investigated. These results demonstrated that as the increasing of the content of hard segments/the cross‐linking agent, the tensile strength of the sample increased and the self‐healing performance exhibited a downward trend. When the tensile strength reached 40 MPa, it could hardly healed, even if prolonging the self‐healing time or increasing the self‐healing temperature. Mechanism study demonstrated that the self‐healing ability was attributed to the dynamic exchange of disulfide bonds and the thermal reversibility of hydrogen bonds in the system. Hydrogen bonding could provide the initial self‐healing force and promote the dynamic exchange reaction of disulfide bonds, while high hydrogen bonding is not conducive to the movement of macromolecular segments, causing a decrease in the self‐healing efficiency.
The increasing concern for safety and sustainability of structures is calling for the development of smart self‐healing materials and preventive repair methods. The appearance of small cracks (<300 ...µm in width) in concrete is almost unavoidable, not necessarily causing a risk of collapse for the structure, but surely impairing its functionality, accelerating its degradation, and diminishing its service life and sustainability. This review provides the state‐of‐the‐art of recent developments of self‐healing concrete, covering autogenous or intrinsic healing of traditional concrete followed by stimulated autogenous healing via use of mineral additives, crystalline admixtures or (superabsorbent) polymers, and subsequently autonomous self‐healing mechanisms, i.e. via, application of micro‐, macro‐, or vascular encapsulated polymers, minerals, or bacteria. The (stimulated) autogenous mechanisms are generally limited to healing crack widths of about 100–150 µm. In contrast, most autonomous self‐healing mechanisms can heal cracks of 300 µm, even sometimes up to more than 1 mm, and usually act faster. After explaining the basic concept for each self‐healing technique, the most recent advances are collected, explaining the progress and current limitations, to provide insights toward the future developments. This review addresses the research needs required to remove hindrances that limit market penetration of self‐healing concrete technologies.
Self‐healing concrete is a smart concrete designed to manage occurring cracks through the activation of an incorporated mechanism resulting in autonomous healing of cracks. This damage management principle provides the material superior functionality with respect to reduced maintenance and repair requirements, increased service life, and sustainability. This review article elucidates and critically evaluates different (stimulated) autogenous and autonomous healing mechanisms.
Polymers have swiftly replaced conventional metallic materials in aviation due to their lightweight and easy processability. Usages of polymers are presently mostly limited to non‐critical ...components. Flight safety is paramount in aviation and overrides all other factors. The aviation industry is averse to the usage of polymeric materials in critical component applications owing to the nature of failure being catastrophic. The review has covered various polymeric component failures and their root cause reasons. To overcome the inherent weakness in polymers currently used, a strategy to mimic nature is being explored by researchers. Self‐healing polymers can overtake metals if coupled with safe fail technology. Such materials have additional advantages in terms of enhanced longevity and ultimate life cycle. This review critically analyzed various factors driving research and development of self‐healing material for aviation applications. Various extrinsic and intrinsic self‐healing materials have been reviewed in the present work. Composites with an extrinsic self‐healing mechanism possess good healability and strength and can potentially replace current materials. Further, candidate polymeric materials with intrinsic self‐healing capability for the aviation field are extensively reviewed. Various aviation‐grade polymers like epoxy, Poly(methyl methacrylate), polycarbonate, and elastomeric materials with possible chemistries of intrinsic healing like Diel‐Alder reaction, Shape memory assisted self‐healing and covalently adaptable networks have been critically examined. Authors believe that extrinsic self‐healing technology is mature enough for use in the secondary structure of aircraft. At the same time, present technologies of intrinsic materials are not mature enough for flight safety reasons in aircraft; however, they are candidate materials for UAVs. Fast‐growing aviation field, coupled with the entry of UAVs, calls for environmentally sustainable material support. Therefore, this review explores materials within the sphere of high mechanical properties coupled with a low environmental impact.
Development of self‐healing materials for aviation applications.
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