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Autonomously self‐healing, reversible, and soft adhesive microarchitectures and structured electric elements could be important features in stable and versatile bioelectronic devices adhere to complex surfaces of the human body (rough, dry, wet, and vulnerable). In this study, we propose an autonomous self‐healing multi‐layered adhesive patch inspired by the octopus, which possess self‐healing and robust adhesion properties in dry/underwater conditions. To implement autonomously self‐healing octopus‐inspired architectures, a dynamic polymer reflow model based on structural and material design suggests criteria for three‐dimensional patterning self‐healing elastomers. In addition, self‐healing multi‐layered microstructures with different moduli endows efficient self‐healing ability, human‐friendly reversible bio‐adhesion, and stable mechanical deformability. Through programmed molecular behavior of microlevel hybrid multiscale architectures, the bioinspired adhesive patch exhibited robust adhesion against rough skin surface under both dry and underwater conditions while enabling autonomous adhesion restoring performance after damaged (over 95% healing efficiency under both conditions for 24 h at 30°C). Finally, we developed a self‐healing skin‐mountable adhesive electronics with repeated attachment and minimal skin irritation by laminating thin gold electrodes on octopus‐like structures. Based on the robust adhesion and intimate contact with skin, we successfully obtained reliable measurements during dynamic motion under dry, wet, and damaged conditions. [ABSTRACT FROM AUTHOR]

Herein, a self-healing waterborne polyurethane (WPU) based on a novel visible light-stimulated healing agent from the aromatic Schiff base family (SBWPU) was synthesized. Moreover, this polymer exhibited remarkable mechanical properties, making it an ideal matrix for the preparation of a new nano-composite coating using hexagonal-boron nitride/graphene oxide/nickel oxide (h-BN/GO/NiO) nano-composite for anti-corrosion applications. SBWPU containing 15 wt % of synthesized healing agent (SBWPU-15) demonstrated favorable healing properties (80.03 %) under a visible light lamp after 24 h (at ambient temperature). SBWPU containing 20 % of the healing agent (SBWPU-20) showed high mechanical properties (20.80 MPa) and an increase in its hydrophobic properties. Additionally, its water absorption rate decreased, making it an attractive option as a polymer matrix for anti-corrosion coating applications. The nano-composite coatings (CSBWPU) were formulated by introducing varying amounts of h-BN/GO/NiO into the SBWPU-20. The coatings displayed an increase in contact angle and a decrease in water absorption rate. The electrochemical impedance spectroscopy (EIS) results revealed that the 0.75-CSBWPU, containing 0.75 % nano-composite, had the highest corrosion resistance (1.58 × 1010 Ω cm2) after 90 days of immersion in seawater. This work offers a potentially helpful concept for developing an eco-friendly, secure, uncomplicated accessibility self-healing polymeric system with controllable mechanical features, which are also favorable for designing novel corrosion protection composite coatings.

This work emphasized on development of a novel bio-derived self-healing copolymer fabricated from benzoxazine and epoxy resins by varying weight ratios. The bio-derived benzoxazine (E-fa) acted as a healing agent was copolymerized with bio-derived epoxy resin namely epoxidized castor oil (ECO). Three main essential properties of the developed copolymer were systematically investigated: thermal property, mechanical property, and self-healing capacity. The numerical simulation was also used to study and predict the ability of roof coatings based on the developed copolymers. The results showed that the reversible crosslinking reaction occurred and resulted in state transition of the copolymers. The mechanical property i.e., tensile strength and peel strength to stainless steel substrate, were substantially improved with the incorporation of ECO. The increase in E-fa contents can enhance the thermos-responsive healing performance of the copolymers up to 93% via reversible reactions with rapid surface damage healed within 2 min. Furthermore, the experimental and numerical results revealed that the thermo-responsive thermoset self-healing bio-derived benzoxazine/epoxy copolymers have a potential use in coating applications required fast self-healing performance and good mechanical properties.

Abstract Autonomously self‐healing, reversible, and soft adhesive microarchitectures and structured electric elements could be important features in stable and versatile bioelectronic devices adhere to complex surfaces of the human body (rough, dry, wet, and vulnerable). In this study, we propose an autonomous self‐healing multi‐layered adhesive patch inspired by the octopus, which possess self‐healing and robust adhesion properties in dry/underwater conditions. To implement autonomously self‐healing octopus‐inspired architectures, a dynamic polymer reflow model based on structural and material design suggests criteria for three‐dimensional patterning self‐healing elastomers. In addition, self‐healing multi‐layered microstructures with different moduli endows efficient self‐healing ability, human‐friendly reversible bio‐adhesion, and stable mechanical deformability. Through programmed molecular behavior of microlevel hybrid multiscale architectures, the bioinspired adhesive patch exhibited robust adhesion against rough skin surface under both dry and underwater conditions while enabling autonomous adhesion restoring performance after damaged (over 95% healing efficiency under both conditions for 24 h at 30°C). Finally, we developed a self‐healing skin‐mountable adhesive electronics with repeated attachment and minimal skin irritation by laminating thin gold electrodes on octopus‐like structures. Based on the robust adhesion and intimate contact with skin, we successfully obtained reliable measurements during dynamic motion under dry, wet, and damaged conditions.

Intrinsic self-healing polymers via dynamic covalent bonds have been attracting extensive attention because of their repeatable self-healing property. Herein, a novel self-healing epoxy resin was synthesized with disulfide-containing curing agent via the condensation of dimethyl 3,3′-dithiodipropionate (DTPA) and polyether amine (PEA). Therefore, in the structure of cured resin, flexible molecular chains and disulfide bonds were imported into the cross-linked polymer networks for triggering self-healing performance. The self-healing reaction of cracked samples was realized under a mild condition (60 °C for 6 h). The distribution of flexible polymer segments, disulfide bonds and hydrogen bonds in cross-linked networks plays a great role in the self-healing process of prepared resins. The molar ratio of PEA and DTPA strongly affects the mechanical performance and self-healing property. Especially when that molar ratio of PEA to DTPA is 2, the cured self-healing resin sample showed great ultimate elongation (795%) and excellent healing efficiency (98%). The products can be used as an organic coating, in which the crack could self-repair during a limited time. The corrosion resistance of a typical cure coating sample has been testified by an immersion experiment and electrochemistry impedance spectrum (EIS). This work provided a simple and low-cost route to prepare a self-healing coating for prolonging the service life of conventional epoxy coatings. [ABSTRACT FROM AUTHOR]

The three-dimensional (3D) printing of hydrogel is an issue of interest in various applications to build optimized 3D structured devices beyond 2D-shaped conventional structures such as film or mesh. The materials design for the hydrogel, as well as the resulting rheological properties, largely affect its applicability in extrusion-based 3D printing. Here, we prepared a new poly(acrylic acid)-based self-healing hydrogel by controlling the hydrogel design factors based on a defined material design window in terms of rheological properties for application in extrusion-based 3D printing. The hydrogel is designed with a poly(acrylic acid) main chain with a 1.0 mol% covalent crosslinker and 2.0 mol% dynamic crosslinker, and is successfully prepared based on radical polymerization utilizing ammonium persulfate as a thermal initiator. With the prepared poly(acrylic acid)-based hydrogel, self-healing characteristics, rheological characteristics, and 3D printing applicability are deeply investigated. The hydrogel spontaneously heals mechanical damage within 30 min and exhibits appropriate rheological characteristics, including G′~1075 Pa and tan δ~0.12, for extrusion-based 3D printing. Upon application in 3D printing, various 3D structures of hydrogel were successfully fabricated without showing structural deformation during the 3D printing process. Furthermore, the 3D-printed hydrogel structures exhibited excellent dimensional accuracy of the printed shape compared to the designed 3D structure. [ABSTRACT FROM AUTHOR]

Eugenol-based self-healing polymers were synthesized in a very short time of 94–159 s. Polymerization of eugenol catalyzed by H2SO4-CH3COOH yielded the corresponding self-healing polymers in quantitative yields in the range of molecular weight (5.18–15.10) × 105 g/mol. The polymer exhibited self-healing behavior at room temperature due to hydrogen bonds between the hydroxyl groups of polyeugenol and the hydroxyl groups of sulfuric acid. This material can function as a polyelectrolyte and a novel self-healing catalyst for biodiesel production.

This work emphasized on development of a novel bio-derived self-healing copolymer fabricated from benzoxazine and epoxy resins by varying weight ratios. The bio-derived benzoxazine (E-fa) acted as a healing agent was copolymerized with bio-derived epoxy resin namely epoxidized castor oil (ECO). Three main essential properties of the developed copolymer were systematically investigated: thermal property, mechanical property, and self-healing capacity. The numerical simulation was also used to study and predict the ability of roof coatings based on the developed copolymers. The results showed that the reversible crosslinking reaction occurred and resulted in state transition of the copolymers. The mechanical property i.e., tensile strength and peel strength to stainless steel substrate, were substantially improved with the incorporation of ECO. The increase in E-fa contents can enhance the thermos-responsive healing performance of the copolymers up to 93% via reversible reactions with rapid surface damage healed within 2 min. Furthermore, the experimental and numerical results revealed that the thermo-responsive thermoset self-healing bio-derived benzoxazine/epoxy copolymers have a potential use in coating applications required fast self-healing performance and good mechanical properties. [ABSTRACT FROM AUTHOR]

Self-healing polymer materials are able to self-repair damage and recover themselves after cracks generating to maintain their structural and functional integrity. According to whether additional repair agent is added, self-healing polymers are mainly divided into two categories, namely extrinsic- and intrinsic-based polymers.The key materials of electrochemical energy storage devices will experience irreversible mechanical damage in extreme condition applications, for example, the energy storage device more prone to physical damage inwearable devices during the multiple bending and deformation processes. These problems severely reduce the stability of energy storage and delivery, and shorten the life of the devices. Therefore, the application of self-healing polymers in electrochemical energy storage devices to improve the stability and life of devices has become one of the research hotspots in recent years. Herein,this article summarizes the repair mechanism of self-healing polymer materials (capsule-based, vascular-based, and intrinsic polymers), with main focus on intrinsic self-healing polymer and its research progress in the field of electrochemical energy storage, which based on molecular interactions to achieve multi-time reversible healing without any additional repair agent.The self-healing electrode and electrolyte system were reviewed respectively, and then the self-healing mechanism and its influence on the electrochemical performance of energy storage devices were described. The research progress of self-healing functional polymer as high specific energy electrode binder, interface modification layer and self-healing electrolyte were summarized in detail. Finally, the future perspectives regarding the future development of self-healing polymer materials were also discussed.

Self-healing polymer materials have the functional characteristics of curing when a crack penetrates the material. Damage response, healing ability and healing performance are the most important healing characteristics of a self-healing material. Self-healing in a material system is employed through different methodologies, such as capsulation, vascular filling and intrinsic healing systems. The most challenging factor in fabrication of self-healing material is the ‘carrier filling’ in both the vascular and capsule type healing methods. The self-healing is either autonomic or external, depending on the actuation of the healing. This paper reviews the healing agent carrier preparation for vascular self-healing systems and compares the vascular healing system with intrinsic self-healing. The review revealed that, in most cases, preparation of healing agents is challenging greater than understanding the healing mechanism. The behaviour of self-healing material under fatigue, impact, and ballistic characterisation is also reviewed towards suggesting the self healing materials for aerospace applications.

Copyright of Journal of Petrochemical Universities / Shiyou Huagong Gaodeng Xuexiao Xuebao is the property of Journal Editorial Department Of Liaoning Shihua University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Self-healing polymers are a class of smart materials that have attracted many researchers due to their unique ability. These materials are able to heal part of the damage without the need to identify the site. In order to study the behavior of these polymers, a thermodynamically consistent model is proposed to predict the mechanical response. Along with this, the implicit time-discrete form of the constitutive model is presented in order to utilize in ABAQUS software by UMAT subroutine. In the discretization, the Newton-Raphson method has been used to update internal variables such as viscoplastic strain components. Considering the calibration of the material parameters by the experimental results of the asphalt sample, the movement of vehicle on the desired pavement has simulated. In this research, a detailed explanation of how to perform the finite element analysis of mechanical behavior of asphalt pavements is presented using constitutive model and its implicit discretization. In the following, its validation with existing experimental results is also carried out. Next, a comparison between the simulations is performed without and with healing effect. From the results of finite element analysis, the important role of healing in the life of the pavement can be noted, which can increase the recovery of damage up to 20%.

The designs of highly extensible soft materials in nature are of a fundamental interest to engineers so that insights into the production of modern, synthetic materials can be gleaned. Marine gastropods of the genus Busycotypus produce a protein based elastomer which possesses a unique combination of stiffness and extensibility. Furthermore, this material displays shape-memory/self-healing properties that are unmatched in synthetic engineering systems. Four variants of the precursor protein components of the egg capsules are highly unique in their amino acid sequences, showing no homology to any known protein families. These proteins are strongly a-helicaì in nature, and can self-assemble into nanometer scaled fibers in vitro. The remarkable reversibly extensibility of the bulk material is dictated not by entropie forces, but rather by a crystalline phase transition within the protein components when the material is put under tension. Proteins shift from a-helix to ß-sheet, and it is this uncoiling of helices within the polymer backbone that allows for the extensibility of the egg capsules. This transition is reversible, as when loads are removed and the material is allowed to relax, it returns to its original a-helical conformation. When examined more closely, it is shown that this a«->>ß transition is a multi-step transformation which involves first the uncoiling of crystalline a-helices into non-crystalline random coils before these then lock into ß-sheets. These different steps dictate changes in the mechanical properties of the material as this transition is occurring. Furthermore, the supramolecular structure of how the individual proteins interact in the intact material also changes throughout tension/relaxation cycles. These structural changes also have effects on the bulk mechanical properties of the material. This work explores in detail the structure-function relationships of Busycotypus egg capsule material mentioned above.

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• A self-healing hydrogel is developed based on an interpenetrating polymer network strategy. • Chemically/ionically cross-linked Fe3+/PAA and physically cross-linked PVA organize the IPN. • The hydrogel satisfies the three capabilities of robustness, self-healing, and conductivity. • The multimodal sensing capabilities for strain, pressure, and temperature are determined. • A dual sensor attached to a finger simultaneously detects folding/pressure-motions. Conductive self-healing polymer hydrogel and related soft sensor devices are receiving considerable attention from academia to industry because of their impacts on the lifetime and ergonomic design of soft robotics, prosthesis, and health monitoring systems. However, the development of such a material has thus far been limited considering performances and accessibility. Herein, robustness, self-healing, and conductivity for soft electronic skin are realized by an interpenetrating polymer network (IPN) system based on chemical/ionic cross-linked poly(acrylic acid) containing ferric ions, intercalated with physically cross-linked poly(vinyl alcohol). This IPN hydrogel successfully satisfies all three aforementioned capabilities; elongation at break greater than 1400%; recovery to original mechanical properties greater than 80% after 24 h; and 0.14 S m−1 of ionic conductivity, which is electrically healable. Such ionic conductivity of hydrogels enables multimodal sensing capabilities, i.e., for strain, pressure, and temperature. Particularly, a uniquely designed dual sensor attached to a finger simultaneously detects mechanical folding and pressure changes independently and can undergo large deformation 1000 times repeated and heating up to 90 °C. [ABSTRACT FROM AUTHOR]

Abstract In this work, we report matrix and interfacial healing capabilities for hybrid DA-based polymer nanocomposites. Thermo-reversible self-healing nanocomposites were prepared by reinforcing bismaleimide grafted graphite nanoplatelets (B-GNPs) in a DA-based hybrid polymer matrix (HPM). The maleimide functional moieties were found grafted on B-GNPs that form globular networked structures on the nanoplatelets. Data from the TG-DSC revealed increased exothermic peaks corresponding to DA and retro-DA bond formation due to the incorporation of B-GNPs in HPM. This indicates the formation of DA bonds proficient enough to establish self-healing at the interfaces of B-GNPs and HPM. We also found that incorporation of B-GNPs in HPM having 40 wt% irreversible epoxy resin (DA40) has the potential to uplift the mechanical stability along with self-healing efficiency demonstrating successful interfacial healing. The resulting B-GNPs reinforced nanocomposites of DA40 showed maximum healing efficiency of ~87% with multiple times healing capability. The tensile strength and modulus were also significantly increased by ~242% and ~41% in comparison to pristine DA40. This study espouses the potential use of B-GNPs for multiple interfacial healing along with matrix healing of hybrid polymer nanocomposites. Highlights • Self-healing of hybrid DA-based polymer nanocomposites has been successfully demonstrated. • Interfacial healing was demonstrated using bismaleimide functionalized GNPs. • The self-healing composites showed maximum healing efficiency of ~87%. • The composites can be healed up to 5 times without significant reduction of mechanical properties. [ABSTRACT FROM AUTHOR]

• The entanglements improve the strength of the polymer from 4.4 MPa to 9.1 MPa. • The resultant elastomer exhibits a strength of 18.4 MPa with a healing efficiency of 86.2 % after 30 s healing. • The elastomer can reversibly lift a 1000 times weight of its own with a strain of 28% upon heating–cooling cycle. Self-healing polymeric material, which can heal the cracks repeatedly and thus definitely prolong their lifetime in practical applications, has attracted intensive interesting in recent years. However, it is still a great challenge to both achieve fast self-healing ability and high mechanical strength. Considering the mechanism of fast self-healing is the re-bonding of dynamic bonds in the fracture surfaces, the dense physical cross-linking might be a good option for fast self-healing polymer to solve the trade-off between self-healing ability and mechanical strength. To this end, the highly entangled polymer chains are thereby introduced to improve the mechanical strength of the elastomer by simply increasing the monomer concentration. As expected, the mechanical strength of the resultant elastomers increases with monomer concentration, accompanied by a slight decline in self-healing ability. In addition, further increment of the mechanical strength to 18.4 Mpa is achieved by introducing anisotropic structure into the highly entangled polymers by pre-stretching. Most importantly, the resultant polymer exhibits high recovery and fast self-healing ability with a healing efficiency of 86.2 % after only 30 s healing at room temperature. Moreover, the highly entangled polymer chains also improve the actuation performance of the elastomer with anisotropic structure, which can lift up about 1000 times of its own weight reversibly upon heating–cooling cycles with a maximum tensile stroke of ca. 28 %. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Aliphatic polycarbonate based polyurethane forms strong supramolecular structures. • Polyurethane involves three types of physical networks of different thermal stability. • Order–disorder transitions and entanglement formation depend on polymer composition. • Polyurethane is efficiently self-healed. Abstract The aliphatic polycarbonate based polyurethanes (PU) from poly(hexamethylene) carbonate diol (PC), hexamethylenediisocyanate and hexanediol were synthesized, characterized and designed as promising self healing polymers. The symmetrical linear PU structure containing the hexamethylene sequences results in a high degree of ordering and strong superstructures, manifested by a high crystallinity of the PC soft phase and a strong self-assembly of linear hard segments (HS). At the optimum composition, both supramolecular structures percolate resulting thus in the singnificant reinforcement. The PU, undergoing order–disorder transitions, involves three types of physical crosslinks with different thermal stability; PC crystalline phase, HS domains and in addition the entanglements. The structure evolution and reversible sol–gel transition during formation/breaking of the corresponding physical networks was followed by rheology, DSC and FTIR. The kinetics of build-up and stability of physical networks is governed by the content of HSs. The investigation contributed to the understanding and control of the thermal phase transitions of supramolecular structures in aliphatic PCPUs. The strong supramolecular structure undergoing order–disorder transitions, presence of thermally stable entanglement network and excellent mechanical properties make the PCPU suitable as a strong self-healing polymer. Two structural motifs are present: the thermally sensitive structure generating self-healing properties and the shape persistent entanglement network structure preventing the irreversible deformation. The efficient healing and restoration of the original structure and mechanical properties after damage of the polymer were checked by microscopy and tensile testing. [ABSTRACT FROM AUTHOR]

To increase the durability and reliability of thermosets, self-healing via a vascular network, is developed. A judicious choice of healing agents proves to be necessary to achieve the best recovery of properties. Four low viscosity two-component epoxy-amine healing systems were compared, to check which glass transition temperature range would be best to recover mechanical properties (T g ranging from −8 to 68 °C). Interdiffusion experiments show that all systems react sufficiently slowly at room temperature to allow interdiffusion of epoxy and amine over more than 1 mm before the diffusion is stopped by vitrification. Swelling tests revealed that most of the selected healing agents diffuse into the surrounding matrix and swell it. This might be beneficial for crack closure and improved adhesion between healing system and matrix. Flexural tests demonstrated that, the higher the glass transition temperature of the fully cured healing system, the higher the healing capability. [ABSTRACT FROM AUTHOR]

The main aim of this work is to study the respective contribution of the hard and soft blocks of a metal-ligand containing block copolymer to the self-healing behavior. To this aim, different block copolymers containing terpyridine were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. These block copolymers consisted of polystyrene as the hard block, n -butyl acrylate (BA) as soft block and terpyridine units as the ligand moiety placed at different locations in the soft block. These block copolymers were complexed with manganese(II) chloride to introduce transient crosslinks and, thus, self-healing behavior. Homopolymers with the hard and soft block only were also synthesized and tested. A quasi-irreversible crosslinking, i.e. by using nickel(II) nitrate, was performed in order to study the dynamics of the permanently (strongly) crosslinked network. Rheological master curves were generated enabling the determination of the terminal flow in these networks and the reversibility of the supramolecular interactions. Additionally, the macroscopic scratch healing behavior and the molecular mobility of the polymer chains in these supramolecular networks were investigated. A kinetic study of the scratch healing was performed to determine the similarities in temperature dependence for rheological relaxations and macroscopic scratch healing. In our previous work, we have explored the effect of strength of the reversible metal-ligand interaction and the effect of changing the ratio of hard to soft block. This work goes further in separating the individual contributions of the hard and soft blocks as well as the reversible interactions and to reveal their relative importance in the complex phenomenon of scratch healing. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel polymer binders based on dynamic radicals were developed for Si anode. • Poly(acrylic acid) was functionalized with diarylbibenzofuranone to form 3D network. • The crosslinked network structure showed a self-healing property. • Enhance mechanical and electrochemical properties were obtained. Silicon (Si), which exhibits high theoretical capacity, is a promising material for high energy density anode material in Lithium Ion Batteries (LIBs) because it is abundant in nature, inexpensive, and eco-friendly. However, Si has excessive volume expansion with charge and discharge cycles, resulting in reduced capacity reversibility and collapsing electrode structures. To overcome this limitation, polymer binders equipped with various functions have been used to improve the electrochemical performance of Si. The present study developed a self-healing cross-linked poly(acrylic acid) (PAA) binder for Si anodes functionalized with diarylbibenzofuranone (DABBF), which exhibits self-healing from reversible C-C bonding and the debonding of dynamic carbon radicals. When applied to Si anodes, the PAA-based binder functionalized with DABBF formed a three-dimensional network, stabilizing the Si structure and achieving improved adhesion and mechanical properties. Its self-healing performance enabled the Si anodes to exhibit stable capacity retention. In addition, the adhesion performance and mechanical properties of Si anodes were higher when DABBF-functionalized PAA was used as a binder. At a current density of 0.5 C, a high initial coulombic efficiency (ICE) of 77.89% was achieved, and after 500 cycles, the capacity remained high, 1774.45 mAh g−1. A novel cross-linked polymer binder with self-healing ability was successfully developed for the first time using dynamic carbon radicals, and its excellent electrochemical performance significantly improved the stability of Si anodes. [ABSTRACT FROM AUTHOR]

• Preparation of self-healable, stretchable, and printable graphene ink based on a fluid dynamic process. • Demonstration of stretchable sweat sensor showing excellent electrochemical performances with high self-healing efficiency (99%). • Demonstration of self-healing ability in real-time monitoring on-body tests of wearable device. The practical application of wearable real-time monitoring systems is currently restricted by the irreversible mechanical damage and fracture of their sensors during physical activity, which has inspired the development of self-healable ink materials. However, progress in this field is limited by the difficulty of combining high mechanical strength with high conductivity and realizing scalable and efficient fabrication. Herein, a fluid dynamics process is used to prepare a self-healable, robust, and conductive ink through the incorporation of graphene into a self-healing polymer, namely poly(1,4-cyclohexanedimethanol succinate-co-citrate). The corresponding screen-printed serpentine-structured electrode exhibits spontaneous conductivity self-healing during 10 cut-heal cycles and at a tensile strain of 200% under ambient conditions. These unique properties are used to fabricate a highly stretchable electrochemical Na+ sensor with a high self-healing efficiency (average sensitivity retention of 99%). On-body tests reveal that this wearable sensor is well suited for the real-time monitoring of sweat during physical exercise and is capable of autonomous repair after mechanical cutting, showing a healing time of ∼12 s. Thus, our work paves the way to the commercialization of devices typically requiring a combination of mechanical resilience and stable electrical performance, e.g., e-skin, sweat sensors, soft robotics, and biofuel cells. [ABSTRACT FROM AUTHOR]

The Tapered Double Cantilever Beam (TDCB) is the common specimen to study self-healing thermosetting polymers. While this geometry allows characterising the mode I fracture toughness without taking into account the crack length, the experiments show an important dispersion and unstable behaviour that must be taken into account to obtain accurate results. In this paper, finite element simulations have been used to understand the experimental behaviour. Static simulations with a stationary crack give the local stresses and the stress intensity factors at the crack tip when the TDCB is under load. In addition, the eXtended Finite Element Method (XFEM) has been used to make quasi-static crack propagation simulations. The results indicate that the crack tip has a curved profile during the propagation, advancing more at the edges than at the centre. The crack propagation begins when the applied load reaches a critical value. The unstable crack propagation noted in the experiments can be reproduced by introducing an unstable behaviour in the simulations. Finally, the sensitivity of the critical load has been studied as a function of the friction between pin and hole, tolerance of geometrical dimensions, and cracks out of the symmetric plane. The results can partially explain the dispersion of the experimental data. [ABSTRACT FROM AUTHOR]

We investigated the healing of epoxy resins with embedded ethyl phenylacetate (EPA) solvent loaded capsules and shape memory alloy (SMA) wires under fatigue loading in tapered double cantilever beam (TDCB) mode. Under cyclic loading, the kinetics of solvent diffusion are in competition with the rate of damage propagation. We showed that the active mechanism of self-healing under continuous loading is different from that in quasi-static testing. Crack arrest was observed after some initial crack growth, resulting from the diffusion of EPA solvent into the crack tip, involving local plasticization of the epoxy. Finite element analysis confirmed that the lower modulus and higher elongation at break of the solvated epoxy reduced the stresses at the crack tip. This effect combined with the well-studied microcapsule toughening effect, tremendously increased the toughness of plain epoxy. For epoxy with embedded SMA wires, completely fractured samples, healed using SMA activation, showed similar fatigue resistance as virgin samples. Furthermore, SMA activation during a 10 min break also stabilized crack progression, compared to at least 2 h needed to reach the same effect without SMA wires. [ABSTRACT FROM AUTHOR]

• A polymer with low temperature self-healing ability was developed for smart coating. • The self-healing ability was determined by Zn-urethane bonds and hydrogen bonds. • The polymer film also displays outstanding anti-icing ability. • This polymer is a highly promising for self-healable anti-icing paint. Achieving the artificial supramolecular polymer with excellent low temperature self-healing capability has been a new topic of great significance in soft robotic actuators and smart coating. Nevertheless, the production of robust polymer with decent low temperature self-healing ability is severely impeded by its high crosslink density and low dynamic crosslink bond. Here, we report a design strategy that both low crosslink density and high dynamic crosslink bonds are introduced into polyurea networks to achieve a tough and low-temperature healable supramolecular system of polypropyleneglycol (PPG)-polydimethylsiloxane (PDMS)-Zn (abbreviated as PPG-PDMS-Zn). Incorporating the long PPG segments into linear PDMS chains endows the resulting polymer with relatively low crosslink density, allowing fast polymer chains movement to unite fractured surfaces. Moreover, the dynamic characteristics and self-healing capability of the supramolecular network were effectively enhanced by combining the unique dynamic exchange feature of weak Zn-urethane coordination bonds and low temperature inhibition-dissociation effect of hydrogen bonds. As a result, the representative sample of PPG-PDMS-Zn-0.5 polymer displays a robust tensile strength of 0.98 MPa and a high self-healing efficiency of 97% at −20 °C, and these features have rarely been achieved in the previously reported materials. With these promising characters, such kind of supramolecular polymers can find wide applications in fields of anti-icing and winter anti-frosting paints, and antarctic pole exploration as well. [ABSTRACT FROM AUTHOR]

Development of sensing technology with wearable chemical sensors is realizing non-invasive, real-time monitoring healthcare and disease diagnostics. The advanced sensor devices should be compact and portable for use in limited space, easy to wear on human body, and low-cost for personalized healthcare markets. Here, we report a highly sensitive, flexible, and autonomously self-healable pH sensor cable developed by weaving together two carbon fiber thread electrodes coated with mechanically robust self-healing polymers. The pH sensor cable showed excellent electrochemical performances of sensitivity, repeatability, and durability. Spontaneous and autonomous sensor healing efficiency of the pH sensor cable was demonstrated by measuring sensitivity during four cycles of cutting and healing process. The pH sensor cable could measure pH in small volumes of real human fluid samples, including urine, saliva, and sweat, and the results were similar to those of a commercial pH meter. Taken together, successful real-time pH monitoring for human sweat was demonstrated by fabricating a wearable sensing system in which the pH sensor cable was knitted into a headband integrated with wireless electronics. • A robust and self-healing polymer was synthesized from biomass-derived and non-toxic monomers. • pH sensor cables fabricated by weaving two carbon fiber thread electrodes showed excellent potentimetric performances. • A remarkable self-healing efficiency for sensitivity of pH sensor cables with a short healing time. • Real-time monitoring capabilities of pH sensor cables for real human fluids of tear, urine, saliva, and sweat. [ABSTRACT FROM AUTHOR]