High Self-healing Efficiency Research Articles

Ultrafast, autonomous self-healable iontronic skin exhibiting piezo-ionic dynamics

The self-healing properties and ionic sensing capabilities of the human skin offer inspiring groundwork for the designs of stretchable iontronic skins. However, from electronic to ionic mechanosensitive skins, simultaneously achieving autonomously superior self-healing properties, superior elasticity, and effective control of ion dynamics in a homogeneous system is rarely feasible. Here, we report a Cl-functionalized iontronic pressure sensitive material (CLiPS), designed via the introduction of Cl-functionalized groups into a polyurethane matrix, which realizes an ultrafast, autonomous self-healing speed (4.3 µm/min), high self-healing efficiency (91% within 60 min), and mechanosensitive piezo-ionic dynamics. This strategy promotes both an excellent elastic recovery (100%) and effective control of ion dynamics because the Cl groups trap the ions in the system via ion-dipole interactions, resulting in excellent pressure sensitivity (7.36 kPa−1) for tactile sensors. The skin-like sensor responds to pressure variations, demonstrating its potential for touch modulation in future wearable electronics and human–machine interfaces.

Highly Self-Healable Polymeric Coating Materials with Enhanced Mechanical Properties Based on the Charge Transfer Complex.

Polymeric coating materials (PCMs) are promising candidates for developing next-generation flexible displays. However, PCMs are frequently subjected to external stimuli, making them highly susceptible to repeated damage. Therefore, in this study, a highly self-healing PCM based on a charge transfer complex (CTC) was developed, and its thermal, self-healing, and mechanical properties were examined. The self-healing material demonstrated improved thermal stability, fast self-healing kinetics (1 min), and a high self-healing efficiency (98.1%) via CTC-induced multiple interactions between the polymeric chains. In addition, it eliminated the trade-off between the mechanical strength and self-healing capability that is experienced by typical self-healing materials. The developed PCM achieved excellent self-healing and superior bulk (in-plane) and surface (out-of-plane) mechanical strengths compared to those of conventional engineering plastics such as polyether ether ketone (PEEK), polysulfone (PSU), and polyethersulfone (PES). These remarkable properties are attributed to the unique intermolecular structure resulting from strong CTC interactions. A mechanism for the improved self-healing and mechanical properties was also proposed by comparing the CTC-based self-healing PCMs with a non-CTC-based PCM.

Supramolecular Elastomers with Excellent Dielectric Properties and High Recyclability Based on the Coordinative Bond.

The enhancement in dielectric properties and self-healing ability for dielectric materials has been a challenging subject these years. Herein, a series of self-healed dielectric elastomers by combining the ferric ions and carboxyl-containing poly(sulfone siloxane)s is reported. Experimental results indicate the excellent dielectric properties of obtained elastomers, as the dielectric constant up to 12.8. SEM micrographs exhibit that carboxyl groups and ferric ions can aggregate together to generate clusters, which further result in interfacial polarization. Besides, high polarity dipole units including sulfonyl units and carboxyl groups contribute to dipole polarization. The overlay of the two mentioned polarization eventually results in the high dielectric property. The dielectric constant obviously increases with the contents of carboxyl groups and ferric ions. Moreover, the samples are feasible for recycling and reprocessing with high self-healing efficiency, owing to the reversibility of the coordination bond. A self-healing efficiency of 92.1% in tensile strength of the obtained samples can be reached after 2h treatment at 60 °C. And the elastomers can also conveniently recover most mechanical properties after solution treatment. This work may offer a promising method for preparing dielectric elastomers with high dielectric properties and self-healing ability.

Ultra-fast self-healable stretchable bio-based elastomer/graphene ink using fluid dynamics process for printed wearable sweat-monitoring sensor

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.

Elongated soy protein isolate-poly(D, L-lactide-co-glycolic acid) microcapsules prepared using syringe filters and their effect on self-healing efficiency of soy protein-based green resin

Self-healing soy-based resins with soy protein isolate (SPI) containing poly(D, L-lactide-co-glycolic acid) (PLGA) microcapsules (MCs) were prepared. Spherical (diameter of 1.30 μm) and elongated MCs (aspect ratios up to 20) were produced using a membrane emulsification technique using syringe filters. Self-healing efficiencies of resins were characterized for their strength recovery and toughness recovery. While both MCs could successfully heal cracks, spherical MCs were seen to compromise the tensile properties of the resin, whereas elongated MCs demonstrated some mechanical enhancement. For resins with elongated MCs, self-healing efficiencies of about 45% and 41% in terms of strength recovery and toughness recovery, respectively, were obtained. For spherical MCs, the self-healing efficiencies were even higher. However, these higher efficiencies were a result of the compromised tensile properties of the resin. The results also showed that higher MC loading results in higher self-healing efficiency. Use of self-healing green resins can extend the useful life of green composites as well as enhance their safety, thus, allowing them to replace currently used petroleum-based composites in many applications.

A novel coating with SiO2 anchored on MXene loading tannic acid for self-healing anticorrosive performance

The self-healing performance of anticorrosive coatings is critical to restoring their protective function in the event of failure to ensure durability in harsh corrosive conditions. In this work, a novel self-healing anticorrosive coating was fabricated by two-dimensional transition metal carbides and carbonitrides (MXenes) and mesoporous silica nanoparticles (MSNs) loading tannic acid (TA) as corrosion inhibitors that can effectively protect low-carbon steel from corrosion damage. The TA as corrosion inhibitors were loaded into the mesoporous silica nanoparticles, and the loading capacity reached about 71.71%. The synthesized epoxy/TA@MXene-SiO2 coating was characterized in detail using different tools. The epoxy/TA@MXene-SiO2 coating had excellent anticorrosive performance and an impedance modulus of 2.826 × 106 Ω cm2 at 0.01 Hz. The impedance modulus reached the maximum peak value of 8.585 × 106 Ω cm2 after 132 h of continuous immersion. In addition, the TA made a coating with an electrochemical self-healing efficiency of 114.27 kΩ cm2 h−1. This work provides insight into the novel design of anticorrosive coatings with excellent anticorrosive performance and high self-healing efficiency.

Surface Chelation Enabled by Polymer-Doping for Self-Healable Perovskite Solar Cells.

Polymer doping is an efficient approach to achieve self-healing perovskite solar cells. However, achieving high self-healing efficiency under moderate conditions remains challenging. Herein, an innovative self-healable polysiloxane (PAT) containing plenty of thiourea hydrogen bonds was designed and introduced into perovskite films. Abundant thiourea hydrogen bonds in PAT facilitated the self-healing of cracks at grain boundaries for damaged SPSCs. Importantly, the doped SPSCs demonstrated a champion efficiency of 19.58% with little hysteresis, almost rivalling those achieved in control atmosphere. Additionally, owing to the effective chelation by PAT and good level of thiourea hydrogen bonds, after 800 cycles of stretching, releasing and self-healing, the doped SPSCs retained 85% of their original IPCE. The self-healing characteristics were demonstrated in situ after stretching at 20% strain for 200 cycles. This strategy of pyridine-based supramolecular doping in SPSCs paves a promising way for achieving efficient and self-healable crystalline semiconductors.

Double-Network Luminescent Films Constructed Using Sulfur Quantum Dots and Lanthanide Complexes.

Although UV light-switchable luminescent films are of importance for application in soft optical devices and anticounterfeiting labels, there are still challenges in developing such films integrated with outstanding luminescent property, high self-healing efficiency, and simultaneously excellent mechanical strength. Herein, double-network (DN) luminescent films are designed and constructed via an intermolecular hydrogen bond crosslinking strategy of poly(ethylene glycol) (PEG) in sulfur quantum dots (S-QDs) and polyurethane (PU), where S-QDs ("stone" one) play dual roles of acting both as a soft segment to crosslink another segment PU ("bird" one) and also as the origin of a luminescence center ("bird" two) in films. In addition, lanthanide(III) complexes (LnCs, Ln═Eu3+, Tb3+) are employed as another emission source to embed in the films and switch the emission colors of DN films from the multicolor (red-yellow-green) of LnCs to the blue color of S-QDs by changing the ultraviolet excitation wavelength from 254 to 365 nm. It is worth noting that the crosslinking network strategy can effectively prevent S-QDs and LnCs from aggregating or leaking and enable both luminescence centers to homogeneously distribute, resulting in luminescent DN films possessing extraordinary UV light-switchable luminescence, improved mechanical property, and excellent self-healing ability. This work presents a viable method for the design and fabrication of luminescent films with multifunctional applications in flexible robotics, wearable devices, and dual-luminescent anticounterfeiting materials.

A Comparative Study on the Self-Healing Characterizations and Formulation Optimization of Polyurea Coating.

Self-healing materials, especially self-healing polyurea/polyurethane, to replace traditional coating has been of increasing interest in the past decade. The frequency of regular maintenance work can also be reduced as the coating is capable of forming bonds at ruptured sites. This reduces the cost of maintenance and the risk involved in workers engaging in maintenance work. The extremely short curing time of polyurea coating could potentially outweigh the cost due to its short down time. With a high self-healing efficiency, self-healing polyurea could be the ultimate choice of protective coating. This report aims to find the optimum formulation for fabrication of polyurea with a high self-healing efficiency. This is conducted by changing the composition of the components chosen for formulation of polyurea. The choice of isocyanate and amine is varied to explore its impact on chain mobility and microphase separation, which are important factors affecting self-healing efficiency. A series of characterizations, including ATR-FTIR, DSC, optical microscope and mechanical tester, is used to analyze the factors affecting the self-healing efficiency of fabricated polyurea and to eventually determine the best formulation. The ideal formulation of toluene 2,4 diisocyanate-amine (TDI-P1000) polyurea managed to achieve a self-healing of 42%. Further studies could be done to include multiple healing mechanisms after different area of polyurea to boost its self-healing efficiency after repeated healing.

Room-temperature self-healing supramolecular polyurethanes based on the synergistic strengthening of biomimetic hierarchical hydrogen-bonding interactions and coordination bonds

Developing a new generation of polymeric materials that integrate robust mechanical properties with ultra-high self-healing efficiency at ambient temperature remains a formidable challenge due to the proverbial trade-offs among strength, toughness, and self-healing ability. Herein, inspired by biological systems (titin protein molecular structure and Nereis jaws), a series of updated supramolecular polyurethanes have been successfully synthesized by incorporating hierarchical hydrogen-bonding motifs into the polymer matrix and subsequently coordinated with Zn2+ ions. Relying on collaborative reinforcement of optimized hierarchical hydrogen bonds and metal-ligand coordination bonds, the resulted supramolecular elastomers exhibited a robust strength of ∼14.15 MPa, an excellent toughness of ∼47.57 MJ m−3, and Young’s modulus of ∼146.92 MPa. Benefiting from the rational design of hard domains, high mobility of chains, and the synergistic effect of multiple non-covalent interactions, the mechanical properties are far superior to the previously reported room‐temperature self‐healing materials. In addition, with the structural design of “inner soft and external hard” model, we also fabricated a bilayer polymer film with a gradient distribution that can achieve rapid self-healing, with an unexpectedly high self-healing efficiency of 95% at ambient temperature in 24 h. This work opens up a new avenue for fabricating room-temperature self-healing materials with robust mechanical strength and toughness at the same time.

Self-healable, super-stretchable and shape-adaptive triboelectric nanogenerator based on double cross-linked PDMS for electronic skins

Self-powered triboelectric nanogenerators (TENG) have shown great potential in the field of electronic skin (E-skin). However, TENG is vulnerable to damage by frequent mechanical impacts during operation. In this work, a self-healable (≤ 2 h), super-stretchable (> 760%) and shape-adaptive TENG was designed as an E-skin to harvest energy and monitor human motion. The triboelectric layer is self-healing double-crosslinked polydimethylsiloxane (PDMS) prepared by adjusting the ratio of imine bonds to hydrogen bonds (H-bonds). The electrode layer is self-healable conductive composite prepared via the formation of H-bonds between MXene and lightly cross-linked PDMS. This TENG can be perfectly attached on the uneven human skin surface due to shape adaptability and can maintain original triboelectric performance after repeated damage. Also, our TENG can switch freely between single sensor and sensor arrays due to high self-healing efficiency, suggesting promising applications in E-skin and wearable device.

A cellulose nanofibril-reinforced hydrogel with robust mechanical, self-healing, pH-responsive and antibacterial characteristics for wound dressing applications

BackgroundBacterial infection in wounds has become a major threat to human life and health. With the growth use of synthetic antibiotics and the elevated evolution of drug resistant bacteria in human body cells requires the development of novel wound curing strategies. Herein, a novel pH-responsive hydrogel (RPC/PB) was fabricated using poly(vinyl alcohol)-borax (PB) and natural antibiotic resveratrol grafted cellulose nanofibrils (RPC) for bacterial-infected wound management.ResultsIn this hydrogel matrix, RPC conjugate was interpenetrated in the PB network to form a semi-interpenetrating network that exhibited robust mechanical properties (fracture strength of 149.6 kPa), high self-healing efficiency (> 90%), and excellent adhesion performance (tissue shear stress of 54.2 kPa). Interestingly, the induced RPC/PB hydrogel showed pH-responsive drug release behavior, the cumulative release amount of resveratrol in pH 5.4 was 2.33 times than that of pH 7.4, which was adapted well to the acidic wound microenvironment. Additionally, this RPC/PB hydrogel exhibited excellent biocompatibility and antioxidant effect. Moreover, in vitro and in vivo results revealed that such RPC/PB hydrogel had excellent antibacterial, skin tissue regeneration and wound closure capabilities.ConclusionTherefore, the generated RPC/PB hydrogel could be an excellent wound dressing for bacteria-infected wound healing.

A nanosheets-polyborosiloxane composite impregnated with shorter hydrogen-bonding clusters achieves combination of self-healing, shapeability and high-barrier properties

Self-healing polymers have been extensively studied, however, challenges remain in cooperating processability and functionality for practical applications. Here, we present a facile method to fabricate a nanocomposite by constructing intercoupling short hydrogen-bonding clusters between polyborosiloxane (PBS) and l -cystine modified MMT nanosheets (LMMT) to produce both weak entanglement and interfacial interaction. At ambient conditions, the resultant nanocomposite simultaneously achieves preferable rheological dynamics, short self-healing time and higher self-healing efficiency (∼99.48% in 10 min), remarkable barrier properties (water vapor permeability ∼4.74 × 10 −11 g m/(m 2 ·s·pa)) even after repeated damage-healing cycles, which overturns the previous understanding of conventional self-healing composites where self-healing, shapeability and high-barrier performances are mutually exclusive. Moreover, such nanostructure characterize enables the self-sealing ability applying in the substance-preserving function. This work provides fundamental insight for designing and developing multi-function materials for self-sealing packaging application. • Facile preparation method of PBS/LMMT composite combined with room-temperature shapeability, self-healing and barrier properties. • Shorter hydrogen-bond cluster of LMMT results in improving a stable interfacial interaction and creating a weak entanglement. • The short layer spacing of LMMT endows the composites with room-temperature formability. • Providing a newly method and material of in-situ self-sealing for substance-preserving packaging.

Healable, recyclable and mechanically robust elastomers with multiple dynamic cross-linking bonds

The cross-linked network structure bestows rubber with excellent mechanical properties, but it greatly limits the self-healing and reprocessing ability of rubber. Herein, to address the above problem, we propose a simple cross-linking strategy with the cross-linker consisting of triple dynamic covalent bonds to vulcanize epoxidized natural rubber (ENR). A dynamic covalent network remarkably enhanced the mechanical properties of ENR through the combination of dynamic covalent bonds in the cross-linked network. At the same time, abundant dynamic covalent bonds rearranged the network topology through reversible exchange. As a result, a novel self-healing ENR with high tensile strength (2.06 ± 0.12 MPa) has been successfully developed. The ENR exhibits a high (97 ± 3%) self-healing efficiency (after 30 h at 70 °C) without applying any external force. Furthermore, it can be recycled more than three times. This work could enlighten researchers in academia and industry to develop self-healing elastomers with mechanical strength and reprocessing ability. • A novel cross-linker containing triple dynamic covalent bonds was synthesized. • Triple dynamic covalent bonds is simultaneously introduced into the cross-linked network. • The covalent cross-linking driven by dynamic covalent bonds reinforce the mechanical properties of rubber. • Reversible interactions enable the self-healing ability and recyclability of rubber.

Simultaneously optimized healing efficiency and mechanical strength in polymer composites reinforced by ultrahigh loading fillers based on interfacial energy and dynamic disulfide bonds

In general, ultrahigh loading fillers can increase the hardness and hinder the interfacial healing progress in polymer composites. Therefore, the healing ability and mechanical strength of polymer composites with ultrahigh filler loading are contradictory properties and are difficult to optimize simultaneously. Herein, self-healing hard polymer composites consisting of 72.4 vol% fillers and self-healing thermoplastic elastomers based on surface energy and disulfide bonds were fabricated. The results showed that in the case that of ultrahigh filler loading, polymer composites not only obtained a high mechanical strength of ∼3.21 MPa and a high self-healing efficiency of ∼92.8%, but also possessed the strong reshape ability. Besides, a physical model was used to describe the self-healing mechanism. The adhesion effectively closed cracks and the surface energy driven the movement of polymer chains as well as disulfide bonds reconstructed new polymer chains at the interfaces, resulting in recovering heal mechanical property. • Self-healable polymer composites with ultrahigh loading fillers were prepared. • The maximum healing efficiency and mechanical strength reached 92.8% and 3.21 MPa. • The physical model was used to describe healing mechanism in detail.

Highly conductive self-healing polymer electrolytes based on synergetic dynamic bonds for highly safe lithium metal batteries

Self-healing polymer electrolytes can improve the safety, reliability and cycle life of the batteries. Herein,we developed a self-healing polymer electrolyte (IBshPE) with high ionic conductivity and excellent self-healing property. IBshPE cross-linked by synergetic dynamic imine bond and boroxine bond was prepared via the reaction of 2-formylphenylboronic acid and poly(ethylene glycol) diamine. In IBshPE, boroxine bonds with B-N coordination and imine bonds can synchronously undergo fast bond exchange reactions, enabling rapid self-healing of IBshPE. IBshPE shows high self-healing efficiency of 97% within 4 h. The healed IBshPE has nearly the same mechanical property and ionic conductivity as the original IBshPE. IBshPE exhibits the highest ionic conductivity (5.08 × 10−3 S cm−1 at 30 °C) among the reported self-healing polymer electrolytes. IBshPE facilitates the construction of robust LiF-rich SEI and efficiently inhibits dendrite growth. LiFePO4/Li cells with IBshPE exhibits excellent cycle performance (capacity retention of 98.6% after 80 cycles) and good rate capability (specific capacity of 130.5 mAh g−1 at 2C rate). More importantly, IBshPE is capable of self-repairing damage in the LiFePO4/Li cells and restoring the performance of the cells, thus effectively enhancing the reliability and safety of the battery.

Biodegradable Natural Rubber Based on Novel Double Dynamic Covalent Cross-Linking.

In this paper, biodegradable epoxidized natural rubber containing cyclic carbonate groups (CNR) was prepared by the reaction between epoxidized natural rubber (ENR) and carbon dioxide. Dynamic disulfide bonds and a boronic ester structure were successfully constructed and then the cross-linking network was formed by the thermally initiated “click” reaction between thiol groups of the cross-linker and the residual epoxy groups of ENR. As a result of the exquisite double dynamic covalent structure, the material exhibits high self-healing efficiency. Moreover, by virtue of the cyclic carbonate structure of the CNR, the natural rubber was confirmed to be biodegradable according to the biodegradable measurement. To the best of our knowledge, natural rubber with biodegradable and self-healing characteristics was obtained for the first time.

Blending polar rubber with polyurethane to construct self-healing rubber with multiple hydrogen bond networks

Preparation of traditional rubbers with excellent self-healing ability is a difficult issue in the field of polymer materials. In the current work, we proposed a new way to fabricate self-healing traditional rubber by blending the polar rubber (epoxidized natural rubber, ENR) with the other polar polymer (polyurethane, PU) containing CC bonds and 2-ureido-4[1H]-pyrimidinone (UPy) groups (PU-UPy). It was demonstrated that the ENR/PU-UPy blend exhibits high self-healing efficiency. During curing, slightly covalent network forms in the blend, which is beneficial for the improvement in the compatibility between the two polymers. Multiple hydrogen bond networks including intermolecular hydrogen bonds between the ENR chains and the PU-UPy chains and strong hydrogen bonds between the UPy groups determine the excellent self-healing ability of the blend. The current blending method provides new ideas for the design of new self-healing traditional elastomers.

Biobased Reversible Cross-Linking Enables Self-Healing and Reprocessing of Epoxy Resins

The rapid development of thermosetting polymers contributes strongly to environmental pollution, petrochemical resource consumption, and increasing carbon dioxide emission. Introducing a reversible supramolecular cross-linking network into the thermosetting polymer to endow it with reprocessability and self-healing ability is highly attractive for the reduction of fossil fuel consumption. Despite the tremendous advancement in recyclable thermosetting polymers, using biobased materials to construct reversible cross-links, which can realize the high biomass carbon content of materials, remains challenging. Here, we present a self-healing and reprocessable epoxy resin enabled by biobased multiple hydrogen bonds between biological tannic acid and chitosan. The binding energy simulation demonstrates that effective hydrogen bonds are constructed in the epoxy resin. The resultant supramolecular cross-linked epoxy resin shows improved mechanical properties (tensile strength increased by two times, toughness increased by 2.7 times), high self-healing efficiency (104% toughness recovery) at room temperature, and excellent reprocessability (109% toughness recovery). We envision that the proposed biobased reversible cross-linking strategy will be useful in the greening and recycling of various thermosetting polymers, such as rubbers, cross-linked plastics, etc.

Self-powered multi-color display based on stretchable self-healing alternating current electroluminescent devices

Multi-color displays enabled with self-powering capability possess unique superiority in information communications for the internet of things (IoT). Here, we present a novel self-powered self-healing multi-color display by integrating the intrinsically stretchable multi-color alternating current electroluminescent (ACEL) devices with the triboelectric nanogenerators (TENGs). By introducing the reversible dynamic imine bonds, PDMS is empowered with superb stretchability (2500%) and high self-healing efficiency (96%) under room temperature. With such stretchable and self-healing PDMS (SSH-PDMS) as the substrate of electrodes and the matrix of emission layers, intrinsically stretchable and self-healing ACEL (SSH-ACEL) devices are fabricated. The self-powered multi-color ACEL display is demonstrated by assembling the modules of SHH-ACEL devices with typical contact-separation mode TENGs. This work may provide a widely adaptable platform for self-powered communication in IoT.