Self-healing Materials Research Articles

Light- and heat-induced shape deformation polyurethane actuators that combine self-healing capabilities

Materials commonly experience physical damage during regular usage, and the implementation of self-healing materials can effectively repair this damage, thereby prolonging the lifespan of the materials. We have successfully synthesized a polyurethane material, S-PU, by introducing azobenzene and reversible disulfide bonds through co-polymerization. The S-PU film not only exhibits light-induced bending, heat-induced recovery ability, but also good self-healing properties. The disulfide bonds in S-PU accelerate the dynamic exchange as the polymer chains flow under heated conditions, enabling self-repairing without affecting the mechanical properties of the material. S-PU is a self-repairing material that can repair damage in a variety of ways. By combining dual-stimulus response characteristics with self-healing properties, this work provides a new idea for self-healing materials and opens more directions for the practical application of the material.

Characteristic of AMPS-Based Self-Healing Material and the Effect on the Properties of Oil Well Cement Slurry

Characteristic of AMPS-Based Self-Healing Material and the Effect on the Properties of Oil Well Cement Slurry

Review on the Encapsulation, Microencapsulation, and Nano- Encapsulation: Synthesis and Applications in the Process Industry for Corrosion Inhibition

Background: Surfaces of materials often corrode and deteriorate due to environmental conditions. There are various widely used methods of reducing corrosion rates to increase the lifetime of materials and equipment. Recently, there has been a growth in the use of nanotechnology to protect metals against corrosion. The application of nano-encapsulation techniques in the process industry is one of the important eras of nanotechnology. This review paper focuses on encapsulation, microencapsulation, and nano-encapsulation methods, emphasizing nanoencapsulation applications as corrosion inhibitions in the process industry. Methods: Materials based on the self-healing mechanism were used in advanced applications such as structures, batteries, and coatings. These technologies may be studied in two ways: compounds with intrinsic self-healing properties and extrinsic self-healing materials with additives such as microcapsules filled with healing agents. Nano-coatings have advantages, like accelerated ground hardness, adhesive energy, long-time period and/or high-temperature corrosion resistance, tribological residence enhancement, etc. Nano-coatings can also be carried out in thinner and smoother layers, considering flexibility, accelerated performance, decreased fuel costs, and smaller carbon footprints, as well as occasional maintenance. The review of corrosion characteristics of polymeric nanocomposite material was discussed in this paper. Results: This review paper presents an updated overview summarizing the latest advances in the various micro/nanocarriers used for self-healing corrosion protective coatings. Conclusion: With this information, the investigators will be able to modify the structure of the inhibitor to get the necessary corrosion inhibition capabilities. The need for a physical examination is rising as a result.

Fabrication of photothermal responsive dual-chamber microcapsules for self-healing epoxy anticorrosion coatings

It has been urgent that timely repair of microdamage generated during long-term service of metal insulation coatings. Hereby, we developed a novel self-healing dual-chamber microcapsule with particle size about 5 μm, in which furfuryl amine modified polystyrene-acrylic acid (PSAF) as shell material and photosensitizer Carbon dots (CDs) as Pickering emulsifier. The synthesized materials were characterized analytically, FTIR and DSC demonstrated the simultaneously existence of healing agent and curing agent in the resultant dual-chamber microcapsule. Experiments also showed microcapsules exhibited satisfying storage stability more than 20 d at room temperature as well as thermogenesis effect that allowing temperature of epoxy composite materials raised to 50 °C in 60s and fractures to be effectively minimized in time. The scratch tensile measurement results demonstrated that epoxy resin composites incorporated with 2 wt% microcapsules exhibited the optimal strength self-healing efficiency, modulus, toughness and anti-fatigue performance. Furthermore, surface characterization and EIS analysis also confirmed the long-lasting healing effect of EP/MC2% complex coating with outstanding corrosion resistance. Therefore, the photothermal responsive dual-chamber microcapsule designed in this work has application as self-healing material especially epoxy anti-corrosion coating.

Self-Healable Multifunctional Fibers via Thermal Drawing.

The development of soft electronics and soft fiber devices has significantly advanced flexible and wearable technology. However, they still face the risk of damage when exposed to sharp objects in real-life applications. Taking inspiration from nature, self-healable materials that can restore their physical properties after external damage offer a solution to this problem. Nevertheless, large-scale production of self-healable fibers is currently constrained. To address this limitation, this study leverages the thermal drawing technique to create elastic and stretchable self-healable thermoplastic polyurethane (STPU) fibers, enabling cost-effective mass production of such functional fibers. Furthermore, despite substantial research into the mechanisms of self-healable materials, quantifying their healing speed and time poses a persistent challenge. Thus, transmission spectra are employed as a monitoring tool to observe the real-time self-healing process, facilitating an in-depth investigation into the healing kinetics and efficiency. The versatility of the fabricated self-healable fiber extends to its ability to be doped with a wide range of functional materials, including dye molecules and magnetic microparticles, which enables modular assembly to develop distributed strain sensors and soft actuators. These achievements highlight the potential applications of self-healable fibers that seamlessly integrate with daily lives and open up new possibilities in various industries.

Combining Siloxane-Based polybenzoxazine with Poly(ethylene-co-vinyl acetate/hydroxyl) for tougher, more Stable, and Self-Healable materials

Cross-linked EVOH containing dynamic silyl ether bonds with improved toughness and processability have been prepared by taking advantage of both ethylene vinyl alcohol (EVOH) and benzoxazine chemistry. For that, the cross-linked EVOH was synthesized through a trans etherification reaction between siloxane mono-functional benzoxazine and pendant hydroxyl groups on ethylene vinyl alcohol (EVOH) copolymer. The precursor EVOH copolymer was obtained by hydrolysis of the commercially available and inexpensive ethylene–vinyl acetate copolymer (EVA). The chemical structures of polymers were analyzed by proton nuclear magnetic resonance (1H NMR) spectra and Fourier transform infrared (FTIR) spectroscopy. The curing and thermal stability were researched by using differential scanning calorimetry (DSC) and a thermogravimetric analyzer (TGA), respectively. The mechanical properties via the stress–strain analysis were examined to identify the effect of the benzoxazines with the silyl ether group on the toughness and self-healing ability of the modified EVOH.

Heterogeneous and Cooperative Rupture of Histidine-Ni2+ Metal-Coordination Bonds on Rationally Designed Protein Templates.

Metal-coordination bonds, a highly tunable class of dynamic noncovalent interactions, are pivotal to the function of a variety of protein-based natural materials and have emerged as binding motifs to produce strong, tough, and self-healing bioinspired materials. While natural proteins use clusters of metal-coordination bonds, synthetic materials frequently employ individual bonds, resulting in mechanically weak materials. To overcome this current limitation, we rationally designed a series of elastin-like polypeptide templates with the capability of forming an increasing number of intermolecular histidine-Ni2+ metal-coordination bonds. Using single-molecule force spectroscopy and steered molecular dynamics simulations, we show that templates with three histidine residues exhibit heterogeneous rupture pathways, including the simultaneous rupture of at least two bonds with more-than-additive rupture forces. The methodology and insights developed improve our understanding of the molecular interactions that stabilize metal-coordinated proteins and provide a general route for the design of new strong, metal-coordinated materials with a broad spectrum of dissipative time scales.

Superior strength, highly stretchable, bionic self-healing polyurethane and its composites for flexible conductivity and self-cleaning applications

Balancing the exceptional mechanical strength and repair efficiency of self-healing materials presents a significant challenge to unlocking their full potential in practical applications. Inspired by natural spider silk and cartilage, multiple dynamic hydrogen bonds were introduced into the pre-prepared polyurethane (PU). Then modifided graphene oxide (GO) nanosheets with dynamic hydrogen bonds were added into the prepared PU to form composites (AU-PU/GDU) to establish a dense hydrogen bond network structure, providing strong interfacial interactions. The AU-PU/GDU film exhibits excellent tensile strength (39.6 MPa), high elongation at break (1155.6 %), and outstanding repair efficiency (90.3 %). Using AU-PU/GDU as the flexible base, a superhydrophobic conductive composite coating (F-AU-PU/GDU) with a contact angle greater than 150° was prepared by incorporating superhydrophobic nanomaterials. This work lays the foundation for the development of multifunctional materials through the creation of self-healing superhydrophobic conductive composite coatings, which have a wide range of potential applications.

Uncovering the Recent Progress of CNC-Derived Chirality Nanomaterials: Structure and Functions.

Cellulose nanocrystal (CNC), as a renewable resource, with excellent mechanical performance, low thermal expansion coefficient, and unique optical performance, is becoming a novel candidate for the development of smart material. Herein, the recent progress of CNC-based chirality nanomaterials is uncovered, mainly covering structure regulations and function design. Undergoing a simple evaporation process, the cellulose nanorods can spontaneously assemble into chiral nematic films, accompanied by a vivid structural color. Various film structure-controlling strategies, including assembly means, physical modulation, additive engineering, surface modification, geometric structure regulation, and external field optimization, are summarized in this work. The intrinsic correlation between structure and performance is emphasized. Next, the applications of CNC-based nanomaterials is systematically reviewed. Layer-by-layer stacking structure and unique optical activity endow the nanomaterials with wide applications in the mineralization, bone regeneration, and synthesis of mesoporous materials. Besides, the vivid structural color broadens the functions in anti-counterfeiting engineering, synthesis of the shape-memory and self-healing materials. Finally, the challenges for the CNC-based nanomaterials are proposed.

Self-healing coatings for large-scale damages via ultrahigh load capacity of healing agents in short kapok microtubules

Self-healing materials, due to their ability to autonomously repair damages, have been extensively applied in the field of metal corrosion protection. However, prior self-healing coatings are powerless against large-scale damages limited by their relatively low amounts of prestored self-healing agents in microcontainers, which severely restricts their long-term anticorrosion performance. Herein, to address this issue, we propose a simple strategy to prestore a water-soluble cerium-based corrosion inhibitor, cerium gluconate, into Kapok fibers through a cyclic process of vacuum drying after saturation with the inhibitor solution, and the load capacity of cerium gluconate in Kapok (CG@K) by this approach can reach up to 455 wt%. This new loading system is relatively easy to be carried out while give an ultrahigh load capacity, and applicable to encapsulate other healing agents theoretically. The Kapok fibers embedded uniformly in the self-healing coatings exhibit a dense three-dimensional network structure, which, along with the ultra-high loading content, renders the self-healing coatings distinguished corrosion resistance. It is worth noting that the self-healing coatings achieve a remarkable ability to autonomously repair large-scale cracks up to 400 μm. This work provides an option for fabricating high agent load capacity and shows tremendous potential for designing self-healing coatings for large-scale damages.

Autonomous Underwater Self-Healable Adhesive Elastomers Enabled by Dynamical Hydrophobic Phase-Separated Microdomains.

High-efficient underwater self-healing materials with reliable mechanical attributes hold great promise for applications in ocean explorations and diverse underwater operations. Nevertheless, achieving these functions in aquatic environments is challenging because the recombination of dynamic interactions will suffer from resistance to interfacial water molecules. Herein, an ultra-robust and all-environment stable self-healable polyurethane-amide supramolecular elastomer is developed through rational engineering of hydrophobic domains and multistrength hydrogen bonding interactions to provide mechanical and healing compatibility as well as efficient suppression of water ingress. The coupling of hydrophobic chains and hierarchical hydrogen bonds within a multiphase matrix self-assemble to generate dynamical hydrophobic hard-phase microdomains, which synergistically realize high stretchability (1601%), extreme toughness (87.1MJm-3), and outstanding capability to autonomous self-healing in various harsh aqueous conditions with an efficiency of 58% and healed strength of 12.7MPa underwater. Furthermore, the self-aggregation of hydrophobic clusters with sufficient dynamic interactions endows the resultant elastomer with effective instantaneous adhesion (6.2MPa, 941.9Nm-1) in extremely harsh aqueous conditions. It is revealed that the dynamical hydrophobic hard-phase microdomain composed of hydrophobic barriers and cooperative reversible interactions allows for regulating its mechanical enhancement and underwater self-healing efficiency, enabling the elastomers as intelligent sealing devices in marine applications.

Νovel Polylactic Acid/Tetraethyl Citrate Self-Healable Active Packaging Films Applied to Pork Fillets' Shelf-Life Extension.

Nowadays, increased food safety and decreased food waste are two of the major global interests. Self-healable active packaging materials are an attractive option to achieve such targets. This property is critical for the hygiene and the consumption appropriateness of the food. Polylactic acid is a very promising polymeric matrix that potentially could replace the widely used low-density polyethylene due to its biobased origin and its easy biodegradable nature. The main drawback of this polymeric matrix is its brittle, fragile nature. On the other hand, tetraethyl citrate is a biobased approved food additive which became an attractive option as a plasticizer for industries seeking alternative materials to replace the traditional petrochemically derived compounds. A novel biobased film exhibiting self-healing behavior suitable for food-active packaging was developed during this study. Polylactic acid's brittleness was reduced drastically by incorporating tetraethyl citrate, and a random cut on the original self-repairing film was fully healed after 120 s. The optimum concentration of tetraethyl citrate in the polylactic acid was around 15% v/w with a water/oxygen barrier close to the relevant of polylactic acid and low migration. According to the EC50 parameter, the antioxidant activity was 300% higher than the relevant of pure polylactic acid, while according to the thiobarbituric acid and heme iron parameters, the film resisted lipid oxidation and deterioration. Finally, the total viable count parameter indicates the strong antimicrobial activity of this sample.

Stability of Ti3C2-MXene/Waterborne polyurethane composite emulsion and investigation of visible light-driven film self-healing performance

Intrinsic self-healing waterborne polyurethane (WPU) is an environmentally friendly, economically viable, and practical novel intelligent material. However, the key to achieving practical applications lies in the remote activation of repair in self-healing materials and the excellent mechanical properties of the matrix. In this study, we introduce quadruple hydrogen bonding in the polyurethane backbone. We have incorporated a novel two-dimensional sheet-like material, MXene, to achieve visible light remote-driven self-healing of material hydrogen bonds while enhancing the material’s mechanical properties. By utilizing the MXene supernatant, this approach not only resolves the issues of poor stability and easy sedimentation of MXene nanosheets in water-based polymers but also helps to prevent resource wastage. Our research results demonstrate that the composite film exhibits a tensile strength of 6.55 MPa and a fracture elongation of 604%. Additionally, quadruple hydrogen bonds in the WPU chains enable rapid self-healing of microcracks under visible light irradiation at 300 mW/cm2, with complete disappearance within 80 min.

Self-healable PVA-Borax-K2SO4 hydrogel electrolyte for flexible symmetric supercapacitors

The self-healing hydrogel materials are formed from the reaction between polyvinyl alcohol (PVA) and sodium tetraborate (Borax). The O-B-C vibration peak from the FT-IR spectrum is used to confirm the formation of the self-healing hydrogel structure. With 0.5 M concentration K2SO4, the resistivity of PVA-Borax-K2SO4 material is evaluated by Bode cure and obtained at 4.13 Ω.cm. With the improvement in hybrid structure, the flexible supercapacitor (FSS) devices were fabricated from two carbon fiber fabrics as symmetric electrodes with a self-healing hydrogel material (PVA-Borax-K2SO4) as electrolyte and separator. The electrochemical performances of flexible symmetric supercapacitor (FSS) devices are measured by cyclic voltammetric, charge/discharge, and impedance tests. The specific capacitance of FSS obtained 1.725 mF/cm2 at 0.05 mA/cm2 discharge current. Moreover, the stability of the FSS device attained confirmation by the comparison of the specific capacitance at 2 and 50 cycles.

A Pollution Barrier Self-Healing Material: Investigating the Effect of Individual Components on Its Performance and Determining Optimal Ratios and Healing Compositions

A Pollution Barrier Self-Healing Material: Investigating the Effect of Individual Components on Its Performance and Determining Optimal Ratios and Healing Compositions

Modified Bacteria Incorporated Geopolymer - A Qualitative Approach for an Eco-friendly, Energy-efficient and Self-healing Construction Material

Cement production consumes huge energy and creates environmental pollution. Cracks present in the cement-based concretes, deteriorate the structural longevity and requires costly repair. An eco-friendly and energy-efficient geopolymeric material is developed by incorporating modified bacterium cells, assuming that the developed material will be a cement-alternatives in construction industries in near future. Transformed Bacillus subtilis cells is incorporated to the alkali-activated fly ash only (100%) for making the geo-polymeric material. The mortar samples prepared by geopolymeric material are cured under various conditions to achieve the best possible energy-efficient curing process. Simulated cracks on mortars are developed by applying 50% (half) of predetermined breaking load for studying the self-healing phenomenon. Artificial cracks on mortars are created by introducing steel bar for studying crack-repairing activity. Mechanical strengths (compressive, tensile and flexural), water permeability, sulfate and chloride resistant activities along with the crack-repairing and the self-healing efficacy of the samples are characterized. Higher mechanical strengths and better longevity in terms of decreased water and chloride ions permeability and increased sulfate resistant activity are noted in the bacterium amended mortars. Ambient temperature modified heat curing process reveals the best possible energy-efficient curing condition. Images and micro-structures analyses show that several new phases (e.g., silicate, mullite, albite and alite etc.) are developed within the bacteria-amended mortars. Eco-friendliness of the bacterium is confirmed by toxicity study against rats models and human cell lines. We hypothesize that the developed geo-polymeric material is a suitable cement alternative in construction industries as well as an eco-friendly and energy efficient material.

Dual Microcapsules Encapsulating Liquid Diamine and Isocyanate for Application in Self-Healing Coatings

Dual microcapsule systems, especially those based on the polyurea matrix, have emerged as pivotal components driving innovation in self-healing materials, thanks to the intrinsic properties of polyurea, primarily diamine and diisocyanate, rendering it an optimal choice for enhancing self-healing coatings. However, the encapsulation of polyurea components is fraught with substantial technical hurdles. Addressing these challenges, a novel methodology has been devised, leveraging n-heptane as a solvent in the liquid diamine emulsion process to facilitate the synthesis of diamine microcapsules. These microcapsules exhibit a uniform spherical morphology and a robust shell structure, with an encapsulated core material ratio reaching 39.69%. Analogously, the encapsulation process for diisocyanate has been refined, achieving a core material percentage of 10.05 wt. %. The integration of this bifunctional microcapsule system into diverse polymeric matrices, including epoxy resins and polyurethanes, has been demonstrated to significantly enhance the self-healing efficacy of the resultant coatings. Empirical validation through a series of tests, encompassing scratch, abrasion, and saltwater immersion assays, has revealed self-healing efficiencies of 21.8% and 33.3%, respectively. These results indicate significant improvements in the durability and self-repair capability of coatings, marking a notable advancement in self-healing materials with promising potential for tailored applications in automotive, aerospace, and construction industries.

Self-healing epoxy coatings via microencapsulation of aromatic diisocyanate in lignin stabilized Pickering emulsions

Isocyanate-filled microcapsules are gaining increased attention for their role in developing self-healing materials, thereby reducing maintenance costs and increasing polymer durability. Nevertheless, microencapsulating highly reactive -NCO groups remains a challenging task in the literature. Likewise, considerable efforts have been directed towards developing polymers from renewable and biobased sources, which could also be applied to microcapsule synthesis. In this work, lignin, an abundant biopolymer, was used as a solid stabilizer for oil-in-water (O/W) interfaces, enabling the encapsulation of highly reactive isocyanate. Hybrid polyurethane/polyurea microcapsules containing reactive methylenediphenyl diisocyanate (MDI) were obtained via optimized O/W Pickering emulsions using lignin for system stabilization. This optimized process facilitated shell formation via the reaction of diisocyanate with lignin and water, eliminating the need for additional chain extenders. Scanning electron microscopy revealed the formation of spherical and rough microcapsules, while infrared spectroscopy confirmed the presence of residual free -NCO groups, indicating effective encapsulation of MDI. Additionally, a core -NCO concentration of 11 wt% was confirmed by titration. The microcapsules were further assessed as components in self-healing epoxy coatings. Their incorporation resulted in the retardation of corrosion on a low carbon steel panel after 72 h of submersion in a saline solution. Electrochemical impedance spectroscopy (EIS) confirmed a significant increase of approximated 620% in impedance modulus after 83 days of immersion in a 3.5 wt% NaCl solution, compared to the neat epoxy coating. These findings suggest a promising technological application of this material for the advancement of self-healing epoxy-based coatings and composites.

Robust, self-healing AIE fluorescent supramolecular elastomers for smart anti-counterfeiting

Providing aggregation-induced emission (AIE) polyurethane with self-healing capability can increase the lifetime of the material and adapt it to multiple application scenarios, which is a huge challenge in the development of luminescent smart materials. Herein, a range of transparent fluorescence polyurethanes (FPUs) with prominent strength were designed and synthesized. The optimization of robust FPUs exhibits outstanding mechanical performance (33.5 MPa tensile strength, 120.2 MJ m−3 toughness) and self-healing ability (88.9 %, at 80 °C for 2 h). Furthermore, the aggregation of tetraphenylethylene structure in the hard segment causes the system to emit bright blue fluoresence. We successfully screen-printed designable patterns on the self-healing polyurethane substrates. The concealed patterns self-repair after damage, and can be clearly and robustly displayed under 365 nm light irradiation. The as-prepared multifunctional self-healing material, exhibiting stable AIE fluorescence, is anticipated to possess significant value in the domains of smart anti-counterfeiting materials, flexible display screens and intelligent optoelectronics.

Innovative Biomaterials for Bone Tumor Treatment and Regeneration: Tackling Postoperative Challenges and Charting the Path Forward.

Surgical resection of bone tumors is the primary approach employed in the treatment of bone cancer. Simultaneously, perioperative interventions, particularly postoperative adjuvant anticancer strategies, play a crucial role in achieving satisfactory therapeutic outcomes. However, the occurrence of postoperative bone tumor recurrence, metastasis, extensive bone defects, and infection are significant risks that can result in unfavorable prognoses or even treatment failure. In recent years, there has been significant progress in the development of biomaterials, leading to the emergence of new treatment options for bone tumor therapy and bone regeneration. This progress report aims to comprehensively analyze the strategic development of unique therapeutic biomaterials with inherent healing properties and bioactive capabilities for bone tissue regeneration. These composite biomaterials, classified into metallic, inorganic non-metallic, and organic types, are thoroughly investigated for their responses to external stimuli such as light or magnetic fields, internal interventions including chemotherapy or catalytic therapy, and combination therapy, as well as their role in bone regeneration. Additionally, an overview of self-healing materials for osteogenesis is provided and their potential applications in combating osteosarcoma and promoting bone formation are explored. Furthermore, the safety concerns of integrated materials and current limitations are addressed, while also discussing the challenges and future prospects.