MnO2 Nanowires with Sub-10 nm Thick Conjugated Microporous Polymers as Synergistic Triboelectric Materials.

MnO2 nanowires coated with conjugated microporous polymers (CMP) are applied as triboelectric energy harvesting materials. The tribopositive performance of the CMP shells is enhanced with the assistance of MnO2 nanowires (MnO2 NW), likely due to cationic charge transfer from the tribopositive CMP layers to the surface Mn2+ and Mn3+ species of MnO2 NW. This is supported by model studies. The MnO2@CMP-2 with sub-10 nm thick CMP layers shows promising triboelectric output voltages up to 576 V and a maximum power density of 1.31 mW cm-2. Spring-assisted triboelectric nanogenerators fabricated with MnO2@CMP-2/PVP-3 films are used as power supplies to operate electronic devices.

Ultrasonic-assisted aqueous two-phase extraction and purification of polyphenols from hawk tea (Litsea coreana var. lanuginose): Investigating its impact on starch digestion.

Hawk tea, a conventional herbal beverage, is renowned for its beneficial properties in enhancing digestion and mitigating hyperglycemic tendencies. However, the extraction methodology for hawk tea polyphenols (HTP) has been understudied thus far, impeding its progress and broader application. To develop an efficient approach for HTP extraction, the present study introduced and optimized the application of ultrasonic-assisted aqueous two-phase extraction. Under optimal extraction conditions, the extraction yield of polyphenols from raw HTP was 7.86 %. During purification, LX-B14 was selected due to the highest adsorption and desorption abilities. Then in an in vitro simulated digestion system, HTP significantly reduced the expected glycemic index, raised the content of resistant starch, and decreased the activities of α-amylase and α-glucosidase, indicating its potential for alleviating starch digestion. Accordingly, the results provide an alternative approach for efficiently obtaining phenolic compounds from hawk tea, facilitating the advanced utilization of HTP within the food industry.

A Versatile Microporous Design toward Toughened yet Softened Self-Healing Materials.

Realizing the full potential of self-healing materials in stretchable electronics necessitates not only low modulus to enable high adaptivity, but also high toughness to resist crack propagation. However, existing toughening strategies for soft self-healing materials have only modestly improves mechanical dissipation near the crack tip (ГD), and invariably compromise the material's inherent softness and autonomous healing capabilities. Here, a synthetic microporous architecture is demonstrated that unprecedently toughens and softens self-healing materials without impacting their intrinsic self-healing kinetics. This microporous structure spreads energy dissipation across the entire material through a bran-new dissipative mode of adaptable crack movement (ГA), which substantially increases the fracture toughness by 31.6 times, from 3.19 to 100.86 kJ m-2, and the fractocohesive length by 20.7 times, from 0.59 mm to 12.24 mm. This combination of unprecedented fracture toughness (100.86 kJ m-2) and centimeter-scale fractocohesive length (1.23 cm) surpasses all previous records for synthetic soft self-healing materials and even exceeds those of light alloys. Coupled with significantly enhanced softness (0.43 MPa) and nearly perfect autonomous self-healing efficiency (≈100%), this robust material is ideal for constructing durable kirigami electronics for wearable devices.

Advancing Two-Photon Photodynamic Therapy Over NIR-II Excitable Conjugated Microporous Polymer with NIR-I Emission.

The availability of second near-infrared (NIR-II) excitable two-photon photosensitizers with NIR-I emission for efficient photodynamic therapy (PDT) is limited by challenges in molecular design. In this study, a NIR-II light-excitable two-photon conjugated microporous polymer (Tph-Dbd) with emission in the NIR-I region is developed. The large conjugated system and delocalized electronic structures endow Tph-Dbd with a large two-photon absorption cross-section under NIR-II light excitation. Moreover, the efficient electron acceptor and donor units within the π-conjugated backbones result in NIR-I emission for high signal-to-background ratio imaging, as well as separated highest occupied molecular orbital and lowest unoccupied molecular orbital distributions for excellent singlet oxygen generation ability. The excellent NIR-II excitable two-photon absorption activity, NIR-I emission, good biocompatibility, and high photostability allow Tph-Dbd to be used for efficient in vitro fluorescence imaging guided PDT. Moreover, the impressive photothermal effect of Tph-Dbd can overcome the limitations of PDT in the treatment of hypoxic tumors. This study highlights a strategy for designing NIR-II excitable two-photon photosensitizers for advanced PDT.

Modification of hollow microporous organic network with polyethyleneimine for efficient enrichment of phenolic acids from fruit juice samples.

Owning to the hydrophobic characteristics of microporous organic networks (MONs), their utilizations still largely limited in non- and weak-polar analytes. To expend their applications, here we reported the synthesis of a novel hollowed H-MON-PEI1800-2 composite via sacrifice template method and subsequent modification with polyethyleneimine (PEI) for efficient solid phase extraction of polar and ionic phenolic acid (PAs) from fruit juice samples. H-MON-PEI1800-2 exhibits large surface area, rapid extraction kinetics, remarkable chemical and thermal stabilities, and provides synergistic electrostatic, π-π, hydrogen bonding, and hydrophobic interaction sites for PAs. The developed method owns low limit of detection, wide linear range, large enrichment factors, and good reusability. The recoveries of H-MON-PEI1800-2 for PAs are 1-3 orders of magnitude higher than those of commercial adsorbents like activated carbon, C18 and Oasis HLB. This work highlights the prospects of functional H-MONs for enriching polar and ionic targets from complex sample matrices.

Hollow microporous organic network fiber membrane for efficient extraction of okadaic acid from marine organisms.

Membrane-based micro-solid phase extraction (M-µSPE) has garnered great attention in sample pretreatment, suffering an inherent contradiction between permeability and adsorption capacity. In this study, a pure microporous organic network (TEB-DIB-MON) fiber membrane was prepared by combining electrostatic spinning technology, Sonogashira-Hagihara reaction and template sacrifice method. The prepared TEB-DIB-MON membrane exhibited a large specific surface area with a hollow and porous structure, thereby providing excellent solvent permeability and high adsorption capacity for okadaic acid (OA, an algal toxin). Under the optimized conditions, a sensitive analytical method was established by coupling M-µSPE with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The established method has a low detection limit (0.5 pg mL-1), a wide linear range (1.5-1000 pg mL-1, R ≥ 0.9991), and good reproducibility (RSD ≤ 9.4 %, n = 6), which was then successfully applied for OA detection in marine organisms. Trace amounts of OA (59.3-89.0 pg mL-1) was detected in the oyster and prawn samples. This work demonstrated that the excellent application potential of MON membranes in sample pretreatment, while also presents a novel synthesis strategy for MONs membranes.

Enhanced detection of catecholamines in human urine using Cis-diol-microporous organic networks with PT-SPE and HPLC-MS/MS.

A novel cis-diol-microporous organic networks (MONs-2OH) material was synthesized via room temperature and Sonogashira coupling reactions, which exhibits exceptional adsorption properties for catecholamines (CAs). MONs-2OH demonstrates robust hydrogen bonding and π-π stacking interactions, crucial for effective adsorption. The MONs-2OH was incorporated into pipette tip solid-phase extraction and developed a new method for detecting CAs in human urine using HPLC-MS/MS. Characterization of the adsorbent revealed its high stability, large specific surface area, abundant phenolic hydroxyl groups, rapid extraction speed, and superior adsorption efficiency. The method achieved a wide linear range (0.5-500 ng/mL), low detection limits (0.06-0.26 ng/mL), high accuracy (90.4 %-99.4 %), and excellent precision (RSD ≤ 10 %). Comparative studies showed MONs-2OH outperforms commercial adsorbents in terms of recovery and adsorption capacity. The results underscore the potential of MONs-2OH for rapid and sensitive CAs determination, offering significant advantages for the auxiliary diagnosis of depression and enhancing the application of PT-SPE in sample pretreatment.

Rational Design of Highly Porous Donor-Acceptor Based Conjugated Microporous Polymer for Photocatalytic Benzylamine Coupling Reaction.

Conjugated microporous polymers (CMPs) are an important class of organic materials with several useful features like, inherent nanoscale porosity, large specific surface area and semiconducting properties, which are very demanding for various sustainable applications. Carbazole building blocks are extensively used in designing photocatalysts due to easy electron donation and hole transportation. In the current study, a new CMP material CBZ-CMP containing carbazole unit used for photocatalytic C═N coupling reaction under blue light irradiation is designed. The CBZ-CMP framework is made through the polycondensation of 4,4'-di(9H-carbazol-9-yl)-1,1'-biphenyl using FeCl3 as a catalyst. The CBZ-CMP shows very high BET surface area of 1536 m2 g-1 together with unimodal porosity (ca. 1.7 nm supermicropore), nanowire-like particle morphology (16-18 nm diameter), and low band gap property. The bi-phenyl moiety functions as the electron accepting center and the carbazole unit acts as the donor center, which accounts for the low band gap energy of CBZ-CMP. This nanoporous semiconducting CBZ-CMP material for photocatalytic benzylamine coupling reaction is explored, where it shows good conversion together with high selectivity under mild reaction conditions. This study offers simple method of preparation of a D-A-D-based porous photocatalyst for sustainable synthesis of value-added organics.

Artificial Lithium Channels Built from Polymers with Intrinsic Microporosity.

In sharp contrast to numerous artificial potassium channels developed over the past decade, the study of artificial lithium-transporting channels has remained limited. We demonstrate here the use of an interesting class of polymers with intrinsic microporosity (PIM) for constructing artificial lithium channels. These PIM-derived lithium channels show exceptionally efficient (γLi+ > 40 pS) and highly selective transport of Li+ ions, with selectivity factors of > 10 against both Na+ and K+. By simply adjusting the initial reaction temperature, we can tune the transport property in a way that PIMs synthesized at initial reaction temperatures of 60 °C and 80°C exhibit improved transport efficiency and selectivity, respectively, in the dioleoyl phosphatidylcholine  membrane.

Coordinatively Unsaturated Co Single-Atom Catalysts Enhance the Performance of Lithium-Sulfur Batteries by Triggering Strong d-p Orbital Hybridization.

The catalytic activities displayed by single-atom catalysts (SACs) depend on the coordination structure. SACs supported on carbon materials often adopt saturated coordination structures with uneven distributions because they require high-temperature conditions during synthesis. Herein, bisnitrogen-chelated Co SACs that are coordinatively unsaturated are prepared by integrating a Co complex into a conjugated microporous polymer (CMP-CoN2). Compared with saturated analogues, i.e., tetranitrogen-chelated Co SACs (denoted as CMP-CoN4), CMP-CoN2 exhibits higher electrocatalytic activity in polysulfide conversions due to an enhanced hybridization between the 3d orbitals of the Co atoms and the 3p orbitals of the S atoms in the polysulfide. As a result, sulfur cathodes prepared with CoN2 deliver outstanding performance metrics, including a high specific capacity (1393 mA h g-1 at 0.1 C), a superior rate capacity (673.2 mA h g-1 at 6 C), and a low capacity decay rate (of only 0.045% per cycle at 2 C over 1000 cycles). They also outperform sulfur cathodes that contain CMP-CoN4 or CMPs that are devoid of Co SACs. This work reveals how the catalytic activity displayed by SACs is affected by their coordination structures, and the rules that underpin the structure-activity relationship may be extended to designing electrocatalysts for use in other applications.

Construction of Donor-Acceptor-Type Conjugated Microporous Polymers by Oxidative Coupling of Boranil-Carbazole Mixed Monomers for Enhanced Photocatalytic Oxidation.

Conjugated microporous polymers (CMPs), featuring photoactive structures, a high surface area, robust thermal stability, and facile modulation, provide a versatile platform for fabricating diverse heterogeneous photocatalysts. The incorporation of donor-acceptor (D-A) structures into CMPs to increase their charge separation potential and enhance the photocatalytic efficacy is a viable strategy. In this work, we designed and synthesized a unique set of D-A monomers, incorporating boranil dyes as electron-deficient moieties and carbazoles as electron-rich subunits. Subsequently, D-A CMPs were prepared via an economical and environmentally friendly oxidation coupling reaction, and their potential in photocatalytic oxidation reactions was investigated. Modulation of the polymer's photoelectronic properties and photocatalytic performance can be achieved by adjusting the boranil content in the monomer. The polymer pCZFB-3, with the highest content of boranil units, exhibited an optimal photocatalytic activity. This finding confirms that strengthening the D-A effect can significantly enhance a catalyst's photoelectronic properties and catalytic efficacy. This study presents insights into designing innovative heterogeneous photocatalysts based on boron-containing dyes.

Biosynthesis of pterostilbene in Escherichia coli from resveratrol on macroporous adsorption resin using a two-step substrate addition strategy.

Pterostilbene (PST), a 3',5'-O-methylated derivative of resveratrol (RSV), is a potent natural antioxidant produced by some plants in trace amounts as defense compound. It exhibits various health-promoting activities, such as anticancer, antiviral, and antimicrobial effects. Large-scale biosynthesis of PST is crucial due to the challenges associated with extracting it from plants. This study aims to develop an efficient method for PST production using an engineered Escherichia coli strain by feeding RSV as a precursor. We introduced a two-step substrate addition strategy combined with immobilized RSV (IMRSV) on macroporous adsorption resin (MAR) to enhance PST production. Five MARs were selected for RSV immobilization, and the substrate addition strategy and fermentation parameters for PST synthesis were optimized. A maximum PST concentration of 403 ± 9 mg/L was achieved, representing a 239% increase over the control, which in a one-step addition of free RSV. The PST titer reached 395 ± 24 mg/L in a 3-L bioreactor. In conclusion, the combination of a two-step substrate addition system and IMRSV is a promising approach for the economical and industrial-scale production of PST.

Microporous polysaccharide hemospheres for reducing pocket hematomas after cardiac device implantation in patients on antithrombotic therapy.

Background: Various surgical procedures have employed microporous polysaccharide hemosphere (MPH) hemostatic agents. However, data regarding their effectiveness in preventing pocket hematomas (PHs) during the implantation of cardiac implantable electronic devices (CIED) among the Asian population are limited. Therefore, this study aimed to investigate the potential benefits of using MPH hemostatic agents during CIED implantations as a preventive measure against post-procedural PHs. Methods: We conducted a retrospective, single-center, observational study involving 255 consecutive Japanese patients who underwent CIED implantation between November 2017 and April 2021. We compared PH occurrences within 28 days after CIED implantation between patients who received MPH hemostatic agents (n = 145) and those who did not (n = 110). Results: PH development was observed in nine (6.2%) patients who received MPH hemostatic agents and in 13 (11.8%) patients without MPH hemostatic (p = .111). Kaplan-Meier analysis of PH development revealed no significant difference between the two groups (log-rank p = .102). However, utilizing MPH hemostatic agents among patients taking antithrombotic drugs, including antiplatelet medications, direct oral anticoagulants, and warfarin, significantly reduced PH incidence (log-rank p = .03). The multivariate Cox proportional hazards model demonstrated that MPH hemostatic agent utilization independently correlated with a decreased PH risk (hazard ratio 0.22, 95% confidence interval 0.08-0.63, p = .004). Conclusions: The findings of this study suggest that the incorporation of MPH hemostatic agents into standard practice may benefit to mitigate PH risk during CIED implantations in patients on antithrombotic therapy. This simple and practical measure may be valuable, especially in high-risk patients, such as those taking antithrombotic medications.

Meso/Microporous Single-Atom Catalysts with Curved Fe-N4 sites Boost the Oxygen Reduction Reaction Activity.

Zeolitic-imidazolate frameworks (ZIFs) are among the most efficient precursors for the synthesis of atomically dispersed Fe-N/C materials, which are promising catalysts for enhancing the performance of Zn-air batteries (ZABs) and proton exchange fuel cells (PEMFCs). However, existing ZIF-derived Fe-N/C electrocatalysts mostly consist of microporous materials, leading to insufficient mass transport and inadequate battery/cell performance. In this study, we synthesize an atomically dispersed meso/microporous Fe-N/C material with curved Fe-N4 active sites, denoted as FeSA-N/TC, through the pyrolysis of hemin-modified ZIF films on ZnO nanorods, obtained from the self-assembly reaction between Zn2+ from ZnO hydrolysis and 2-methylimidazole. Density functional theory calculations demonstrate that the curved Fe-N4 active sites can weaken the intermediate adsorptions, resulting in lower free energy barriers and enhanced performance during oxygen reduction reaction (ORR). Specifically, FeSA-N/TC exhibits exceptional ORR performance with half-wave potentials of 0.925 V in alkaline media and 0.825 V in acidic media. When used as the cathodic catalyst in PEMFCs and ZABs, FeSA-N/TC achieves high peak power densities (H2-O2 PEMFC: 1100 mW cm-2; H2-Air PEMFC: 715 mW cm-2; liquid-state ZAB: 228 mW cm-2; solid-state ZAB: 112 mW cm-2), demonstrating its feasibility and efficiency in practical applications.

An enzymatic reaction-based SERS saliva analysis microporous array chip for chiral differentiation and high-throughput detection of D-amino acids.

A Raman-active boronate modified surface-enhanced Raman scattering (SERS) microporous array chip based on the enzymatic reaction was constructed for reliable, sensitive, and quantitative monitoring of D-Proline (D-Pro) and D-Alanine (D-Ala) in saliva. Initially, 3-mercaptophenylboronic acid (3-MPBA) was bonded to Au-coated Si nanocrown arrays (Au/SiNCA) via Au-S bonding. Following this, H2O2 obtained from D-amino acid oxidase (DAAO)-specific catalyzed D-amino acids (D-AAs) further reduced 3-MPBA to 3-hydroxythiophenol (3-HTP) with a new Raman peak at 882 cm-1. Meanwhile, the original characteristic peak at 998 cm-1 remained unchanged. Therefore, the I882/I998 ratio increased with increasing content of D-AAs in the sample to be tested, allowing D-AAs to be quantitatively detected. The Au/SiNCA with large-area periodic crown structure prepared provided numerous, uniform "hot spots," and the microporous array chip with 16 detection units was employed as the platform for SERS analysis, realizing high-throughput, high sensitivity, high specificity and high-reliability quantitative detection of D-AAs (D-Pro and D-Ala). The limits of detection (LOD) were down to 10.1 µM and 13.7 µM throughout the linear range of 20-500 µM. The good results of the saliva detection suggested that this SERS sensor could rapidly differentiate between early-stage gastric cancer patients and healthy individuals.

Study on photocatalytic degradation and antibacterial properties of conjugated microporous polymers/TiO2 composite membranes.

Conjugated microporous polymers (CMPs) are widely used in the field of photocatalysis due to their unique conjugated structures and various synthesis methods. Herein, we report the design and synthesis of conjugated microporous polymers hollow spheres (CMPs-HS) superhydrophilic modified by acetylcysteine (CMPs-HS-S) and compounded with the inorganic semiconductor material titanium dioxide (CMPs-HS-S/TiO2) for efficient photocatalytic degradation. To facilitate recycling, the composite membrane material was prepared by combining the materials mentioned above with PVDF membrane. The composite membrane materials had good hydrophilic and photocatalytic properties. Under visible light, the degradation rate of tetracycline (TC) (10 mg/L 180 min) reached 90 %, and the bactericidal rates for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were 89 % and 99.99 %, respectively. The efficient photocatalytic performance of the composite membranes could be attributed to the hollow sphere structure of CMPs and the role of TiO2 as a photogenic electron transfer platform. Additionally, the hydrophilicity of the membrane also helped to accelerate the occurrence of photocatalytic reactions. After electron paramagnetic resonance (EPR) detection, h+, 1O2 and O2- were proved to be important reactive substances, which played a major role in degradation. These studies reflect the versatility of CMPs-based photocatalysts and provide a new idea for the future development of CMPs-based photocatalysts.

2D Microporous Polymers/Reduced Graphene Oxide with Built-In Lithiophilic Sites for Uniform Lithium Deposition in Lithium Metal Anode.

Lithium (Li) metal is an attractive anode material for use in high-energy lithium-sulfur and lithium-air batteries. However, its practical application is severely impeded by excessive dendrite growth, huge volume changes, and severe side reactions. Herein, a novel Li metal anode composed of lithiophilic two dimensional (2D) conjugated microporous polymer (Li-CMP) and reduced graphene oxide (rGO) sandwiches (Li-CMP@rGO) for Li metal batteries (LiMBs) is reported. In the Li-CMP@rGO anode, the conductive rGO facilitates the charge transfer while the functionalized-CMP provides Li nucleation sites within the micropores, thereby preventing dendrite growth. As a result, the Li-CMP@rGO anode can be cycled smoothly at 6 mA cm-2 of current density with a platting capacity of 2 mAh cm-2 for 1000 h. A Coulombic efficiency of 98.4% is achieved over 350 cycles with a low overpotential of 28 mV. In a full cell with LiFePO4 cathode, the Li-CMP@rGO anode also exhibited good cycling stability compared to CMP@rGO and CMP/Super-P. As expected, the simulation results reveal that Li-CMP@rGO has a strong affinity for Li ions compared to CMP@rGO. The strategies adopted in this work can open new avenues for designing hybrid porous host materials for developing safe and stable Li metal anodes.

3D Graphene-like Carbon Structures from Poly(Acrylic Acid): A Novel Synthetic Route.

Emerging contaminants, such as the hormone 17α-ethynylestradiol (EE), in aquatic environments pose a serious risk to both human and environmental health, making efficient removal essential. This study evaluated the effectiveness of three-dimensional porous carbon structures derived from poly(acrylic acid) (PAAc, Carbopol 990) as adsorbents for removing EE from aqueous solutions. Activated carbon materials were prepared using varying ratios of KOH as an activating agent (PAAc:KOH; 1:0 AAC, 1:1 AC1, 1:2 AC2, and 1:3 AC3). Adsorption tests were conducted by adding 10 mg of the adsorbent to 40 mL of an EE solution (100 ppm, 20% acetonitrile in water). Analyses including TGA, XRD, and Raman spectroscopy were performed to evaluate the materials' structural properties and adsorption capacities. Among the materials, AC3 exhibited the highest adsorption capacity for EE (238 mg g-1), followed by AC2 (153 mg g-1) and AC1 (82 mg g-1). The superior efficiency of AC3 can be attributed to its larger surface area and pore volume, enabling greater interaction with EE molecules. These materials demonstrated higher adsorption capacities compared to commercial activated carbons and single-walled carbon nanotubes. This work opens new possibilities for developing efficient adsorbents, contributing to more effective and sustainable solutions for water purification and environmental protection.

RF pulsed plasma modified composite scaffold for enhanced anti-microbial activity and accelerated wound healing.

Infected wounds present significant challenges pertaining to healing and often demand administration of strong antibiotics to patients. Also, drug resistant microbes may alter the physiology of wounds to create biofilms, frequently leading to high morbidity and mortality. In this investigation, a biodegradable, microporous composite agarose-chitosan scaffold was fabricated. Furthermore, its surface was modified with diphenyldiselenide deposition, using low pressure pulsed plasma technology. The optimized plasma parameters, viz. 5ON/15OFF (ms) of plasma pulse rate and 80 min of treatment time resulted in scaffolds having enhanced anti-bacterial activity against gram positive microbes like Staphylococcus (S.) aureus and S. epidermidis. The scaffolds were non-toxic to skin cells, as confirmed by the MTT assay. Cell proliferation through plasma treated and untreated scaffolds was assessed by culturing primary human dermal fibroblasts (HdaF) and human keratinocytes (HaCaT) and visualizing via confocal microscopy. Moreover, in-vivo rat model confirmed accelerated wound healing with plasma treated scaffold (100 % on day 14), as compared to the untreated scaffold (100 % on day 16) when compared with over-the-counter (OTC) ointment Betadine (100 % on day 12).

Preparation and properties of polydimethylsiloxane-regulated oriented microporous poly (L-lactic acid) biomimetic bone repair materials.

Despite the exceptional biocompatibility and degradability of Poly (L-lactic acid) (PLLA), its brittleness, low melting strength, and poor bone induction makes it challenging to utilize for bone repair. This study used a simple, efficient solid hot drawing (SHD) method to produce high-strength PLLA, using supercritical CO2 (SC-CO2) foaming technology to give PLLA a bionic microporous structure to enhance its toughness, while precisely controlling micropore homogeneity and improving the melt strength by using Polydimethylsiloxane (PDMS). This PDMS-regulated oriented microporous structure resembled that of natural bone, displaying a maximum tensile strength of 165.9 MPa and a maximum elongation at break of 164.2 %. Furthermore, this bionic structure promoted the polarization of mouse bone marrow macrophages (iBMDM), exhibiting a simultaneous pro- and anti-inflammatory effect. This structure also contributed to the adhesion and growth of mouse embryonic fibroblasts (NIH-3 T3), promoting osteogenic differentiation, which paved the way for developing degradable PLLA bone-repair load-bearing materials.