Search

Graphical abstract:

AbstractThe deposition of textile waste into landfill has reached an unsustainable level and raises serious environmental issues across the world. Transforming textile waste into fiber reinforcement in cementitious composites offers a sustainable resolution toward a circular textile economy. This article presents a comprehensive review of environmental concerns, recycling routes for textile waste, together with an in-depth review of the engineering properties of concrete incorporating recycled textiles. In general, the incorporation of these recycled fibers from textile waste enhances strain capacity, crack control, durability, and energy absorption of concrete viadual effects: bridging action (direct mechanism) and refinement of pore distribution (indirect effect). An improvement in compressive strength can be achieved by the utilization of a small dosage of recycled fibers or recycled fiber fabrics in concrete (strength < 40 MPa). Finally, the cost and environmental benefits for eco-efficient building application are also evaluated to draw the attention of researchers toward these potentially recyclable waste materials.

Next generation wound care technology capable of diagnosing wound parameters, promoting healthy cell growth, and reducing pathogenic infections noninvasively would provide patients with an improved standard of care and accelerated wound repair. Temperature is one of the indicating biomarkers specific to chronic wounds. This work reports a hybrid, multifunctional optical material platform—nanodiamond (ND)–silk membranes as biopolymer dressings capable of temperature sensing and promoting wound healing. The hybrid structure was fabricated through electrospinning, and 3D submicron fibrous membranes with high porosity were formed. Silk fibers are capable of compensating for the lack of an extracellular matrix at the wound site, supporting the wound-healing process. Negatively charged nitrogen vacancy (NV–) color centers in NDs exhibit optically detected magnetic resonance (ODMR) and act as nanoscale thermometers. This can be exploited to sense temperature variations associated with the presence of infection or inflammation in a wound, without physically removing the dressing. Our results show that the presence of NDs in the hybrid ND–silk membranes improves the thermal stability of silk fibers. NV–color centers in NDs embedded in silk fibers exhibit well-retained fluorescence and ODMR. Using the NV–centers as fluorescent nanoscale thermometers, we achieved temperature sensing in 25–50 °C, including the biologically relevant temperature window, for cell-grown ND–silk membranes. An enhancement (∼1.5× on average) in the temperature sensitivity of the NV–centers was observed for the hybrid materials. The hybrid membranes were further tested in vivoin a murine wound-healing model and demonstrated biocompatibility and equivalent wound closure rates as the control wounds. Additionally, the hybrid ND–silk membranes exhibited selective antifouling and biocidal propensity toward Gram-negative Pseudomonas aeruginosaand Escherichia coli, while no effect was observed on Gram-positive Staphylococcus aureus.

Nanodiamonds (ND) have been gaining impetus in fields such as medicine and electronics. ND has been widely used to modify polymer surfaces and composites for improved functionality. However, there have been limited research on ND application in regard to textile substrates. In this study, we presented a sustainable coating method, adapted to functionalized ND particles that would be coated onto wool fabric surfaces to enhance hydrophilicity. The application of an ND coating was found to increase wool hydrophilicity because of the presence of additional polar groups, shown by Fourier transform infrared spectrometry, which increased surface energy and fiber roughness. Scanning electron microscopy images revealed that the polar ND-coated wool scales demonstrated improved fiber hydrophilicity. Water absorbency, wicking, and contact angle results for coated fabrics confirmed significant improvement in hydrophilicity, which was directly related to the concentration of ND particles. The optimal concentration of ND was therefore selected to coat the wool fabric. Furthermore, tensile strength and abrasion resistance of the coated fabrics were increased due to the exceptional mechanical properties of ND.

Compliance mismatch of commercially available artificial grafts, where the artificial graft and the native vessel are subject to different radial expansions, is a major issue that results in graft occlusion after implantation. A human artery possesses a nonlinear mechanical response to pulsatile pressure due to its nonlinear viscoelastic nature, which is difficult to replicate in artificial graft fabrication. Here, we fabricated nanocomposites with nonlinear mechanical responses for potential application as the load-bearing layer of vascular grafts, based on a poly(dimethylsiloxane) (PDMS)-casted nanofibrous film. The nanofibers consisted of a core–sheath structure with a PDMS elastomer reinforced with poly(methyl methacrylate) (PMMA) nanofibers as the sheath and thermoplastic polyurethane (TPU) elastomer as the core. The surface morphology and chemical composition together with the crystalline structure of the nanocomposites were characterized, and dynamic mechanical analysis was performed to select the graft with the most suitable properties as the load-bearing layer of a small-diameter vascular graft. The presence of the stiff polymer PMMA and elastic polymer TPU in the PMMA/PDMS/TPU combination resulted in a delayed dissipation of energy after exposure to a force corresponding to 180 mm Hg. Casting the PDMS/PMMA/TPU nanofibrous mat into a nanocomposite film improved the ultimate tensile strength of PDMS without compromising its elasticity. The compliance values of the nanocomposites were also found to be a close match to those of the greater saphenous vein, demonstrating a great potential of the nanocomposites as the load-bearing layer in a biostable vascular graft.

Summary: The melting temperature difference between poly(propylene) (PP) fibre and random poly(propylene-co‐ethylene) (PPE) was exploited to establish processing conditions for all‐PP composite. Under these conditions, the matrix must be liquid to ensure good wetting and impregnation of fibres, though temperatures must be low enough to avoid melting of fibres. The high chemical compatibility of the two components allowed creation of strong physico‐chemical interactions, favouring strong interfacial adhesion. Static and dynamic mechanical properties and morphology of all‐PP composites were investigated according to method of preparation and compared with the behaviour of hot compacted composites, prepared under different moulding conditions. The composites were compacted with varying pressure and time, and mechanical and thermal properties of the resulting sheets were measured. With increased moulding time, more fibres melted or their original properties deteriorated. Fast cooling or quenching caused imperfect morphology. Moulding pressure played an important role. Morphology of the optimum hot compacted composite was investigated using scanning electron microscopy before and after tensile testing. Tensile fracture surfaces showed a melted phase epitaxially crystallised onto the remaining orientated phase. Compacted composites showed fibre shapes under a thin layer of PPE with all of the gaps between fibres filled by melted PPE matrix.SEM of compacted all-PP composite without quenching.

Summary: The difference between the melting temperatures of poly(propylene) (PP) fibre and random poly(propylene-co‐ethylene) (PPE) was exploited in order to establish processing conditions for an all PP composite. Under these conditions the matrix must be a liquid in order to ensure good wetting and impregnation at the fibres, though the temperature must not be too high to avoid melting the fibres. The high chemical compatibility of the two components allowed creation of strong physico‐chemical interactions, which favour strong interfacial adhesion. The static and dynamic mechanical properties and morphology of poly(propylene) woven fabric reinforced random PPE composites have been investigated with reference to the woven geometry that influenced the properties of the woven composites. Among the various cloth architectures that were used in the PP‐PPE composites, the satin weave imparted overall excellent mechanical properties due to the weave parameters, such as high float length and fibre count, low interlace point and crimp angle, etc. Morphology of the composite has been investigated by macro photography and scanning electron microscopy. Images from scanning electron microscopy provided confirmation of the above results by displaying the consolidation and good fibre‐matrix wetting of the composites.Loss modulus of poly(propylene) woven-matrix composites with different types of woven geometry.

Preparation and properties of poly(propylene)-poly(propylene) composites have been investigated. Poly(propylene) fibres of varying diameter have been incorporated in a random ethylene co-poly(propylene). The composites prepared from the same semi-crystalline polymer in the matrix and reinforcement have lead to inherently strong interfacial bonding between the two phases of the same polymer. The composites demonstrated enhanced stiffness, which increased with fibre diameter. The structure, thermal, static and mechanical properties of poly(propylene) long fibre reinforced random co-poly(propylene) composites have been studied with reference to the fibre diameter. The matrix and fibre components retained their separate melting temperatures. After melting, the two phases remained separate and showed their individual crystallization temperatures on cooling, and melting temperatures on a second heating. The melting temperature of the poly(propylene) fibres increased after formation of the composites. The compression molding of the composites at a temperature below the melting temperature of the fibres caused annealing of the fibre crystals. By incorporation of long poly(propylene) fibre into random co-poly(propylene), the glass transition, storage and static modulus have been found to be increasing and composite with the largest fibre diameter shows better properties. Transcrystallization of the matrix poly(propylene) was observed. Optical microscopy of composites with fibre diameter 68 μm.

Additive manufacturing or 3D-printing is used to create bespoke items in many fields, such as defence, aerospace and medicine. Despite the progress made in 3D-printed orthopaedic implants, significant challenges remain in terms of creating a material capable of osseointegration while inhibiting bacterial colonisation of the implant. Diamond is rapidly emerging as a material with an extensive range of biomedical applications, especially due to its excellent biocompatibility. However, diamond is a difficult material to fabricate, owing to its extreme level of hardness and its brittleness. New methods of fabrication, including additive manufacturing, have overcome some of these challenges and given rise to an increase in the use of diamond-based implants in both soft and hard tissue applications. This review outlines the recent progress in fabricating diamond for orthopaedic application, specifically focusing on the different fabrication approaches and their applicability in vitroand in vivo. The prospects and challenges of using a diamond in medical implant technologies are also discussed.

Magnesium hydroxide (Mg(OH)2) is hailed as a cheap and biocompatible material with antimicrobial potential; however, research aimed at instilling additional properties and functionality to this material is scarce. In this work, we synthesized novel, fluorescent magnesium hydroxide nanosheets (Mg(OH)2-NS) with a morphology that closely resembles that of graphene oxide. These multifunctional nanosheets were employed as a potent antimicrobial agent against several medically relevant bacterial and fungal species, particularly on solid surfaces. Their strong fluorescence signature correlates to their hydroxide makeup and can therefore be used to assess their degradation and functional antimicrobial capacity. Furthermore, their pH-responsive change in fluorescence can potentially act as a pH probe for wound acidification, which is characteristic of healthy wound healing. These fluorescent antimicrobial nanosheets were stably integrated into biocompatible electrospun fibers and agarose gels to add functionality to the material. This reinforces the suitability of the material to be used as antimicrobial bandages and gels. The biocompatibility of the Mg(OH)2-NS for topical medical applications was supported by its noncytotoxic action on human keratinocyte (HaCaT) cells.

Owing to several key attributes, diamond is an attractive candidate material for neural interfacing electrodes. The emergence of additive-manufacturing (AM) of diamond-based materials has addressed multiple challenges associated with the fabrication of diamond electrodes using the conventional chemical vapor deposition (CVD) approach. Unlike the CVD approach, AM methods have enabled the deposition of three-dimensional diamond-based material at room temperature. This work demonstrates the feasibility of using laser metal deposition to fabricate diamond–titanium hybrid electrodes for neuronal interfacing. In addition to exhibiting a high electrochemical capacitance of 1.1 mF cm–2and a low electrochemical impedance of 1 kΩ cm2at 1 kHz in physiological saline, these electrodes exhibit a high degree of biocompatibility assessed in vitrousing cortical neurons. Furthermore, surface characterization methods show the presence of an oxygen-rich mixed-phase diamond–titanium surface along the grain boundaries. Overall, we demonstrated that our unique approach facilitates printing biocompatible titanium–diamond site-specific coating-free conductive hybrid surfaces using AM, which paves the way to printing customized electrodes and interfacing implantable medical devices.

No Abstract