Voids, the most studied type of manufacturing defects, form very often in processing of fiber-reinforced composites. Due to their considerable influence on physical and thermomechanical properties of composites, they have been extensively studied, with the focus on three research tracks: void formation, characteristics, and mechanical effects. Investigation of voids in composites started around half a century ago and is still an active research field in composites community. This is because of remaining unknowns and uncertainties about voids as well as difficulties in their suppression in modern manufacturing techniques like out-of-autoclave curing and parts with high complexity, further complicated by increased viscosity of modified resins. Finally, this is because of the increasing interest in realization of more accurate void rejection limits that would tolerate some voidage. The current study reviews the research on formation, characterization, and mechanical effects of voids, which has been conducted over the past five decades. Investigation and control of void formation, using experimental and modeling approaches, in liquid composite molding as well as in prepreg composite processing are surveyed. Techniques for void characterization with their advantages and disadvantages are described. Finally, the effect of voids on a broad range of mechanical properties, including inter-laminar shear, tensile, compressive, and flexural strength as well as fracture toughness and fatigue life, is appraised. Both experimental and simulation approaches and results, concerning voids' effects, are reviewed.
Abstract Three-dimensional lattices have applications across a range of fields including structural lightweighting, impact absorption and biomedicine. In this work, lattices based on triply periodic minimal surfaces were produced by polymer additive manufacturing and examined with a combination of experimental and computational methods. This investigation elucidates their deformation mechanisms and provides numerical parameters crucial in establishing relationships between their geometries and mechanical performance. Three types of lattice were examined, with one, known as the primitive lattice, being found to have a relative elastic modulus over twice as large as those of the other two. The deformation process of the primitive lattice was also considerably different from those of the other two, exhibiting strut stretching and buckling, while the gyroid and diamond lattices deformed in a bending dominated manner. Finite element predictions of the stress distributions in the lattices under compressive loading agreed with experimental observations. These results can be used to create better informed lattice designs for a range of mechanical and biomedical applications.
Abstract While the developments of additive manufacturing (AM) techniques have been remarkable thus far, they are still significantly limited by the range of printable, functional material systems that meet the requirements of a broad range of industries; including the health care, manufacturing, packaging, aerospace, and automotive industries. Furthermore, with the rising demand for sustainable developments, this review broadly gives the reader a good overview of existing AM techniques; with more focus on the extrusion-based technologies (fused deposition modeling and direct ink writing) due to their scalability, cost efficiency and wider range of material processability. It then goes on to identify the innovative materials and recent research activities that may support the sustainable development of extrusion-based techniques for functional and multifunctional (4D printing) part and product fabrication.
G. Wang, Ferdinand S. Melkonyan, A. Facchetti
et al.
For over two decades bulk-heterojunction polymer solar cell (BHJ-PSC) research was dominated by donor:acceptor BHJ blends based on polymer donors and fullerene molecular acceptors. This situation has changed recently, with non-fullerene PSCs developing very rapidly. The power conversion efficiencies of non-fullerene PSCs have now reached over 15 %, which is far above the most efficient fullerene-based PSCs. Among the various non-fullerene PSCs, all-polymer solar cells (APSCs) based on polymer donor-polymer acceptor BHJs have attracted growing attention, due to the following attractions: 1) large and tunable light absorption of the polymer donor/polymer acceptor pair; 2) robustness of the BHJ film morphology; 3) compatibility with large scale/large area manufacturing; 4) long-term stability of the cell to external environmental and mechanical stresses. This Minireview highlights the opportunities offered by APSCs, selected polymer families suitable for these devices with optimization to enhance the performance further, and discusses the challenges facing APSC development for commercial applications.
Abstract This article provides a database of the mechanical properties of additively manufactured polymeric materials fabricated using material extrusion (e.g., fused filament fabrication (FFF)). Mechanical properties available in the literatures are consolidated in table form for different polymeric materials for FFF. Mechanical properties such as tensile, compressive, flexural, interlayer, fatigue, and creep properties are discussed in detail. The effects of printing parameters such as raster angle, infill, and specimen orientation on properties are also provided, together with a discussion of the possible causes (e.g., texture, microstructure changes, and defects) of anisotropy in properties. In addition to that, research gaps are identified which warrant further investigation.
Petroleum-based plastic materials as pollutants raise concerns because of their impact on the global ecosystem and on animal and human health. There is an urgent need to remove plastic waste from the environment to overcome the environmental crisis of plastic pollution. This review describes the natural and unique ability of fungi to invade substrates by using enzymes that have the capacity to detoxify pollutants and are able to act on nonspecific substrates, the fungal ability to produce hydrophobins for surface coating to attach hyphae to hydrophobic substrates, and hyphal ability to penetrate three dimensional substrates. Fungal studies on macro- and microplastics biodegradation have shown that fungi are able to use these materials as the sole carbon and energy source. Further research is required on novel isolates from plastisphere ecosystems, on the use of molecular techniques to characterize plastic-degrading fungi and enhance enzymatic activity levels, and on the use of omics-based technologies to accelerate plastic waste biodegradation processes. The addition of pro-oxidants species (photosensitizers) and the reduction of biocides and antioxidant stabilizers used in the plastic manufacturing process should also be considered to promote biodegradation. Interdisciplinary research and innovative fungal strategies for plastic waste biodegradation, as well as ecofriendly manufacturing of petroleum-based plastics, may help to reduce the negative impacts of plastic waste pollution in the biosphere.
Sarah A. Stewart, Juan Domínguez-Robles, Ryan F. Donnelly
et al.
The oral route is a popular and convenient means of drug delivery. However, despite its advantages, it also has challenges. Many drugs are not suitable for oral delivery due to: first pass metabolism; less than ideal properties; and side-effects of treatment. Additionally, oral delivery relies heavily on patient compliance. Implantable drug delivery devices are an alternative system that can achieve effective delivery with lower drug concentrations, and as a result, minimise side-effects whilst increasing patient compliance. This article gives an overview of classification of these drug delivery devices; the mechanism of drug release; the materials used for manufacture; the various methods of manufacture; and examples of clinical applications of implantable drug delivery devices.
In the last decade, significant developments of flexible and stretchable force sensors have been witnessed in order to satisfy the demand of several applications in robotic, prosthetics, wearables and structural health monitoring bringing decisive advantages due to their manifold customizability, easy integration and outstanding performance in terms of sensor properties and low-cost realization. In this paper, we review current advances in this field with a special focus on polymer/carbon nanotubes (CNTs) based sensors. Based on the electrical properties of polymer/CNTs nanocomposite, we explain underlying principles for pressure and strain sensors. We highlight the influence of the manufacturing processes on the achieved sensing properties and the manifold possibilities to realize sensors using different shapes, dimensions and measurement procedures. After an intensive review of the realized sensor performances in terms of sensitivity, stretchability, stability and durability, we describe perspectives and provide novel trends for future developments in this intriguing field.
The ongoing miniaturization of devices and development of wireless and implantable technologies demand electromagnetic interference (EMI)‐shielding materials with customizability. Additive manufacturing of conductive polymer hydrogels with favorable conductivity and biocompatibility can offer new opportunities for EMI‐shielding applications. However, simultaneously achieving high conductivity, design freedom, and shape fidelity in 3D printing of conductive polymer hydrogels is still very challenging. Here, an aqueous Ti3C2‐MXene‐functionalized poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate ink is developed for extrusion printing to create 3D objects with arbitrary geometries, and a freeze–thawing protocol is proposed to transform the printed objects directly into highly conductive and robust hydrogels with high shape fidelity on both the macro‐ and microscale. The as‐obtained hydrogel exhibits a high conductivity of 1525.8 S m–1 at water content up to 96.6 wt% and also satisfactory mechanical properties with flexibility, stretchability, and fatigue resistance. Furthermore, the use of the printed hydrogel for customizable EMI‐shielding applications is demonstrated. The proposed easy‐to‐manufacture approach, along with the highlighted superior properties, expands the potential of conductive polymer hydrogels in future customizable applications and represents a real breakthrough from the current state of the art.
N. M. Nurazzi, F. A. Sabaruddin, M. M. Harussani
et al.
Developments in the synthesis and scalable manufacturing of carbon nanomaterials like carbon nanotubes (CNTs) have been widely used in the polymer material industry over the last few decades, resulting in a series of fascinating multifunctional composites used in fields ranging from portable electronic devices, entertainment and sports to the military, aerospace, and automotive sectors. CNTs offer good thermal and electrical properties, as well as a low density and a high Young’s modulus, making them suitable nanofillers for polymer composites. As mechanical reinforcements for structural applications CNTs are unique due to their nano-dimensions and size, as well as their incredible strength. Although a large number of studies have been conducted on these novel materials, there have only been a few reviews published on their mechanical performance in polymer composites. As a result, in this review we have covered some of the key application factors as well as the mechanical properties of CNTs-reinforced polymer composites. Finally, the potential uses of CNTs hybridised with polymer composites reinforced with natural fibres such as kenaf fibre, oil palm empty fruit bunch (OPEFB) fibre, bamboo fibre, and sugar palm fibre have been highlighted.
Melt electrowriting (MEW) is an emerging high‐resolution additive manufacturing technique based on the electrohydrodynamic processing of polymers. MEW is predominantly used to fabricate scaffolds for biomedical applications, where the microscale fiber positioning has substantial implications in its macroscopic mechanical properties. This review gives an update on the increasing number of polymers processed via MEW and different commercial sources of the gold standard poly(ε‐caprolactone) (PCL). A description of MEW‐processed polymers beyond PCL is introduced, including blends and coated fibers to provide specific advantages in biomedical applications. Furthermore, a perspective on printer designs and developments is highlighted, to keep expanding the variety of processable polymers for MEW.
Daniel Esse, Benedikt Scheuring, Frank Henning
et al.
Dynamic mechanical thermal analysis is a well-established method to determine the influence of temperature and frequencies on polymers. One challenge inherent to this method is the potential for significant changes in material properties, which can exceed several orders of magnitude and rapidly approach the accuracy or mechanical limits of measurement systems or actuators. In this work, it is shown that a change in the magnitude of the mechanical load within the linear elastic region does not affect the results. Consequently, the test parameters during the DMTA to be adapted to the stiffness of the specimens, allowing materials and volumes closer to the limits of the testing system to be measured. Furthermore, master curves were generated according to the temperature–time superposition for the frequency from the measured sections using a modified method. This was achieved by shifting the loss factor and applying the shift factor to the storage modulus. The tests presented in this work were carried out on continuous fibre-reinforced epoxy resin with a [+45/−45]2s fibre orientation and the neat matrix material itself, up to temperatures above the glass transition area. Wicket plots indicated thereby that the temperature–time superposition is applicable for both material systems. A comparison of the two material systems showed, that the fibre-reinforced specimen is shifted horizontally to a greater extent.
Green backfill materials enhance slope stability and support sustainable mining in open-pit mines. However, current research mainly focuses on traditional loose fills, neglecting eco-friendly cementitious alternatives. In this study, the potential of waste rock-based geopolymers as mine backfilling materials were proved. Specifically, the compressive strength test was conducted to evaluate the effect of materials interaction, aggregate gradation index, alkali activator dosage, water-to-binder ratio and waste rock utilization rate on the strength. And acoustic emission (AE) technology was used to clarify fracture mechanisms of materials. Results demonstrated high-temperature treatment improves the compressive and flexural strength of waste rock-based paste, with calcined waste rock powder effectively enhancing fly ash reactivity. Increasing slag replacement reduces compressive strength linearly, with 5 MPa decline per 10 % increase in slag content. In addition, specimens with on-site gradation aggregate or higher alkali activator dosage exhibit superior strength. The water-binder ratio around 0.4 and 1:5 waste rock utilization ratio enhances reaction dynamic, maximizing compressive strength. Furthermore, the stress-strain process includes four distinct stages: the compaction and elastic stage, stable crack growth stage, unstable crack growth stage and the post-peak stage. Failure patterns predominantly feature single-slope shear fractures, with cracks concentrated in middle and upper areas of specimen. This study contributes to sustainable resource utilization and green mine construction.
Andrea Paola Rodriguez, Amanda Guadalupe Romero, Silvia Noemi Kozuszko
et al.
The human body, once regarded primarily as a spiritual vessel, is now understood as a highly complex biological system governed by intricate cellular and molecular processes. As civilizations and technologies have evolved, so too have the methodologies, materials, and epistemologies surrounding wound care. From herbal applications in ancient cultures to the development of bioengineered dressings in contemporary medicine, the field of wound healing reflects a continuous trajectory of innovation and adaptation. This review presents a concise overview of wound management practices across diverse cultural contexts, highlighting the contributions of ancestral knowledge systems. It further examines the current landscape of wound dressing technologies, with particular emphasis on soft materials engineered, such as polymers, gels, and foams, to optimize healing outcomes in both acute and chronic wounds. In seeking deeper integration of ancestral knowledge into biomedical innovation, this review explores clinical trials, patent activity, regulatory standards, and epistemological considerations related to medicinal plant applications. By honoring origin and embracing plural knowledge systems, we aim to advance the development of wound care nanotechnologies that are not only scientifically robust but also culturally inclusive, ethically grounded, and accessible across diverse healthcare settings. The second part of this review summarizes tissue engineering in the market and clinical trials, plant-based remedies and pharmacopoeias, medicinal activities of the plants, analyzing skin wound healing from traditional cataplasm to advanced wound dressings within a holistic framework.
Chemistry, Medical physics. Medical radiology. Nuclear medicine
Abstract The tremendous interest received by additive manufacturing (AM) within the biomedical community is a consequence of the great versatility offered in terms of processing approach, materials selection, and customization of the resulting device. In particular the unparalleled control over structural and compositional features at the macro- and microscale, as a result of the large design freedom and high reproducibility, is making AM the technology of election for the fabrication of biodegradable medical devices. This article is aimed at providing an update overview of scientific literature on biodegradable polymers for AM application in the biomedical field. The main AM techniques applied so far to biodegradable polymers are outlined by presenting relevant materials processing requirements. The different classes of biodegradable polymers investigated for AM (i.e., proteins, polysaccharides, aliphatic polyesters of either natural or synthetic origin, polyurethanes, as well as other synthetic polymers under AM implementation) are described by highlighting their source of extraction, chemical modification, or synthesis route, and their physical-chemical and processing properties in relationship to AM. Relevant literature on their AM processing for medical and pharmaceutical applications is accordingly reviewed.
3D printing has changed the fabrication of advanced materials as it can provide customized and on‐demand 3D networks. However, 3D printing of polymer materials with the capacity to be transformed after printing remains a great challenge for engineers, material, and polymer scientists. Radical polymerization has been conventionally used in photopolymerization‐based 3D printing, as in the broader context of crosslinked polymer networks. Although this reaction pathway has shown great promise, it offers limited control over chain growth, chain architecture, and thus the final properties of the polymer networks. More fundamentally, radical polymerization produces dead polymer chains incapable of postpolymerization transformations. Alternatively, the application of reversible deactivation radical polymerization (RDRP) to polymer networks allows the tuning of network homogeneity and more importantly, enables the production of advanced materials containing dormant reactivatable species that can be used for subsequent processes in a postsynthetic stage. Consequently, the opportunities that (photoactivated) RDRP‐based networks offer have been leveraged through the novel concepts of structurally tailored and engineered macromolecular gels, living additive manufacturing and photoexpandable/transformable‐polymer networks. Herein, the advantages of RDRP‐based networks over irreversibly formed conventional networks are discussed.