Materials Science and Engineering: R: Reports最新文献

Natural biomaterials have benefited the human civilisation for millennia. However, in recent years, designing of natural materials for a wide range of applications have become a focus of attention, spearheaded by sustainability. With advances in materials science, new ways of manufacturing, processing, and functionalising biomaterials for structural specificity has become feasible. Our review is focused on bacterial cellulose (BC), an exceptionally versatile natural biomaterial. BC is a unique nanofibrillar biomaterial extruded by microscopic single- cell bacterial factories utilising the chemical energy harvested from renewable substrates. BC is extracellular and is intrinsically pure, unlike other biopolymers that require extraction and purification. BC fibres are 100 times thinner than plant-derived cellulose and exist in a highly porous three-dimensional network that is highly biocompatible. Macro fibres fabricated from BC nanofibrils are stronger and stiffer, have high tensile strength values and can be used as substitutes for fossil fuel-derived synthetic fibres. The increased surface area to volume ratio allows stronger interactions with the components of composites that are derived from BC. The reactive hydroxyl groups on BC allows various chemical modifications for the development of functionalised BC with a plethora of ‘smart’ applications. In this review we consolidate the current knowledge on the production and properties of BC and BC composites, and highlight the very recent advancements in bulk applications, including food, paper, packaging, superabsorbent polymers and the bio-concrete industries. The process simplicity of BC production has the potential for large scale low-cost applications in bioremediation. Furthermore, the emerging high value applications of BC will be in electrochemical energy storage devices as a battery separator, and in transparent display technologies will be explored. Finally, the extensive biomedical applications of BC are discussed including, wound healing, controlled drug delivery, cancer treatment, cell culture and artificial blood vessels. In a further development on this, additive manufacturing considers enhancing the capabilities for manufacturing complex scaffolds for biomedical applications. An outlook on the future directions of BC in these and other innovative areas is presented.

Personal protective equipment (PPE) is crucial for ensuring occupational safety when handling toxic chemicals or in close contact with biological pathogens. The increased poisoning and infection cases outside the working scenario have attracted public attention, which drove the development and application of PPE for the professionals and the public. The use of PPE can effectively lower the risk of acute and chronic diseases caused by pesticide exposures and significantly reduce the spread of infectious diseases. However, conventional PPE mostly only functions as physical blocking or electrostatic repulsion materials, which still poses potential risks caused by cross- and post-contamination from the PPE. Although sensors are not usually considered as a necessary component of PPE, the detection of health threats in the environment could benefit preparations for unprepared risks promptly, especially in non-occupational situations, thus improving the protection of human safety. In this review, we discuss the needs of novel PPE by surveying some insufficient protection cases and threats that occurred during conventional PPE applications. Then, we summarize recent progress in developing single-functional decontamination and colorimetric sensing PPE, mostly fiber-based media against agricultural toxicants and microorganisms, with intension to inspire the future design of novel PPE with the integrated “decontamination-and-sensing” property. Some recently developed conventional dual-functional materials against either pesticide or microorganism exposures are highlighted. Finally, strategies and limitations of developing decontamination and sensing material using unique interactions and reactions of targets with functionalized fibrous substrates are discussed by comparing the successful approaches and practical challenges in PPE applications.

The prevalence of bacterial infections and resistance to existing antibiotics make new effective antibacterial strategies urgently needed. Photocatalytic antibacterial, an effective strategy relying on exogenous excitation, has drawn increasing attention over the past decades, owing to its controllable, safe, and non-invasive characteristics. Many photoresponsive agents have been developed. With exceptional features of abundance, facile synthesis, suitable band structure, high stability, and low toxicity, metal-free polymeric two-dimensional nanomaterial graphitic carbon nitride (g-C₃N₄) is an attractive photosensitizer for antibiotic-free antibacterial application. In this review, the basic structural characteristics and preparation methods of g-C₃N₄ are summarized. The photocatalytic antibacterial mechanism of g-C₃N₄ through reactive oxygen species (ROS) generation is also discussed. In order to achieve more precise and efficient antibacterial effects, we pay special attention to two aspects: (1) how to increase the utilization of visible light and reduce the recombination of electron-hole pairs, thereby enhancing the production of ROS; and (2) how to obtain effective bacteria-killing activity while maintaining good biocompatibility and environmental friendliness, which determines the practical applications of materials. Several significant modification strategies are thus introduced, including structure design, surface modification, element doping, and construction of g-C₃N₄-based heterojunctions. Furthermore, various typical examples of combining the photocatalytic antibacterial effect of g-C₃N₄ with other strategies to exert good synergistic effects are summarized. Lastly, the potential challenges and perspectives are offered. This review is expected to inspire more follow-up work to design high-performance g-C₃N₄-based materials for photocatalytic antibacterial application.

Bulk metallic glasses (BMGs) being metallic materials without long-range order have attracted a considerable amount of interest from academia and industry in the past three decades due to their unique and outstanding properties. However, the manufacturing of glassy components with large dimension and complex geometries has remained a considerable challenge. The main obstructions in this regard arise from the oftentimes limited glass-forming ability (GFA) of most metallic systems, which requires extremely fast quenching of the corresponding melts and, consequently, limits the obtainable dimensions. In addition, BMGs generally have a poor machinability due to their intrinsic high hardness and extreme brittleness. The emerging 3D printing technology (also called additive manufacturing), as an advanced bottom-up manufacturing process, seems to be a viable route to circumvent these deficiencies inherent to conventional processing routes. Additive manufacturing theoretically allows the fabrication of large-sized BMGs and components with complex geometries, greatly extending the range of applications of BMGs as both structural and functional materials. The 3D printing technology has given fresh impetus to the field of BMGs and represents an approach, which is intensely explored in the BMG’s scientific community at the moment. In this review, we present a comprehensive overview of the state-of-the-art research on various aspects related to 3D printing of BMGs. It covers various 3D printing techniques for manufacturing BMGs, the microstructures (e.g. structural heterogeneities and fused-related defects) found in 3D-printed BMGs, the crystallization behavior in additively manufactured glasses and the associated alloy selection criterion, the observed mechanical properties and deformation mechanisms, and finally the functional properties and potential applications of 3D-printed BMGs and BMG matrix composites, in terms of catalysis, wear, corrosion, and biocompatibility. This article also identifies a number of key questions to be answered in the future in this important research direction in order to successfully bridge the gap from fundamental research to large-scale application of additively manufactured bulk metallic glasses.

Additive manufacturing (AM), also known as three-dimensional (3D) printing, has boomed over the last 30 years, and its use has accelerated during the last 5 years. AM is a materials-oriented manufacturing technology, and printing resolution versus printing scalability/speed trade-off exists among various types of materials, including polymers, metals, ceramics, glasses, and composite materials. Four-dimensional (4D) printing, together with versatile transformation systems, drives researchers to achieve and utilize high dimensional AM. Multiple perspectives of the AM of structural materials have been raised and illustrated in this review, including multi-material AM (MMa-AM), multi-modulus AM (MMo-AM), multi-scale AM (MSc-AM), multi-system AM (MSy-AM), multi-dimensional AM (MD-AM), and multi-function AM (MF-AM). The rapid and tremendous development of AM materials and methods offers great potential for structural applications, such as in the aerospace field, the biomedical field, electronic devices, nuclear industry, flexible and wearable devices, soft sensors, actuators, and robotics, jewelry and art decorations, land transportation, underwater devices, and porous structures.

Emulating the unique combination of structural, compositional, and functional gradation in natural materials is exceptionally challenging. Many natural structures have proved too complex or expensive to imitate using traditional processing techniques despite recent manufacturing advances. Recent innovations within the field of additive manufacturing (AM) or 3D Printing (3DP) have shown the ability to create structures that have variations in material composition, structure, and performance, providing a new design-for-manufacturing platform for the imitation of natural materials. AM or 3DP techniques are capable of manufacturing structures that have significantly improved properties and functionality over what could be traditionally-produced, giving manufacturers an edge in their ability to realize components for highly-specialized applications in different industries. An example of how these techniques can be applied towards a total hip arthroplasty application is provided to spur further innovation in this area.To this end, the present work reviews fundamental advances in the use of naturally-inspired design enabled through 3DP / AM, how these techniques can be further exploited to reach new application areas, and the critical issues that lie ahead for widespread implementation to solve long-standing as well as emerging scientific challenges.

Transient electronics, which can be tuned to be completely or partially dissoluble, degradable, and disintegrable, create new opportunities in the upcoming ubiquitous electronics era that are inaccessible with conventional permanent electronics. This emerging field offers unique electronic applications in environmentally degradable eco-devices with minimal or zero waste, biodegradable medical implants not requiring secondary removal surgery, and hardware-based security devices with self-destructing circuits. Nanoscale thin-film processing that exploits Si in single-crystalline form and related techniques allow construction of transient electronics with high performance and versatile characteristics, including nearly all types of active electronic components, integrated circuits, sensors and other integrated wireless medical devices. Here we review recently developed transient electronics and materials, mainly illustrating representative inorganic and Si electronic materials technologies. Dissolution chemistry and reaction kinetics of semiconductors, dielectric and metal conductors are described to explain the dependence on environmental conditions such as temperature, pH, ion species and materials microstructure, density, crystallinity, composition. Materials and approaches that define the functional lifetime of transient electronic are introduced in two aspects: using passive encapsulation layers to control water-vapor diffusion and using on-demand active triggerable systems of stimulus-responsive materials. Transfer-printing approaches and solution printing processes offer strategies to integrate high-performance inorganic electronic materials with soft and flexible biodegradable organic substrates. Various examples of biodegradable medical electronics for clinically relevant diseases and symptoms support effective practical applications.

Two-dimensional (2D) materials such as graphene and molybdenum disulfide et al. offer significant new prospects for electronics, optics, and biosensing applications due to their unique physical and chemical properties. The controlled manipulation of such materials to create three-dimensional (3D) architectures is an intriguing approach to favorably tuning their properties and creating new types of 3D devices with small form factors. However, 2D materials exhibit extremely low bending stiffnesses compared with traditional functional materials, therefore, it is rather challenging to obtain stable 3D structures under van der Waals (vdW) interaction despite the easier out-of-plane manipulation. The centuries-old paper-shaping techniques named as ‘kirigami’ and ‘origami’ may provide a potential solution to this deadlock. The general idea is that through pre-patterning and mechanical deformations, 2D materials can be reshaped and transformed into 3D structures on demand, which extends the application of kirigami/origami from conventional functional films to atomically thin nanosheets. This kind of shaping and structuring strategy not only integrates 2D materials with 3D micro/nano-structures in a controllable manner, but also offers a new paradigm for tailoring the properties of 2D materials, thus enabling more functions beyond the capability of planar geometry. Such 3D micro/nano-architectures containing engineered 2D materials can provide a platform to explore the frontier physics and produce micro/nano-devices with improved performance or unprecedented functionalities. Hence, it is necessary to review the recent progress in this emerging field, which combines the exemplary kirigami/origami strategy with promising 2D materials to increasingly inspire the multidisciplinary applications. This review focuses on 2D materials kirigami/origami, including intrinsic and engineered properties, mechanisms, methods and applications. The research challenges and opportunities are also discussed to promote future theoretical and technological studies in this blooming interdisciplinary field.

As one of the most complex structures in nature, butterflies have attracted wide interest over the past few decades. Inspired by these delicate structures and the marvelous derived properties, scientists have investigated and biomimetic fabricated several designs to replicate the structure and to apply the functional features. Here, we present up-to-date researches concerning butterfly-inspired functional materials in different fields. After introducing the basic properties and corresponding structures, the bio-mimic fabrication methods are clarified and concluded. We then concerned about the applications, combining the modified butterfly wing and the fabricated replicas. The challenges and prospects of the further development of the butterfly inspired functional materials are conclusively presented.

Additive manufacturing of industrially-relevant high-performance parts and products is today a reality, especially for metal additive manufacturing technologies. The design complexity that is now possible makes it particularly useful to improve product performance in a variety of applications. Metal additive manufacturing is especially well matured and is being used for production of end-use mission-critical parts. The next level of this development includes the use of intentionally designed porous metals - architected cellular or lattice structures. Cellular structures can be designed or tailored for specific mechanical or other performance characteristics and have numerous advantages due to their large surface area, low mass, regular repeated structure and open interconnected pore spaces. This is considered particularly useful for medical implants and for lightweight automotive and aerospace components, which are the main industry drivers at present. Architected cellular structures behave similar to open cell foams, which have found many other industrial applications to date, such as sandwich panels for impact absorption, radiators for thermal management, filters or catalyst materials, sound insulation, amongst others. The advantage of additively manufactured cellular structures is the precise control of the micro-architecture which becomes possible. The huge potential of these porous architected cellular materials manufactured by additive manufacturing is currently limited by concerns over their structural integrity. This is a valid concern, when considering the complexity of the manufacturing process, and the only recent maturation of metal additive manufacturing technologies. Many potential manufacturing errors can occur, which have so far resulted in a widely disparate set of results in the literature for these types of structures, with especially poor fatigue properties often found. These have improved over the years, matching the maturation and improvement of the metal additive manufacturing processes. As the causes of errors and effects of these on mechanical properties are now better understood, many of the underlying issues can be removed or mitigated. This makes additively manufactured cellular structures a highly valid option for disruptive new and improved industrial products. This review paper discusses the progress to date in the improvement of the fatigue performance of cellular structures manufactured by additive manufacturing, especially metal-based, providing insights and a glimpse to the future for fatigue-tolerant additively manufactured architected cellular materials.