Silk biomaterials are a class of materials derived from silk proteins obtained from various sources, ranging from domesticized silkworms to spiders and even underwater organisms. As substrates for biomaterial construction, silk proteins offer a wide array of unique properties and functionalities, including exceptional mechanical strength, biocompatibility, relative ease of chemical modifications, and many more. The field of silk biomaterials is rapidly evolving, driven by interdisciplinary research and technological innovations. Recent advances in basic science, particularly new insights into structural transitions in silk proteins, the physicochemical characteristics of silk-rich fluids, and the untangling of the high complexity of natural processing conditions developed through millions of years of evolution, offer a promising perspective for creating a new generation of improved materials capable of addressing various healthcare-related challenges. This review discusses and summarizes the latest advances in both basic science and technological developments in silk-based biomaterials, focusing specifically on how concepts from fundamental science and engineering technologies are implemented to fabricate biomaterials with tunable performance and customizable function. Further exploration and understanding of silk's properties at both the molecular and supramolecular levels will likely lead to promising novel applications in medicine, ultimately improving patient outcomes across various therapeutic areas.
Vat photopolymerization, or light-based 3D printing via curing of liquid resins, is a class of additive manufacturing expected to serve an important role in the future of manufacturing. New light-based 3D printing modalities have emerged that rely on different wavelengths of light, methods of light projection, or chemical strategies to initiate and control the formation of a polymer network. Advances in photocatalysis and photochemical transformations will continue to propel the development of new resins, broadening the scope of material properties achievable with light-based 3D printing. As new resins become available, scientists and engineers can leverage molecular attributes as well as the architecture of the printed object toward an emergent functionality. This review highlights important developments in the chemistry and materials for light-based 3D printing, with a particular focus on the impact of these technologies in health care, sustainability, and 4D fabrication.
Rapid sintering using a high heating rate is growing in technological and scientific interest. This is motivated by the promise of reducing the carbon footprint of sintering and developing materials with properties and microstructures different from those achievable by conventional heating. For instance, rapid heating can induce suppression of grain growth, the possibility of obtaining modified space charges and elemental segregations, and the development of out-of-equilibrium materials. Severe challenges still exist for the industrial exploitation of rapid sintering technologies, and, nowadays, only fast firing can be considered mature. Most of these limitations are related to the homogeneity of the sample and the possibility of obtaining complex shapes. This review investigates developments in rapid sintering by comparing different processes, suggested mechanisms, and future challenges.
Metal additive manufacturing (AM) holds immense potential for developing advanced structural alloys. However, the complex, heterogeneous nature of AM-produced materials presents significant challenges to traditional material characterization and optimization methods. This review explores the integration of artificial intelligence (AI) and machine learning (ML) with high-throughput material characterization protocols to rapidly establish the process–structure–property (PSP) relationships critically needed to dramatically accelerate the development of metal AM processes. Combinatorial high-throughput evaluations, including rapid material synthesis and nonstandard high-throughput testing protocols, such as spherical indentation and small punch tests, are discussed for their capability to rapidly assess mechanical properties and establish PSP linkages. Furthermore, the review examines the role of AI and ML in optimizing AM processes, particularly through Bayesian optimization, which offers new avenues for efficient exploration of high-dimensional design spaces. The review envisions a future where AI- and ML-driven, autonomous AM development cycles significantly enhance material and process optimization.
The properties of chalcogenide phase change materials have long attracted the scientific community due to a combination of state retention (i.e., memory) and a large contrast in electrical and optical properties between different solid phases. The last decade has witnessed a vast interest in utilizing this material family for optics and photonics, given their large refractive index modulation, nonvolatility—elusive in optics—and straightforward integration into photonic devices. Thus, designing new optical phase change materials (O-PCMs) and demonstrating high-performance applications have become fast-growing research topics. However, advances in O-PCMs have predominantly followed empirical device developments, driven by their promise in trending technological applications. Nonetheless, a growing interest in revealing their materials science intricacies is driving the much-needed effort toward a holistic understanding and codesign of O-PCMs, which is required to fill knowledge gaps, expand the materials library, and solve the most pressing device performance challenges.
Doped and mixed oxides are a class of materials with widespread applications, ranging from electronics to energy storage. The precise determination of ion valency in these materials is crucial for understanding their electronic, ionic, magnetic, and other properties, as well as controlling behaviors during processing and microstructure development. In this review, we present magnetometry measurement as a powerful tool to determine ion valency and position in doped and mixed oxides. Focus is given to transition metals in dilute concentrations. We discuss the theoretical framework, experimental techniques, data analysis methods, and case studies that showcase the effectiveness of magnetometry in elucidating the valency of ions in various oxide systems. The results highlight the importance of magnetometry as a nondestructive and highly sensitive technique for characterizing the valence states and positions of dopant ions. They position magnetometry as a valuable member of the suite of complementary advanced tools for characterizing ion valency.
Organic semiconductors (OSCs) offer the capacity for distinctive and finely tuned electronic, optical, thermal, and mechanical properties, making them of interest across a range of energy generation and storage, sensor, lighting, display, and electronics applications. The pathway from molecular building block design to material, however, is complicated by complex synthesis– processing–structure–property–function relationships that are inherent to OSCs. The adoption of artificial intelligence (AI) tools, including the subset of AI referred to as machine learning (ML), into the materials design and discovery pipeline offers significant potential to overcome the multifaceted roadblocks along this pathway. Here, we review recent advances in the application of AI/ML for OSCs, with a focus on the development and use of ML. We present a brief primer on ML models and then highlight efforts wherein ML is used to predict molecular and material properties and discover new molecular building blocks and OSCs.
From a microstructural standpoint, chocolate is a suspension of solid particles—including cocoa solids, sugar crystals, and sometimes milk solids—in a continuous lipid (cocoa butter) phase. The proportions and types of ingredients dictate the melting profile and rheology of the chocolate, which in turn have significant implications for its physical and sensory properties. In this review, we discuss the effects of ingredients and processing on the microstructural, rheological, and sensory properties of chocolate. Applicable rheological models are covered, as well as a brief overview of bloom. Finally, we suggest directions for future research.
The introduction of self-healing behavior into polymeric materials is attractive for improving their longevity in a vast array of applications. Notably, intrinsic self-healing, achieved through exploitation of reversible or dynamic interactions between polymer chains, has shown significant advances in recent years. However, characterization of self-healing varies markedly across the literature, and true insight into the mechanism and cyclability is often limited. Therefore, this review explores the various mechanisms and chemistries behind intrinsic self-healing polymers, with a specific focus on their use in diverse optical applications. We also discuss the methods currently used to investigate self-healing behavior of polymers across the literature, with a view to establishing guidelines for the best practice in characterizing these materials.
The characterization of archaeological ceramics involves mineral composition studies of the ceramic mass and investigations of associated organic residues. Analyses of the mineral composition of the ceramic mass are conducted to determine the origin of the raw materials, the production technologies used to create the ceramic, and the history of the objects. Contemporary ceramics research pays much attention to analyzing organic residues, which provide valuable information about the diet, cooking practices, and vessel use of ancient communities. This article discusses examples of the use of various analytical techniques, with particular emphasis on spectroscopic and chromatographic methods. The crucial importance of validating research methods and interdisciplinary cooperation is also discussed.
Resonant soft X-ray scattering (RSoXS) is a powerful tool for chemically and orientationally resolved nano-to-mesoscale characterization of complex molecular materials. Through its development over the past 15 years, its use has been extended to uniquely characterize structures, not only dry, thin films for devices, coatings, photolithography, and liquid crystalline ordering, but also solvated nanostructures in biology for therapeutics and hydrated membranes for filtration or biosensing. Here, we review progress in this exciting and maturing technique with an eye toward the materials scientist or engineer who has little experience with RSoXS but would like to know more about how the technique would fit into their toolset.
This review covers the anelastic deformation observed under electric loading (electroplasticity) of metals and ceramics. The interplay of various complex mechanisms beyond trivial Joule heating leading to enhanced plasticity is discussed in the context of both materials classes. In the case of metals, electromechanical coupling resulting in forces being exerted on atoms and dislocations is elucidated. In the case of ceramics, change in the grain boundary structure is proposed to justify the enhanced plasticity. Microstructural evidence is analyzed in correlation with the deformation behavior.
Conductive and radiative thermal transport play a critical role in the design, development, and performance of a wide array of technologies and applications. In this review, we focus on the challenges associated with nano- and microscale thermal measurements and the strategies developed thus far to overcome them. For measurements below ∼1,000°C, numerous thermoreflectance techniques are already in wide use; however, uncertainty and measurement error may limit the measurement of samples in certain regimes. These regimes include materials of high thermal conductivity (≳2,000 W/m·K), thin films (≲100 nm), or interfaces located well below the sample surface. A rigorous treatment of uncertainty and error is thus required for measuring these samples and for the development of future metrology tools. At higher temperatures, pyrometry techniques are being developed; however, several physical and experimental limitations exist. Some methods rely on a known emissivity for the measurement of temperature, and significant radiative transport can introduce error in modeling. Both of these mean that knowledge of spectrally dependent and temperature-dependent emissivity properties may be required.
When a material is cyclically loaded, an amplitude of load exists, called the threshold, below which a crack does not grow. In a polymeric material, physical interactions between polymer chains are much weaker than covalent bonds between repeat units along an individual chain. Consequently, when a crack impinges on a chain, high tension transmits along a long length of the chain. Breaking a single covalent bond dissipates the energy stored in that long length. The longer the length over which high tension transmits, the higher the threshold. Here we review how stress deconcentrates in diverse polymeric materials, including polymer networks, particle-reinforced elastomers, glassy polymers, semicrystalline polymers, phase-separated polymers, and composites. Ample opportunities exist for investigation and innovation.
In the rapidly evolving rechargeable battery market, various applications lead to varied property requirements. One area that is emerging as essential is high-power batteries. These are expected to be able to charge and discharge in the order of minutes (slower than supercapacitors but faster than typical Li-ion batteries) and still have a high energy density (orders of magnitude higher than that of supercapacitors but lower than that of high-energy Li-ion batteries). In this space, anodes operating at a safe potential (near 1.5 V versus Li) sacrifice some energy density but enable fast cycling and lead to very safe batteries. In this review, we explore the plethora of materials being considered in the literature as potential high-power anodes. Though Nb-based anodes are prominent due to their recent popularity in the literature, any material classes leading to the appropriate balance of power and energy are discussed. We, in particular, aim to distinguish materials that are suitable only for supercapacitors from those with the potential for practical batteries, distinguished by volumetric energy density. The best materials discussed herein show excellent specific capacities and fast cycling performance, though a greater focus on performance at practical loadings is generally required.
A hydrogen-based economy relies on the use of steel components such as containers for storage, pipelines for transport, or bipolar plates in fuel cells. All these components suffer from hydrogen embrittlement if common, inexpensive steels are used. For a widespread application of hydrogen, hydrogen ingress into and through the steel must be minimized. A powerful solution is hydrogen permeation barrier layers. They can be obtained by surface modifications using chemical treatments such as nitriding or carburizing and mechanical treatments such as peening, or by deposition of protective coatings. In this review, hydrogen embrittlement mechanisms and the role of individual defects are briefly described, followed by a detailed description of the advantages and disadvantages of the different types of hydrogen permeation barrier layers. As the mechanical properties of the layers are important for applications, an outlook on how small-scale mechanical tests can be used for their characterization is presented.
The evolution of ferroelectric devices is driven by advancements in materials science, device physics, and engineering. However, depolarization fields and interfacial disorder limit the scaling performance, endurance, and reliability of conventional thin-film ferroelectrics. van der Waals (vdW) ferroelectric materials exhibiting novel properties at the atomic scale are interesting candidates for mitigating the aforementioned issues, thereby allowing for improved ferroelectric device performance. In this review, we discuss the unconventional origins of both spontaneous and artificial polarization, along with their associated switching mechanisms, in polar and nonpolar vdW ferroelectric crystals and heterostructures. Recent device architectures utilizing vdW ferroelectricity are reviewed with a specific focus on emerging memory, steep-slope logic, and in-memory computing applications. We conclude with an overview of the opportunities and challenges for vdW ferroelectrics related to scalability, endurance, device integration, and growth, highlighting recent advances toward manifesting next-generation electronics.
Ceramics are typically brittle at ambient conditions due to their covalent or ionic bonding and limited dislocation activities. While plasticity, and occasionally superplasticity, can be achieved in ceramics at high temperatures through thermally activated phenomena, creep, and grain boundary sliding, their deformation at ambient temperature and pressure remains challenging. Processing under high pressure via the high-pressure torsion (HPT) method offers new pathways for severe plastic deformation (SPD) of ceramics. This article reviews recent advances in HPT processing of ceramics, focusing primarily on traditional ceramics (e.g., oxides, carbides, nitrides, oxynitrides) and to a lesser extent advanced ceramics (e.g., silicon, carbon, perovskites, clathrates). Key structural and microstructural features of SPD-processed ceramics are discussed, including phase transformations and the generation of nanograins and defects such as vacancies and dislocations. The properties and applications of these deformed ceramics are summarized, including powder consolidation, photoluminescence, bandgap narrowing, photovoltaics, photocatalysis (dye degradation, plastic waste degradation, antibiotic degradation, hydrogen production, CO2 conversion), electrocatalysis, thermoelectric performance, dielectric performance, and ion conductivity for Li-ion batteries. Additionally, the article highlights the role of HPT in synthesizing novel materials, such as high-entropy ceramics (particularly high-entropy oxides), black oxides, and high-pressure polymorphs, which hold promise for energy and environmental applications.
It has long been assumed that all matter will assume simple closed-packed lattices and become metallic under pressure, in accordance with the Thomas-Fermi-Dirac (TFD) model. However, this model struggles to explain pressure driven complex structural transitions that have been observed in elements, including sodium, challenging our conventional understanding of compressed matter. Moreover, in stark contrast to the TFD picture, first-principles calculations suggest that various elements and compounds become electrides under pressure. Electrides, characterized by concentrations of charge density at interstitial regions, can be thought of as ionic compounds where electrons behave as the anions. Though ambient-pressure molecular electrides have been extensively studied via experiments and computations, high-pressure electrides (HPEs) are not well understood. The identification and characterization of HPEs has been, to date, purely based on theory including topological analysis of the electron density and the electron localization function. Here, we review these theoretical analyses tools and suggest guidelines that can be used to classify systems as electrides. Moreover, we describe models used to rationalize the electronic structure of HPEs, drawing parallels with ambient pressure molecular systems, and urge for the development of experimental techniques that provide evidence for the theoretically calculated charge localization.
Polymer vesicles and lipid nanoparticles are supramolecular structures with similar physicochemical properties that are self-assembled from different amphiphilic molecules. Because of their efficient drug encapsulation capability, they are good candidates for drug delivery systems. In recent years, nanoparticles with different compositions, sizes, and morphologies have been applied to the delivery of a wide variety of different therapeutic molecules, such as nucleic acids, proteins, and enzymes; their remarkable chemical versatility allows for customization to specific biological applications. In this review, design approaches for polymer vesicles and lipid nanoparticles are summarized with representative examples in terms of their physicochemical properties (size, shape, and mechanical features), preparation strategies (film rehydration, solvent switch, and nanoprecipitation), and applications (with a focus on diagnosis, imaging, and RNA-based therapy). Finally, the challenges limiting the transition from laboratory to clinical application and future perspectives are discussed.
