Over the past five years, artificial intelligence (AI) has grown significantly in different aspects of our daily lives, including health, transportation, and the digital world, all by leveraging data. Inspired by these success stories, materials researchers have started to adopt AI in experimental materials science to accelerate materials discovery and development by 10–100× through improving the efficiency of hypothesis generation, testing, and data analysis in a closed-loop fashion. This issue of MRS Bulletin presents a collection of papers discussing the recent advancements of AI in different aspects of experimental materials science and provides a framework for the next generation of autonomous experimentation strategies. In this article, we review the role of AI in experimental materials science and summarize the key aspects and challenges of autonomous experimentation discussed in each contributed article. We pose four questions at the interface of AI and experimental materials science, and present immediate calls for action for researchers working in this emerging field to move beyond optimization toward autonomous discovery. We hope this issue can accelerate convergence as well as flexibility and reconfiguration of hardware and software modules of autonomous robotic experimentation techniques to enable true digitalization of materials synthesis.Graphical abstract

Engineered tissues and organs that approximate the sizes and functions of actual organs hold great promise for advancing medicine and pharmacology. However, significant challenges remain in producing clinically relevant biofabricated constructs using traditional tissue-engineering techniques. The use of three-dimensional volumetric bioprinting technology is expected to enable the creation of large-scale functional organs for various applications. In this article, we discuss key considerations for creating volumetric functional tissue constructs, particularly using bioprinting technology. In addition, we critically evaluate the advantages and limitations of current volumetric bioprinting techniques, and highlight recent advances in volumetric bioprinting applications that can address the donor organ shortage and the lack of reliable in vitro models.Graphical abstract

AbstractFor the last 500 years, the West has mapped Africa as a source of raw materials, disrupted vibrant African value addition, and arrogated itself as the place where industrial revolutions (value addition) happen. This strategy is clearly traceable from the transatlantic slave trade, continuing through European colonialism, to the current critical raw materials (CRMs) framing necessary for its digital and climate tech dominance. African countries have realized that continuing to export materials raw is an unsustainable path of dependency. Emphasis is now on value addition, which is the norm in everyday life, rendered informal, marginal, even illegal under colonialism and never revisited, recentered, and formalized after independence. This article takes minerals as an example of indigenous value addition and how the transatlantic slave trade and colonial rule destroyed it and inserted in its place extractive infrastructures of CRMs export that have remained intact since independence. The last half of the essay switches to Africa’s pivot to value addition, zeroing in on Zimbabwe and the Democratic Republic of the Congo as case studies, focusing on chrome, cobalt, and lithium. These minerals constitute the basis for the electric vehicle, smartphone, lithium-ion battery, semiconductor, and other electronic manufacturing to supply the newly created African Continental Free Trade Area, an internal market of 1.3 billion people. The article ends with a discussion of four major challenges to value addition—energy, finance, markets, and skills—and how Africa is meeting and could meet them. The reader is invited to consider the implications of a world order in which Africa is no longer exporting its materials raw, but becomes the center of global manufacturing, adding value to its own materials.Graphical abstract

As materials scientists and engineers, we have the responsibility and ability to make sustainability a reality by creating and implementing sustainable materials and processes. It is, after all, the materialization of our needs and wants that have led to the current situation. However, we need to have the will to do it, know what to do, and how to do it. We must learn what sustainable options are possible, learn to choose among the options based on societal, environmental, and economic concerns, and learn how to work with others to make decisions that change the status quo. This leads to the questions: what community is prepared to act with us and how can we educate people to make a difference? As discussed in this article, the answer is the microelectronics industry. There is a growing recognition that microelectronics both cause and prevent societal and environmental problems. It is there, in the context of these problems and the growing importance and proliferation of microelectronics in our everyday lives, that we can forge partnerships to simultaneously solve sustainability issues and teach materials science and engineering students to become leaders in sustainable electronics.Graphical Abstract

Throughout human history, the capacity to invent, manufacture, and use chemicals and materials has transformed concepts of development with path-dependent solutions to problems encountered in various industrial and societal sectors, including energy, transportation, food production, textiles, and personal care. It is increasingly clear that the trajectory of development initiated by some path-breaking materials is not sustainable. Recent developments in the concept of planetary boundaries have explored some reasons for unsustainability and ineffectiveness of current chemicals management practices. The reasons are almost always due to previously unknown chemical characteristics such as toxicity, reactivity, environmental recalcitrance, or increasing scarcity. In some cases, the suspected but ignored potential hazard of chemicals manifests slowly or becomes uncontrollable due to accumulation and biochemical or physical transformation in the environment. Consequently, environmental pollution by such chemicals is associated with alarmingly high levels of human mortality and disease burden worldwide. Recent examples include halogenated chemicals used as flame retardants and the thinning of the stratospheric ozone layer; bisphenol A used in plastics and microplastics widespread in biotic and abiotic ecosystem components, including the ocean; hormone mimicking chemicals such as phthalates in human tissues; neurotoxicity of lead used in solder materials, paints, and water distribution pipes; neurodevelopmental diseases associated with mercury used in ore beneficiation, in dental amalgams and lighting systems; and asbestos fibers used in ceiling tiles, roofs, and automobile brakes. These notorious examples have forced the introduction of retroactive policies to restrict the use of certain chemicals in materials development, and a few proactive policies designed to prevent the initial use of certain chemicals known or suspected to be hazardous. Improvements in the scientific knowledge and development of tools to screen for chemicals of concern have also led to the development of forecasting tools for improved management of chemicals. It could be impossible to foresee all potential risks associated with chemicals. Therefore, such management approaches can be most effective in supporting sustainable development of materials when they generate boundaries within which criteria for safety are understood and alternative assessments are continuous. This article situates the power of selected forecasting tools for early warning systems in a planetary boundary framework while highlighting gaps and incongruencies inherent in their use to support proactive and reactive regulatory policies, and for developing performance standards for lowering the chemical footprint of consumer products.Graphical Abstract

Materials innovation has arguably played one of the most important roles in the development of implantable neuroelectronics. Such technologies explore biocompatible working systems for reading, triggering, and manipulating neural signals for neuroscience research and provide the additional potential to develop devices for medical diagnostics and/or treatment. The past decade has witnessed a golden era in neuroelectronic materials research. For example, R&D on soft material-based devices have exploded and taken center stage for many applications, including both central and peripheral nerve interfaces. Recent developments have also witnessed the emergence of biodegradable and multifunctional devices. In this article, we aim to overview recent advances in implantable neuroelectronics with an emphasis on chronic biocompatibility, biodegradability, and multifunctionality. In addition to highlighting fundamental materials innovations, we also discuss important challenges and future opportunities. Graphical Abstract

AbstractGraphene-based materials have garnered tremendous interest as electromagnetic interference shields for various applications in healthcare, wireless communications and positioning systems, and space microelectronics. This is because they can circumvent the common drawbacks of metal-based shields, including weight and corrosion. In the present work, we report a ~30-nm highly transparent shield with 93% optical transmission that can attenuate the incident electromagnetic waves by ~94% in the X-band frequency range, offering an electromagnetic interference (EMI) shielding effectiveness of 13.3 dB at 8.2 GHz. The shield is designed in a layer-by-layer assembly, featuring two layers of the conductive sulfuric acid post-treated poly(3,4-ethylenedioxythiophene)poly(styrene sulfonate) (PEDOT:PSS) polymer sandwiching reduced graphene oxide (rGO) nanosheets in between. The assembled shield possesses a shielding to thickness figure-of-merit ratio of 400 dB µm–1, which is far superior to the reported values for graphene-based metal-free transparent shields. The multilayer rGO/PEDOT:PSS ultrathin film can be easily fabricated by a simple, cost-effective approach for various electrostatic discharge and EMI shielding applications.Impact statementOur work is the first study to introduce the viability of a highly transparent antistatic and electromagnetic interference (EMI) shield using reduced graphene oxide (rGO) as an interlayer within two nanolayers of poly(3,4-ethylenedioxythiophene)poly(styrene sulfonate)—an intrinsically conducting polymer also known as PEDOT:PSS. The developed 30-nm sandwich assembly resulted in an ultrathin film with high optical transparency of 93% that could attenuate 93.5% of the incident electromagnetic waves. The fabricated thin shield demonstrates a total EMI shielding effectiveness of 13.3 dB at 8.2 GHz in the X-band frequency range. This specific assembly design of rGO and PEDOT:PSS presented a thickness-specific shielding effectiveness of 400 dB µm–1, which is a record figure of merit compared with the reported values for previously “transparent” shields among “metal-free graphene-based” composites to date. To the best of our knowledge, no prior study has been reported on the “transparent” ESD/EMI shields based on the solution-processing of PEDOT:PSS and rGO.Graphical abstract

AbstractCommercial fusion power plants will require strong magnetic fields that can only be achieved using state-of-the-art high-temperature superconductors in the form of REBa2Cu3O7−δ-coated conductors. In operation in a fusion machine, the magnet windings will be exposed to fast neutrons that are known to adversely affect the superconducting properties of REBa2Cu3O7−δ compounds. However, very little is known about how these materials will perform when they are irradiated at cryogenic temperatures. Here, we use a bespoke in situ test rig to show that helium ion irradiation produces a similar degradation in properties regardless of temperature, but room-temperature annealing leads to substantial recovery in the properties of cold-irradiated samples. We also report the first attempt at measuring the superconducting properties while the ion beam is incident on the sample, showing that the current that the superconductor can sustain is reduced by a factor of three when the beam is on.Impact statementREBa2Cu3O7−δ high-temperature superconductors are an enabling technology for plasma confinement magnets in compact commercial fusion power plants, owing to their ability to carry very high current densities when processed as quasi-single crystals in the form of coated conductors. In service in a fusion device, the magnet windings will be exposed to a flux of fast neutrons that will induce structural damage that will adversely affect the superconducting performance, but very little data are currently available on the effect of irradiation at the cryogenic temperatures relevant for superconducting magnets. Moreover, even room-temperature annealing substantially affects superconducting properties after irradiation, so to obtain key technical data for fusion magnet designers, it is important to measure these properties in situ, under irradiation. This work shows that for the first time, it is important to consider how energetic particles directly influence superconductivity during irradiation because we observe a reduction in zero-resistance current by a factor of as much as three when an ion beam is incident on the sample. Although neutrons will not interact with the material in the same way as charged ions, primary knock-on ions from neutron damage are expected to have a similar effect to the He+ ions used in our study.Graphical abstract

In recent years, three-dimensional (3D) bioprinting has become an emerging technology to fabricate functional tissues and organs that could replicate native tissue function. Due to its ability to precisely position cellular materials and utilize medical images, 3D bioprinting has enormous potential in biomedical applications, including tissue engineering and regenerative medicine. Three-dimensional bioprinting is a rapidly progressing field that has demonstrated clinically relevant impactful uses. In this article, we provide an overview of important aspects of 3D bioprinting technologies, bioink design, and emerging bioprinting technologies in the field. We also feature five articles that focus on different aspects of 3D bioprinting included in this issue. These articles highlight 3D bioprinted tissue models, 3D bioprinting of organoid and organ-on-a-chip platforms, volumetric bioprinting for large-scale tissues and organs, and applications of 3D bioprinting in bone tissue engineering and otolaryngology.Graphical abstract

The family of two-dimensional (2D) transition-metal carbides, carbonitrides, and nitrides, known as MXenes, has grown from a single composition in 2011 to a ~50-composition family. With a large number of possible transition metals and their combinations, four possible 2D thickness ranges for a single 2D flake, tunable surface chemistry and the capability for hosting species between their 2D flakes, MXenes can be considered one of the most amendable families of materials in the 2D space. MXenes have a unique combination of properties complementary to other 2D materials, such as high electrical conductivity (up to 24,000 S/cm), high Young’s modulus (reaching ~380 GPa), combined with 2D flexibility, and tunable and hydrophilic surfaces. These set of properties as well as their simple and scalable synthesis qualified MXenes to be studied in a variety of different areas, including energy storage and conversion, electrocatalysis, sensing, electromagnetic interference shielding and wireless communications, structural materials, tribology, environmental remediation, and biomedical fields. This issue covers the various MXene synthesis routes and some of MXenes emerging areas in sensing, environmental, and biomedical applications. Additionally, the structure, stability, and properties of MXenes are discussed from the computational studies perspective. Graphical abstract

AbstractNanostructured materials with their remarkable properties are key enablers in many modern applications. For example, industrial dry-milling processes would not be as widely spread without the use of hard, wear-resistant metal nitride coatings to protect the cutting tools. However, improving these nanostructured thin films with regard to dynamical properties is demanding as probing respective parameters of (sub-)micron layers without any substrate influence is still challenging. To extend the scientific toolbox for such spatially confined systems, a novel methodological approach based on resonance peak measurements of a cantilever-transducer system termed micromechanical spectroscopy (µMS) is developed and applied to a Al0.8Cr0.2N model system. The mainly wurtzite type supersaturated Al0.8Cr0.2N system showed precipitation of cubic CrN at grain boundaries and local Cr variations upon annealing at 1050°C. This was accompanied by an increase in the previously unknown damping capability of 63 percent and an increase in Young’s modulus by 36 percent.Impact statementThere is a wide variety of applications for nano- to micrometer-sized thin films in today’s engineering technology, from thermal barrier- and wear-resistant coatings in turbines and bearings, over diffusion barriers and heatsinks in microelectronic devices, to optically active layers in lasers or mirrors. The mechanical properties of such thin films are oftentimes governed by their thermal history, leading to either intentional or undesired changes in the microstructure (e.g., the formation of precipitates). While the investigation of such features is usually constricted to static analysis using high-resolution techniques, such as transmission electron microscopy, understanding their impact on dynamic properties of the film remains a challenge. However, these are highly relevant in many engineering applications where cyclic behavior is common, such as high-speed dry milling. In the present work, we investigate the change in mechanical damping capability upon annealing of a 6-µm thin AlCrN film, commonly used in demanding dry-milling applications, using micromechanical spectroscopy (µMS) of cantilever-shaped specimens. After a carefully adjusted heat treatment, the film exhibits the formation of cubic CrN precipitates in an otherwise wurtzite AlCrN matrix, which leads to a previously unknown beneficial increase in damping capability of the film.Graphical abstract

AbstractThe seemingly contradictory state of research on short-range order in many-component alloys is addressed through a critical review of the characterization of face-centered-cubic 3d systems. Despite the paucity of direct observations, the ordering of many widely studied alloys is argued to be primarily interesting for its potential ubiquity. To clarify this situation, future research directions are proposed with reference to historical results, including a review of the fundamental principles of ordering and clustering.Graphical abstract