Mrs Bulletin最新文献

Over the past three decades, nanoindentation has continuously evolved and transformed the field of materials mechanical testing. Once highlighted by the groundbreaking Oliver-Pharr method, the utility of nanoindentation has transcended far beyond modulus and hardness measurements. Today, with increasing challenges in developing advanced energy generation and electronics technologies, we face a growing demand for accelerated materials discovery and efficient assessment of mechanical properties that are coupled with modern machine learning-assisted approaches, most of which require robust experimental validation and verification. To this end, nanoindentation finds its unique strength, owing to its small-volume requirement, of fast-probing and providing a mechanistic understanding of various materials. As such, this technique meets the demand for rapid materials assessment, including semiconductors, ceramics, and thin films, which are integral to next-generation energy-efficient and high-power electronic devices. Here, we highlight modern nanoindentation strategies using novel experimental protocols outlined by the use of nanoindentation for characterizing functional structures, dislocation engineering, high-speed nanoindentation mapping, and accelerating materials discovery via thin-film libraries. We demonstrate that nanoindentation can be a powerful tool for probing the fundamental mechanisms of elasticity, plasticity, and fracture over a wide range of microstructures, offering versatile opportunities for the development and transition of functional materials.

Graphical abstract: Modern strategies for nanoindentation in electronic systems, functional ceramics, heterogeneous structures, and thin films.

Nanoindentation is crucial in materials science for assessing mechanical properties in submicrometer volumes, and high-speed nanoindentation mapping has evolved it from a localized measurement technique into a scanning-probe-like approach for microstructures, delivering large-area, high-resolution mechanical property maps with more than 200,000 indents in hours. Such mapping enables direct imaging of hardness and modulus variations, phase boundaries, and local deformation behaviors in materials where heterogeneity governs mechanical performance. By correlating these mechanical maps with composition, orientation, and phase data from complementary analytical techniques, deep multidimensional data sets reveal the complex interplay between structure, processing, and properties. Such data sets increasingly demand advanced statistical clustering, machine learning, and deep learning for classification, trend extraction, and phase identification. Moving forward, high-speed nanoindentation is anticipated to operate under operando conditions and advanced mechanical modalities, offering new insights into interfacial deformation, anisotropic behavior, and the broader challenges of materials design and performance.

Graphical abstract: Schematic representation of high-speed nanoindentation mapping revealing microstructural heterogeneities in mechanical response. The indenter tip rapidly probes the surface, generating property maps sensitive to features such as twinning, recrystallization, segregation, precipitates, and sintered phases. These mechanical maps can be directly correlated with crystallographic and phase information from Electron Backscatter Diffraction (EBSD) and elemental composition from Energy-Dispersive X-ray Spectroscopy (EDS). Measurements can be performed operando, i.e., under real-time and service-relevant environmental conditions (e.g., temperature, atmosphere), enabling direct analysis of structure-property-performance relationships at the microstructural scale.

A triboelectric nanogenerator (TENG) is a novel device that utilizes contact electrification and electrostatic induction to convert mechanical energy into electrical energy. Its characteristics include high energy density and flexibility, enabling self-powering of electronic devices by harvesting mechanical energy from the environment. Its applications include biomedical devices, wearable electronics, and Internet-of-Things (IoT) sensors. Despite these advantages, extracting electrical energy from TENG remains challenging due to its time-varying nature and low internal capacitance. Effective power-management techniques are essential for TENG energy-harvesting systems, yet research on dedicated integrated power-conversion methods is currently limited. Given the growing interest in TENG, a comprehensive exploration of energy-harvesting systems is critically necessary. This article synthesizes and compares current advancements in triboelectric energy-harvesting systems, emphasizing strategies to enhance output power through various power-conversion techniques. Additionally, it explores techniques employed in other energy-harvesting systems to inspire innovative approaches in TENG system design.

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Abstract: The power-conversion efficiency (PCE) of perovskite solar cells (PSCs) has exceeded in 2024 the theoretical single-junction Shockley-Queisser limit of 33.7% with the perovskite/silicon tandem version. The commercialization of the technology is now a reality with the PV industry demonstrating its first commercial products. Many companies have shown excellent module reliability with most of them passing the IEC standardization (required for commercial silicon solar cells). In this article, we want to bring some light on the most intriguing question regarding the stability and reliability of PSC technology: Are we there yet? Issues on stability are still under strong investigation and research on the topic has increased exponentially in the last 10 years. Since some companies have already promised excellent reliability of their modules, with 80% retention of the initial PCE after 25 years, the following  two or three years will be crucial to demonstrate these pledges. In this work, we present an outline of the most stable PSC devices reported to date and discuss the most important strategies leading to highly stable devices.

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Supplementary information: The online version contains supplementary material available at 10.1557/s43577-025-00863-5.

Thermoelectric technology has emerged as a promising solution for direct heat-to-electricity conversion and solid-state cooling, offering great energy efficiency and environmental impact advantages. However, conventional systems predominantly rely on tellurium-based materials, which are limited by scarcity, high cost, and environmental concerns. This article focuses on tellurium-free thermoelectric modules, with an emphasis on magnesium-based alternatives, including p-type MgAgSb and n-type Mg₃(Sb, Bi)₂, which demonstrate competitive performance at operating temperatures below 300℃. By exploring recent advances in material synthesis, module fabrication, and interface engineering, we highlight the potential of these sustainable materials to achieve high thermoelectric figures of merit while reducing environmental impact. Additionally, the article assesses the performance metrics and durability of these modules and discusses emerging applications in energy harvesting, medical devices, consumer electronics, and more. Finally, we outline future research directions aimed at overcoming remaining challenges, including long-term stability and scalable manufacturing, to pave the way for the widespread adoption of tellurium-free thermoelectric technology.

Graphical abstract: Potential application scenarios of Mg-based Te-free thermoelectric technology.

Abstract: For the past 30 years, nanoindentation has provided critical insights into the microstructure-strength relationship for a wide range of materials. However, it has traditionally been limited to quasistatic testing at room temperature, which has hindered a holistic understanding of microstructurally induced deformation mechanisms and their dynamic evolution as a function of the temperature and strain rate. Over the past decade, the operational scope of nanoindentation has expanded dramatically. Temperatures up to 1100°C and strain rates as high as 10⁺⁴ s^-1 and as low as 10^-8 s^-1 have become accessible. In addition, advanced techniques allow tracking microstructural evolution and corresponding changes in mechanical behavior during deformation under extreme conditions. These advancements have transformed nanoindentation into a versatile tool for comprehensive materials characterization, enabling high-throughput investigations under multimodal conditions.

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Abstract: Filamentous cyanobacteria originate toxic harmful algal blooms (HABs) in aquatic ecosystems, severely impacting freshwater ecosystems and life. Despite being natural bloomers, these microorganisms are challenging to handle in vitro, due to the formation of aggregates with entangled filaments. Consequently, their precise growth dynamics, although vital to timely predict HABs, remains inaccessible. Here, we precisely assessed growth of the HAB forming cyanobacteria Oscillatoria nigroviridis, by cultivating filament suspensions in transparent, gas permeable, and portable fluoropolymer microcapillary strips. Direct optical observation of O. nigroviridis growth revealed shorter filaments comprising less than 50 cells grew at a slower rate, dN/dt = 0.09 cell/day compared to filaments comprising more than 50 cells, with dN/dt up to 0.47 cell/day. The fourfold increase in dN/dt is suggested as part of the blooming strategy of the microorganism. This work suggests that fluoropolymer microcapillary strips can be used for effortless sampling and high-resolution monitoring of HABs.

Impact statement: Climate change is increasing the occurrence of episodes of harmful algal bloom, where uncontrolled growth of noxious cyanobacteria such as Oscillatoria species has detrimental outcomes in both the environment and biomass production industry, consequently, impairing human and animal health due to the production of toxic or bioactive compounds. In particular, the study of growth dynamics of Oscillatoria species has been limited to unprecise methods due to complications with aliquoting filamentous biomass. Fluoropolymer microcapillary strips provide an ideal miniaturized platform for sampling, cultivation, and growth monitoring of O. nigroviridis strain UHCC 0327, which paves the way to foster better water quality management tools.

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Supplementary information: The online version contains supplementary material available at 10.1557/s43577-024-00813-7.

We report on a 23-year-old man who presented with bilateral subclinical keratoconus and juvenile glaucoma (JG). With intraocular pressures (IOPs) of 30 and 28 mmHg, both eyes were consecutively operated by adjusted trabeculotomy, leading to a remarkable decrease in IOP to well below the mean for this surgery in JG. Meanwhile, most keratoconus indices clearly progressed in the first 5 months postoperatively, with increases in corneal hysteresis, associated with a remarkable drop in the corneal resistance factor. During the following years, IOP remained low, and all changes (except the increase in corneal hysteresis) reverted to near preoperative levels through the follow-up course of 5 years. This report complements a few existing reports that show the coincidence of keratoconus and JG, and, more importantly, documents a novel pattern of remarkable and prolonged corneal changes following surgical lowering of IOP in eyes with these changes. Postoperative biomechanical disturbances in the cornea and possibly limbus are proposed in cases of JG and subclinical keratoconus.

The natural world contains a diverse range of solutions that allows for living organisms to dynamically adapt their structure and mechanical properties to meet environmental demands. For example, coral reef is able to accumulate reinforcing calcium carbonate from wave agitation and water current that stabilizes gaps in the structure and increases the reef density and strength through diagenetic reef cementation. Bone responds to repeated stress by translating deformations and fluid movement in the bone matrix into cellular signals that trigger bone formation through mechanotransduction. Utilizing these mechanisms as inspiration, synthetic materials have been developed that utilize stress-generated piezoelectric charges to attract mineral ions to form reinforcing mineral layers that can repair defects and damage over time and extend material lifetime. In this article, we examine natural adaptive processes that give inspiration for new synthetic materials with similar dynamic adaptive properties. We also introduce the capabilities of existing bioinspired synthetic materials, current challenges these systems face, potential application areas of this technology, and future research opportunities of these adaptive materials.

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Metallic materials, predominantly steels, are the most common structural materials in the various components along the hydrogen supply chain. Ensuring their sustainable and safe use in hydrogen technologies is a key factor in the ramp-up of the hydrogen economy. This requires extensive materials qualification, however, most of the accepted; and standardized test methods for determining the influence of gaseous hydrogen on metallic materials describe complex and costly procedures that are only available to a very limited extent worldwide. The hollow specimen technique is a simple, rapid, and economical method designed to overcome the limitations of the current methods for the qualification of metallic materials under high-pressure hydrogen gas. However, this technique is not yet standardized. The TransHyDE-H2Hohlzug project is presented in this article, along with the main steps required to optimize the hollow specimen technique. This includes closing knowledge gaps related to the specimen geometry, surface quality, and gas purity in dedicated working packages, thus contributing to a comprehensive standardization of the technique for tests in high-pressure hydrogen gas.

Impact statement

The hydrogen economy is considered a key solution for achieving climate neutrality in Europe, as it plays a crucial role in the decarbonization of sectors such as transport, industry, power, etc. Ensuring the safety and reliability of infrastructure is crucial for the ramp-up of the hydrogen economy. Therefore, it is necessary to meticulously study the materials and components used for infrastructure under conditions that closely resemble in-service conditions. The currently standardized methods are limited as they do not precisely replicate in-service conditions, and when they do, they are often complex, costly, and not easily accessible. This article presents the hollow specimen technique, a simple, and economical method developed to address the limitations of current standardized methods. The results from this work will contribute to the standardization of this technique for tests in high-pressure hydrogen gas. This will enable a faster evaluation of materials for hydrogen applications by industry and academia, thereby contributing to the growth of the hydrogen economy.

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