X‐rays are a penetrating form of high‐energy electromagnetic radiation with wavelengths ranging from 10 pm to 10 nm. Similar to visible light, X‐rays provide a powerful tool to study the atoms and elemental information of objects. Different characterization methods based on X‐rays are established, such as X‐ray diffraction, small‐ and wide‐angle X‐ray scattering, and X‐ray‐based spectroscopies, to explore the structural and elemental information of varied materials including low‐dimensional nanomaterials. This review summarizes the recent progress of using X‐ray related characterization methods in MXenes, a new family of 2D nanomaterials. These methods provide key information on the nanomaterials, covering synthesis, elemental composition, and the assembly of MXene sheets and their composites. Additionally, new characterization methods are proposed as future research directions in the outlook section to enhance understanding of MXene surface and chemical properties. This review is expected to provide a guideline for characterization method selection and aid in precise interpretation of the experimental data in MXene research.

Conductive fibers are needed for the development of flexible electronic and biomedical devices. MXene fibers show great promise for use in such applications because of their high conductivity. Current literature on MXene fiber development highlights the need for improving their mechanical properties and investigation of biocompatibility. Here the use of silk fibroin biopolymer as a MXene formulation additive for the production of MXene fibers is studied. It is found that the favorable silk fibroin–MXene interactions resulted in improved durability, withstanding up to 1 h of high frequency sonication in buffered solutions. Furthermore, fibers with ≈5 wt% silk fibroin displays interesting properties including high conductivity (≈3700 S cm⁻¹), high volumetric capacitance (≈910 F cm⁻³), and non‐cytotoxicity toward THP‐1 monocytic cells. The results presented here provide an important insight into potential use of MXene fibers in flexible electronics and biomedical applications.

Ti ₃ C ₂ T _x MXene is a promising active material for developing fiber-based devices due to its exceptional electrical conductivity and electrochemical capacitance. However, fabricating robust fibers with high MXene content remains challenging due to shortcomings such as low interfacial adhesion between sheets and shrinkage-induced sheet disorientation during processing, leading to diminished physical and electrochemical properties. Here, we demonstrate the fabrication of tough, conductive, and electrochemically active fibers through a sequential bridging strategy involving calcium cation (Ca ²⁺ ) infiltration of cellulose nanocrystal (CNC)-bridged MXene, cross-linked and dried under tension. The resulting fibers exhibited a record toughness of ∼2.05 MJ m ⁻³ and retained high volumetric capacitance (∼985 F cm ⁻³ ), attributed to the synergistic CNC bridging, Ca ²⁺ cross-linking, and tension application during fiber drying. These fibers also surpass the conductivity of their unaligned pristine MXene counterpart (∼8347 S cm ⁻¹ vs ∼5078 S cm ⁻¹ ), ascribed to the tension-induced improvement in MXene alignment within these fibers, mitigating the undesirable effects of inserting an insulating CNC bridge. We anticipate that improving the toughness and conductivity of sequentially bridged MXene fibers will pave the way for the production of robust multifunctional MXene fibers, allowing their use in practical high-performance applications like wearable electronics and energy storage devices.

Wearable electronic sensors have recently attracted tremendous attention in applications such as personal health monitoring, human movement detection, and sensory skins as they offer a promising alternative to counterparts made from traditional metallic conductors and bulky metallic conductors. However, the real-world use of most wearable sensors is often hindered by their limited stretchability and sensitivity, and ultimately, their difficulty to integrate into textiles. To overcome these limitations, wearable sensors can incorporate flexible conductive fibers as electrically active components. In this study, we adopt a scalable wet-spinning approach to directly produce flexible and conductive fibers from aqueous mixtures of Ti₃C₂T_x MXene and natural rubber (NR). The electrical conductivity and stretchability of these fibers were tuned by varying their MXene loading, enabling knittability into textiles for wearable sensors. As individual filaments, these MXene/NR fibers exhibit suitable conductivity dependence on strain variations, making them ideal for motivating sensors. Meanwhile, textiles from knitted MXene/NR fibers demonstrate great stability as capacitive touch sensors. Collectively, we believe that these elastic and conductive MXene/NR-based fibers and textiles are promising candidates for wearable sensors and smart textiles.

In article number 1804732, Shayan Seyedin, Joselito M. Razal, and co‐workers make a class of flexible and highly conductive fibers from MXene and PEDOT:PSS that when fabricated into elastic energy storing devices demonstrate high performance even when stretched multiple times. This work provides a promising energy storage solution for powering miniaturized or wearable electronics.

Ti₃C₂T_x MXene (or “MXene” for simplicity) has gained noteworthy attention for its metal‐like electrical conductivity and high electrochemical capacitance—a unique blend of properties attractive toward a wide range of applications such as energy storage, healthcare monitoring, and electromagnetic interference shielding. However, processing MXene architectures using conventional methods often deals with the presence of defects, voids, and isotropic flake arrangements, resulting in a trade‐off in properties. Here, a sequential bridging (SB) strategy is reported to fabricate dense, freestanding MXene films of interconnected flakes with minimal defects, significantly enhancing its mechanical properties, specifically tensile strength (≈285 MPa) and breaking energy (≈16.1 MJ m^–3), while retaining substantial values of electrical conductivity (≈3050 S cm^–1) and electrochemical capacitance (≈920 F cm^–3). This SB method first involves forming a cellulose nanocrystal‐stitched MXene framework, followed by infiltration with structure‐densifying calcium cations (Ca²⁺), resulting in tough and fatigue resistant films with anisotropic, evenly spaced, and strongly interconnected flakes — properties essential for developing high‐performance energy‐storage devices. It is anticipated that the knowledge gained in this work will be extended toward improving the robustness and retaining the electronic properties of 2D nanomaterial‐based macroarchitectures.