Two-dimensional (2D) transition metal nitrides and carbides (MXenes), represented by Ti₃C₂T_x, have broad applications in flexible electronics, electromechanical devices, and structural membranes due to their unique physical and chemical properties. Despite the Young’s modulus of 2D Ti₃C₂T_x has been theoretically predicted to be 0.502 TPa, which has not been experimentally confirmed so far due to the measurement is extremely restricted. Here, by optimizing the sample preparation, cutting, and transfer protocols, we perform the direct in-situ tensile tests on monolayer Ti₃C₂T_x nanosheets using nanomechanical push-to-pull equipment under a scanning electron microscope. The effective Young’s modulus is 0.484 ± 0.013 TPa, which is much closer to the theoretical value of 0.502 TPa than the previously reported 0.33 TPa by the disputed nanoindentation method, and the measured elastic stiffness is ~948 N/m. Moreover, during the process of tensile loading, the monolayer Ti₃C₂T_x shows an average elastic strain of ~3.2% and a tensile strength as large as ~15.4 GPa. This work corrects the previous reports by nanoindentation method and demonstrates that the Ti₃C₂T_x indeed keeps immense potential for broad range of applications.

Nanocomposite based wearable strain sensors hold promise for a variety of applications from human body motion detection to soft robotics. However, improving the sensitivity of strain sensors while keeping their stretchability (i.e., strain detection range) is still a grand challenge in this area. In this research, a highly efficient and scalable method was developed to enhance the sensitivity of a strain sensor based on carbon nanotube/polydimethylsiloxane (CNT/PDMS) nanocomposites. Through the introduction of porosity into the nanocomposites to form CNT/PDMS sponges using citric acid monohydrate particles, the sensitivity (GF = 15, strain (ε) > 15%; GF = 1.1, ε < 15%) is improved compared to the CNT/PDMS nanocomposites without a porous structure (GF = 3.2, ε > 10%; GF = 0.12, ε < 10%). The strain sensor based on the CNT/PDMS sponge not only shows the capability of monitoring human body motion, such as bending of a finger and elbow, speaking, drinking, and breathing, but also demonstrates potential applications in soft robotics, such as detection of the actuation of a dielectric elastomer.

Traditional design, manufacturing and maintenance are run and managed independently under their own rules and regulations in an increasingly time-and-cost ineffective manner. A unified platform for efficient and intelligent design-manufacturing-maintenance of mechanical equipment and systems is highly needed in this rapidly digitized world. In this work, the definition of digital twin and its research progress and associated challenges in the design, manufacturing and maintenance of engineering components and equipment were thoroughly reviewed. It is indicated that digital twin concept and associated technology provide a feasible solution for the integration of design-manufacturing-maintenance as it has behaved in the entire lifecycle of products. For this aim, a framework for information-physical combination, in which a more accurate design, a defect-free manufacturing, a more intelligent maintenance, and a more advanced sensing technology, is prospected.

As the key half reaction of water-splitting electrolysis, the hydrogen evolution reaction (HER) that occurs at the cathode directly determines the overall efficiency of hydrogen production. To improve the efficiency of electrochemical water splitting for hydrogen generation, efficient and robust catalysts need to be developed. Strain engineering, which represents an effective and promising category of strategies, can regulate the electronic structures of catalysts by modulating the lattice strain and ultimately optimizing the HER dynamics. This work critically reviews the recent progress of strain engineering in HER and provides future perspectives for this area. The methods and characterization techniques are also introduced in detail. Hopefully this review can provide guidelines for the design and manufacturing of advanced catalysts for HER and other heterogeneous catalysis reactions such as chemical sensing, CO₂ reduction and NH₃ synthesis.