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The vanishing friction, known as superlubricity, is potentially a significant performance indicator in the development of nanostructured materials and has become increasingly important for realizing energy saving and extending the life of mechanical components. Herein, a systematic review of recent progress in nanomaterials for achieving the superlubric state is provided, beginning with a brief introduction of nanostructured materials in superlubricity and its wide potential applications. Subsequently, a detailed discussion of experimental and simulation works on the different spatial structures of nanomaterials associated with size effects ranging from 0D to 3D nanostructures is given, with an emphasis on solid and liquid superlubricity. Finally, this work concludes with perspectives on the challenges and future directions for developing nanomaterials in the field of superlubricity.

There has been tremendous interest in the development of different innovative wear‐resistant materials, which can help to reduce energy losses resulted from friction and wear by ≈40% over the next 10–15 years. This paper provides a comprehensive review of the recent progress on designs, properties, and applications of wear‐resistant materials, starting with an introduction of various advanced technologies for the fabrication of wear‐resistant materials and anti‐wear structures with their wear mechanisms. Typical strategies of surface engineering and matrix strengthening for the development of wear‐resistant materials are then analyzed, focusing on the development of coatings, surface texturing, surface hardening, architecture, and the exploration of matrix compositions, microstructures, and reinforcements. Afterward, the relationship between the wear resistance of a material and its intrinsic properties including hardness, stiffness, strength, and cyclic plasticity is discussed with underlying mechanisms, such as the lattice distortion effect, bonding strength effect, grain size effect, precipitation effect, grain boundary effect, dislocation or twinning effect. A wide range of fundamental applications, specifically in aerospace components, automobile parts, wind turbines, micro‐/nano‐electromechanical systems, atomic force microscopes, and biomedical devices are highlighted. This review is concluded with prospects on challenges and future directions in this critical field.

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Inspired by shape-morphing organisms in nature, researchers have developed various hydrogels with stimuli-responsive swelling, shrinking, bending, folding, origami, rolling, twisting, or locomotion. These smart hydrogels are usually created by patterning or 4D printing. The shape morphing of hydrogels allows the fabrication of helixing, twisting, and rolling microstructures, all of which are hard to reproduce directly by ordinary techniques. More importantly, under external stimuli (e.g., solvent, humidity, temperature, light, pH, and electric/magnetic fields), many hydrogels exhibit recoverable shape morphing and thus find promising applications in grippers, sensors, valves, soft robotics, etc. Since shape morphing determines the functions of hydrogels in a great number of cases, herein, recent advances of stimuli-responsive hydrogels are summarized, with their types, shape-morphing mechanisms, fabrication methods, shape-morphing modes, and extensive applications covered. The conclusion and perspectives are also presented to guide the design and fabrication of functional hydrogels.

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