The special mechanical properties of nanoparticles allow for novel applications in many fields, e.g., surface engineering, tribology and nanomanufacturing/nanofabrication. In this review, the basic physics of the relevant interfacial forces to nanoparticles and the main measuring techniques are briefly introduced first. Then, the theories and important results of the mechanical properties between nanoparticles or the nanoparticles acting on a surface, e.g., hardness, elastic modulus, adhesion and friction, as well as movement laws are surveyed. Afterwards, several of the main applications of nanoparticles as a result of their special mechanical properties, including lubricant additives, nanoparticles in nanomanufacturing and nanoparticle reinforced composite coating, are introduced. A brief summary and the future outlook are also given in the final part.

The use of reactive electropositive metal contacts is proposed to lower contact resistance in MoS₂ devices, based on calculations of the sulfur vacancy in MoS₂ by the screened exchange (sX) hybrid functional. sX gives band gaps of 1.88 eV and 1.34 eV for monolayer and bulk MoS₂. The S vacancy has a formation energy of 2.35 eV in S-rich conditions, while the Mo vacancy has a large formation energy of 8.02 eV in Mo-rich conditions. The S vacancy introduces defect levels 0/−1 at 1.23 eV and −1/−2 at 1.28 eV in the upper gap. Its formation energy becomes small or negative for E_F near the conduction band edge, leading to E_F pinning near the conduction band for reactive metal contacts and lower contact resistances.

Superlubricity of graphite and graphene has aroused increasing interest in recent years. Yet how to obtain a long-lasting superlubricity between graphene layers, under high applied normal load in ambient atmosphere still remains a challenge but is highly desirable. Here, we report a direct measurement of sliding friction between graphene and graphene, and graphene and hexagonal boron nitride (h-BN) under high contact pressures by employing graphene-coated microsphere (GMS) probe prepared by metal-catalyst-free chemical vapour deposition. The exceptionally low and robust friction coefficient of 0.003 is accomplished under local asperity contact pressure up to 1 GPa, at arbitrary relative surface rotation angles, which is insensitive to relative humidity up to 51% RH. This ultralow friction is attributed to the sustainable overall incommensurability due to the multi-asperity contact covered with randomly oriented graphene nanograins. This realization of microscale superlubricity can be extended to the sliding between a variety of two-dimensional (2D) layers.

In modern electric equipment, especially electric vehicles, inverter control systems can lead to complex shaft voltages and bearing currents. Within an electric motor, many parts have electrical failure problems, and among which bearings are the most sensitive and vulnerable components. In recent years, electrical failures in bearing have been frequently reported in electric vehicles, and the electrical failure of bearings has become a key issue that restricts the lifetime of all-electric motor-based power systems in a broader sense. The purpose of this review is to provide a comprehensive overview of the bearing premature failure in the mechanical systems exposed in an electrical environment represented by electric vehicles. The electrical environments in which bearing works including the different components and the origins of the shaft voltages and bearing currents, as well as the typical modes of electrical bearing failure including various topographical damages and lubrication failures, have been discussed. The fundamental influence mechanisms of voltage/current on the friction/lubrication properties have been summarized and analyzed, and corresponding countermeasures have been proposed. Finally, a brief introduction to the key technical flaws in the current researches will be made and the future outlook of frontier directions will be discussed.

Marangoni effect has been observed in many liquids, but its existence in pure water is still a debated problem. In the present work, the Marangoni flow in evaporating water droplets has been observed by using fluorescent nanoparticles. Flow patterns indicate that a stagnation point where the surface flow, the surface tension gradient, and the surface temperature gradient change their directions exists at the droplet surface. The deduced nonmonotonic variation of the droplet surface temperature, which is different from that in some previous works, is explained by a heat transfer model considering the adsorbed thin film of the evaporating liquid droplet.