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The rapid development of two-dimensional (2D) materials has significantly broadened the scope of 2D science in both fundamental scientific interests and emerging technological applications, wherein the mechanical properties play an indispensably key role. Nevertheless, particularly challenging is the ultrathin nature of 2D materials that makes their manipulations and characterizations considerably difficult. Herein, thanks to the excellent flexibility of vanadium disulfide (VS2) sheets, their susceptibility to out-of-plane deformation is exploited to realize the controllable loading and enable the accurate measurements of mechanical properties. In particular, the Young's modulus is estimated to be 44.4 ± 3.5 GPa, approaching the lower limit for 2D transition metal dichalcogenides (TMDs). We further report the first measurement of thickness-dependent bending rigidity of VS2, which deviates from the prediction of the classical continuum mechanics theory. Additionally, a deeper understanding of the mechanics within two dimensions also facilitates the modulation of strain-coupled physics at the nanoscale. Our Raman measurements showed the Gruneisen parameters for VS2 were determined for the first time to be γE2g1 ≈ 0.83 and γA1g ≈ 0.32.

Multilayer graphene exhibits strong mechanical anisotropy in the nonlinear elastic regime, and tuning this mechanical anisotropy without damaging the graphene is a tough challenge. In this work, we propose an efficient strategy to tune the mechanical anisotropy of multilayer graphene via interlayer twist. The orientation-dependent strain–stress curve of monolayer graphene is described in analytical form, which is further generalized for predicting the mechanical anisotropy of twisted multilayer graphene by introducing a twist-induced “phase shift.” These predictions are supported by atomistic simulations. It is found that the strong nonlinear mechanical anisotropy of multilayer graphene can be effectively tuned and even eliminated via the twist-induced phase shift. These findings are finally generalized for other layered crystals.

Phosphorene, a two-dimensional material that can be exfoliated from black phosphorus, exhibits remarkable mechanical, thermal, electronic, and optical properties. In this work, we demonstrate that the unique structure of pristine phosphorene endows this material with exceptional quantum-mechanical performance by using first-principles calculations. Upon charge injection, the maximum actuation stress is 7.0 GPa, corresponding to the maximum actuation strain as high as 36.6% that is over seven times larger than that of graphene (4.7%) and comparable with natural muscle (20–40%). Meanwhile, the maximum volumetric work density of phosphorene (207.7 J/cm3) is about three orders of magnitude larger than natural muscle (0.008–0.04 J/cm3) and approximately six times larger than graphene (35.3 J/cm3). The underlying mechanism of this exceptional electromechanical performance in phosphorene is well revealed from the analysis of atomic structure and electronic structure. Finally, the influence of charge on the mechanical behaviors of phosphorene is examined by mechanical tests, indicating the sufficient structural integrity of phosphorene under the combined electromechanical loading. These findings shed light on phosphorene for promising applications in developing nanoelectromechanical actuators.

Graphene possesses extraordinary mechanical, electronic, and thermal properties, thus making it one of the most promising building blocks for constructing macroscopic high performance and multifunctional materials. However, the common material strength–ductility paradox also appears in the carbon-nanoarchitected materials and some of the key mechanical performance, for example, the tensile strength of graphene-based materials, are still far lower than that of graphene. Inspired by the exceptional mechanical performance of silk protein benefiting from the conformations of folded structures as well as their transitions, this work proposed a topological strategy to yield graphene-based materials with ultrahigh ductility while maintaining decent tensile strength by self-folding graphene sheets. This drastically improved mechanical performance of graphene-based materials is attributed to the exploitation of shearing, sliding, and unfolding deformation at the self-folded interface. Molecular dynamics simulations show that both modulating self-folded length and engineering interface interaction can effectively control the strength, ductility, and the ductile failure of van der Waals interfaces among the self-folded structures, where interfacial shearing, sliding, and unfolding open channels to dissipate mechanical energy. Based on the insights into the atomic-scale deformation by molecular dynamics simulations, the underlying mechanism of deformation and failure of these materials is finally discussed with a continuum mechanics-based model. Our findings bring perceptive insights into the microstructure design of strong-yet-ductile materials for load-bearing engineering applications.

The fabrication of nanotips has been driven by the increasing industrial demands in developing high-performance multifunctional nanodevices. In this work, we proposed a controlled, rapid as well as low cost nanomolding-necking technology to fabricate gold nanotips arrays. The geometries of gold nanotips having cone angle range of ∼28-77° and curvature radii of