Applications of nanowires into future generation nanodevices require a complete understanding of the mechanical properties of the nanowires. A great research effort has been made in the past two decades to understand the deformation physics and mechanical behaviors of nanowires, and to interpret the discrepancies between experimental measurements and theoretical predictions. This review focused on the characterization and understanding of the mechanical properties of nanowires, including elasticity, plasticity, anelasticity and strength. As the results from the previous literature in this area appear inconsistent, a critical evaluation of the characterization techniques and methodologies were presented. In particular, the size effects of nanowires on the mechanical properties and their deformation mechanisms were discussed.

Emerging micro-scale medical devices are showing promise, whether in delivering drugs or extracting diagnostic biomarkers from skin. In progressing these devices through animal models towards clinical products, understanding the mechanical properties and skin tissue structure with which they interact will be important. Here, through measurement and analytical modelling, we advanced knowledge of these properties for commonly used laboratory animals and humans (~30 g to ~150 kg). We hypothesised that skin’s stiffness is a function of the thickness of its layers through allometric scaling, which could be estimated from knowing a species’ body mass. Results suggest that skin layer thicknesses are proportional to body mass with similar composition ratios, inter- and intra-species. Experimental trends showed elastic moduli increased with body mass, except for human skin. To interpret the relationship between species, we developed a simple analytical model for the bulk elastic moduli of skin, which correlated well with experimental data. Our model suggest that layer thicknesses may be a key driver of structural stiffness, as the skin layer constituents are physically and therefore mechanically similar between species. Our findings help advance the knowledge of mammalian skin mechanical properties, providing a route towards streamlined micro-device research and development onto clinical use.

Simple equations are proposed for determining elastic modulus and hardness properties of thin films on substrates from nanoindentation experiments. An empirical formulation relates the modulus E and hardness H of the film/substrate bilayer to corresponding material properties of the constituent materials via a power-law relation. Geometrical dependence of E and H is wholly contained in the power-law exponents, expressed here as sigmoidal functions of indenter penetration relative to film thickness. The formulation may be inverted to enable deconvolution of film properties from data on the film/substrate bilayers. Berkovich nanoindentation data for dense oxide and nitride films on silicon substrates are used to validate the equations and to demonstrate the film property deconvolution. Additional data for less dense nitride films are used to illustrate the extent to which film properties may depend on the method of fabrication.

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A number of arthropod taxa contain metals in their mandibles (jaws), such as zinc, manganese, iron, and calcium. The occurrence of zinc and its co-located halogen chlorine have been studied in relation to the mechanical properties and shown to be linked in a direct fashion with increasing concentration. Hardness along with elastic modulus (stiffness) has also been linked to zinc and halogen concentration in some marine polychaete worms. The metal appears to be incorporated within the biological matrix, possibly bonding with proteins. However, the comparative advantage of metal inclusion has not been tested. It is possible that without metals, alternative mechanisms are used to achieve hardness of equal value in similar 'tools' such as mandibles. This question has direct bearing on the significance of metal hardening. In the present article, we compare across mandibles from six termite species, including samples with major zinc concentration, minor manganese, and no metals. Nanoindentation, electron microscopy, and electron microanalysis are used to assess metal concentration, form, and mechanical properties. The data demonstrate that termite mandibles lacking metals when fully developed have lower values for hardness and elastic modulus. Zinc is linked to a relative 20% increase in hardness when compared with mandibles devoid of metals. The similar transition metal, manganese, found in minor concentrations, is not linked to any significant increase in these mechanical properties. This raises the question of the function of manganese, which is as commonly found in insect mandibles as zinc and often located in the same mandibles.