Reviews & Analysis

Poisson's ratio describes the resistance of a material to distort under mechanical load rather than to alter in volume. On the bicentenary of the publication of Poisson's Traité de Mécanique, the continuing relevance of Poisson's ratio in the understanding of modern materials is reviewed.

Crystalline ice surfaces are found to exhibit an unusually large spread of vacancy formation energies, akin to an amorphous material. The finding has implications for the fundamental understanding of electrostatically frustrated surfaces and for the reactivity and catalytic properties of atmospheric ice.

The electronic structure in the bulk of a crystal can be unveiled by hard X-ray angle-resolved photoemission spectroscopy.

X-ray illumination can be used to control the arrangement of oxygen atoms in cuprate superconductors, allowing the writing of regions of robust high-transition-temperature superconductivity.

Mimicking the complexity of the extracellular environment in synthetic hydrogels is hard. A simple two-photon excitation strategy to simultaneously immobilize multiple proteins with spatial control in three dimensions shows promise.

The solvent-based electrolytes used at present in lithium-ion batteries can be unsafe for large-scale applications. A crystalline electrolyte with high ionic conductivity could soon enable all-solid energy storage systems.

Versatile room-temperature control of spin currents without a net charge flow paves the way for new methods to transfer and process information.

Single-walled carbon nanotubes have been used as test tubes for chemical reactions in an electron microscope. It is now shown that they can also act as reactors for the synthesis of narrow, helically twisted graphene nanoribbons through electron irradiation of functionalized fullerenes.

The coarsening mechanism, by which larger droplets in a solid-state matrix consume smaller ones, can effectively be reversed in the case of core–shell precipitates, leading to a nearly monodisperse droplet size distribution.

The design of structures of organic nanoporous crystals has been hampered by the difficulty of placing functional moieties in a predictive manner. A modular strategy based on prefabricated organic nanocages having directional chiral interactions that self-assemble into the predicted crystals circumvents this problem.

A single nanodevice that detects the presence of a single molecule would perhaps be the ultimate sensor. The demonstration of hydrogen sensing based on a single gold nanoaerial brings that possibility nearer.

Living cells regulate their area through active mechanisms, which often lead to the fusion and fission of lipid vesicles. It is now found that bilayers adhered to elastic substrates can also adjust their area passively, in response to applied lateral strains.

A new design for elastic metamaterials that can behave either as liquids or solids over a limited frequency range may enable new applications based on the control of acoustic, elastic and seismic waves.

Stem cells that are cultured in the laboratory differentiate in response to the mechanical properties of the substrate and its topography. It is now shown that mesenchymal stem cell multipotency is prolonged when the cells are cultured on a surface patterned with an ordered arrangement of nanoscale pits.

The thermal properties of nanostructures have become a fundamental topic owing to the necessity of heat removal in increasingly smaller electronic devices. Carbon allotropes present a range of intriguing thermal features, with the thermal conductivity spanning five orders of magnitude at room temperature. The topic is reviewed here with particular emphasis on graphene, which exhibits the highest thermal conductivity observed.

The main challenges to face before graphene can become part of realistic applications were discussed at a recent dedicated meeting.