Volume 10 Issue 1, January 2011

The friction and wear of materials is part of our everyday experience, and yet these processes are not well understood. The example of diamond highlights wear processes that result from bumping atoms, showing that the devil is indeed in the details.

Empty liquids and equilibrium gels have so far been only theoretical possibilities, predicted for colloids with patchy interactions. But evidence of both has now been found in Laponite, a widely studied clay.

The practical use of electronic ratchets has long been hampered by low output powers and cryogenic operating temperatures. A pentacene-based organic ratchet can now drive electronic circuitry at room temperature.

A suitably chosen thin layer inserted between a ferromagnetic electrode and an organic semiconductor allows control over the polarization of the injected spins.

High annealing temperatures have limited the technological potential of solution-processed metal oxide semiconductors. It is now shown that high-quality films can be formed below 250 °C using precursors that are hydrolysed on-chip.

The first diffraction patterns from the individual atomic packing clusters in a metallic glass finally enable the direct study of local order in amorphous alloys.

Atomic force microscopy experiments on individual blood platelets reveal their dynamic contractile response to varied stiffness of the substrate.

In chemistry, some dynamic bonds can be selectively and reversibly broken and reformed in response to an environmental stimulus. This Review article discusses the incorporation of dynamic bonds, or interactions, in polymeric materials and the structural changes and macroscopic responses observed in the presence of different stimuli.

The atomic configuration of metallic glasses is a long-standing issue important to the understanding of their properties. Nanobeam electron diffraction experiments now enable a direct determination of the local atomic order in a metallic glass.

The only way diamond can be polished is by pressing it against small diamond crystals, but this works well only for certain crystallographic orientations. The details of this wear mechanism have now been uncovered in simulations that suggest wear occurs via a thin amorphous layer on the diamond surface.

The chemical versatility of organic semiconductors promises to be of great use to electronics and spintronics. As an example, it is now demonstrated that the spin polarization of extracted carriers from an organic semiconductor device can be controlled by the insertion of a thin layer of polar material. This approach opens up ideas for future spintronic device concepts.

A low-temperature, solution-based preparation of amorphous, metal oxide semiconducting thin-films is reported. This ‘sol–gel on chip’ hydrolysis approach yields thin-film transistors with high field-effect mobilities, reproducible and stable turn-on voltages and high operational stability.

Ratchet systems can extract work from non-equilibrium processes. Yet present electronic ratchets only operate at cryogenic temperatures and generate low currents, which are clear limitations for their practical use. Now, organic electronic ratchets providing enough power to drive simple logic circuits at room temperature have been realized.

Theoretical models of colloids with directional and anisotropic interactions have predicted the existence of both liquids with vanishing density, and arrested networks at equilibrium — that is, not undergoing phase separation. Experimental evidence of empty liquids and equilibrium gels is now provided for Laponite, a synthetic clay. These observations further our understanding of anisotropic interactions in colloidal suspensions.

Blood platelets aggregate to form clots that prevent haemorrhage. Knowledge of single-platelet mechanics is scarce, however. Atomic force microscopy experiments now show that platelets contract rapidly on contact with fibrinogen, and adhere strongly to multiple fibrin polymers, enhancing the elasticity of clots. These findings are relevant to disorders of platelet function, such as thrombosis.

A one-step preparation method of electrospun, synthetic scaffolds with controlled surface chemistry and functionality is reported. On addition of amphiphilic macromolecules, non-specific protein adsorption on the fibres’ surfaces is reduced, and by the further covalent attachment of certain peptide sequences to the fibres, specific bioactivation of the scaffold is achieved.

Sodium layered oxides are low-dimensional and strongly correlated systems that have been extensively studied because of their intriguing structural and physical properties. Electrochemical sodium intercalation is now used to investigate their different phase domains and thermal stability.

Andre Geim and Kostya Novoselov were awarded the 2010 Nobel Prize in Physics "for groundbreaking experiments regarding the two-dimensional material graphene". To celebrate the event, in this web focus we have gathered some of the most prominent papers on this one-atom-thick layer of graphite that Nature Materialshas published in the past four years.