The construction of tissue-engineering scaffolds that mimic cardiac anisotropy is a challenge. Now, accordion-like honeycomb scaffolds have been created that can form tissue grafts with preferentially aligned heart cells, and with mechanical properties that closely resemble the anisotropy of native myocardium.

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Article by Engelmayr et al.

Transfer-printing of ultrathin silicon films onto flexible substrates leads to semitransparent and large-scale arrays of integrated solar micro-cells with photovoltaic energy-conversion efficiencies of 6-8%.

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Article by Yoon et al.

Materials in the classes of skutterudites and clathrates are considered good thermoelectrics due to their low thermal conductivity. This is normally attributed to the effect of 'rattling' atoms that induce a disordered structure known as a 'phonon glass'. Experimental studies now elucidate the effect of rattlers and demonstrate that they induce glass-like conductivity, even if the phonon-glass picture may not be appropriate.

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Article by Koza et al.

The scales of a fish are its first level of defence. Now, the four-layered structure of fish scales has been analysed according to its mechanical properties and penetration resistance. This study of the different layers provides a mechanistic understanding of evolutionary design as well as inspiration for new materials for protective armour.

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Article by Bruet et al.

The contractile forces of cells can cause extracellular matrices to detach from their surroundings, which is problematic for biological studies and tissue engineering. Now, multiple phases of cell-seeded hydrogels can be integrated using a collagen-fibre-mediated method, resulting in the construction of well-defined and stable patterns of three-dimensional matrices.

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Letter by Gillette et al.

Fabrication of complex 2D patterns is now possible using 'rails' as a guiding mechanism for the self assembly of microstructures within fluidic channels. The movement of the structures is controlled by the rails, rather than the channel flow, resulting in a highly precise method capable of making heterogeneous systems, for example, patterns of different living cells for tissue engineering, or even a depiction of the Eiffel Tower.

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Article by Chung et al.

Cluster expansion is a particularly successful computational method that enables the identification of the relationship between lattice configurations and scalar properties in crystals. The introduction of a tensorial analogue of the method will enable prediction of tensor-valued properties. The model is validated by predicting anisotropic properties relevant to semiconductor optoelectronic devices.

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Letter by A. van de Walle

"L'eclatement des celestins" (1964), a typical work of art by Jacques Villegle. The pointy torn shapes in Villegle's work are very familiar, but the reasons these shapes arise when adhesive films are peeled were unknown until now. Understanding the mechanism behind this phenomenon could lead to new tests for the mechanical properties of thin films. (c) ADAGP, Paris and DACS, London 2008.

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Article by Hamm et al.

Atoms on the surfaces of crystals have fewer interactions than those in the bulk, resulting in a contraction of the inter-atomic lengths. Coherent diffraction and molecular simulations show that the contractions of interatomic lengths in nanocrystals are strongly dependent on the surface orientation, providing unique information for these materials systems, which have physical and structural properties dominated by the surfaces.

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Article by Huang et al.

The insensitivity of the mechanical properties of wet, granular matter - such as sandcastles - to their liquid content is not well understood. X-ray microtomography demonstrates that this behaviour results from the organization of the liquid into a variety of bridges and clusters. For spherical as well as non-spherical grains, a simple geometric rule relating the macroscopic properties to the internal liquid morphologies is proposed.

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Letter by Scheel et al.

Gold nanoparticles play an important role in a number of technical applications ranging from optoelectronics to biosensing. An understanding of the morphology of these nanoparticles is important for these applications. For the first time, the precise internal distribution of strain in decahedral gold nanoparticles has been determined conclusively. These findings are of importance as they may enable engineering of the electronic and optical properties of such multiply twinned nanoparticles.

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Letter by Johnson et al.

The 'colossal' magnetoresistance that originates from an insulator-to-metal transition in some manganites makes these important compounds. The nature of the insulating phase has been subject to intense debate, but is widely assumed to be due to strong localization of electrons at the manganese ions, so that the valence state of the manganese ion varies periodically throughout the crystal, forming a charge-ordered state. Experimental findings now support a totally different interpretation that is based on a collective variation of electronic charge density across the crystal, the so-called sliding charge-density wave.

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Letter by Cox et al.