Uncertain next steps - p851

doi:10.1038/nmat2556

The future role of NASA in human space exploration remains economically uncertain. Should materials scientists care?

Full Text - Uncertain next steps | PDF (164 KB) - Uncertain next steps

Our choice from the recent literature - p852

doi:10.1038/nmat2555

Full Text - Our choice from the recent literature | PDF (149 KB) - Our choice from the recent literature

Oxide dielectrics: A change of direction - pp853 - 854

Hagen Klauk

doi:10.1038/nmat2552

Field-effect transistors, regardless of whether they use an organic or an inorganic semiconductor, require a gate dielectric with a large relative permittivity. A once-popular layered electrolyte may be just the right material for the job.

Full Text - Oxide dielectricsA change of direction | PDF (231 KB) - Oxide dielectricsA change of direction

See also: Article by Pal et al.

Magnetic shape memory: Magnetoelastic sponges - pp854 - 855

Mehmet Acet

doi:10.1038/nmat2551

Nickel–manganese–gallium foams connected internally by sizeable single-crystalline elements provide magnetic-field-induced strains comparable to free-standing bulk single crystals, and demonstrate feasibility for the application of magnetic shape memory.

Full Text - Magnetic shape memoryMagnetoelastic sponges | PDF (131 KB) - Magnetic shape memoryMagnetoelastic sponges

See also: Letter by Chmielus et al.

Biodegradable Alloys: The glass window of opportunities - pp855 - 857

Evan Ma & Jian Xu

doi:10.1038/nmat2550

Crystalline alloys often fall short in providing certain key properties desired for biomedical applications. But by using metallic glasses instead, problems such as hydrogen evolution can be dramatically reduced in biodegradable magnesium alloys.

Full Text - Biodegradable AlloysThe glass window of opportunities | PDF (188 KB) - Biodegradable AlloysThe glass window of opportunities

See also: Letter by Zberg et al.

Carbon nanotubes: Not that slippery - pp857 - 858

Ruben Perez

doi:10.1038/nmat2553

Friction measurements on carbon nanotubes show a remarkable anisotropy, the origin of which can be traced to the activation of specific deformation modes of energy dissipation.

Full Text - Carbon nanotubesNot that slippery | PDF (188 KB) - Carbon nanotubesNot that slippery

See also: Letter by Lucas et al.

Organic electronics: Electrical contacts - pp858 - 860

Natalie Stingelin

doi:10.1038/nmat2562

Further achievements in the realm of organic and molecular electronics — even at the level of device applications — requires greater understanding of the materials at a fundamental level. This insight can only come with input from researchers in several disciplines working together on the materials from different perspectives.

Full Text - Organic electronicsElectrical contacts | PDF (283 KB) - Organic electronicsElectrical contacts

Material witness: Shaking hands with robots - p860

Philip Ball

doi:10.1038/nmat2554

Full Text - Material witnessShaking hands with robots | PDF (111 KB) - Material witnessShaking hands with robots

Giant magnetic-field-induced strains in polycrystalline Ni–Mn–Ga foams - pp863 - 866

M. Chmielus, X. X. Zhang, C. Witherspoon, D. C. Dunand & P. Müllner

doi:10.1038/nmat2527

The magnetic-field-induced strain in magnetic shape-memory alloys can be used in several types of application. However, the strain is high (10%) only in single-crystalline specimens, which are difficult and expensive to obtain. Polycrystalline samples with comparable strain have now been fabricated by introducing pores of similar size to the grains.

First Paragraph - Giant magnetic-field-induced strains in polycrystalline Ni-Mn-Ga foams | Full Text - Giant magnetic-field-induced strains in polycrystalline Ni–Mn–Ga foams | PDF (630 KB) - Giant magnetic-field-induced strains in polycrystalline Ni–Mn–Ga foams | Supplementary information

Subject Categories: Magnetic materials | Mechanical properties

See also: News and Views by Acet

Plasmonic nanorod metamaterials for biosensing - pp867 - 871

A. V. Kabashin, P. Evans, S. Pastkovsky, W. Hendren, G. A. Wurtz, R. Atkinson, R. Pollard, V. A. Podolskiy & A. V. Zayats

doi:10.1038/nmat2546

Plasmonic biosensors are either based on freely propagating surface plasmons or plasmons localized at nanostructures. Despite advantages such as quantitative detection, localized surface-plasmon sensors have shown lower overall sensitivities. A nanorod metamaterial supporting new plasmonic modes is now shown to considerably outperform earlier plasmonic biosensors by combining and expanding their respective advantages.

First Paragraph - Plasmonic nanorod metamaterials for biosensing | Full Text - Plasmonic nanorod metamaterials for biosensing | PDF (919 KB) - Plasmonic nanorod metamaterials for biosensing | Supplementary information

Subject Categories: Optical, photonic and optoelectronic materials | Sensors and biosensors

Application of a quartz-crystal microbalance to measure ionic fluxes in microporous carbons for energy storage - pp872 - 875

Mikhael D. Levi, Grigory Salitra, Naomi Levy, Doron Aurbach & Joachim Maier

doi:10.1038/nmat2559

Conventional electroanalytical and structure-analysis techniques provide limited information about ionic fluxes in electrochemical systems. A quartz crystal microbalance is now used as a gravimetric probe of the concentration and compositional changes in microporous activated carbon.

First Paragraph - Application of a quartz-crystal microbalance to measure ionic fluxes in microporous carbons for energy storage | Full Text - Application of a quartz-crystal microbalance to measure ionic fluxes in microporous carbons for energy storage | PDF (2,287 KB) - Application of a quartz-crystal microbalance to measure ionic fluxes in microporous carbons for energy storage | Supplementary information

Subject Categories: Materials for energy | Porous materials | Characterisation and analytical techniques

Hindered rolling and friction anisotropy in supported carbon nanotubes - pp876 - 881

Marcel Lucas, Xiaohua Zhang, Ismael Palaci, Christian Klinke, Erio Tosatti & Elisa Riedo

doi:10.1038/nmat2529

When a tip slides on a carbon nanotube, the friction along the transverse direction is much larger than in the parallel direction. It is shown that this behaviour is due to hindered rolling of the tube, and a frictional dissipation that is negligible for a tip sliding along the axis.

First Paragraph - Hindered rolling and friction anisotropy in supported carbon nanotubes | Full Text - Hindered rolling and friction anisotropy in supported carbon nanotubes | PDF (1,144 KB) - Hindered rolling and friction anisotropy in supported carbon nanotubes | Supplementary information

Subject Categories: Mechanical properties | Nanoscale materials

See also: News and Views by Perez

Linking catalyst composition to chirality distributions of as-grown single-walled carbon nanotubes by tuning Ni_xFe_1-x nanoparticles - pp882 - 886

Wei-Hung Chiang & R. Mohan Sankaran

doi:10.1038/nmat2531

Although much effort has been directed towards the separation of single-walled carbon nanotube mixtures, chiral-selective growth is required for scalable production and applications. The chiral distribution of carbon nanotubes can now be altered by varying the composition of nickel–iron nanocatalysts.

First Paragraph - Linking catalyst composition to chirality distributions of as-grown single-walled carbon nanotubes by tuning Ni: x: Fe: 1-: x: nanoparticles | Full Text - Linking catalyst composition to chirality distributions of as-grown single-walled carbon nanotubes by tuning NixFe1-x nanoparticles | PDF (2,782 KB) - Linking catalyst composition to chirality distributions of as-grown single-walled carbon nanotubes by tuning NixFe1-x nanoparticles | Supplementary information

Subject Categories: Catalytic materials | Nanoscale materials

MgZnCa glasses without clinically observable hydrogen evolution for biodegradable implants - pp887 - 891

Bruno Zberg, Peter J. Uggowitzer & Jörg F. Löffler

doi:10.1038/nmat2542

The mechanical properties and corrosion behaviour of glassy metals are attractive for biodegradable implants. Magnesium-based glasses are particularly promising but they suffer from hydrogen evolution during corrosion. A distinct reduction in hydrogen evolution is now observed in zinc-rich magnesium glasses showing good tissue compatibility.

First Paragraph - MgZnCa glasses without clinically observable hydrogen evolution for biodegradable implants | Full Text - MgZnCa glasses without clinically observable hydrogen evolution for biodegradable implants | PDF (1,088 KB) - MgZnCa glasses without clinically observable hydrogen evolution for biodegradable implants

Subject Categories: Metals and alloys | Glasses | Biomedical materials

See also: News and Views by Ma & Xu

Enhanced ordering temperatures in antiferromagnetic manganite superlattices - pp892 - 897

S. J. May, P. J. Ryan, J. L. Robertson, J.-W. Kim, T. S. Santos, E. Karapetrova, J. L. Zarestky, X. Zhai, S. G. E. te Velthuis, J. N. Eckstein, S. D. Bader & A. Bhattacharya

doi:10.1038/nmat2557

One of the attractions in studying oxide heterostructures is the unusual physical phenomena that they enable. It is now demonstrated that the enforced cation ordering in thin oxide superlattices leads to significantly enhanced magnetic ordering temperatures.

Abstract - Enhanced ordering temperatures in antiferromagnetic manganite superlattices | Full Text - Enhanced ordering temperatures in antiferromagnetic manganite superlattices | PDF (795 KB) - Enhanced ordering temperatures in antiferromagnetic manganite superlattices | Supplementary information

Subject Categories: Magnetic materials | Surface and thin films

Solution-deposited sodium beta-alumina gate dielectrics for low-voltage and transparent field-effect transistors - pp898 - 903

Bhola N. Pal, Bal Mukund Dhar, Kevin C. See & Howard E. Katz

doi:10.1038/nmat2560

Sodium beta-alumina (SBA) compositions are well known as ionic conductors. Nevertheless, ionic and electron conductivities perpendicular to the lattice planes in the material are very low. It is now shown that by exploiting this property, SBAs can be used as transistor gate dielectrics in solution-processed devices using oxide-based and polymer electrodes.

Abstract - Solution-deposited sodium beta-alumina gate dielectrics for low-voltage and transparent field-effect transistors | Full Text - Solution-deposited sodium beta-alumina gate dielectrics for low-voltage and transparent field-effect transistors | PDF (930 KB) - Solution-deposited sodium beta-alumina gate dielectrics for low-voltage and transparent field-effect transistors | Supplementary information

Subject Categories: Ceramics | Structural materials | Electronic materials

See also: News and Views by Klauk

On the origin of the open-circuit voltage of polymer–fullerene solar cells - pp904 - 909

Koen Vandewal, Kristofer Tvingstedt, Abay Gadisa, Olle Inganäs & Jean V. Manca

doi:10.1038/nmat2548

The efficiency of solar cells depends not only on the generated current, but also the photovoltage produced. Ground-state charge-transfer complexes are shown to have an important role in influencing the open-circuit voltage of several polymer–fullerene solar-cell blends; future chemical tuning of the polymers could maximize the complexes' role in affecting the voltage for increased power-conversion efficiency.

Abstract - On the origin of the open-circuit voltage of polymer-fullerene solar cells | Full Text - On the origin of the open-circuit voltage of polymer–fullerene solar cells | PDF (694 KB) - On the origin of the open-circuit voltage of polymer–fullerene solar cells | Supplementary information

Subject Categories: Polymers | Optical, photonic and optoelectronic materials | Materials for energy

Non-entropic and reversible long-range deformation of an encapsulating bioelastomer - pp910 - 916

Ali Miserez, S. Scott Wasko, Christine F. Carpenter & J. Herbert Waite

doi:10.1038/nmat2547

Bioelastomers generally show elasticity similar to that of rubber, which originates from entropic forces linked to deformation. It is now shown that in the egg capsule of a large marine shell, the elasticity is instead based on a structural transition. The results could have a significant impact on engineering protective encapsulating systems inspired by natural elastomers.

Abstract - Non-entropic and reversible long-range deformation of an encapsulating bioelastomer | Full Text - Non-entropic and reversible long-range deformation of an encapsulating bioelastomer | PDF (1,005 KB) - Non-entropic and reversible long-range deformation of an encapsulating bioelastomer | Supplementary information

Subject Categories: Biological materials | Mechanical properties