Volume 12 Issue 3, March 2013

Unique opportunities arise from exceptional points that coalesce states of an open system in synthetic photonic media, where delicately balanced complex dielectric functions produce unprecedented optical properties.

Open crystalline configurations self-assembled from colloids with sticky patches have recently been shown to be unexpectedly stable. A theory that accounts for the entropy of the colloids' thermal fluctuations now explains why.

Assessing when cell death occurs following in vivo transplantation of stem cells is challenging. Now, pH-sensitive hydrogel capsules containing arginine-based liposomes are shown to act as magnetic resonance imaging contrast agents, allowing cell death to be monitored within the capsules.

Materials displaying negative linear compressibility are, at present, the exception rather than the rule. An unusually large and persistent example of this phenomenon in the molecular framework material zinc dicyanoaurate dramatically expands the range of mechanical responses conceivable in other materials.

The cytoplasm of living cells responds to deformation in much the same way as a water-filled sponge does. This behaviour, although intuitive, is connected to long-standing and unsolved fundamental questions in cell mechanics.

The complete elastic response of a spider's orb web has been quantified by non-invasive light scattering, revealing important insights into the architecture, natural material use and mechanical properties of the web. This knowledge advances our understanding of the prey-catching process and the role of supercontraction therein.

In a uniformly aligned liquid crystal, colloidal particles having a number of holes give rise to arrays of topological defects that are associated with the particles' topology.

High-throughput computational approaches combining thermodynamic and electronic-structure methods with data mining and database construction are increasingly used to analyse huge amounts of data for the discovery and design of new materials. This Review provides an overall perspective of the field for a broad range of materials, and discusses upcoming challenges and opportunities.

The dynamical properties of single-chain magnets are difficult to control experimentally. The demonstration of a scheme for switching individual spins optically now allows for the study and manipulation of dynamical processes in magnetic nanowires with comparative ease.

The appealing electronic properties of the monolayer semiconductor molybdenum disulphide make it a candidate material for electronic devices. The observation of tightly bound trions in this system—which have no analogue in conventional semiconductors—opens up possibilities for controlling these quasiparticles in future optoelectronic applications.

The expansion of a material in one or more directions under increasing hydrostatic pressure is a phenomenon known as negative linear compressibility. The demonstration that zinc dicyanoaurate exhibits an unusually large negative linear compressibility opens up possibilities for designing other materials with comparable properties.

The design of open crystalline arrangements of colloidal particles with attractive patches has been hampered by the difficulty in exploring the full range of conceivable parameters both experimentally or with simulations. An analytical theory that explains the role of entropy in stabilizing open colloidal lattices and that predicts the conditions at which stable crystal structures of patchy particles form is now reported.

Because it is an intrinsically slow technique, scanning tunnelling microscopy is not usually useful for studying the dynamics of particles on a surface. This issue is now solved by using scanning noise microscopy, which yields a complete characterization of copper phthalocyanine molecules on Cu(111), ranging from the dynamical processes to the underlying electronic structure at the single-molecule level.

Rechargeable metal–air batteries are considered particularly attractive due to their potential high-energy densities and simplicity of the underlying cell reaction. A room-temperature sodium–oxygen cell with an ether-based electrolyte demonstrates enhanced current densities using pure carbon cathodes without an added catalyst.

Non-trivial topological phases can allow for one-way spin-polarized transport along the interfaces of topological insulators but they are relatively uncommon in the condensed state of matter. By arranging judiciously designed metamaterials into two-dimensional superlattices, a photonic topological insulator has now been demonstrated theoretically, enabling unidirectional spin-polarized photon propagation without the application of external magnetic fields or breaking of time-reversal symmetry.

The control and manipulation of the magnetization of thin metallic films by means of an electric current is a promising strategy for ensuring that potential spintronic applications are energy efficient. It is now shown that large changes in the current-induced magnetic field can arise as a result of varying the thickness of the Ta layer in Ta|CoFeB|MgO heterostructures.

Graphene has attracted considerable interest for future electronics, but the absence of a bandgap limits its direct applicability in transistors and logic devices. It is now shown that vertical integration with MoS₂ and other layered materials enables the fabrication of vertical field-effect transistors with large on/off ratios and high current densities as well as complementary inverters with larger-than-unity voltage gain.

It has been suggested that the cytoplasm of living cells can be described as a porous elastic meshwork bathed in an interstitial fluid. Microindentation tests now show that intracellular water redistribution plays a fundamental role in cellular rheology and that at physiologically relevant timescales cellular responses to mechanical stresses are consistent with such a poroelastic model.

The mechanical properties of a spider’s web are spatially mapped using Brillouin light scattering. This non-contact approach can probe the elastic properties of single fibres, intersection points and glue spots within the web, as well as measure how the elastic stiffness changes in supercontracted silk fibres.

The monitoring of cell survival and functionality following their in vivo transplantation remains a challenge in clinical cell therapy. Now, using magnetic resonance imaging techniques and microcapsules with pH-sensitive components, in vivo cell death and cell viability patterns can be assessed with high anatomical accuracy.