Reviews & Analysis

A study on carrier-collection efficiency in various organic photovoltaic systems now reveals that ultrafast relaxation of photoexcitations within the manifold of charge-transfer states does not impede mobile charge carrier generation.

Reversible strains up to 14% driven by changes in temperature or electric field have been realized in a thin film of bismuth ferrite oxide.

The energetic and kinetic behaviours of water-oxidation catalysts deposited on semiconductor electrodes are probed in situ, elucidating the junction formed between them, and transforming the design principles of the catalysts.

Planar patterns of colloidal microparticles have been manufactured with high yield over square centimetre areas by using magnetic-field microgradients in a paramagnetic fluid. This approach could evolve into technology capable of printing three-dimensional objects through programmable and reconfigurable 'magnetic pixels'.

Memory devices based on the spin-transfer-torque effect offer a range of attractive properties, such as speed of operation and low energy cost. This Progress Article outlines a strategy for assembling different nanodevices based on the spin-torque effect to achieve qualitatively different computing architectures.

Scanning probe techniques reveal an intricate interplay between the formation of structural domains in strontium titanate and electronic transport effects at oxide interfaces.

Measurements of the structure and organization of intact bone samples show that water plays a significant role in orienting bone apatite crystals, and that such ordering is mediated by an amorphous mineral coating layer.

Mixed-halide organic–inorganic hybrid perovskites are reported to display electron–hole diffusion lengths over 1 μm. This observation provides important insight into the charge-carrier dynamics of this class of semiconductors and increases the expectations for highly efficient and cheap solar cells.

Adult cells can be routinely reprogrammed into pluripotent stem cells by chemical and genetic means, such as the expression of a cocktail of exogenous transcription factors. It is now shown that growing cells on substrates with aligned features such as microgrooves can enhance this process.

Traps in organic semiconducting crystals are healed when a perfluoropolyether oil is deposited on the surface of these materials, thus making possible the detection of intrinsic features of charge-carrier transport in rubrene and tetracene.

Poorly ordered films of conjugated polymers that show high charge mobility recently challenged the idea that disorder is detrimental for electrical conduction. Systematic studies now reveal that long polymeric chains can bridge small crystalline domains thus supporting charge transport on length scales relevant for device operation.

Advances in photochemistry have profoundly impacted the way in which biology is studied. Now, a photoactivated enzymatic patterning method that offers spatiotemporal control over the presentation of bioactive proteins to direct cells in three-dimensional culture significantly expands the available chemical toolbox.

Cells can sense their environment by applying and responding to mechanical forces, yet how these forces are transmitted through the cell's cytoskeleton is largely unknown. Now, a combination of experiments and computer simulations shows how forces applied to the cell cortex are synergistically shared by motor proteins and crosslinkers.

Therapeutics based on small interfering RNA (siRNA), which in principle are able to reversibly silence any gene of interest, are under development for the treatment of cancers, viral infections, hereditary disorders and many other diseases. This Review discusses the biological challenges that siRNA delivery materials aim to overcome, as well as the most clinically advanced classes of siRNA delivery systems, including cyclodextrin–polymer nanoparticles, lipid nanoparticles and siRNA conjugates.

The clinical application of vaccines has expanded from infectious diseases to cancer, enhancing our vision of how the immune system can be used to prevent and treat disease. This Review highlights recent developments, clinical successes and future challenges in the design of prophylactic, therapeutic and tolerance-inducing synthetic vaccines with inspiration from the natural immune system.

The use of macroscopic depots to deliver drugs — including small molecules, protein and cells — at the desired treatment site by using a carrier whose physical and chemical properties control the presentation of the drug increases drug effectiveness and reduces side effects. This Review discusses the advantages of macroscopic drug-delivery systems, the associated mechanisms of spatiotemporal control of drug presentation, and the design and use of multifunctional macroscopic drug-delivery devices.

Nanoscale materials that deliver drugs in response to specific stimuli offer enhanced control of the drugs' release profile and distribution. This Review provides a comprehensive discussion of progress during the past five years in the design of nanoscale systems that can respond to exogenous stimuli such as temperature or variations in light or magnetic-field intensities, or to endogenous stimuli such as redox gradients or changes in pH or enzyme concentration.