Volume 9 Issue 2, February 2010

To deepen understanding and hasten the development of treatments, cancer needs to be modelled more accurately in vitro; applying tissue-engineering concepts and approaches in this field could bridge the gap between two-dimensional studies and in vivo animal models.

The concept of using magnetic micro- and nanoparticles for targeting solid tumours with drugs was first proposed over three decades ago, but has yet to translate into a clinical application. Rethinking the mechanistic approach could circumvent the difficulties that have stood in its way.

By using an ionic liquid as a gate dielectric, superconductivity can be induced in an inorganic band insulator up to a temperature of 15 K by an electric field, opening new directions in superconductivity research.

Stable particle-like molecular architectures are written in a frustrated chiral-nematic liquid crystal using a vortex laser beam. This fundamentally new mechanism to form toroidal features with anisotropic optical properties has great potential to create new applications in liquid-crystal photonics.

Stimuli-responsive polymers can be engineered, in both film and colloid forms, to respond to a variety of inputs, from temperature to pH. The inherent flexibility in their structure and responses result in materials that lend themselves to applications ranging from drug delivery to sensing. Recent advances and future challenges in this direction are reviewed.

Jamming transitions of disordered systems such as foams, gels and colloidal suspensions, describe the change from a liquid to a solid state. An investigation of the three-dimensional properties of jamming shows how, for example, unjamming occurs simultaneously in all directions even if it is induced in one direction only.

Coherent X-ray diffraction spectroscopy has recently emerged as a powerful tool for imaging strain at the nanoscale. Developments in both fabrication and experimental techniques have now enabled all nine components of the strain tensor in a nanorod to be determined, demonstrating the ability of coherent X-ray diffraction spectroscopy to yield measurements of strain in three dimensions with a resolution of a few tens of nanometres.

Using a liquid gate has allowed electrically induced superconductivity in a solid specimen by means of carrier accumulation on the surface. But this phenomenon was limited to materials that became superconductors at low carrier density. It is now shown that superconductivity can be induced in a much wider range of materials by using an ionic liquid.

One of the more promising uses of metamaterials is in imaging, where the capability to control the propagation of light could lead to new applications. In particular, the realization of a broadband metamaterial lens that has an almost complete hemispherical field of view that is focused on a flat plane represents a significant step towards such new uses.

Electrostatic control of spin polarization is a promising route for developing efficient spintronic devices, but is challenging for materials with a small spin–orbit interaction. It is now shown that an electric field can be used to vary the spin polarization in a silicon quantum well by exploiting the discrete nature of the energy levels. This route may work for other inorganic and organic materials.

Chiral nematic liquid-crystal phases consist of rod-shaped molecules that have a preference to twist. However, applied fields force them to exist without the twist. Introducing particle-like twists, so called torons, using laser light relieves this frustration by facilitating the reappearance of the twist. The presence of torons could extend the use of liquid crystals in electro-optic and photonic devices.

Capacitive energy storage is technologically attractive because of its short charging times and its ability to deliver more power than batteries. The capacitive charge-storage properties of mesoporous films of MoO₃ with iso-oriented grains now lead to pseudocapacitive materials that offer increased energy density while still maintaining high power density.

The morphology and structure of polymer blends is central to charge-carrier, exciton and photon management in organic light-emitting diodes, transistors and solar cells. A broadly applicable approach, based on mixing a photocrosslinkable moiety into semiconducting polymers, enables the simple formation of heterostructured blends with control of morphology and structure for use in all types of device.

Surfaces with physicochemical properties that can be modulated using external stimuli offer great promise for designing responsive or adaptive materials. Now, biocompatible dynamic scaffolds based on thin hydrogel coatings that reversibly hide and display surface chemical patterns in response to temperature changes have been fabricated.

Biocompatible, lithographically defined, ferromagnetic microdiscs that have a spin-vortex ground state oscillate when activated by an alternating magnetic field. This oscillation compromises the integrity of the cell membrane and initiates programmed cell death in ∼90% of cancer cells in vitro, even with a low-frequency field applied for only ten minutes.

An important challenge in medicine is the efficient delivery of drugs in the body using non-toxic nanocarriers. Porous metal–organic frameworks with imaging properties are now used as nanoscale carriers for the controlled delivery of antitumour and retroviral drugs against cancer and AIDS.