February 20, 2006

High-tech virus films

Nature is proving to be a particularly versatile resource for finding simple, inexpensive ways of building high-tech materials and devices.

Researchers from the Massachusetts Institute of Technology have advanced their technique of using viruses to build extremely thin films of material molecule-by molecule by engineering a bacteria-invading virus to form rigid rods, using electrostatic forces to make the virus rods line up in a single layer, and then covering the viruses with metal or semiconductor nanoparticles, or encapsulating them to form nanowires.

The researchers formed the virus layers on top of flexible plastic films that can be made as thin as 10 nanometers. The method taps inexpensive chemical fabrication techniques that can be used with a wide variety of materials that have useful electronic, magnetic and optical properties.

The virus-coated films could be used to make chemical and biological sensors and electronic devices like lightweight, flexible electrodes for batteries, solar cells and light-emitting diodes.

(Spontaneous Assembly of Viruses on Multilayered Polymer Surfaces, Nature Materials, published online February 19, 2006)

Rubber crystal has light touch

Photonic crystal -- material with tiny regularly spaced holes -- precisely controls lightwaves, opening the way for lightning fast computer chips that use light rather than electrical signals and tiny communications devices.

Researchers from the University of Toronto and the European Laboratory for Non-linear Spectroscopy have given the concept of photonic crystal a twist. They have made photonic crystal from rubber, which means the crystal's light-controlling properties can be reversibly changed by stretching and compressing the crystal.

The rubber photonic crystal could be used to make optical devices that are sensitive to pressure. Potential applications include highly-accurate color fingerprinting, color displays, air-bag sensors, building strain sensors, and tunable light-emitting diodes and lasers.

(From Colour Fingerprinting to the Control of Photoluminescence in Elastic Photonic Crystals, Nature Materials, published online February 19, 2006)

Bits and pieces

Enzymes compute

The right combination of enzymes, hydrogen peroxide, and glucose forms a chemical computer that carries out basic binary logic functions. The method could be used to monitor biochemical processes and to make high-speed hybrid chemical-electronic computers.

(Elementary Arithmetic Operations by Enzymes: A Model for Metabolic Pathway Based Computing, Angewandte Chemie International Edition, February 27, 2006)

Quantum crypto advances demoed

A pair of upcoming papers demonstrate promising methods for simplifying and improving quantum cryptography systems. One method uses a photon's position within an array of pixels to transmit 4.5 bits of information per photon rather than just one. The other method uses decoy signals to detect eavesdroppers.

(Quantum Key Distribution with Higher-Order Alphabets Using Spatially Encoded Qudits, Experimental Quantum Key Distribution with Decoy States, scheduled for publication in Physical Review Letters)

Swollen lenses make biosensor

Microscopic hydrogel lenses change size, and thus focus, in the presence of specific amounts of antibodies. The lenses promise to be sensitive biosensors for diagnosing diseases and developing drugs.

(Label-Free Biosensing with Hydrogel Microlenses, Angewandte Chemie International Edition, February 20, 2006)

Nanofluidics tune light chips

A combination of nanoscale fluidic channels and photonic crystal -- materials that contain tiny, regularly spaced holes -- makes a material that can be filled with liquid in order to change its lightwave-controlling properties. The technique could be used to make chemical and biological sensors that can detect and analyze individual molecules and optical communications devices that can be reconfigured on-the-fly.

(Nanofluidic Tuning of Photonic Crystal Circuits, Optics Letters, January 1, 2006)