January 16, 2006

Magnetic logic advances

Magnetic memory chips, which retain data after the power is turned off, are becoming available and could eventually supplement or even replace disk drives in computers. Several research teams are looking to take this technology beyond simply storing data by using it in computer chips that process data.

Researchers from the University of Notre Dame and the Technical University of Munich in Germany have taken a step toward magnetic logic chips with a prototype device that carries out the basic binary logic operations necessary for computing. The device uses nanoscale magnets in a quantum dot cellular automata architecture that was previously developed at Notre Dame. (See Quantum dot logic advances, TRN, October 11, 2000)

The minuscule oblong magnets are arranged in sets of eight to form majority gates, which are a type of binary logic gate that uses three inputs and one output. Combinations of of this type of gate can produce all of the necessary logic for today's computers.

Magnetic logic uses little power and retains data without power. Magnetic logic could someday be used to make computers that turn on instantly without having to boot up and computer chips that can be easily reconfigured.

(Majority Logic Gate for Magnetic Quantum-Dots Cellular Automata, Science, January 13, 2006)

Seeing the light of Net access

High-speed Internet access and wireless home networks are widespread technologies, and researchers are working to make them faster and cheaper.

Researchers from the Pennsylvania State University have designed a network based on a pair of emerging technologies: broadband over powerlines and optical wireless networks. Broadband over powerlines brings data communications, including Internet access, over powerlines to every outlet and light fixture in a home. Optical wireless networks transmit data using lightwaves.

The scheme uses white light-emitting diodes (LEDs) for lighting and networking. Most research on optical wireless networks calls for infrared light rather than white light. White light-emitting diodes are emerging as a low-power, low-cost alternative to incandescent and fluorescent lighting. The wireless networking techniques developed for infrared also apply to white light, but the white light sources used for illumination provide better wireless coverage than infrared systems.

With the right configurations, in-home powerlines and optical wireless networks could transmit data at 1 gigabit per second. High-speed Internet connections via cable and telephone lines typically range from 1.5 to 8 megabits per second, and today's radio-based wireless networks range from 11 to 108 megabits per second.

The scheme could provide a simple, cost-effective way of bringing high-speed networking to computers, televisions and telephones throughout homes and offices.

(Broadband Access over Medium and Low Voltage Powerlines and Use of White Light Emitting Diodes for Indoor Communications, IEEE Consumer Communications & Networking Conference, Las Vegas, Nevada, January 8-10, 2006)

Carbon gets more hydrogen

Hydrogen is a clean-burning fuel, but using it as an environmentally friendly energy source requires finding clean ways to produce it. One of the most promising approaches is solar water-splitting, a scheme to use sunlight to drive the chemical separation of hydrogen and oxygen from water.

The catalyst is the key to splitting water into oxygen and hydrogen. Much recent research has focused on titanium dioxide catalysts, and last year researchers found that nanotubes made of titanium dioxide are more effective than bulk titanium dioxide. The catch is pure titanium dioxide only works with ultraviolet light, which makes up only a small portion of sunlight. (See Nanotubes crank out hydrogen, TRN, February 9/16, 2005)

Researchers from the University of Texas at Austin have found a way to add carbon to the titanium dioxide nanotubes in order to shift their catalytic activity from ultraviolet to visible light. They also found that the length of the nanotubes plays a key role; 3.3 microns is optimum.

The carbon-infused titanium dioxide nanotubes generated more hydrogen from sunlight than pure titanium dioxide nanotubes.

(Novel Carbon-Doped TiO2 Nanotube Arrays with High Aspect Ratios for Efficient Solar Water Splitting, Nano Letters, January 11, 2006)

Chemistry pumps artificial muscle

Much of the research into artificial muscle involves using electricity or temperature to change the shape of polymer materials. A major aim of this research is to use these materials to someday power machines like robots.

Biological muscle, however, is chemically driven, and early attempts to make chemically driven artificial muscle have yielded tiny, unstable devices that could not scale up to larger sizes.

Researchers from the University of Sheffield in England, the Council for the Central Laboratory of the Research Councils (CCLRC) in England, and the European Synchrotron Radiation Facility (ESRF) in France have overcome these problems with a block copolymer material that combines two polymers at the molecular scale.

The researchers' synthetic muscle increases in volume three times in the presence of a high pH solution and contracts in the presence of a low pH solution.

The material is a 90-nanogram weakling compared to biological muscle; it is one million times less powerful than myosin and 10,000 times weaker than striated muscle. It is also extremely slow, completing a cycle of expansion and contraction in about 20 minutes.

However, it demonstrates that biological-like artificial muscle is possible, and there are routes to making the chemically-driven device much more powerful, according to the researchers. Such muscles could tap chemical energy directly rather than having to convert it into electricity or heat, which could eventually make artificial muscle more practical.

(Reciprocating Power Generation in a Chemically Driven Synthetic Muscle, Nano Letters, January 11, 2006)

Bits and pieces

A bacterial protein controls the speed of light down to an extremely slow one millimeter per second, dead bacteria rotated by laser beams make useful microfluidic pumps, a combination of nanoscale "near field" light and ordinary "far field" light promises high-speed interconnects for parallel processing supercomputers.

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