Genetically modified viruses that assemble into electrodes could one day revolutionise battery manufacturing.

Researchers in the US have created viruses that automatically coat themselves in metals and line up head to tail to form an efficient battery anode 鈥� the negatively charged component that channels electrons to generate current. These nanowires could be used to make revolutionary new forms of lithium-ion batteries, the researchers say.

鈥淣ow it鈥檚 simply a matter of designing the other components, and we鈥檒l be able to form batteries by simply pouring all the ingredients together and letting them self-assemble,鈥� says Angela Belcher, a biological engineer at MIT who led the research. 鈥淧lus we can make them at room temperature in very safe conditions, instead of the high temperatures and dangers usually associated with battery production.鈥�

Belcher鈥檚 team genetically modified tube-shaped viruses that normally infect bacteria to create the electrodes. They introduced snippets of single-stranded DNA that caused the viruses to manufacture specific molecules on their outer coating that attach to cobalt ions and gold particles. This combination turns the virus into an efficient anode as they provide an ideal conduit for electrons.

Going for gold

To find the right genetic code to produce the gold-clinging molecules, or complexes, Belcher鈥檚 team exposed billions of viruses with slightly different DNA to gold and then extracted genetic material from the ones that most strongly interacted with the metal. To create the cobalt-clinging complexes, the team created genetic code from scratch by mimicking the code which enables animal cells to harvest calcium. This is because cobalt can be harvested in a similar way to calcium.

The genetic material added to the viruses can easily be interchanged, the researchers say, so it should be relatively simple to create other electronic components, including a positively charged battery electrode (cathode) using the technique.

This flexibility is one of the most powerful aspects of the work, says Trevor Douglas, a pioneer of nanomaterial chemistry at Montana State University in the US, who was not involved with the work. 鈥淭his proves that you can harness these viruses to do many different things,鈥� he says. 鈥淚t raises the bar for everyone else in the field. We can鈥檛 be satisfied proving principles 鈥� we have to move this on to actually utilising these principles.鈥�

The other important aspect, he says, is scalability. The team modified the viruses to cling to a surface 鈥� producing 10-centimetre-long anode sheets. 鈥淭hey took this from the nanoscale to the macroscopic, which could mean batteries of every shape and size,鈥� Douglas adds. 鈥淚t鈥檚 not hard to imagine these being produced on a factory-scale.鈥�

But the research may also be useful for other energy technologies. Belcher is currently investigating how to use viruses to create self-assembling solar cells.

Journal reference: Science (DOI: 10.1126/science.1122716)

Glasses that change from 鈥渓ong distance鈥� to 鈥渞eading鈥� mode at the flick of a switch could prove a revelation for many wearers.

Researchers have developed a prototype that uses liquid crystals to change focus in an instant, thus preventing the eye strain induced by wearing conventional bifocal glasses. Focusing through specific portions of a bifocal lens causes many users to become dizzy or disoriented, while others report increased eye fatigue.

鈥淏ifocals effectively work the same way they have since they were invented by Benjamin Franklin,鈥� says Nasser Peyghambarian, a professor of optical sciences at Arizona State University, US, who helped develop the 鈥渄ynamic鈥� glasses. 鈥淏ut as any of more than 40 million people in America who need bifocals know, they鈥檙e a pain.鈥�

Fresnel lens

The dynamic glasses change focus using a 5-micron-thick layer of nematic liquid crystal, sandwiched between two pieces of glass. Molecules of the liquid crystal reorient themselves when exposed to an electric field and the researchers used this to create a type of dynamic Fresnel lens.

In a normal Fresnel lens, concentric rings are carved into a piece of glass causing light to become focused in a similar way to a conventional lens. Dynamic glasses mimic the Fresnel effect using concentric circles of clear electrodes on the pieces of glass containing the crystal. Activating these electrodes causes the liquid crystal to align into rings and focus light passing through the lens.

A company called PixelOptics, based in Virginia, US, plans to sell glasses containing dynamic lenses commercially within two years. 鈥淭he prototype is pretty bulky, but when these hit the streets they鈥檒l be virtually indistinguishable from other, very stylish glasses,鈥� says Ronald Blum, CEO of PixelOptics.

Infrared laser

PixelOptics first developed the idea of dynamic focusing while working on large lenses for computer screens. Ideally, these would have allowed near-sighted and far-sighted people to read their monitors without their spectacles. 鈥淎s screens got thinner and thinner, though, the idea became less practical,鈥� Blum says. 鈥淪o instead we decided to move the technology from the computer to the computer user.鈥�

The first commercial dynamic glasses will only be able to switch between a person鈥檚 normal vision and their 鈥渞eading鈥� prescription. However, by applying different voltages and by changing the number of current-carrying rings within each lens it should be possible to produce different magnifications using the same lens, researchers say.

Peyghambarian is now working on glasses that can dynamically refocus on whatever the wearer is looking at. These will most probably use an infrared laser built into the bridge of the glasses to determine how far away an object is. 鈥淭he idea is to put the focusing power found in the lens of a camera on your face all the time,鈥� Peyghambarian told 快猫短视频.

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0600850103)

For 20 years, researchers have worked to develop the perfect high-temperature superconducting wires to replace today鈥檚 copper-based power grid. But the secret, it now seems, is to build flawed ones. The key may be to position non-conducting nanodots at strategic points within the wire.

Electrical current flowing through superconducting materials experiences virtually no resistance, enabling wires of the material to carry high current loads very efficiently. However, such a powerful current will disrupt itself because it produces a strong, fluctuating magnetic field.

By depositing lines of 10-nanometre-wide, non-conducting dots of barium zirconate at fixed distances along the wire, researchers at Oak Ridge National Laboratory, Tennessee, US, have found a way to disrupt current flow in just the right way to tone down these fluctuations.

Slow progress

鈥淭he potential applications for high-temperature superconducting materials are so significant that the people who discovered them were awarded Nobel prizes the year after their announcement,鈥� says Amit Goyal, one of the wire鈥檚 developers. 鈥淏ut we still don鈥檛 have a physical understanding of how they work, so getting anywhere near these applications has taken two decades. Now we may see some steps forward soon.鈥�

The wires, made of yttrium barium copper oxide (YBCO), will first be worked into lightweight and powerful rotating machinery such as generators and motors, says Venkat Selvamanickam, head of materials research at Superpower Inc. The company鈥檚 contractual agreement with Oak Ridge means it will probably be given first refusal to exploit the technology.

However, Selvamanickam says, the 鈥渒iller app鈥� for these wires will be as the infrastructure of tomorrow鈥檚 electrical grid. A typical modern electrical grid based on copper wires can ferry current along with just under 90% efficiency. A grid based on an infrastructure of high-temperature superconducting wires could be more than 97% efficient.

Right now, that is too small a change to merit the cost of installation, says Paul Grant, one of the patent holders of YBCO and a consultant for the US government鈥檚 department of energy.

Widespread blackouts

However, large areas of high power consumption are starting to become problematic for current grids, as was shown by the widespread blackout in Canada and the US in August 2003. Superconducting wires play a large role in building stable grid structures, not only as transmission cables but also as components in transformer stations and other maintenance equipment, Grant says.

鈥淭his change, in the end, is going to be moved by governmental policy,鈥� he says. 鈥淪o it may be politics now that鈥檚 slowing things down more than technology.鈥�

Not that the remaining technological challenges are insignificant. The method Oak Ridge used to produce the wires only spins out lengths measured in inches, rather than miles. There are two techniques for producing longer wires, but it is unclear how they could accommodate the inclusion of nanodots.

Also, the term 鈥渉igh temperature鈥� is somewhat of a misnomer. Such superconducting materials, in this case YBCO, need to be cooled to around -200掳C (conventional superconductors only work at near absolute zero temperatures, closer to -273掳C). This means that a system that circulates liquid nitrogen along the wires would need to accompany any installation.

Fortunately liquid nitrogen is inexpensive, which means that superconducting wire applications such as levitating trains would become economically feasible.

Journal reference: Science (vol 311, p 1911)

Chronic feelings of social isolation are associated with as much as a 30 mmHg rise in a person鈥檚 systolic blood pressure by the age of 65, which could easily push their systolic blood pressure over 150 mmHg, the medical definition of hypertension. The study showed that this is independent of other confounding variables such as smoking, drinking, socioeconomic status and body mass index.

鈥淲hile we haven鈥檛 conclusively proven why this happens, the pieces are starting to fall into place,鈥� says John Cacioppo, a psychologist at the University of Chicago, US, who conducted the research.

鈥淭his shows that how we deal with isolation changes as we age on both emotional and physical levels,鈥� says Sarah Pressman, a health psychologist at Carnegie Mellon University. 鈥淭his is not something that鈥檚 all in your head.鈥�

Lonely youths

Previous work by Cacioppo showed that college students who felt socially isolated had increased vascular tension 鈥� a narrowing of blood vessels that increases resistance to blood flow. Their young bodies could compensate, so the condition did not lead to abnormally high blood pressure, but Cacioppo speculated that the same would not be true in older individuals.

The study drew data from the first year of the Chicago Health, Aging, and Social Relations Study (CHASRS), which ran the full gamut of physical and psychological examinations for 229 individuals born between 1935 and 1952.

These allowed the researchers to assess subjects鈥� social life and glean their own thoughts on social isolation. Combined with a vast array of associated physiological and hormonal data, this could be the gateway to understanding what role loneliness plays in human health, Cacioppo says.

Social connections

鈥淟oneliness isn鈥檛 just stress or depression,鈥� he notes. 鈥淚t鈥檚 a unique physiological and psychological reaction.鈥�

But this physiological reaction is still clouded in mystery. The study confirmed previous findings that the number of social connections a person has can be predictive of whether or not that person is lonely. But it also shows that some of the most outgoing people can still display psychological symptoms of extreme social isolation.

Studies on twins have indicated that genetics probably plays a role in determining susceptibility to loneliness. Cacioppo believes the emotion is the result of evolutionary forces that drove us to form groups and thus increase our ability to survive.

鈥淭his isn鈥檛 a disease, it鈥檚 an important part of what draws us together,鈥� he says. 鈥淲e鈥檝e gone from the selfish gene to the lonely brain.鈥�

It is Cacioppo鈥檚 hope that further research will reveal a more complete picture of the physiological underpinnings of loneliness 鈥� and in doing so help find ways to moderate human feelings of isolation.

Journal reference: Journal of Psychology and Aging (DOI: 10.1037/0882-7974.21.1.000)

US researchers say they have developed 鈥済reen鈥� chemicals that could replace the lead-based primary explosives that are used to detonate everything from blasting caps to ballistic missiles. They also claim their process may make the manufacturing of such energetic compounds safer.

Primary explosives are the relatively weak yet highly sensitive materials used to set off powerful explosions. Lead-based chemicals came into use for this purpose one hundred years ago to replace the even more toxic mercury fulminate.

But studies show that toxic plumes are released as lead-based explosives are discharged. A 1991 survey revealed that maintenance workers at an FBI gun range had nearly 10 times as much lead in their blood as is permitted under government safety regulations.

Stable but sensitive

However, chemists have struggled to find replacement chemicals with the right stability and sensitivity, says My Hang Huynh, the explosives expert at Los Alamos National Laboratory in New Mexico who engineered the green explosives.

Her team has developed primary explosives based on a chemical called nitrotetrazole. In fact, nitrotetrazole itself has been studied for the past few decades as a next-generation explosive. However, it only makes a good primary explosive when partnered with toxic perchlorate-based chemicals.

Huynh鈥檚 team overcame this by tweaking the distribution of charge on the nitrotetrazole molecule. Switching charge groups on the molecule also changed the substance鈥檚 overall properties, such as its sensitivity to ignition through physical contact or heat. This could allow the substance to be tailored for specific applications, says Huynh.

However, one potential stumbling block for the new class of chemicals is that they lose sensitivity when they get wet. This has been one of the major hurdles in the race for other potential primary explosives, says Thomas Klapotke at the University of Munich, Germany, who has also worked on developing greener explosives.

Keeping it wet

Huynh sees this effect as a benefit, however, since the chemical returns to its explosive state after drying out. This property can be exploited to make the manufacturing and storage processes safer.

Producing conventional lead-based primary explosives is so risky that the US and UK import the chemicals rather than produce them. However, Huynh鈥檚 chemicals, which are produced in solution, do not become active until they are carefully dried out.

In addition, since they do not degrade in their wet form, they can be safely stored indefinitely, she says.

Journal reference: Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0600827103

Researchers at IBM鈥檚 Thomas J. Watson Research Center used techniques similar to conventional chip-making technology to create field effect transistors along a carbon nanotube 鈥� one very large carbon molecule 鈥� that had been deposited onto a silicon wafer. Unlike shrunken conventional silicon circuits, the resulting logic circuit yielded virtually no electron flow impedance, meaning current flowed faster.

鈥淭his isn鈥檛 about making the circuits smaller, it鈥檚 about making them faster,鈥� said Joerg Appenzeller, one of the circuit鈥檚 developers. 鈥淣anotubes fit the characteristics we need to advance high-end processing.鈥�

The components of today鈥檚 computer chips are made by doping tracts of a silicon substrate with metals of different electronic properties. While this technique was the breakthrough technology behind the integrated circuit, it becomes increasingly problematic in the race for smaller and smaller components.

Bad vibrations

Moore鈥檚 Law, coined in 1965, predicted that with the speed of technological development, the number of transistors in a chip and therefore a chip鈥檚 speed would double roughly every 18 months.

The problem is that as electrical paths shrink, electrical resistance increases proportionally. Also, the process of doping 鈥� adding impurities to the silicon to alter its electrical properties 鈥� means that the impurities left behind scatter electron flow, which becomes more of a problem at smaller scales.

The major reason behind the resistance, however, is an odd phenomenon known as plasmonic resonance, in which an electron鈥檚 path is hindered when it becomes coupled with vibrations in the surrounding lattice structure. But because the carbon nanotube is a single molecule with electrons passing along the tube, this problem is averted and resistance minimised, even at tiny scales.

Additionally, smaller silicon pathways make it easier for electrons to 鈥渏ump tract鈥� and leech into other nearby components. But in a nanotube circuit, this would be highly improbable as electrons would be carried down the molecular tract of the nanotube, Appenzeller explains.

Proof of principle

These properties will allow the manufacture of smaller transistors with electrons flowing faster through their wires, making for faster processing. The newly created circuit only operated at 52 megahertz 鈥� a pittance compared with the gigahertz speeds of modern silicon processors, but optimisation of transistor speed was not the team鈥檚 primary goal.

鈥淲e wanted to show the basic properties of the circuit,鈥� Appenzeller says, who adds they have 鈥渁 long way to go鈥� before thinking about processing speeds.

And development goes beyond simply optimising transistor sizes or design architecture. Current nanotube production methods are not yet able to produce tubes with the exact shapes or consistent sizes that would be needed to build even one chip, let alone mass manufacturing them.

鈥淚f we put a Manhattan Project type of effort into this, we could do it in five years,鈥� says Andrew Rinzler, the physicist at the University of Florida who made the IBM team鈥檚 tubes. 鈥淏ut, in reality, it鈥檚 going to take a little longer.鈥�

Journal reference: Science (DOI: 10.1126/science.1122797)

It twists and swims 鈥� and little else 鈥� but the first combination of two molecular machines is an important step on the long path to nanodevices sophisticated enough to, for example, perform repair functions within our cells.

鈥淭he next step is to integrate multiple molecular machines鈥� into much bigger devices, says Kazushi Kinbara, who developed the tiny contraption with colleagues at the University of Tokyo, Japan. 鈥淭hat project is now in progress.鈥�

The last decade of research has produced a wide array of nanoscale widgets 鈥� ranging from a 350-atom propeller to an elevator with a 2.5-nanometre rise. But virtually all have been a demonstration of principle, and of little or no real use in isolation.

鈥淭he motion of just one of these types of constructs is something that researchers spend years on,鈥� says Ross Kelly, who built a molecular motor in 1999 at Boston College. 鈥淛oining two moving pieces, and actually getting them to work together, is a considerable achievement.鈥�

Twisted prongs

The first part of the team鈥檚 molecular machine works a little like a pair of pliers (see diagram). But opening one end of the structure鈥檚 central X-shape does not widen the other end. Instead, the two prongs at that end twist around until they are 90掳 from their original position. This contortion is hinged on a pair of iron-based molecules that act as molecular ball bearings.

The opening and closing action is powered by exposure to ultraviolet and visible light. The UV light causes a pair of double-bonded nitrogen atoms strung between the two plier 鈥渉andles鈥� to kink, closing them. Exposure to visible light unkinks the bond, opening it up.

The second half of the machine is a pair of flipper-like pedals suspended between the prongs on the other side of the X. The twisting motion prompted by light exposure causes the pedals to flap, much like the flippers of a toy diver. The result is the first example of one molecular machine controllably driving the action of another, say the researchers.

Magnetism vs gravity

Both science and science fiction have long imagined that such tiny contraptions would one-day produce awe-inspiring results 鈥� whether as artery cleaning nanorobots or out-of-control producers of grey goo.

However, the mechanics of molecular machines is extraordinarily complex. It relies on the dynamics of chemical bonds and nanoscale forces, as apposed to the relatively straight-forward engineering principles at work in large-scale mechanical devices, like cars. Furthermore, magnetism becomes more important than gravity, and the strongest 鈥渨elding鈥� is a chemical bond that can be ripped open by nearby molecules.

But perhaps the biggest challenge is that the devices are not usually built one molecule at a time. Instead machines such as this new one are produced by a series of chemical reactions in solution that assemble billions of billions of units at a time.

Killer application

鈥淎fter you finally have finished the very difficult task of making a ball-and-stick model for a molecule that will perform a particular task, you face the even more difficult challenge of building it,鈥� said Josef Michl, a nanotechnologist at the University of Colorado.

However, it is a challenge that researchers are getting better yet each year. Kinbara expects his work will yield sophisticated molecular machines in as little as five years. Some of the first applications of complex molecular devices will probably be in microfluidics or very small-scale electrical systems.

鈥淲hat the final product will be 50 years from now, we don鈥檛 know,鈥� Michl says. 鈥淲e鈥檙e still at the very beginning. Ultimately, the killer application is going to be something we haven鈥檛 even thought of yet.鈥�

Journal reference: Nature (DOI: 10.1038/nature046735)