Clean jeans: wash away pollution

Ingenious: a laundry additive could help to destroy nitrogen oxides

An unusual collaboration between chemists and fashion experts has produced pollution-busting clothes, which clean up urban air as people walk around.

Tony Ryan, chemistry professor at Sheffield University, and Helen Storey of the London College of Fashion, lead the Catalytic Clothing partnership. They’ve produced prototype jeans in which the denim is laden with nanoparticles of titanium dioxide or titania, which catalyse the destruction of nitrogen oxides, the main cause of low-level urban pollution.

Catalytic Clothing has already been exhibited at science and fashion shows, with the particles sprayed on to the denim. The next step, in collaboration with Ecover, the green detergent manufacturer, will be to develop a laundry additive called CatClo that adds the titania in a domestic washing machine. This would bring the idea to a mass market where it could make a real difference to urban air quality. One person wearing clothes treated with CatClo could remove about 5g of nitrogen oxides a day. That’s about the same as the daily emissions of an average family car.

“If thousands of people used the additive, the result would be a significant improvement in air quality,” says Ryan. “In Sheffield, for instance, if everyone washed their clothes in the additive, there would be no pollution problem caused by nitrogen oxides at all.”

Clothes need only be washed once with CatClo, because the nanoparticles grip tightly on to fabric fibres without affecting the clothing’s look or feel. Although best suited to denim and other cottons, they also work with other materials.

'Red Planet' dress created by Professor Helen Storey MBE and Professor Tony Ryan OBE

When CatClo encounters nitrogen oxides, they end up as harmless nitrates, which are washed away when the material is next laundered. The reaction requires light; sunshine is best but ordinary daylight or artificial light is fine.

Titania nanoparticles are already used extensively in sunscreens where they protect the skin from ultraviolet solar radiation. Their pollution-busting photocatalysis has been incorporated in solid materials such as glass, paints, cements and paving stones. But the CatClo researchers believe it will have more impact in clothing.

“The technology is not new, but the application is,” says Storey, whose short film about CatClo has gone viral. “The feedback revealed a massive market for this product from potential consumers who understand the concept behind it.”

The additive could be on sale within two years, costing as little as 10 pence for a full washing load.

Catalytic Clothing: Field of Jeans will be at the Manchester Science Festival, October 25-November 4. The Red Planet dress is being exhibited at Meadowhall, Sheffield, throughout its October Fashion Month 2012,

Now you see them: vanishing electronics

Biodegradable is a term normally reserved for compost, paper and eco-friendly plastic bags, writes Denise Roland. But now scientists have found a way to make electronics that simply disappear when they’re no longer needed.

Not only does this mean greener gadgets with decomposing parts, but as the materials are also “biocompatible” – meaning they do no harm to the body – it opens the possibility of implanting electronics in patients without worrying about their removal.

An international team of researchers has developed electronics so thin that they dissolve completely on contact with just a few drops of water or bodily fluids. Yet the silicon nano-membranes supporting the components are substantial enough for sophisticated devices like minuscule digital cameras. And by running the electronics using induction coils – a wireless power supply – they can operate without being connected to an electricity source.

“From the earliest days of the electronics industry, a key goal has been to build devices that last forever,” says John Rogers of the University of Illinois who led the research. “But if you think about the opposite possibility – devices engineered to disappear in a controlled manner – then other, completely different kinds of application opportunities turn up.”

Uses for so-called “transient electronics” are many and varied, ranging from medical devices that function for only a few days to longer-lasting components of mobile phones.

Determining exactly when the device will dissolve is done by controlling the solubility of its silk casing. The thickness and structure of the coating can be programmed to fine-tune the lifespan of the device, from days to years.

“It’s a new concept, so there are lots of opportunities, many of which we probably have not even identified yet,” explains Professor Rogers. The research is published online in the journal Science.

When one quake leads to another

A map of seismic activity after an earthquake in the Indian Ocean

This year’s largest earthquake, a magnitude 8.6 event under the East Indian Ocean off Sumatra on April 11, caused little immediate damage, but it triggered other quakes around the world for the following week.

Analysis by US seismologists, published in Nature, shows the quake was extremely unusual. Most great earthquakes occur on the boundaries between tectonic plates, when one plate slips over another. This one was different, taking place within the Indo-Australian plate with a predominantly horizontal rather than a vertical movement.

The lateral movement was good news because it avoided the devastating tsunami often generated by great sub-sea quakes. But it also meant that the tremor generated more powerful waves through the Earth’s crust, triggering significant seismic activity for at least a week.

“Until now we seismologists have always said: ‘Don’t worry about distant earthquakes triggering local quakes,’” says Roland Burgmann, earth science and planetary professor at the University of California, Berkeley. “This study now says that, while it may only happen every few decades, it is a real possibility if the right kind of earthquake happens.

“We found a lot of big events around the world, including in Baja California, Indonesia and Japan that created significant local shaking,” he adds. “If those quakes had been in an urban area, it could potentially have been disastrous.”

Why coffee can be bittersweet

When you wake up and smell the coffee, actually tasting it can be a bitter disappointment, writes Ling Ge. Recent findings from neuroscience and psychology reveal why – and how complex tasting really is.

People often imagine that taste comes from the tongue. In fact, the tongue and associated receptors in the mouth detect only salty, sweet, sour, bitter, spicy and metallic sensations. Yet we also experience mint, vanilla, coffee, strawberry and myriad other flavours.

“Eighty per cent of what we think of as taste actually reaches us through smell,” says Barry Smith, co-director of the Centre for the Study of the Senses at the University of London.

There are two ways of smelling – “orthonasal” (the odour comes in through nostrils) and “retronasal” (it travels up the oral cavity inside the mouth to the olfactory bulb).

“The smell of freshly brewed coffee is absolutely wonderful. Aren’t you a little disappointed when you taste it? If you hold your nose, coffee is hot water with a bitter taste,” Smith says. This is because saliva strips off about 300 of the 631 airborne chemicals that combine to form coffee’s complex aroma, so you receive only half of it retronasally.

Taste is also influenced by the trigeminal nerve, which is responsible for sensation in the face, including the pain in the bridge of your nose if you have too much wasabi or mustard. The trigeminal nerve also makes chillies taste hot and peppermint cool, even though there is no difference in the temperature in the mouth.

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