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13 March 2010 | NewScientist | 19 For daily technology stories, visit www.NewScientist.com/technology CALL it the yoga polymer: Nafion, a material used in some fuel cells, has an unrivalled memory for contortions. Tao Xie at General Motors in Warren, Michigan, has twisted and stretched a Nafion strip into three distinct shapes, and found that it will revert to each shape at the appropriate temperature. Nafion becomes softer as it is heated. At 140 °C Xie stretched it into a particular shape, which was locked in the polymer’s “memory” as it cooled to 107 °C and stiffened. Stretching and cooling it twice more allowed two other shapes to be memorised, so that when heated to the appropriate temperature the Nafion formed the corresponding shape (Nature, DOI: 10.1038/nature08863). Previously the best shape- memory polymers were able to remember only two shapes. Become a data network FIRST we sent data through wires, then the air, now the human body is becoming a communications conduit. Researchers in South Korea have transmitted data at a rate of 10 megabits per second through a person’s arm, between two electrodes placed on their skin 30 centimetres apart (Journal of Micromechanics and Microengineering, DOI: 10.1088/0960-1317/20/2/025032). The thin, flexible electrodes use significantly less energy than a wireless link like Bluetooth. That’s because low-frequency electromagnetic waves pass through skin with little attenuation, a route that also shelters them from outside interference. The film-like electrodes are made with a silicon-rich polymer that is safe to be worn for long periods and also makes for a good connection. Rather than wiring people directly BERND VOGEL/CORBIS TECHNOLOGY Shape-shifter warms to its task to the internet, the team see health benefits for their technology. It is difficult to monitor vital signs, such as blood sugar and electrical activity of the heart, in a person going about their everyday lives because it means either covering them in snaking wires connected to a recording device, or using wireless transmission. “If we use wireless for each of these vital signs we would need many batteries,” says study co-author Sang-Hoon Lee of Korea University in Seoul. A network transmitting through the skin would cut energy needs by roughly 90 per cent, he says. WHICH conducts heat better, polyethylene or iron? The answer depends on how much you stretch the plastic. Polyethylene normally acts as a thermal insulator: it transmits just 0.35 watts per kelvin per metre. But previous studies have shown that its heat- conducting abilities can be increased by stretching it, creating long, straight polymer chains that heat can travel along more easily. So Gang Chen at the Massachusetts Institute of Technology and his team set out to see how much heat they Stretchy plastic conducts like iron could make polyethylene conduct. They first made a gel by dissolving samples of the plastic in an industrial solvent at 145 °C, and quenching the mix in water. The gel was then heated to 120 °C so that long threads could be drawn from it. Once dried, the threads were stretched, resulting in strings several centimetres long but just tens of nanometres thick. These were found to have a thermal conductivity of 104 watts per kelvin per metre – better than pure iron, which conducts 80 watts per kelvin per metre (Nature Nanotechnology, DOI: 10.1038/nnano.2010.27). Heat-conducting plastics “could be used in automobiles to make lightweight radiators”, says Chen. Skin signalspirated downloads of The Hurt Locker via BitTorrent before the movie won six Oscars, according to TorrentFreak.com 7.9m The Falcon 9 rocket, developed by private firm SpaceX, could play a critical role in the future of the US space programme, but company founder Elon Musk isn’t banking on its maiden launch being perfect ( Los Angeles Times, 8 March) “We do not need to be successful on the first flight” “A network transmitting through the skin would cut energy needs by roughly 90 per cent”

Shape shifting polymer makes a memorable mark

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Page 1: Shape shifting polymer makes a memorable mark

13 March 2010 | NewScientist | 19

For daily technology stories, visit www.NewScientist.com/technology

CALL it the yoga polymer: Nafion, a material used in some fuel cells, has an unrivalled memory for contortions.

Tao Xie at General Motors in Warren, Michigan, has twisted and stretched a Nafion strip into three distinct shapes, and found that it will revert to each shape at the appropriate temperature.

Nafion becomes softer as it is heated. At 140 °C Xie stretched it into a particular shape, which was locked in the polymer’s “memory” as it cooled to 107 °C and stiffened. Stretching and cooling it twice more allowed two other shapes to be memorised, so that when heated to the appropriate temperature the Nafion formed the corresponding shape (Nature, DOI: 10.1038/nature08863).

Previously the best shape-memory polymers were able to remember only two shapes.

Become a data networkFIRST we sent data through wires,

then the air, now the human body is

becoming a communications conduit.

Researchers in South Korea

have transmitted data at a rate of

10 megabits per second through a

person’s arm, between two electrodes

placed on their skin 30 centimetres

apart (Journal of Micromechanics

and Microengineering, DOI:

10.1088/0960-1317/20/2/025032 ).

The thin, flexible electrodes

use significantly less energy than

a wireless link like Bluetooth.

That’s because low-frequency

electromagnetic waves pass through

skin with little attenuation, a route

that also shelters them from outside

interference. The film-like electrodes

are made with a silicon-rich polymer

that is safe to be worn for long periods

and also makes for a good connection.

Rather than wiring people directly

BE

RN

D V

OG

EL

/CO

RB

IS

TECHNOLOGY

Shape-shifter warms to its task

to the internet, the team see health

benefits for their technology. It is

difficult to monitor vital signs, such

as blood sugar and electrical activity

of the heart, in a person going about

their everyday lives because it means

either covering them in snaking wires

connected to a recording device, or

using wireless transmission.

“If we use wireless for each of

these vital signs we would need

many batteries,” says study

co-author Sang-Hoon Lee of Korea

University in Seoul. A network

transmitting through the skin

would cut energy needs by roughly

90 per cent, he says.

WHICH conducts heat better, polyethylene or iron? The answer depends on how much you stretch the plastic.

Polyethylene normally acts as a thermal insulator: it transmits just 0.35 watts per kelvin per metre. But previous studies have shown that its heat-conducting abilities can be increased by stretching it, creating long, straight polymer chains that heat can travel along more easily. So Gang Chen at the Massachusetts Institute of Technology and his team set out to see how much heat they

Stretchy plastic conducts like iron

could make polyethylene conduct.They first made a gel by

dissolving samples of the plastic in an industrial solvent at 145 °C, and quenching the mix in water. The gel was then heated to 120 °C so that long threads could be drawn from it. Once dried, the threads were stretched, resulting in strings several centimetres long but just tens of nanometres thick. These were found to have a thermal conductivity of 104 watts per kelvin per metre – better than pure iron, which conducts 80 watts per kelvin per metre (Nature Nanotechnology, DOI: 10.1038/nnano.2010.27).

Heat-conducting plastics “could be used in automobiles to make lightweight radiators”, says Chen.

–Skin signals–

pirated downloads of The Hurt Locker via BitTorrent before the movie won six Oscars, according to TorrentFreak.com

7.9m

The Falcon 9 rocket, developed by private firm SpaceX, could play a critical role in the future of

the US space programme, but company founder Elon Musk isn’t banking on its maiden launch

being perfect ( Los Angeles Times, 8 March)

“We do not need to be successful on the first flight”

“A network transmitting through the skin would cut energy needs by roughly 90 per cent”