EVER wondered where gadgets go when they die? For now, almost all of them are
unceremoniously laid to rest in landfill sites. But in Europe that鈥檚 about to
change. The European Commission will soon set in motion laws to regulate the
disposal of electrical and electronic goods. Discarded devices will, quite
literally, be sent to meet their maker. By 2006, manufacturers of everything
from TVs and computers to mobile phones and electric toothbrushes will have to
take back and recycle up to 90 per cent of their products, once their owners
have discarded them.
It鈥檚 a tough target. At the moment, recycling waste electrical and electronic
equipment, or WEEE, is expensive and laborious. Tumble dryers and other large
appliances, made mainly of ferrous metal, don鈥檛 present too much of a
challenge鈥攖hey can be shredded whole. It鈥檚 the smaller, more intricate
devices that are the headache, as they must be carefully dismantled by hand to
recover anything for reuse.
But it doesn鈥檛 have to be this way. Suppose instead that when their time
comes, these items dismantled themselves. This is precisely what a team of
researchers at Brunel University in Runnymede, Surrey, are hoping to make
possible. 鈥淲e thought it would be good if products `know鈥� what they have to do
at the end of their lives,鈥� says Eric Billett, professor of design at Brunel.
Billett and his colleagues Joe Chiodo and David Harrison have devised a way to
use smart materials to make discarded mobile phones or computers pop apart on
request. Their components鈥攃ircuit boards, screens, switches and the
like鈥攚ill sort themselves into separate piles. With this kind of organised
self-destruction, Billett hopes to transform recycling WEEE from a fiddly
nightmare into one painless stage in a product鈥檚 journey from cradle to
grave.
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It can鈥檛 happen too soon. WEEE is becoming a major problem. Over 6 million
tonnes of the stuff is dumped each year in the European Union
alone鈥攔oughly 4 per cent of all municipal waste. That may not sound like
much, but the volume of WEEE is growing at about three times the rate of other
garbage.
According to the Swedish telecommunications manufacturer Ericsson, there are
600 million mobile phones in use in the world today, and the number is expected
to hit 1 billion by 2002. And as mobile use spreads from the boardroom to the
playground, the next wave of must-have, multifunctional, multicoloured phones
will send older models straight into the garbage, along with last year鈥檚
trainers.
Computers are another hassle. Their average life expectancy has withered from
10 years back in the 1960s to around four in 1998. Many cutting-edge machines
now manage less than two years鈥� service.
It鈥檚 not just the quantity of WEEE, but also its make-up that鈥檚 worrying the
waste watchers. Electronics contain an intimate mixture of many materials. Some
of them are precious, such as gold. Some are hazardous, such as lead, mercury,
cadmium, halogenated compounds and arsenic. So WEEE can鈥檛 just be burnt, because
this releases toxic emissions such as heavy metals, dioxins and furans.
The mess is complicated by the fact that the recycling methods on offer today
are simply not an attractive option. The manual approach is expensive, with
around 80 per cent of the outlay arising from labour costs. While the cost of
recycling cars or washing machines, for example, is around 100 euros (about
拢60) per tonne, it costs six times that to recycle a tonne of electronic
games or radios. So more than 90 per cent of Europe鈥檚 WEEE currently ends up as
landfill.
Hence the approach at Brunel. If Billett and his team succeed in making
products that dismantle themselves on demand, it will be possible to reuse
valuable components and reclaim expensive or hazardous materials. They are
pinning their hopes on a technique called active disassembly using smart
materials (ADSM). It relies on the unusual properties of shape memory alloys
(SMAs) and shape memory polymers (SMPs). These materials undergo radical shape
changes when they are heated to a particular trigger temperature.
To start with, the only difference between conventional gadgets and their
ADSM counterparts will lie in the fasteners holding them together, such as
screws or brackets. The new fasteners will pop out when they are heated to the
preset temperature. Later, products can be designed from scratch with ADSM in
mind.
SMAs are well-established materials. They have been around for some 30 years,
and come in two main types: those based on copper-zinc-aluminium alloys, and
those made of the more expensive nickel-titanium alloys (see 鈥淢etal with memory鈥�).
The price of these alloys is dropping as they find more applications, from space
station connectors to spectacle frames and medical devices.
SMPs are relative newcomers that only became commercially available in the
late 1990s. Several companies now produce them, and the Brunel project is
working with a family of polyurethanes developed by Mitsubishi Heavy Industries
in Japan.
These polymers have some clear advantages over SMAs. For starters, they are
between 10 and 100 times cheaper. Billett and his colleagues are also able to
specify their critical temperature to within a few degrees. 鈥淭he trigger
temperature is usually between 100 and 200 掳C,鈥� says Billett. 鈥淚f the other
components in the product are going to be recycled, we need plastic fasteners
that give way reliably before the other plastics in the product begin to
驳辞.鈥�
SMAs have advantages too鈥攚hen they revert to their original shape, they
produce large forces that help push components apart. SMPs, however, produce no
force when they reach their trigger temperature (see 鈥淪hape-changing plastic鈥�).
鈥淧lastic fasteners might need to be supplemented by a spring,鈥� says
Billett, 鈥渂ut with the difference in cost between SMAs and SMPs, you鈥檇 have to
have a specific reason to use the metals.鈥�
The work at Brunel has drawn interest and money from many large electronics
manufacturers, in addition to research council funding. Most of the big guns,
including Motorola, Panasonic, Nokia, Kodak, Philips and Sony, have participated
in the trials. The team has fitted an array of equipment鈥攎obile phones,
cameras, games consoles, stereos and calculators鈥攚ith shape memory screws,
brackets, coils, rods and discs, that release or push the products apart as they
heat up. And overall the tests have been a success.
The manufacturers are now drawing up a set of conditions that their products
could reasonably be expected to withstand in normal operation. 鈥淗ow hard do you
shake your cellphone, and just how hot would your laptop get in the back of the
car in Greece?鈥� asks Billett. 鈥淲e obviously need to avoid premature disassembly.
But if you drop your tape recorder into a cup of tea, it鈥檚 reasonable to expect
it to be damaged. Under-bonnet car electronics, on the other hand, might be
expected to withstand boiling water if, say, there was a radiator leak.鈥�
Although it will be a long time before the fruits of the Brunel research
become industry standards, Billett believes the principle is now proven. 鈥淎DSM
is no longer technically in question,鈥� he says. 鈥淲e鈥檙e now looking at whether it
is commercially viable.鈥� To this end, the Spanish recyclers Gaiker Technology
Centre and Indumetal Recycling have been drafted in to build an EU-funded pilot
plant in Spain which will test the technique.
Gaiker and Indumetal aren鈥檛 revealing details of the project, but there are a
number of key issues that need to be looked at. For example, which form of
heating will be best? So far the researchers have been using hot water, but hot
air, infrared or even microwave heaters might prove more practical or
economic.
It may also be possible to arrange the disassembly process so that the
dismantling happens in stages, allowing the various components to be sorted,
rather than leaving you with a jumble of bits and pieces. For example, casings
might all be made to spring apart at one temperature, while the brackets holding
liquid crystal displays in place might release at a slightly higher temperature.
Then circuit boards could pop out, and so on.
Large-scale applications may be a long way off, but that doesn鈥檛 stop Chiodo
from picturing what an ADSM recycling plant might be like. The process begins at
one end of the building with a confusion of old TVs, stereos, phones and
computers piled up on the conveyor. As the belt carries the carcasses into an
oven, they reach their initial trigger temperature and begin to creak and pop.
First the casings spring apart and are cleared away by robotic arms. Next, the
larger subassemblies such as cathode ray tubes, LCDs, circuit boards and buttons
ease themselves free ready for sorting. Finally, the smaller components such as
integrated circuits come apart and are collected. The Brunel team envisages that
most of the sorting would be automatic. 鈥淭here are a variety of established
mechanical separation techniques that could be incorporated to separate the
different streams,鈥� says Chiodo.
While Europe is leading the way with laws to reinforce recycling, WEEE is a
worldwide problem. Billett believes the writing is on the wall for everyone:
鈥淛apanese, American and European legislation is broadly in step and most of the
manufacturers are international anyway.鈥�
Chiodo also envisages some light-hearted spin-offs. Manufacturers are bound
to take advantage of the consumer appeal afforded by these products. Fancy a
phone that is discreet and businesslike all week, but becomes jazzy and bright
for the weekend? Just pop it under the grill for a few seconds. Then on Sunday
night, another quick blast could sober it up ready for work on Monday
morning.
鈥淚 can鈥檛 see it being done any time soon,鈥� says Chiodo, 鈥渂ut there are
already materials available that undergo major changes in shape, volume and
colour when exposed to the right stimulus.鈥� Just make sure they鈥檙e not
overstimulated, or you could find yourself with a pile of plastic bits.
The shape memory effect in metals relies on a phase change in the material鈥檚
crystal structure. Below the trigger temperature, the alloy has a structure
called martensite. At higher temperatures, the structure switches to
austenite.
In the martensitic state, an SMA can be formed into any shape that鈥檚 needed,
such as a coil or bracket. But when heated to its trigger temperature, the
material will revert to the austenitic phase鈥攁nd its original shape. In
doing so, it can exert a force several times greater than that needed to deform
it in the first place. Materials exhibiting this sort of one-way effect can be
easily reshaped after they have cooled down and the phase change reverses.
Another class of SMA, called a two-way material, can flip automatically between
two specific shapes.
Eric Billett at Brunel University in Surrey knows these special plastics
inside out. 鈥淭he mechanism behind the shape memory effect in SMPs can be found
to some extent in most plastics,鈥� says Billett. 鈥淭he difference in this case is
that it has been optimised to be an asset.鈥�
Below the trigger temperature the SMP is in a brittle, glassy state, with its
long polymer chains tangled together and held in place by bonds between them. At
the trigger temperature, these intermolecular bonds break, and the material
becomes rubbery and elastic. Heat an SMP screw thread, for example, and it
becomes floppy, allowing the screw fixed through it to be pushed out of place by
a small spring. Cool the SMP and the bonds reform into their original
configuration, so the thread can be reused.