Anyone with a physics O-Level or GCSE knows that with most solid things, if you heat them, they will expand slightly. One exception to this law, not covered by school textbooks but widely known by eager schoolchildren, is empty crisp packets: lay one flat under a grill and it shrivels miraculously to a quarter of its normal size. This extreme reaction of a material to a controlled external stimulus was definitely, in late Seventies secondary-modern-speak, “smart”.
This, sadly, is not how smart materials got their name, although passing heat through compounds and seeing what happens is something smart materials researchers do a lot of. The “smart” label is thought to have first appeared after a Japanese scientist, who had developed some of the world’s first “intelligent” materials, consulted his Japanese/English dictionary for a translation of “intelligent”. It gave him “smart”, and the word stuck.
Smart materials do things; in the words of scientists, they have functionality. They function in response to doses of heat, electricity, pressure or other stimuli. They can be made to behave in a controlled, programmed way, changing their shape, colour or texture.
The responses of these compounds can be predicted, and therefore controlled, to within tiny tolerances, making them ideal for high-tech applications.
But some scientists are now bypassing the traditional trickle-down route (space-aerospace-cars-consumer products) taken by new materials in the past, and are finding uses for smart materials in the home. The likelihood is that, not long into the next century, smart materials will make the consumer products, furniture and equipment of today look as wooden and difficult to use as the everyday tools of 100 years ago look now.
Bedfordshire’s Cranfield University Smart Materials Group is investigating possible relationships between smart materials and people in the home and at work. “We have a special interest in domestic environments,” says Dr Cliff Friend, co-chair of the group, “simply because we believe very passionately that it’s here, where the human is in very immediate contact with the product, that there’s a very big human interface application for these adaptive materials. We’re looking at the domestic arena not as technology-driven, but as one that is pulled by design and the user.”
For 20 years, Friend has worked on high-tech applications for a group of materials called shape memory alloys (SMAs). Strands of these alloys deform in response to a given stimulus, and return to their original state when the stimulus is removed. Embedded in particular formations within structural materials, pre-shaped or “programmed” SMA strands can cause useful temporary deformations in structures, just as nerves instruct muscles to flex or relax. Electrical current can be passed through a network of programmed SMA in an aircraft wing, for example, and the heat causes the alloy strands to attempt to return to their under- formed state. This forces a small change in the shape of the wing, which stays until the current is switched off. The “brain” in this instance would be a computer inside the aircraft, sensing changes in aerodynamic conditions and controlling how the wing flexes to deal with them.
The smartest end of smart materials development is concentrating on self-sensing fibres, which can give warning of dangerous stresses in structures, or replace the type of complex “mechatronic” systems that control anti-lock braking in cars. But, as far as product design goes, it is the opposite end of the spectrum that occupies Friend. “We’re interested in more limited function. You heat an SMA and you get a shape change, and if you cool it right you get the reverse shape change; it’s very limited. For example, photochromic lenses in spectacles: light falls on them, they go dark, the light disappears, they go clear. But what’s interesting about those two applications is they’re locked into the material at the atomic/molecular level. And there is currently more scope in gaining only limited functionality, for example, in an appliance.”
In a bold step, Cranfield has taken on an industrial designer to speculate on how materials advances might offer a closer fit between user and product. Many of the concepts are being developed ahead of the material, but could conceivably be in production within five to ten years. There are no prototypes yet, only ideas based around pointers to the types of phenomena that could be introduced into materials.
Friend would like to see such materials break the stalemate between most household appliances and their human users. He shares with Philips the belief that users are weary of dumb, utilitarian machines around the house, and would like to feel more attachment to the products they buy. This way, some argue, products would be kept longer and replaced less often, which is good for the environment.
The Philips/Alessi range of kitchen appliances tried to develop this “humanware” theme of pet-like interaction between the user and product, but was received in the UK as a set of risible, retro, rich man’s Christmas presents. “We’re asking if we can go a stage further,” says Friend. “Would another function enhance this humanware characteristic? It might be based around how the product is held. You grab it hard, it is elastically resistant to you. Grab it more softly, and it gives more, but still recovers its shape once you take your hand off.”
Philips has expressed an interest in Cranfield’s work, and other synergies exist in the blending of skills from design and science to progress product development.
But if squidgy kettles smack more of gimmickry than of an indirect appeal to consumers to treasure their household appliances, there are a thousand more deserving targets for materials development. One example is the concept of seating for the disabled that minimises pressure sores by adapting its shape “intelligently”. This idea is being pursued by Friend’s group in partnership with Cranfield’s postgraduate medical school.
Designers are keen to experiment with smart materials, and no wonder. They offer undreamt-of scope in achieving the ultimate fit between humans and hardware.
Alex Tatic, a designer at Priestman Associates, believes, for example, that his sport of mountain biking could be transformed. Understanding the distribution of forces around a mountain bike frame and its rider in a variety of different conditions – off-road, on-road, uphill, downhill – Tatic can conceive of how a programmable material could extend the length of the frame by just an inch when required. This would significantly aid cycling downhill, in a crouched position, says Tatic. “There would be a real leap in design and performance.”
The cyclist’s helmet and knee pads, moulded from material that becomes more resilient under sudden impact and remains soft at other times, represent an appropriate use for the tactile sensitive material envisaged at Cranfield. Other ideas spring instantly to mind: laptop computers, portable medical equipment, luggage, prams – any products would benefit that need to resist hard knocks but reward human touch.
Smart materials can potentially improve human interaction with almost everything our bodies contact. Their development, as the Cranfield course acknowledges, should be led by design, and the needs of the end-user.