Smart materials have arrived in the curriculum. But what are they? Carolyn O'Grady finds out
Materials that change colour with temperature; granules that when put into warm water turn into a malleable substance and then become rock hard; starches that bind and thicken faster. No wonder smart materials are described by one teacher who uses them as "definitely having the Wow! factor" - they make students sit up and take notice. As do the very sophisticated "smart" products now on the market: computer keyboards that roll up; diving suits that cling in certain conditions and not others; clothes that contain medicines and ointments needed by the wearer. Soon we will have pockets that respond to the wearer's fingerprints to ward off pickpockets; collars that create "a cone of silence" round you for a peaceful walk in the middle of the city; and clothes programmed to take on the appearance of anything you desire. So what are smart materials?
In the national curriculum programmes of study and attainment targets for design and technology key stages 1-4 they are linked to modern materials, which are defined as being developed through the invention of new or improved processes, for example as a result of synthetic materials or ingredients, but not naturally occurring changes. The smartness of some materials lies in their ability to respond to differences in temperature or light and change in some way. They can sense conditions in their environment and react to them. Smart materials appear to "think" and some have a "memory" as they revert back to their original state. So, for example, it is possible to create a spoon for a baby that will, say, go red if the food or liquid on it is too hot. It will then revert back to its original colour. Some other examples include a shape memory alloy (one such is nitinol), which responds with mechanical movements when a set temperature is reached (for example to trigger a sprinkler system); or thermochromic dyes, used to produce clothing that changes colour with light or temperature, for example, to warn of possible hypothermia or excessive UV exposure, and modified starches, such as those which set at high temperature and then become fluid again at low temperature.
In 1999, when the national curriculum programmes of study for design and technology were published, it was not considered likely that teachers would be able to do much in the way of hands-on experiments. Hence the use of the words "should be taught about" rather than, say, "use" or "work with" in relation to a modern materials. Many of the materials were not freely available (and if they could be bought, were expensive) and teachers did not have the knowledge and experience to find or use them. Now that is changing. The materials are becoming available (see smart materials resources box) and teachers are getting to grips with what they might do with them.
The KS3 design and technology schemes of works (published last year) encourage them to teach about smart materials in a practical way through focused practical tasks. In Unit 9A on Selecting Materials, in the section on Food, for example, it is suggested that teachers "organise some practical investigations that enable the pupils to explore the uses of modern materialsingredients, for example to compare the use of modified starches to make a simple thickened sauce or mousse with traditional methods". There is, however, no expectation that pupils will use smart materials when they design and make a products of their own, though they should be aware that a manufacturer could use them if their products were made in high volume.
The Technology Enhancement Programme (TEP), funded by Gatsby Technical Education Projects, has long been encouraging the use of smart materials in education. Frank Muraca, TEP's national co-ordinator for materials and resources, estimates that about 30 per cent of teachers are now using them at KS4 and most sixth-formers are now exposed to them. "Expense is still a problem at KS3 and 4", he says. But cheaper products are being made available by organisations such as TEP and NADCAT. It is now possible for teachers to buy enough of the materials to not only demonstrate applications but also to allow pupils to use them.
Smart materials may have the Wow! factor, but sexiness can bring its own problems. It is very easy for pupils to get carried away and invent startling but, at the end of the day, gimmicky products. Louise Davies, principal officer for Damp;T at the Qualifications and Curriculum Authority, points out that in the Year 9 QCADepartment for Education and Skills Scheme of Work, pupils are encouraged to look critically at materials. She says: "There is an expectation that they will think about whether these modern and smart materials are appropriate, an improvement, and about the issues surrounding their use. For example, is technological development in this area a good idea? And for whom?"
So we can make clothes change colour, but we have to make sure that the application of this technological feat meets social, economic, environmental and ethical considerations. For example, change of colour might indicate that a child was getting too much exposure to harmful sun rays. Frank Muraca counsels against teaching smart materials in isolation. "Think smart materials when appropriate," he says. "Teachers should be informed and trained to know about them in order to suggest them as one solution to a design problem." But they do excite pupils. "They allow students to catch up with modern industrial practice and offer new products. Teachers really enjoy using them," he says.
Experiments and ideas
Food: introducing modified starches
Modified starches respond to differences in temperature - for example, they swell or thicken in hot water or when heated and return to a flow when cool. They are used in pizza toppings: the topping thickens when heated in the oven and so does not run off the base, but on slight cooling the topping becomes runny again. Modified starches are used in instant deserts, which thicken without heating but do not return to their original state.
Preparation the day before: Blend and cook four mixtures using cornflour, wheat flour, waxy maize starch and modified starch (use one tablespoon of each and 150ml water). Divide each mixture into two beakers, put one of each starch into the fridge and one into a freezer. Remember to label them.
On the day: Defrost the frozen starches. Then, once you have discussed starches in the context you want, do the practical demonstration in as dramatic way as possible - almost as if you were performing a magic trick. Tip out the cold cornflour and wheatflour first (they will have set into a gel), then try to tip out the waxy and modified starches (these will be soft). Use your fingers to show the pupils their texture and viscosity. Microwave all of them for one minute. Look at them again. Add lemon juice to the waxy maize starch mixture and the cornflour (they will go runnier). Then add it to the modified maize starch (the texture will not change). Discuss (you could bring in lemon meringue pie here). Now tip out all the defrosted starches and squeeze them with your hand. The wheatflour and cornflower will weep lots of water. The waxy and modified will not.
Adapted from the Get Smart! Starch Pack by Lesley Woods.
Resistant materials: introducing polymorphs Polymorph, a nylon-based thermoplastic, which comes in granular form (available fom TEP), shows very definite results and is an excellent way of introducing pupils to thermoplastics. When placed in moderately hot water (64 degrees Celsius), it "melts" to form a transparent homogenous material, rather like a modelling putty.
At this point you can mould and stretch it as much as you like. It then sets rock hard when cold - so hard, in fact, that you can use tools to drill it and saw it. If you reheat it, however, it goes soft again. It is fairly expensive (around pound;20 a kilo), but the fact that it goes soft again means that it can be recycled repeatedly. It can be used to make all sorts of objects: key fobs, a telephone case and individualised knife and fork handles which can be moulded by the user.
Textiles: introducing thermochromic pigments
Thermochromic materials change colour at specific temperatures. The battery test strip is a good example. If the battery is in good condition, the current flows through a printed resistor under the thermochromic film and heats it to cause a colour change.
The following experiment uses thermochromic pigments which can be painted on to surfaces. Use two polystyrene cups, one thick walled and the other thin walled, and paint a strip of colour down the sides of the two cups. Let the paint dry and then pour hot water in.
The colour change takes some time on the thick-walled cup, but would be pretty instantaneous on the thin-walled cup. As the water cools the paint strip returns to its original colour. Pupils could investigate how long it would take to register heat on different vessels and check how hot the water has to be.
The thermochromic pigments used in this experiment are available from TEP and the experiment is adapted from its Smart Colours leaflet.