SMART MATERIALS

SHAPE MEMORY ALLOYS:

• Shape memory alloys are metals that have been designed to work in a particular way in response to the stresses and strains placed on them. The most common is called 'nitonol': an alloy of nickel and titanium. Other shape alloys can contain a range of other materials such as iron, nickel, cobalt and titanium alloys in varying percentages.
• METAL ALLOYS SPECIFICALLY DEVELOPED TO REMEMBER THEIR SHAPE UNDER SPECIFIC CONDITIONS.
• Heat treatment gives the material a memory. For example, a nitonol wire heated by passing electrical current through it will reduce in length by about five percent. On releasing the current, the wire can be stretched back to its original length.
• Applications for shape memory alloys: 'Memoflex' glasses are an example of the use of shape memory alloys. These are nickel/titanium alloys that have the ability to regain their original shape at room temperature after being deformed. In this instance they re termed 'superelastic' alloys. Deformation of these materials can be complex, e.g forming a wire into a knot, while the material is capable of complete recovery. Shape memory alloys also have applications in bio-engineering. For example, a Stent tube can be collapsed when chilled and when it is inserted into the body it expands to let blood through it. Another example includes the plating of broken bones, as the plates reach body temperature they remember to contract, pulling the fracture together and applying a pressure to make the bones heal quicker.

THERMOCHROMIC PIGMENT (SMART COLOURS):

• Colour pigments that can change colour in response to heat. The pigments are typically combined with polymers as plastic products are moulded.
• The Russell Hobbs 2001 'Thermocolour' kettle changes from a cool blue colour when cold to a vibrant pink as it boils. In the market for high tech gadgets, this is clearly desirable and is a strong aesthetic feature used in branding and advertising for this product.
• The colour change is also quite a good safety feature, as we naturally associate bright colours with danger and heat. Also, if the kettle has been left to stand after boiling then the user can instantly see if the water is hot enough to make a drink from.
• Further applications include: thermometers; baby feeding products.
• THERMOCHROMIC FILM = a special type of liquid crystal which when heated will change colour. The introduction of these pigments in the form of an ink has led to the development of temperature testing strips used for medical and other applications.

PHOSPHORESCENT PIGMENT:

• Ceramic powders that have the ability to absorb light and then release the light energy over a long period of time. They can be mixed with acrylic paints/inks for creating illuminated signs that do not require an additional power source.