Materiales Y Sistemas Inteligentes

January 2008 Number 299

SMART MATERIALS AND SYSTEMS
‘Smart’ materials and systems sense and respond to their environment and have applications in areas as diverse as health, defence and packaging. The UK has a long track record of research in this area and the government has launched a number of initiatives to encourage exploitation of this research. This POSTnote gives an overview of currentresearch and potential applications. It also examines the factors driving smart materials research and those holding back their exploitation.
Smart materials sense changes in the environment around them and respond in a predictable manner. Some types of smart materials include: Piezoelectric - Applying a mechanical stress to these materials generates an electric current. Piezoelectricmicrophones transform changes in pressure caused by sound waves into an electrical signal. Shape memory - After deformation these materials can remember their original shape and return to it when heated. Applications include shape memory stents - tubes threaded into arteries that expand on heating to body temperature to allow increased blood flow. Thermochromic - These materials change colour in response tochanges in temperature. They have been used in bath plugs that change colour when the water is too hot. Photochromic - These materials change colour in response to changes in light conditions. Uses include security inks and dolls that ‘tan’ in the sun. Magnetorheological - These fluids become solid when placed in a magnetic field. They can be used to construct dampers that suppress vibrations.These can be fitted to buildings and bridges to suppress the damaging effects of, for example, high winds or earthquakes.

Box 1. Types of smart material

Background

The most commonly accepted definition is that smart materials and systems can sense and respond to the environment around them in a predictable and useful manner. For example, the ‘photochromic’ materials used in reactivespectacle lenses become darker in response to increased light. Smart materials arise from research in many different areas and there is a large overlap with nanotechnology. Some types of smart material are described in Box 1. Smart systems also sense their environment and respond, but are not constructed from a single material. They may incorporate smart materials, but can also be constructed usingtraditional technology. Pacemakers are a smart system designed to respond to an irregular heart rate with an electrical impulse that regulates it. The significance of smart materials and systems Smart materials and systems open up new possibilities, such as clothes that can interact with a mobile phone or structures that can repair themselves. They also allow existing technology to be improved. Using asmart material instead of conventional mechanisms to sense and respond, can simplify devices, reducing weight and the chance of failure.

The commercial importance of smart materials is beginning to be recognised. In 2003, smart materials were the subject of a report produced by the Foresight Materials Panel - a government funded project that brings experts together to provide technologicalvisions of the future.1 It predicted that “the key to 21st century competitive advantage will be the development of products with increasing levels of functionality. Smart materials will play a critical role in this development”. Some experts believe that adding functionality in this way offers the best opportunity for UK industry to compete with low priced imports.

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Smart materials research is of long standing but commercial exploitation has been slow. The Foresight report concluded that “smart materials technology provides an excellent opportunity for the UK. However, despite significant progress over the last five years, supported by various government programmes, it [the UK] remains relatively poorly positioned...