Issue 23

Frattura ed Integrità Strutturale, 23 (2013); Rivista Ufficiale del Gruppo Italiano Frattura

The Italian research on smart materials and MEMS

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ecent developments in the field of material science and semiconductor technologies are fostering the engineering use of smart materials and micro-electromechanical-systems (MEMS) for the production of intelligent products. The term smart material applies when a material can react in a useful, reliable, reproducible and usually reversible manner to some stimulus picked up from its environment. A really smart material will use its reaction to the external stimulus to initiate or actuate an active response, e.g. with an active control system. There are materials that are designed to change their colour at a particular temperature. They find uses in bath plugs that show when the bath water is too hot, or in children’s feeding spoons and coffee or tea mugs that testify chromatically the temperature of their content. Other examples include water mixers incorporating self-energized shape memory springs to ensure a constant flow temperature despite fluctuating supply temperatures and pressures due to water being used elsewhere in the home. Besides these examples, the class of smart materials and applications is very large and rapidly growing, especially thanks to the steady development of new formulations and manufacturing techniques. Micro electromechanical systems (MEMS) merge mechanical and electrical components and have feature sizes ranging from micrometers to millimetres. They are typically fabricated using methods borrowed from the industry of integrated circuits and they have the potential of providing significant cost advantages when fabricated in large batches. Their small size also makes it possible to integrate them into a wide range of systems. Feature sizes may be scaled down to the order of the wavelength of light, thus making them attractive for many optical applications. Microsensors (e.g., accelerometers for automobile crash detection and pressure sensors for biomedical applications) and microactuators (e.g., for moving arrays of micromirrors in projection systems) are examples of commercial applications of MEMS. A relatively new and very promising field of application involves the integration of smart materials within MEMS to produce adaptive systems on a microscale. Thermally-activated, single-piece microgrippers or smart microvalves based on magnetorheological fluids are just two instances of the many possibilities disclosed by this fruitful hybrid technology. Although the chemistry and the physics behind the development of most smart materials and MEMS are well established, there is a definite need for engineering tools to help the designer incorporate those materials into marketable industrial products. This Special Issue collects papers aimed at providing fundamental background and useful design methods to the readers approaching this stimulating area of research. The papers were presented at the seminar held in Scilla from May 31 to June 2, 2012, by the Smart Materials and MEMS working group of the Italian Association of Stress Analysis (AIAS). We wish to thank the Italian section of the ASME for their support and Ingg. L. Bruno, C. Maletta and E. Sgambiterra for their fruitful collaboration.

Eugenio Dragoni, Università di Modena e Reggio Emilia Franco Furgiuele, Università della Calabria Aurelio Somà, Politecnico di Torino

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