Microsensors, microelectromechanical systems (MEMS), andelectronics for smart structures and systems

Abstract

The technology referred to by the terms`microelectromechanical systems' (MEMS), `interdigital transducers'(IDTs), and `smart systems' is a multidisciplinary one which hasgenerated a great deal of interest in the chemical, mechanical,electrical engineering, medical, materials science, and food sciencecommunities in recent years. The term `smart system' refers to adevice or an array of devices that can sense changes in itsenvironment and makes a useful or optimal response by changing its material properties, geometry, or mechanical orelectromagnetic response. Both the sensor and actuator functionswith the appropriate feedback must be integrated, and comprise the`brain' of the material. The materials belonging to this category include a range of artificial materials, from optically active orchiral polymers to multifunctional polymers, carbon nanotubes,piezoelectrics, ferroelectrics, and other active ceramics. Theminiaturization of sensors and subsequently that of the MEMSincorporating the sensors, actuators, and electronic circuitry forsignal processing and control feedback have been made possible byadvances in technologies originating in the semiconductor industry,and the emerging field has grown rapidly during the past ten years.Recently, microstereolithography has revolutionized the MEMSindustry through multifunctional polymeric materials incorporatingorganic thin-film transistors with three-dimensional MEMS which isnot possible with silicon processing.The integration of MEMS, IDTs, and the required microelectronics and conformal antenna in the multifunctional smart materials and composites results in a smart wireless system suitable for sensing and control of a variety of functions in automobile, aerospace, marine, and civil structures, and the food and medical industries. This unique combination of technologies also results in novel conformal sensors that can be remotely accessed by an antenna system with the advantage of no power requirements at the sensor site.After giving a brief overview of microsensors and MEMS, the paperfocuses on the design and fabrication of MEMS devices and their use in engineering and medical applications. Examples include:(1) accelerometers and gyroscopes for automobiles, inertialnavigation, etc; (2) drag sensing and reduction for aircraft; (3)sensing and control of ice formation and de-icing for aircraft;(4) remote measurement of tip deflection for helicopters; (5) healthmonitoring of structures; and (6) a `smart tongue and electronicnose'.