Microsensors, microelectromechanical systems (MEMS), and electronics 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 has generated a great deal of interest in the chemical, mechanical, electrical engineering, medical, materials science, and food science communities in recent years. The term 'smart system' refers to a device or an array of devices that can sense changes in its environment and makes a useful or optimal response by changing its material properties, geometry, or mechanical or electromagnetic response. Both the sensor and actuator functions with 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 or chiral polymers to multifunctional polymers, carbon nanotubes, piezoelectrics, ferroelectrics, and other active ceramics. The miniaturization of sensors and subsequently that of the MEMS incorporating the sensors, actuators, and electronic circuitry for signal processing and control feedback have been made possible by advances in technologies originating in the semiconductor industry, and the emerging field has grown rapidly during the past ten years. Recently, microstereolithography has revolutionized the MEMS industry through multifunctional polymeric materials incorporating organic thin-film transistors with three-dimensional MEMS which is not 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 paper focuses on the design and fabrication of MEMS devices and their use in engineering and medical applications. Examples include: (1) accelerometers and gyroscopes for automobiles, inertial navigation, 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) health monitoring of structures; and (6) a 'smart tongue and electronic nose'.

Structural Health Monitoring for Composite Materials

“…The new sensors are so thin and flexible that they can be easily surface-mounted or embeded between layers, offering the potential for on-line and continuous monitoring. [18] (a) (b)…”

“…MEMS is an intelligent system which can sense the circumstances and do some reactions by the microcircuit control [18]. At present, many MEMS sensors, such as MEMS accelerometers and pressure sensors, can be purchased commercially.…”

A radio frequency controlled microvalve for biomedical applications

“…The selection of a propagation mode depends on the type of material and the intended application. Different crystal cuts can be used to generate a specific surface acoustic mode [11][12][13][14][15][16].…”

“…Where as Love waves have been found to be ideal for detection of ice formation, monitor the onset of crack formation and crack propagation. Moreover Rayleigh waves have been used for sensing deflection, strain, temperature humidity, pressure and acceleration [11,12].…”

Surface acoustic wave device based wireless passive microvalve for microfluidic applications

“…6,7 Importantly, it is a well known method to use a sandwich structure of semiconductor on a piezoelectric substrate to form a space-charge coupled SAW devices and SAW convolvers. 8 Based on the previous research work carried out by the authors, it was proven at the simulation level that a similar approach can be utilised in the design of a SAW based microactuator.…”