<title>Wireless IDT microsensors for subsurface sensing</title>

Abstract

A sensor by definition should be non-intrusive and respond faithfully to the parameter that one is trying to measure. Ideally the sensor should be small so that it does not disturb the field it is trying to measure and permit implementation on new and existing systems without requiring redesign of the system. Power supply to activate the sensor and extract data from the sensor is often the Achilles heel in implementation. Surface Acoustic Wave (SAW) devices also called the IDT Microsensor fit the bill ideally. They are in fact the first MEMS devices made, although this is not generally recognized. Unlike other MEMS devices, a SAW device has no moving parts. SAW devices can be mass-produced using semiconductor fabrication methods. The operation and use of Inter Digital Transducer (IDT) microsensor will be reviewed. Our major interest is that these sensors operate at RF frequencies and can hence be excited wirelessly using microstrip antennas from a remote source. Thus, one can achieve a passive sensor and retrieve the sensor data wirelessly. Whenever sensing is needed on a rapidly rotating system such as helicopter blades or automobile tires, in subsurface situations or inaccessible locations, a wireless passive sensor is the ideal solution. This talk will overview research on design and application of wireless IDT microsensors to dynamical strain monitoring, ice sensing, temperature and humidity sensing, liquid characterization and currently to tire pressure measurements.