A8.1 - Merging the Ultrasonic and Microacoustic Sensor Principles

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
A8 - Ultrasonic Sensors III
R. Lucklum, M. Ke - Otto-von-Guericke-Universität Magdeburg (Germany), M. Zubtsov - Wuhan University (China)
181 - 186


Ultrasonic sensors and acoustic (resonant) microsensors are well accepted devices in many application fields. Both principles are based on acoustic wave propagation where the value of interest perturbs wave propagation in a distinct manner. The sensing capabilities of resonant microsensors result from the high Q-factor of the resonator and precise determination of the resonant frequency. Similarly, the time of flight of an ultrasonic burst traveling through the object of interest can be determined with high accuracy. Both principles face however, severe limitation in size and integration into microsystems.
We will show that acoustic band gap materials, socalled phononic crystals, provide a new platform for sensing material properties in small cavities. The sensor employs specific transmission windows within the band gap to determine properties of a component that builds the phononic crystal. When applied as sensor, the material of interest constitutes one component of the phononic crystal, e.g., a fluid in the holes of a solid plate. If the value of interest, e.g. the concentration of a contaminant in a liquid mixture, changes its acoustic properties, the acoustic properties of the phononic crystal will also change. Transmission or reflection coefficients are appropriate parameters for measurement and used to localize a characteristic feature of the phononic crystal. For a sensor application, a transmission peak within the band gap or a transmission dip outside the band gap is the most favorable measure. The transmission peaks can be considered as being based on resonance-like
effects, their examination combines basic features of ultrasonic and acoustic sensors.
Experimental proof-of-principle has been performed with water-alcohol mixtures. A resolution similar to the classical sensors has been achived.