Detection piezoelectric-excited

Campbell, G. A., Uknalis, J., Tu, S.-I., Mutharasan, R. Detection of Escherichia coli 0157 H7 in ground beef samples using piezoelectric excited millimeter-sized cantilever (PEMC) sensors. Biosensors and Bioelectronics 2007,22 (7), 1296-1302... 

Campbell, G.A., Medina, M. B., Mutharasan, 1C Detection of Staphylococcus enterotoxin B at picogram levels using piezoelectric-excited millimeter-sized cantilever sensors. Sensors and Actuators B Chemical 2007, 126 (2), 354-360... 

Rijal,K., Mutharasan,R. Piezoelectric-excited millimeter-sized cantilever sensors detect density differences of a few micrograms/mL in liquid medium. Sensors and Actuators B Chemical2007, 121 (1), 237-244... 

As the magnitude of an apphed electric field applied to a piezoelectric material is increased, the amphtude of oscillation increases and there is increasing acceleration of analytes adhered to the surface. This in turn results in an increasing force exerted by the surface on the analytes, which ultimately causes rupture of the bonds attaching the analytes to the surface (Fig. 9). Due to its piezoelectric properties the quartz crystal can be used to detect the excitation of vibrations in the substrate produced by bond rupture, which are converted into an electrical signal. The signal indicates not only the pres-... 

Piezoelectric-excited Millimeter-sized Cantilever (PEMC) Sensors for Detecting Bioterrorism Agents... 

Using the same PAbs an optical biosensor system has been developed for 2,4,6-TCP [224]. The principle is the detection of laser-induced fluorescence (LIF) in single microdroplets by a homogeneous quenching fluorescence immunoassay (QFIA). The competitive immunoassay occurs in microdroplets (d=58.4 mm) produced by a piezoelectric generator system. A continuous Ar ion laser (488 nm) excites the fluorescent tracer and its fluorescence is detected by a spectrometer attached to a cooled, charge-coupled device (CCD) camera... 

In the previous section we considered the conditions under which mechanical resonances would occur in a TSM resonator. In considering only the mechanical properties of the crystal, however, we neglected consideration of how these resonances would actually be excited or detected. The device uses a piezoelectric substrate material in which the electric field generated between electrodes couples to mechanical displacement. This allows electrical excitation and detection of mechanical resonances. In constructing a practical sensor, changes in resonant frequency of the device are measured electrically. The electrical characteristics of the resonator can be described in terms of an equivalent-circuit model that describes the impedance (ratio of applied voltage to current) or admittance (reciprocal of impedance) over a range of frequencies near resonance. 

The discovery by R. M. White of the University of California at Berkeley that surface acoustic waves could be excited and detected by lithographically patterned interdigital electrodes on the surface of piezoelectric crystals [42] has led to widespread use of SAW devices in a number of signal-processing applications. These include frequency filters, resonators, delay lines, convolvers, and correlators [43,44]. 

While a thin transduction layer below and/or above the input and output transducers must be piezoelectric, there is no such restriction upon the balance of the substrate. A piezoelectric thin film (such as crystallographically oriented polycrystalline ZnO or AIN) can be deposited on a non-piezoelectric substrate to provide a medium for AW excitation and detection. Thus, (non-piezoelectric) silicon wafers often serve as the substrate for SAW or FPW devices, with piezoelectric transduction provided by a layer of ZnO. Note also that this transduction layer need not extend laterally past the regions in which the IDTs are defined. 

The excitation and detection of surface acoustic waves, flexural plate waves, and other plate waves on piezoelectric substrates is most readily accomplished by use of an interdigital transducer (IDT) first reported by White and Voltmer [6]. The comb-like structure of the IDT, illustrated in Figure 6.4, is typically made from a lithographically patterned thin film that has been deposited onto the surface of a piezoelectric substrate or thin film. The metal film used to make the IDT must be thick enough to offer low electrical resistance and thin enough so that it does not present an excessive mechanical load to the AW. Typical IDTs are made... 

Resonant US in liquids. Measurements of ultrasonic resonance in liquids involve using a resonator cell comprising two major elements, namely a resonator chamber, where acoustic resonance forms and two transducers (usually piezoelectric), which excite and detect ultrasonic vibrations. 

The excitation can be realized by electrostatic, electromagnetic, or piezoelectric methods. The detection is carried out by capacitive, piezoelectric, or piezoresistive techniques. The principle of vibrating gyroscopes can be traced back to Foucault s pendulum in 1851. There are numerous design possibilities for the construction of vibrating gyroscopes [1-5, 9] Fig. 7.2.1 shows one principle. 

Fig. 7.2.6 Functional principle of a silicon micromachined tuning fork, the tines are excited by piezoelectric actuators, the Coriolis forces bend the suspensions and are detected by piezoresistive resistors in the suspension bars. Source Conti Temic, Produktlinie Sensorsysteme...

The viscosity sensor uses a microacoustic sensor device [11], in which the piezoelectric effect in a crystal is used to excite (and detect) acoustic vibrations. For microacoustic liquid sensing, special wavetypes are used in order to avoid unwanted radiation losses due to the excitation of compressional waves in the liquid. This... 

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