Surface transverse wave device

Tom-Moy, M., R.L. Baer, D. Spira-Solomon, and T.P. Doherty (1995). Atrazine measurements using surface transverse wave devices. Anal. Chem., 65 1510-1516. 

Tom-Moy, M. Baer, R.L. Spira-Solomon, D. Doherty, T.P. Atrazine Measurements Using Surface Transverse Wave Devices. Anal. Chem. 1995, 67, 1510-1516. 

To circumvent the limitations of these techniques, we have used a Surface Transverse Wave (STW) device as an on-line detector for liquid chromatography. The device can be derivatized to bind the target compound of interest. The sensing chemistry can consist of an antibody, antigen. Protein A or Protein G or any receptor or ligand capable of binding its complementary partner. One of the key features of the STW device is its ability to make a continuous measurement. In this report, we present the STW on-line detection system as an example of a reagentless detector which can make continuous measurements without the need for other separation steps. 

A new chemical sensor based on surface transverse device has been developed (99) (see Sensors). It resembles a surface acoustic wave sensor with the addition of a metal grating between the tranducer and a different crystal orientation. This sensor operates at 250 mH2 and is ideally suited to measurements of surface-attached mass under fluid immersion. By immohi1i2ing atra2ine to the surface of the sensor device, the detection of atra2ine in the range of 0.06 ppb to 10 ppm was demonstrated. 

Slip is not always a purely dissipative process, and some energy can be stored at the solid-liquid interface. In the case that storage and dissipation at the interface are independent processes, a two-parameter slip model can be used. This can occur for a surface oscillating in the shear direction. Such a situation involves bulk-mode acoustic wave devices operating in liquid, which is where our interest in hydrodynamic couphng effects stems from. This type of sensor, an example of which is the transverse-shear mode acoustic wave device, the oft-quoted quartz crystal microbalance (QCM), measures changes in acoustic properties, such as resonant frequency and dissipation, in response to perturbations at the surface-liquid interface of the device. 

Piezoelectric acoustic wave devices also respond to small changes in mass at surfaces immersed in (viscous) liquids [9]. The resonance frequency of AT-cut quartz resonators immersed in liquids depends on the liquid density and viscosity. The transverse shear wave which penetrates into the viscoelastic deposit and into the liquid is damped due to energy dissipation associated with the viscosity of the medium (film or liquid) at the acoustic frequencies. 

Acousto-ophc modulators control the transmission of light by local changes in the index of refrachon of the transmission medium. This modulahon or change occurs by means of a traveling sound wave that induces a stress-related modihcahon of the local index. The sound wave can be transverse copla-nar device), longitudinal colinear), or a combinahon of both as in the case of a surface acoustic wave (SAW). 

Device Type Wave Type Particle Displacement Relative to Wave Propagation Direction Transverse Component Displacement Relative to the Sensing Surface Media Plate Thickness Factors Determining Frequency3 Typical Frequency (MHz) Example ... 

In this device, a thin film or periodic grating on the surface of the crystal slows the wave and prevents radiation of energy into the interior of the crystal [84]. With proper choice of crystal orientation, a purely transverse particle motion at the surface can be obtained, permitting the sensor to operate successfully in liquids. 

FIGURE 3.48 (a) Operating principle of surface wave linear motor (transverse propagating wave exciting an elastic body) (b) a structural example of a surface wave rotational device. ... 

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