UC Riverside

We present an experimental study of mass sensitivity for a Surface Acoustic Wave (SAW) sensor. Chemical SAW sensors have been developed to detect the mass variation of the mass adsorbed into sensing film by showing resonant frequency shifts. Previous experimental results have focused on the static sensitivity of theoretical SAW sensors assuming that the film thickness is negligible compared to the central wavelength of surface waves. Most current research is focused on dynamic experimental measurement and analytical techniques that are application specific. We have studied a SAW sensor with relatively thick isotropic film layers sputtered on as a static measurement comparison. The results can be used in a detection algorithm to quantify mass on the SAW sensor. Our results show a set of nodal response wave form changes and frequency shifts due to a continuous mass distribution. The development of the static experimental technique was completed with duplicate SAW tests. The duplicate SAWs had 12 measurements with 10 independently sputtered layers of 100 fÝm SiO2, hermitically sealed, and hermitical seal removed using a HP8510A network analyzer. In addition, our results show worst case total error of 0.1% between replicates. Further testing and modeling is required to correlate macro to micro scales for quantifying mass detection with SAW sensors. This research discusses the issues of utilizing a SAW sensor that could be readily integrated into cell phones for distributed sensing as being requested by Homeland Security.