NETWORK ANALYSIS METHOD APPLIED TO LIQUID-PHASE ACOUSTIC-WAVE SENSORS

The network analysis method was used to completely characterize 5- and 9-MHz bulk acoustic wave quartz crystal sensors with aluminum and gold electrodes in the liquid phase for all conditions of the crystals. The behavior of the sensors Is evaluated in terms of the series resonant frequency, frequency of maximum phase, minimum impedance, motional resistance, maximum phase, and slope of phase. The difference in resonant frequency In liquid relative to air for crystals with gold and aluminum electrodes strongly implies that the electrode-liquid interface plays a significant role in acoustic wave propagation into the liquid. Previous theories associated with liquid-phase sensor behavior based on the Sauerbrey expression fall to explain experimental measurements of series resonant frequency as a function of viscosity. © 1990, American Chemical Society. All rights reserved.