Research Initiation Awards: In-Situ Measurement of Interfacial Mass Changes with Chemically Milled At-cut Quartz Crystals

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Piezoelectric transducers have been exploited for their ability to detect minute interfacial mass changes. The quartz crystal microbalance (QCM), comprising a thin wafer of AT-cut quartz sandwiched between two metallic excitation electrodes, has been used extensively in this regard. The format of the QCM is particularly attractive since AT-cut quartz crystals are inexpensive, easily handled and can be configured so that one of the excitation electrodes can be used as a working electrode in a conventional electrochemical cell. Applications of the QCM have been somewhat limited, however, by low sensitivity compared to other transducers because of the rather low operating frequencies (.10 MHz) of the QCM. This program aims to remove this obstacle by investigating the use of high frequency (up to 100 MHz), miniature chemically milled AT-cut quartz crystals in mass detection, both in vapor and liquid media. The goals this project will be to demonstrate (1) the mass sensitivity of these crystals to metal deposition and adsorption of gaseous analytes into thin active films, (2) the viability and mass sensitivity of these devices in liquid media (3) detection of electrochemically induced mass changes, (4) the feasibility of various sensor configurations using these resonators and (5) the use of these crystals as viscosity sensors.