Abstract
When the quartz crystal microbalance (QCM) is used in liquid for adsorption or desorption monitoring based bio- or chemical sensing applications, the frequency shift is not only determined by the surface mass change, but also by the change of liquid characteristics, such as density and viscosity, which are greatly affected by the liquid environmental temperature. A monolithic dual-channel QCM is designed and fabricated by arranging two QCM resonators on one single chip for cancelling the fluctuation induced by environmental factors. In actual applications, one QCM works as a specific sensor by modifying with functional membranes and the other acts as a reference, only measuring the liquid property. The dual-channel QCM is designed with an inverted-mesa structure, aiming to realize a high frequency miniaturized chip and suppress the frequency interference between the neighbored QCM resonators. The key problem of dual-channel QCMs is the interference between two channels, which is influenced by the distance of adjacent resonators. The diameter of the reference electrode has been designed into several values in order to find the optimal parameter. Experimental results demonstrated that the two QCMs could vibrate individually and the output frequency stability and drift can be greatly improved with the aid of the reference QCM.
Highlights
There has been a long history for quartz crystal microbalance (QCM) resonators to serve as a mass-frequency transducer, which vibrates in a thickness shear mode (TSM) mode
When a rigid film is attached onto the QCM surface, which equivalently corresponds to an increase of crystal thickness, the fundamental frequency will drop
We aim to develop a dual-channel high frequency QCM combined with the flow injection analysis technique
Summary
There has been a long history for quartz crystal microbalance (QCM) resonators to serve as a mass-frequency transducer, which vibrates in a thickness shear mode (TSM) mode. The QCM resonator is composed of an ATcut quartz crystal piece and two metal film electrodes coated onto double surfaces of the quartz crystal chip. The fundamental resonance frequency of the QCM resonator is dominated by the crystal thickness and determined by Equation (1). When a rigid film is attached onto the QCM surface, which equivalently corresponds to an increase of crystal thickness, the fundamental frequency will drop . The resonance frequency shift is governed (in a limited film thickness) by Equation (2) derived by Sauerbrey [5]: Sensors 2017, 17, 1136; doi:10.3390/s17051136 www.mdpi.com/journal/sensors
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