QCM based sensor for detecting volumetric properties of liquids

• Published in: Current applied physics 2019, 19(6), , pp.679-682
• Main Authors: Mukhin, Nikolay, Lucklum, Ralf
• Format: Article
• Language: English
• Subjects: Acoustic metamaterials; Quartz crystal microbalance; Weakly coupled resonators; 물리학
• ISSN: 1567-1739; 1878-1675
• DOI: 10.1016/j.cap.2019.03.017

We introduce a microacoustic sensor, which combines the quartz crystal microbalance, a liquid-filled cavity and an intermediate artificial layer with effective acoustic properties. Each of the three components fulfils a specific task. The quartz vibrates in its thickness shear mode and acts as source and detector of shear waves, which penetrate the intermediate artificial layer and excite a resonance in the liquid-filled cavity. Both the piezoelectric transducer and the liquid-filled cavity are high-Q resonators with well-adjusted resonance frequencies very close to each other. The intermediate artificial layer couples the two resonators in a distinct manner via control of the propagation of acoustic waves between the quartz crystal and the liquid-filled cavity layer. The origin of the sensor signal is a change of the resonance frequency of the liquid-filled cavity caused by variations of acoustic properties of the liquid analyte inside the cavity, first of all speed of sound. This resonance appears as second resonance peak in the admittance spectrum of the quartz crystal. •High accuracy speed of sound measurement with quartz crystal microbalance•Changes in volume properties of liquid cause a shift in the resonance frequency•Liquid resonance appears as second peak in the admittance spectrum•Optimal coupling between quartz crystal and liquid resonators required•Intermediate artificial layer couples the two resonators in a predefined manner