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Low-cost, in-liquid measuring system using a novel compact oscillation circuit and quartz-crystal microbalances (QCMs) as a versatile biosensor platform

  • Quartz-crystal microbalances (QCMs) are commercially available mass sensors which mainly consist of a quartz resonator that oscillates at a characteristic frequency, which shifts when mass changes due to surface binding of molecules. In addition to mass changes, the viscosity of gases or liquids in contact with the sensor also shifts the resonance but also influences the quality factor (Q-factor). Typical biosensor applications demand operation in liquid environments leading to viscous damping strongly lowering Q-factors. For obtaining reliable measurements in liquid environments, excellent resonator control and signal processing are essential but standard resonator circuits like the Pierce and Colpitts oscillator fail to establish stable resonances. Here we present a lowcost, compact and robust oscillator circuit comprising of state-of-the-art commercially available surface-mount technology components which stimulates the QCMs oscillation, while it also establishes a control loop regulating the applied voltage. Thereby an increased energy dissipation by strong viscous damping in liquid solutions can be compensated and oscillations are stabilized. The presented circuit is suitable to be used in compact biosensor systems using custom-made miniaturized QCMs in microfluidic environments. As a proof of concept we used this circuit in combination with a customized microfabricated QCM in a microfluidic environment to measure the concentration of C-reactive protein (CRP) in buffer (PBS) down to concentrations as low as 5 μgmL -1.

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Author:Stefan BeißnerGND, Jan-Wilhelm ThiesGND, Christopher Bechthold, Philipp Kuhn, Bettina Thürmann, Stefan Dübel, Andreas Dietzel
DOI original:https://doi.org/10.5194/jsss-6-341-2017
Parent Title (English):Journal of Sensors and Sensor Systems
Document Type:Article
Year of Completion:2017
Publishing Institution:Hochschule Hannover
Release Date:2019/06/04
GND Keyword:Quarz; Mikrowaage; Biosensor; Oszillatorschaltung
First Page:341
Last Page:350
Institutes:Fakultät I - Elektro- und Informationstechnik
DDC classes:620 Ingenieurwissenschaften und Maschinenbau
Licence (German):License LogoCreative Commons - Namensnennung 3.0