Low-cost, in-liquid measuring system using a novel compact oscillation circuit and quartz-crystal microbalances (QCMs) as a versatile biosensor platform
Low-cost, in-liquid measuring system using a novel compact oscillation circuit and quartz-crystal microbalances (QCMs) as a versatile biosensor platform
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DOI：
10.5194/jsss-6-341-2017
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发表时间：
2017-10-09
影响因子：
1
通讯作者：
Dietzel, Andreas
中科院分区：
文献类型：
--
作者：
Beissner, Stefan;Thies, Jan-Wilhelm;Dietzel, Andreas
石英晶体微量天平（QCM）是商业上可获得的质量传感器，其主要由以特征频率振荡的石英谐振器组成，当质量由于分子的表面结合而变化时，该特征频率发生变化。除了质量变化之外，与传感器接触的气体或液体的粘度也会改变谐振，但也会影响品质因数（Q因数）。典型的生物传感器应用需要在液体环境中操作，导致粘性阻尼强烈降低Q因子。为了在液体环境中获得可靠的测量，出色的谐振器控制和信号处理是必不可少的，但标准的谐振器电路，如皮尔斯和科尔皮茨振荡器无法建立稳定的谐振。在这里，我们提出了一个低成本，紧凑和强大的振荡器电路，包括国家的最先进的市售表面贴装技术组件，刺激QCM振荡，同时它也建立了一个控制回路调节施加的电压。因此，可以补偿由液体溶液中的强粘性阻尼引起的增加的能量耗散，并且稳定振荡。所提出的电路适用于在微流体环境中使用定制的小型化QCM的紧凑型生物传感器系统。作为概念验证，我们在微流体环境中使用该电路与定制的微制造QCM组合来测量缓冲液（PBS）中的C-反应蛋白（CRP）的浓度，其浓度低至5 μ g mL（-1）。
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 mu g mL(-1).