scholarly journals Modelling of the response of acoustic piezoelectric resonators in biosensor applications – Part 1: The general theoretical analysis

2015 ◽  
Vol 4 (1) ◽  
pp. 137-142 ◽  
Author(s):  
M. V. Voinova
Keyword(s):  
Quartz Crystal ◽  
Adsorbed Layer ◽  
Biological Materials ◽  
Liquid Media ◽  
Surface Mass ◽  
Piezoelectric Resonators ◽  
Saw Devices ◽  
Viscous Losses ◽  
Environmental Biosensor ◽  
Analytical Tools

Abstract. Acoustic piezoelectric resonators are widely used as precise analytical chemistry tools for the real-time monitoring of a negligibly small amount of surface-attached mass of biological components, in particular, in environmental biosensor measurements. The surface acoustic wave (SAW)-based sensors and the quartz crystal microbalance (QCM) compared in our work belong to the leading group due to their considerable advantages. These piezoelectric resonators are considered now as high-resolution analytical tools allowing researchers to discriminate between components due to the selective polymer coating on the resonator surface. The gravimetrical measurements performed with the SAW-based or QCM sensors provide the experimental data with high precision for the detection of surface mass for the thin adsorbed layer rigidly attached to the oscillator surface. The new challenge is the analysis of soft and biological materials, where the viscous losses of energy can essentially influence measured characteristics. Modelling is the important part of the analysis allowing researchers to quantify the results of the experiments. The present work provides a general theory of SH-SAW devices probing soft and biological materials. The results are compared with QCM-D operated in liquid media.

scholarly journals Characterizing Vibrating Cantilevers for Liquid Viscosity and Density Sensing

2008 ◽  
Vol 2008 ◽  
pp. 1-9 ◽  
Author(s):  
Christian Riesch ◽  
Erwin K. Reichel ◽  
Franz Keplinger ◽  
Bernhard Jakoby
Keyword(s):  
Cross Sections ◽  
Quartz Crystal ◽  
Model Parameters ◽  
Additional Mass ◽  
Liquid Loading ◽  
Fitting Procedure ◽  
Saw Devices ◽  
Quartz Crystal Resonators ◽  
Macroscopic Parameters ◽  
Online Process

Miniaturized liquid sensors are essential devices in online process or condition monitoring. In case of viscosity and density sensing, microacoustic sensors such as quartz crystal resonators or SAW devices have proved particularly useful. However, these devices basically measure a thin-film viscosity, which is often not comparable to the macroscopic parameters probed by conventional viscometers. Miniaturized cantilever-based devices are interesting alternatives for such applications, but here the interaction between the liquid and the oscillating beam is more involved. In our contribution, we describe a measurement setup, which allows the investigation of this interaction for different beam cross-sections. We present an analytical model based on an approximation of the immersed cantilever as an oscillating sphere comprising the effective mass and the intrinsic damping of the cantilever and additional mass and damping due to the liquid loading. The model parameters are obtained from measurements with well-known sample liquids by a curve fitting procedure. Finally, we present the measurement of viscosity and density of an unknown sample liquid, demonstrating the feasibility of the model.

scholarly journals Design of a Dual-Technology Fusion Sensor Chip with a Ring Electrode for Biosensing Application

Micromachines ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 153 ◽  
Author(s):  
Cheng Ma ◽  
Jin Zhu ◽  
Xiaolong Li ◽  
Wei Zheng
Keyword(s):  
Refractive Index ◽  
Gold Electrode ◽  
Quartz Crystal ◽  
Adsorbed Layer ◽  
Ring Electrode ◽  
Sensor Chip ◽  
Bottom Surface ◽  
Outer Diameter ◽  
Refractive Index Sensitivity ◽  
Index Sensitivity

Quartz crystal microbalance (QCM) is still a new high-precision surface detection technique. However, the adsorption quality detected by the QCM currently contains a solvent-coupling quality and cannot separate the actual biomolecular mass. Local surface plasmon resonance (LSPR) can detect the mass of biomolecules, but requires a certain contrast between the solvent of the surrounding medium and the refractive index of the adsorbed layer. The sensor chip, combining two compatible technologies, can realize the simultaneous detection of biomolecules and improve the refractive index sensitivity. The structure of our chip is to prepare the ring-shaped gold electrode on the upper surface of the quartz crystal, the circular gold electrode on the bottom surface, and the spherical gold nanoparticles arrays in the center region of the ring electrode to form a QCM/LSPR dual-technology chip. Through simulation, we finally get the size of the best energy trap by the two electrodes on the upper surface and the lower surface: the ring-top electrode with a thickness of 100 nm, an inner diameter of 4 mm, and an outer diameter of 8 mm; and the bottom electrode with a thickness of 100 nm and a radius of 6 mm. By comparing the refractive index sensitivity, we chose a spherical gold nanoparticle with a radius of 30 nm and a refractive sensitivity of 61.34 nm/RIU to design the LSPR sensor chip.

Quartz crystal microbalance based on torsional piezoelectric resonators

2007 ◽  
Vol 78 (7) ◽  
pp. 074903 ◽  
Author(s):  
W. Bücking ◽  
B. Du ◽  
A. Turshatov ◽  
A. M. König ◽  
I. Reviakine ◽  
...  
Keyword(s):  
Quartz Crystal Microbalance ◽  
Quartz Crystal ◽  
Piezoelectric Resonators

Electrochemistry of Dopamine β-Hydroxylase in Adsorbed State at a Gold Electrode

2004 ◽  
Vol 69 (4) ◽  
pp. 759-775 ◽  
Author(s):  
Ana Ion ◽  
Torbjørn Ljones ◽  
Florinel G. Banica
Keyword(s):  
Gold Electrode ◽  
Quartz Crystal ◽  
Adsorbed Layer ◽  
Open Circuit ◽  
Transfer Reactions ◽  
Potential Range ◽  
Adsorbed State ◽  
Cathodic Potential ◽  
Potential Region ◽  
Charge Transfer Reactions

Dopamine β-hydroxylase (DBH) adsorbed on gold electrode was investigated by electrochemical and quartz crystal microbalance methods. It was found that DBH can adsorb irreversibly on a gold electrode under open circuit conditions. In a neutral phosphate buffer, the adsorbed layer is stable to desorption within the potential range of 0.6 to -0.7 V vs Ag|AgCl (1 M KCl) electrode. At potentials positive than 0.8 V, adsorbed DBH undergoes an electrochemical oxidation involving probably tyrosine, tryptophan and histidine residues. This process is accompanied by DBH desorption and gold oxidation. In the cathodic potential region, from -0.2 to -0.7 V, DBH exhibits two reductions assigned to disulfide groups. No charge transfer reactions involving the copper centres in DBH have been noticed. However, DBH can bind reversibly copper(II) ions, which are not involved in the enzymatic activity and their presence was proved by voltammetry. The compactness of the adsorbed film was checked by cyclic voltammetry of selected redox probes at the DBH-coated electrode.

New Design for a Differentially Pumped Hydration Chamber for a Siemens IA

1971 ◽  
Vol 29 ◽  
pp. 44-45
Author(s):  
R. C. Moretz ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Electron Microscopy ◽  
Water Vapor ◽  
Electron Diffraction ◽  
Water Vapor Pressure ◽  
Biological Materials ◽  
Thin Membrane ◽  
Reliable System ◽  
System A ◽  
Water Films ◽  
Aperture Opening

Electron microscopy and diffraction of biological materials in the hydrated state requires the construction of a chamber in which the water vapor pressure can be maintained at saturation for a given specimen temperature, while minimally affecting the normal vacuum of the remainder of the microscope column. Initial studies with chambers closed by thin membrane windows showed that at the film thicknesses required for electron diffraction at 100 KV the window failure rate was too high to give a reliable system. A single stage, differentially pumped specimen hydration chamber was constructed, consisting of two apertures (70-100μ), which eliminated the necessity of thin membrane windows. This system was used to obtain electron diffraction and electron microscopy of water droplets and thin water films. However, a period of dehydration occurred during initial pumping of the microscope column. Although rehydration occurred within five minutes, biological materials were irreversibly damaged. Another limitation of this system was that the specimen grid was clamped between the apertures, thus limiting the yield of view to the aperture opening.

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