• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.655-668
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• 2009

The principle and applications of quartz crystal sensors based on the three basic concepts for mass, viscosity, and viscoelastic changes are reviewed. In the general discussion the basic principle of quartz crystal and realization of a resonant frequency-resonant resistance diagram are described in detail. As examples of their applications, gas sensing with a carbon-coated quartz crystal, determination of the blood coagulation factor, an electrochemical analysis and crystallization analysis are reported. The possibility of developing new biosensors and chemical sensors is discussed on the basis of these results.

• Elastomers and Composites
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• v.43 no.3
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• pp.166-172
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• 2008

The resistance and frequency change of a quartz crystal microbalance during toluene absorption was measured for poly(vinyl acetate) (PVAc) with 268 nm thickness. Solubility of toluene in PVAc were measured at temperatures from 25$^{\circ}C$ to 42$^{\circ}C$ and pressures up to 28.4 torr. The frequency of a quartz crystal microbalance increased with increasing temperature and decreased with an increase in toluene vapor pressure. The resistance of a quartz crystal microbalance increased with increasing toluene vapor pressure and decreased with an increase in temperature. A greater pressure of toluene results in a greater solubility of the toluene into the PVAc film. The change of solubility was calculated by Sauerbrey equation.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.439-443
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• 2018

The outstanding characteristics of high quality GaN single crystal substrates make it possible to apply the manufacture of high brightness light emitting diodes and power devices. However, it is very difficult to obtain high quality GaN substrate because the process conditions are hard to control. In order to effectively control the formation of GaN polycrystals during the bulk GaN single crystal growth by the HVPE (hydride vapor phase epitaxy) method, a quartz ring was introduced in the edge of substrate. A variety of evaluating method such as high resolution X-ray diffraction, Raman spectroscopy and photoluminescence was used in order to measure the effectiveness of the quartz ring. A secondary ion mass spectroscopy was also used for evaluating the variations of impurity concentration in the resulting GaN single crystal. Through the detailed investigations, we could confirm that the introduction of a quartz ring during the GaN single crystal growth process using HVPE is a very effective strategy to obtain a high quality GaN single crystal.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.39-41
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• 1992

The characteristics of LB ultra-thin film multi-layers were evaluated by the AT-cut quartz crystal. Cholesterol and phosphatidyl choline LB multi-layers were deposited on the surface of quartz crystal by using vertical lifting method and horizontal lifting method. There was good relationship between deposition ratio and frequency shift, and the frequency was more stable at the case of horizontal lifting method to the vertical lifting method.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.8
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• pp.947-950
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• 1992

At-cut quartz crystal has been applied as chemical vapour sensors. The responses of quartz crystal at 9 MHz coated with phosphatidylglycerol(PG), phosphatidylinositol(PI), phosphatidylethanolamine(PE), phosphatidylserine(PS), and lipid A(LA) are determined for amyl acetate, acetoin, menthone and other organic gases which showed different affinities for each lipid. The identification of odorants depending on the species of lipid used for coating is discussed in terms of the normalized resonant frequency shift pattern.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.878-880
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• 1998

Quartz crystal in contact with viscoelastic medium is described directly in terms of the electrical equivalent circuit of the system. Stearic acid is used as viscoelastic medium and deposited on the surface of quartz crystal using the Langmuir-Blodgett(LB) method. Impedance properties of quartz crystal coated with LB films which were investigated and the possibility of applying the technique to chemical sensing introduced.

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.434-436
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• 2000

In this study, we investigate the optical characteristics of merocyanine dye Langmuir-Blodgett(LB) film using the oscillation characteristics of quartz crystal. As results, the resistance and frequency shift at the parallel resonance under the UV irradiation is to be going down. This behaviour of resistance and frequency is different from the case of general mass adsorption into the organic film on the quartz crystal. Generally the frequency decrease of quartz crystal oscillator, which has been considered as mass loading, goes along with the resistance increase. Thus it has been suggested that the J-aggregate dissociation in merocyanine dye LB film by UV irradiation give rise to transformation of oscillation characteristics of quartz crystal.

• KSBB Journal
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• v.13 no.4
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• pp.337-342
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• 1998

Immunosensor for the determination of LDL(Low-Density Lipoprotein), a good indicator for the diagnosis of atherosclerosis and hypercholesterolemia, was developed by using quartz crystal microbalance(QCM). The immunosensor consists of flow-through cell, oscillating circuit, oscilloscope, and frequency counter. FIA(Flow Injection Analysis) was applied to the QCM system for the measurement of LDL in liquid phase. Antibody showing binding affinity against LDL was immobilized on the gold electrode of a quartz crystal by covalent coupling via polyethylenimine / glutaredehyde. LDL was injected and bound to the antibody immobilized on the QCM immunosensor. The response of the immunosensor (F0 - F1) was found to be proportional to the LDL concentration from 200 $\mu\textrm{g}$/ml to 800 $\mu\textrm{g}$/ml. Operational conditions for the operation of immunosensor were also investigated in terms of sensitivity and non-specific binding.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.7
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• pp.487-496
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• 2008

Quartz crystal oscillator is frequently used in measuring a very small amount of mass attached to or adsorbed on the surface of an electrode on the quartz plate. The physical principle is that the resonance frequency of the shear vibration of the quartz caused by an applied electric field is a function of the mass. Recently, effort has been tried to measure physical properties of viscoelastic fluids, such as viscosity and shear modulus. This paper presents useful formula that can be used in estimating the properties of viscoelastic fluids. Important finding in this analysis is that the formula can produce multiple values for the physical properties of the viscoelastic materials.

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.05a
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• pp.94-94
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• 1998