Quartz Crystal Microbalance Sensor

QCM consists mainly of quartz resonator, signal detection, oscillator and data processing.

Where, quartz resonator is the receiver and converter of sensor; it is a resonant sensor composed of AT-cut quartz crystal, which is modified by two balanced metal electrodes on the upper and lower surfaces of the crystal by vacuum deposition or evaporation. Commonly used metals are Au, Pt, Ni and Pd.

The basic principle of quartz crystal microbalance makes use of the piezoelectric effect of quartz crystal. If there is no external force, each crystal lattice in quartz crystal is in regular hexagonal shape; if mechanical pressure is applied on both sides of the crystal, the charge center of the crystal lattice will shift and polarize, generating electric field in corresponding direction. On the contrary, if an electric field is applied to the two electrodes of quartz crystal, the crystal will deform mechanically; this physical phenomenon is piezoelectric effect. If alternating voltage is applied to the two electrodes of the crystal, the crystal will vibrate mechanically; at the same time, the mechanical vibration of crystal will generate alternating voltage.

Unlike measurement with QCM sensor in vacuum or air, the energy dissipation from mechanical vibration is too high in liquid phase; at beginning, it was very difficult for QCM Technologies Inc. to find an appropriate electrical driving system to maintain stable vibration of piezoelectric quartz crystal oscillator in liquid phase. Things have changed in 1982; Okuhara and Nomurak made the technical breakthrough, and successfully developed the piezoelectric quartz oscillator that vibrates stably in liquid phase, enabling the application of QCM sensor in liquid phase. In 1985, by solving the formula about propagation of shear wave between piezoelectric quartz oscillator and Newtonian fluid with restriction by boundary conditions, Gordon and Kanazawa established the relation between change of piezoelectric quartz oscillator frequency and type of Newtonian fluid, i.e. Kanazawa-Gordon formula.

In case of traditional QCM sensor, a rigid material deposited on the chip surface will vibrate with the chip without deformation. In this case, the rigid material will not suppress the oscillation and the detected dissipation value will be low. On the other hand, the soft film will not vibrate completely with the chip. This means that it will deform during the testing. The soft film will suppress the oscillation and produce high dissipation. Therefore, the dissipation parameters provide the real-time properties of the softness/hardness or viscoelasticity of the films deposited on the chip surface, which makes it possible to monitor the conformational changes.

1. It qualitatively provides the information about the softness/hardness of adsorbate film and the information about the change of softness/hardness as a function of time.

2. It provides the key information of the quantitative model.

3. It provides the basic elements of viscoelastic film model.

SungThai’s QCM sensor is mainly applied to the field as follows：biomedical science、polymer material、organic chemistry、electrochemical analysis、surface chemical research、analytical chemistry

SungThai independently developed quartz microbalance sensors by using high precision coating technology for crystal components at aerospace grade, and manufactures various highly sensitive, high precision and reusable quartz crystal microbalance products for universities, research institutes and commercial enterprises. In addition, it is compatible with different quartz crystal microbalance systems. SungThai’s QCM sensor is mainly applied to the field as follows: biomedical science, polymer material, organic chemistry, electrochemical analysis, surface chemical research, analytical chemistry