JP4936921B2 - Quartz crystal sensor device - Google Patents

Description

  The present invention relates to a measuring device using a quartz crystal sensor capable of detecting adhesion of a trace substance with high sensitivity, and in particular, a quartz crystal resonator capable of detecting a qualitative change of the deposit when used in a liquid. The present invention relates to a sensor device.

  It is already well known that when a substance adheres to the surface of a crystal resonator or the surface of an electrode formed on the surface of the crystal resonator, the frequency characteristics of the crystal resonator change due to the change in mass. By utilizing this property, a sensor that detects and measures the adhesion of a very small amount of substance has been realized, which is called a quartz crystal sensor (hereinafter referred to as a QCM sensor). Further, detection and measurement of a specific substance in which a film having selectivity for the adhesion property of the substance is formed on the surface of the QCM sensor is also performed. Hereinafter, in order to clearly indicate the sensor head of the QCM sensor, it is referred to as a QCM element.

  The change in the frequency characteristics of the crystal resonator is detected by performing high-frequency oscillation using a crystal oscillator and measuring the oscillation frequency with a counter.

When material is attached only to the electrode, A is the electrode area of the QCM sensor, F ₀ is the oscillation frequency, ΔF is the change in frequency due to the material attached, μ is the shear stress of the crystal, and p is the crystal's shear stress. When the specific gravity, Δm, is the amount of change in the mass of the QCM sensor, the amount of change ΔF in the transmission frequency is known to have the following relationship.

  For example, when the oscillation frequency of the fundamental wave is 9 MHz with a diameter of 5 mm, it is said to be about 1.1 ng / Hz. In Equation 1, the coefficient of frequency change with respect to mass increases in accordance with the square of the oscillation frequency. For this reason, it is desirable to set the transmission frequency as high as possible.

  In the QCM element as described above, its natural frequency is measured, and the value is used to detect a trace substance in a liquid or gas. In addition to the natural frequency described above, there is a Q value when a QCM element is used in a resonance circuit, and a detector using this has been recently used for detection of trace substances.

  Since the present invention relates to the change of the Q value related to the oscillation circuit, the Q value of the electrical characteristics will be described below. In general, the Q value of the electrical characteristics of a crystal resonator is determined using an impedance analyzer.

  For example, an impedance analyzer is used in the QCM-Z500 manufactured by KSV Instruments. In addition, Patent Document 1 generally describes “a transmission circuit that supplies a LO signal whose amplitude is constant and frequency changes with time to a crystal resonator to be measured for Q value, and a current flowing through the crystal resonator is a voltage. A current-voltage converter for converting to a signal, a frequency conversion circuit for detecting a voltage component in phase with the LO signal supplied to the crystal resonator from an output signal from the voltage-current converter, and an output of the frequency conversion circuit A crystal resonator Q value measuring device is disclosed that includes a low-pass filter that extracts a low-frequency signal component from a signal and detects the maximum conductance at a resonance frequency by sweeping the crystal resonator. In addition, QCM-D300 manufactured by Q-Sense detects trace substances by measuring the decay time of the oscillating current of the crystal resonator.

Japanese Patent Laid-Open No. 6-18577

  By using a circuit that can also be used for frequency measurement, the present invention makes it possible to measure the oscillation intensity and the voltage applied to the electrodes of the crystal resonator as data that depends on the change in the Q value of the QCM element. By detecting changes in the Q value, and simultaneously performing frequency measurement and data measurement dependent on the Q value with the same QCM sensor, switching these measurements as appropriate or simultaneously measuring and performing data processing This improves the detection ability of trace substances.

The crystal resonator sensor device of the present invention is a crystal resonator sensor that is used for detection of a trace substance by contacting with liquid or gas.
An oscillation circuit comprising a quartz crystal resonator and an amplification device to which a minute amount of material is attached;
A frequency counter for measuring the oscillation frequency of the oscillation circuit;
Means for measuring the oscillation intensity of the oscillation circuit, the voltage applied to the electrode of the crystal resonator, or a voltage proportional to the voltage;
Data processing means for computing the measured data;
Means for displaying the processed data,
The means for measuring the voltage applied to the electrodes of the crystal resonator or a voltage proportional to the voltage comprises the means for measuring the oscillation input voltage and the means for measuring the oscillation output voltage of the amplification device,
1) Two-dimensional display of the measured frequency and the oscillation intensity or amplification degree,
2) Display the product or quotient of the measured change in frequency and the change in oscillation intensity or amplification according to the time series,
3) 3D display of the measured frequency, the oscillation intensity or amplification degree, and the time,
4) Whether to display the measured frequency and the time series of the ratio of the input voltage to the output voltage,
5) Obtain the measured frequency and the ratio or difference between the input voltage and the output voltage, and display the oscillation frequency and the ratio or difference two-dimensionally.
6) displaying the product of the time series time derivative of the measured frequency and the time series time derivative of the ratio of the input voltage and the output voltage according to the time series,
It has a display means which performs either of these.

One of the electrodes of the crystal resonator is connected to the input side of the amplification device, and the other of the electrodes of the crystal resonator is connected to the output side of the amplification device.

The amplification device is a bipolar transistor or a field effect transistor. The input voltage is measured by a circuit connected to the base electrode or the gate electrode, and the output voltage is connected to the emitter or collector, or the source or drain. Measure with a circuit.

  When the oscillation intensity is used, the amplification device is a bipolar transistor or a field effect transistor, and the oscillation intensity is measured by an emitter or collector, or a circuit connected to the source or drain.

  In addition, the oscillation circuit includes an oscillation intensity adjusting unit that suppresses the oscillation intensity to a state near the critical point where the oscillation is sustained, so that the measurement data can be changed in the oscillation intensity or the voltage applied to the crystal oscillator electrode. It is easy to detect the influence on the change of the.

  According to the present invention, the ability to detect a trace substance can be improved by performing frequency measurement and measurement related to a change in Q value with the same QCM sensor, and switching at the same time or performing measurement at the same time.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing the entire quartz resonator sensor of the present invention. The frequency of the signal from the QCM sensor 1 is measured by the frequency counter 4 and this data is displayed on the display device 6. Also, the signal voltage on the input side and the signal voltage on the output side of the QCM sensor 1 are converted by an AD (analog-digital) converter 5 and displayed on the display device 6. In the display device 6, the difference or ratio between the input signal strength and the output signal strength of the amplifier 3 is taken and displayed in time series together with the above frequency. Here, it is known that the difference or ratio between the input side signal strength and the output side signal strength of the amplifier 3 changes depending on the Q value of the resonator (that is, the QCM sensor). The display device 6 can take the frequency on the horizontal axis and the above ratio on the vertical axis. If necessary, changes in frequency and Q value are switched or displayed simultaneously.

  FIG. 2 is an example of a QCM sensor circuit. Although a bipolar transistor is shown as the amplifying device, a field effect transistor can also be used. The QCM element is connected between the collector and the base, takes out signals from the input side and the output side of the amplifying device, performs AD conversion, performs digital processing, and displays on the display device 6.

  Furthermore, by detecting and maintaining the oscillation state near the oscillation limit by changing the power supply voltage, it is possible to increase the detection sensitivity of the change in the Q value. A method for adjusting the oscillation state in this way is already well known. Other methods include adjusting the feedback capacitance, adjusting the emitter (or source) resistance, adjusting the base (or gate) bias, and the like.

  3 and 4 show other examples of the QCM sensor circuit. The advantages of using these oscillation circuits are as follows. First, the circuit configuration is very simple and suitable for integration in a sensor head. Such integration makes it difficult to be affected by external fluctuation factors. In this circuit, a change in frequency and a change in Q value can be observed simultaneously. In this oscillation circuit, the change in the Q value is detected by increasing or decreasing the oscillation intensity as the Q value of the resonator is increased or decreased by the QCM sensor.

  FIG. 5 shows an example in which the influence of the liposome solution is measured by a sensor having a cellulose membrane using the circuit of FIG. FIG. 5 is a diagram showing the ratio of frequency and output side voltage / input side voltage in time series. A and A 'in the figure are peaks due to the sensor touching the sample liquid, and B and B' or C and C 'are peaks due to abrupt changes in the sample liquid.

  FIG. 6 depicts the data of FIG. 5 with the horizontal axis representing frequency and the vertical axis representing the above ratio. A, B, and C in FIGS. 5 and 6 correspond to each other. It can be seen that the graph of FIG. 6 shows the change points B and C more clearly than FIG.

  FIG. 7 and FIG. 8 show examples in which the influence of the liposome solution was measured using a sensor having a cellulose membrane in the same manner as described above using the circuit of FIG.

FIG. 7 is a diagram showing a time lapse of the transition from the reference frequency. The change in the section from (a) to (d) is due to the following operations.
(B) A sensor having a cellulose membrane, in which a liposome solution is injected into a measuring cell filled with a buffer solution (here, phosphate buffer solution containing sodium chloride), and the target substance is adsorbed by the quartz sensor membrane. is there.
(B) The case where the measurement cell is washed with a buffer solution, and after the solution in the measurement cell is replaced with the buffer solution.
(C) The case where the glycine solution is injected, the solution in the measurement cell is changed with a buffer solution, and then the CHAPS solution is injected.
(D) The measurement cell is washed with a buffer solution, and the solution in the measurement cell is replaced with a buffer solution.

  FIG. 8 is a diagram illustrating a time lapse of transition from the reference oscillation intensity. It can be seen that the oscillation intensity also changes in the section (b) to (d) above.

  FIG. 9 shows the product of the time derivative of FIG. 7 and the time derivative of FIG. The transition part indicated by A in FIG. 9 is on the plus side as in the section A, but the transition part indicated by B is on the minus side, and the behavior is different from that in the section A. Thus, by displaying the product of the time derivative and the time derivative of FIG. 8, it is possible to detect a state change that could not be detected in the past.

  In section (a) of FIG. 9, normal QCM characteristics are shown. In the normal change, the substance attaches / detaches to / from the electrode, the mass on the electrode changes, and the QCM measurement value changes. As the substance adheres to the quartz crystal as a sensor and the mass of the vibrating part increases, The oscillation intensity also decreases, and conversely, the oscillation intensity increases as it detaches and the mass decreases.

A negative value in the transition portion indicated by B indicates that a change opposite to the normal change occurs. For example, in this section, there is a possibility that the state of the film containing the adsorbing substance changes at the molecular level. This change cannot be captured by normal QCM measurements. Thus, the QCM sensor of the present invention has more contents that can be detected than the conventional QCM sensor.
Further, since the measurement using the QCM sensor of the present invention is a measurement of mass change without using gravity, it is obvious that it can be used for measurement in a zero-gravity environment.

  FIG. 10 is a diagram in which FIGS. 7 and 8 are three-dimensionally displayed. From the three-dimensional display, it can be seen that the behavior of the second section is different from the behavior of the first section and is a graph extending in different directions.

  Although the present invention has been described mainly with respect to detection of trace substances in a liquid, measurement in a gas is possible if there is a sufficient concentration.

It is a block diagram which shows the whole crystal oscillator sensor apparatus of this invention. It is a circuit diagram which shows the 1st example of a crystal oscillator sensor. It is a circuit diagram which shows the 2nd example of a crystal oscillator sensor. It is a circuit diagram which shows the 3rd example of a crystal oscillator sensor. It is a figure which shows the example of a measurement using this invention. FIG. 6 is a diagram showing the data of FIG. 5 with the horizontal axis representing frequency and the vertical axis representing the output side voltage / input side voltage ratio. It is a figure which shows the time passage of the transition from a reference frequency. It is a figure which shows the time passage of the transition from a reference | standard oscillation intensity | strength. It is a figure which shows the product of the time differentiation of FIG. 7, and the time differentiation of FIG. It is the figure which displayed FIG. 7 and FIG. 8 three-dimensionally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 QCM sensor 2 QCM element 3 Amplifier 4 Frequency counter 5 AD (analog-digital) converter 6 Display apparatus

Claims (3)

Quartz crystal sensor used to detect trace substances by contacting with liquid or gas.
An oscillation circuit comprising a quartz crystal resonator and an amplification device to which a minute amount of material is attached;
A frequency counter for measuring the oscillation frequency of the oscillation circuit;
Means for measuring the oscillation intensity of the oscillation circuit, the voltage applied to the electrode of the crystal resonator, or a voltage proportional to the voltage;
Data processing means for computing the measured data;
Means for displaying the processed data,
The means for measuring the voltage applied to the electrodes of the crystal resonator or a voltage proportional to the voltage comprises the means for measuring the oscillation input voltage and the means for measuring the oscillation output voltage of the amplification device,
1) Two-dimensional display of the measured frequency and the oscillation intensity or amplification degree,
2) Display the product or quotient of the measured change in frequency and the change in oscillation intensity or amplification according to the time series,
3) 3D display of the measured frequency, the oscillation intensity or amplification degree, and the time,
4) Whether to display the measured frequency and the time series of the ratio of the input voltage to the output voltage,
5) Obtain the measured frequency and the ratio or difference between the input voltage and the output voltage, and display the oscillation frequency and the ratio or difference two-dimensionally.
6) displaying the product of the time series time derivative of the measured frequency and the time series time derivative of the ratio of the input voltage and the output voltage according to the time series,
A crystal resonator sensor device comprising display means for performing any of the above. 2. One of the electrodes of the crystal resonator is connected to the input side of the amplification device, and the other electrode of the crystal resonator is connected to the output side of the amplification device. The crystal resonator sensor device described. The above amplification device is a bipolar transistor or a field effect transistor. The input voltage is measured by a circuit connected to the base electrode or the gate electrode, and the output voltage is a circuit connected to the emitter or collector, or the source or drain. in quartz oscillator sensor device according to claim 1, characterized that you measure.

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