Measuring and testing – Mass
Reexamination Certificate
1999-05-04
2002-05-14
Raevis, Robert (Department: 2856)
Measuring and testing
Mass
Reexamination Certificate
active
06386053
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a mass sensor for determining a minute mass of a nanogram (10
−9
g) order, for example, a mass sensor for sensing microorganisms such as bacteria, viruses, and protozoa (immune sensor), and a mass sensor for sensing moisture, toxic substances, or specific chemical substances such as taste components (moisture meter, gas sensor, and taste sensor), and a method for sensing a mass. In particular, the present invention relates to a mass sensor, and a method for sensing a mass, conveniently used for determining the mass of a body to be sensed by measuring change in resonant frequencies caused by changes in the mass of the diaphragm on which a catching substance for catching a body to be sensed by reacting only with the body to be sensed is applied.
Since the mass sensor of the present invention is not limited to the measurement of change in the mass of the catching substance applied on a diaphragm as described above, that is, not limited to the indirect measurement of change in the mass of a diaphragm, but it is naturally possible to sense change in resonant frequency due to change in the mass of the diaphragm itself, the mass sensor can also be used as a thickness meter for vapor-deposited films or a dew point meter.
Furthermore, even if the mass of the diaphragm is not changed directly or indirectly, the mass sensor of the present invention can also be used as a vacuum meter, a viscosity meter, or a temperature sensor by placing it in an environment to cause change in resonant frequency, that is, by placing it in an environment of medium gases or liquids having different degrees of vacuum, viscosity, or temperature.
Thus, although the mass sensor of the present invention can be used in various applications depending on its embodiments, the same basic principle is also applied to the measurement of change in resonant frequencies of the diaphragm and the resonating portion including the diaphragm.
BACKGROUND ART
Recent progress of scientific and medical technologies, and newly developed medicines such as antibiotics and chemicals have enabled the treatment of various diseases heretofore considered to be difficult to treat. On the other hand, especially in developed countries where people are accustomed in such medical civilization, immunological resistance of human beings have lowered, and many people have suffered from various diseases caused by substances or microorganisms which heretofore had not hurt human beings.
Among what are referred to as diseases, microorganism examinations are essential for the treatment of diseases caused by microorganisms such as bacteria, viruses, or protozoa, to find their pathogens, to clarify their types, and to determine drugs to which they are sensitive.
At present, in the first stage of microorganism examinations, since the cause of a disease and the type of the pathogen can be estimated from the symptoms, various specimens, such as blood, are selected depending on the type of the disease, pathogens present in the specimens are morphologically identified, or antigens or the specific metabolites of pathogens (e.g., toxins or enzymes, etc.) existing in the specimens are immunochemicaly identified. This process is smear, tinction, or microscopy used in bacterial examinations, and in recent years, instantaneous identification has become possible in this stage by fluorescent antibody tinction or enzymatic antibody tinction.
Furthermore, the virus serological test, recently used in the detection of viruses, is a method for proving the presence of specific immunity antibodies that appear in the serum of a patient. Examples of the method include the complement fixation reaction in which the presence of antibodies or antigens is determined by adding complements to test blood, and by observing whether the complements react with antigens or antibodies in the blood and fix to the cell membranes of the antigens or antibodies, or destroy the cell membranes.
Except extremely special cases where symptoms have not been seen heretofore, and the disease is caused by a new pathogen which has not been discovered, in the treatment of diseases caused by microorganisms or the like, adequate treatment can be conducted by finding pathogens in an early stage through the microorganism test described above, and the patient can be led to recovery without worsening of the symptoms.
However, with methods such as smear, tinction, and microscopy, the detection of microorganisms is often difficult depending on their quantities, and time-consuming treatment such as the culture of specimens on an agar is required at need. Also in the virus serological test, since measurements must be performed as a rule during both the acute stage and the convalescent stage for determination from the movement of the quantities of antibodies, there is the problem of time consumption from the point of view of prompt diagnosis.
As seen in complement fixation described above, when a substance to be sensed reacts with a catching substance which catches the substance to be sensed by reacting only with specific substance to be sensed, microorganisms, the mass of the catching substance increases by the mass of the substance to be sensed, even slightly. Such an increase in the mass similarly occurs in the relationship between a catching substance and a chemical substance such as a specific gaseous substance and a smell component, and also applies to the case where a substrate itself without change in the mass is a catching substance, on which a specific substance is deposited or added. On the contrary, when a reaction in which a substance to be sensed caught by a catching substance or the like is released occurs, the mass of the catching substance or the like slightly decreases.
As an example of a method for sensing change in such a small mass, U.S. Pat. No. 4789804 discloses in
FIG. 27
thereof a mass sensor
80
comprising a quartz oscillator
81
and electrodes
82
,
83
facing the quartz oscillator. When any substance adheres externally on these electrodes
82
,
83
, the mass sensor
80
senses change in their mass using change in the resonant frequency of the thickness slip oscillation of the quartz oscillator
81
in the direction of the surface of the electrodes. Since such a mass sensor
80
measures change in resonant frequency basically caused by change in the mass load on the quartz oscillator
81
, such a mass sensor
80
is considered to be able to be used also as a thickness meter for measuring the thickness or the growth of a vapor-deposited film, or a moisture meter.
However, when such a quartz oscillator
81
is used, since the part on which an external substance adheres and the part for detecting resonant frequency are in the same location, for example, the resonant frequency is unstable when the piezoelectric properties of the mass sensor
80
itself vary due to the temperature of the specimen or change in temperature. Also, if the specimen is a conductive solution, and when the mass sensor
80
is immersed unprotected in the specimen, a short-circuit between electrodes may occur. Therefore, the mass sensor
80
must be subjected to insulation such as resin coating.
SUMMARY OF THE INVENTION
The present invention aims to solve the above problems of a micro-mass sensor, and according to the present invention, there are provided first to sixth mass sensors described below.
As a first mass sensor, there is provided a mass sensor characterized in that a piezoelectric element is arranged on at least a part of at least one plate surface of a sensing plate, a side of at least one sheet-like diaphragm is joined to a side of said sensing plate so that the plate surface of said diaphragm is perpendicular to the plate surface of said sensing plate, the other side of said sensing plate is joined to a sensor substrate, and a resonance portion is formed of said sensing plate, said diaphragm, and said piezoelectric element.
Furthermore, as a second mass sensor, there is provided a mass sensor characterized in that a connection plate is joined to
Kimura Koji
Ohnishi Takao
Takeuchi Yukihisa
Burr & Brown
NGK Insulators Ltd.
Raevis Robert
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