JP2004245719A - Method and device for measuring mass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for measuring a mass adoptable to an increase in the number of sensors and an increase in sensitivity. <P>SOLUTION: In this device for measuring the mass, a specimen solution is brought into contact with the surface of the excitation electrode 22a of a piezoelectric vibration piece 20 coated with sensitive film to measure the mass of a specific substance in the specimen solution. The device comprises a constant volume jetting means (ink jet head) 30 jetting the specimen solution on the surface of the excitation electrode 22a, a position control means 50 controlling the relative position of the piezoelectric vibration piece 20 to the constant volume jetting means 30, and a temperature control means 18 holding the piezoelectric vibration piece 20 and the constant volume jetting means 30 at a specified temperature or below. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２３】
ただし、ｄｆは圧電振動片の共振周波数の変化量、ｆ_０は圧電振動片の共振周波数の初期値、ρは圧電材料の密度、μは圧電材料のせん断応力、ｄｍは励振電極に結合した特定物質の質量、Ａは励振電極の面積である。上式からわかるように、圧電振動片の共振周波数の初期値ｆ_０が高いほど、その変化量ｄｆが大きくなり、質量測定装置が高感度化する。例えば、ｆ_０を従来の２７ＭＨｚから１５０ＭＨｚまで高周波化すれば、感度を３０倍にすることができる。そして圧電振動片を高周波化するには、圧電振動片の振動部における肉厚を薄くすればよい。
【００２４】
図２に、逆メサ型圧電振動片の説明図を示す。なお、図２（１）は平面図であり、図２（２）は図２（１）のＡ−Ａ線における側面断面図である。圧電振動片２０として、いわゆる逆メサ型圧電振動片を使用する。逆メサ型圧電振動片２０は、水晶等の圧電材料を平板状に切り出し、その両面中央部に凹部を形成して薄肉化し、その薄肉部の両面に励振電極２２ａ，２２ｂを形成したものである。圧電振動片２０の周縁の厚肉部２１には、励振電極２２ａ，２２ｂと導通する接続電極２４ａ，２４ｂを形成する。なお、各電極はＡｕ／ＣｒまたはＡｇ／Ｃｒの２層によって構成する。このような逆メサ型圧電振動片では、周縁の厚肉部により中央の薄肉振動部が保護されるので、外力による振動部の破壊を防止することができる。これにより、高周波の圧電振動片が利用可能となり、質量測定装置を高感度化することができる。
【００２５】
そして、この圧電振動片２０における上面の励振電極２２ａの表面に感応膜を塗布して、圧電振動片２０をほぼ水平に配置する。感応膜は、検出すべき特定物質の分子のみと結合する物質であり、特定物質に対応して選択する。
【００２６】
一方、図１に示すように、検体溶液を吐出する定量吐出手段３０を圧電振動片２０の上方に設ける。定量吐出手段３０として、いわゆるインクジェットヘッドを使用する。なお、定量吐出手段３０は所定量の検体溶液を所定位置に吐出できるものであればよく、ピエゾ方式やバブルインクジェット方式、サーマルインクジェット方式など、インクジェットの方式は問わない。したがって、熱影響を受けやすい検体溶液の場合には、ピエゾ方式を採用すればよい。その他の場合には、ヘッド構造を簡略化できるバブルインクジェット方式やサーマルインクジェット方式を採用すればよい。
【００２７】
図３に、ピエゾ方式のインクジェットヘッドの側面断面図を示す。このインクジェットヘッド３０は、主に、ガラス基板３２、シリコン基板３６およびシリコン等からなるノズルプレート３８で構成する。シリコン基板３６とノズルプレート３８との間にインク室４２を形成して検体溶液を封入する。このインク室４２に隣接するノズルプレート３８には、ノズル３９を形成する。一方、インク室４２の壁面を構成するシリコン基板３６を薄肉化して、振動板３７を形成する。そして、振動板３７とガラス基板３２との間に、ピエゾ（圧電）素子３４を配置する。なお、ピエゾ素子３４の両端面には、駆動用の電極３３，３５を配置する。この駆動用電極３３，３５によりピエゾ素子３４に電圧を印加すると、ピエゾ素子が膨張する。これにより、振動板３７がインク室４２を圧縮し、インク室４２内の検体溶液がノズル３９から吐出される。
【００２８】
図４に、位置制御手段の斜視図を示す。圧電振動片２０の励振電極を定量吐出手段３０のノズル直下に配置するため、位置制御手段５０を設ける。定量吐出手段３０は、シャフト５６に対して摺動自在に取り付けるとともに、図示しないタイミングベルト等に固定して、Ｘ方向に沿って移動可能とする。一方、圧電振動片２０を載置するトレイ５２は、シャフト５４に対して摺動自在に取り付けるとともに、図示しないタイミングベルト等に固定して、Ｙ方向に沿って移動可能とする。また、圧電振動片２０および定量吐出手段３０の両方または一方の位置を検知するＣＣＤカメラ等の画像認識手段５８を設ける。
【００２９】
位置制御の具体的な手順は、まず圧電振動片２０をトレイ５２に載置して、定量吐出手段３０の下方に移動させる。次に、画像認識手段５８により圧電振動片２０を撮像して、圧電振動片２０の現在位置を検知する。そして、圧電振動片２０の励振電極が定量吐出手段３０のノズル直下に位置するように、定量吐出手段３０をＸ方向に移動させるとともに、圧電振動片２０を載置したトレイ５２をＹ方向に移動させる。これにより、検体溶液を励振電極上に正確に吐出させることができる。なお、圧電振動片の位置を固定しつつ、定量吐出手段をＸＹ両方向に移動させるように、位置制御手段を構成してもよい。
【００３０】
ところで、水晶振動子マイクロバランス法は、感応膜と特定物質との結合に適した所定の温度下で実施する必要がある。そこで、上述した圧電振動片２０および定量吐出手段３０を所定の温度下に保持する温度調節手段１８を設ける。温度調節手段１８として、圧電振動片２０および定量吐出手段３０を内部に収容可能な恒温槽を使用する。これにより、検体溶液を含む定量吐出手段３０の全体を、効率的かつ正確に所定の温度下に保持することができる。なお、圧電振動片２０や定量吐出手段３０の各部にヒータ等を設けて、それぞれ別個に温度調節することも可能である。
【００３１】
そして、図１に示すように、圧電振動片２０を外部の発振回路４０に接続する。発振回路４０は、圧電振動片２０の励振電極に通電して圧電振動片２０を発振させるものである。また、発振回路４０は周波数カウンタ５に接続する。周波数カウンタ５は、圧電振動片２０の共振周波数を測定するものである。また、周波数カウンタ５はコンピュータ６に接続する。コンピュータ６は、周波数カウンタ５が測定した共振周波数から、圧電振動片２０の励振電極２２ａに付着した特定物質の質量を算出するものである。加えて、特定物質の付着量の経時変化から検体溶液中の特定物質の有無および濃度等を解析し得るようにコンピュータ６を構成するのが好ましい。
【００３２】
次に、第１実施形態に係る質量測定装置の使用方法について説明する。
図１に示すように、まず定量吐出手段３０の下方に圧電振動片２０を配置する。その際、位置制御手段５０により、圧電振動片２０と定量吐出手段３０との相対位置制御を行って、圧電振動片２０の上側の励振電極２２ａを定量吐出手段３０のノズル直下に配置する。次に、温度調節手段１８を作動させて、圧電振動片２０および検体溶液を含む定量吐出手段３０を所定の温度下に保持する。
【００３３】
質量測定を行うには、まず発振回路４０から圧電振動片２０に通電して圧電振動片２０を発振させる。また、周波数カウンタ５により圧電振動片２０の共振周波数を連続的に計測しておく。次に、定量吐出手段３０のノズルから検体溶液を吐出し、圧電振動片２０の上側の励振電極２２ａに接触させる。検体溶液が励振電極２２ａに接触すると、検体溶液中の特定物質が励振電極表面の感応膜と結合する。これにより、励振電極２２ａの質量が増加して、圧電振動片２０の共振周波数が低下する。この共振周波数の低下量等をコンピュータ６で解析することにより、特定物質の有無および濃度等を算出することができる。
【００３４】
なお、検体溶液が励振電極２２ａの表面のみに接触するように、定量吐出手段３０からの検体溶液の吐出量を設定すれば、検体溶液は感応膜の塗布されていない部分には接触しない。これにより、検体溶液中の特定物質の質量を正確に把握することができる。一方、定量吐出手段３０を使用するので、励振電極に吐出した検体溶液量を正確に把握することができる。以上により、検体溶液中の特定物質の濃度を直接的に算出することが可能となり、質量測定の精度を向上させることができる。
【００３５】
以上に詳述した第１実施形態に係る質量測定方法および質量測定装置により、高感度化に対応することが可能となる。
すなわち第１実施形態では、定量吐出手段により、圧電振動片の上側の励振電極に検体溶液を吐出させて質量測定を行う構成とした。この場合、下側の励振電極と短絡するおそれがないので、下側の励振電極を検体溶液から封止するための被覆部材が不要となり、製造コストを削減することができる。また、大量の検体溶液が不要となり、微量の検体溶液中に含まれる特定物質の質量測定を行うことができる。加えて、検体溶液の吐出位置および吐出量を正確に制御することができるので、高精度の質量測定が可能である。
【００３６】
さらに、圧電振動片の一部のみに検体溶液が接触するので、圧電振動片の発振が検体溶液の影響によって妨げられることが少なくなる。これにより、高周波の圧電振動片でも安定して発振させることができる。これにともなって、高周波の圧電振動片を利用することが可能となり、質量測定の高感度化に対応することができる。
【００３７】
次に、第２実施形態について説明する。
図５および図６に、第２実施形態で使用する圧電振動片の説明図を示す。図５は図６のＣ−Ｃ線における側面断面図であり、図６（１）は平面図であり、図６（２）は底面図である。第２実施形態に係る質量測定方法は、圧電振動片１２０に複数組の励振電極１２２ａ，１２２ｂを形成し、その圧電振動片１２０における一方面側の各励振電極１２２ａの表面に感応膜を塗布し、その各励振電極１２２ａに検体溶液を接触させて、検体溶液中の特定物質の質量測定を行う方法であって、定量吐出手段により、前記各励振電極１２２ａに検体溶液を順次吐出して接触させるものである。なお、第１実施形態と同様の構成となる部分については、その説明を省略する。
【００３８】
第２実施形態で使用する圧電振動片１２０は、図５に示すように、水晶等の圧電材料を平板状に切り出し、その両面の対応する位置に複数の凹部を形成して薄肉化し、各薄肉部の表裏両側に励振電極１２２ａ，１２２ｂを形成したものである。なお、表裏一対の励振電極１２２ａ，１２２ｂを形成した部分が、それぞれ振動部１２１として機能する。
【００３９】
この圧電振動片１２０において、図６（１）に示す表側には、各励振電極１２２ａに対応する複数の接続電極１２４ａを周縁部に形成する。一方、図６（２）に示す裏側には、全ての励振電極１２２ｂと導通する共通接続電極１２４ｂを周縁部に形成する。なお質量測定を行う際には、裏側の共通接続電極１２４ｂは、図１に示す発振回路４０に常時接続しておく。そして、質量測定を行う振動部１２１に対応する表側の接続電極１２４ａを、順次発振回路４０に接続して質量測定を行う。
そして、この圧電振動片１２０の表側における各励振電極１２２ａの表面に、それぞれ異なる特定物質と結合する感応膜を塗布する。
【００４０】
この圧電振動片と定量吐出手段との相対的な位置制御は、以下の手順で行う。まず、図４に示す圧電振動片２０の代わりに、上述した圧電振動片１２０をトレイ５２に載置して、定量吐出手段３０の下方に移動させる。次に、画像認識手段５８により圧電振動片の現在位置を検知する。そして、質量測定を行う振動部の励振電極が、定量吐出手段３０のノズル直下に位置するように、定量吐出手段３０をＸ方向に移動させるとともに、圧電振動片を載置したトレイ５２をＹ方向に移動させる。この移動作業を、質量測定を行う振動部の全てについて行う。これにより、質量測定を行う各振動部の励振電極上に、検体溶液を正確に吐出させることができる。
【００４１】
第２実施形態に係る質量測定方法および質量測定装置により、マルチセンサ化に対応することができる。
すなわち第２実施形態では、圧電振動片に複数組の励振電極を形成し、その圧電振動片における一方面側の各励振電極の表面に感応膜を塗布し、定量吐出手段により前記各励振電極に検体溶液を順次吐出して、検体溶液中の特定物質の質量測定を行う構成とした。これにより、下側の励振電極を検体溶液から隔離するための大がかりな被覆部材が不要となり、製造コストを削減することができる。また、複数の振動部を有するマルチセンサ型の圧電振動片を使用する場合でも、大量の検体溶液が不要となり、微量の検体溶液中に含まれる特定物質の質量測定を行うことができる。なお、検体溶液の吐出位置および吐出量を正確に制御することができるので、高精度の質量測定が可能である。これらにより、質量測定のマルチセンサ化に対応することができる。
【図面の簡単な説明】
【図１】第１実施形態に係る質量測定装置の説明図である。
【図２】逆メサ型圧電振動片の説明図である。
【図３】ピエゾ方式インクジェットヘッドの側面断面図である。
【図４】位置制御手段の説明図である。
【図５】マルチセンサ型圧電振動片の側面断面図である。
【図６】マルチセンサ型圧電振動片の平面図および底面図である。
【図７】従来の質量測定チップの説明図である。
【図８】従来の質量測定装置の説明図である。
【符号の説明】
１…質量測定装置
５…周波数カウンタ
６…コンピュータ
１８…温度調節手段
２０…圧電振動片
２１…厚肉部
２２ａ，２２ｂ…励振電極
２４ａ，２４ｂ…接続電極
３０…定量吐出手段
４０…発振回路
５０…位置制御手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mass measuring method and a mass measuring device used for measuring the presence or absence, concentration, and the like of a specific substance in a sample solution using a piezoelectric vibrating reed.
[0002]
[Prior art]
In fields such as food, biochemistry, and the environment, a quartz crystal microbalance method is used to measure the presence or absence, concentration, and the like of a specific substance. As a specific method, first, a sensitive film of a specific substance is applied to the surface of the excitation electrode on one side of the piezoelectric vibrating reed. Then, the piezoelectric vibrating reed is immersed in a sample solution containing a specific substance. Then, the specific substance in the sample solution binds to the sensitive membrane, and the mass of the excitation electrode increases. As the mass of the excitation electrode increases, the resonance frequency of the piezoelectric vibrating piece decreases. Thereby, the presence / absence and concentration of the specific substance in the sample solution can be determined.
[0003]
By the way, when the piezoelectric vibrating reed is immersed in the sample solution, if the excitation electrodes formed on both surfaces thereof are short-circuited to each other, the piezoelectric vibrating reed cannot be oscillated. Therefore, it is necessary to cover the excitation electrode on the other surface side on which the sensitive film is not coated with a covering member or the like, thereby sealing the excitation electrode from the sample solution and preventing a short circuit between the electrodes.
[0004]
FIG. 7 is an explanatory diagram of the mass measuring chip described in Patent Document 1. Note that FIG. 7A is a plan view, and FIG. 7B is a side cross-sectional view taken along line GG of FIG. 7A. The mass measuring chip 503 includes a piezoelectric vibrating reed 520 in which circular excitation electrodes 522a and 522b are formed on both sides of a rectangular piezoelectric flat plate. Further, a covering member 550 made of an insulating thin plate is adhered to one surface side of the piezoelectric vibrating reed 520 by an adhesive 558. Thus, the excitation electrode 522b on one side is sealed from the sample solution, and a short circuit between the electrodes is prevented. Further, a lead wire 524 is attached to each excitation electrode, and a portion of the lead wire 524 immersed in the sample solution is covered with an adhesive 558.
[0005]
FIG. 8 shows an explanatory diagram of a conventional mass measuring device. In the mass measuring device 501, the above-described mass measuring chip 503 is connected to an external oscillation circuit 540. The mass measurement is performed by applying the above-described sensitive film (not shown) to the surface of the excitation electrode 522a and immersing the mass measurement chip 503 in the sample solution 7. First, the piezoelectric vibrating reed of the mass measuring chip 503 is oscillated by the oscillation circuit 540, and the resonance frequency of the piezoelectric vibrating reed is measured by the frequency counter 5. As described above, when the specific substance in the sample solution binds to the sensitive film and the mass of the excitation electrode increases, the resonance frequency of the piezoelectric vibrating piece decreases. Therefore, the computer 6 analyzes the decrease amount of the resonance frequency and calculates the presence / absence and concentration of the specific substance in the sample solution.
[0006]
[Patent Document 1]
JP-A-6-138125 [Patent Document 2]
JP 2000-338022 A
[Problems to be solved by the invention]
As described above, when the piezoelectric vibrating reed is used by immersing it in the sample solution, the excitation electrode not coated with the sensitive film is covered with a covering member or the like, thereby sealing the excitation electrode from the sample solution. It is necessary to prevent a short circuit between the electrodes. Therefore, there is a problem that many manufacturing costs are required. Further, when the piezoelectric vibrating reed is used by immersing it in a sample solution, a large amount of the sample solution is required, and there is a problem that it is impossible to measure the mass contained in a small amount of the sample solution.
[0008]
Recently, a multi-sensor is required for a mass measuring device. Making a mass measuring device a multi-sensor means enabling mass measurement of many types of specific substances at the same time. In order to make the mass measuring chip a multi-sensor, a piezoelectric vibrating reed having a plurality of vibrating parts is formed, and a different sensitive film is applied to the excitation electrode of each vibrating part. However, in order to use such a piezoelectric vibrating reed immersed in a sample solution, a large amount of the sample solution is required. In addition, the covering member for preventing the short circuit of each excitation electrode becomes large-scale, and a large production cost is required. For these reasons, there is a problem that it is not possible to cope with the multi-sensor of the mass measuring device.
[0009]
On the other hand, high sensitivity is required for mass measuring devices. In order to increase the sensitivity of the mass measuring device, it is necessary to increase the frequency of the piezoelectric vibrating reed. However, when the high-frequency piezoelectric vibrating reed is used while immersed in the sample solution, there is a problem that the impedance of the piezoelectric vibrating reed increases and oscillation becomes unstable. Therefore, there is a problem that high-sensitivity mass measurement cannot be performed.
[0010]
The present invention focuses on the above problems, can reduce the manufacturing cost, can measure the mass of a specific substance contained in a trace amount of a sample solution, and can respond to multi-sensor and high sensitivity. It is an object of the present invention to provide a mass measuring method and a mass measuring device that are possible.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the mass measuring method according to the present invention comprises applying a sensitive film to a surface of an excitation electrode on one side of a piezoelectric vibrating reed, bringing a sample solution into contact with the excitation electrode, In the method for measuring the mass of a specific substance, the sample solution is discharged to and brought into contact with the excitation electrode by a quantitative discharge means.
[0012]
In this case, since there is no possibility of short-circuit with the lower excitation electrode, a covering member for sealing the lower excitation electrode from the sample solution is not required, and the manufacturing cost can be reduced. Further, a large amount of the sample solution is not required, and the mass measurement of the specific substance contained in the minute amount of the sample solution can be performed. In addition, since the discharge position and discharge amount of the sample solution can be accurately controlled, high-precision mass measurement is possible.
[0013]
Furthermore, since the sample solution contacts only a part of the piezoelectric vibrating reed, the oscillation of the piezoelectric vibrating reed is less hindered by the influence of the sample solution. Thus, even a high-frequency piezoelectric vibrating reed can be oscillated stably. Accordingly, it is possible to use a high-frequency piezoelectric vibrating reed, and it is possible to cope with higher sensitivity of mass measurement.
[0014]
Further, a plurality of sets of excitation electrodes are formed on the piezoelectric vibrating reed, a sensitive film is applied to the surface of each of the excitation electrodes on one side of the piezoelectric vibrating reed, and a sample solution is brought into contact with each of the excitation electrodes, This is a method for measuring the mass of a specific substance in a sample solution, wherein the sample solution is sequentially discharged to and contacted with each of the excitation electrodes by a quantitative discharge means.
[0015]
This eliminates the need for a large covering member for sealing the lower excitation electrode from the sample solution, thereby reducing the manufacturing cost. Further, even when a multi-sensor type piezoelectric vibrating reed having a plurality of vibrating parts is used, a large amount of a sample solution is not required, and the mass measurement of a specific substance contained in a minute amount of a sample solution can be performed. In addition, since the discharge position and discharge amount of the sample solution can be accurately controlled, high-precision mass measurement is possible. Accordingly, it is possible to cope with the multi-sensor mass measurement.
[0016]
It should be noted that the sample solution may be discharged and brought into contact with only the surface of the excitation electrode. In this case, the sample solution does not come into contact with the portion where the sensitive film is not applied. Therefore, the accuracy of mass measurement can be improved.
[0017]
On the other hand, the mass measuring device according to the present invention is a device for measuring the mass of a specific substance in the sample solution by bringing the sample solution into contact with the surface of the excitation electrode of the piezoelectric vibrating reed coated with the sensitive film. Thus, a configuration is provided in which a quantitative discharge means for discharging a sample solution onto the surface of the excitation electrode is provided. This makes it possible to reduce the manufacturing cost, measure the mass of a specific substance contained in a minute amount of a sample solution, and cope with a multi-sensor and high sensitivity.
[0018]
Further, the piezoelectric vibrating reed may be configured to include a temperature adjusting unit for maintaining the piezoelectric vibrating reed and the fixed-quantity discharging unit at a predetermined temperature. This can minimize the influence of the temperature change on the reaction between the sensitive film applied to the surface of the excitation electrode and the specific substance in the sample solution, and can improve the accuracy of mass measurement.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of a mass measuring method and a mass measuring device according to the present invention will be described in detail with reference to the accompanying drawings. Note that what is described below is merely an embodiment of the present invention, and the present invention is not limited thereto.
[0020]
FIG. 1 is an explanatory diagram of the mass measuring device according to the first embodiment. The mass measuring device 1 is a device for measuring the mass of a specific substance in the sample solution by bringing the sample solution into contact with the surface of the excitation electrode 22a of the piezoelectric vibrating reed 20 to which the sensitive film has been applied. The apparatus includes a fixed amount discharging unit 30 for discharging the sample solution to the surface of 22a, and a temperature adjusting unit 18 for maintaining the piezoelectric vibrating reed 20 and the fixed amount discharging unit 30 at a predetermined temperature.
[0021]
The mass measuring device according to the first embodiment is obtained by increasing the sensitivity of a conventional mass measuring device. The sensitivity of the mass measuring device can be expressed by the following equation.
[0022]
(Equation 1)

[0023]
However, df is the change in the resonance frequency of the piezoelectric vibrating piece, f ₀ is the initial value of the resonance frequency of the piezoelectric vibrating piece, [rho is the density of the piezoelectric material, mu is the shear stress of the piezoelectric material, dm bound to the excitation electrode specific The mass of the material, A, is the area of the excitation electrode. As can be seen from the above equation, the higher the initial value f ₀ of the resonance frequency of the piezoelectric vibrating reed, the larger the change df thereof, and the higher the sensitivity of the mass measuring device. For example, if the frequency f ₀ is increased from the conventional 27 MHz to 150 MHz, the sensitivity can be increased 30 times. To increase the frequency of the piezoelectric vibrating reed, the thickness of the vibrating portion of the piezoelectric vibrating reed may be reduced.
[0024]
FIG. 2 shows an explanatory diagram of the inverted mesa type piezoelectric vibrating reed. 2A is a plan view, and FIG. 2B is a side cross-sectional view taken along line AA of FIG. 2A. As the piezoelectric vibrating reed 20, a so-called inverted mesa type piezoelectric vibrating reed is used. The inverted-mesa type piezoelectric vibrating piece 20 is obtained by cutting a piezoelectric material such as quartz into a flat plate shape, forming a concave portion at the center of both surfaces thereof to reduce the thickness, and forming excitation electrodes 22a and 22b on both surfaces of the thin portion. . Connection electrodes 24a and 24b that are electrically connected to the excitation electrodes 22a and 22b are formed on the thick portion 21 on the periphery of the piezoelectric vibrating reed 20. Each electrode is composed of two layers of Au / Cr or Ag / Cr. In such an inverted-mesa type piezoelectric vibrating reed, the thick vibrating portion at the periphery protects the thin vibrating portion at the center, so that the vibrating portion can be prevented from being broken by an external force. Accordingly, a high-frequency piezoelectric vibrating reed can be used, and the sensitivity of the mass measuring device can be increased.
[0025]
Then, a sensitive film is applied to the surface of the excitation electrode 22a on the upper surface of the piezoelectric vibrating reed 20, and the piezoelectric vibrating reed 20 is arranged substantially horizontally. The sensitive membrane is a substance that binds only to the molecule of the specific substance to be detected, and is selected according to the specific substance.
[0026]
On the other hand, as shown in FIG. 1, a fixed-quantity ejection unit 30 for ejecting the sample solution is provided above the piezoelectric vibrating reed 20. A so-called ink-jet head is used as the constant-rate discharging means 30. It is to be noted that the constant-rate discharging means 30 may be any means capable of discharging a predetermined amount of the sample solution to a predetermined position, and any type of ink jet such as a piezo method, a bubble ink jet method, or a thermal ink jet method may be used. Therefore, in the case of a sample solution that is easily affected by heat, a piezo method may be adopted. In other cases, a bubble inkjet system or a thermal inkjet system that can simplify the head structure may be used.
[0027]
FIG. 3 is a side sectional view of a piezo type inkjet head. The ink jet head 30 mainly includes a glass substrate 32, a silicon substrate 36, and a nozzle plate 38 made of silicon or the like. An ink chamber 42 is formed between the silicon substrate 36 and the nozzle plate 38 to enclose a sample solution. A nozzle 39 is formed in the nozzle plate 38 adjacent to the ink chamber 42. On the other hand, the diaphragm 37 is formed by thinning the silicon substrate 36 constituting the wall surface of the ink chamber 42. Then, a piezo (piezoelectric) element 34 is arranged between the vibration plate 37 and the glass substrate 32. Note that driving electrodes 33 and 35 are arranged on both end surfaces of the piezo element 34. When a voltage is applied to the piezo element 34 by the driving electrodes 33 and 35, the piezo element expands. As a result, the vibration plate 37 compresses the ink chamber 42, and the sample solution in the ink chamber 42 is discharged from the nozzle 39.
[0028]
FIG. 4 shows a perspective view of the position control means. In order to dispose the excitation electrode of the piezoelectric vibrating piece 20 directly below the nozzle of the fixed-quantity discharge means 30, a position control means 50 is provided. The fixed-quantity discharge unit 30 is slidably attached to the shaft 56 and fixed to a timing belt or the like (not shown) so as to be movable in the X direction. On the other hand, the tray 52 on which the piezoelectric vibrating reed 20 is placed is slidably attached to the shaft 54, and is fixed to a timing belt or the like (not shown) so as to be movable in the Y direction. Further, there is provided an image recognition means 58 such as a CCD camera for detecting the position of both or one of the piezoelectric vibrating reed 20 and the quantitative discharge means 30.
[0029]
The specific procedure of the position control is as follows. First, the piezoelectric vibrating reed 20 is placed on the tray 52 and moved below the fixed-quantity discharging means 30. Next, the current position of the piezoelectric vibrating reed 20 is detected by imaging the piezoelectric vibrating reed 20 by the image recognition means 58. Then, the fixed-quantity discharging means 30 is moved in the X direction so that the excitation electrode of the piezoelectric vibrating piece 20 is located immediately below the nozzle of the fixed-quantity discharging means 30, and the tray 52 on which the piezoelectric vibrating piece 20 is placed is moved in the Y direction. Let it. Thus, the sample solution can be accurately ejected onto the excitation electrode. Note that the position control means may be configured to move the fixed-quantity discharge means in both the X and Y directions while fixing the position of the piezoelectric vibrating reed.
[0030]
By the way, the quartz crystal microbalance method needs to be performed at a predetermined temperature suitable for bonding the sensitive film and the specific substance. Therefore, a temperature adjusting means 18 for keeping the above-described piezoelectric vibrating reed 20 and the fixed-quantity discharging means 30 at a predetermined temperature is provided. As the temperature adjusting means 18, a thermostatic chamber capable of accommodating the piezoelectric vibrating reed 20 and the fixed quantity discharging means 30 is used. This makes it possible to efficiently and accurately maintain the entire fixed-quantity discharge unit 30 including the sample solution at a predetermined temperature. In addition, it is also possible to provide a heater or the like in each part of the piezoelectric vibrating reed 20 or the fixed-quantity discharge means 30, and to individually control the temperature.
[0031]
Then, as shown in FIG. 1, the piezoelectric vibrating reed 20 is connected to an external oscillation circuit 40. The oscillation circuit 40 energizes the excitation electrode of the piezoelectric vibrating reed 20 and causes the piezoelectric vibrating reed 20 to oscillate. The oscillation circuit 40 is connected to the frequency counter 5. The frequency counter 5 measures the resonance frequency of the piezoelectric vibrating reed 20. The frequency counter 5 is connected to a computer 6. The computer 6 calculates the mass of the specific substance attached to the excitation electrode 22a of the piezoelectric vibrating reed 20 from the resonance frequency measured by the frequency counter 5. In addition, it is preferable that the computer 6 be configured so as to analyze the presence / absence, concentration, and the like of the specific substance in the sample solution from a change with time of the attached amount of the specific substance.
[0032]
Next, a method of using the mass measuring device according to the first embodiment will be described.
As shown in FIG. 1, first, the piezoelectric vibrating reed 20 is disposed below the constant-rate discharging means 30. At this time, the position control means 50 controls the relative position between the piezoelectric vibrating reed 20 and the fixed-quantity discharging means 30, and arranges the excitation electrode 22 a on the upper side of the piezoelectric vibrating piece 20 directly below the nozzle of the fixed-quantity discharging means 30. Next, the temperature adjusting means 18 is operated to maintain the piezoelectric vibrating reed 20 and the quantitative discharge means 30 containing the sample solution at a predetermined temperature.
[0033]
In order to perform mass measurement, first, current is supplied from the oscillation circuit 40 to the piezoelectric vibrating reed 20 to cause the piezoelectric vibrating reed 20 to oscillate. Further, the resonance frequency of the piezoelectric vibrating reed 20 is continuously measured by the frequency counter 5. Next, the sample solution is discharged from the nozzle of the fixed-quantity discharging means 30 and is brought into contact with the excitation electrode 22 a on the upper side of the piezoelectric vibrating reed 20. When the sample solution comes into contact with the excitation electrode 22a, a specific substance in the sample solution binds to the sensitive film on the surface of the excitation electrode. Thereby, the mass of the excitation electrode 22a increases, and the resonance frequency of the piezoelectric vibrating piece 20 decreases. By analyzing the amount of decrease in the resonance frequency by the computer 6, the presence / absence and concentration of the specific substance can be calculated.
[0034]
In addition, if the discharge amount of the sample solution from the quantitative discharge unit 30 is set so that the sample solution contacts only the surface of the excitation electrode 22a, the sample solution does not contact the portion where the sensitive film is not applied. Thereby, the mass of the specific substance in the sample solution can be accurately grasped. On the other hand, since the quantitative discharge means 30 is used, the amount of the sample solution discharged to the excitation electrode can be accurately grasped. As described above, the concentration of the specific substance in the sample solution can be directly calculated, and the accuracy of mass measurement can be improved.
[0035]
With the mass measuring method and the mass measuring device according to the first embodiment described above in detail, it is possible to cope with high sensitivity.
That is, in the first embodiment, the quantitative measurement unit discharges the sample solution to the excitation electrode on the upper side of the piezoelectric vibrating reed to measure the mass. In this case, since there is no possibility of short-circuit with the lower excitation electrode, a covering member for sealing the lower excitation electrode from the sample solution is not required, and the manufacturing cost can be reduced. Further, a large amount of the sample solution is not required, and the mass measurement of the specific substance contained in the minute amount of the sample solution can be performed. In addition, since the discharge position and discharge amount of the sample solution can be accurately controlled, high-precision mass measurement is possible.
[0036]
Furthermore, since the sample solution contacts only a part of the piezoelectric vibrating reed, the oscillation of the piezoelectric vibrating reed is less hindered by the influence of the sample solution. Thus, even a high-frequency piezoelectric vibrating reed can be oscillated stably. Accordingly, it is possible to use a high-frequency piezoelectric vibrating reed, and it is possible to cope with higher sensitivity of mass measurement.
[0037]
Next, a second embodiment will be described.
5 and 6 are explanatory views of the piezoelectric vibrating reed used in the second embodiment. FIG. 5 is a side sectional view taken along the line CC of FIG. 6, FIG. 6A is a plan view, and FIG. 6B is a bottom view. In the mass measurement method according to the second embodiment, a plurality of sets of excitation electrodes 122a and 122b are formed on a piezoelectric vibrating reed 120, and a sensitive film is applied to the surface of each of the excitation electrodes 122a on one side of the piezoelectric vibrating reed 120. A method in which a sample solution is brought into contact with each of the excitation electrodes 122a to measure the mass of a specific substance in the sample solution, and the sample solution is sequentially discharged and brought into contact with each of the excitation electrodes 122a by a quantitative discharge means. Things. Note that the description of the same configuration as that of the first embodiment will be omitted.
[0038]
As shown in FIG. 5, the piezoelectric vibrating reed 120 used in the second embodiment is obtained by cutting out a piezoelectric material such as quartz into a flat plate shape, forming a plurality of concave portions at corresponding positions on both surfaces thereof, and reducing the thickness. Excitation electrodes 122a and 122b are formed on both front and back sides of the section. The portions where the pair of front and back excitation electrodes 122a and 122b are formed function as the vibrating portions 121, respectively.
[0039]
In the piezoelectric vibrating reed 120, on the front side shown in FIG. 6A, a plurality of connection electrodes 124a corresponding to the respective excitation electrodes 122a are formed on the periphery. On the other hand, on the back side shown in FIG. 6 (2), a common connection electrode 124b that is electrically connected to all the excitation electrodes 122b is formed on the periphery. When performing the mass measurement, the common connection electrode 124b on the back side is always connected to the oscillation circuit 40 shown in FIG. Then, the connection electrodes 124a on the front side corresponding to the vibrating section 121 for performing the mass measurement are sequentially connected to the oscillation circuit 40 to perform the mass measurement.
Then, on the surface of each of the excitation electrodes 122a on the front side of the piezoelectric vibrating reed 120, a sensitive film that binds to a different specific substance is applied.
[0040]
The relative position control between the piezoelectric vibrating reed and the quantitative discharge means is performed in the following procedure. First, instead of the piezoelectric vibrating reed 20 shown in FIG. 4, the above-described piezoelectric vibrating reed 120 is placed on the tray 52 and moved below the fixed-quantity discharging means 30. Next, the current position of the piezoelectric vibrating reed is detected by the image recognition means 58. Then, the fixed-quantity discharging unit 30 is moved in the X direction so that the excitation electrode of the vibrating unit for performing the mass measurement is located directly below the nozzle of the fixed-quantity discharging unit 30, and the tray 52 on which the piezoelectric vibrating reed is placed is moved in the Y direction. Move to This moving operation is performed for all of the vibrating sections for performing mass measurement. Thus, the sample solution can be accurately discharged onto the excitation electrode of each vibrating section for performing mass measurement.
[0041]
With the mass measuring method and the mass measuring device according to the second embodiment, it is possible to cope with a multi-sensor configuration.
That is, in the second embodiment, a plurality of sets of excitation electrodes are formed on the piezoelectric vibrating reed, a sensitive film is applied to the surface of each excitation electrode on one side of the piezoelectric vibrating reed, and a quantitative discharge means is applied to each of the excitation electrodes by the quantitative discharge means. The sample solution was sequentially discharged to measure the mass of the specific substance in the sample solution. This eliminates the need for a large covering member for isolating the lower excitation electrode from the sample solution, thereby reducing manufacturing costs. Further, even when a multi-sensor type piezoelectric vibrating reed having a plurality of vibrating parts is used, a large amount of a sample solution is not required, and the mass measurement of a specific substance contained in a minute amount of a sample solution can be performed. In addition, since the discharge position and discharge amount of the sample solution can be accurately controlled, high-precision mass measurement is possible. Accordingly, it is possible to cope with the multi-sensor mass measurement.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a mass measuring device according to a first embodiment.
FIG. 2 is an explanatory view of an inverted mesa type piezoelectric vibrating reed.
FIG. 3 is a side sectional view of a piezo type inkjet head.
FIG. 4 is an explanatory diagram of a position control unit.
FIG. 5 is a side sectional view of the multi-sensor type piezoelectric vibrating reed.
FIG. 6 is a plan view and a bottom view of the multi-sensor type piezoelectric vibrating reed.
FIG. 7 is an explanatory diagram of a conventional mass measuring chip.
FIG. 8 is an explanatory view of a conventional mass measuring device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Mass measuring device 5 ... Frequency counter 6 ... Computer 18 ... Temperature adjusting means 20 ... Piezoelectric vibrating reed 21 ... Thick parts 22a and 22b ... Exciting electrodes 24a and 24b ... Connection electrode 30 ... Quantitative discharge means 40 ... Oscillation circuit 50 ... Position control means

Claims (5)

A method of applying a sensitive film to the surface of the excitation electrode on one side of the piezoelectric vibrating reed, contacting the sample solution with the excitation electrode, and measuring the mass of a specific substance in the sample solution,
A mass measuring method, characterized in that a sample solution is discharged to and brought into contact with the excitation electrode by a quantitative discharge means. A plurality of sets of excitation electrodes are formed on the piezoelectric vibrating reed, a sensitive film is applied to the surface of each of the excitation electrodes on one side of the piezoelectric vibrating reed, and a sample solution is brought into contact with each of the excitation electrodes to form the sample solution. A method for measuring the mass of a specific substance in,
A mass measuring method, characterized in that a sample solution is sequentially discharged and brought into contact with each of the excitation electrodes by a quantitative discharge means. The mass measuring method according to claim 1 or 2,
A mass measuring method, wherein the specimen solution is discharged and brought into contact only with the surface of the excitation electrode. A device for measuring the mass of a specific substance in the sample solution by contacting the sample solution with the surface of the excitation electrode of the piezoelectric vibrating reed coated with the sensitive film,
A mass measuring apparatus comprising: a fixed amount discharging means for discharging a sample solution onto a surface of the excitation electrode. The mass measuring device according to claim 4,
A mass measuring device comprising a temperature adjusting means for maintaining the piezoelectric vibrating reed and the constant-rate discharging means at a predetermined temperature.

Images