JP4380087B2

JP4380087B2 - Flow cell

Info

Publication number: JP4380087B2
Application number: JP2001158052A
Authority: JP
Inventors: 健松原
Original assignee: Fuji Electric Systems Co Ltd
Current assignee: Fuji Electric Co Ltd
Priority date: 2001-05-28
Filing date: 2001-05-28
Publication date: 2009-12-09
Anticipated expiration: 2021-05-28
Also published as: JP2002350333A

Description

【０００１】
【発明の属する技術分野】
本発明は、例えば飲料水や生体試料などを化学分析する測光分析計に適用するフローセルに関する。
【０００２】
【従来の技術】
飲料水や生体試料など液体の化学分析に用いる吸光度測定では、液体試料をフローセルの内部に流し、そのセル側面に開口した測光窓を通して発光部から出射した光を液体流路に入射し、反対側の測光窓を通して受光部で受光するようにしている。
【０００３】
また、そのフローセルの従来構造では、例えば特開平１０−１１１２３５号公報で開示されているように、セル内に画成した液体試料の流路を挟んでその両側の側面に開口した測光窓を通じて発光部と受光部の間に光路を形成し、かつ測光窓には光透過性に優れた石英ガラスなどにより液体流路と発光部，受光部との間を液密にシールするようにしており、さらに測光窓にワイパーを付設して液体試料の成分が付着した測光窓の汚れをワイパーの操作で排除するようにしている。
【０００４】
【発明が解決しようとする課題】
前記した従来構造のフローセルでは、液体試料に含まれる成分がフローセルの内壁面に付着し、これを長期に亘って放置すると測光窓に配した石英ガラスの光透過性が劣化して測定精度が低下するようになることから、メンテナンス作業として定期的にセル内の洗浄，および測光窓のワイピングを行って清浄な状態に維持するようにしている。
【０００５】
ところで、フローセルの測光窓をワイピングするには、ワイパー，洗浄ブラシなどの付属機構を要して大型化するほか、そのワイピング作業にも手間がかかるなど、コストおよび保守管理面に問題があつた。
本発明は上記の点に鑑みなされたものであり、従来構造のフローセルの測光窓に配した石英ガラスを省略し、測光窓への試料成分の付着，汚れに対するワイピングを不要にしてセルの小形化，メンテナンスフリーを実現したフローセルを提供することを目的とする。
【０００６】
【課題を解決するための手段】
上記目的を達成するために、本発明によれば、セル内に画成した液体試料の流路を挟んでその両側に発光部および受光部を配し、かつ発光部と受光部との間の光路に対応して流路に接するセル内の側壁に測光窓を開口した構成になるフローセルにおいて、前記測光窓を微小な貫通穴とした上で穴内壁面を撥水処理し、その撥水処理面の表面張力と流路側の液体圧力との釣合いにより、測光窓の内側への液体浸入を防止するように構成する。
【０００７】
そして、本発明によれば、周囲温度変化に伴うセル内圧力，液体試料の圧力変化などに対して、前記した液体浸入防止機能を安定確保させるために、発光部および受光部と測光窓の裏面側との間に、外気に対して封止された小室を画成するとともに、該小室の室内空間を加熱するヒータ，および流路側の圧力と小室内の圧力との差圧を検出する圧力センサを設け、該圧力センサの検出信号を基に、前記加熱ヒータの発熱制御により小室内の気体圧力を調整して液体が流路側から測光窓を通じて小室に流入することを防止するようにする（請求項１）。
その具体的な態様として、前記の小室を発光部および受光部を搭載した基板と測光窓を開口して前記基板と重ね合わせたシリコン基板との間に画成し、かつ圧力センサおよびヒータをそれぞれ半導体式圧力センサ，および薄膜ヒータとして前記シリコン基板の基板上に作り込んで構成する（請求項２）。
【０００８】
上記の構成により、撥水加工を施した測光窓における表面張力に対して、セル内の流路を流れる試料の液体圧力が小さい範囲では、液体圧力と表面張力との釣合いにより、液体流路側から測光窓を通じて発光部，受光部側に液体が浸入することが阻止される。
また、測光窓部における表面張力に対して流路側の液体圧力が大きい場合でも、前記の圧力センサで検出した差圧信号を基に、ヒータの加熱により測光窓の内側に画成した小室の圧力を高めるように制御することで、流路側からの液体浸入を防止できる。
【０００９】
【発明の実施の形態】
以下、本発明の実施の形態を図示実施例に基づいて説明する。
〔実施例１〕
図１(a),(b) はフローセルの構造を示すものである。図において、１は発光素子、２は受光素子、３は発光素子１，受光素子２を搭載したガラス基板、３ａはガラス基板３の内側に形成した凹状の小室、４は板面に微小な測光窓穴４ａを開口したシリコン基板、５は液体試料を流す流路６を画成するガラス基板であり、前記の発光素子１，受光素子２および測光窓穴４ａが一直線上に並ぶように各基板３，４，５を重ね合わせ、その相互間を結合してフローセルを構成している。
【００１０】
また、前記シリコン基板４に開口した測光窓穴４ａは、外側から流路６に向けて縮小したテーパ状の穴として、流路側から窓穴の中に液体が浸入し難い形状となし、さらにその測光窓穴４ａの内壁面にはフッ素樹脂などで撥水処理を施して液体の濡れ性が低い撥水層７が形成されている。なお、図１(b) のセル組立状態では、測光窓４ａの裏面側に画成されている小室３ａの空間は周囲の外気に対して封止された空間となる。
【００１１】
ここで、前記の測光窓穴４ａを円形穴として、その窓穴の半径をｒ、流路６に通流する試料液体の表面張力をγ、撥水処理を施した窓穴の内壁面と液体との接触角をβ、小室３ａ（小室には空気が封じ込められている）の内圧をＰ_g、流路６の液体圧力Ｐ_lとすると、流路６から測光窓穴４ａを通じて背後の小室３ａに試料液体が浸入しない条件は、毛細管力と小室内圧力と流路内圧力との釣合いから、次式(1),(2) によって決まる。
【００１２】
【式１】
πｒ²Ｐ_g＋２πｒγ・ｃｏｓθ＞Ｐ_l（πｒ²） ………(1)
【００１３】
【式２】
ｒ＜（２γ・ｃｏｓθ）／（Ｐ_l−Ｐ_g） ………(2)
そして、上式(2) を基に、圧力差（流路６と小室３ａとの相対圧）と測光窓穴４ａの開口部最大半径との関係をプロットして表すと図２のようになる。
【００１４】
すなわち、流路６と小室３ａとの相対圧（差圧）に対して撥水処理を施した測光窓穴４ａの穴径を図２に表した特性線以下に設定する、あるいは流路６の液体圧力に対応して小室３ａの内圧を後記の実施例２で述べるように調整制御すれば、表面張力と液体圧力との釣合いによって流路６から測光窓穴４ａを通じて小室３ａに試料液体が浸入しなくなる。
【００１５】
したがって、この封止手段をフローセルの測光窓穴４ａに適用することにより、従来構造のように石英ガラスで測光窓を液密シールしたり、測光窓に付着した試料の汚れを清掃するために行うワイピングが不要となり、フローセルのメンテナンスフリー化が実現できる。
〔実施例２〕
次に、前記実施例１をさらに改良した実施例の構成を図３で説明する。この実施例では、発光素子１，受光素子２を搭載したガラス基板３と測光窓穴４ａを開口したシリコン基板４との間に画成された小室３ａに対して、シリコン基板４の基板上には半導体式圧力センサ８，および薄膜ヒータ９が作り込まれている。
【００１６】
すなわち、当該フローセルを使って液体試料の化学分析を行っている状態で、
周囲温度の変化に伴う小室３ａ内の圧力変動、あるいは試料液体の脈動によって測光窓穴４ａにおけるメニスカス（毛細管の液体表面がつくる球面状の表面）が変化すると、発光素子１と受光素子２との間の光路が微妙に変化し、これが受光素子の検出信号にノイズとして現れてフローセルの測定精度を低下させる。
【００１７】
そこで、この実施例では、前記のようにシリコン基板４の裏面側に作り込んだ半導体式圧力センサ８および薄膜ヒータ９を用い、圧力センサ８の検出信号を基にしたフィードバック制御によりヒータ９を通電制御し、小室３ａに封じ込められている気体（空気）の温度，したがってその室内圧力（気体圧）を流路６の液体圧力に対応して可変調整して、流路６側から液体が測光窓穴４ａを通じて小室３ａに浸入しないようにしている。
【００１８】
ここで、前記圧力センサ８はシリコン基板４の一部に形成したダイヤフラム８ａの上にピエゾ抵抗８ｂを形成し、流路６側の圧力と小室３ａの内圧との圧力差に応動するダイヤフラム８ａの歪みをピエゾ抵抗８ｂの抵抗値変化して差圧を検出する。そして、圧力センサ８の出力信号を基に、薄膜ヒータ９に流す電流をフィードバック制御することにより、小室３ａ内の気体温度を変えて、先記の(2)式，および測光窓穴におけるメニスカスの形状を一定に維持する条件を満たす圧力を発生させる。なお、差圧，温度の変動に対する制御の応答性を高めるためには、小室３ａの容積はできるだけ小さい方が望ましい。また、薄膜ヒータ９は、基板側への熱放散をできるだけ抑えるために、シリコン基板４と熱絶縁するのがよい。
【００１９】
次に、実施例１で述べたフローセルの製造方法を図４，図５で説明する。まず、シリコン基板４の加工工程を図４(a) 〜(c) に示す。すなわち、面方位（100)の単結晶シリコン基板４（(a) 図参照）の表面にシリコン酸化膜１０を形成した上で、測光窓穴４に対応するマスクをフォトリソグラフイーによりパターニングする（(b) 図参照）。次に、K0H などシリコンの結晶異方性エッチヤントによりシリコン基板４にテーパ形状の測光窓穴４ａを加工する（(c) 図参照）。なお、シリコンの結晶異方性エッチングを行う場合は窓穴４ａの形状は図１(a) で示すような角穴とするが、ドライエッチング法により円形状の窓穴にテーパをつけることも可能である。そして、エッチング処理の後はシリコン酸化膜１０をバッファードふっ酸により洗浄して除去する。
【００２０】
一方、受光素子１，受光素子２（図１参照）を搭載するガラス基板３の加工は、図５(a),(b) で示すように、ガラス基板３に取付ける発光素子（発光ダイオード），受光素子、あるいはこれに代わる光ファイバなどの外形サイズに合わせて、ガラス基板３の表面にフォトレジストのマスク１１を作っておき（(a) 図参照）、サンドブラスト法などにより両面から小室３ａとなる凹所，および発光素子，受光素子の装着穴３ｂを加工する（(b) 図参照）。
【００２１】
そして、前記の加工方法で作製した各基板を図１で示すように組合せて積層した上で各基板の相互間を接合する。なお、この接合方法としては、例えば、各基板を４００℃程度まで加熱して密着させた上で、ガラス基板３と５との間に電圧を印加する陽極接合法が採用できる。
次に、実施例２で述べたシリコン基板４の製造方法を図６(a) 〜(e) で説明する。まず、(a) 図に示すシリコン基板４の表面にフォトレジストにより圧力センサ８のピエゾ抵抗８ａに対応するマスク、および薄膜ヒータ９に対応するマスクをパターン形成した上で、イオン注入法などによりホウ素を高濃度に拡散してピエゾ抵抗８ｂ，薄膜ヒータ９を作り込む。なお、薄膜ヒータ９は白金などの金属をシリコン基板４の表面に成膜しても良い。続いて、ピエゾ抵抗８ｂ，薄膜ヒータ９の電極や配線の導体パターンを形成した後、シリコン基板４の表裏両面にシリコン酸化膜１０を形成した上で、測光窓穴４ａおよび圧力センサ８のダイヤフラム８ａに対応するマスクをパターニングする（(b) 図参照）。次に、シリコン基板４の裏面側から反応性イオンエッチング法などによりエッチングして測光窓穴４ａの半開穴４ａ-1，および薄肉なダイヤフラム８ａを残しての凹所８ａ-1を形成する（(c) 図参照）。なお、前記ダイヤフラム部８ａの肉厚は、目標とする圧力センサ感度から定めてエッチング時間により調整する。続いて、シリコン基板４の表面側からも同様な方法でエッチングを行い、先に裏面側から加工した半開穴４ａ-1と貫通させた上で、さらに貫通穴のコーナーからエッチングを進めてテーパ状の測光窓穴４ａを完成する（(d) 図参照）。最後に、シリコン酸化膜１０を除去して圧力センサ８および薄膜ヒータ９が作り込まれたシリコン基板４が完成する（(e) 図参照）。そして、実施例１と同様にガラス基板３，５と組合せて積層，接合することにより図３に示したフローセルが完成する。
【００２２】
【発明の効果】
以上述べたように、本発明によれば、セル内に画成した液体試料の流路を挟んでその両側に発光部および受光部を配し、かつ発光部と受光部との間の光路に対応して流路に接するセル内の側壁に測光窓を開口した構成になるフローセルにおいて、前記測光窓を微小な貫通穴とした上で穴内壁面を撥水処理し、その撥水処理面の表面張力と流路側の液体圧力との釣合いにより、測光窓の内側への液体浸入を防止するようにしたことにより、従来構造のフローセルでその測光窓に配した石英ガラスの省略、および測光窓への試料成分の付着，汚れに対するワイピングを不要にしてフローセルの小形化，メンテナンスフリー化が図れる。
【００２３】
また、周囲温度，流路の液体圧力の変動に対しても、圧力センサで検出した差圧信号を基に、ヒータの加熱により測光窓の内側に画成した小室の圧力を高めるように制御することで、流路側からの液体浸入を防止できる。
【図面の簡単な説明】
【図１】本発明の実施例１に係るフローセルの構成図であり、(a) は分解斜視図、(b) は組立状態での要部の拡大断面図
【図２】図１(b) における液体流路／セル内小室の圧力差とこれに表面張力が釣り合う測光窓穴の最大半径との関係図
【図３】本発明の実施例２に係るフローセルの要部構造の断面図
【図４】図１におけるシリコン基板の製造方法の説明図であり、(a）〜(c) はその加工工程図
【図５】図１におけるガラス基板の製造方法の説明図であり、(a),(b) はその加工工程図
【図６】図３におけるシリコン基板の製造方法の説明図であり、(a) 〜(e) はその加工工程図
【符号の説明】
１発光素子
２受光素子
３ガラス基板
３ａ小室
４シリコン基板
４ａ測光窓穴
６液体流路
７撥水層
８半導体式圧力センサ
９薄膜ヒータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow cell applied to a photometric analyzer that chemically analyzes, for example, drinking water or a biological sample.
[0002]
[Prior art]
In absorbance measurement used for chemical analysis of liquids such as drinking water and biological samples, the liquid sample is flowed into the flow cell, the light emitted from the light emitting part is incident on the liquid channel through the photometric window opened on the side of the cell, and the opposite side The light receiving unit receives light through the photometric window.
[0003]
Further, in the conventional structure of the flow cell, for example, as disclosed in JP-A 10-111235, JP-emitting through photometric window that opens on the side surface of both sides of the flow path of the liquid sample defining in the cell An optical path is formed between the light-receiving part and the light-receiving part, and the light-measuring window is liquid-tightly sealed between the liquid flow path, the light-emitting part, and the light-receiving part with quartz glass having excellent light transmittance. Further, a wiper is attached to the photometric window so that dirt on the photometric window to which the components of the liquid sample have adhered is removed by operating the wiper.
[0004]
[Problems to be solved by the invention]
In the conventional flow cell described above, the components contained in the liquid sample adhere to the inner wall surface of the flow cell, and if this is left for a long period of time, the light transmittance of the quartz glass placed in the photometric window deteriorates and the measurement accuracy decreases. Therefore, as maintenance work, the cell is regularly cleaned and the photometric window is wiped to maintain a clean state.
[0005]
By the way, in order to wipe the photometric window of the flow cell, there is a problem in terms of cost and maintenance management, such as requiring an attachment mechanism such as a wiper and a cleaning brush to increase the size, and taking time and effort for the wiping work.
The present invention has been made in view of the above points, and omits the quartz glass disposed in the photometric window of the flow cell having the conventional structure, thereby reducing the size of the cell by eliminating the need for wiping against the sample component adhering to the photometric window and contamination. The purpose is to provide a flow cell that is maintenance-free.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a light emitting part and a light receiving part are arranged on both sides of a flow path of a liquid sample defined in a cell, and between the light emitting part and the light receiving part. In a flow cell having a structure in which a photometric window is opened on the side wall of the cell that contacts the flow path corresponding to the optical path, the inner wall surface of the hole is subjected to water repellent treatment after the photometric window is formed as a minute through hole, and the water repellent treated surface thereof the balance between the surface tension and the flow fluid pressure of the roadside, configured to prevent liquid from entering the inside of the photometric window.
[0007]
And according to this invention, in order to ensure the above-mentioned liquid penetration prevention function stably with respect to the pressure in a cell accompanying the ambient temperature change, the pressure change of a liquid sample, etc., the light emission part, the light-receiving part, and the back surface of a photometry window And a heater for heating the indoor space of the small chamber, and a pressure sensor for detecting a differential pressure between the pressure on the flow path side and the pressure in the small chamber the provided, based on the detection signal of the pressure sensor, so as to prevent the flow into the chamber through the metering window from the adjustment to the liquid flow path side gas pressure of the small chamber by controlling heat generation of said heater (according Item 1 ).
As a specific aspect thereof, the small chamber is defined between a substrate on which a light emitting unit and a light receiving unit are mounted and a silicon substrate that is overlapped with the substrate by opening a photometric window, and a pressure sensor and a heater, respectively. semiconductor pressure sensor, and a thin film heater constituting crowded created on a substrate of said silicon substrate (claim 2).
[0008]
With the above configuration, in the range where the liquid pressure of the sample flowing through the flow path in the cell is small relative to the surface tension in the photometric window subjected to the water repellent finish, the liquid flow path side causes a balance between the liquid pressure and the surface tension. The liquid is prevented from entering the light emitting unit and the light receiving unit through the photometric window.
Even when the liquid pressure on the flow path side is larger than the surface tension in the photometric window, the pressure in the small chamber defined inside the photometric window by heating the heater based on the differential pressure signal detected by the pressure sensor. By controlling so as to increase the flow rate, liquid intrusion from the flow path side can be prevented.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the illustrated examples.
[Example 1]
Figure 1 (a), (b) shows a structure of the flow cell. In the figure, 1 is a light-emitting element, 2 is a light-receiving element, 3 is a glass substrate on which the light-emitting element 1 and the light-receiving element 2 are mounted, 3a is a concave chamber formed inside the glass substrate 3, and 4 is a minute photometry on the plate surface. A silicon substrate 5 having an opening in the window hole 4a is a glass substrate that defines a flow path 6 through which a liquid sample flows, and each of the substrates has the light emitting element 1, the light receiving element 2, and the photometric window hole 4a aligned in a straight line. Three, four, and five are overlapped and connected to each other to form a flow cell.
[0010]
Further, the photometric window hole 4a opened in the silicon substrate 4 is formed as a tapered hole that is reduced from the outside toward the flow path 6 and has a shape in which liquid does not easily enter the window hole from the flow path side. On the inner wall surface of the photometric window hole 4a, a water repellent layer 7 having a low liquid wettability is formed by performing a water repellent treatment with a fluororesin or the like. In the cell assembled state of FIG. 1 (b), the space of the small chamber 3a defined on the back side of the photometric window 4a is a space sealed against the ambient air.
[0011]
Here, the photometric window hole 4a is a circular hole, the radius of the window hole is r, the surface tension of the sample liquid flowing through the flow path 6 is γ, the inner wall surface of the window hole subjected to water repellent treatment and the liquid , The internal pressure of the small chamber 3a (air is contained in the small chamber) is P _g , and the liquid pressure P _l of the flow path 6 is the small chamber 3a behind the flow path 6 through the photometric window hole 4a. The conditions under which the sample liquid does not enter are determined by the following equations (1) and (2) based on the balance between the capillary force, the pressure in the small chamber, and the pressure in the flow path.
[0012]
[Formula 1]
πr ² P _g + 2πrγ · cos θ> P _l (πr ² ) (1)
[0013]
[Formula 2]
r <(2γ · cos θ) / (P ₁ −P _g ) (2)
Based on the above equation (2), the relationship between the pressure difference (relative pressure between the flow path 6 and the small chamber 3a) and the maximum radius of the opening of the photometric window hole 4a is plotted and expressed as shown in FIG. .
[0014]
That is, the hole diameter of the photometric window hole 4a subjected to water repellent treatment with respect to the relative pressure (differential pressure) between the flow path 6 and the small chamber 3a is set to be equal to or smaller than the characteristic line shown in FIG. if adjustment control as described in response to fluid pressure chamber 3a internal pressure the examples below 2, the sample liquid in chamber 3a through the photometric window hole 4a from Thus the channel 6 to balance the surface tension and the liquid pressure It will not penetrate.
[0015]
Therefore, by applying this sealing means to the photometric window hole 4a of the flow cell, the photometric window is liquid-tightly sealed with quartz glass as in the conventional structure, or the sample adhering to the photometric window is cleaned. Wiping is not required, and the flow cell can be made maintenance-free.
[Example 2]
Next, a configuration of an embodiment obtained by further improving the embodiment 1 will be described with reference to FIG. In this embodiment, the small chamber 3a defined between the glass substrate 3 on which the light emitting element 1 and the light receiving element 2 are mounted and the silicon substrate 4 having the photometric window hole 4a is opened on the substrate of the silicon substrate 4. The semiconductor type pressure sensor 8 and the thin film heater 9 are built in.
[0016]
That is, in the state of performing a chemical analysis of a liquid sample using the flow cell,
When the meniscus (spherical surface created by the liquid surface of the capillary tube) in the photometric window hole 4a changes due to pressure fluctuations in the small chamber 3a due to changes in the ambient temperature or pulsation of the sample liquid, the light emitting element 1 and the light receiving element 2 The optical path in between changes slightly, and this appears as noise in the detection signal of the light receiving element, thereby reducing the measurement accuracy of the flow cell.
[0017]
Therefore, in this embodiment, the semiconductor pressure sensor 8 and the thin film heater 9 formed on the back side of the silicon substrate 4 as described above are used, and the heater 9 is energized by feedback control based on the detection signal of the pressure sensor 8. The temperature of the gas (air) confined in the small chamber 3a, and therefore the pressure inside the chamber (gas pressure) is variably adjusted according to the liquid pressure in the flow path 6 so that the liquid can be measured from the flow path 6 side. The small chamber 3a is prevented from entering through the hole 4a.
[0018]
Here, the pressure sensor 8 includes a piezoresistor 8b formed on a diaphragm 8a formed on a part of the silicon substrate 4, and a diaphragm 8a that responds to a pressure difference between the pressure on the channel 6 side and the internal pressure of the small chamber 3a. The differential pressure is detected by changing the resistance value of the piezoresistor 8b. Based on the output signal of the pressure sensor 8, the current flowing through the thin film heater 9 is feedback controlled to change the gas temperature in the small chamber 3 a, and the above equation (2) and the meniscus in the photometric window hole A pressure is generated that satisfies the condition for maintaining the shape constant. It should be noted that the volume of the small chamber 3a is preferably as small as possible in order to increase the control response to the variation of the differential pressure and temperature. The thin film heater 9 is preferably thermally insulated from the silicon substrate 4 in order to suppress heat dissipation to the substrate side as much as possible.
[0019]
Next, the flow cell manufacturing method described in the first embodiment will be described with reference to FIGS. First, the processing steps of the silicon substrate 4 are shown in FIGS. 4 (a) to 4 (c). That is, after a silicon oxide film 10 is formed on the surface of a single crystal silicon substrate 4 (see FIG. (A)) with a plane orientation (100), a mask corresponding to the photometric window hole 4 is patterned by photolithography (( b) See figure). Next, the photometric window hole 4a having a tapered shape is processed in the silicon substrate 4 by crystal anisotropic etching of silicon such as K0H (see FIG. 4C). When performing crystal anisotropic etching of silicon, the shape of the window hole 4a is a square hole as shown in FIG. 1 (a), but it is also possible to taper the circular window hole by dry etching. It is. After the etching process, the silicon oxide film 10 is removed by washing with buffered hydrofluoric acid.
[0020]
On the other hand, the processing of the glass substrate 3 on which the light receiving element 1 and the light receiving element 2 (see FIG. 1) are mounted, as shown in FIGS. 5 (a) and 5 (b), a light emitting element (light emitting diode) attached to the glass substrate 3, A photoresist mask 11 is made on the surface of the glass substrate 3 in accordance with the external size of the light receiving element or an optical fiber instead of the light receiving element (see FIG. (A)), and the chamber 3a is formed from both sides by sandblasting or the like. The recess and the mounting hole 3b for the light emitting element and the light receiving element are processed (see FIG. 5B).
[0021]
And each board | substrate produced with the said processing method is combined and laminated | stacked as shown in FIG. 1, Then, each board | substrate is joined. As the bonding method, for example, an anodic bonding method in which a voltage is applied between the glass substrates 3 and 5 after each substrate is heated to about 400 ° C. and brought into close contact can be employed.
Next, a method for manufacturing the silicon substrate 4 described in the second embodiment will be described with reference to FIGS. First, a mask corresponding to the piezoresistor 8a of the pressure sensor 8 and a mask corresponding to the thin film heater 9 are formed on the surface of the silicon substrate 4 shown in FIG. Is diffused in a high concentration to form a piezoresistor 8b and a thin film heater 9. The thin film heater 9 may be formed of a metal such as platinum on the surface of the silicon substrate 4. Subsequently, after forming a piezoresistor 8b, a conductive pattern for the electrodes of the thin film heater 9 and wiring, and forming silicon oxide films 10 on both the front and back surfaces of the silicon substrate 4, the photometric window hole 4a and the diaphragm 8a of the pressure sensor 8 are formed. Pattern the mask corresponding to (see (b) figure). Next, etching is performed from the back side of the silicon substrate 4 by a reactive ion etching method or the like to form a semi-opening hole 4a-1 of the photometric window hole 4a and a recess 8a-1 leaving a thin diaphragm 8a (( c) See figure). The thickness of the diaphragm 8a is determined from the target pressure sensor sensitivity and is adjusted by the etching time. Subsequently, etching is performed in the same manner from the front surface side of the silicon substrate 4, penetrating through the semi-open hole 4a-1 previously processed from the back surface side, and further etched from the corner of the through hole to be tapered. The photometric window hole 4a is completed (see (d) figure). Finally, the silicon oxide film 10 is removed to complete the silicon substrate 4 on which the pressure sensor 8 and the thin film heater 9 are formed (see FIG. 4E). Then, the flow cell shown in FIG. 3 is completed by laminating and bonding in combination with the glass substrates 3 and 5 as in the first embodiment.
[0022]
【The invention's effect】
As described above, according to the present invention, the light emitting part and the light receiving part are arranged on both sides of the flow path of the liquid sample defined in the cell, and the light path between the light emitting part and the light receiving part is provided. Correspondingly, in a flow cell having a structure in which a photometric window is opened on the side wall in the cell that is in contact with the flow path, the hole inner wall surface is subjected to water repellent treatment after the photometric window is formed as a minute through hole, and the surface of the water repellent treated surface By preventing the liquid from entering the photometric window by balancing the tension and the liquid pressure on the flow path side, the quartz glass placed in the photometric window in the conventional flow cell is omitted, and the photometric window This eliminates the need for wiping against sample component adhesion and contamination, making the flow cell smaller and maintenance-free.
[0023]
Also, with respect to fluctuations in the ambient temperature and the liquid pressure in the flow path, control is performed to increase the pressure in the small chamber defined inside the photometric window by heating the heater based on the differential pressure signal detected by the pressure sensor. Thus, liquid intrusion from the channel side can be prevented.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a flow cell according to a first embodiment of the present invention, where (a) is an exploded perspective view, and (b) is an enlarged cross-sectional view of a main part in an assembled state. FIG. 3 is a cross-sectional view of the main structure of a flow cell according to Embodiment 2 of the present invention. FIG. 3 is a relationship diagram of the pressure difference between the liquid flow path / cell chamber in the cell and the maximum radius of the photometric window hole in which the surface tension is balanced. 4 is an explanatory diagram of a method for manufacturing a silicon substrate in FIG. 1, and (a) to (c) are diagrams illustrating the processing steps. FIG. 5 is an explanatory diagram of a method for manufacturing a glass substrate in FIG. (b) is the process diagram [FIG. 6] It is explanatory drawing of the manufacturing method of the silicon substrate in FIG. 3, (a)-(e) is the process diagram [description of code]
DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Light receiving element 3 Glass substrate 3a Small chamber 4 Silicon substrate 4a Photometric window hole 6 Liquid flow path 7 Water repellent layer 8 Semiconductor type pressure sensor 9 Thin film heater

Claims

A light emitting part and a light receiving part are arranged on both sides of the flow path of the liquid sample defined in the cell, and the side wall in the cell is in contact with the flow path corresponding to the optical path between the light emitting part and the light receiving part. In the flow cell having a configuration in which the photometric window is opened, the hole inner wall surface is subjected to water repellent treatment after the photometric window is formed as a minute through hole, and the balance between the surface tension of the water repellent treated surface and the liquid pressure on the flow path side, The flow cell is configured to prevent liquid from entering inside the photometric window, and defines a small chamber sealed against the outside air between the light emitting unit and the light receiving unit and the back side of the photometric window, A heater for heating the indoor space of the small chamber and a pressure sensor for detecting a differential pressure between the pressure on the flow path side and the pressure in the small chamber are provided, and the small heater is controlled by heat generation control of the heater based on the detection signal of the pressure sensor. Adjust the gas pressure in the room to measure the liquid from the flow path side. Flow cell being characterized in that so as to prevent the flow into the chamber through.

2. The flow cell according to claim 1 , wherein the chamber is defined between a substrate on which the light emitting unit and the light receiving unit are mounted and a silicon substrate that is opened with a photometric window and is overlapped with the substrate, and the heater is a thin film heater, A flow cell characterized in that a pressure sensor is formed as a semiconductor pressure sensor on the silicon substrate.