JPH04152249A - Biochemical sensor with optical wave-guide path diffraction lattice - Google Patents

Abstract

PURPOSE:To facilitate fabrication of a sensor and enhance the sensitivity and processing accuracy by lowering the refraction factor of a material to an optical wave guide path, and heightening the refraction factor of material to a diffraction lattice. CONSTITUTION:An optical wave guide path 6 and a diffraction lattice 7 are made from different materials, and their respective characteristics are optimized. The material of the optical wave guide path 6 shall have a refraction factor as small as 1.45-1.55 so as to sink the loss of the wave guide beam 4, and a change in the wave guide path characteristic is suppressed, which is due to change in the clad 5 generated when used as a sensor. The material of the diffraction lattice 7 shall have a redraction factor as large as 1.85 so as to enlarge the difference in the refraction factor value from the aqueous solution which is a chief object to be sensed, and the wave guide beam exciting efficiency in the diffraction lattice 7 is increased. Further the easiness in processing is enhanced to a great extent by subjecting the material of diffraction lattice 7 to photo-resist or electron beam resist process. This facilitates fabrication of sensor and enhances the sensitivity and processing accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a biochemical sensor using a diffraction grating structure attached to an optical waveguide.

[Prior Art] The following are well known biochemical sensors using optical waveguides. That is, the Swiss group used the sol-gel method to create S j 0 with a thickness of about 1100 nm.
A thin film of a mixture of 2 and Ti1t was prepared on a glass substrate, and a commercially available diffraction grating was pressed onto the thin film while it was still soft to form a thin film optical waveguide (2) having a relief (1) of the diffraction grating with a diameter of about 2 mm. prepared (e.g., W, Lukos
z and K, Tiefenthaler, 5ens
ors and actuators, is
f19+181 273-284) The angle θ at which the laser beam (3) can be incident on the diffraction grating portion of this thin film optical waveguide as shown in Fig. 1 and the guided light can be excited is determined by the angle θ of the cladding portion (5) as shown in Fig. 2. It strongly depends on the refractive index nc. Therefore, when the refractive index nc of the cladding part (5) changes due to adsorption of proteins, ions, etc. to the diffraction grating part (1), the intensity (4) of the guided light changes. This can be used to create biochemical sensors. but,
At present, this optical waveguide grating biochemical sensor has the following four drawbacks.

1. Since the diffraction grating (1) is produced by pressing the diffraction grating base material, it is difficult to produce a homogeneous and high quality diffraction grating, and the operation is troublesome.

2. The refractive index of the SiO2TiO mixed film that becomes the optical waveguide (2) and the refractive index of the diffraction grating part (1) are equal, and at most 1.
8, the intensity of the excitation guided light when it comes into contact with the sample solution is small.

3. Because the sol-gel method is used, it is difficult to produce high-quality optical waveguides. In particular, the reagents used in the sol-gel method tend to react with moisture in the air, so it is difficult to produce high-quality optical waveguides, especially in Japan. A device is required to avoid moisture, and often only films with high attenuation of guided light can be obtained.

4. Since the material of the optical waveguide (2) and the material of the diffraction grating part (1) are the same, the influence of light absorbing substances and light scattering substances adsorbed on parts other than the diffraction grating part (11) is large, and the optical waveguide part ( 2
) It is necessary to cover the vicinity of the diffraction grating portion (1) with another material.

Further, as described below, in order to configure the present invention,
A resist material with a high refractive index and excellent operability (
It is essential to fabricate a thin film using photoresist or electron beam resist, but there has been no such material in the past.6 [Problems to be Solved by the Invention] The present invention aims to The purpose of this study is to solve the drawbacks of biochemical sensors and provide a method for fabricating optical waveguide grating biochemical sensors that are easy to fabricate, have high sensitivity, and have high processing precision. Another object of the present invention is to develop a resist thin film with a high refractive index, which is essential to the present invention.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, the optical waveguide portion (6) and the diffraction grating portion (7) are made of different materials,
Optimize each characteristic. The optical waveguide section (6) is made of a material with a small refractive index of 1.45 to 1.55 to guide the guided light (
4) The first diffraction grating section (7) is made of a material with a large refractive index of 185 or more, and the main The difference in refractive index with the aqueous solution that is the object of sensing is increased to increase the waveguide light excitation efficiency in the diffraction grating section (7).Furthermore, the material of the diffraction grating section (7) is photoresist or electron beam resist. This was possible for the first time by utilizing the following fact that we discovered: Thin films of polytungstens, which are both inorganic photoresist materials and electron beam resist materials. The refractive index varies from about 17 to more than 2.0 depending on the drying time. Therefore, for example, by using three-beam interferometry, the refractive index can be reduced to 2.0.
Diffraction gratings can be easily made from the materials listed above.

In addition, during the process of synthesizing polytungstic acid, excess H
Conventionally, a platinum catalyst was used to remove 2O2, which made it difficult to determine the end point and often made it difficult to obtain a high-quality photoresist or a high-quality electron beam resist. The synthesis method is improved by removing the H2O2.

[Function] By making the diffraction grating part (7) and the optical waveguide part (6) from different materials in this way, the characteristics of each part can be optimized, the sensitivity of the sensor is increased, and the manufacturing process can be standardized. As a result, variations between products have been significantly reduced. Furthermore, since the diffraction grating portion (7) is made of a photoresist material having a high refractive index or an electron beam resist material having a high refractive index, processing of the single diffraction grating portion (7) is facilitated. Furthermore, improvements were made to the synthesis method for polytungstens, making it easier to obtain photoresist thin films with a high refractive index.

[Example] The present invention will be explained in more detail below using Examples.

Example 1 Since it is essential in the present invention to make the polytungsten NM have a refractive index of 185 or more and to easily synthesize the polytungsten #, this example uses a thin film of polytungstic acid. We will describe the fabrication method. There are various polytungstic acids, and here we will discuss in detail isopolyungsten M (hereinafter abbreviated as W-rPA), but other polytungstens, such as heteropolytungsten M (hereinafter abbreviated as W-HPA). But it's the same.

First, 3 g of tungsten powder was reacted and dissolved in 15 ml of H20t to obtain a transparent solution. Tungstic acid can be used instead of tungsten powder.
, H, Okamoto, K, Matsumoto
.

and Y, 5asaki, Inorg, Chf
, ^cta, 111 (+91161L27) uses a platinum catalyst, but in the present invention heating was used.

That is, place the reaction solution in a test tube container in a dryer heated from 60°C to 120°C, and heat it for about 2 hours to remove H
When the 0M reaction solution from which 2O2 had been removed started to turn yellow and foaming from the reaction solution had not yet finished, the first solution was taken out from the dryer and transferred to an evaporation dish, and dried by blowing air at room temperature. , a yellow solid was obtained. Note that if the reaction solution is removed from the dryer before it turns yellow or after foaming is complete, white crystals will form during drying and solidification.However, it is easier to identify the end point of the reaction as described above. , and there are few failures, however, if white crystals are generated, 1 (202
The reaction solution can be obtained by dissolving it in . On the other hand, when decomposing H20p using a platinum catalyst, foaming is so intense that it is difficult to distinguish the end point.

Example 2 W-TPA or W-1 produced in Example 1 was added to 1 m of alcohol such as methanol or distilled water.
A solution for a spin code was prepared by dissolving 0.45 g of solid PA. Rotation speed during spin code and obtained W-
The relationship between the film thickness of the IPA thin film is shown in FIG. 3. However, although this film thickness was measured after sufficiently drying the thin film and the one rotation time was 30 seconds, it may be greater or less than this.

After spin code, W-ZPA@51 from 80°C to 12
The relationship between the drying time at 0 DEG C. and the refractive index of the thin film measured by ellipsometry is shown in FIG. 4. The refractive index of the thin film when sufficiently dried was about 2.0. This fact was discovered for the first time by the present inventors. The refractive index of conventional photoresists is at most 16, and the refractive index of about 2.0 shown in this example is the largest refractive index of photoresists and as an electron beam resist capable of spin coding. . However, the refractive index did not change much depending on the light irradiation.

Example 3 KN O obtained by melting a commercially available slide glass at 400°C]
A thin film of W-IPA or W-HPA with a film thickness of 1500 nm is formed by a spin coding method on a glass optical guide path (6) with an effective thickness of about 2 μm of a waveguide layer prepared by a thermal ion exchange method by immersing it in water for 2 hours. did. 30 at 120”C
After drying the thin film for a few minutes, a period of 0.
0w-IP with a 5 μm diffraction grating made as shown in Figure 5.
Since A and W-HPA are negative photoresists, only the areas irradiated with laser light are cured, and the 5mm x
A 5 mm diffraction grating (7) was formed. Development was performed with distilled water. Further heat drying is performed at 120°C to reduce the refractive index to 2.
, set it to 0. Diffraction gratings with high refractive indexes can be made with thin films of other polytungstic acids containing Ta, Nb, etc.

In this embodiment, the glass optical waveguide (6) with the diffraction grating (7) thus obtained was assembled into a sensor as shown in FIG. )
A Teflon sheet C9) with a low refractive index of about 1.3 is sandwiched between the parts in contact with the optical waveguide to prevent leakage of the guided light. The solution chamber (8) is deposited on the surface of the solution chamber (8).
) may be fixed with epoxy resin, etc., in the solution chamber (8)
He-Ne laser light (3) in a state filled with distilled water
is incident on the diffraction grating (7) to excite the guided light (4), and then a solution with a different pH is introduced, the intensity of the guided light (4) changes significantly, and the relationship between pH and guided light intensity is almost linear. Met. Furthermore, when a protein solution (for example, albumin) is introduced into the solution chamber (8), the intensity of the guided light (4) changes greatly, and the protein concentration and the change in the guided light intensity are almost proportional as shown in Figure 7. did. When we compared the sensitivity of an optical waveguide grating biochemical sensor using the sol-gel method based on reported examples, this sensor was about 5 times better.

Example 4 Using a stamp method or a holographic diffraction grating method and a photocurable polymer, a diffraction grating (1
An optical waveguide 11i (11) with an ion was fabricated. The refractive index of the polymer optical waveguide [11] and the diffraction grating (10) is 1.52, and if they come into contact with an aqueous solution as they are, the difference in refractive index with the aqueous solution is small, so the diffraction efficiency will be extremely small. The w-rpΔ or W-HPA produced as in Example 1 was coated on the polymer optical waveguide (11) and the diffraction grating (10) by a spin coding method. Furthermore, the light from a He-Cd laser or a low-pressure mercury lamp was applied. was applied to only the diffraction grating portion, so that only the diffraction grating was covered with W-IPA or W-HPA as shown in Figure 9. Wetting between W-IPA or W-HPA and the polymer was To improve the quality, the polymer membrane is immersed in concentrated sulfuric acid.

Alternatively, it is effective to make the surface of the polymer film hydrophilic by exposing it to oxygen plasma.

The optical waveguide (11) with the diffraction grating (10) thus obtained was assembled into a sensor similar to that shown in FIG.
The sensor characteristics were almost the same as in Example 3.

Example 5 As shown in Fig. 10, first, a W-IPA or W-HPA diffraction grating (14) is formed on a slide glass substrate or an acrylic resin substrate (13) by three-beam interference method or electron beam beam method. Had made.

Next, as shown in FIG. 11, this was covered with a photocurable resin or glass to produce an optical waveguide section (15). A thin film was formed using a spin code method in the case of a photocurable resin, and a sputtering method in the case of glass. The optical waveguide with a diffraction grating thus produced was assembled into a sensor similar to that shown in FIG. 5, and the sensor characteristics were almost the same as in Example 3.

[Effect of the invention] The present invention produces effects as described below.

In the optical waveguide diffraction grating biochemical sensor of the present invention, the refractive index of the material of the optical waveguide part is low (and the refractive index of the material of the diffraction grating part is high), so that the guided light is attenuated in the optical waveguide part. In addition, the influence of adsorption of substances in the solution to the optical waveguide section is reduced, and the diffraction efficiency at the diffraction grating section is increased, increasing the sensitivity of the sensor. By using a resist material discovered by the inventors that has a high refractive index of 1°85 or higher, the machining accuracy of the single diffraction grating structure has been improved and processing has become easier. Thanks to this improvement, the resist material can now be easily obtained.

4,

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional optical waveguide grating biochemical sensor, and Figure 2 shows the relationship between the optimal angle and the refractive index of the cladding when laser light is input from the diffraction grating to excite the guided light. be. Figure 3 shows the relationship between the rotation speed and film thickness when W-IPA is produced by the spin code method, and Figure 4 shows the relationship between the rotation speed and film thickness when W-IPA is produced by the spin code method.
This is the relationship between the refractive index of the thin film and the drying time. Figure 5 shows W-
A perspective view of a glass optical waveguide equipped with a diffraction grating structure made of IPA, Fig. 6 is a vertical cross-sectional view of the optical waveguide shown in Fig. 5 assembled into a biochemical sensor, and Fig. 7 shows the use of the sensor shown in Fig. 6. This is an example of sensing albumin in a solution. Figure 8 is a vertical cross-sectional view of an optical waveguide with a diffraction grating made using a photocurable resin, and Figure 9 is a vertical cross-sectional view of the diffraction grating shown in Figure 8 covered with W-TPA or W-HPA. be. Fig. 10 is a vertical cross-sectional view of a diffraction grating made of W-IPA or W-HPA attached to a glass substrate, and Fig. 11 is a state in which the substrate and diffraction grating shown in Fig. 10 are covered with a leading wave layer. FIG. 1... Diffraction grating relief, 2.11.15... Thin film optical waveguide or waveguide layer, 3... Laser light, 4...
- Waveguide light, 5... Clad part, 6... Glass optical waveguide, 7, 10.14... Diffraction grating, 8... Solution chamber,
9... Teflon sheet, 12... High refractive index photoresist film, 13... Slide glass

Claims (1)

[Claims] 1. A diffraction grating (7) made of a material with a refractive index of 1.85 or more attached on top of an optical waveguide layer (6) made of a material with a refractive index of 1.45 to 1.55. An optical waveguide diffraction grating biochemical sensor characterized in that is a sensitive part. 2. The optical waveguide according to claim 1, wherein the diffraction grating structure (7) is made of a photoresist material having a refractive index of 1.85 or more or an electron beam resist material having a refractive index of 1.85 or more. Diffraction grating biochemical sensor. 3. A photoresist thin film having a refractive index of 1.85 or more, which is characterized by forming a thin film made of isopolytungstic acid, heteropolytungstic acid, or a material containing these polytungstic acids as one of its constituent elements, and then drying and solidifying it. How to make it. 4. A method for synthesizing isopolytungstic acid or heteropolytungstic acid, which comprises removing excess H_2O_2 from the reaction solution by heating.