JPH09257696A - Surface plasmon resonance sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a method of inserting a light source and a sensor chip unit into a small hole or narrow plate by separating them from a photodetector. SOLUTION: A sensor chip 2 has a gold or silver thin film having a thickness of about 50nm to cause a surface plasmon resonance on the surface of a glass plate having the same refractive index a that of a prism 13 and connected to the upper bottom of a prism 13 via matching oil having the same refractive index as that of the prims 13. Or, the metal thin film may be deposited directly on the upper bottom of the prism 13. An incident side GI type optical fiber 5 and a reflecting side GI type optical fiber 6 are mounted at the lower bottom of the prism 13. Since the fibers 5, 6 are mounted in parallel in the same direction as that of the lower bottom of the prism 13, the chip unit has substantially the same size as that of the prism 13, and can be inserted freely if it is the hole of the size for passing the prism 13. The fiber 5 introduces the incident light from a light source, and fiber 6 introduces the reflected light from the prism 13 to a photoreceiving sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface plasmon resonance sensor device utilizing the surface plasmon resonance phenomenon, and more particularly to improvement of the configuration of its optical system.

[0002]

2. Description of the Related Art A surface plasmon resonance sensor is known which measures the refractive index of a solution or the like and its variation by utilizing the surface plasmon resonance phenomenon. Here, since the fluctuation of the refractive index of the solution reflects the fluctuation of the amount of the substance in the solution, for example, as a biosensor used in the fields of biochemistry, molecular biology, medical examination, etc., this surface plasmon resonance The sensor is being used.

The surface plasmon resonance sensor is basically composed of
A light source, a high refractive index light transmission medium having a light reflection surface having a metal thin film, and a photodetector are provided. The light transmission medium is generally made of a high refractive index material such as glass or acrylic and is called a sensor chip. With a sample such as blood or urine in contact with the outer surface of the metal thin film formed on the light-reflecting surface of the sensor chip, a light ray is incident on the light-reflecting surface from the light source to the light-reflecting surface through the sensor chip, The reflected light is received by the photodetector.

A conventional surface plasmon resonance sensor device is
A spherical (or aspherical) lens is provided between the light source and the sensor chip. The bundle of rays from the light source is condensed into a "wedge" shape on the light reflecting surface of the sensor chip through this spherical lens. Therefore, light rays having different incident angles are simultaneously incident on the light reflecting surface, and the light rays are reflected with a reflectance distribution associated with surface plasmon resonance. The refractive index of the sample can be determined by measuring the incident angle (plasmon resonance angle) corresponding to the minimum value in the reflectance distribution.

In the conventional apparatus, the above-mentioned light source, spherical lens, optical parts such as sensor chip and photodetector, and piping for supplying a sample to the sensor chip are housed in one case.

[0006]

In the conventional device, various optical parts and pipes are housed in one case, so that the size of the case is more than the size obtained by adding the required optical path length to these optical parts. Further, it is difficult to reduce the size of the spherical lens among the optical components. Further, the case is made of a material and a shape that are hard to be deformed because it is necessary to maintain optical characteristics.

Therefore, it is difficult to downsize the conventional device so that it can be used for measurement in a small hole such as an endoscope.

Therefore, it is an object of the present invention to provide a surface plasmon resonance sensor device having an improved structure suitable for measurement in a small hole such as an endoscope and measurement in a narrow space.

[0009]

A surface plasmon resonance sensor device of the present invention comprises a light source, a sensor chip unit including a sensor chip having a light reflecting surface in contact with a metal thin film,
A photodetector is provided, and the reflected light from the sensor chip is guided to the photodetector through the graded index type optical fiber.

A graded index type optical fiber (hereinafter referred to as GI type optical fiber) has a refractive index distributed in a parabolic shape from the center to the periphery, and light travels in a parabolic shape in a fixed cycle, so that it is used as a lens. Has the same effect.

According to this structure, the light source and the sensor chip unit can be separated from the photodetector. That is, it is possible to extend the optical fiber from the case in which the photodetector is housed and connect the sensor chip unit and the light source to the tip of the optical fiber. By forming the sensor chip unit and the light source in a small size, this part can be inserted into a small hole or a narrow place and used as an endoscope.

Preferably, the light source and the sensor chip unit are also connected by a GI type optical fiber. Thereby, the sensor chip unit can be separated from the light source and the photodetector.
Since the sensor chip unit is generally composed of a sensor chip and an attached prism, etc., it is easy to make it very small. Therefore, only this sensor chip unit can be inserted into a small hole or a narrow space and used as an endoscope.

[0013]

FIG. 1 shows the entire basic configuration of a surface plasmon resonance sensor device according to an embodiment of the present invention.

This surface plasmon resonance sensor device has an L
ED (light emitting diode) or LD (laser diode)
Such as a light source 1, a sensor chip 2 having a metal thin film on a light reflecting surface, a prism 3 bonded to the sensor chip 2, a light receiving sensor 4 which is a one-dimensional CDD, and incident light from the light source 1 to the prism 3. Is provided with an incident side graded index type (GI type) optical fiber 5 and a reflection side GI type optical fiber 6 for guiding reflected light from the prism 3 to the light receiving sensor 4. Further, although not shown, a polarizing plate for converting incident light from the light source 1 into P-polarized light for exciting the surface plasmon wave is provided on an optical path at an appropriate position between the light source 1 and the sensor chip 2. Will be placed.

The sensor chip 2 is formed by forming a thin film 2a of gold or silver for causing surface plasmon resonance with a thickness of about 50 nm on the surface of a glass plate having the same refractive index as the prism 3. The sensor chip 2 is bonded to the prism 3 via a matching oil having the same refractive index as the prism 3. The sensor chip 2 can be easily replaced by removing it from the prism 3. It should be noted that the prism 3 having the metal thin film 2a directly formed on the surface thereof may be used as a sensor chip. When this sensor device is used as a biosensor for detecting a specific antigen, a specific antibody that selectively reacts with the antigen may be fixed on the outer surface of the metal thin film 2a.

As shown in FIG. 2, the GI type optical fiber 5 on the incident side receives light from the light source 1, propagates it in a meandering manner, and focuses it on the light reflecting surface having the metal thin film of the sensor chip 2. Tied to. In Figure 2, the light has one node in the fiber 5.
As an example, the length of the fiber 5 is made longer by adding an integer multiple of the meandering period of light (interval between nodes) to the length shown in the figure.

As shown in FIG. 3, the GI optical fiber 6 on the reflection side receives the reflected light from the sensor chip 2, propagates it in a meandering manner, and spreads it in a wide angle according to the reflection angle to receive light. 4. FIG. 3 exemplifies a case where the fiber 6 makes one node. However, when the length of the fiber 6 is made longer, the length is the figure length plus an integer multiple of the meandering period of light. In the optical fiber 6, information on the intensity distribution (reflectance distribution) according to the reflection angle (incident angle) of the reflected light is maintained. The resonance angle of the surface plasmon resonance is calculated from the intensity distribution of the reflected light that appears in the output signal of the light receiving sensor 4.

The light source 1 and the light receiving sensor 4 can be housed in one case. In that case, the cables of the flexible and sufficiently long optical fibers 5 and 6 extend out from the case, and the sensor chip 2 and the prism 3 are attached to the tip of the cables.
A sensor chip unit consisting of is connected. This sensor chip unit is easy to make very small. Therefore, this sensor chip unit can be used endoscopically by inserting a small hole or a narrow place.

The light source 1 is made sufficiently small (for example, about several mm) by using an LED chip, and the light source 1 is not a spherical lens but a minute (for example, 1 mm diameter) graded index lens. It is also possible to join to the prism 3 via. In this case, the incident side optical fiber 6 is unnecessary and the light source 1 has a small size, so that the light source 1 can be included in the sensor chip unit. In that case, the light receiving sensor 4 and a power supply circuit and a signal processing circuit (not shown) are housed in a case, and the power supply line for the light source 1 and the cable of the reflection side optical fiber 6 are extended from the case to the outside. A sensor chip unit including the light source 1 can be coupled to the tip.

4 and 5 are a front view and a perspective view showing another embodiment of the sensor chip unit.

The sensor chip is formed by bonding the same sensor chip 2 as shown in FIG. 1 to the upper bottom surface of the trapezoidal prism 13. Alternatively, the metal thin film may be directly vapor-deposited on the upper bottom surface of the trapezoidal prism 13. An incident side GI type optical fiber 5 and a reflecting side GI type optical fiber 6 are attached to the lower bottom surface of the trapezoidal prism 13. Optical fibers 5 and 6 are prisms 1.
Since the sensor chip unit is mounted on the lower bottom surface of the prism 3 in the same direction and in parallel with each other, the sensor chip unit has substantially the same size as the prism 13, and therefore a hole of a size through which the prism 3 passes can be freely inserted. it can.

The shape of the prism 13 is designed so that the incident angles θ of the light on the sensor chip 2 are distributed around, for example, 45 degrees. This is an angle (plasmon resonance angle) at which surface plasmon resonance occurs when the sensor chip 2 is in contact with air when the prism 13 having a refractive index of about 1.52 is used. Therefore, this configuration is suitable as a gas sensor.

FIG. 6 shows an example in which the sensor chip unit shown in FIG. 4 is modified to be used for the purpose of measuring an aqueous solution. In the prism 3 having a refractive index of 1.52, the plasmon resonance angle when the sensor chip is in contact with water is about 72 degrees. The sensor chip 2 is bonded to the side surface of the same trapezoidal prism 13 as shown in FIG. 4 so that the incident angles to the sensor chip 2 are distributed around this 72 degrees. Since the sensor chip 2 is bonded to the prism 13 via the matching oil, it is easy to change the bonding location according to the purpose of measurement.

Further, in the modification of FIG. 6, the light guide plate 11 is inserted between the reflection side optical fiber 6 and the light receiving sensor 4. Although the light emitted from the optical fiber 6 spreads in a conical shape in the natural state, the light guide plate 11 confines this light in a substantially two-dimensional space and guides it to the light receiving sensor 4. Therefore, the amount of light incident on the light receiving sensor 4 increases, and a light receiving sensor with low sensitivity can also be used.

FIG. 7 shows the appearance of a cap type sensor chip used in yet another embodiment of the sensor chip unit, and FIG. 8 shows a cross section taken along the line AA 'of FIG.

The cap 21 is a metal or resin case formed in a substantially trapezoidal shape so as to cover the trapezoidal prism 13 shown in FIG. 21a and 21b.
The sensor chip 2 similar to that shown in FIG. 1 is bonded to the opening 21a on the upper bottom surface of the trapezoidal cap 21 from the inside. Further, the trapezoidal prism 13 is provided in the trapezoidal cap 21.
And the sensor chip 2 is inserted in the same manner as shown in FIG.
And the trapezoidal prism 13 are joined.

This cap-type sensor chip is fitted in an optical fiber fixing block 22 as shown in FIG. The fixing block 22 is a rectangular parallelepiped block having a front surface 22a of a size that fits exactly into the opening 21b on the lower bottom surface of the cap 21, and from the front surface 22a to the rear surface 2
It has two holes 22a and 22b penetrating to 2b, and the incident side GI optical fiber 5 and the reflection side GI optical fiber 6 are fixedly inserted into these through holes 22a and 22b. A sensor chip unit as shown in FIG. 10 is completed by fitting the front portion of the fixing block 22 into the opening 21b on the lower bottom surface of the cap type sensor chip and adhering the two. The positional relationship of the optical components is the same as that of the embodiment shown in FIG.

In this sensor chip unit, it is possible to prevent the prism 13 from coming into contact with dust, water and other contaminants. In addition, by disposing only the cap 21 and the sensor chip 2 adhered to the cap 21 at each measurement, the process after measuring dangerous substances such as bacteria and viruses becomes easy.

[0029]

The surface plasmon resonance sensor device of the present invention can be used by inserting it into a small hole or a narrow place like an endoscope.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an overall basic configuration of a surface plasmon resonance sensor device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an incident side GI type optical fiber.

FIG. 3 is an explanatory diagram of a reflection side GI type optical fiber.

FIG. 4 is a front view showing another embodiment of the sensor chip unit.

FIG. 5 is a perspective view of the same.

FIG. 6 is a front view showing a modified example of the sensor chip unit of FIG.

FIG. 7 is a perspective view showing a cap type sensor chip used in still another embodiment of the sensor chip unit.

8 is a cross-sectional view taken along the line AA ′ of FIG.

FIG. 9 is a perspective view of a block for fixing an optical fiber.

FIG. 10 is a perspective view showing a sensor chip unit using a cap type sensor chip.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 sensor chip 3, 13 prism 4 light receiving sensor 5 incident side GI type optical fiber 6 reflection side GI type optical fiber 11 light guide plate 21 cap 22 optical fiber fixing block

Claims (6)

[Claims] 1. A surface plasmon resonance sensor device comprising a light source, a sensor chip unit including a sensor chip having a light reflecting surface in contact with a metal thin film, and a photodetector, wherein reflected light from the sensor chip is A surface plasmon resonance sensor device comprising a reflection side graded index type optical fiber for guiding to a photodetector. 2. The apparatus according to claim 1, further comprising an incident side graded index optical fiber for guiding light from the light source to the sensor chip and focusing on the light reflecting surface. Surface plasmon resonance sensor device. 3. The surface plasmon according to claim 2, wherein the sensor chip unit has a trapezoidal prism, and the incident-side and reflection-side optical fibers are attached to the same surface of the trapezoidal prism. Resonance sensor device. 4. The apparatus according to claim 2, wherein the sensor chip unit has a trapezoidal prism, the sensor chip can be selectively joined to different surfaces of the trapezoidal prism, and the trapezoidal prism further comprises: A surface plasmon resonance sensor device having a shape in which a distribution range of an incident angle of light on the sensor chip changes depending on a surface to which the sensor chip is joined. 5. The device according to claim 1, wherein the light from the reflection-side optical fiber is confined in a substantially two-dimensional space between the reflection-side optical fiber and the photodetector, and the light is detected in the photodetector. A surface plasmon resonance sensor device comprising a light guide plate for guiding. 6. The surface plasmon resonance sensor device according to claim 1, wherein the sensor chip unit includes a prism bonded to the sensor chip, and a cap that covers the prism.