Pressure sensor head and pressure sensor device

Abstract

To provide a pressure sensor head having a reflection film adjacent to a pressure-sensitive film and capable of suppressing a reduction in detection sensitivity.SOLUTION: A pressure sensor head 1 includes: an optical fiber 10 having a first end 10a to which excitation light 111 is incident and a second end 10b that emits the excitation light 111; an optically transmissive pressure-sensitive film 13 formed of a flexible material 15 containing metal nanoparticles 16 exhibiting localized plasmon resonance, having an incidence surface 13a to which the excitation light 111 is incident from the second end 10b and a pressurizing surface 13b to which a pressure is applied, and deformed according to the applied pressure to shift a peak wavelength of an absorption spectrum of the localized plasmon resonance by the metal nanoparticles 16; and a reflection film 14 having a plurality of slits formed therein and arranged opposed to the pressurizing surface 13b. When the excitation light 111 is incident from the first end 10a, detection light 112 having wavelength characteristics according to the localized plasmon resonance by the metal nanoparticles 16 is emitted from the first end 10a.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a pressure sensor head and a pressure sensor device. [Background technology]

[0002] A pressure-sensitive membrane is known that is formed from a flexible material containing metal nanoparticles that undergo localized plasmon resonance, and that, when pressure is applied, shifts the peak wavelength of the absorption spectrum of the localized plasmon resonance caused by the metal nanoparticles (see, for example, Non-Patent Document 1). The pressure-sensitive membrane described in Non-Patent Document 1 is formed from dimethylpolysiloxane (also known as PDMS) that contains gold nanoparticles with a thickness of 10 nm. When the pressure-sensitive membrane described in Non-Patent Document 1 is irradiated with white excitation light, localized plasmon resonance occurs due to the metal nanoparticles, and the detection light that passes through the pressure-sensitive membrane has wavelength characteristics corresponding to the localized plasmon resonance caused by the metal nanoparticles.

[0003] When a pressure of 0 kPa to 35 kPa is applied to the pressure-sensitive film described in Non-Patent Document 1, the film is distorted, and the peak wavelength of the absorption spectrum of localized plasmon resonance due to the metal nanoparticles changes from 600 nm to 610 nm. With the pressure-sensitive film described in Non-Patent Document 1, the peak wavelength of the absorption spectrum of localized plasmon resonance due to the metal nanoparticles shifts in response to changes in the applied pressure, so the pressure applied to the pressure-sensitive film can be detected from the peak wavelength of the absorption spectrum. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] “Development of an optical pressure-sensitive membrane based on plasmon resonance on a gold island film” Eito Takebayashi et al., Electronics and Communications in Japan December, 2020 Summary of the Invention [Problem to be solved by the invention]

[0005] The pressure-sensitive membrane described in Non-Patent Document 1 is being considered for use in a pressure sensor head for measuring blood pressure inside the body, such as the intracoronary artery pressure used to calculate the myocardial fractional flow reserve (FFR). The pressure-sensitive membrane described in Non-Patent Document 1 detects the pressure applied to the pressure-sensitive membrane from the peak wavelength of the absorption spectrum, and therefore can suppress a decrease in detection accuracy caused by attenuation of the light intensity of the excitation light and detection light due to loss in the optical fiber, etc.

[0006] When the pressure-sensitive film described in Non-Patent Document 1 is used in a pressure sensor head, a reflective film made of a metal such as aluminum is disposed adjacent to the pressure-sensitive film. By having the pressure-sensitive film and the reflective film disposed adjacent to it, the pressure sensor head can emit detection light having wavelength characteristics according to localized plasmon resonance of the metal nanoparticles to an externally disposed spectrometer via an optical fiber or the like.

[0007] However, when a reflective film is placed adjacent to a pressure-sensitive film, the flexibility of the pressure-sensitive film decreases, and the amount of distortion of the pressure-sensitive film in response to pressure applied to the pressure-sensitive film decreases, which reduces the shift in the peak wavelength of the absorption spectrum and may result in a decrease in detection sensitivity.

[0008] The present invention is intended to solve such problems, and has an object to provide a pressure sensor head that has a reflective film adjacent to a pressure-sensitive film and that can suppress a decrease in detection sensitivity. [Means for solving the problem]

[0009] The sensor device according to the present invention comprises a housing, an optical fiber having a first end into which excitation light is incident and a second end from which the excitation light is emitted, the second end being fixed to the housing, an optically transparent pressure-sensitive membrane formed of a flexible material containing metal nanoparticles that exhibit localized plasmon resonance, the optically transparent pressure-sensitive membrane having an incident surface into which the excitation light is incident from the second end and a pressure surface to which pressure is applied, the optically transparent pressure-sensitive membrane distorting in response to pressure applied to the pressure surface, thereby shifting the peak wavelength of the absorption spectrum of the localized plasmon resonance caused by the metal nanoparticles, and a reflective membrane having a plurality of slits formed therein and disposed opposite the pressure surface, and when excitation light is incident from the first end, the sensor device emits detection light from the first end, the detection light having wavelength characteristics according to the localized plasmon resonance caused by the metal nanoparticles.

[0010] Furthermore, in the sensor head according to the present invention, the plurality of slits are preferably formed around a reflecting portion that reflects the excitation light that has passed through the pressure-sensitive film.

[0011] Furthermore, in the sensor head according to the present invention, the plurality of slits are preferably arranged to form a plurality of circular rings with different diameters.

[0012] Furthermore, in the pressure sensor head according to the present invention, each of the plurality of circular rings is preferably formed by a single slit.

[0013] Furthermore, in the pressure sensor head according to the present invention, each of the plurality of circular rings is preferably formed by a plurality of slits.

[0014] Furthermore, in the pressure sensor device according to the present invention, the plurality of slits are preferably formed randomly.

[0015] Furthermore, a sensor device according to the present invention includes a light-emitting element that emits excitation light, a pressure sensor head that contains metal nanoparticles that exhibit localized plasmon resonance and that emits detection light having wavelength characteristics according to the localized plasmon resonance of the metal nanoparticles when the excitation light is incident thereon, a spectrometer that separates the detection light into wavelengths and detects the intensity of the dispersed light, and a computing device that extracts a peak wavelength of the absorption spectrum of the localized plasmon resonance of the metal nanoparticles from the intensity of the light detected by the spectrometer, determines a pressure applied to the pressure sensor head from the extracted peak wavelength, and outputs a pressure signal indicating the determined pressure, wherein the pressure sensor head includes a housing and The optical fiber has a first end to which excitation light is incident and a second end from which the excitation light is emitted, the second end being fixed to a housing; an optically transparent pressure-sensitive membrane formed of a flexible material containing metal nanoparticles, the optically transparent pressure-sensitive membrane having an incident surface to which the excitation light is incident from the second end and a pressure surface to which pressure is applied, the optically transparent pressure-sensitive membrane distorting in response to the pressure applied to the pressure surface, thereby shifting the peak wavelength of the absorption spectrum of the localized plasmon resonance caused by the metal nanoparticles; and a reflective membrane having a plurality of slits formed therein and arranged opposite the pressure surface, wherein when excitation light is incident from the first end, detection light having wavelength characteristics according to the localized plasmon resonance caused by the metal nanoparticles is emitted from the first end. [Effects of the Invention]

[0016] The pressure sensor head according to the present invention has a reflective film adjacent to the pressure-sensitive film and can suppress a decrease in detection sensitivity. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a block diagram of a pressure sensor device according to an embodiment. [Figure 2] 1A and 1B are diagrams illustrating a pressure sensor head according to a first embodiment. [Figure 3] FIG. 3 is a plan view of the reflective film shown in FIG. [Figure 4]3(a) is a diagram showing the pressure application conditions when the distortion and displacement of the pressure-sensitive film and the reflective film shown in FIG. 2 are measured by simulation when pressure is applied to the pressure-sensitive film and the reflective film, and FIG. 3(b) is a contour diagram showing the displacement of the pressure-sensitive film and the reflective film when pressure is applied to the pressure-sensitive film and the reflective film. [Figure 5] FIG. 10 is a diagram showing a pressure sensor head according to a second embodiment. [Figure 6] 6(a) is a diagram showing the pressure application conditions when the distortion and displacement of the pressure-sensitive film, the reflective film, and the moisture-proof film shown in FIG. 5 are measured by simulation when pressure is applied to the pressure-sensitive film, the reflective film, and the moisture-proof film; and FIG. 6(b) is a contour diagram showing the displacement of the pressure-sensitive film, the reflective film, and the moisture-proof film when pressure is applied to the pressure-sensitive film, the reflective film, and the moisture-proof film. [Figure 7] 10(a) is a plan view of a reflective film according to a first modified example, FIG. 10(b) is a plan view of a reflective film according to a second modified example, and FIG. 10(c) is a plan view of a reflective film according to a third modified example. DETAILED DESCRIPTION OF THE INVENTION

[0018] The pressure sensor head and pressure sensor device according to the present invention will be described below with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to the embodiments, but extends to the inventions set forth in the claims and their equivalents.

[0019] (Configuration and Function of Pressure Sensor Device According to the Embodiment) FIG. 1 is a block diagram of a pressure sensor device according to an embodiment.

[0020] The pressure sensor device 100 has a light source element 101, an optical branching element 102, a spectroscope 103, a computing device 104, and a pressure sensor head 1, and is used to measure blood pressure inside the body of a subject, such as the pressure inside the coronary artery. Optical paths between the light source element 101, the optical branching element 102, the spectroscope 103, and the pressure sensor head 1 are formed by optical fibers 105. The optical fibers 105 optically connect between the light source element 101 and the optical branching element 102, between the optical branching element 102 and the pressure sensor head 1, and between the optical branching element 102 and the spectroscope 103.

[0021] The light source element 101 is a light emitting element such as a halogen lamp, a laser diode, or a light emitting diode (LED) that emits white light as excitation light 111 in response to application of a voltage. The light branching element 102 transmits the excitation light 111 emitted from the light source element 101 to the pressure sensor head 1, and branches the detection light 112 emitted from the pressure sensor head 1 to the spectroscope 103.

[0022] The pressure sensor head 1 contains metal nanoparticles that exhibit localized plasmon resonance, and exhibits localized plasmon resonance due to the metal nanoparticles when excitation light 111 is incident on the pressure sensor head 1. The pressure sensor head 1 emits detection light 112 having wavelength characteristics according to the localized plasmon resonance due to the metal nanoparticles that is exhibited in response to the incidence of excitation light 111.

[0023] In response to the input of the detection light 112, the spectrometer 103 separates the detection light 112 into wavelengths, generates an intensity signal 120 indicating the intensity of the dispersed light, and outputs the generated intensity signal 120 to the arithmetic unit 104. The spectrometer 103 is preferably a spectrometer capable of measuring spectra in visible light from 400 nm to 800 nm and near-infrared light from 800 nm to 2500 nm. Furthermore, the smaller the wavelength resolution of the spectrometer 103, the more preferable it is so that changes in peak wavelength due to pressure can be observed. For example, the wavelength resolution of the spectrometer 103 is 10 nm or less, 5 nm or less, 2 nm or less, or 1 nm or less, but is not limited to these.

[0024] The arithmetic device 104 is a computer that determines the pressure applied to the pressure sensor head 1 and outputs a pressure signal indicating the determined pressure. First, in response to the intensity signal 120 input from the spectrometer 103, the arithmetic device 104 extracts the peak wavelength of the absorption spectrum of localized plasmon resonance caused by the metal nanoparticles 16 from the light intensity corresponding to the intensity signal 120. Next, the arithmetic device 104 determines the pressure to be applied to the pressure sensor head 1 from the extracted peak wavelength of the absorption spectrum, for example, by referring to a table indicating the correlation between the peak wavelength of the absorption spectrum and the pressure applied to the pressure-sensitive film 13. Then, the arithmetic device 104 outputs a pressure signal indicating the determined pressure.

[0025] (Configuration and Function of Pressure Sensor Head According to First Embodiment) FIG. 2 is a diagram showing the pressure sensor head 1. As shown in FIG.

[0026] The pressure sensor head 1 has an optical fiber 10, an adhesive member 11, a housing 12, a pressure-sensitive film 13, and a reflective film 14. The pressure sensor head 1 is inserted into the body of a subject, and detects blood pressure inside the body of the subject in response to excitation light incident thereon via an optical fiber 105, and outputs detection light indicating the detected blood pressure.

[0027] The optical fiber 10 has a first end 10a optically connected to an optical fiber 105 connected to the optical branching element 102, and a second end 10b fixed to the housing 12. The optical fiber 10 guides excitation light 111 incident from the optical branching element 102 through the optical fiber 105 at the first end 10a and outputs it from the second end 10b to the pressure-sensitive film 13. The optical fiber 10 also guides detection light 112 incident from the pressure-sensitive film 13 through the housing 12 at the second end 10b and outputs it from the first end 10a to the optical fiber 105.

[0028] The adhesive member 11 is an elastomer formed from a fluorine compound, and is an adhesive member that adheres the optical fiber 10 to the recess of the housing 12. The adhesive member 11 is, for example, SIFEL (registered trademark) manufactured by Shin-Etsu Chemical Co., Ltd.

[0029] The housing 12 is made of silicon (Si), silicon nitride (SiN), or the like, and has a hexagonal prism shape. The surface of the housing 12 may be modified by silane treatment. A recess is formed on one end face of the housing 12, into which the second end 10b of the optical fiber 10 is inserted, and a pressure-sensitive film 13 is disposed on the other end face of the housing 12.

[0030] The pressure-sensitive film 13 is an optically transparent member formed of a flexible material 15 containing a plurality of metal nanoparticles 16 that undergo localized plasmon resonance. The pressure-sensitive film 13 has an incident surface 13a onto which excitation light 111 is incident from the second end 10b of the optical fiber 10, and a pressure surface 13b located opposite the incident surface 13a and onto which pressure is applied. The pressure-sensitive film 13 distorts in response to the pressure applied to the pressure surface 13b, thereby shifting the peak wavelength of the absorption spectrum of the localized plasmon resonance caused by the metal nanoparticles 16.

[0031] The flexible material 15 is formed of a flexible synthetic resin such as PDMS and has a hexagonal planar shape. The flexible material 15 is, for example, SILPOT 184 manufactured by The Dow Chemical Company. The thickness of the flexible material 15 is, for example, 10 nm. The material and thickness of the flexible material 15 are determined so that the radial distortion of the pressure-sensitive film 13 is 10% to 50% at normal pressure in response to pressure applied to the pressure-applying surface 13b. The Young's modulus of the material of the flexible material 15 is 0.01 MPa to 1 MPa, and the thickness of the flexible material 15 is 1 μm to 10 mm, so that the radial distortion of the pressure-sensitive film 13 is 10% to 50% at normal pressure.

[0032] The metal nanoparticles 16 are formed of metals such as gold (Au), platinum (Pt), silver (Ag), and nickel (Ni), and have a spherical shape. The diameter of the metal nanoparticles 16 is 40 nm or more and 250 nm or less. Because the diameter of the metal nanoparticles 16 is 40 nm or more and 250 nm or less, localized surface plasmon resonance occurs when excitation light with a wavelength 10 times the diameter, i.e., visible light of 400 nm to 800 nm and near-infrared light of 800 nm to 2500 nm, is incident on the metal nanoparticles 16. The metal nanoparticles 16 may have shapes other than spherical, such as rod-like, rectangular, or flat.

[0033] The reflective film 14 is formed of a metal such as aluminum (Al), silver (Ag), or gold (Au) or a dielectric multilayer film, and is arranged so as to cover the surface of the pressure-sensitive film 13 opposite to the surface facing the housing 12. The Young's modulus of the reflective film 14 is several GPa to several hundred GPa, and the film thickness is 1 μm or less. The reflective film 14 is arranged so as to face the pressure-applying surface 13b of the pressure-sensitive film 13. The reflective film 14 is also arranged so that its outer edge covers the side surface of the pressure-sensitive film 13, and is fixed to the housing 12. The reflective film 14 is formed, for example, by evaporating the raw material of the reflective film 14 onto the pressure-sensitive film 13.

[0034] FIG. 3 is a plan view of the reflective film 14. As shown in FIG.

[0035] The reflective film 14 has a circular reflective portion 20 in the center, and first to third slits 21 to 23 are formed to surround the reflective portion 20. The reflective film 14 reflects light that has passed through the pressure-sensitive film 13 and emits the reflected light toward the pressure-sensitive film 13. Each of the first to third slits 21 to 23 is a single slit having a circular planar shape and is formed with a width that makes it difficult for liquid to penetrate. The first slit 21 is disposed between the reflective portion 20 and the second slit 22, and has a diameter that is longer than the diameter of the reflective portion 20 but shorter than the diameter of the second slit 22. The second slit 22 is disposed between the first slit 21 and the third slit 23, and has a diameter that is longer than the diameter of the first slit 21 but shorter than the diameter of the third slit 23. The third slit 23 is disposed outside the second slit 22 and has a diameter that is longer than the diameter of the second slit 22.

[0036] (Actions and Effects of the Pressure Sensor Head According to the First Embodiment) In the pressure sensor head 1, by forming the first slit 21 to the third slit 23 in the reflective film 14, the flexibility of the reflective film 14 is improved, making it difficult for the reflective film 14 to suppress distortion of the pressure-sensitive film 13, and thereby suppressing a decrease in the pressure detection sensitivity of the pressure-sensitive film 13.

[0037] Fig. 4(a) is a diagram showing pressure application conditions when measuring by simulation the distortion and displacement of the pressure-sensitive film 13 and the reflective film 14 when pressure is applied to the pressure-sensitive film 13 and the reflective film 14. Fig. 4(b) is a contour diagram showing the displacement of the pressure-sensitive film 13 and the reflective film 14 when pressure is applied to the pressure-sensitive film 13 and the reflective film 14.

[0038] The simulations shown in Figures 4(a) and 4(b) were performed using SolidWorks with a geometrically nonlinear large displacement analysis using shell elements. The thickness of the pressure-sensitive film 13 is 1.3 μm, and the Young's modulus of the pressure-sensitive film 13 is 0.44 Pa. The thickness of the reflective film 14 is 10 nm, and the Young's modulus of the reflective film 14 is 68.3 GPa. Because SolidWorks cannot simulate a film thickness of 10 nm, the simulation was performed with the scale scaled 1000 times larger. In the simulation, pressure was applied to the area indicated by arrow A on the surface of the reflective film 14 opposite to the surface facing the pressure-sensitive film 13.

[0039] When the first slits 21 to the third slits 23 are not formed in the reflective film 14, the distortion of the pressure-sensitive film 13 is reduced to about 1 / 60 compared to when the reflective film 14 is not arranged. Because the distortion of the pressure-sensitive film 13 is reduced to about 1 / 60, the detection sensitivity of the reflective film 14 is reduced to about 1 / 60 compared to when the reflective film 14 is not arranged.

[0040] On the other hand, by forming the first slits 21 to the third slits 23 in the reflective film 14, the distortion of the pressure-sensitive film 13 was reduced to about half compared to when the reflective film 14 was not provided. By forming the first slits 21 to the third slits 23 in the reflective film 14, the distortion of the pressure-sensitive film 13 increased by about 30 times compared to when the first slits 21 to the third slits 23 were not formed. The detection sensitivity of the reflective film 14 increased by about 30 times compared to when the first slits 21 to the third slits 23 were not formed, due to the distortion of the pressure-sensitive film 13 increasing by about 30 times.

[0041] Furthermore, in the pressure sensor head 1, the first slits 21 to the third slits 23 are formed so as to surround the reflecting portion 20, and therefore the light transmitted through the pressure-sensitive film 13 does not enter the first slits 21 to the third slits 23. In the pressure sensor head 1, the light transmitted through the pressure-sensitive film 13 does not enter the first slits 21 to the third slits 23, and therefore there is no risk of the reflectance of the light transmitted through the pressure-sensitive film 13 decreasing due to the light being transmitted through the pressure-sensitive film 13 entering the first slits 21 to the third slits 23. In the pressure sensor head 1, there is no risk of the reflectance of the light transmitted through the pressure-sensitive film 13 decreasing, and therefore the light intensity of the detection light 112 does not decrease due to the first slits 21 to the third slits 23 being formed in the reflecting film 14.

[0042] Furthermore, by forming the first slits 21 to the third slits 23 to have widths that make it difficult for liquid to penetrate, the pressure sensor head 1 is less likely to have liquid penetrate from the outside to the inside of the pressure sensor head 1 and swell the flexible material 15 in an environment where liquid is present around it, such as in a blood vessel.The pressure sensor head 1 is less likely to have the flexible material 15 swell and change the distance between the metal nanoparticles 16 contained in the pressure-sensitive film 13, so it is possible to detect the pressure of the liquid present around the pressure sensor head 1.

[0043] Furthermore, in the pressure sensor head 1, the reflective film 14 functions as a dustproof film that prevents dust from entering the interior of the pressure sensor head 1 from the outside, so there is little risk of dust entering the interior of the pressure sensor head 1 both during the manufacturing process and during use. Since there is little risk of dust entering the interior of the pressure sensor head 1 during the manufacturing process, there is less risk of dust particles on the order of several microns in diameter getting mixed into the pressure-sensitive film 13 during the manufacturing process, which would reduce the risk of a decrease in yield. Furthermore, since there is little risk of dust entering the interior of the pressure sensor head 1 during use, there is less risk of dust particles on the order of several microns in diameter getting mixed into the pressure-sensitive film 13 during use, which would reduce the risk of a malfunction.

[0044] (Configuration and Function of Pressure Sensor Head According to Second Embodiment) FIG. 5 is a diagram showing a pressure sensor head according to the second embodiment.

[0045] The pressure sensor head 2 differs from the pressure sensor head 1 in that it has a moisture-proof film 17. The configurations and functions of the components of the pressure sensor head 2 other than the moisture-proof film 17 are the same as the configurations and functions of the components of the pressure sensor head 1 that are assigned the same reference numerals, and therefore detailed explanations will be omitted here. Like the pressure sensor head 1, the pressure sensor head 2 is disposed in the pressure sensor device 100, and when excitation light 111 is incident, it emits detection light 112 having wavelength characteristics according to localized plasmon resonance caused by metal nanoparticles.

[0046] The moisture-proof film 17 is made of a moisture-proof synthetic resin such as a fluororesin, and is disposed so as to face the surface of the reflective film 14 that faces the pressure-sensitive film 13. The Young's modulus of the moisture-proof film 17 is several MPa to several hundred GPa, and the film thickness is 1 μm or less. The moisture-proof film 17 is disposed so that its outer edge covers the side surfaces of the pressure-sensitive film 13 and the reflective film 14, and is fixed to the housing 12. The moisture-proof film 17 may be formed using, for example, Cytop (registered trademark). The moisture-proof film 17 is formed by a well-known film-forming method such as spin coating.

[0047] (Actions and Effects of the Pressure Sensor Head According to the Second Embodiment) Because the pressure sensor head 2 has a moisture-proof membrane 17, there is less risk of liquid penetrating the pressure-sensitive membrane 13 in an environment where liquid is present around it, such as in a blood vessel, than with the pressure sensor head 1, and the pressure of the liquid present around it can be detected with even greater accuracy.

[0048] In addition, the pressure sensor head 2 has a moisture-proof film 17 that functions as a dust-proof film that prevents dust from entering the inside of the pressure sensor head 1 from the outside of the pressure sensor head 1, so similar to the pressure sensor head 1, it can suppress a decrease in yield and the occurrence of failures.

[0049] Furthermore, by forming the first slit 21 to the third slit 23 in the reflective film 14, the flexibility of the reflective film 14 is improved, and even though the pressure sensor head 1 has a moisture-proof film 17, a decrease in pressure detection sensitivity due to the pressure-sensitive film 13 can be suppressed.

[0050] FIG. 6(a) is a diagram showing pressure application conditions when the strain and displacement of the pressure-sensitive film 13 when pressure is applied to the pressure-sensitive film 13, the reflective film 14, and the moisture-proof film 18 are measured by simulation. FIG. 6(b) is a contour diagram showing the displacement of the pressure-sensitive film 13, the reflective film 14, and the moisture-proof film 18 when pressure is applied to the pressure-sensitive film 13, the reflective film 14, and the moisture-proof film 18. The simulations shown in FIGS. 6(a) and 6(b) were performed in the same manner as the simulations shown in FIGS. 4(a) and 4(b). In the simulations, pressure was applied to the region indicated by arrow A on the surface of the reflective film 14 opposite to the surface facing the pressure-sensitive film 13.

[0051] By forming the first slits 21 to the third slits 23 in the reflective film 14, the distortion of the pressure-sensitive film 13 was reduced to one-fifth of that when the reflective film 14 was not provided. By forming the first slits 21 to the third slits 23 in the reflective film 14, the distortion of the pressure-sensitive film 13 increased six times compared to when the first slits 21 to the third slits 23 were not formed. The detection sensitivity of the reflective film 14 increased six times as the distortion of the pressure-sensitive film 13 increased six times compared to when the first slits 21 to the third slits 23 were not formed.

[0052] (Modification of the pressure sensor head according to the embodiment) In the pressure sensor heads 1 and 2, the first slit 21 to the third slit 23, each of which is a single slit having a circular planar shape, are formed in the reflective film 14, but in the pressure sensor head of the embodiment, it is sufficient that the slits are formed in the reflective film.

[0053] FIG. 7(a) is a plan view of a reflective film according to a first modified example, FIG. 7(b) is a plan view of a reflective film according to a second modified example, and FIG. 7(c) is a plan view of a reflective film according to a third modified example.

[0054] In the reflective film 14a according to the first modification, first slits 21a to third slits 23a are formed so as to surround the reflective portion 20. Each of the first slits 21a to third slits 23a is a plurality of slits having an annular planar shape. Each of the first slits 21a to third slits 23a is similar to the first slits 21 to third slits 23 except that they are a plurality of slits, and therefore detailed description thereof will be omitted here.

[0055] In the reflective film 14b according to the second modification, first to third slits 21b to 23b are formed so as to connect opposing sides. The first to third slits 21b to 23b are formed so as to intersect at the center of the reflective portion 20. In the reflective film 14b according to the second modification, the first to third slits 21b to 23b are formed so as to intersect at the reflective portion 20, which may attenuate the intensity of the detection light 112. However, the amount of shift in the peak wavelength of the absorption spectrum used by the pressure sensor device 100 to determine pressure does not depend on the intensity of the detection light 112, so the first to third slits 21b to 23b have little effect on the detection sensitivity.

[0056] In the reflective film 14c according to the third modification, a plurality of slits 24 are formed randomly. The positions at which the plurality of slits 24 are arranged, and the lengths, widths, and shapes of the plurality of slits 24 are different from one another. The plurality of slits 24 are formed by applying pressure so as to apply a stress equal to or greater than the yield strength of the material forming the reflective film 14c. For example, when the plurality of slits 24 are made of aluminum, the slits 24 are formed in the reflective film 14c by applying a pressure equal to or greater than 100 MPa, which is the yield strength of aluminum. Like the first slits 21b to the third slits 23b, the slits 24 have little effect on detection sensitivity.

[0057] Furthermore, by adjusting the pressure applied to the reflective film 14c when forming the plurality of slits 24, each of the plurality of slits 24 is formed to a width that makes it difficult for liquid to penetrate. By forming the plurality of slits 24 to a width that makes it difficult for liquid to penetrate, the reflective film 14c can detect the pressure of liquid present in the surroundings in an environment where liquid is present in the surroundings, such as in a blood vessel. [Explanation of symbols]

[0058] 1 Pressure sensor head 10 Optical Fiber 11 Adhesive material 12. Case 13 Pressure-sensitive membrane 14 Reflective film 15 Flexible materials 16 Metal nanoparticles 17 Moisture-proof membrane

Claims

1. The housing and an optical fiber having a first end to which excitation light is incident and a second end from which the excitation light is emitted, the second end being fixed to the housing; an optically transparent pressure-sensitive membrane formed of a flexible material containing metal nanoparticles that exhibit localized plasmon resonance, the optically transparent pressure-sensitive membrane having an incident surface onto which the excitation light is incident from the second end and a pressure surface onto which pressure is applied, the optically transparent pressure-sensitive membrane distorting in response to pressure applied to the pressure surface, thereby shifting a peak wavelength of an absorption spectrum of localized plasmon resonance due to the metal nanoparticles; a reflective film having a plurality of slits formed therein and disposed so as to face the pressure surface; When the excitation light is incident on the first end, detection light having wavelength characteristics according to localized plasmon resonance of the metal nanoparticles is emitted from the first end. A pressure sensor head comprising:

2. The pressure sensor head according to claim 1 , wherein the plurality of slits are formed around a reflective portion that reflects the excitation light that has passed through the pressure-sensitive film.

3. The pressure sensor head according to claim 2 , wherein the plurality of slits are arranged to form a plurality of annular rings with different diameters.

4. The pressure sensor head according to claim 3 , wherein each of the plurality of circular rings is formed by a single slit.

5. The pressure sensor head according to claim 3 , wherein each of the plurality of circular rings is formed by a plurality of the slits.

6. The pressure sensor head according to claim 1 , wherein the plurality of slits are formed randomly.

7. a light emitting element that emits excitation light; a pressure sensor head containing metal nanoparticles that exhibit localized plasmon resonance, and emitting detection light having wavelength characteristics according to the localized plasmon resonance of the metal nanoparticles when the excitation light is incident thereon; a spectroscope that separates the detected light into wavelengths and detects the intensity of the separated light; a computing device that extracts a peak wavelength of an absorption spectrum of localized plasmon resonance caused by the metal nanoparticles from the intensity of light detected by the spectrometer, determines a pressure applied to the pressure sensor head from the extracted peak wavelength, and outputs a pressure signal indicating the determined pressure, The pressure sensor head includes: The housing and an optical fiber having a first end to which excitation light is incident and a second end from which the excitation light is emitted, the second end being fixed to the housing; an optically transparent pressure-sensitive membrane formed of a flexible material containing the metal nanoparticles, the optically transparent pressure-sensitive membrane having an incident surface onto which the excitation light is incident from the second end and a pressure surface onto which pressure is applied, the optically transparent pressure-sensitive membrane being deformed in response to pressure applied to the pressure surface, thereby shifting a peak wavelength of an absorption spectrum of localized plasmon resonance due to the metal nanoparticles; a reflective film having a plurality of slits formed therein and disposed so as to face the pressure surface; When the excitation light is incident on the first end, the detection light having wavelength characteristics according to localized plasmon resonance of the metal nanoparticles is emitted from the first end. A pressure sensor device comprising:

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