JP7361388B2 - Sensors, sensor manufacturing methods, pressure or temperature measurement systems and measurement methods - Google Patents

Description

The present disclosure relates to a sensor, a method for manufacturing the same, a pressure or temperature measurement system and a measurement method, and more particularly relates to a technique for measuring the pressure applied to an object or the temperature of an object.

Sensing technology using metal nanoparticles has been proposed. For example, JP-A-2007-170932 (Patent Document 1) discloses a metal fine particle-chromogenic composite material. This composite material has a structure in which fine metal particles are arranged in contact with or close to a matrix that is a chromogenic material. Composite materials can reversibly shift the wavelength of the surface plasmon resonance (SPR) or the peak value of light absorption or light scattering of metal particles by reversibly controlling the optical change of the chromogenic material. Can be controlled.

Japanese Patent Application Publication No. 2007-170932 Japanese Patent Application Publication No. 2012-137485

In order to put sensors (specifically, pressure sensors or temperature sensors) using metal nanoparticles into practical use, there is a need for sensors with simpler configurations. Moreover, it is preferable that a sensor with such a simple configuration can be manufactured as easily as possible.

The present disclosure has been made to solve the above problems, and an object of the present disclosure is to provide a sensor having a simple configuration using metal nanoparticles. Another object of the present disclosure is to provide a technology that allows easy manufacture of a sensor using metal nanoparticles.

(1) A sensor according to an aspect of the present disclosure is a sensor for measuring pressure or temperature. This sensor includes a photoresponsive material including a liquid crystal having a helical structure and metal nanoparticles, and a light-transmitting layer that covers at least a portion of the photoresponsive material and is transparent to light irradiated onto the photoresponsive material. Equipped with.

(2) The liquid crystal includes at least one of cholesteric liquid crystal, smectic liquid crystal, and TGB (Twisted Grain Boundary) liquid crystal.

(3) The helical structure of the liquid crystal has a helical pitch determined by dividing the wavelength of the light irradiated onto the photoresponsive material by the refractive index of the photoresponsive material. (4) The wavelength of the light irradiated to the photoresponsive material is included in the visible range. The helical pitch of the helical structure of liquid crystal is on the order of submicrometers. (5) The wavelength of the light irradiated to the photoresponsive material is included in the infrared region. The helical pitch of the helical structure of liquid crystal is on the order of micrometers.

(6) A method for manufacturing a sensor according to another aspect of the present disclosure is a method for manufacturing a sensor for measuring pressure or temperature. This manufacturing method involves the steps of preparing a metal nanoparticle dispersion in which metal nanoparticles are dispersed by a reduction method, and introducing a material capable of producing a liquid crystal having a helical structure into the metal nanoparticle dispersion. and preparing a liquid crystal.

(7) The average interparticle distance of metal nanoparticles in the metal nanoparticle dispersion is in the range of nanometer order to micrometer order. (8) The average interparticle distance of the metal nanoparticles in the metal nanoparticle dispersion ranges from the submicrometer order to the single micrometer order.

(9) A measurement system according to yet another aspect of the present disclosure measures the pressure applied to the object or the temperature of the object using a sensor installed on the object. The sensor has a photoresponsive material that includes a liquid crystal with a helical structure and metal nanoparticles. The measurement system includes a photodetector that detects light irradiated onto the sensor, and an arithmetic device that calculates the pressure or temperature of the object by subjecting the signal from the photodetector to predetermined signal processing.

(10) The photodetector includes a camera that photographs the sensor. The calculation device calculates the pressure or temperature of the object based on the color information of the image taken by the camera.

(11) The photodetector includes a spectrometer that separates the transmitted light or reflected light from the sensor. The calculation device calculates the pressure or temperature of the object based on the peak wavelength of the absorbance spectrum or reflection spectrum acquired by the spectrometer.

(12) A measurement method according to an aspect of the present disclosure is a measurement method for measuring the pressure applied to the object or the temperature of the object using a sensor installed on the object. The sensor has a photoresponsive material that includes a liquid crystal with a helical structure and metal nanoparticles. The measurement method includes the steps of detecting the light irradiated onto the sensor with a photodetector, and calculating the pressure or temperature of the object by subjecting the signal from the photodetector to predetermined signal processing.

(13) The method further includes the step of irradiating the photoresponsive material with light having a wavelength equal to the refractive index of the photoresponsive material multiplied by the helical pitch of the helical structure of the liquid crystal.

According to the present disclosure, it is possible to provide a sensor (pressure sensor or temperature sensor) that uses metal nanoparticles and has a simple configuration. Further, according to the present disclosure, a sensor using metal nanoparticles can be easily manufactured.

1 is a diagram schematically showing the overall configuration of a pressure measurement system according to Embodiment 1. FIG. It is a figure showing the example of composition of a measurement jig in more detail. FIG. 3 is a diagram showing a configuration example of a pressure sensor 5 in Embodiment 1. FIG. It is a figure which shows the image of a pressure sensor. FIG. 2 is a diagram for explaining a liquid crystal used as a photoresponsive material. FIG. 3 is a conceptual diagram for explaining how cholesteric liquid crystal changes with pressure changes. FIG. 2 is a conceptual diagram for explaining the appearance of gold nanoparticles in a gold nanoparticle-doped liquid crystal. 3 is a flowchart showing a manufacturing procedure of the pressure sensor according to Embodiment 1. FIG. FIG. 3 is a diagram showing changes over time in the appearance of a gold nanoparticle-doped liquid crystal. FIG. 3 is a diagram for comparing the appearance of pressure sensors. FIG. 3 is a diagram showing images of a measurement jig and a pressure sensor when pressure is applied. 7 is a flowchart showing pressure measurement processing in the first embodiment. FIG. 3 is a diagram showing an example of spectrum measurement results for a gold nanoparticle-free sample. It is a figure which shows the example of the spectrum measurement result in a diluted sample. It is a figure which shows the example of the spectrum measurement result in a reference sample. It is a figure showing an example of a spectrum measurement result in a concentrated sample. It is a figure which shows the measurement result of the absorbance spectrum at the time of various pressure application. FIG. 3 is a diagram showing the relationship between the peak wavelength and pressure determined from the absorbance spectrum. It is a figure which shows the measurement result of the reflection spectrum at the time of various pressure application. FIG. 3 is a diagram showing the relationship between the peak wavelength determined from the reflection spectrum and the pressure. FIG. 6 is a diagram showing a transmitted image taken by a camera when pressure is applied. FIG. 6 is a diagram showing a reflected image taken by a camera when pressure is applied. FIG. 2 is a diagram schematically showing the overall configuration of a pressure measurement system according to a second embodiment. FIG. 2 is a diagram showing a state of measurement in the pressure measurement system 2. FIG. It is a figure showing an example of a target object. 7 is a flowchart showing pressure measurement processing in Embodiment 2. FIG.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In addition, the same reference numerals are attached to the same or corresponding parts in the figures, and the description thereof will not be repeated.

<Definition of terms>
In the present disclosure and its embodiments, "metal nanoparticles" are metal particles having a particle size on the order of nanometers. A "metal nanoparticle aggregate" is an aggregate formed by aggregation of a plurality of metal nanoparticles. "Metal nanoparticle integrated structure" is a structure in which multiple metal nanoparticles are fixed to the surface of beads via interaction sites, and are arranged at intervals equal to or less than the diameter of the metal nanoparticles. It is.

In the present disclosure and its embodiments, "nanometer order" includes a range from 1 nm to 1000 nm (=1 μm). "Nanometer order" typically ranges from 1 to 100 nm, preferably from 1 to 50 nm.

In the present disclosure and its embodiments, "micrometer order" includes a range from 1 μm to 1000 μm (=1 mm). “Submicrometer order” includes a range from 0.1 μm (=100 nm) to 1 μm. "Single micrometer order" includes a range from 1 μm to 10 μm. Therefore, "the range from submicrometer order to single micrometer order" means the range from 0.1 μm to 10 μm.

In the present disclosure and its embodiments, the "wavelength range of localized surface plasmon resonance induced in metal nanoparticles" refers to, for example, a wavelength range corresponding to the full width at half maximum of the peak of localized surface plasmon resonance of metal nanoparticles. It is. This wavelength range typically falls within the visible range of 400 nm to 700 nm.

In the present disclosure and embodiments thereof, the ultraviolet range refers to wavelength ranges from 200 nm to 360 nm. The visible range means a wavelength range of 360 nm to 700 nm. Infrared region means a wavelength region of 700 nm to 5 μm. "White light" means light in the wavelength range from the ultraviolet region to the near-infrared region (for example, the wavelength range of 200 nm to 1100 nm). The white light may be continuous light or pulsed light.

In the present disclosure and its embodiments, "having optical transparency" means a property in which the intensity of light passing through a substance is greater than zero. When light passes through a material, the remaining light energy may be absorbed, scattered or reflected by the material. The wavelength range of the light may be any of the ultraviolet, visible, and near-infrared regions, a region that spans two of these three regions, or a region that spans all three regions. But that's fine. Light transmittance can be defined, for example, by a range of transmittance. In this case, the lower limit of the transmittance range is not particularly limited as long as it is greater than 0.

[Embodiment 1]
<Overall configuration of pressure measurement system>
FIG. 1 is a diagram schematically showing the overall configuration of a pressure measurement system according to a first embodiment. Hereinafter, the x direction and the y direction represent the horizontal direction. The x direction and the y direction are orthogonal to each other. The z direction represents the vertical direction. The direction of gravity is downward in the z direction.

Referring to FIG. 1, pressure measurement system 1 measures the pressure (load) applied to the surface of object 9. In the embodiment described below, the pressure measurement system 1 is an experimental system for measuring the distribution of pressure applied to the surface of the object 9 by a weight. The pressure measurement system 1 includes a light source 11, a measurement jig 12, a stage 13, an objective lens 14, an optical component 15, a spectrometer 16, a camera 17, and a controller 18.

The light source 11 emits light that illuminates the pressure sensor 5 (see FIGS. 2 to 4) installed on the measurement jig 12. Preferably, this irradiation light is white light. In the embodiments described below, a halogen lamp is used as the light source 11. However, the light source 11 may be an LED (Light Emitting Diode), a fluorescent lamp, or the like.

However, the light source 11 may be a light source that emits light other than white light. Although the details will be described later, if the light source 11 includes at least part of the reflection wavelength range of liquid crystal and at least part of the wavelength range of localized surface plasmon resonance induced by metal nanoparticles, , a light source that emits light in a wavelength range narrower than the wavelength range of white light may be used.

The measurement jig 12 is configured to be able to apply a desired pressure to the pressure sensor 5 placed on the object 9. Furthermore, the measurement jig 12 is configured to be able to irradiate the pressure sensor 5 with light from the light source 11 . An example of the configuration of the measurement jig 12 will be explained with reference to FIG.

The stage 13 holds the measurement jig 12. The stage 13 is, for example, an XYZ-axis stage that can move an object (measurement jig 12 in this example) placed on the stage 13 in the x direction, y direction, and z direction. By employing the XYZ axis stage, the light from the light source 11 can be irradiated onto the target position of the pressure sensor 5.

The objective lens 14 takes in the light irradiated onto the pressure sensor 5 from the light source 11. Although FIG. 1 shows an optical system in which light transmitted through the pressure sensor 5 is taken into the objective lens 14, the light reflected by the pressure sensor 5 may be taken into the objective lens 14. The light taken into the objective lens 14 reaches the optical component 15.

The optical component 15 is appropriately selected from mirrors, dichroic mirrors, prisms, optical fibers, and the like. In this embodiment, a dichroic mirror is used as the optical component 15. The optical system of the pressure measurement system 1 is adjusted so that light captured by the objective lens 14 is guided by an optical component 15 to a spectrometer 16 and a camera 17 .

The spectrometer 16 measures the spectrum (absorbance spectrum or reflection spectrum) of the pressure sensor 5 according to a command from the controller 18 and outputs the measurement result to the controller 18 . The spectrometer 16 is preferably a spectrometer (ultraviolet-visible-infrared spectrophotometer) capable of measuring spectra in the wavelength range from the ultraviolet region to the near-infrared region. Instead of the spectrometer 16, a camera (multispectral camera or hyperspectral camera) capable of acquiring wavelength information may be employed. The smaller the wavelength resolution of the spectrometer 16, the better. The wavelength resolution of the spectrometer 16 is, for example, 10 nm or less, 5 nm or less, 2 nm or less, or 1 nm or less, but is not limited thereto. Note that the spectrometer 16 corresponds to a "photodetector" according to the present disclosure.

The camera 17 photographs the pressure sensor 5 according to a command from the controller 18 and outputs the photographed image to the controller 18. In the first embodiment, the camera 17 is an auxiliary device for observing changes in the pressure sensor 5, and is not used for pressure measurement (see FIGS. 20 and 22). Therefore, the camera 17 can be omitted.

The controller 18 is, for example, a personal computer, and includes a processor 181 such as a CPU (Central Processing Unit), a memory 182 such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and an input/output port (not shown). including. Controller 18 controls spectrometer 16 and camera 17. Further, the controller 18 calculates the pressure distribution on the surface of the object 9 by extracting predetermined information (described later) from the spectrum measured by the spectrometer 16. Furthermore, the controller 18 is also configured to record an image taken by the camera 17 (a transmitted image of the pressure sensor 5 when pressure is applied). Note that the controller 18 corresponds to a "computation device" according to the present disclosure.

<Configuration of measurement jig>
FIG. 2 is a diagram showing an example of the configuration of the measuring jig 12 in more detail. Referring to FIG. 2, measurement jig 12 includes slide glasses 121 and 122 and weights 123 and 124.

The slide glasses 121 and 122 are glass plates having a flat rectangular parallelepiped shape (flat plate shape). The slide glass 121 is placed on the top surface of the pressure sensor 5, and the slide glass 122 is placed on the bottom surface of the object 9. The slide glass 121 and the slide glass 122 sandwich the pressure sensor 5 and the object 9 therebetween. However, in the examples described later, in order to evaluate the performance of the pressure sensor 5 itself, pressure measurement results are shown in a state where there is no object 9 (a state where the pressure sensor 5 is alone). Note that the slide glasses 121 and 122 are also only constituent elements for facilitating pressure application, and are not essential.

The weight 123 is installed near one end of the long side of the slide glass 121 . The weight 124 is installed near the other end of the long side of the slide glass 121 . By arranging the weights 123 and 124 at both ends of the slide glass 121 in this manner, pressure can be equally applied to the pressure sensor 5 and the object 9. In addition, in the example described later, each of the weights 123 and 124 was a number of coins equivalent to 50 g, 100 g, 150 g, or 200 g.

<Configuration of pressure sensor>
FIG. 3 is a diagram showing a configuration example of the pressure sensor 5 in the first embodiment. Referring to FIG. 3, pressure sensor 5 includes a substrate 51, a transparent film 52, a photoresponsive material 53, and a spacer 54.

The substrate 51 is placed on the bottom surface of the photoresponsive material 53 and the spacer 54, and the transparent film 52 is placed on the top surface of the photoresponsive material 53 and the spacer 54. Thereby, the substrate 51 and the transparent film 52 sandwich the photoresponsive material 53 and the spacer 54 from above and below. The substrate 51 provides mechanical strength to the pressure sensor 5. The transparent film 52 is made of a material that transmits light emitted from the light source 11 (for example, white light). The transparent film 52 corresponds to a "light-transmitting layer" according to the present disclosure.

In this example, the material of the substrate 51 and the transparent film 52 is a transparent resin or transparent polymer such as polyethylene terephthalate (PET) or polycarbonate. However, the materials of the substrate 51 and the transparent film 52 are not limited to resin or polymer, and may be glass, quartz, or the like.

Note that it is not essential that the substrate 51 have optical transparency. If the transparent film 52 located on the side irradiated with light from the light source 11 has a light transmittance, the substrate 51 is not required to have a light transmittance.

The photoresponsive material 53 is a gel material that changes color depending on the pressure applied to the photoresponsive material 53. Photoresponsive material 53 includes liquid crystal and metal nanoparticles. The structure of the photoresponsive material 53 will be explained in detail later.

The spacer 54 is provided between the substrate 51 and the transparent film 52 so as to surround the photoresponsive material 53. Thereby, the spacer 54 secures a space for holding the photoresponsive material 53 between the substrate 51 and the transparent film 52, and prevents the photoresponsive material 53 from flowing out from the pressure sensor 5. For example, double-sided tape can be used as the spacer 54. Note that the spacer 54 is not an essential component of the pressure sensor 5 and can be omitted.

In the examples described below, both the substrate 51 and the transparent film 52 are transparent conductive films manufactured by Teijin Ltd. (model number: PFC100-D150). As the spacer 54, double-sided tape (thickness: about 0.12 mm) manufactured by Nichiban Co., Ltd. was used. The size of the slide glasses 121 and 122 was 26 mm x 76 mm x 1 mm.

FIG. 4 is a diagram showing an image of the pressure sensor 5. FIG. 4 shows an image taken from above in which the pressure sensor 5 is sandwiched between slide glasses 121 and 122 for performance evaluation of the pressure sensor 5.

<Pressure measurement mechanism>
FIG. 5 is a diagram for explaining liquid crystal used in the photoresponsive material 53. In this embodiment, cholesteric liquid crystal doped with gold nanoparticles is used as the photoresponsive material 53. Hereinafter, this material will also be referred to as "gold nanoparticle-doped liquid crystal." Note that the metal nanoparticles that can be used in the photoresponsive material 53 are not limited to gold nanoparticles, and may be silver nanoparticles, for example.

As shown in FIG. 5, cholesteric liquid crystal has a helical structure. More specifically, cholesteric liquid crystal has a layered structure in which liquid crystal molecules are arranged in a spiral around an axis. The liquid crystal molecules within each layered structure are oriented in the same direction. Hereinafter, the length in the axial direction when the layered structure of liquid crystal molecules makes one revolution around the axis will be referred to as the "helical pitch" and will be expressed as p. Adjacent layered structures are twisted at a certain angle in a certain direction around the axis (torsion angle). In general, the helix angle varies from a few minutes to several degrees, so that the helical pitch p can also be widely distributed from the submicrometer order to larger orders (eg, millimeter order).

When the pressure applied to the pressure sensor 5 changes under light irradiation from the light source 11, the color of the pressure sensor 5 changes due to both the effect of the cholesteric liquid crystal and the effect of the gold nanoparticles.

FIG. 6 is a conceptual diagram for explaining how cholesteric liquid crystal changes as pressure changes. FIG. 6 schematically shows five liquid crystal layers 61 to 65 included in the cholesteric liquid crystal. Gold nanoparticles 7 are distributed on each liquid crystal layer.

Cholesteric liquid crystal selectively reflects light with a wavelength equal to the helical pitch p multiplied by the refractive index of the medium (gel material). When adding a small amount of cholesteric liquid crystal molecules to water (ultrapure water), the refractive index n _w of the gel material can be approximated to be equal to the refractive index of water (n _w ≈1.33). Therefore, the wavelength λ of the light reflected by the cholesteric liquid crystal is expressed by the following formula (1). From this relational expression, it can be seen that as the helical pitch p becomes narrower, the wavelength λ of the reflected light becomes shorter (a short wavelength shift occurs).
λ= _nwp ...(1)

As an example, when the helical pitch p=480 nm, the reflected light is red because the wavelength λ is approximately 640 nm. When the helical pitch p=300 nm, the wavelength λ≈400 nm, and the reflected light changes to purple. In this way, reflected light of a specific wavelength corresponding to the helical pitch p can be obtained from the cholesteric liquid crystal.

When the pressure applied to the pressure sensor 5 increases, the cholesteric liquid crystal contracts and the helical pitch p narrows. In this case, the wavelength of the reflected light becomes shorter due to the reflection characteristics of the cholesteric liquid crystal. Conversely, when the pressure applied to the pressure sensor 5 decreases, the cholesteric liquid crystal expands and the helical pitch p widens. In this case, the wavelength of the reflected light becomes longer due to the reflection characteristics of the cholesteric liquid crystal.

Note that when measuring the wavelength change of reflected light in the visible range (and when the medium of cholesteric liquid crystal is water), the helical pitch p is on the submicrometer order (480 nm, 300 nm, etc. in the above example). . However, by setting the helical pitch p to 1 μm or more (on the order of micrometers), it is also possible to measure changes in the wavelength of reflected light in the infrared region. Further, although the explanation has been given using reflected light as an example, a similar wavelength change is also observed in absorbed light.

FIG. 7 is a conceptual diagram for explaining the appearance of gold nanoparticles in a gold nanoparticle-doped liquid crystal. Referring to FIG. 7, in a cholesteric liquid crystal doped with gold nanoparticles, the above relational expression (1) is modified as follows (see equation (2) below).
λ=( _nw + _ΔnGNP )p...(2)

In equation (2), the change in refractive index due to doping of gold nanoparticles is expressed as Δn _GNP . From equation (2), it can be seen that as the refractive index (n _w +Δn _GNP ) becomes higher, the wavelength λ of the reflected light becomes longer.

When the gold nanoparticle concentration is low (see "dilution" in the figure), the contribution of the gold nanoparticles to the refractive index Δn _GNP is negligibly small (Δn _GNP ≈0). However, as shown in "Standard" and "Concentration" in the figure, when the concentration of gold nanoparticles reaches a certain high concentration, the interaction between the gold nanoparticles becomes stronger and Δn _GNP (>0) increases. As a result, the refractive index (n _w +Δn _GNP ) increases, and the wavelength λ of the reflected light increases.

On the other hand, the strength of the interaction between gold nanoparticles (cooperative effect of localized surface plasmons) varies depending on the distance between the gold nanoparticles. Then, depending on the strength of the cooperative effect of localized surface plasmons, the direction and magnitude (shift amount) of the peak wavelength shift in the absorbance spectrum or reflection spectrum change (see patent (See Reference 2). More specifically, when the distance between the gold nanoparticles becomes sufficiently close (for example, when the helical pitch becomes less than p), the peak wavelength shifts to longer wavelengths due to the cooperative effect of localized surface plasmons of the gold nanoparticles. This amount of shift increases as the distance between the gold nanoparticles decreases. Although details will be described later, the longer wavelength shift of the peak derived from the localized surface plasmon of the gold nanoparticles can act in the direction of weakening the shorter wavelength shift of the peak derived from the cholesteric liquid crystal.

In this way, the direction and magnitude of the wavelength shift caused by the cholesteric liquid crystal change depending on the pressure applied to the pressure sensor 5. Furthermore, the direction and magnitude of the peak wavelength shift due to the cooperative effect of localized surface plasmons is determined depending on the concentration of gold nanoparticles. Therefore, the spectrum of the pressure sensor 5 is analyzed and the correspondence between the spectrum and pressure is determined in advance. Then, the analysis results are stored in the memory 182 of the controller 18 as a map, relational expression, or the like. By referring to this correspondence relationship, the pressure applied to the pressure sensor 5 can be calculated based on the spectrum of the pressure sensor 5.

Generally, cholesteric liquid crystals are produced by mixing nematic liquid crystals and chiral additives (chiral materials) in a specific range of ratios. The helical pitch p can be adjusted by changing the type and/or content of the chiral material. For example, the helical pitch p can be narrowed by increasing the content of chiral material.

Furthermore, the distance between the gold nanoparticles can be adjusted by changing the particle size and/or content (concentration) of the gold nanoparticles. By increasing the particle size of the gold nanoparticles or increasing the concentration of the gold nanoparticles, the distance between the gold nanoparticles can be reduced.

It is also conceivable to use only either cholesteric liquid crystal or gold nanoparticles in a pressure sensor. In contrast, the pressure sensor 5 according to the present embodiment is a so-called hybrid pressure sensor that employs a photoresponsive material 53 that includes both cholesteric liquid crystal and gold nanoparticles. As explained below, such a hybrid pressure sensor can produce an appropriate degree of color change in a desired wavelength range depending on the measurement application by appropriately setting the combination of the multiple parameters mentioned above. One of the advantages is that the photoresponsive material 53 can be prepared.

First, by setting the helical pitch p of the cholesteric liquid crystal to an appropriate value, you can adjust the wavelength of the reflected light (reference wavelength) before applying pressure, and the approximate wavelength range ( wavelength range) can be adjusted. Specifically, by setting the helical pitch p to the submicrometer order, the wavelength range of the reflected light can be made into the visible range. In particular, the visibility of the pressure sensor 5 can be improved by adjusting the reference wavelength or the changing wavelength range to be located within a wavelength range in which the sensitivity of the human eye (specific luminous efficiency) is high among the visible range. Furthermore, as described above, as the helical pitch p narrows with the application of pressure, the wavelength of the reflected light becomes shorter. Therefore, by adjusting the reference wavelength before applying pressure so that it is located in the red or infrared wavelength range, all or most of the changing wavelength range can be made to fall within the visible range. That is, it is possible to widen the pressure range in which color changes can be observed with a visible camera or the human eye.

On the other hand, by setting the particle size or concentration of gold nanoparticles to appropriate values, the sensitivity of color change to pressure changes (also called resolution) can be adjusted depending on the measurement application. When it is desired to measure minute pressure changes, the sensitivity to color changes can be made high, and conversely, when it is desired to measure relatively large pressure changes, the sensitivity to color changes can be intentionally made low. As described above, according to the present embodiment, by making the photoresponsive material 53 a hybrid type of cholesteric liquid crystal and gold nanoparticles, it can be used in a range where the relative luminous efficiency is high and suitable for the amount of pressure change to be measured. A sensitive pressure sensor 5 can be realized.

Note that cholesteric liquid crystal is not the only type of liquid crystal that can be used for the photoresponsive material 53. Liquid crystals are broadly classified into cholesteric liquid crystals, nematic liquid crystals, and smectic liquid crystals depending on their molecular structure. Among these liquid crystals, smectic liquid crystals can also be used as the photoresponsive material 53 because they have a spiral mode (smectic C* phase) in which liquid crystal molecules rotate in each layer. Furthermore, a liquid crystal having a defective structure called TGB (Twisted Grain Boundary) phase can also be used as the photoresponsive material 53 because it has a helical structure.

Furthermore, although an example in which the photoresponsive material 53 is applied to measuring the pressure of the object 9 has been described here, temperature changes in the object 9 can also be measured using the photoresponsive material 53. Cholesteric liquid crystal expands as the temperature rises and contracts as the temperature falls. The mechanism for measuring temperature changes is similar to the mechanism for pressure changes, so detailed description will not be repeated.

<Sensor manufacturing flow>
FIG. 8 is a flowchart showing the manufacturing procedure of the pressure sensor 5 according to the first embodiment. Referring to FIG. 8, in step S11, a metal nanoparticle dispersion liquid in which metal nanoparticles are dispersed in a dispersion medium is prepared. In the examples described below, the metal nanoparticles are gold nanoparticles, and the dispersion medium is ultrapure water.

For the preparation of the gold nanoparticle dispersion, it is desirable to employ an in-solution reduction method (so-called reduction method) using a solution containing gold ions (gold complex ions) and a reducing agent. For example, tetrachloroauric acid can be reduced with citric acid. Sputtering is also known as a method for preparing gold nanoparticle dispersions, but sputtering cannot be adopted. This is because the sputtering method does not allow gold nanoparticles to be uniformly distributed on the liquid crystal layer.

In step S12, a gold nanoparticle-doped liquid crystal (photoresponsive material 53) is prepared by introducing liquid crystal molecules into the gold nanoparticle dispersion medium prepared in step S11. In this example, hydroxypropyl cellulose (HPC), which is a type of cellulose derivative, is used as the cholesteric liquid crystal molecule. However, other known materials (such as cholesteryl carbonate and cholesteryl ester) may be used as raw materials for cholesteric liquid crystals.

It is also conceivable to reverse the order of step S11 and step S12, first introducing cholesteric liquid crystal molecules into ultrapure water, and then dispersing gold nanoparticles. However, even in this case, a state in which gold nanoparticles are uniformly distributed on the liquid crystal layer is not formed. Therefore, it is not suitable for manufacturing the pressure sensor 5.

In step S13, gold nanoparticle-doped liquid crystal is applied onto the substrate 51. Further, the applied gold nanoparticle-doped liquid crystal is fixed using spacers 54.

In step S14, the gold nanoparticle-doped liquid crystal coated on the substrate 51 is covered with a transparent film 52. In FIG. 3, the entire surface of the gold nanoparticle-doped liquid crystal (photoresponsive material 53) is covered with the transparent film 52, but it is only necessary that at least a portion of the gold nanoparticle-doped liquid crystal be covered with the transparent film 52.

In step S15, the substrate 51 and the transparent film 52 are bonded. The mode of joining is not particularly limited, and may be adhesive or welded, or may be mechanically fixed. This completes the pressure sensor 5.

As described above, the pressure sensor 5 according to the first embodiment is a simple structure that is simply sandwiched between the substrate 51 in which liquid crystal molecules having a helical structure such as cholesteric liquid crystal are introduced into a gold nanoparticle dispersion and the transparent film 52. It has a unique structure. Patent Document 2 discloses a pressure sensor and a temperature sensor using a metal nanoparticle integrated structure. However, production of a metal nanoparticle integrated structure requires a step of immobilizing metal nanoparticles on the surface of beads via interaction sites such as thiol groups (see, for example, paragraph [0036] of Patent Document 2). On the other hand, in this embodiment, it is sufficient to introduce cholesteric liquid crystal molecules into the gold nanoparticle dispersion, and there is no need to prepare a gold nanoparticle integrated structure. Therefore, pressure sensors or temperature sensors using gold nanoparticles can be manufactured more easily.

Note that the gold nanoparticle dispersion that can be used in the pressure sensor 5 does not require that all the gold nanoparticles be dispersed, and some of the metal nanoparticles may be aggregated. In other words, the gold nanoparticle dispersion may include a metal nanoparticle aggregate in which a plurality of metal nanoparticles aggregate.

<Exterior observation>
The appearance of the gold nanoparticle-doped liquid crystal and pressure sensor 5 manufactured according to the manufacturing procedure described above was observed. First, a gold nanoparticle dispersion liquid with a concentration of 1.059 nM was prepared using gold nanoparticles with a particle size of 30 nm. A gold nanoparticle-doped liquid crystal was prepared by introducing 1.0 g of cholesteric liquid crystal molecules (HPC) into 0.65 g of a gold nanoparticle dispersion. Hereinafter, a sample using this stock solution will be referred to as a "reference sample."

A gold nanoparticle dispersion containing gold nanoparticles in a 10 times higher concentration (10.59 nM) than the stock solution was prepared. The same amount (1.0 g) of HPC was introduced into a gold nanoparticle dispersion with a concentration 10 times higher than the same amount (0.65 g) to prepare a gold nanoparticle-doped liquid crystal. This sample is called a "concentrated sample." On the contrary, a gold nanoparticle dispersion liquid was prepared in which the concentration of gold nanoparticles was 10 times lower (0.1059 nM) than in the stock solution. The same amount (1.0 g) of HPC was introduced into the same amount (0.65 g) of a gold nanoparticle dispersion with a concentration 10 times lower to prepare a gold nanoparticle-doped liquid crystal. This sample is called a "diluted sample."

Normally, when concentrating a gold nanoparticle dispersion, centrifugation is performed to remove the supernatant, and the gold nanoparticles remaining at the bottom are used. Because gold nanoparticles are small, they may not completely settle even after centrifugation. When spectroscopically measured using an ultraviolet-visible-infrared spectrophotometer (UV-vis), the concentration of gold nanoparticles in the concentrated sample is believed to be approximately 3.752 nM (ie, 3.543 times concentrated). On the other hand, when diluting the gold nanoparticle dispersion liquid, centrifugation is not performed, so a concentration close to the expected concentration can be obtained. From the UV-vis results, the concentration of gold nanoparticles in the diluted sample is considered to be approximately 0.111 nM (ie, 9.522 times diluted).

Furthermore, for comparison, a sample containing no gold nanoparticles was prepared. More specifically, the same amount (1.0 g) of HPC was introduced into 0.65 g of ultrapure water. This sample will be described as a "gold nanoparticle free (non-containing) sample."

FIG. 9 is a diagram showing changes in the appearance of gold nanoparticle-doped liquid crystal over time. In FIG. 9, from left to right, concentrated samples, reference samples, diluted samples, and gold nanoparticle-free samples are arranged in this order. Note that each sample was stored in a storage container (screw tube).

Immediately after preparation and one day after preparation, the diluted sample and the gold nanoparticle-free sample were white. On the other hand, the reference sample had a light reddish-purple color, and the concentrated sample had a deep reddish-purple color. Almost no color unevenness was observed in any of the samples. In contrast, the color of each sample changed after several days of preparation. Specifically, the color of each sample partially (spotted) changed from blue to orange.

FIG. 10 is a diagram for comparing the appearance of the pressure sensor 5. In FIG. 10, from left to right, pressure sensors fabricated using a gold nanoparticle-free sample, a diluted sample, a reference sample, and a concentrated sample are shown, respectively. The center of the gold nanoparticle-free sample was orange, and the periphery was green. On the other hand, the colors of other samples containing gold nanoparticles were orange to red.

The average interparticle distance (also called particle density or particle spacing) d of gold nanoparticles in each sample is the concentration of gold nanoparticles in the gold nanoparticle dispersion liquid (c = 0.111 nM, 1.059 nM, 3 .752 nM) and Avogadro's number is _NA (NA≈6.02×10 ²³ ), it can be estimated according to the following formula (3).
d={1/(c× _NA )} ^1/3 ...(3)

The average interparticle distance d1 in the diluted sample was d1 = 2.46 μm. The average interparticle distance d2 in the reference sample is d2=1.16 μm. The average interparticle distance d3 in the concentrated sample is d3=0.761 μm. Thus, the average interparticle distances d1 to d3 range from submicrometer order to single micrometer order.

Note that the average interparticle distances d1 to d3 calculated here are the distances when the gold nanoparticles are dispersed in the dispersion medium (ultrapure water). It is considered that the average interparticle distance in a state where the gold nanoparticles are distributed on the liquid crystal layer is shorter than the above d1 to d3, that is, the gold nanoparticles are distributed at a higher density.

FIG. 11 is a diagram showing an image (reflected image) of the measurement jig 12 and the pressure sensor 5 when pressure is applied. The lower half of FIG. 11 shows an image of the pressure sensor 5 using the reference sample installed in the measurement jig 12 in "no pressure" (without weights 123, 124) and "with pressure" (without weights 123, 124). 124) is shown. Furthermore, for comparison, the upper half of FIG. 11 shows an image of the pressure sensor 5 using a gold nanoparticle-free sample installed in the measurement jig 12.

The pressure P [unit: Pa] applied to the pressure sensor 5 in "with pressure" can be calculated according to the following formula (4).
P=αW/S...(4)

In formula (4), W is the mass of the weight [unit: kg]. S is the area [unit: cm ² ] of the gold nanoparticle-doped liquid crystal (photoresponsive material 53) including the surrounding spacer 54. α is a coefficient for converting mass per unit area [unit: kg/cm ² ] into force per unit area [unit: N/m ² = Pa], and α = 9.8×10 ⁴ It is calculated as follows.

Based on the above formula (4), the pressure P when the weight is 50 g is calculated as P=1396 [Pa]. The pressure P when the weight is 100 g is calculated as P=2792 [Pa]. The pressure P when the weight is 150 g is calculated as P=4188 [Pa]. The pressure P when the weight is 200 g is calculated as P=5584 [Pa].

In the simulated experiment (water cave experiment) described in Embodiment 2, it is required to be able to measure a pressure of about 100 kPa at maximum. If pressure changes can be measured by the pressure sensor 5 within the above range of pressure P, it can be evaluated that at least half of the pressure range required for the simulation experiment can be covered. As will be described later, by changing the composition of the gold nanoparticle-doped liquid crystal, it is possible to cover the entire pressure range required for the simulation experiment. In addition, in the simulation experiment, it is desirable that a pressure difference of about 10 ² Pa can be distinguished (that is, the pressure resolution is 10 ² Pa).

<Pressure measurement flow>
FIG. 12 is a flowchart showing pressure measurement processing in the first embodiment. The flowchart shown in FIG. 12 and FIG. 26, which will be described later, is called from the main routine (not shown) when the measurement start condition is satisfied, for example, when the measurement person operates the controller 18 (for example, presses the measurement start button). and executed. Each step included in these flowcharts is basically realized by software processing by the controller 18, but may also be realized by dedicated hardware (electric circuit) created within the controller 18.

Referring to FIG. 12, in step S21, controller 18 controls light source 11 to start irradiating light to pressure sensor 5 (object 9). This light irradiation is continued until the spectrum measurement is completed. Note that the irradiation light from the light source 11 includes a wavelength obtained by multiplying the refractive index (n _w +Δn _GNP ) of the gold nanoparticle-doped liquid crystal by the helical pitch p of the cholesteric liquid crystal (see equation (2) above).

In step S22, the controller 18 controls the spectrometer 16 to acquire the spectrum (absorbance spectrum or reflection spectrum) of the pressure sensor 5.

In step S23, the controller 18 analyzes the spectrum acquired in step S22 and calculates the pressure represented by the pressure sensor 5. This spectrum analysis will be described later.

In step S24, the controller 18 outputs the pressure calculation result in step S23. For example, the controller 18 can display the pressure distribution on the surface of the object 9 on a monitor (not shown).

In step S25, the controller 18 determines whether the measurement end condition is satisfied. When the user performs a predetermined operation (such as pressing a measurement end button) or when spectra are acquired for a predetermined time or a predetermined number of times, it is determined that the measurement end condition is met. If the measurement end condition is not satisfied (NO in step S25), the controller 18 returns the process to S22. As a result, photographing of the object 9 is continued. When the measurement end condition is met (YES in step S25), the controller 18 stops irradiating the object 9 with light (step S26), and returns the process to the main routine. This completes the series of processing.

<Comparison of absorbance spectrum and reflection spectrum>
FIG. 13 is a diagram showing an example of spectrum measurement results for a gold nanoparticle-free sample. FIG. 14 is a diagram showing an example of spectrum measurement results for a diluted sample. FIG. 15 is a diagram showing an example of spectrum measurement results for the reference sample. FIG. 16 is a diagram showing an example of spectrum measurement results for a concentrated sample. In each of FIGS. 13-16, the absorbance spectrum is shown at the top and the reflection spectrum is shown at the bottom. Three spectral measurements were performed under the same conditions.

Referring to FIGS. 13 to 16, in all samples, the peak wavelength of the absorbance spectrum and the peak wavelength of the reflection spectrum were almost equal. Specifically, the peak wavelength λp of both spectra in the gold nanoparticle-free sample was 614 nm. The peak wavelength λp of both spectra in the diluted sample was 630 nm. The peak wavelength λp of both spectra in the reference sample was 641 nm. The peak wavelength λp of both spectra in the concentrated sample was 620 nm. This shows that either the absorbance spectrum or the reflection spectrum may be measured.

<Peak wavelength vs pressure>
FIG. 17 is a diagram showing measurement results of absorbance spectra when applying various pressures. FIG. 17 and FIG. 18 (described later) show measurement results for a gold nanoparticle-free sample, a diluted sample, a reference sample, and a concentrated sample in order from the top. In FIG. 17, the horizontal axis represents wavelength, and the vertical axis represents absorbance.

It can be seen from FIG. 17 that a significant change occurs in the absorbance spectrum depending on the pressure applied to the pressure sensor 5. The peak wavelength λp was read from these absorbance spectra, and the correlation between the peak wavelength λp and pressure was organized in a separate graph.

FIG. 18 is a diagram showing the relationship between the peak wavelength λp determined from the absorbance spectrum and the pressure. In FIG. 18, the horizontal axis represents the pressure applied to the pressure sensor 5 [unit: kPa], and the vertical axis represents the peak wavelength λp of the absorbance spectrum.

Referring to FIG. 18, when the measurement results shown in FIG. 17 were plotted on the graph, it was possible to linearly approximate the relationship between the pressure and the peak wavelength λp. When the slope of this approximate straight line was compared between samples, the reference sample had the largest absolute value of the slope. From this, it can be seen that among the four samples, the reference sample is the one in which the pressure change is most likely to be reflected in the shift amount of the peak wavelength λp (that is, it has the highest sensitivity). The results of this analysis show that simply increasing the concentration of the gold nanoparticle dispersion does not improve the sensitivity to pressure changes, and that there is an appropriate range (or optimal concentration) for the concentration of the gold nanoparticle dispersion. is suggested.

Next, the results of determining the relationship between the peak wavelength and pressure using the same procedure from the local reflection spectrum of the pressure sensor 5 will be described.

FIG. 19 is a diagram showing measurement results of reflection spectra when applying various pressures. FIG. 20 is a diagram showing the relationship between the peak wavelength λp determined from the reflection spectrum and the pressure. In FIGS. 19 and 20, the measurement results for the gold nanoparticle-free sample are shown at the top, and the measurement results for the reference sample are shown at the bottom.

As shown in FIGS. 19 and 20, it was confirmed that the analysis results of the reflection spectrum were similar to the analysis results of the absorbance spectrum. In other words, even in the reflection spectrum, a linear approximation of the relationship between pressure and peak wavelength λp was possible. Furthermore, the slope (absolute value) of the approximate straight line in the reference sample was larger than the slope of the approximate straight line in the gold nanoparticle-free sample.

In order to measure a wide range of pressure changes (maximum pressure changes of about 100 kPa) as required for the simulation experiment described later in Embodiment 2, it is desirable to intentionally lower the sensitivity to color changes. . In other words, it is desirable to reduce the slope of the approximate straight line. For example, if it is assumed that the peak wavelength shifts from a wavelength of 700 nm to 400 nm, the slope of the approximate straight line may be set to about -3 [nm/kPa]. By appropriately adjusting the composition of the gold nanoparticle-doped liquid crystal (gold nanoparticle particle size, gold nanoparticle doping amount, and/or amount of ultrapure water, etc.), the slope of the approximate straight line can be reduced to the small value shown above. Can be set.

More specifically, by increasing the concentration of gold nanoparticles, it is possible to reduce the average distance between the gold nanoparticles to a single micrometer order or less (nanometer order). The interaction between localized surface plasmons of gold nanoparticles becomes significant when the average interparticle distance is on the order of nanometers. When the average interparticle distance is on the order of nanometers, the peak derived from localized surface plasmon of gold nanoparticles and the peak derived from cholesteric liquid crystal approach each other. Then, the longer wavelength shift of the peak derived from the localized surface plasmon in the gold nanoparticles and the shorter wavelength shift of the peak derived from the cholesteric liquid crystal weaken each other (cancellation), reducing the sensitivity to color change. As a result, it is possible to realize a pressure sensor 5 that can measure pressure changes over a wide range.

On the other hand, the average distance between the gold nanoparticles may be on the order of a single micrometer or more (on the order of micrometers). In this example, gold nanoparticles with a particle size of 30 nm were used, but when the particle size of the gold nanoparticles is larger (for example, several hundred nm), the average interparticle distance can be on the order of micrometers. Even if the average interparticle distance is on the order of micrometers, spectral changes occur in response to pressure changes. In this way, the average interparticle distance of gold nanoparticles may range from the order of nanometers to the order of micrometers.

<Transmission image when pressure is applied>
FIG. 21 is a diagram showing a transmitted image taken by the camera 17 when pressure is applied. FIG. 21 shows transmission images of a gold nanoparticle-free sample, a diluted sample, a reference sample, and a concentrated sample in order from top to bottom. The applied pressure increases from left to right. FIG. 22 is a diagram showing a reflected image taken by the camera 17 when pressure is applied. FIG. 22 depicts, from top to bottom, transmission images of the gold nanoparticle-free sample and the reference sample.

The white circle described in the leftmost image showing the measurement results when the weights 123 and 124 are not used (0 g) represents the photometric region of the spectrum explained in FIGS. 13 to 16 and the like. According to this embodiment, it is possible to measure the pressure in a minute area surrounded by a white circle and having a diameter of about 25 μm. If the magnification of the objective lens 14 is increased to, for example, 100 times, it is also possible to measure pressure in an even smaller area with a diameter of about 10 μm. Note that, in principle, it is also possible to measure pressure in a region as large as the wavelength (1 μm or less), which is the diffraction limit of light.

It can be seen from both FIG. 21 and FIG. 22 that the color changes as the pressure changes (specifically, it changes from light blue to light purple). Note that the black shadows in each image are microbubbles generated in the gold nanoparticle-doped liquid crystal.

As described above, according to the first embodiment, the pressure sensor 5 having a simple configuration using gold nanoparticles can be manufactured more easily. This sensor can also be used as a temperature sensor. In the first embodiment, a spectrum obtained by spectroscopic measurement of the pressure sensor 5 is analyzed. The type of spectrum may be an absorbance spectrum or a reflection spectrum. The pressure applied to the object 9 can be calculated based on the shift of the peak wavelength of the spectrum. Furthermore, by continuously or intermittently acquiring the shift of the peak wavelength, it is also possible to track changes in the pressure applied to the object 9 over time.

[Embodiment 2]
In the first embodiment, a configuration has been described in which the pressure applied to the pressure sensor 5 is measured based on a spectrum change of the pressure sensor 5 obtained by spectroscopy. In the second embodiment, a configuration will be described in which pressure is measured based on a color change in an image obtained by photographing the pressure sensor 5. The configuration of the pressure sensor 5 itself is basically the same as the configuration described in Embodiment 1 (see FIGS. 3 and 4).

<Configuration of pressure measurement system>
FIG. 23 is a diagram schematically showing the overall configuration of a pressure measurement system according to the second embodiment. Referring to FIG. 23, pressure measurement system 2 is an experimental system for measuring the pressure applied to object 9 when a fluid medium acts on the surface of object 9. More specifically, the pressure measurement system 2 measures the pressure distribution on the surface of the object 9 caused by the impact of the fluid medium on the object 9. The object 9 is, for example, a small structure (building model).

Such simulations are commonly referred to as "wind tunnel experiments" when the fluid medium is air. On the other hand, the fluid medium in this embodiment is a liquid such as water or an aqueous solution. Therefore, the pressure measurement system 2 can also be called a "water cave experiment system". However, the fluid medium may also be a gas (such as air).

The pressure measurement system 2 includes a light source 21, a water tank 22, a camera 23, and a controller 24.

The light source 21 emits light to irradiate the object 9. As in the first embodiment, this irradiation light is preferably white light from a halogen lamp or the like, but the type of light source 21 is not particularly limited. The light irradiated onto the object 9 may be, for example, light from a light provided on the ceiling of the laboratory or sunlight. In this way, the light source 21 may be provided outside the pressure measurement system 2, and therefore is not an essential component of the pressure measurement system 2.

The water tank 22 is a circulation type water tank and includes a pump 221 , a first main part 222 , a rectifier 223 , a measuring part 224 , and a second main part 225 . Note that the size of the water tank 22 excluding the pump 221 is approximately 1245 mm in width and 500 mm in depth.

Pump 221 generates a liquid flow by discharging liquid. As shown by the arrow in the figure, the liquid discharged from the pump 221 flows in the order of the first main part 222 - the rectifier part 223 - the measuring part 224 - the second main part 225 and returns to the pump 221 . The pump 221 may operate according to a command from the controller 24 or according to manual operation by a measuring person. By changing the discharge amount from the pump 221, the liquid can be adjusted to flow through the measuring section 224 at a desired flow rate.

The first main part 222 and the second main part 225 are main parts of a flow path through which the liquid circulates. The first main part 222 connects the pump 221 and the rectifier 223. The second main part 225 connects the measuring part 224 and the pump 221. In this example, the cross-sectional shape of the flow path in the first main part 222 and the second main part 225 is a square of 100 mm x 100 mm.

The rectifying section 223 is provided between the first main section 222 and the measuring section 224. The rectifying section 223 rectifies the liquid from the first main section 222 and supplies the rectified liquid to the measuring section 224 . Specifically, the rectifying section 223 includes a honeycomb section 223A and a constricted section 223B. The honeycomb portion 223A has a large number of flow holes (mesh) arranged in a honeycomb shape. The constricted portion 223B is provided downstream of the honeycomb portion 223A, and has a shape whose cross-sectional area decreases in the flow direction of the liquid. As the liquid flows through the honeycomb portion 223A, the flow is rectified and the uniformity of the liquid is improved. Furthermore, when the liquid flows through the constriction, it contracts (contraction occurs), thereby further improving the uniformity of the liquid.

The measuring section 224 is provided between the rectifying section 223 and the second main section 225. The measurement unit 224 is configured such that the object 9 can be placed therein. One or more resistors may be arranged upstream of the measuring section 224. Thereby, a flow having a target turbulent flow structure can be generated, and the flow can be applied to the object 9. In this example, the cross-sectional shape of the measuring section 224 is a square measuring 30 mm x 30 mm. The length of the measuring section 224 is 335 mm.

FIG. 24 is a diagram showing how the pressure measurement system 2 performs measurement. In FIG. 24, illustration of the water tank 22 and the like is omitted to avoid complexity, and the object 9 is shown exposed.

Referring to FIGS. 23 and 24, camera 23 photographs object 9 under light irradiation according to a command from controller 24, and outputs the photographed image to controller 24. The camera 23 is, for example, a video camera that can shoot moving images. By taking a video, it is possible to track changes in the pressure distribution on the surface of the object 9 over time. However, the camera 23 may be a still camera that takes still images. Note that the camera 17 corresponds to a "photodetector" according to the present disclosure.

Note that in this example, since the object 9 is photographed in its actual size, unlike the first embodiment, the objective lens 14 (see FIG. 1) is not provided. However, it is also possible to photograph the object 9 from a distance. In that case, a telephoto lens (not shown) can be provided.

The controller 24 is, for example, a personal computer, and includes a processor 241 such as a CPU, a memory 242 such as a ROM and a RAM, and an input/output port (not shown). Controller 24 controls camera 23. Further, the controller 24 calculates the pressure distribution on the surface of the object 9 by performing predetermined image processing on the image taken by the camera 23. Image processing by the controller 24 will be described later.

FIG. 25 is a diagram showing an example of the target object 9. As shown in FIG. Referring to FIG. 25, object 9 is a structure as described above, and includes an outer wall 91 and a roof 92. A plurality of pressure sensors 5 are arranged on the outer wall 91. A plurality of pressure sensors 5 are similarly arranged on the roof 92.

Although FIG. 24 shows a spacing between adjacent pressure sensors 5, such spacing is optional. A plurality of pressure sensors 5 may be arranged without spacing. Alternatively, a single pressure sensor 5 may be provided so as to cover the entire surface of the outer wall 91 or the roof 92. Further, the shape of the pressure sensor 5 is not limited to a planar shape. For example, when the roof 92 has a curved shape as shown in FIG. 24, the pressure sensor 5 may also have a curved shape that matches the shape of the roof 92.

<Pressure measurement flow>
FIG. 26 is a flowchart showing pressure measurement processing in the second embodiment. Referring to FIG. 26, in step S31, the controller 24 causes the light source 21 to start irradiating the object 9 with light. In addition, when the light source 21 is not controlled by the controller 24 (when the light source 21 is manually operated, when the light source 21 is the sun, etc.), the process of step S21 is skipped.

In step S32, the controller 24 controls the camera 17 to photograph the pressure sensor 5 installed on the surface of the object 9 under light irradiation.

In step S33, the controller 24 performs predetermined image processing on the image photographed in step S22, and calculates the pressure represented by the pressure sensor 5. More specifically, the correspondence between the pressure applied to the pressure sensor 5 and the color expressed by the pressure sensor 5 is stored in advance in the memory 242 of the controller 24 as, for example, a map. By referring to this correspondence, the controller 24 can calculate the pressure applied to the pressure sensor 5 based on the color information (for example, RGB values) extracted from the image of the pressure sensor 5.

The remaining processing from S34 to S36 is the same as the processing from S24 to S26 in the first embodiment (see FIG. 12), so the description thereof will not be repeated.

As described above, in the second embodiment, the pressure is calculated based on the color information of the image taken by the pressure sensor 5. This method is more suitable for tracking pressure over a wider range in real time than the spectrum analysis method described in the first embodiment. For example, by installing a large-area pressure sensor 5 near the top of a high-rise building, the pressure sensor 5 can be used as a wind pressure gauge.

In the second embodiment, an example has been described in which the pressure sensor 5 is used to measure pressure in a situation where liquid (or gas) acts on the object 9. The pressure sensor 5 can also be used to measure pressure distribution on contact surfaces between solid objects. As an example, pressure-sensitive sheets are currently used to evaluate tire grip performance. Once the color of existing pressure-sensitive sheets changes with the application of pressure (load), it remains changed even after the pressure is removed. In other words, with existing pressure-sensitive sheets, traces of pressure accumulate. On the other hand, the pressure sensor 5 according to the present embodiment is reversible, and the color of the pressure sensor 5 can change from time to time depending on the applied pressure. Therefore, by using the pressure sensor 5, more detailed information on changes in pressure over time can be obtained. As another example, in fields such as sports science and robotics, it is also possible to measure changes over time in the pressure acting on the soles of the feet during weight shifts associated with walking.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the claims rather than the description of the embodiments described above, and it is intended that all changes within the meaning and scope equivalent to the claims are included.

1 pressure measurement system, 11 light source, 12 measurement jig, 121, 122 slide glass, 123, 124 weight, 13 stage, 14 objective lens, 15 optical component, 16 spectrometer, 17 camera, 18 controller, 181 processor, 182 memory , 5 pressure sensor, 51 substrate, 52 transparent film, 53 photoresponsive material, 54 spacer, 61-65 liquid crystal layer, 7 gold nanoparticles, 9 object, 91 outer wall, 92 roof, 2 pressure measurement system, 21 light source, 221 pump, 22 water tank, 222 first main part, 223 rectifier, 223A honeycomb part, 223B constriction part, 224 measurement part, 225 second main part, 23 camera, 24 controller, 241 processor, 242 memory.

Claims (13)

A sensor for measuring pressure or temperature,
A photoresponsive material including a liquid crystal having a helical structure and metal nanoparticles;
A sensor comprising: a light-transmitting layer that covers at least a portion of the photo-responsive material and is transparent to light irradiated onto the photo-responsive material. The sensor according to claim 1, wherein the liquid crystal includes at least one of cholesteric liquid crystal, smectic liquid crystal, and TGB (Twisted Grain Boundary) liquid crystal. 3. The sensor according to claim 2, wherein the helical structure of the liquid crystal has a helical pitch obtained by dividing the wavelength of the light irradiated to the photoresponsive material by the refractive index of the photoresponsive material. The wavelength of the light irradiated to the photoresponsive material is included in the visible range,
4. The sensor according to claim 3, wherein the helical pitch of the helical structure of the liquid crystal is on the order of submicrometers. The wavelength of the light irradiated to the photoresponsive material is included in the infrared region,
The sensor according to claim 3, wherein the helical pitch of the helical structure of the liquid crystal is on the order of micrometers. A method of manufacturing a sensor for measuring pressure or temperature, the method comprising:
a step of preparing a metal nanoparticle dispersion liquid in which metal nanoparticles are dispersed by a reduction method;
A method for manufacturing a sensor, comprising the step of preparing a metal nanoparticle-doped liquid crystal by introducing a material capable of producing a liquid crystal having a helical structure into the metal nanoparticle dispersion. 7. The method for manufacturing a sensor according to claim 6, wherein the average interparticle distance of the metal nanoparticles in the metal nanoparticle dispersion is in the range of nanometer order to micrometer order. 8. The method for manufacturing a sensor according to claim 7, wherein the average interparticle distance of the metal nanoparticles in the metal nanoparticle dispersion ranges from a submicrometer order to a single micrometer order. A measurement system that measures the pressure applied to the object or the temperature of the object using a sensor installed on the object,
The sensor has a photoresponsive material including a liquid crystal having a helical structure and metal nanoparticles,
The measurement system includes:
a photodetector that detects the light irradiated to the sensor;
A pressure or temperature measurement system, comprising: a calculation device that calculates the pressure or temperature of the object by subjecting the signal from the photodetector to predetermined signal processing. The photodetector includes a camera that photographs the sensor,
10. The pressure or temperature measurement system according to claim 9, wherein the calculation device calculates the pressure or temperature of the object based on color information of an image photographed by the camera. The photodetector includes a spectrometer that spectrally transmits transmitted light or reflected light from the sensor,
The pressure or temperature measurement system according to claim 9, wherein the calculation device calculates the pressure or temperature of the object based on the peak wavelength of the absorbance spectrum or reflection spectrum acquired by the spectrometer. A measurement method for measuring the pressure applied to the object or the temperature of the object using a sensor installed on the object, the method comprising:
The sensor has a photoresponsive material including a liquid crystal having a helical structure and metal nanoparticles,
The measurement method is
detecting the light irradiated on the sensor with a photodetector;
A method for measuring pressure or temperature, the method comprising: calculating the pressure or temperature of the object by subjecting the signal from the photodetector to predetermined signal processing. 13. The method for measuring pressure or temperature according to claim 12, further comprising the step of irradiating the photoresponsive material with light having a wavelength equal to the refractive index of the photoresponsive material multiplied by the helical pitch of the helical structure of the liquid crystal.

Images