Fluid sensor, flow path, method for manufacturing the same, and method for manufacturing a fluid sensor

Abstract

To provide a device with a simple structure which does not have a movable part for detecting the pressure of a fluid.SOLUTION: A part of a wall of a flow passage is formed of a flexible material and a surface of the wall formed of the flexible material is more rigid than the inside of the wall. Thereby, the wall of the flexible material is deformed by application of a pressure in the flow passage, and periodic wrinkles are generated in a surface part with a high rigidity by the deformation. Development of a structural color from the wrinkles makes it possible to detect the pressure in the flow passage.SELECTED DRAWING: Figure 2B

Description

[Technical Field]

[0001] This invention relates to a fluid sensor that measures the pressure of a fluid flowing through a channel based on the structural color that appears on the channel wall due to the deformation of the channel wall caused by the internal pressure of the channel through which the fluid to be measured flows. This invention also relates to a channel configured to produce a structural color on the channel wall due to the deformation of the channel wall caused by the internal pressure of the fluid flowing through the channel, and a method for manufacturing the same. This invention further relates to a method for manufacturing the above-mentioned fluid sensor using such a channel. [Background technology]

[0002] Measuring gas flow is a central challenge in the field of fluid dynamics. While many methods exist for measuring gas flow, they typically utilize specialized, highly sophisticated equipment. In contrast, far fewer methods exist that enable simple fluid measurements using small, low-cost devices or components. Such devices would greatly expand the applications and uses of fluid flow measurement.

[0003] In cases where various solutions exist, measuring fluid flow often boils down to determining the pressure required to produce a given flow rate. This is achieved using pressure gauges, but this is often cumbersome in terms of both setup and reading. Typical pressure gauges operate by measuring the strain caused by pressure. Thus, the task of pressure measurement boils down to strain measurement. To perform strain measurement, several tactile sensors are available in addition to a wide range of commercially available strain gauges.

[0004] Furthermore, many advanced applications require two-dimensional measurement of pressure, and therefore strain. For this purpose, digital image correlation and related techniques can be used. These techniques allow visualization of how strain is distributed throughout the entire channel. While these techniques are powerful and well-developed, their measurement relies on large and expensive equipment configurations. For example, microchannels made of polydimethylsiloxane (PDMS) combined with stimulus-responsive coloration have been developed for pressure detection. Various means for detecting color changes have been proposed, including photonic crystal lattices, lenses, interference, dyed solutions, and pressure-sensitive pigments. However, fabricating such microchannels requires many steps using special equipment in a clean environment, and strain measurement typically requires much more sophisticated equipment. Also, Patent Document 1 discloses strain measurement using a film of a transparent material in which fine particles are dispersed at regular intervals. Here, the distribution of strain over a large area is detected from the distribution of structural color by utilizing the fact that the spacing of the fine particle dispersion film changes as it expands and contracts due to strain, and the structural color changes accordingly. In the strain measurement described in Patent Document 1, it is necessary to fabricate a fine particle dispersion film suitable for such measurement, but it is not easy to realize such a strain measurement device. Furthermore, in such a structure, structural color appears regardless of the presence or absence of strain, so the change in structural color takes the form of a change in the hue of this constantly present structural color. Depending on the detector or other detection conditions for detecting changes in structural color, it may be desirable for the structural color to appear in a form where no structural color appears when there is no strain, and as the strain increases, not only the wavelength but also the intensity of the structural color changes, or the presence or absence of structural color changes. Therefore, it would be advantageous to provide an element structure for strain measurement that can accommodate such detection conditions. [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of the present invention is to provide a flow channel having a greatly simplified structure and being easy to manufacture, wherein the structural color of the flow channel wall changes depending on the pressure of the fluid flowing through the flow channel, and a method for manufacturing such a flow channel. Another object is to provide a fluid sensor having a simple structure and a method for manufacturing the same by using such a flow channel. [Means for solving the problem]

[0006] According to one aspect of the present invention, a fluid sensor is provided having a flow path surrounded by a wall made of a material that deforms at least a portion of itself due to the internal pressure applied by a given fluid, wherein periodic wrinkles are formed on at least a portion of at least one surface of the wall on the side facing the flow path and on the side opposite to the flow path due to the deformation, and structural color appears on at least a portion of the at least one surface due to the wrinkles. Here, at least one surface of the wall has a surface region that is more rigid than the interior of the wall. The wrinkles may be formed when at least a portion of the rigid region of at least one of the surfaces is compressed by the deformation. Furthermore, a portion of the channel wall may be made of a material with lower rigidity than the remaining portion of the channel wall, and the highly rigid surface region may be located on at least one surface of the channel in the portion of the channel wall that is made of a material with lower rigidity than the remaining portion of the channel wall. Furthermore, the material with low rigidity may be polydimethylsiloxane. Furthermore, the material constituting the remaining portion of the wall of the flow path is a silicon-containing material, and a first adhesive region on the surface of the first member made of polydimethylsiloxane and a second adhesive region on the surface of the second member made of the silicon-containing material, which corresponds to the first portion of the surface of the first member, are bonded together, and the region surrounded by the bonded first and second adhesive regions, but which is not bonded itself, may be used as the flow path. Furthermore, the silicon-containing material may be glass or silicon. Furthermore, the highly rigid surface region may be formed by treating the polydimethylsiloxane surface with argon (Ar) plasma. Furthermore, both the first adhesive region of the first member composed of polydimethylsiloxane and the second adhesive region of the second member composed of the silicon-containing material, or only the first adhesive region, may be subjected to oxygen (O2) plasma treatment. Furthermore, the surface of the first member including the first adhesive region and the surface of the second member including the second adhesive region may be flat surfaces. Furthermore, openings may be provided near one end and near the other end of the flow path, allowing the fluid to flow between the two openings. Furthermore, when the internal pressure from the fluid is not applied to the surface of the wall of the channel, the channel is closed, and when the internal pressure from the fluid is applied, the portion of the wall of the channel made of the deformable material deforms, causing the channel to open. According to another aspect of the present invention, a method for manufacturing a fluid sensor is provided, in which a portion of the surface of a member composed of polydimethylsiloxane is treated with Ar plasma, at least a portion of the remaining portion of the surface of the member is treated with O2 plasma, and the portion of the member treated with O2 plasma is bonded to a silicon-containing substrate, thereby providing a fluid sensor in which the portion treated with Ar plasma serves as a flow channel, and a structural color appears on at least a portion of the surface due to the internal pressure applied by a given fluid. Here, the process of bonding the region of the member treated with the O2 plasma to the silicon-containing substrate may be carried out by bringing the region of the member into contact with the surface of the substrate. Furthermore, the Ar plasma treatment and the O2 plasma treatment may be performed using masks in which the transmission-shielding relationship is reversed. Furthermore, the Ar plasma treatment may be carried out using a mask that allows Ar plasma to pass through the region designated as the flow path, and a fine wire-shaped member may be provided in a portion of the region on the mask through which the Ar plasma should pass, thereby protecting the region of the member located below the fine wire-shaped member from irradiation with the Ar plasma. According to yet another aspect of the present invention, a channel is provided which is surrounded by a wall made of a material that deforms at least in part by an internal pressure applied by a given fluid, wherein periodic wrinkles are formed on at least a portion of at least one surface of the wall on the channel side and the surface opposite to the channel due to the deformation, and structural color is expressed on at least a portion of the at least one surface due to the wrinkles. Here, at least one surface of the wall has a surface region that is more rigid than the interior of the wall, and the wrinkle may be formed by the compression of at least a portion of the rigid region of the at least one surface by the deformation. Furthermore, a portion of the channel wall may be made of a material with lower rigidity than the remaining portion of the channel wall, and the highly rigid surface region may be located on at least one surface of the channel in the portion of the channel wall that is made of a material with lower rigidity than the remaining portion of the channel wall. According to yet another aspect of the present invention, a method for manufacturing a channel is provided in which the region treated with the Ar plasma forms a channel, and structural color appears on at least a portion of the surface when internal pressure is applied, by treating a portion of the surface of a member composed of polydimethylsiloxane with Ar plasma, treating at least a portion of the remaining portion of the surface of the member with O2 plasma, and bonding the region of the member treated with the O2 plasma to a silicon-containing substrate. [Effects of the Invention]

[0007] According to the present invention, a flow channel is provided in which, despite its simplified structure, its wall surface responds sensitively to the fluid pressure within the flow channel and exhibits structural color, making it suitable for application in fluid sensors and the like. Furthermore, since the wavelength-order microstructure that exhibits this structural color is a microstructure spontaneously formed by periodic wrinkles on the flow channel wall surface caused by the deformation of the flow channel wall due to the application of pressure to the flow channel, in other words, by deformation, such a microstructure itself does not need to be actively created during the manufacturing process, and can therefore be easily manufactured. [Brief explanation of the drawing]

[0008] [Figure 1] The following are photographs of a device according to one embodiment of the present invention: (a) a photograph of the entire device when no gas flow is being passed through it, and (b) a photograph of the device while a nitrogen gas flow is being passed through it at a flow rate of 10 mL / min; magnified photographs of the Ar plasma-treated and untreated regions within the Ar plasma-treated / untreated boundary area near a small circle drawn near the center of the overall device photograph; and further, high-magnification photographs of the square-shaped regions within the Ar plasma-treated and untreated regions in the magnified photographs. [Figure 2A] A schematic diagram showing the manufacturing process of a PDMS device according to one embodiment of the present invention. Both a top view and a side view are shown for each step. [Figure 2B]These are photographs of a device according to one embodiment of the present invention, taken with nitrogen (N2) flow rates of 0 mL / min, 5 mL / min, 10 mL / min, 20 mL / min, 50 mL / min, 100 mL / min, 200 mL / min, 300 mL / min, and 400 mL / min, respectively. The intensity profiles for red (R), green (G), and blue (B) (R, G, and B are shown in dark gray, gray, and light gray, respectively) are also shown to the right of the corresponding photographs. The intensity profile graphs further show the average intensity of R, G, and B (i.e., the intensity of light before trichromatic separation) with a black-bordered line. These profiles show the intensity of each color as it appears on the cutting line obtained by cutting the photograph of the device along the horizontally extending white dashed line shown in the photograph with a flow rate of 0 mL / min. [Figure 2C] This is the finite element simulation result of a device according to one embodiment of the present invention, showing the stress induced in the y-direction (direction perpendicular to the flow) on the inner wall of the PDMS slab by nitrogen gas flow rates of 50 mL / min, 100 mL / min, and 400 mL / min from top to bottom, respectively. Here, the shape targeted for simulation is the same as the shape of the device in Figure 2B, but here, to facilitate the simulation, a gap (height 50 μm) between the upper PDMS and the bottom glass was assumed. [Figure 2D] A laser microscope image of wrinkles formed under a 10 mL / min N2 flow in a device according to one embodiment of the present invention. This image was recorded at the center of the flow path. [Figure 2E] This graph plots the average intensity along the channel for each of the following colors (R, G, B, and unseparated light, labeled "Gray" in the figure; the same applies to other figures) as a function of flow rate. These values ​​are obtained by averaging the intensities shown in Figure 2B. [Figure 3A] A schematic diagram of a mask used to manufacture a second device, which is a modified version of a PDMS device that is one embodiment of the present invention. [Figure 3B]Photographs taken when N₂ is flowed to the second device at flow rates of 0 mL / min, 5 mL / min, 10 mL / min, 20 mL / min, 50 mL / min, 100 mL / min, 200 mL / min, 300 mL / min and 400 mL / min, respectively. Furthermore, intensity profiles for R, G and B are shown respectively to the right of the corresponding photographs. These profiles indicate the intensity of each of these colors appearing on a cutting line obtained by cutting the captured photograph of the second device along the laterally extending white dashed line shown in the photograph when the flow rate is 0 mL / min. [Figure 3C] A graph plotting the average intensity along the flow path as a function of flow rate for each of R, G, B, and a value obtained by averaging these three colors (denoted as Gray in the figure). These values are obtained by averaging the intensity shown in FIG. 3B over position. [Figure 3D] A laser microscope image of wrinkles formed in the second device under a 10 mL / min N₂ flow. This image was captured at the central portion of the flow path, in the region indicated by a gray square near the center of the photograph when the flow rate is 0 mL / min. [Figure 3E] A graph plotting the displacement of PDMS in the second device as a function of flow rate. This displacement was recorded at the central portion of the flow path, in the region indicated by a gray square near the center of the photograph when the flow rate is 0 mL / min. [Figure 3F] A graph of repeated measurement results showing the stability of the sensitivity of the second device, which represents the normalized intensity of unseparated trichromatic light (gray) measured at 500 mL / min as a function of the number of measurements. [Figure 4] Photographs of a device according to an embodiment of the present invention, captured under various illumination conditions, wherein N₂ gas was flowed at 400 mL / min. [Figure 5A] A perspective view of a three-dimensionally printed mold used for evaluating wrinkles on a curved surface formed under compression. [Figure 5B] A conceptual cross-sectional view showing how a PDMS slab is adhered to the mold when evaluating wrinkles on a curved surface formed under compression. [Figure 5C]Images of PDMS taken under conditions of strains of 0.8%, 1.3%, and 2.5% using molds with various radii of curvature to evaluate wrinkles on a curved surface formed under compression. Furthermore, strain magnitude profiles recorded along the longitudinally extending dashed lines drawn in each image are shown to the right of each image. The data for the three images and corresponding strain magnitude profiles shown on the left, and the data for the three images and corresponding strain magnitude profiles shown on the right, were obtained from two PDMS slabs plasma-treated using different masks. Here, the left image uses a mask without lines, and the right image uses a mask with lines. [Figure 5D] This graph plots the wavelength (upper) and amplitude profile (lower) of wrinkles formed on a curved surface under compression as a function of strain. These values ​​were obtained from the strain magnitude profile shown in Figure 5C. The dotted curves are plotted according to the analytical models shown in equations (1) and (2). [Figure 5E] A graph showing the stress-strain relationship in PDMS. All error bars represent standard deviation. [Figure 6A] This figure shows a cross-sectional model of a PDMS slab used in a finite element method simulation to analyze the relationship between strain and displacement. The upper part shows the three-dimensional Cartesian coordinate system of the model, and the lower part shows the configuration of the model and the constraints on its movement due to its fixation to the substrate. As shown in the lower cross-sectional view, a uniformly distributed force is applied to the free surface of the PDMS (the surface between the parts fixed to the substrate at both ends). [Figure 6B] This graph plots the relationship between strain and displacement as a function of applied force, using the finite element method for finite element analysis. Additionally, eight solid circles are plotted representing points based on experimentally obtained displacements, as shown in Figure 3E. [Figure 6C]This graph plots the strain obtained from a simulation using the finite element method for finite element analysis as a function of the displacement obtained from the simulation, represented as small white circles. The points based on the experimentally obtained displacements shown in Figure 3E are also plotted as eight solid small circles. [Figure 6D] This figure shows the relationship between strain and displacement, mapped onto the cross-sectional shape of a PDMS (Plastic Design Mass Spectrometer) using shading, based on simulations conducted using the finite element method. The results shown, from top to bottom, represent the displacements obtained from simulations under N2 flow rates of 5 mL / min, 10 mL / min, 20 mL / min, 50 mL / min, 100 mL / min, 200 mL / min, 300 mL / min, and 400 mL / min, respectively. [Figure 6E] This figure shows the stress tensor obtained from a simulation using the finite element method to analyze the relationship between strain and displacement, mapped onto the cross-sectional shape of the PDMS using varying shades of gray. The results shown, from top to bottom, represent the stress tensor obtained from the simulation under N2 flow rates of 5 mL / min, 10 mL / min, 20 mL / min, 50 mL / min, 100 mL / min, 200 mL / min, 300 mL / min, and 400 mL / min, respectively. [Figure 6F] This graph shows the profile of the bottom surface of the PDMS obtained from a simulation based on the finite element method used for finite element analysis, examining the relationship between strain and displacement. The horizontal axis of the graph represents the distance from the fixed end of the PDMS, and the vertical axis represents the displacement. The eight curves shown in the graph correspond to the eight different N2 flow rates in Figures 6D and 6E. [Figure 6G] This figure shows the strain (solid line) and stress tensor (dashed line) profiles along the bottom surface of the PDMS, obtained from a simulation based on the finite element method used for finite element analysis of the relationship between strain and displacement. [Figure 6H]This graph plots the strain, obtained from the simulation based on the finite element method described above, as a function of the stress tensor, represented by small, open circles. Additionally, eight solid circles are plotted based on the stress values ​​obtained in the simulation in Figure 6C. These stress values ​​correspond to the experimentally obtained displacements shown in Figure 3E. [Figure 7] Microscopic images for comparison of wrinkles formed in two different ways. The left image shows wrinkles formed by flowing N2 at 10 mL / min, while the right image shows wrinkles formed by compression using a curved mold. [Figure 8] Images of PDMS slabs taken using molds with various curvatures under strain rates of 0.8%, 1.3%, and 2.5%. For each image, three amplitude profiles recorded along three dashed lines extending vertically in the image are shown to the right of the corresponding image. Of the six images and corresponding amplitude profiles, the three on the left were obtained from PDMS slabs treated with Ar plasma using a mask without lines (shown at the top left of the figure), and the three on the right were obtained from PDMS treated with Ar plasma using a mask with lines (shown at the top right of the figure). [Figure 9] This graph compares wavelength (upper side) and amplitude (lower side) as functions of strain. Of the four graphs shown, the two on the left are from PDMS slabs treated with plasma using a mask without lines (shown in the upper left of the figure), while the two on the right are from PDMS treated with Ar plasma using a mask with lines (shown in the upper right of the figure). The bar graphs in this figure were created using the three amplitude profiles corresponding to each image in Figure 8. For each graph, three bars (left, center, and right) are drawn for the same strain, and these were created using the data from the three corresponding amplitude profiles located on the left, center, and right of Figure 8, respectively. [Figure 10A]Photographs of a device according to another embodiment of the present invention, fabricated using a modified mask, under a flow rate of 400 mL / min of different gases: He, Ne, N2, Ar, CO2, and Xe. The top photograph shows the device with no gas flowing (i.e., a flow rate of 0 mL / min). Furthermore, intensity profiles for R, G, B, and undecoupled light (shown in dark gray, gray, light gray, and light gray bordered in black, respectively) are shown to the right of each photograph. These intensity profiles are the result of measuring intensity on the corresponding photograph along the horizontal white dashed line shown only in the photograph for 0 mL / min. [Figure 10B] (b) Graphs plotting the average intensity along the channel for R, G, B and undegraded light (shown by squares, circles, upward-pointing triangles and downward-pointing triangles bordered in black, respectively) as a function of the density (left) and viscosity (right) of the various gases shown in Table 1, based on the results of measuring various gases using a device of another embodiment of the present invention fabricated using a modified mask. [Figure 10C] A graph plotting displacement as a function of density (left) and viscosity (right) in the results of measuring various gases using a device of another embodiment of the present invention fabricated using a modified mask. [Figure 10D] A graph plotting the pressure drop as a function of density (left) and viscosity (right) in measurements of various gases using a device of another embodiment of the present invention, fabricated using a modified mask. The squares and circles represent experimental data and calculated values, respectively. [Figure 10E] A graph plotting displacement as a function of pressure drop, showing the results of measuring various gases using a device of another embodiment of the present invention, fabricated using a modified mask. The dashed line indicates the result of linear fitting. [Figure 11] In the results of measuring various gases using a device of another embodiment of the present invention fabricated with a modified mask, the graph on the left plots the average intensity along the flow path for the gray area, the graph in the center plots the pressure drop, and the graph on the right plots the displacement as a function of density. [Figure 12] A photograph taken from the side of a PDMS device according to one embodiment of the present invention while an N2 gas flow is being passed through it at 400 mL / min. [Figure 13] This graph plots the pressure drop measured and calculated under the same conditions as in Figure 10D, as a function of density. The squares and circles (hollow and solid) represent experimental data and calculated values, respectively. However, the calculated values ​​shown in the hollow and solid circles were calculated using Bernoulli's equation with and without the viscosity loss term, respectively. [Figure 14A] This figure shows the applicant's logo mark used as an example of a graphic displayed in an embodiment of a device that displays graphics based on flow in the present invention. [Figure 14B] This diagram conceptually shows the structure of a device for displaying the logo mark shown in Figure 14A (excluding the graphic portion, specifically the text "NIMS"). The dark-colored area, which has the same shape as the logo mark, is the region that has been treated with Ar plasma. [Figure 14C] Figure 14B shows a photograph of the device of the conceptual example being flowed with N2 gas at a rate of 10 mL / min. [Figure 15] A conceptual diagram illustrating an example of a device structure that can use liquid as the fluid to be measured. [Figure 16] Figure 15 shows the results of a simulation based on the finite element method, which calculated the stress tensor on the top surface of a device conceptually representing its structure. These results are then mapped onto (a) an oblique view and (b) a top view of the device using varying shades of gray. [Figure 17] Figure 15 shows a device conceptually illustrating its structure. The structural colors that appear when N2 gas is flowed through it at a flow rate of 100 mL / min ((a)) and when liquid water is flowed through it at a flow rate of 1 mL / min ((b)) are photographs taken from above the device. [Modes for carrying out the invention]

[0009] According to one embodiment of the present invention, fluid flow is measured by visualizing the flow using structural color that appears on the channel wall due to strain caused by the flow of a fluid such as gas in the channel. A device for performing such measurement is realized, for example, by treating a plate-shaped member made of PDMS (hereinafter referred to as a PDMS slab) with two types of plasma, namely argon (Ar) plasma and oxygen (O2) plasma. Here, O2 plasma is typically used to induce covalent bonding between PDMS and a substrate such as glass when bonding a cover (hereinafter also referred to as a substrate) to the device. That is, O2 plasma treatment generates radicals and reactive side chains on the surface of the PDMS, and adhesion is achieved by forming stable bonds such as covalent bonds with the substrate surface such as glass. The formation of such bonds proceeds simply by pressing the PDMS and the substrate against each other, without the use of chemicals to promote the reaction. If the substrate surface is also treated with O2 plasma, a large number of radicals and reactive side chains are generated on its surface, which makes the adhesion between the PDMS and the substrate surface even stronger and more reliable, and is preferable in that delamination is less likely to occur during storage or use.

[0010] To explain the procedure for bonding the PDMS to the substrate, a simple operation such as stacking the PDMS slab and the substrate and applying pressure after O2 plasma treatment is sufficient. In the devices fabricated in the following examples, the PDMS and substrate were stacked and pressed together by hand for about 10 seconds. Maintaining a raised temperature during or after the pressing operation can further strengthen and ensure adhesion. In the examples, after the pressing operation, the substrate was heated in an oven set to 65°C for several minutes.

[0011] In this example, glass (specifically a soda-lime glass substrate in the following examples) was used as the substrate material to be bonded to the PDMS, but the usable materials are not limited to this. Any material that can be bonded to the O2 plasma-treated PDMS by forming the aforementioned bond is acceptable. Various processing conditions, such as whether or not O2 plasma treatment is required on the substrate surface and the processing time, can be appropriately determined to obtain sufficient adhesive strength and reliability for the operating conditions of the device to be manufactured. This is also influenced by what material is used for the substrate surface. For example, silicon may be used instead of glass as the substrate material, but in that case, in order to achieve adhesion equivalent to that with glass, it is necessary to perform stronger O2 plasma treatment on the PDMS surface or on both the PDMS surface and the substrate surface compared to when using glass as the substrate.

[0012] In contrast, Ar plasma hardly induces covalent bonding, but instead modifies the PDMS surface, forming a more rigid, glassy coating on it. The elastic step between this highly rigid layer and the highly flexible substrate (a layer that lies beneath (inside) the highly rigid layer on the PDMS slab surface and can be called the PDMS substrate in the sense that the highly rigid layer rests on it) causes a well-ordered wrinkle structure to appear on the surface when the PDMS slab is deformed. Since the repetition wavelength of these wrinkles (hereinafter simply referred to as wavelength) is in the range of a few micrometers, an angle-dependent structural color can be observed on the deformed PDMS slab.

[0013] To fabricate a device for measuring flow, a PDMS slab is locally treated with Ar plasma using a mask, and then the remaining portion of the PDMS slab is treated with O2 plasma using a mask that is the inverse of the first mask in the sense that the transmission-shielding relationship is reversed. As a result, the surface of the PDMS slab can be covalently bonded to a substrate such as glass, except for the Ar plasma-treated portion. The Ar plasma-treated region remains chemically unbonded. This structure allows fluids such as gases to flow only between the untreated region and the substrate such as glass. When the surface of the PDMS slab is bonded to a substrate in the manner described above, depending on the force applied during bonding, the warping of the substrate and the PDMS slab, and the size of the surface irregularities, there may be little to no voids between the unbonded regions because no chemical bonding has occurred, resulting in a closed flow path. In this configuration, which lacks a channel that forms a channel with a cross-sectional area greater than zero, even when no fluid is flowing, the deformation of the PDMS due to fluid flow is maximized. This deformation can be measured by visualizing the structural color of the wrinkle pattern caused by the deformation.

[0014] Figure 1 shows photographs of the entire device with and without fluid flowing through it, magnified images of the upper surface of the inner wall (PDMS slab surface) of the device, and further magnified images of a portion of the magnified image. The magnified images of the plasma-treated region of the inner wall clearly show that wrinkles, which are not present when no fluid is flowing, appear when fluid is flowing (i.e., while a flow path is formed by deformation due to pressure). In contrast, in the non-plasma-treated region of the inner wall, only a few relatively irregular wrinkles appear even when fluid is flowing. Furthermore, photographs of the device taken from above show that areas treated with Ar plasma and exhibiting clear wrinkles exhibit distinct coloration, while areas not treated with Ar plasma and exhibiting only slight wrinkles show almost no coloration. This provides a simple and compact means of measuring the pressure of a flowing fluid such as gas. This demonstrates that the flow of a fluid such as gas can be measured by quantitatively measuring the change in color using such a PDMS device. In addition, it is shown that this color depends on the density and viscosity of the fluid. They also revealed that this technology can be used to display specific patterns, such as logos.

[0015] Alternatively, the fluid being measured does not necessarily have to be flowing; it is also possible to measure pressure changes in a stationary fluid. In principle, the structure of such a fluid pressure sensor should have a surface that is dynamic in the sense that wrinkles are generated and disappear, or the height of the wrinkles changes, by deforming due to the pressure of the fluid being measured or any other arbitrary force. To give a more specific example, it may have the same structure as the sensor for flowing fluids described above, or a part of the wall surface of the container containing the fluid being measured may have such a dynamic wrinkle structure. Alternatively, dynamic wrinkles may be formed on the wall of the sensor chamber, which is at the same pressure as such a container or a space that is considerably larger than a normal container, by communicating with such a container or a space that is open in the sense of being in contact with that space.

[0016] The basic principle in manufacturing the above-mentioned devices is to form channels between the PDMS and the substrate on which the PDMS is mounted by treating the PDMS with gas plasma. The entire surface of the PDMS microfluidic device is exposed to O2 plasma, as is common practice in this art. This increases the reactivity of the interface between the PDMS and the substrate, such as glass, improving adhesion to the glass substrate. This method is widely used to improve the airtightness of microfluidic devices (Non-Patent Document 1). Another result of O2 plasma treatment is the formation of a thin, rigid layer on the surface of the PDMS (Non-Patent Documents 2, 3, 4, and 5). The rigidity of this layer is significantly higher than that of the PDMS (Non-Patent Document 6). Even if the surface of the PDMS is treated with Ar plasma, a very rigid and thin layer is formed on the surface (Non-Patent Documents 7 and 8), but no adhesive surface is formed as a result. Therefore, the Ar plasma-treated surface can be easily peeled off from the substrate, such as glass, and does not adhere to the substrate in the same manner as the O2 plasma-treated surface. This invention utilizes this property to form a pattern on the PDMS surface using adhesive regions that bond to a substrate such as glass, and regions that do not bond to glass or other substrates but have significantly higher rigidity than the bulk PDMS.

[0017] The presence of a thin, highly rigid PDMS layer over a region of significantly lower rigidity also yields other beneficial characteristics. These characteristics can be observed when the PDMS is compressed. Because the thin, highly rigid layer resists compression far more strongly than the bulk PDMS, it undergoes a buckling transition, which creates nearly periodic wrinkles on its surface (Non-Patent Literature 9). These wrinkles have an interval of approximately 1 μm, which corresponds to the wavelength of light. As a result, this wrinkle structure forms a diffraction grating structure, resulting in diffraction of light of a specific wavelength that can be easily detected. Furthermore, both the interval and amplitude of these wrinkles (i.e., the depth and / or height of the wrinkles) are highly sensitive to the compressibility of the PDMS, in other words, the strain applied to the PDMS. This provides a simple but highly sensitive means of measuring strain on the PDMS. If this strain is caused by the flow of a fluid such as gas, this becomes a highly sensitive means of detecting that flow.

[0018] To elaborate on the compression described above, if the channel wall deforms due to the internal pressure from the fluid within the channel, the curvature of at least a portion of the channel wall will change. More specifically, the rigid glass portion of the channel wall hardly deforms, but the PDMS side, which is less rigid than the glass, does deform. Generally, when a thin plate-like member is bent, the outer part of the curve tends to stretch, and tension is applied to the surface of this part of the member, while the inner surface tends to be compressed. Therefore, in the channel described above, compressive stress is applied to the inner surface, forming the approximately periodic wrinkles mentioned above. The diffraction of light of specific wavelengths caused by these periodic wrinkles gives rise to structural color.

[0019] To achieve wrinkle formation and the resulting color change caused by compression under flow, as shown in Figure 2A, multiple regions with different adhesions can be created in the PDMS by localized treatment with O2 plasma and Ar plasma using positive and negative masks. The Ar plasma-treated portion can be peeled off even after the entire PDMS has been bonded to a substrate such as glass. By injecting a fluid such as gas, the Ar plasma-treated PDMS is deformed, creating a temporary gap between the Ar plasma-treated region and the substrate such as glass. Importantly, such a structure maximizes the deformation of the PDMS due to the flow of fluid such as gas when no flow channels are formed in advance. To realize this idea, as shown on the far left of Figure 2A, the central part of the PDMS slab (e.g., 2.5 mm thick) is exposed to Ar plasma via a positive mask (the dark gray area covering everything except the central part in the top view on the far left of Figure 2A), with the central part shown in dark gray. After Ar plasma treatment, as shown second from the left in Figure 2A, the PDMS slab is stretched (for example, by applying a strain of approximately 20% for several seconds) to intentionally create controlled cracks in the thin, rigid layer formed by the Ar plasma treatment on the PDMS surface. This process is useful for creating a reproducible structure because the stretching process prevents the formation of uncontrolled cracks due to unexpected bending or stretching at some point in the manufacturing process. Similar to O2 plasma-treated PDMS, Ar plasma-treated PDMS exhibits vivid angle-dependent coloration when stretched. Next, as shown third from the left in Figure 2A, the remaining surface of the PDMS slab is exposed to O2 plasma with the Ar plasma-treated area covered using a negative mask. The device manufacturing is then completed by bonding the PDMS slab to a substrate such as glass.

[0020] To test the functionality of this device, nitrogen (N2) gas was injected into the device at a flow rate of 400 mL / min. As expected, structural coloration was observed in the Ar plasma-treated region, as shown in Figure 2B. Simulations using finite element analysis (FEA) revealed that the region where this structural coloration appeared overlapped with the region where the inner wall of the PDMS slab was compressed due to the pressure of the gas flow, as shown in Figure 2C. This caused wrinkle formation, suggesting that compression was the cause of the appearance of structural coloration. This is further supported by the fact that the structural coloration profile changes symmetrically with respect to the direction perpendicular to the flow, and it matches very well with the compression profile obtained by FEA. The presence of wrinkles was confirmed by microscopic observation of the device in the presence of flow. As shown in Figure 2D, these wrinkles are oriented in line with the direction of flow, and the wavelength of the wrinkles (repetition period between wrinkles) is estimated to be approximately 2-3 μm. Several oblique cracks were also observed, which are thought to have been formed as a result of deformation along two directions: the direction of flow and the direction perpendicular to the flow. While the formation of such cracks is unavoidable, the number of cracks does not change significantly once they have formed. Therefore, measurements and analyses can be performed reproducibly even in the presence of such diagonal cracks. To investigate how the gas flow relates to structural color, the color change was observed by varying the flow rate from 5 mL / min to 400 mL / min. The color was observable even at a low flow rate of 5 mL / min, but it became brighter as the flow rate increased. For further quantitative analysis, the intensity values ​​of red (R), green (G), and blue (B) were extracted from the observed images for each flow rate, and graphs plotting these values ​​were placed to the right of the corresponding device photographs showing structural color for each flow rate in Figure 2B. In addition, the average intensity of R, G, and B (the intensity of the entire visible region before decomposition into these three colors) was also plotted in the graph. As shown in Figure 2E, the average intensity along the flow path for each of R, G, and B (the average intensity across the entire flow path shown in the device photograph in Figure 2B) clearly increased as the flow rate increased.These results indicate that the greater the flow rate, the greater the deformation of the PDMS slab, which in turn increases the amplitude of wrinkles, i.e., the magnitude of their undulations, and thus the greater the color change. This observation is confirmed by the FEA simulation shown in Figure 2C.

[0021] Introducing defects can improve the regularity of wrinkles and the sensitivity of the device. Here, "defect" means that the rigidity of the region on the inner wall surface of the channel where periodic wrinkles are formed is not uniformly increased, but rather, generally speaking, the rigidity of a part of that region differs from the surrounding area. In the embodiment referred to below, this part of the region has a thin wire shape. The rigidity of such a part of the region may be substantially the same as the rigidity of the bulk portion of the inner wall of the channel below it (i.e., the rigidity before the rigidity-enhancing treatment), or, depending on the method of Ar plasma irradiation and the size and structure of the mask used, it may be the rigidity between the rigidity of the bulk portion and the rigidity of the surrounding area. Therefore, this "defect" can also be called a "discontinuity of rigidity."

[0022] The function of this defect can be understood as follows: If the rigidity of the region where wrinkles are formed is uniform, then if irregularity appears in the wrinkles somewhere, that irregularity (non-periodicity) may propagate over long distances. To prevent or mitigate such propagation, a defect in the uniformity of rigidity is introduced within the region. More specifically, for example, if irregularity appears in wrinkles formed nearby due to the presence of unintended structural / rigidity irregularity within the region where wrinkles are formed, low-rigidity "firewalls," i.e., thin, linear low-rigidity regions, are formed at various points within the region to prevent it from propagating over long distances. Even if irregular wrinkles (i.e., their minute deformations) propagate up to these low-rigidity "firewalls," they can be absorbed, preventing the propagation of irregularity beyond that point. Conversely, by providing "firewalls" with higher rigidity than the surrounding area, the "firewall" will not respond to minute deformations caused by wrinkles formed on one side of the thin, linear "firewall," thereby blocking the propagation of irregularity between adjacent regions. Furthermore, since wrinkle formation does not occur within the fine, linear defect regions described above, the area where wrinkle formation occurs decreases when considering the entire region under the assumption of constant strain. This may also contribute to the effect of the defect.

[0023] To introduce such defects, the positive mask used during device manufacturing can be replaced with a modified mask. This modified mask has, for example, three fine lines approximately 0.6 mm wide, spaced at equal intervals and aligned with the flow direction, as shown in Figure 3A. The area beneath these fine lines is considered to be protected from Ar plasma exposure, which can be confirmed by observing the boundary between the plasma-treated and un-plasma-treated areas, as shown in Figure 1. This acts as a defect that causes more regularly spaced wrinkles to form in the protected area, resulting in a more pronounced structural color. In devices using this modified mask (hereinafter also referred to as the second device, and devices manufactured using the non-modified mask also referred to as the first device), it was confirmed that a stronger structural color appeared compared to the first device without the modified mask, as shown in Figures 2B and 2E, as shown in Figures 3B and 3C. Furthermore, as can be seen by comparing Figure 3D with Figure 2D, the second device forms wrinkles with even greater density and regularity. Despite improvements and enhancements in regularity and structural color, the second device exhibits the same trend as the first device. This trend is that the structural color becomes even brighter as the flow rate increases. This trend was confirmed by measuring the flow rate over a wide range from a few mL / min to several hundred mL / min, as shown in Figure 3B. The flow rate dependence of this color change correlates with the displacement of the PDMS, as shown in Figure 3E.

[0024] Here, the above displacement can be estimated by first capturing an image in the absence of flow, and then measuring how much the height needs to be adjusted to obtain a focused image under several flow rates. Although this displacement is a monotonic but nonlinearly increasing function with respect to flow rate, the sensitivity of this measurement can be calculated to be roughly 1 μm per unit flow rate by assuming its linearity and using the displacement measured at 400 mL / min. This is a universal form of sensitivity that describes the device according to the present invention. In addition to optical detection using a CCD based on structural color, other analytical methods can be employed to improve its performance. At low magnification, vivid colors and their gradations can be observed by changing the illumination conditions, as shown in Figure 4. In contrast, a device fabricated without using such lines exhibits a somewhat muted color profile, as shown in Figure 2B. These results confirm that the introduction of the lines described above helps to make the wrinkles denser in a limited area, enhancing structural color and enabling high-sensitivity measurements.

[0025] In addition to sensitivity, the device according to the present invention also exhibits good other important characteristics such as stability and measurement error. To measure these characteristics, the same device was used to intermittently interrupt the N2 flow at 10-second intervals at least 50 times. That is, a cycle of flowing N2 gas for 10 seconds followed by stopping the N2 gas supply for 10 seconds was repeated 50 times, and measurement data was collected every 10 cycles during this measurement. As shown in Figure 3F, no significant change was observed in the normalized intensity even after repeating such cycles numerous times. For these measurements, the flow rate was set to 500 mL / min, which is higher than the flow rates used in the other experiments described above. The measurement error here was estimated to be as low as 1%, indicating sufficient stability and reliability as a device for repeated use.

[0026] To further explain the formation of wrinkles in the device of the present invention, a PDMS mold having a curved surface, as shown in Figures 5A and 5B, was fabricated. The curved shape of this PDMS mold is designed to simulate the upper wall of a microchannel that is deformed by the pressure caused by the flow through the channel. For details on the deformation of the channel wall when fluid flows through a microchannel, please refer to Non-Patent Literature 10, which provides an analysis of this deformation. The curved cross section of this mold should be effective in reproducing the wrinkles formed in the device of the present invention by gas flow, and therefore in estimating how much bending strain is generated. For this purpose, an FEA simulation was performed, assuming that the displacement caused by the flow can be approximately reproduced by applying a uniform load to one side of a PDMS slab fixed at both ends, as shown in Figure 6A. The results of this simulation are shown in Figures 6B to 6H. Based on the simulation results, the bending strain of the PDMS was estimated to be in the range of approximately 1% to 4%. This resulted in the creation of three molds with different curvatures that produced equivalent bending strains of 0.5%, 1.3%, and 2.5%, respectively. When Ar plasma-treated PDMS was mounted on these curved molds, wrinkle formation was observed at a low bending strain of 0.8%. The wavelengths of these wrinkles were the same as those observed when an N2 flow of 10 mL / min was applied (approximately 0.8% strain), as shown in Figures 5C and 7. The wavelength remained almost constant at approximately 2.8 μm, decreasing slightly as the strain increased, while the amplitude increased monotonically as a function of bending strain, as shown in Figure 5D. As shown in Figures 8 and 9, the wrinkles appeared in multiple locations (3 locations) and coincided with each other. The wavelength λ and amplitude A of the strain formed on the curved surface are calculated as follows.

[0027]

number

[0028] Here, λ0 is defined as follows:

[0029]

number

[0030] Also, ε is strain, E f and E s ν is the Young's modulus of the uppermost thin film formed by Ar plasma treatment on the PDMS slab surface and the PDMS bulk portion beneath the thin film, respectively, ν is the Poisson's ratio of PDMS, and t f Here, E f = 0.4 GPa and t f It was assumed that ν = 23 nm. These values ​​were determined for O2 plasma-treated PDMS under similar plasma power, pressure, and time. The reason for adopting the above method of determining the values ​​is that although detailed results of the above values ​​for Ar plasma-treated PDMS were not available, it is expected that these values ​​will not differ significantly under similar treatment conditions even if O2 plasma treatment is performed. For ν, the typical value of 0.499 was used. Also, as shown in Figure 5E, the value of Es was experimentally determined to be 0.13 MPa. The analytical solution was in good agreement with the experimental results obtained for plasma-treated PDMS using a mask without nanowires. In general, the amplitude increases as the strain increases, but the wavelength of the wrinkles remains almost constant at approximately 1.9 μm regardless of the strain, as shown in Figure 5D. The difference between the wavelengths of 2.8 μm and 1.9 μm shown in Figure 9 is the value observed in the presence of flow using the two devices.

[0031] The color change is also affected by other factors, such as the density and viscosity of the gas at 20°C. To evaluate the influence of such factors on the measurement results, the color change was measured when six inert gases—helium (He), neon (Ne), nitrogen (N2), argon (Ar), carbon dioxide (CO2), and xenon (Xe)—were flowed at a fixed flow rate of 400 mL / min in a device fabricated using three parallel lines. The densities and viscosities of these six gases are shown in Table 1. The differences in color intensity and pattern among these six gases are not very noticeable, but there are recognizable differences, particularly between He and Xe shown in Figure 10A. To quantify these results, the average of the respective RGB intensities along the flow path was calculated for each result. Although these average data are small, they nevertheless show a recognizable dependence on both viscosity and density, as shown in Figure 10B. To further quantify the response of this device, the displacement of the PDMS in the middle of the flow path was measured for each of the six gases. The dependence of displacement was similar to that of intensity, but showed more pronounced changes than those for density and viscosity, as shown in Figure 10C. Interestingly, the pressure drop Δp, the difference in pressure measured between the gas inlet and outlet, also showed a similar trend, including discontinuous changes, as shown in Figure 10D. Importantly, the averaged color intensity on RGB (Figure 10B) showed almost the same trend as both concentration and viscosity, including subtle differences between gases, but the total variation was considerably smaller. A detailed comparison is shown in Figure 11. The reduced variation is thought to be due to the strong nonlinear response of this device, and as can be clearly seen from Figures 3C and 3E, intensity and displacement level off at high flow rates. All of these measurements were performed at high flow rates, within the range where the measured values ​​were sufficiently saturated, but the changes decreased.

[0032] [Table 1]

[0033] To explain that the pressure drop depends on the properties of the gas, we use the modified Bernoulli equation for steady, heterogeneous, incompressible viscous flow shown below as equation (4).

[0034]

number

[0035] Here, p is pressure, ρ is density, v is velocity, g is acceleration due to gravity, z is the height (elevation) from the reference horizontal plane, and w μ represents the energy dissipated by viscosity μ and is given as a function of hydrodynamic resistance and flow rate. Subscripts 1 and 2 represent the inlet and outlet, respectively. The above modified Bernoulli equation holds when the Reynolds number and Mach number are sufficiently smaller than the values ​​for turbulent and compressible flow, respectively. Also, as shown in Figure 12, the deformation of the flow path decreases as the flow moves from the inlet to the outlet, so the flow in this device is not constant. Since Δp = p1 - p2 and the effect of gravity can be ignored, equation (4) can be transformed into equation (5) shown below.

[0036]

number

[0037] Here, the viscosity loss term w μ It can be expressed as follows:

[0038]

number

[0039] Here, Q represents the flow rate, l represents the length of the flow path, w represents the width of the flow path, and h represents the height of the flow path (i.e., the vertical width of the flow path). w as shown in equation (6) μThe values of several specific constants in the mathematical expression representing are derived from a parabolic cross-section used to estimate Δp in the flow channel (see Non-Patent Document 11 for details). In addition, the displacements of PDMS in the z-direction at the inlet and the outlet are represented by h1 and h2, respectively. Based on the results shown in Fig. 10C and Fig. 12 which shows that h2 is a fraction of h1, 500 μm and 100 μm are used for these values respectively for the time being. To calculate the velocities v1 and v2, a simplified assumption is made that the cross-sectional shape of the flow channel is triangular, and it is also assumed that h=(h1+h2) / 2. Notably, this calculation almost accurately reproduced the experimental data including the apparently randomly scattered variations, as shown in Fig. 10D. In contrast, w μ when these values are calculated using Bernoulli's equation without , the calculation results show a linear relationship between Δp and density that differs greatly from the experimental results as shown in Fig. 13. From these results, it can be seen that such random behavior of the data reflects the sum of kinetic energy and viscous loss of each gas, which depends on density and viscosity loss, two gas-specific parameters that vary independently of each other as listed in Table 1. It is also found that Δp linearly depends on the displacement, as shown in Fig. 10E. Therefore, from the mutual relationship between the gas characteristics, the displacement of PDMS and the color change, the physical characteristics of the gas can be determined based on the color pattern of the device of the present invention.

[0040] Since color change occurs when any gas flows through the Ar plasma-treated region, this technique can also be used to display arbitrary patterns in the presence of flow. To demonstrate this concept, a mask having the same shape as the applicant's logo mark shown in Fig. 14A was used to fabricate a device whose structure is conceptually shown in Fig. 14B. When an N2 gas flow is passed through the device at 10 mL / min, the gas flow deforms the portion of PDMS having substantially the same shape as the logo mark, producing a bright color as shown in Fig. 14C.

[0041] The dependence of the color intensity of a gas on various parameters is determined by the pressure changes and deformation amounts required to achieve the desired flow rate, and therefore by the color changes obtained in response to the pressure required to achieve the set flow rate. Although this dependence is nonlinear and highly complex, its pattern is actually quite detailed, and various gases and their properties can be identified using advanced analytical techniques such as machine learning. Gas analysis and gas identification can be achieved even with a small device by combining the equipment according to the present invention with equipment capable of determining density or viscosity.

[0042] [Conclusion] The present invention, while not limited thereto, allows for the measurement of gas flow using a device consisting of, for example, a glass slide and a PDMS slab whose surface is locally treated with Ar plasma and O2 plasma. The use of Ar plasma provides a PDMS surface whose visible optical transmittance changes in response to strain. This optical change, in the form of structural color, is due to the formation of distinct wrinkles on the PDMS surface under strain. Unlike O2 plasma-treated PDMS, Ar plasma-treated PDMS does not adhere to the glass surface. Therefore, by using a mask, a PDMS slab is obtained in which only a portion of the surface is Ar plasma-treated, while the rest is O2 plasma-treated. Thus, a PDMS device is fabricated that does not have pre-formed channels but allows gas to flow only between the Ar plasma-treated region and the glass surface. The gas flow deforms the PDMS, and this deformation results in a color change that correlates with the flow rate, viscosity, and density of the gas used, such as He, Ne, N2, Ar, CO2, and Xe. Herein, the present invention intends to demonstrate the feasibility of gas measurement using this very simple device. By clarifying the dependence of PDMS on many factors, including its thickness and Young's modulus, it will be possible to more accurately measure flow parameters over a wide range by adjusting these factors. Furthermore, the present invention can also be applied to displaying arbitrary patterns, such as logos, through flow. Since this pattern exhibits complex color gradations that reflect the causal relationships of several gas parameters, it will be possible to distinguish between various gas mixtures, such as odors, by performing analysis based on machine learning. The gas measurement and analysis method according to the present invention will contribute not only to a wide range of scientific applications such as flow detection and display, but also to the fields of art and entertainment.

[0043] Although the device according to the present invention is sometimes described as a "device without a flow path," strictly speaking, it is not that there is no flow path (it disappears) when no gas is flowing through it, but rather that the cross-sectional area of ​​the flow path becomes zero (that is, the flow path always exists, but when the gas pressure is zero, the flow path is closed). When gas is injected into the device in this state, the PDMS deforms due to the gas pressure, causing the PDMS to lift away from the substrate, and a flow path with a cross-sectional area larger than zero is formed there, i.e., the flow path opens. Alternatively, the device can be configured so that the cross-sectional area of ​​the flow path is larger than zero even when the gas pressure is zero. If the device is configured so that the cross-sectional area of ​​the flow path is zero when the gas pressure is zero, the PDMS may not deform sufficiently unless the pressure of the gas injected into such a device is sufficiently high, and the cross-sectional area of ​​the flow path may remain zero. Therefore, depending on the various structural parameters of the device, there is a risk that it may not operate when the gas pressure is very low.

[0044] Furthermore, although it is stated that glass (specifically soda-lime glass) is used as the substrate material, other materials can also be used. In the device actually fabricated by the inventors of this invention, the O2 plasma-treated region of the PDMS slab surface and the region of the glass surface to be bonded are both treated with O2 plasma, thereby generating radicals and reactive side chains on both O2 plasma-treated surfaces. Subsequently, bonding is achieved by the reaction between these radicals and reactive side chains when the two surfaces are brought into contact. Therefore, any substrate material that causes the above reaction can be used instead of glass. Although not limited to this, it has been confirmed that silicon substrates can also be used, for example. Alternatively, a substrate with at least a silicon-containing material on its surface may also be used. However, glass is suitable as the substrate material for the device according to the present invention because it is inexpensive and readily available in a variety of specifications.

[0045] As mentioned above, when the PDMS slab and substrate come into contact, no chemicals are needed to particularly accelerate the reaction; simply pressing lightly to ensure contact between the PDMS slab and the substrate is sufficient. Although not essential, maintaining a high temperature (for example, 65°C for several minutes) after contact can further strengthen the bond. Alternatively, if reliable bonding is guaranteed, the PDMS slab surface can be treated with O2 plasma and then brought into contact with a substrate that has not undergone such treatment (followed by further heat treatment as needed) to achieve adhesion.

[0046] It should be noted that Ar plasma treatment is not mandatory for bonding the PDMS slab to the substrate; any bonding method or means suitable for the structure and materials of the device of the present invention can be used. If a bonding method or means other than Ar plasma treatment is used, a substrate made of any material suitable for such a method or means may be used instead of glass (or silicon, etc.).

[0047] Furthermore, while this application uses PDMS as the material for the channel wall, which exhibits structural coloration due to deformation caused by the internal pressure of the channel, other materials may generally be used. The conditions required for such a channel wall are as follows: - The rigidity of at least a portion of the inner surface of the channel wall, which is a region of the channel wall that exhibits structural color, is greater than the rigidity of the portion of the channel wall that lies further inside than that inner surface portion and is adjacent to that inner surface. When the fluid to be measured flows through the channel, at least the region of the channel wall that should exhibit the aforementioned structural color deforms due to the internal pressure of the channel. Due to the deformation described above, periodic wrinkles are formed on the rigid inner surface portion of the channel, and a detectable structural color appears due to the diffraction of light based on these periodically arranged wrinkles.

[0048] Therefore, although this application explains that PDMS is used as the material for the channel wall where wrinkles are formed due to the internal pressure of the channel, it is not limited to PDMS as long as the material satisfies the above conditions. Furthermore, although a highly rigid surface region was formed by hardening the inner wall portion of the channel by Ar plasma treatment, the inner wall portion of the channel wall material may be hardened by other radiation, chemical treatment, or other methods or means, or the inner wall portion may be coated with an inner wall surface material different from that of the channel wall. Also, a channel structure consisting of two types of components, where a component having the above-mentioned surface properties is attached to a substrate made of another material, is not necessarily required; for example, the channel may be formed with a single component. However, the device structure actually fabricated as an example in this application, namely the structure and manufacturing method of bonding a PDMS slab with a part of its surface hardened by Ar plasma treatment to a glass substrate using surface activation by O2 plasma, has already been demonstrated and established as suitable for other types of fluid devices. Therefore, adopting this device structure and manufacturing method is advantageous in that the device of the present invention can be easily fabricated and a reliable device can be realized.

[0049] Although this application describes the device according to the present invention as being used exclusively for gas measurement, considering its principle, it is clear that it can be applied to any fluid, as mentioned earlier. However, when attempting to measure fluids with a much higher density than gases, such as liquids, there is a problem in that structural color is less likely to appear compared to gas measurement. To explain this in detail, interference must occur due to the reflection of light on the surface of periodic wrinkles in order for structural color to appear. For structural color to appear clearly, the above reflection must be of a sufficient magnitude. However, since the inner wall of the flow channel where wrinkles are formed is the interface between the inner wall material of the flow channel and the fluid being measured, in order for such sufficient reflection to occur, the refractive index of the inner wall material of the flow channel (approximately 1.412 when using PDMS, and about 1.4 to 2.0 when using glass) must be significantly different from the refractive index of the fluid. Since the refractive index of gas is almost the same as that of vacuum (a value very close to 1.0), the above requirement regarding the refractive index is satisfied for any gas. On the other hand, when a liquid is applied, the difference in refractive index is generally much smaller than in the case of a gas (the refractive index of water is approximately 1.3334, and that of ethanol is approximately 1.3618), making it difficult in many cases to obtain structural colors that are easily recognizable by the naked eye. Of course, even when the fluid being measured is a liquid, if its refractive index differs significantly from that of the surface portion of the inner wall of the flow path, structural colors that are visible to the naked eye will appear, and in such cases, the present invention can be easily applied. Furthermore, since structural colors are expressed, albeit weakly, as long as the refractive indices of the two do not perfectly match, measurements using the present invention become possible by using image processing or other measurement means that can detect such weak structural colors.

[0050] Furthermore, by slightly modifying the device structure, the problem described above, caused by the proximity of refractive indices between the liquid being measured and the channel wall where wrinkles are formed, can be fundamentally resolved. The direct cause of the problem where structural color is difficult to observe when the fluid being measured is a liquid is that the refractive index of the channel wall where wrinkles are formed comes into contact with the fluid being measured (in this case, a liquid) which has a refractive index close to that of the channel wall. Therefore, wrinkles should be formed only in the parts of the channel wall that do not come into contact with the fluid being measured. Of course, wrinkles may also be formed in the parts that come into contact with the fluid.

[0051] Specifically, in the device according to the present invention described above, the rigidity of the surface (inner wall surface) facing the inside of the flow path, which is part of a component (e.g., a PDMS slab) constituting a portion of the flow path wall, is made higher than that of the inside of this component. When a fluid flows through the flow path, the flow path deforms and a portion of the inner wall surface is compressed, causing wrinkles to form in the area where only the surface has high rigidity, and this results in the appearance of structural color. However, the inner wall surface is not the only surface area that is compressed when the flow path wall deforms due to the flow of fluid through it. For example, refer to Figure 6E, which shows the stress distribution (results of FEA) of each part of the PDMS slab when a fluid flows through a flow path formed by a substrate and a PDMS slab bonded to the substrate (in Figure 6E, it is a cross-sectional view by a plane perpendicular to the flow path, so only the left and right ends are bonded in the figure). Here, the darker the color, the greater the compressive stress applied. In Figure 6E, the inner wall surface of the flow path (the inner surface of the curved part in the center, i.e., the downward-facing surface) is darker in color, indicating that a large compressive stress is applied to this surface. Therefore, as explained above, when compressive stress is applied to the inner wall surface of the channel by Ar plasma treatment, wrinkles are formed there, causing structural color to appear. However, looking at Figure 6E, dark areas also appear on the back surface of the PDMS slab (the outer wall surface of the channel, the upper surface in the figure). More specifically, the areas near the boundary between the curved parts of the PDMS slab, that is, the areas near the boundary between the parts of the PDMS slab that are bonded to the substrate and the parts that are not, are darker than the surrounding areas. In other words, it can be seen that a large compressive stress is applied in the direction along the cross-section in Figure 6E to the areas near both sides of the channel on the outer wall surface of the channel. Note that the parts of the surface where particularly large compression occurs compared to the surrounding areas may be referred to as compression regions below.

[0052] Figure 15 conceptually illustrates that large compressive stresses are also applied to the outer wall surfaces of the channel corresponding to the regions near both sides of the channel. Figure 15 shows an example of the device structure specifically described above, in which a PDMS slab is bonded to a highly rigid substrate. Here, of the two front and back surfaces of the PDMS slab, the lower surface (bottom surface) in the figure is treated with O2 plasma in the portion that is bonded to the substrate, and with Ar plasma in the portion that becomes the inner wall surface of the channel. Furthermore, the opposite surface of the PDMS slab (top surface) is treated with Ar plasma in the same way as the inner wall surface of the channel, so that wrinkles are formed in the region of the top surface where compression occurs, just like on the inner wall surface of the channel.

[0053] Figure 16 shows the results of a simulation using the finite element method to calculate the stress tensor on the upper surface of such a device, i.e., the outer wall surface of the flow channel within the PDMS slab. In this figure, the perspective view ((a)) and top view ((b)) of the device are mapped using shading. In Figure 16, fluid is introduced from the inlet on the left side of the device and flows towards the outlet on the right side. As can be seen from the perspective view (a), the inlet and outlet are connected to the vicinity of the start and end of the flow channel, respectively, via tubular sections extending downward from a circular opening provided on the upper surface of the PDMS slab. In the top view shown in Figure 16 (b), the inlet and outlet are represented by small white circles near the left and right ends of the figure, respectively. The flow channel is connected to the outside only through the inlet and outlet. See also Figure 2A for the structure and location of the inlet and outlet. In the diagram, the channel width (cross-sectional area) decreases from the inlet to the outlet because the outlet side of the channel is narrowed to prevent a significant drop in pressure within the channel when fluid is introduced from the inlet. Such a tapered channel can maintain a relatively high pressure within the channel, even with low flow rates. As a result, even at low flow rates, the deformation of the channel wall becomes larger, leading to a clearer manifestation of structural coloration.

[0054] When a fluid is introduced into the device configured in this way, as shown in the lower part of Figure 15, the fluid enters the unbonded area between the PDMS slab and the substrate, causing the PDMS to deform into a dome shape and form a channel. This deformation compresses a portion of the inner wall of the channel (near the center in the figure), as previously explained, creating periodic wrinkles. However, as explained with reference to Figure 6E and as shown in Figure 15, this formation of periodic wrinkles due to compression also occurs on the opposite side (top surface) of the PDMS slab. Such compressed regions are formed near both sides of the channel, as shown in Figure 15. Therefore, when the fluid flowing through the channel is a gas, structural color appears on both the inner and outer walls of the channel due to the wrinkles formed on both surfaces. On the other hand, when a liquid such as water flows through the channel, structural color is hardly observed on the inner wall surface in contact with the liquid, as previously explained. However, on the outer wall side of the channel, the surface rigidity is higher than the interior due to Ar plasma treatment, similar to the inner wall surface, so periodic wrinkles are similarly formed, especially in the compressed regions near both sides of the channel. Therefore, as long as the outer surface of the channel is exposed and not in close contact with other components or coated with liquid or solid material, structural color will appear regardless of whether the fluid inside the channel is a gas or a liquid.

[0055] As is clear from the above explanation, if periodic wrinkles are formed due to compression on the entire outer wall surface of the channel, or at least in the compression region of the outer wall surface where significant compression occurs, it is possible to produce structural color due to the deformation of the channel, regardless of whether or not there is a structure that forms periodic wrinkles in the compression region on the inner wall surface of the channel. However, if there are circumstances such as the structural color that appears on the inner wall side of the channel having a greater intensity of coloration, periodic wrinkles may be formed on both the outer and inner walls of the channel. [Examples]

[0056] The following describes embodiments of the present invention in detail. It should be noted that the present invention is not limited to these embodiments, and the technical scope of the present invention is defined by the claims.

[0057] Two types of fluid sensors, consisting of a glass substrate and PDMS, were fabricated using the method described below and shown in Figure 2A. These two types of fluid sensors will be referred to as the first and second devices, respectively.

[0058] The inner wall of the first device fabricated in this manner was observed under a microscope with and without N2 gas flow. The results are shown in Figure 1. In addition, the structural color that appeared when no gas was flowing through the first device and when N2 gas was flowing at various flow rates from 5 mL / min to 400 mL / min was observed. These photographs and the R, G, B, and pre-three-color light intensity profiles at positions along the gas flow are shown in Figure 2B. As can be seen from these, when no gas is flowing through the first device, the PDMS slab constituting the first device is not deformed by the internal pressure of the flow path, so almost no structural color appears. However, when gas is flowed, internal pressure is applied to the flow path, causing the PDMS slab to deform, and as a result, structural color appears. As is clear from Figure 2B and Figure 2E, which shows the R, G, B, and pre-three-color light intensity profiles for each flow rate along the flow path, it was confirmed that this structural color changes in response to changes in flow rate, i.e., changes in internal pressure.

[0059] To confirm that the deformation of the PDMS slab, which is the low-rigidity side member of the flow path within the first device, increases with increasing flow rate, a FEA simulation was performed, as detailed in Figures 6A to 6H. The results are shown in Figure 2C. In this simulation, the stress in the direction perpendicular to the flow that the inner wall surface on the PDMS slab side of the flow path receives for various flow rates was directly determined, and this stress naturally causes deformation of the inner wall surface.

[0060] To confirm that periodic wrinkles occur on the inner wall surface due to the deformation described above, the first device was observed using a laser microscope while N2 gas was flowed through it at a flow rate of 10 mL / min. The resulting microscopic image is shown in Figure 2D.

[0061] As an example of the appearance of the device according to the present invention, Figure 12 shows a photograph of the first device, which is an embodiment, when N2 gas is flowing through it at a rate of 400 mL / min.

[0062] To confirm the effect of introducing the aforementioned defects into the PDMS surface, whose rigidity has been increased by Ar plasma treatment of the inner wall of the flow channel, a second device, another embodiment of the present invention, was fabricated by performing the same treatment as the first device, the first embodiment, except that the mask used for Ar plasma treatment was changed to the fine-reinforced mask shown in Figure 3A. As with the first embodiment, Figure 3B (corresponding to Figure 2B of the first embodiment) shows photographs and light intensity profiles when N2 gas at various flow rates is flowed through the second device fabricated in this way, and Figure 3C (corresponding to Figure 2E of the first embodiment) shows the average intensity profiles of R, G, B and undecomposed light for each flow rate along the flow channel. As can be seen from these figures, it can be seen that the structural color changes more sensitively to changes in flow rate in this embodiment using the fine-reinforced mask. Furthermore, by comparing Figure 2D, which shows the results of observing the wrinkles formed in the first device, the first embodiment, with Figure 3D, which shows the results of observing the second device, this embodiment, under the same conditions as the first device, it can be confirmed that more regular wrinkles are formed in the second device using the fine-reinforced mask.

[0063] Furthermore, Figure 3E shows the results of measuring the relationship between the displacement of the PDMS portion of the inner wall of the flow path and the flow rate in this embodiment. By comparing these results with the relationship between the flow rate and the intensity of the structural color shown in Figure 3C, it was confirmed that there is a strong correlation between the displacement of the inner wall of the flow path and the intensity of the structural color. Moreover, as shown in Figure 3F, it was confirmed that the structural color intensity did not change even when the experiment with a large flow rate (500 mL / min) was repeated 50 times, indicating that the operation of the device according to the present invention is sufficiently stable.

[0064] Furthermore, the structural colors of six types of gases, namely He, Ne, N2, Ar, CO2, and Xe, were compared when flowed through the second device of this embodiment. Figure 10A shows the structural colors appearing in the second device when each gas is flowing, as well as the intensity profiles of the structural colors at various positions along the flow path. Figures 10B and 10C show the average intensity of the structural colors in relation to the gas concentration and viscosity in these experiments, Figure 10D shows the relationship between the calculated and experimental values ​​of the gas density and viscosity and the pressure drop between the inlet and outlet of the flow path, and Figure 10E shows the relationship between the pressure drop and displacement. In Figure 11, the graph on the left shows the average intensity, pressure drop, and displacement along the flow path of the structural colors (not tricolor-decomposed), as functions of density, in the results of measuring various gases using the second device. These results were used in the theoretical analysis described above, and their interpretation is also provided; please refer to that explanation for details.

[0065] Furthermore, as a third device, we fabricated a device with a structure similar to the first device, but with additional Ar plasma treatment applied to the outer wall surface of the flow channel of the PDMS slab, so that clear structural colors would appear even when the fluid being measured was a liquid. However, unlike the first device, the third device employed a flow channel that narrows from the inlet to the outlet, as described above. We observed the structural colors that appeared when gas and liquid flowed through this device, respectively.

[0066] Figure 17(a) shows a photograph of the structural color that appeared when nitrogen gas was flowed through the third device, and Figure 17(b) shows a photograph of the structural color that appeared when liquid water was flowed through the same device. In Figure 17(a), the flow path is visible in approximately the lower half of the photograph, while in Figure 17(b), the flow path is visible in approximately the upper half of the photograph. In both cases, the fluid is flowing from right to left. In Figure 17(a), where gas is flowing, structural coloration is visible in the compression region near the center of the inner wall of the channel (the lower part of the photograph (a slightly wider band-like area extending horizontally from the right of the location labeled "N2" in the photograph, appearing brighter than the surrounding area)) and in one of the compression regions on the outer wall of the channel that is within the field of view (a slightly wider band-like area extending horizontally, though slightly upward sloping to the right in the center of the photograph, is the structural color in question). In contrast, in Figure 17(b), where liquid is flowing, no structural coloration is visible in the center of the inner wall of the channel (a dark band-like area extends horizontally in the upper part of the screen corresponding to the center of the channel), and only the appearance of structural coloration in the compression regions on both sides of the outer wall of the channel (a bright band-like area extending horizontally appears slightly below the center of the screen) can be confirmed.

[0067] [Creation of PDMS] A PDMS slab was prepared using a complete set of chemicals (Dow Corning's Sylgard 184) containing a PDMS substrate and hardener. A liquid PDMS mixture consisting of substrate and hardener in a weight ratio of 30:1 was degassed and poured into a Petri dish. After curing this at 65°C overnight, the PDMS was cut into small pieces for later experiments.

[0068] [Plasma treatment] A low-pressure plasma system (Femto, version B) purchased from Dieter electronic GmbH + Co. was used. Ar was used as the plasma source to obtain PDMS that would wrinkle due to strain. O2 was used as another plasma source to create an active surface for adhesion to the glass surface. The area irradiated with plasma was controlled by using a three-dimensionally printed mask. A PDMS piece with the mask attached was placed in the plasma chamber and plasma-treated with plasma power, pressure, and processing time set to 100 W, 0.6 mbar, and 1 minute, respectively.

[0069] [Device fabrication] A device without flow channels was fabricated using a PDMS slab (20 mm × 50 mm × 2.5 mm). The procedure is shown in Figure 2A. Two holes (1.5 mm in diameter) were drilled at both ends of the region to be exposed to Ar plasma to create an inlet and outlet. A mask with a rectangular opening (25 mm × 10 mm) was used to cover the region to be later exposed to O2 plasma. Immediately after Ar plasma treatment, the PDMS slab was stretched at a strain rate of 20% for several seconds. When exposing the PDMS slab to O2 plasma, a negative mask was used to cover the region treated with Ar plasma. A glass substrate was also placed in a plasma chamber, and its surface was activated by O2 plasma. The conditions for this plasma treatment were 35 W, 0.6 mbar, and 20 seconds. The PDMS treated with these two types of plasma was bonded to the glass substrate. The device thus fabricated was placed in an oven and heated at 65°C for several minutes to ensure adhesion at the boundaries.

[0070] [Surface photography under compression using a mold] Ar plasma-treated PDMS (20mm x 50mm x 2.5mm) was bonded to the surface of a three-dimensionally printed mold, as shown in Figure 5B. To control strain, 5m -1 , 10m -1 and 20m -1Three types with different curvatures were fabricated. These curvature values ​​correspond to strains of 0.8%, 1.3%, and 2.5%, respectively. These strained PDMS samples were observed in laser confocal mode using a 3D surface profiler (VK-X3000 from Keyence Corporation).

[0071] [Gas measurement] He, Ne, N2, Ar, CO2, and Xe were used, and the flow was controlled by a mass flow controller (MFC) (SEC-N112MGM from Horiba, Ltd.). The program to control the MFC was designed using LabVIEW (NI Corporation). The gas flow was injected from the inlet at various flow rates, including 5 mL / min, 10 mL / min, 20 mL / min, 50 mL / min, 100 mL / min, 200 mL / min, 300 mL / min, and 400 mL / min. To confirm that there were no leaks, the flow rate was measured at the outlet using a volumetric flowmeter (ProFLOW 6000 electronic flowmeter from Restek Corporation). For color analysis, the device was observed in the presence of flow using a stereomicroscope (Leica S9i from Leica Microsystems). The color changes of the device caused by the flow were analyzed using the software ImageJ (version 1.53k).

[0072] [FEA Simulation] The deformation of PDMS under various gas flow conditions was modeled as a time-dependent problem using the FEA software COMSOL Multiphysics 5.6a. Since it is difficult to model the separation and opening of a gapless interface due to internal gas flow, the phenomenon of a channel forming due to the expansion of the PDMS upon gas injection was modeled as the deformation of a narrow channel with a height of 50 μm under a 400 mL / min N2 flow, assuming no contact force at the interface. This PDMS channel had a width of 10 mm, a length of 2.5 mm, and an upper wall (PDMS slab) thickness of 25 mm. Note that different dimensions were used in the FEA simulation for a third device, as shown in Figure 16, which was configured to exhibit clear structural coloration even when the measured fluid was a liquid. Similarly, since it is difficult to model the opening of a gapless channel due to liquid inflow, the initial channel height was assumed to be 500 μm for this model. For further details on this numerical model, please refer to Non-Patent Document 10. This Non-Patent Document calculates the deformation of smaller flow channels and verifies it experimentally. [Industrial applicability]

[0073] As described in detail above, the present invention provides a device that is small, simple in structure, and easy to manufacture, and can be applied to various applications such as fluid sensors, making it highly useful in industry. [Prior art documents] [Patent Documents]

[0074] [Patent Document 1] Japanese Patent Publication No. 2006-242819 [Non-patent literature]

[0075] [Non-Patent Document 1] JMK Ng, I. Gitlin, AD Stroock, GM Whitesides, Electrophoresis 2002, 23, 3461.

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Non-licensed Document 8

Non-licensed literature 9

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Non-licensed Document 11

Claims

1. It has a flow path surrounded by walls made of a material that deforms at least partially due to the internal pressure applied by a given fluid, Periodic wrinkles are formed on at least a portion of the surface of the wall on the side facing the flow path and on the side opposite to the flow path due to the deformation. A fluid sensor in which structural color appears on at least a portion of at least one of the surfaces due to the aforementioned wrinkles.

2. The at least one surface of the wall has a surface region that is more rigid than the interior of the wall. The fluid sensor according to claim 1, wherein the wrinkles are formed by the compression of at least a portion of the rigid region of at least one of the surfaces due to the deformation.

3. A portion of the wall of the aforementioned channel is made of a material with lower rigidity than the rest of the wall of the aforementioned channel. The fluid sensor according to claim 2, wherein the rigid surface region is located on at least one surface of the flow path in a portion of the flow path wall that is made of a material less rigid than the remaining portion of the flow path wall.

4. The fluid sensor according to claim 3, wherein the low-rigidity material is polydimethylsiloxane.

5. The material constituting the remaining portion of the wall of the channel is a material containing silicon. A first adhesive region on the surface of a first member made of polydimethylsiloxane is bonded to a second adhesive region on the surface of a second member made of a silicon-containing material, the second adhesive region corresponding to the first adhesive region on the surface of the first member. The fluid sensor according to claim 4, wherein a region surrounded by the bonded first and second bonded regions, and which is not bonded itself, is used as the flow path.

6. The fluid sensor according to claim 5, wherein the silicon-containing material is glass or silicon.

7. The fluid sensor according to claim 5, wherein the rigid surface region is formed by Ar plasma treatment of the polydimethylsiloxane surface.

8. Both the first adhesive region of the first member composed of the polydimethylsiloxane and the second adhesive region of the second member composed of the silicon-containing material, or only the first adhesive region, are O ２ The fluid sensor according to claim 5, which is plasma treated.

9. The fluid sensor according to claim 5, wherein the surface of the first member including the first adhesive region and the surface of the second member including the second adhesive region are flat surfaces.

10. The fluid sensor according to claim 1, wherein openings are provided near one end and near the other end of the flow path, and the fluid flows between the two openings.

11. The fluid sensor according to any one of claims 1 to 10, wherein the flow path is closed when the internal pressure due to the fluid is not applied to the surface of the wall of the flow path, and when the internal pressure due to the fluid is applied, the flow path opens as the portion of the wall of the flow path made of the deformable material deforms.

12. A portion of the surface of a component made of polydimethylsiloxane is treated with Ar plasma. At least a portion of the remaining area on the surface of the member is O ２ Processed with plasma, The O of the member ２ By adhering the plasma-treated region to a silicon-containing substrate, the Ar plasma-treated region becomes a flow channel. A method for manufacturing a fluid sensor in which structural color appears on at least a portion of the surface due to the internal pressure applied by a given fluid.

13. The O of the member ２ The method for manufacturing a fluid sensor according to claim 12, wherein the process of bonding the plasma-treated region to the silicon-containing substrate is carried out by bringing the region of the member into contact with the surface of the substrate.

14. The Ar plasma treatment and the O ２ The method for manufacturing a fluid sensor according to claim 13, wherein the plasma processing is performed using a mask in which the transmission-shielding relationship is reversed.

15. The Ar plasma processing is carried out by using a mask that allows Ar plasma to pass through the region designated as the flow path, A method for manufacturing a fluid sensor according to claim 12 or 13, wherein a fine wire-shaped member is provided in a portion of the area on the mask through which the Ar plasma is to be transmitted, thereby protecting the area of ​​the member located below the fine wire-shaped member from irradiation with the Ar plasma.

16. A flow channel surrounded by walls made of a material that deforms at least partially due to the internal pressure applied by a given fluid, Periodic wrinkles are formed on at least a portion of the surface of the wall on the side facing the flow path and on the side opposite to the flow path due to the deformation. A channel in which structural color appears on at least a portion of at least one of the surfaces due to the aforementioned wrinkles.

17. The at least one surface of the wall has a surface region that is more rigid than the interior of the wall. The flow channel according to claim 16, wherein the wrinkles are formed by the compression of at least a portion of the rigid region of at least one of the surfaces due to the deformation.

18. A portion of the wall of the aforementioned channel is made of a material with lower rigidity than the rest of the wall of the aforementioned channel. The channel according to claim 17, wherein the rigid surface region is located on at least one surface of the channel in a portion of the channel wall that is made of a material less rigid than the remaining portion of the channel wall.

19. A portion of the surface of a component made of polydimethylsiloxane is treated with Ar plasma. At least a portion of the remaining area on the surface of the member is O ２ Processed with plasma, The O of the member ２ By adhering the plasma-treated region to a silicon-containing substrate, the Ar plasma-treated region becomes a flow channel. A method for manufacturing a channel in which structural color appears on at least a portion of the surface upon application of internal pressure.

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