Sensor and detection device

Abstract

The present invention suppresses the generation of air bubbles in a flow passage for a liquid and secures a reaction area of a target material in the flow passage. A fluid sensor (1) comprises: a piezoelectric substrate (10); a sensitive film (21) provided on the piezoelectric substrate and including a surface (21S) that reacts with a target substance in a liquid; a measurement unit (11) for propagating a surface acoustic wave (SW) to a region of the surface of the piezoelectric substrate, in which the piezoelectric substrate and the surface overlap; a flow path structure (3) including the surface, a ceiling part (31c) facing the surface, a plurality of side wall parts surrounding sides, and an introduction port (32) and a discharge port (33) for the liquid that are provided separated from each other on the ceiling part, the flow path structure including the surface, the ceiling part, and the plurality of side wall parts in order to form a flow path for the liquid; and first and second structures (34a) and (34b) provided at positions sandwiched by the introduction port and the discharge port of the ceiling part, extending from the ceiling part toward the surface, and separated from the surface and the plurality of side wall parts.

Description

Sensors and Detection Devices

[0001] The present invention relates to sensors and detection devices.

[0002] Conventionally, a sensor is known that detects the amount of a target substance by introducing a liquid into a sensor equipped with a sensitive membrane, causing the sensitive membrane to react with a specific target substance contained in the liquid, and measuring changes in the electrical properties of the sensitive membrane in response to changes in the mass of the sensitive membrane or changes in the vibration propagation characteristics. When introducing a liquid into this sensor located in a flow path, bubbles may be generated. Bubbles generated in the liquid may reduce the sensitivity of the sensor.

[0003] The fluid sensor described in Patent Document 1 is composed of a lower substrate and an upper plate, and has a liquid inlet, a space (flow path) through which the liquid passes, and a liquid outlet inside the upper plate. Here, an inclination angle α is set to gradually increase the height of the space on the inlet side, and an inclination angle θ is set to widen the outlet. An inclination angle β is also set to gradually increase the width of the space when viewed from above. This can suppress the generation of bubbles. Patent Document 2 discloses a technology in which a columnar structure is provided upstream of the detection area to prevent the intrusion of foreign matter, including generated bubbles. Patent Document 3 discloses a technology in which a protruding structure is provided on the lower substrate or the upper plate, or both, upstream of the detection area to mix the introduced liquid.

[0004] U.S. Patent No. 8,968,674 U.S. Patent No. 10,330,643 U.S. Patent No. 10,371,667

[0005] The technology disclosed in Patent Document 1 has a structure in which the space through which the liquid passes is angled and gradually widens, thereby restricting the space through which the liquid passes. This may result in a smaller detection area for the target substance and reduced sensitivity. Furthermore, the technologies disclosed in Patent Documents 2 and 3 require a structure upstream of the detection area, which increases the size of the device. The present invention has been made in consideration of the above-mentioned problems, and aims to provide a sensor and detection device that suppresses the generation of bubbles in a flow channel provided on a surface that reacts with a target substance in a liquid while ensuring a reaction area for the target substance.

[0006] The present invention is a sensor comprising: a piezoelectric body; a sensitive membrane provided on the piezoelectric body, having a surface opposite to the piezoelectric body, and reacting with a target substance; a pair of electrodes provided on the piezoelectric body for propagating elastic waves in at least a region in the piezoelectric body where the piezoelectric body and the surface overlap; a first inner wall including the surface; a second inner wall provided on the piezoelectric body and facing the first inner wall; a plurality of third inner walls surrounding the sides; a flow path structure having a first opening for introducing a liquid and a second opening for discharging the liquid to the outside, the first inner wall, the second inner wall, and the plurality of third inner walls spaced apart from each other in the second inner wall, forming a flow path for the liquid; and a structure provided at a position sandwiched between the first opening and the second opening in the second inner wall, extending from the second inner wall toward the first inner wall, and spaced apart from the first inner wall and the plurality of third inner walls. In the above configuration, the structure may include a first structure disposed on the upstream side of the flow channel and a second structure disposed on the downstream side of the flow channel.

[0007] In the above configuration, the structure may be composed of at least one of a first structure arranged to surround the first opening and having an opening on the upstream side of the flow path when viewed from the normal direction to the surface, and a second structure arranged to surround the second opening and having an opening on the downstream side of the flow path. In the above configuration, the first structure or the second structure may be configured such that an end portion on the second opening side extends toward the second opening side, or an end portion on the first opening side extends toward the first opening side. In the above configuration, the structure may be configured to extend continuously from the upstream side to the downstream side of the flow path. In the above configuration, the structure may have a width equal to or greater than the widths of the first opening and the second opening. In the above configuration, the distance between the structure and two third inner walls opposing each other in the width direction of the flow path may be approximately constant from the upstream side to the downstream side. In the above configuration, the distance between both side surfaces of the structure opposing each other in the width direction of the flow path and the two third inner walls opposing each other in the width direction of the flow path may be approximately the same. In the above configuration, the flow path may be formed in a closed space except for the first opening and the second opening. In the above configuration, the pair of electrodes may be a pair of comb electrodes provided below the sensitive membrane on the piezoelectric body, and may have reflectors provided at positions facing each other with the pair of comb electrodes sandwiched between them in the longitudinal direction of the flow path. In the above configuration, the pair of electrodes may be a pair of first comb electrodes for transmitting the elastic waves and a pair of second comb electrodes for receiving the elastic waves, facing each other with the sensitive membrane sandwiched between them in the longitudinal direction of the flow path. In the above configuration, the pair of electrodes may be a first electrode and a second electrode stacked with the piezoelectric body sandwiched between them, and the sensitive membrane may be positioned so that its surface overlaps with the measuring unit in the stacking direction.

[0008] The present invention is a detection device comprising: a transmitter that transmits a high-frequency signal to generate the elastic wave to the pair of electrodes of a sensor having any of the above configurations; a measuring instrument that measures information about the elastic wave propagated to a portion of the piezoelectric body where the piezoelectric body overlaps with the surface; and a detector that detects the target substance based on the information measured by the measuring instrument.

[0009] The present invention provides a piezoelectric element comprising: a piezoelectric body; a sensitive film provided on the piezoelectric body, having a surface on the side opposite to the piezoelectric body, and reacting with a target substance; a pair of electrodes provided on the piezoelectric body for propagating elastic waves in at least a region in the piezoelectric body where the piezoelectric body and the surface overlap; a first inner wall including the surface; a second inner wall provided on the piezoelectric body and facing the first inner wall; a plurality of third inner walls surrounding the sides; a first opening for introducing a liquid; and a second opening for discharging the liquid to the outside, the first opening and the second opening being spaced apart from each other on either the second inner wall or the third inner wall. or either the first opening or the second opening is provided on the second inner wall, and the one of the first opening or the second opening that is not provided on the second inner wall is provided on the third inner wall, and the sensor is provided with a flow path structure that forms a flow path for liquid, including the first inner wall, the second inner wall, and the plurality of third inner walls, and a structure that is provided at a position facing the surface in the flow path with a predetermined gap therebetween, and that blocks a portion of the liquid that is introduced from the first opening and flows toward the second opening side and diverts it in both directions in the width direction of the flow path. The present invention is a sensor comprising: a piezoelectric body; a sensitive membrane provided on the piezoelectric body, having a surface opposite to the piezoelectric body, and reacting with a target substance; a pair of electrodes provided on the piezoelectric body for propagating elastic waves in at least a region in the piezoelectric body where the piezoelectric body and the surface overlap; a first inner wall including the surface; a second inner wall provided on the piezoelectric body and facing the first inner wall; a plurality of third inner walls surrounding the sides; a flow path structure having a first opening for introducing a liquid and a second opening for discharging the liquid to the outside, the first inner wall, the second inner wall, and the plurality of third inner walls provided spaced apart from each other in the second inner wall or the third inner wall, and forming a flow path for the liquid, the flow path structure including the first inner wall, the second inner wall, and the plurality of third inner walls; and a structure provided at a position sandwiched between the first opening and the second opening, extending from the second inner wall side to the first inner wall side and provided spaced apart from the first inner wall. In the above configuration, the first opening or the second opening may be provided in the third inner wall, and the structure may be provided away from the first inner wall and the plurality of third inner walls.The present invention provides a piezoelectric transducer comprising: a piezoelectric body; a sensitive film provided on the piezoelectric body, having a surface on the opposite side to the piezoelectric body, and reacting with a target substance; a pair of electrodes provided on the piezoelectric body for propagating elastic waves in at least a region in the piezoelectric body where the piezoelectric body and the surface overlap; a first inner wall including the surface; a second inner wall provided on the piezoelectric body and facing the first inner wall; a plurality of third inner walls surrounding the sides; a first opening for introducing a liquid and a second opening for discharging the liquid to the outside, wherein the first opening and the second opening are provided apart from each other on either the second inner wall or the third inner wall; the second inner wall is provided with either the first opening or the second opening, and the third inner wall is provided with either the first opening or the second opening that is not provided in the second inner wall; a flow path structure that forms a liquid flow path including the first inner wall, the second inner wall, and the plurality of third inner walls; and a structure that is provided at a position between the first opening and the second opening, extending from the second inner wall side to the first inner wall side, and is provided away from the first inner wall, and is provided at a position that passes through a line segment with the first opening at one end and the second opening at the other end being the shortest distance.

[0010] According to the present invention, it is possible to suppress the generation of bubbles in the flow channel while ensuring a reaction area for the target substance.

[0011] 6A is a plan view showing a schematic configuration example of a fluid sensor according to the first embodiment. FIG. 6B is a side view showing a schematic configuration example of the fluid sensor of FIG. 1. FIG. 6C is a plan view showing a schematic configuration example of a measurement substrate constituting the fluid sensor of FIG. 1. FIG. 6D is a plan view showing a schematic configuration example of a flow channel structure constituting the fluid sensor of FIG. 1. FIG. 6E is a bottom view showing a schematic configuration example of a flow channel structure constituting the fluid sensor of FIG. 1. FIG. 6F is a partial perspective view of the fluid sensor of FIG. 1. FIG. 6G is a partial plan view of the fluid sensor of FIG. 1. FIG. 6H is a cross-sectional view taken along line A-A' in FIG. 6. FIG. 6H is a cross-sectional view taken along line B-B' in FIG. 6. FIG. 6I is a partial perspective view of FIG. 5 with arrows indicating the flow of liquid. FIG. 7A is a cross-sectional view of FIG. 7A with arrows indicating the flow of liquid. FIG. 7I is a partial perspective view of an example of a fluid sensor according to a modified example of the first embodiment with arrows indicating the flow of liquid. FIG. 7I is a cross-sectional view taken along line A-A' in FIG. 10 with arrows indicating the flow of liquid. FIG. 7A is a partial perspective view of an example of a fluid sensor according to a modified example of the first embodiment with arrows indicating the flow of liquid. FIG. 7B is a cross-sectional view taken along line A-A' in FIG. 10 with arrows indicating the flow of liquid. FIG. 7C is a diagram showing the simulation results of a liquid supply test of a flow channel structure having no structure, and FIG. 7D is a diagram showing the simulation results of a liquid supply test of the flow channel structures according to the first embodiment and its modified example. 16A and 16B are block diagrams illustrating an example of the configuration of a detection device according to a third embodiment of the present invention; FIG. 16B is a graph illustrating the effect of bubble generation on detection results; FIG. 16C is a partial perspective view illustrating a schematic configuration of a fluid sensor according to a second embodiment of the present invention; FIG. 16D is a partial plan view illustrating a schematic configuration of a fluid sensor according to a second embodiment of the present invention; FIG. 16E is a cross-sectional view taken along line A-A' in FIG. 16; FIG. 16F is a cross-sectional view taken along line B-B' in FIG. 16; FIG. 16G is a cross-sectional view taken along line C-C' in FIG. 16; FIG. 15A is a partial perspective view illustrating a schematic configuration of a fluid sensor according to a modified example of the second embodiment of the present invention; FIG. 20A is a cross-sectional view taken along line A-A' in FIG. 20; FIG. 20D is a partial perspective view illustrating a schematic configuration of a fluid sensor according to a modified example of the second embodiment of the present invention; FIG. 20F is a cross-sectional view taken along line A-A' in FIG. 20; FIG. 20C is a partial plan view illustrating another example of the arrangement and configuration of a structure according to the second embodiment of the present invention; and FIG. 20D is a diagram illustrating simulation results of a liquid supply test of the flow channel structures according to the second embodiment and its modified example. FIG. 10 is a plan view showing a schematic configuration example of a delay type fluid sensor according to a modified example of the present invention.1A and 1B are cross-sectional views showing a schematic configuration example of a resonance type fluid sensor using bulk acoustic waves according to a modified example of the present invention. (a) is a partial plan view showing the schematic configuration of a fluid sensor according to a third embodiment of the present invention, and (b) is a side view showing the shapes of an inlet 32A and an outlet 33A. (a) and (b) are partial plan views showing the schematic configuration of a fluid sensor according to a modified example of the third embodiment of the present invention. (a) and (b) are partial plan views showing the schematic configuration of a fluid sensor according to a modified example of the third embodiment of the present invention.

[0012] Hereinafter, the embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. Note that the embodiments described below are examples of means for realizing the present invention, and should be appropriately modified or changed depending on the configuration of the device to which the present invention is applied and various conditions, and the present invention is not limited to the following embodiments.

[0013] Furthermore, in the following drawings, identical or similar parts are designated by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the vertical and horizontal dimensions and scales of components or parts may differ from those of the actual components. Therefore, specific dimensions and scales should be determined with reference to the following explanation. It goes without saying that the dimensional relationships and ratios may differ between the drawings. (First Embodiment and Its Modifications) First, a first embodiment of the present invention and its modifications will be described. FIGS. 1 to 14 are diagrams illustrating the first embodiment and its modifications. [First Embodiment] [Configuration] FIG. 1 is a plan view showing a schematic configuration example of a fluid sensor 1 according to the first embodiment. FIG. 2 is a side view showing a schematic configuration example of the fluid sensor 1, and FIG. 3 is a plan view showing a schematic configuration example of a measurement substrate 2 constituting the fluid sensor 1. As shown in FIGS. 1 to 3, the height direction of the fluid sensor 1 is the Z direction, the longitudinal direction is the X direction, and the planar direction perpendicular to the X direction is the Y direction. This also applies to FIG. 4 and subsequent figures. As shown in Figures 1 to 3, the fluid sensor 1 includes a measurement substrate 2 and a flow path structure 3. The measurement substrate 2 includes a piezoelectric substrate 10 and a measurement unit 11 provided on the piezoelectric substrate 10. In the first embodiment, the planar shape of the piezoelectric substrate 10 is a rectangle with the long side in the X direction and the short side in the Y direction. Here, the rectangle does not have to be a geometric rectangle, and the opposing sides may deviate from parallel by about 10 degrees. The corners may also be rounded. The same applies to the following rectangular shapes.

[0014] The piezoelectric substrate 10 is a substrate made of a piezoelectric material, and can be, for example, a lithium tantalate substrate, a lithium niobate substrate, or a quartz substrate. For example, it can be a single-crystal rotated Y-cut X-propagation lithium tantalate substrate or a single-crystal rotated Y-cut X-propagation lithium niobate substrate. The piezoelectric substrate 10 can also be configured with a piezoelectric film bonded directly or via an insulating layer to a support substrate such as a sapphire substrate, a silicon substrate, a spinel substrate, a quartz substrate, or a quartz substrate. The measurement unit 11 includes a comb electrode 20 provided in the center of the piezoelectric substrate 10 in the X direction, a sensitive film 21 provided on top of the comb electrode 20, and a pair of reflectors 22 provided on both ends of the piezoelectric substrate 10 in the X direction, sandwiching the comb electrode 20 therebetween. The comb electrode 20 is configured by a pair of electrodes arranged crosswise so that their electrode fingers are staggered.

[0015] Applying a high-frequency voltage from the outside to the comb-shaped electrode 20 excites the piezoelectric substrate 10, generating a surface acoustic wave (SAW) with a wavelength corresponding to the electrode pitch. The generated surface acoustic wave (SAW) propagates in the X direction (the direction of the arrow in FIG. 1 ) on the surface of the piezoelectric substrate 10 that overlaps the surface 21S of the sensitive film 21, and is reflected by the reflectors 22 at both ends. As a result, a standing wave of the surface acoustic wave (SAW) is formed on the piezoelectric substrate 10 sandwiched between the pair of reflectors 22, causing a resonance phenomenon. The resonance frequency changes depending on the amount of target material on the surface 21S.

[0016] Although not shown, the comb electrode 20 on the piezoelectric substrate 10 is entirely covered with a protective film that protects the comb electrode 20 from the sample liquid and the like. In other words, the sensitive film 21 is provided on the protective film that covers the comb electrode 20. The protective film can be made of an insulating film such as a silicon oxide film, a silicon nitride film, or a silicon nitride oxide film.

[0017] The comb electrode 20 may be formed from a single layer of, for example, ruthenium (Ru), chromium (Cr), aluminum (Al), titanium (Ti), copper (Cu), molybdenum (Mo), tungsten (W), tantalum (Ta), platinum (Pt), rhodium (Rh), iridium (Ir), or the like, or a laminated film of a plurality of selected types of these films. For example, the comb electrode 20 may be formed from a film in which aluminum is laminated on a titanium lower layer.

[0018] The sensitive film 21 has a structure in which, for example, a conductive film is provided on a protective film, a self-assembled monolayer (SAM) that has high affinity with the conductive film is provided on the conductive film, and an antibody is further provided on the SAM. As an example, the conductive film is composed of a film in which gold is laminated on a titanium base. The antibody specifically reacts with an antigen, which is a target substance in the liquid. The sensitive film 21 is not limited to the above structure, as long as it is configured to react with the target substance in the liquid. As an example, the liquid serving as a sample containing a target substance is a biological sample such as saliva or blood. The target substance may be a protein, an antigen, a virus, or the like.

[0019] In the first embodiment, the reflector 22 has a lattice shape, as shown in FIGS. 1 and 3 . The reflector 22 can be made primarily of, for example, at least one metal selected from aluminum, copper, and molybdenum. As an example, the reflector 22 is made primarily of aluminum. FIG. 4A is a plan view showing a schematic configuration of the flow path structure 3 constituting the fluid sensor 1, and FIG. 4B is a bottom view showing a schematic configuration of the flow path structure 3 constituting the fluid sensor 1. As shown in FIGS. 1 , 2 , 4A, and 4B , the flow path structure 3 is provided on the sensitive film 21 of the piezoelectric substrate 10 so as to cover a portion of the surface 21S of the sensitive film 21.

[0020] Specifically, the flow path structure 3 includes a box-shaped main body 30 having an inner wall portion 31 that forms a flow path 35 through which a liquid flows on the surface 21S of the piezoelectric substrate 10. In addition, the main body 30 is provided with an inlet 32 ​​for introducing a liquid from the outside into the flow path 35, and an outlet 33 for discharging a liquid from the inside of the flow path 35 to the outside. In this configuration, the surface 21S is one of the inner walls that form the flow path 35, and corresponds to the first inner wall. Hereinafter, the inlet 32 ​​side of the flow path 35 will be referred to as the upstream side, and the outlet 33 side will be referred to as the downstream side.

[0021] The flow path structure 3 further includes a first structure 34a and a second structure 34b provided on an upper portion (hereinafter referred to as a "ceiling portion 31c") of the inner wall portion 31 facing the surface 21S between the inlet 32 ​​and the outlet 33 when viewed from a normal direction to the surface 21S, in other words, in a plan view. The ceiling portion 31c is an inner wall facing the surface 21S and corresponds to a second inner wall. The flow path structure 3 is fixed to the piezoelectric substrate 10 by adhesively fixing a bottom surface portion 30B thereof to the piezoelectric substrate 10 via an adhesive member 40. The flow path structure 3 may be provided directly on the piezoelectric substrate 10 without using the adhesive member 40.

[0022] As a result, when viewed from the normal direction to the surface 21S, the sensitive film 21 is surrounded by the adhesive member 40. That is, the inner wall portion 31, adhesive member 40, and piezoelectric substrate 10 of the flow path structure 3 form a flow path 35 containing the sensitive film 21, the first structure 34a, and the second structure 34b. Specifically, the flow path 35 is closed except for the inlet 32 ​​and the outlet 33 by the inner wall portion 31, adhesive member 40, and piezoelectric substrate 10. The flow path structure 3 can be made of a resin material such as PDMS (dimethylpolysiloxane). The adhesive member 40 can be made of, for example, adhesive tape or a thermosetting resin such as PDMS. As an example, the adhesive member 40 is made of adhesive tape. Using adhesive tape can ensure a uniform height of the adhesive portion. The space between the inner wall portion 31 and the outer wall portion that form the box shape of the main body 30 may be solid or hollow. The inlet 32 ​​is cylindrically shaped and penetrates the Y-direction center of the end of the upper main body 30 on the -X-direction side, inside the inner wall 31. The inlet 32 ​​corresponds to the first opening. The outlet 33 is cylindrically shaped and penetrates the Y-direction center of the end of the upper main body 30 on the +X-direction side, inside the inner wall 31. The outlet 33 has the same diameter as the inlet 32. The outlet 33 corresponds to the second opening. That is, the inlet 32 ​​and the outlet 33 are spaced apart from each other in the longitudinal direction of the flow path 35 and are disposed opposite the surface 21S. The shapes of the inlet 32 ​​and the outlet 33 are not limited to cylindrical, and may be other shapes such as rectangular, and may have different diameters. The planar shapes of the first and second structures 34a and 34b are rectangular, with the long side in the X-direction and the short side in the Y-direction, and are disposed opposite each other on the upstream and downstream sides of the flow path 35 at a predetermined distance. Furthermore, when viewed from the normal direction to the surface 21S, the first structure 34a is provided at the center position of the main body 30 in the Y direction and at a position where the upstream end of the flow path 35 is adjacent to the inlet 32. When viewed from the normal direction to the surface 21S, the second structure 34b is provided at the center position of the main body 30 in the Y direction and at a position where the downstream end of the flow path 35 is adjacent to the outlet 33.

[0023] Furthermore, the lengths of the short sides of the first and second structures 34a and 34b are configured to be the same or approximately the same as the diameters of the inlet 32 ​​and the outlet 33. That is, side passages 35s each having a gap of distance d are formed between one end and the other end of the first and second structures 34a and 34b in the Y direction and the side wall portions 31s on the long sides of the inner wall portion 31. The multiple side wall portions of the inner wall portion 31, including the side wall portions 31s, correspond to multiple third inner walls. In this case, the description will be given as four side wall portions. The Y direction corresponds to the width direction of the flow path 35. That is, the two sides of the inner wall portion 31 facing each other in the width direction of the flow path 35 are the side wall portions 31s on the long sides.

[0024] Fig. 5 is a partial perspective view showing the schematic configuration of the fluid sensor 1, and Fig. 6 is a partial plan view showing the schematic configuration of the fluid sensor 1. Fig. 7A is a cross-sectional view taken along line AA' in Fig. 6, and Fig. 7B is a cross-sectional view taken along line BB' in Fig. 6. Figs. 5 to 7B show the inner portion sandwiched between dashed dotted lines P and P' in Fig. 2.

[0025] As shown in FIGS. 5 and 7A , the first and second structures 34a and 34b are integrally formed with the ceiling portion 31c of the inner wall portion 31 of the main body 30 and extend downward from the ceiling portion 31c toward the surface 21S. That is, the first and second structures 34a and 34b extend from the ceiling portion 31c toward the surface 21S. In addition, the first and second structures 34a and 34b are provided with a predetermined distance h from the opposing surface 21S. As a result, as shown in FIGS. 7A and 7B , the height h from the surface 21S to the lower ends of the first and second structures 34a and 34b is lower than the height H from the surface 21S to the ceiling portion 31c. Furthermore, as shown in FIG. 7A , a groove portion 35b is formed between the first structure 34a and the second structure 34b by the opposing ends of these structures and the ceiling portion 35c.

[0026] Here, fluid sensor 1 is a sensor designed to detect a target substance contained in a sample liquid. The liquid to be tested is introduced through inlet 32 ​​using a pump, pipette, or the like. The liquid introduced into flow path 35 from inlet 32 ​​flows through flow path 35 toward outlet 33, filling flow path 35. After flow path 35 is nearly filled with liquid, the liquid is pushed out through outlet 33 by the amount introduced. In this way, the liquid is discharged from outlet 33. In other words, a liquid supply mechanism and a discharge mechanism are formed by flow path structure 3 provided on piezoelectric substrate 10. Detection of the target substance is performed when flow path 35 is nearly filled with liquid. However, if air bubbles are present in flow path 35 at this time, the air bubbles will cause noise and reduce detection accuracy. FIG. 8 is a partial perspective view of FIG. 5 with arrows indicating the flow of liquid, and FIG. 9 is a cross-sectional view of FIG. 7A with arrows indicating the flow of liquid.

[0027] Liquid introduced from the inlet 32 ​​into the flow path 35, the interior of which is occupied by gas, flows toward the outlet 33. It has been experimentally shown that bubbles are likely to occur when there is a large imbalance in the flow rates between the inlet 32 ​​and the outlet 33, as viewed from the normal direction to the surface 21S. For example, the flow rate of liquid flowing through a path passing through the diameter of the inlet 32 ​​and the outlet 33 and connecting the centers of the circles (hereinafter referred to as the "shortest path") is relatively high, while the flow rate of liquid flowing in an area outside the shortest path is relatively low. In the first embodiment, as shown in FIGS. 8 and 9 , a portion of the liquid attempting to flow through the shortest path after introduction is blocked by the first structure 34a and detoured in both directions in the Y direction (horizontal direction).

[0028] That is, as shown in Fig. 8, the introduced liquid flows laterally around the first structure 34a through the side paths 35s on both sides thereof toward the discharge port 33, and then, as shown in Figs. 8 and 9, flows around to the underside of the first structure 34a toward the discharge port 33. Some of the flowing liquid flows into the groove 35b on its way toward the discharge port 33 and accumulates there, but most of the liquid remains in its original flow through the side paths 35s on both sides of the second structure 34b and flows below the second structure 34b.

[0029] This reduces the flow rate of the liquid flowing through the shortest path compared to when the first and second structures 34a and 34b are not present, and the liquid flows in a detour in the horizontal direction, allowing the liquid to flow efficiently to the area outside the shortest path. In other words, compared to when the first and second structures 34a and 34b are not present, the deviation in the flow rate of the liquid between the shortest path and the area outside it can be reduced. [Modification of the First Embodiment] Next, a modification of the first embodiment will be described. [Configuration] FIG. 10 is a partial perspective view showing a schematic configuration example of a fluid sensor 1A according to a modification of the first embodiment, with arrows indicating the flow of liquid added. FIG. 11 is a cross-sectional view taken along line A-A' in FIG. 10, with arrows indicating the flow of liquid added.

[0030] As shown in FIGS. 10 and 11 , the fluid sensor 1A differs from the fluid sensor 1 of the first embodiment in that it includes a flow path structure 3A instead of the flow path structure 3 of the fluid sensor 1. Below, the differences from the first embodiment will be described in detail, and overlapping parts will be denoted by the same reference numerals and description thereof will be omitted as appropriate. The flow path structure 3A of the fluid sensor 1A is configured such that the first and second structures 34a and 34b of the flow path structure 3 of the first embodiment are replaced with a structure 34A. When viewed from the normal direction to the surface 21S, the structure 34A is provided on the ceiling portion 31c facing the surface 21S between the inlet 32 ​​and the outlet 33 of the flow path structure 3A. The planar shape of the structure 34A is rectangular with the long side in the X direction and the short side in the Y direction. When viewed from the normal direction to the surface 21S, the structure 34A is located at the center of the main body 30 in the Y direction, with one upstream end adjacent to the inlet 32 ​​and the other downstream end adjacent to the outlet 33. The structure 34A has a width equal to or substantially equal to the diameter of the inlet 32 ​​and extends continuously from the position adjacent to the inlet 32 ​​to the position adjacent to the outlet 33. Additionally, a bypass passage 35s having a gap of distance d is formed between one end and the other end of the structure 34A in the Y direction and the side wall portion 31s on the long side of the inner wall portion 31. As shown in FIG. 11 , the structure 34A is integrally formed with the ceiling portion 31c of the inner wall portion 31 of the main body 30 and protrudes downward from the ceiling portion 31c toward the surface 21S. Furthermore, the structure 34A is provided with a predetermined distance h from the opposing surface 21S. As a result, as shown in Fig. 11 , the height h from the surface 21S to the lower end of the structure 34A is lower than the height H from the surface 21S to the ceiling portion 31c. In this modification, as shown in Fig. 10 and 11 , a portion of the liquid that attempts to flow along the shortest path after being introduced is blocked by the structure 34A and detours in both directions in the Y direction (horizontal direction). That is, as shown in Fig. 10 , the introduced liquid detours laterally through the side paths 35s on both sides of the structure 34A toward the outlet 33, and also flows around to the underside of the structure 34A toward the outlet 33, as shown in Fig. 10 and 11 .Furthermore, in this modified example, unlike the structure of the first embodiment, the structure is not interrupted midway, and there is no region that obstructs the flow midway, as in the groove portion 35b of the first embodiment.

[0031] As a result, the flow rate of the liquid flowing through the shortest path can be reduced compared to when the structures 34A are not provided, and the liquid flows in a detour in the lateral direction, allowing the liquid to flow efficiently to the area outside the shortest path. In other words, compared to when the structures 34A are not provided, the bias in the flow rate between the shortest path and the area outside it can be reduced. [Simulation Results of Liquid Supply Test] Next, the results of a liquid supply test using a simulator for a conventional flow path structure not provided with structures, and the flow path structures according to the first embodiment and its modified examples will be described.

[0032] FIG. 12( a) is a diagram showing the results of a simulation of a liquid supply test to a structure without a structural body (hereinafter referred to as an "intangible structure"). FIGS. 12( b) and 12(c) are diagrams showing the results of a simulation of a liquid supply test to a flow path structure according to the first embodiment and its modified examples. Note that FIGS. 12( a) to 12(c) show half of the space filled with liquid, including the inlet 32 ​​and the outlet 33, cut in the X direction at the center in the Y direction. The simulation was performed using ANSYS Fluent (registered trademark), a fluid analysis software, and a VOF (Volume of Fluid) model solver type capable of analyzing free surfaces was used as a multiphase flow model.

[0033] The figure also illustrates the state in which pure water is continuously introduced into the flow path 35 from the inlet 32, from a state in which the flow path 35 is filled with gas, and then reaches a steady state. The steady state refers to a state in which the amount of gas contained therein hardly changes over time. In other words, it is a state in which the density of bubbles relative to the volume of the flow path hardly changes. In the simulation results shown in Figures 12(a) to 12(c), region 120 is the region containing the most gas, region 121 is the region containing the next most gas after region 120, and region 122 is the region containing the next most gas after region 121. Region 123 is the region containing the most liquid, and region 124 is the region containing the next most liquid after region 123. Note that region 124 contains less gas than region 122. In comparison with the solid structure of Figure 12(a), the flow path structures of the first embodiment and its modified examples of Figure 12(b) and Figure 12(c) have a reduced area of ​​region 120, particularly at the downstream end of flow path 35, which means that the generation of bubbles is suppressed.

[0034] Furthermore, in the flow path structure according to the first embodiment shown in FIG. 12(b) and the flow path structure according to the modified example of the first embodiment shown in FIG. 12(c), the area of ​​region 120 at the downstream end of the flow path structure according to the modified example is slightly smaller than that of the flow path structure according to the first embodiment. This indicates that the overall amount of bubbles is reduced compared to the inert structure. Meanwhile, in the flow path structure according to the first embodiment, as shown in FIG. 12(b), the region 123 in the inert structure has partially changed to region 124, and in the flow path structure according to the modified example, there is also a portion that has changed to region 122. [Regarding Target Substance Detection] FIG. 13 is a block diagram showing an example configuration of a detection device 100, and FIG. 14 is a graph illustrating the effect of bubble generation on detection results. In FIG. 14, the horizontal axis represents frequency, and the vertical axis represents the admittance of a resonant fluid sensor. The detection device 100 is a device that measures target substances in liquids using a fluid sensor, and is compatible with both resonant and delay-type fluid sensors.

[0035] The fluid sensors 1 and 1A shown in the first embodiment and its modified examples correspond to a resonance-type configuration. Although only the reference symbols for the fluid sensors 1 and 1A are shown in FIG. 13 , the fluid sensors according to the second embodiment, the modified example of the second embodiment, and other modified examples described below can also be applied to the detection device 100. As shown in FIG. 13 , the detection device 100 includes a transmitter 101, a receiver 102, a measuring device 103, and a detector 104. The fluid sensor is connected to corresponding terminals of the transmitter 101, receiver 102, and measuring device 103 of the detection device 100 via terminals (not shown). In the case of the resonance-type fluid sensors 1 and 1A, the fluid sensor is connected to the transmitter 101 and measuring device 103. The transmitter 101 transmits a high-frequency signal to the comb-shaped electrode 20 of the fluid sensor 1 or 1A. This applies a high-frequency voltage to the comb-shaped electrode 20. In the case of a delay-type fluid sensor, the high-frequency signal is transmitted to the measuring device 103 in addition to the comb-shaped electrode on the transmitting side. In the case of a delay-type fluid sensor, the receiver 102 receives the signal of the elastic wave received by the interdigital electrode on the receiving side. The received signal is output to the measuring device 103.

[0036] In the case of a resonance-type fluid sensor, the measuring instrument 103 measures, for example, the frequency of the oscillation signal output by the fluid sensor 1 or 1A. On the other hand, in the case of a delay-type fluid sensor, the measuring instrument 103 measures, for example, the phase difference between the high-frequency signal transmitted by the transmitter 101 and the high-frequency signal received by the receiver 102. Note that this configuration is not limited, and the measuring instrument 103 may have other measurement modes, such as measuring the phase difference for a resonance-type fluid sensor. In the case of a resonance-type fluid sensor, for example, the detector 104 detects the target substance based on the amount of change in the frequency of the oscillation signal measured by the measuring instrument 103. On the other hand, in the case of a delay-type fluid sensor, for example, the detector 104 detects the target substance based on the amount of change in the phase difference measured by the measuring instrument 103.

[0037] Specifically, measurement by the fluid sensor 1 or 1A involves, for example, propagating a surface acoustic wave SW to generate a standing wave in a state where the flow path 35 is filled with a liquid that does not contain a target substance, and measuring frequency information at that time. Next, using a similar procedure, frequency information is measured in a state where the flow path 35 is filled with a liquid that contains the target substance. Note that the supply of liquid to the fluid sensor 1 or 1A may be performed manually using a pipette or the like, but the detection device 100 may also be configured to be equipped with a separate electric pump (not shown) or the like to automatically supply liquid.

[0038] The measurement results of the measuring instrument 103 can be displayed as the relationship between frequency and admittance, as shown in FIG. 14, for example. That is, the frequency at which admittance, which is the reciprocal of impedance, is greatest is the resonant frequency. This resonant frequency changes depending on whether or not a target substance is present. Measurement result 300 in FIG. 14 shows the relationship between frequency and admittance (|Y|) when measuring air, and measurement results 301 and 302 show the measurement results for a liquid containing a target substance.

[0039] If the liquid contains a target substance, the target substance reacts on surface 21S. The mass acting on comb electrode 20 changes depending on the amount of target substance on surface 21S, causing a change in the resonant frequency. In other words, the presence or amount of the target substance can be detected from the amount of change in the resonant frequency (see Δf in FIG. 14 ).

[0040] However, if bubbles are generated in the liquid filling the flow path 35, the bubbles will act as noise, causing changes in the measurement value. The more bubbles there are, the more the signals from the gas and liquid components will mix, making it difficult to accurately detect the target substance. In other words, the more bubbles there are in the liquid in the flow path 35, the smaller the overall mass will be, and changes in mass will occur regardless of the amount of target substance. Furthermore, the surface acoustic waves (SAW) that propagate through the portion of the piezoelectric substrate 10 that overlaps with the bubble portion have different propagation velocities than the surface acoustic waves that propagate through the portion that overlaps with the liquid portion, and this change in propagation velocity also acts as noise and adversely affects the measurement results.

[0041] In the example shown in Fig. 14, two types of measurement results, measurement results 301 and 302, are obtained for the measurement results in air. Normally, two measurement results are obtained: measurement result 300, which is the measurement result in air, and measurement result 302, which is the measurement result in liquid containing target substances, etc. However, due to changes in the propagation speed of elastic waves caused by bubbles, measurement result 301 may be obtained as an additional result. In this case, accurate detection of the target substance becomes impossible. [Effects of the first embodiment and its modifications]

[0042] As described above, the fluid sensor 1 according to the first embodiment is configured to include the piezoelectric substrate 10 and the sensitive film 21 that is provided on the piezoelectric substrate 10 and has a surface 21S on the side opposite to the piezoelectric substrate 10, and that reacts with a target substance. In addition, the fluid sensor 1 is configured to include the measuring unit 11 that is provided on the piezoelectric substrate 10 and has the comb-shaped electrode 20 and reflector 22 for propagating an elastic wave at a portion of the surface of the piezoelectric substrate 10 where the piezoelectric substrate 10 and the surface 21S overlap. The piezoelectric substrate 10 is further provided with a flow path structure 3 having a surface 21S, a ceiling portion 31c facing the surface 21S, four inner wall portions including sidewall portions 31s surrounding the sides, and first openings (inlet ports 32) for introducing liquid into the flow path 35 and second openings (outlet ports 33) for discharging the liquid in the flow path 35 to the outside, the first openings being spaced apart in the ceiling portion 31c along the longitudinal direction of the flow path 35, the first openings being spaced apart in the ceiling portion 31c along the longitudinal direction of the flow path 35, the second openings being spaced apart in the ceiling portion 31c along the longitudinal direction of the flow path 35, the first openings being spaced apart in the ceiling portion 31c along the longitudinal direction of the flow path 35, and the second openings being spaced apart in the ceiling portion 31c along the longitudinal direction of the flow path 35. The piezoelectric substrate 10 is further provided with a first structure 34a and a second structure 34b extending from the ceiling portion 31c toward the surface 21S and spaced apart from the surface 21S and the four sidewall portions. Specifically, the first structure 34 a is provided on the upstream side of the flow path 35 , and the second structure 34 b is provided on the downstream side of the flow path 35 .

[0043] Furthermore, the fluid sensor 1A according to the modified example of the first embodiment includes a structure 34A instead of the first and second structures 34a and 34b of the fluid sensor 1. The structure 34A is disposed between the inlet 32 ​​and the outlet 33 when viewed from the normal direction to the surface 21S, and extends continuously from the upstream side to the downstream side of the flow path 35. The inner wall 31 and the first and second structures 34a and 34b (or the structure 34A) are configured so that the side paths 35s have the same distance d on both sides of the flow path 35 and are spaced at a constant distance from the upstream side to the downstream side of the flow path 35. The flow path 35 is closed by the surface 21S, the inner wall 31, the adhesive member 40, and the piezoelectric substrate 10, except for the inlet 32 ​​and the outlet 33.

[0044] In the configurations of the first embodiment and its modified examples, the first and second structures 34a and 34b or the structure 34A can block a portion of the liquid introduced through the inlet 32 ​​and divert it laterally (in the +Y and −Y directions). This allows the liquid flow to be divided into a flow that wraps around under the first and second structures 34a and 34b or the structure 34A and a flow that diverts laterally. As a result, the flow rate of the liquid flowing along the shortest path between the inlet 32 ​​and the outlet 33 can be reduced compared to when the structures are not present, and the liquid diverted laterally can efficiently spread to the area outside the shortest path. This reduces the imbalance in the flow rate of the liquid between the shortest path and the area outside it, and suppresses the generation of bubbles due to the supply of liquid into the flow path 35. In addition, because the first and second structures 34a and 34b or the structure 34A are positioned opposite the surface 21S, the device can be made more compact than conventional configurations in which the first and second structures 34a and 34b or the structure 34A are located upstream.

[0045] Furthermore, the detection device 100 according to the first embodiment and its modifications can detect a target substance in a liquid using the fluid sensor 1 or 1A, thereby enabling detection of the target substance in an environment with less noise due to air bubbles. As a result, the target substance can be detected more accurately than in the past. (Second Embodiment and Modification) Next, a second embodiment of the present invention and its modifications will be described. FIGS. 15 to 23 are diagrams illustrating the second embodiment and its modifications. [Second Embodiment] [Configuration] FIG. 15 is a partial perspective view showing the schematic configuration of a fluid sensor 1B according to the second embodiment (hereinafter referred to as "fluid sensor 1B"), and FIG. 16 is a partial plan view showing the schematic configuration of the fluid sensor 1B according to the second embodiment. The second embodiment differs from the first embodiment and its modifications in that it includes a first structure 36a and a second structure 36b, which have different structures, instead of the first structure 34a and the second structure 34b of the first embodiment. Hereinafter, the same components as those described in the first embodiment and its modifications will be designated by the same reference numerals and will not be described as appropriate. Differences from the first embodiment and its modifications will be described in detail. As shown in FIGS. 15 and 16, the fluid sensor 1B includes a measurement substrate 2 and a flow path structure 3B.

[0046] The flow path structure 3B has a configuration in which, instead of the first structures 34a and the second structures 34b in the flow path structure 3 of the first embodiment, a first structure 36a and a second structure 36b having different structures are provided. The other configurations are the same as those of the flow path structure 3.

[0047] When viewed from the normal direction to the surface 21S, the first structure 36a includes a pair of arms 360a extending parallel to the X direction with the inlet 32 ​​sandwiched therebetween in the Y direction, and a connecting portion 362a connecting the downstream ends of the arms 360a. That is, when viewed from the normal direction to the surface 21S, the first structure 36a is disposed so as to surround the inlet 32 ​​and has an opening on the upstream side of the flow path 35. The planar shape of the second structure 36b is a shape obtained by rotating a substantially U-shape 90 degrees clockwise. In other words, the second structure 36b has a shape obtained by rotating the first structure 36a 180 degrees around the axis normal to the surface 21S.

[0048] When viewed from the normal direction to the surface 21S, the second structure 36b includes a pair of arms 360b extending parallel to the X direction with the outlet 33 sandwiched therebetween in the Y direction, and a connecting portion 362b connecting the upstream ends of the arms 360b. That is, when viewed from the normal direction to the surface 21S, the second structure 36b is disposed so as to surround the periphery of the outlet 33 and has an opening on the downstream side of the flow path 35.

[0049] Furthermore, the width in the Y direction of the first and second structures 36a and 36b is configured to be shorter than the length between the opposing surfaces of the side wall portion 31s on the long side of the inner wall portion 31. That is, a bypass path 35s having a gap of d2 (d2<d) is formed between the arm portions 360a and 360b of the first and second structures 36a and 36b and the side wall portion 31s (see FIG. 16). Here, FIG. 17A is a cross-sectional view taken along line A-A' in FIG. 16, FIG. 17B is a cross-sectional view taken along line B-B' in FIG. 16, and FIG. 17C is a cross-sectional view taken along line CC' in FIG. 16.

[0050] As shown in FIGS. 15 , 17A , and 17B , the first and second structures 36a and 36b are integrally formed with the ceiling portion 31c of the inner wall portion 31 of the main body 30 and extend downward from the ceiling portion 31c toward the surface 21S. That is, the first and second structures 36a and 36b extend from the ceiling portion 31c toward the surface 21S. In addition, the first and second structures 36a and 36b are provided with a predetermined distance h from the opposing surface 21S. As a result, the height h from the surface 21S to the lower ends of the first and second structures 36a and 36b is lower than the height H from the surface 21S to the ceiling portion 31c. Furthermore, as shown in FIGS. 17A and 17B , a space of height H in which no structures are present is defined between the first and second structures 36a and 36b and their connecting portions 362a and 362b. 18 is a partial perspective view of FIG. 15 with arrows indicating the flow of liquid, and FIG. 19 is a cross-sectional view of FIG. 17A with arrows indicating the flow of liquid.

[0051] 18 and 19 , after the liquid is introduced, part of the liquid that attempts to flow along the shortest path is blocked by the connecting portion 362a of the first structure 36a and is repelled in the −X direction (toward the upstream end of the flow path 35) by the connecting portion 362a and the pair of arms 360a. At this time, part of the liquid repelled by the connecting portion 362a flows along the arms 360a inside the area surrounded by the first structure 36a toward the upstream end, which is the upstream end of the flow path 35.

[0052] This liquid further bounces back at the upstream end and flows laterally through the side paths 35s on both sides of the first structure 36a, detouring toward the discharge port 33. The other part of the liquid flows around to the underside of the first structure 36a and toward the discharge port 33, as shown in Figures 18 and 19 .

[0053] The liquids flowing laterally and downwardly meet in a structure-free region between the first and second structures 36a and 36b on their way toward the outlet 33. Then, they are forced to detour laterally again by the second structure 36b, flowing laterally through the side paths 35s on both sides of the second structure 34b and flowing around under the second structure 36b. Furthermore, the liquid flowing laterally passes through the side paths 35s on the outside of the arms 360b of the second structure 36b, bounces off the downstream end of the flow path 35, and flows into the outlet 33 from the opening side of the second structure 36b. That is, the liquid flows into the outlet 33 by detouring around the arms 360b of the second structure 36b. This reduces the flow rate of the liquid flowing along the shortest path compared to when the first and second structures 36a and 36b are not present, and the liquid detours laterally, allowing the liquid to flow efficiently in the region outside the shortest path. Furthermore, by orienting the openings of the first and second structures 36a and 36b toward the upstream and downstream ends of the flow path 35, respectively, it is possible to form a flow of liquid toward both ends. That is, compared to a case where the first and second structures 36a and 36b are not present, it is possible to reduce the bias in the flow rate of liquid between the shortest path and the area outside it. [Modification of Second Embodiment] [Configuration] Fig. 20 is a partial perspective view showing a schematic configuration example of a fluid sensor 1C according to a modification of the second embodiment, with arrows indicating the flow of liquid added. Fig. 21 is a cross-sectional view taken along line A-A' in Fig. 20, with arrows indicating the flow of liquid added.

[0054] As shown in FIGS. 20 and 21 , the fluid sensor 1C differs from the fluid sensor 1B of the second embodiment in that it includes a flow path structure 3C instead of the flow path structure 3B of the fluid sensor 1B. Below, the differences from the second embodiment will be described in detail, and overlapping parts will be denoted by the same reference numerals and will not be described again as appropriate. The flow path structure 3C of the fluid sensor 1C is configured such that, instead of the first and second structures 36a and 36b in the flow path structure 3B of the second embodiment, it includes first and second structures 36Aa and 36Ab, which have different connection structure. The first structure 36Aa includes a pair of arms 360a and a connection portion 364a connecting the downstream ends of the arms 360a. The connection portion 364a is configured by continuously extending the connection portion 362a of the second embodiment toward the center in the +X direction. Similarly to the second embodiment, the first structure 36Aa opens toward the upstream end of the flow path 35 and is disposed so as to surround the periphery except for the opening side of the inlet 32. The second structure 36Ab includes a pair of arms 360b and a connecting portion 364b that connects the upstream ends of the arms 360b. The connecting portion 364b is configured by continuously extending the connecting portion 362b of the second embodiment toward the center in the -X direction. Similarly to the second embodiment, the second structure 36Ab opens toward the downstream end of the flow path 35 and is disposed so as to surround the periphery except for the opening side of the outlet 33.

[0055] Furthermore, similar to the first and second structures 36a and 36b of the second embodiment, the widths in the Y direction of the first and second structures 36Aa and 36Ab are configured to be shorter than the length between the opposing surfaces of the side wall portions 31s on the long sides of the inner wall portion 31. That is, between the arm portions 360a and 360b of the first and second structures 36Aa and 36Ab and the side wall portions 31s, bypass paths 35s each consisting of a gap with a distance d2 are formed.

[0056] The first and second structures 36Aa and 36Ab are provided at a predetermined interval along the X direction of the flow path structure 3C. A groove portion 35b is formed between the first structure 36Aa and the second structure 36Ab by their opposing ends and the ceiling portion 35c.

[0057] The first and second structures 36Aa and 36Ab are integrally formed with the ceiling portion 31c of the inner wall portion 31 of the main body 30, and extend downward from the ceiling portion 31c toward the surface 21S. That is, the first and second structures 36Aa and 36Ab extend from the ceiling portion 31c toward the surface 21S.

[0058] Furthermore, the first and second structures 36Aa and 36Ab are provided with a predetermined distance h from the opposing surface 21S, so that the height h from the surface 21S to the lower ends of the first and second structures 36Aa and 36Ab is lower than the height H from the surface 21S to the ceiling 31c, as shown in Fig. 21 .

[0059] In this modification, as shown in FIGS. 20 and 21 , the liquid flows from the introduction to the middle of the flow in the same manner as in the first and second structures 36a and 36b of the second embodiment. Meanwhile, the liquid that flows around the outside of the arm 360a toward the outlet 33 and the liquid that flows around the underside of the connection 364a toward the outlet 33 flow along the connection 364a toward the groove 35b at the center in the X direction. Therefore, some of the flowing liquid flows into the groove 35b and accumulates there. However, the second structure 36Ab allows most of the liquid to continue flowing horizontally through the side passage 35s outside the arm 360b and below the connection 364b. This reduces the flow rate of the liquid flowing along the shortest path compared to when the first and second structures 36Aa and 36Ab are not present. Furthermore, the liquid detouring laterally allows the liquid to flow efficiently to the area outside the shortest path. Furthermore, by orienting the openings of the first and second structures 36Aa and 36Ab toward one end and the other end of the flow path 35 in the X direction, respectively, it is possible to form a flow of liquid toward both ends. That is, compared to a case where the first and second structures 36Aa and 36Ab are not present, it is possible to reduce the bias in the flow rate of liquid between the shortest path and the area outside it. [Simulation Results of Liquid Supply Test] Next, with reference to FIGS. 12(a) to (c) and 22(a) and (b), the results of a liquid supply test performed using a simulator on the flow path structures according to the second embodiment and its modified example will be described.

[0060] 22(a) and 22(b) show the results of a simulation of a liquid supply test for the flow channel structure according to the second embodiment and its modified example. Note that FIGS. 22(a) and 22(b) show half of the space filled with liquid, including the inlet 32 ​​and the outlet 33, cut in the X direction at the center in the Y direction. The simulation was performed using the same fluid analysis software as in the first embodiment under the same conditions. The simulation also depicts a state in which the flow channel 35 is filled with gas, and then pure water is continuously introduced into the flow channel 35 from the inlet 32, resulting in a steady state. Compared to the solid structure shown in FIG. 12(a), the flow channel structures according to the second embodiment and its modified example shown in FIGS. 22(a) and 22(b) show a reduced area of ​​the gas-filled region overall. In particular, the upstream end of the flow channel 35 does not have the regions 121 and 122 containing relatively large amounts of gas, which were present in the flow channel structures according to the first embodiment and its modified example shown in FIGS. 12(b) and 12(c).

[0061] 12(b) and 12(c) , the bubble region 120 that appeared in the structure of the first embodiment described above has disappeared, and the regions 121 and 122 have been significantly reduced at the downstream end of the flow path 35. Also, unlike the flow path structures of the first embodiment and its modified example, the region 123 that was free of bubbles in the non-bubble structure of FIG.

[0062] In particular, the structure of the modified example of the second embodiment shown in FIG. 22(b) is a combination of the structure of the second embodiment shown in FIG. 22(a) and the structure of the first embodiment shown in FIG. 12(b), and exhibits the greatest bubble suppression effect. Specifically, a small region 122 exists at the downstream end of the flow path 35, but the remaining region is a region 123 that does not contain bubbles. Although not shown, simulation results similar to those shown in FIG. 22(b) were also obtained when the connecting portions 364a and 364b in the structure of FIG. 22(b) were connected in series. Next, the results of similar simulations performed on a configuration in which only the first structure 36a and only the second structure 36b are arranged in the fluid sensor 1B will be described.

[0063] 23(a) and 23(b) are partial plan views showing the schematic configurations of fluid sensors 1D and 1E according to other modifications of the second embodiment. FIGS. 23(c) and 23(d) are diagrams showing the results of a simulation of a liquid supply test for the fluid sensors 1D and 1E of FIGS. 23(a) and 23(b). As shown in FIG. 23(a), the fluid sensor 1D has a configuration similar to that of the fluid sensor 1B, except that only the first structure 36a is disposed. As shown in FIG. 23(b), the fluid sensor 1E has a configuration similar to that of the fluid sensor 1B, except that only the second structure 36b is disposed. As shown in FIG. 23(c), the simulation results for the fluid sensor 1D show that the upstream end of the flow path 35 is filled with a bubble-free region 123, similar to the simulation results for the second embodiment and its modifications shown in FIGS. 22(a) and 22(b). 12(a), the downstream end of flow path 35 has region 120 where bubbles exist, region 121 which contains the next most gas after region 120, and region 122 which contains the next most gas after region 121. Therefore, it can be seen that a configuration provided with only first structure 36a is unable to deal with bubbles that occur at the downstream end of flow path 35. On the other hand, the simulation results for fluid sensor 1E, as shown in FIG. 23(d), show that the area of ​​the region occupied by gas is reduced overall compared to the inorganic structure of FIG. 12(a).

[0064] However, at the upstream end of the flow path 35, the amount of bubbles is reduced compared to the solid structure of FIG. 12(a), but regions 121 and 122 are present. Also, at the side of the inlet 32 ​​of the flow path 35, the amount of bubbles is reduced compared to the solid structure of FIG. 12(a), but region 124 is also present. On the other hand, at the downstream end of the flow path 35, regions 121 and 122 are present to the same extent as in the structure of the second embodiment of FIG. 22(a). In either configuration, it is clear that the amount of bubbles is reduced compared to the solid structure of FIG. 12(a), and it is clear that the effect of suppressing bubbles can be obtained even in a configuration in which only the first structure 36a or only the second structure 36b is provided. [Effects of the second embodiment and its modified examples]

[0065] As described above, the fluid sensor 1B according to the second embodiment is configured to include a piezoelectric substrate 10 and a sensitive film 21 that is provided on the piezoelectric substrate 10 and has a surface 21S on the side opposite to the piezoelectric substrate 10, and that reacts with a target substance. In addition, the fluid sensor 1B is configured to include a measuring unit 11 that is provided on the piezoelectric substrate 10 and has a comb-shaped electrode 20 and a reflector 22 for propagating an elastic wave at a portion of the surface of the piezoelectric substrate 10 where the piezoelectric substrate 10 and the surface 21S overlap. The piezoelectric substrate 10 further includes a flow path structure 3 that is provided on the piezoelectric substrate 10 and has a surface 21S, a ceiling portion 31c facing the surface 21S, four inner wall portions including sidewall portions 31s surrounding the sides, and first openings (inlet ports 32) for introducing liquid into the flow path 35 and second openings (outlet ports 33) for discharging the liquid in the flow path 35 to the outside, the first openings being provided in the ceiling portion 31c and spaced apart along the longitudinal direction of the flow path 35, the flow path structure 3 forming the flow path for the liquid including the surface 21S, the ceiling portion 31c, and the four inner wall portions. The piezoelectric substrate 10 further includes a first structure 36a and a second structure 36b that extend from the ceiling portion 31c toward the surface 21S at a position between the first opening and the second opening of the flow path structure 3 in the flow path 35 and are spaced apart from the surface 21S and the four inner wall portions.

[0066] Specifically, when viewed from the normal direction of the surface 21S, the first structure 36a is configured to have an open end on the upstream side of the flow path 35, and to have a pair of arm portions 360a and a connecting portion 362a that surround the periphery other than the opening side of the inlet 32. In addition, when viewed from the normal direction of the surface 21S, the second structure 36b is configured to have an open end on the downstream side of the flow path 35, and to have a pair of arm portions 360b and a connecting portion 362b that surround the periphery other than the opening side of the outlet 33.

[0067] With this configuration, the first structure 36a can block a portion of the liquid introduced from the inlet 32 ​​and divert it laterally (in the +Y and −Y directions). Furthermore, the portion of the liquid can be guided toward the upstream end of the flow path 35. Furthermore, the second structure 36b can block a portion of the liquid that has flowed through the first structure 36a and divert it laterally. Furthermore, the portion of the liquid can be guided toward the downstream end of the flow path 35.

[0068] This reduces the flow rate of liquid flowing through the shortest path between the inlet 32 ​​and the outlet 33 compared to an inert structure, and allows the liquid to be efficiently distributed to the area outside the shortest path by diverting the liquid laterally. This reduces the unevenness of the liquid flow rate between the shortest path and the area outside it, thereby suppressing the generation of bubbles due to the supply of liquid into the flow path 35. Furthermore, since the liquid can flow toward both the upstream and downstream ends of the flow path 35, the generation of bubbles at both longitudinal ends of the flow path 35 can be more efficiently suppressed. Furthermore, the fluid sensor 1C according to the modified second embodiment is configured to include first and second structures 36Aa and 36Ab instead of the first and second structures 36a and 36b of the fluid sensor 1B.

[0069] Specifically, the first structure 36Aa replaces the connection portion 362a of the fluid sensor 1B with a connection portion 364a, which extends the connection portion 362a downstream (+X direction). The second structure 36Ab replaces the connection portion 362b of the fluid sensor 1B with a connection portion 364b, which extends the connection portion 362b upstream (-X direction). Compared to the configuration of the second embodiment, this configuration stabilizes the flow of liquid branched laterally and the flow of liquid bypassed downward by the extensions of the connection portions 364a and 364b, thereby more efficiently suppressing the generation of bubbles. Furthermore, a fluid sensor 1D according to another modification of the second embodiment is configured such that only the first structure 36a is provided in the fluid sensor 1B according to the second embodiment.

[0070] With this configuration, the first structure 36a can block a portion of the liquid introduced through the inlet 32 ​​and divert it laterally. Furthermore, a portion of the liquid can be guided toward the end of the flow path 35 on the inlet 32 ​​side. This reduces the flow rate of the liquid flowing along the shortest path between the inlet 32 ​​and the outlet 33 compared to an inert structure. Additionally, the liquid diverted laterally can efficiently distribute the liquid to the area outside the shortest path, thereby suppressing the generation of air bubbles in the space caused by the supply of liquid into the flow path 35. Furthermore, a flow of liquid can be formed toward the end of the flow path 35 on the inlet 32 ​​side, thereby suppressing the generation of air bubbles at the end of the flow path 35 on the inlet 32 ​​side. A fluid sensor 1E according to another modification of the second embodiment is configured such that only the second structure 36b is provided in the fluid sensor 1B according to the second embodiment.

[0071] With this configuration, the second structure 36b can block a portion of the liquid introduced from the inlet 32 ​​and flowing toward the outlet 33 and divert it laterally (in the +Y and −Y directions). Furthermore, a portion of the liquid can be guided toward the end of the flow path 35 on the outlet 33 side. As a result, compared to an inorganic structure, it is possible to suppress the generation of bubbles at the end of the flow path 35 on the outlet 33 side.

[0072] Furthermore, when detecting a target substance in a liquid using the fluid sensor 1B, 1C, 1D, or 1E according to the second embodiment and its modifications, the detection device 100 according to the first embodiment and its modifications can detect the target substance in an environment with less noise due to air bubbles than conventional methods. As a result, the target substance can be detected more accurately than conventional methods. [Third Embodiment] Next, a third embodiment of the present invention will be described. FIG. 26 is a diagram illustrating the third embodiment. [Configuration] The third embodiment differs from the first and second embodiments and their modifications in that it includes an inlet 32A and an outlet 33A instead of the inlet 32 ​​and outlet 33 of the first and second embodiments and their modifications. Below, the same components as those described in the first and second embodiments and their modifications are denoted by the same reference numerals and will not be described again as appropriate. Differences will be described in detail. FIG. 26(a) is a partial plan view showing the schematic configuration of a fluid sensor 1K according to the third embodiment, and FIG. 26(b) is a side view showing the shapes of the inlet 32A and outlet 33A. In the following description, the sidewall portions on the long sides of the inner wall portion 31, that is, the sidewall portions on the +Y direction side and the −Y direction side, will be referred to as long sidewall portions 31LS, and the sidewall portions on the short sides, that is, the sidewall portions on the +X direction side and the −X direction side, will be referred to as short sidewall portions 31SS. As shown in FIG. 26( a), a fluid sensor 1K according to the third embodiment includes a flow path structure 3K instead of the flow path structure 3 in the fluid sensor 1 of the first embodiment. The flow path structure 3K includes a main body 30K instead of the main body 30 of the first embodiment. The main body 30K includes an inlet 32A and an outlet 33A, respectively, provided in the sidewall portion on the +Y direction side, instead of the inlet 32 ​​and the outlet 33 of the first embodiment.

[0073] The inlet 32A includes a cylindrical first pipe 32Aa extending from the main body 30K in the +Y direction and a cylindrical second pipe 32Ab bending and extending continuously in the +Z direction from the +Y direction end of the first pipe 32Aa. That is, as shown in FIG. 26(b), the inlet 32A has a substantially L-shaped bent shape when viewed from the X direction. The first pipe 32Aa and the second pipe 32Ab are in communication. The second pipe 32Ab has an opening 32Ac that opens toward the +Z direction.

[0074] Meanwhile, a through-hole 30h1 communicating with the flow path 35 is provided at the end of the +X direction side wall portion on the +Y direction side of the main body 30K, at a position overlapping with the long side wall portion 31LS in the Y direction. The end of the -Y direction side of the first pipe portion 32Aa is connected to the through-hole 30h1, and the inlet 32A and the flow path 35 communicate with each other via the through-hole 30h1.

[0075] The outlet 33A includes a cylindrical third pipe 33Aa extending from the main body 30K in the +Y direction and a fourth pipe 33Ab bending in the +Z direction from the +Y-direction end of the third pipe 33Aa and continuing to extend. That is, as shown in FIG. 26(b), the outlet 33A has a substantially L-shaped bent shape when viewed from the X direction. The third pipe 33Aa and the fourth pipe 33Ab are in communication. The fourth pipe 33Ab has an opening 33Ac that opens toward the +Z direction.

[0076] Meanwhile, a through-hole 30h2 communicating with the flow path 35 is provided at the −X-direction end of the side wall portion on the +Y-direction side of the main body 30K, at a position overlapping with the long side wall portion 31LS in the Y direction. The −Y-direction end of the third pipe portion 33Aa is connected to the through-hole 30h2, and the outlet 33A and the flow path 35 communicate with each other via the through-hole 30h2.

[0077] Although the inlet 32A and the outlet 33A are configured as L-shaped pipes, they are not limited to this configuration and may be configured as straight pipes or as through-holes (i.e., through-holes 30h1 and 30h2) that penetrate the side wall of the main body 30K. A straight pipe is a pipe portion that extends in the +Y direction. In this case, an opening is formed at the +Y end of the straight pipe. Furthermore, although the shape of the pipe is cylindrical, it is not limited to this and may be other shapes such as a square pipe.

[0078] Furthermore, the fluid sensor 1K has a configuration in which the first structure 34a and the second structure 34b are disposed at the end on the +Y direction side compared to the fluid sensor 1 of the first embodiment. That is, the first structure 34a and the second structure 34b are disposed at a position closer to the long side wall portion 31LS on the +Y direction side. This is to position the first structure 34a and the second structure 34b on the shortest path between the inlet 32A and the outlet 33A. [Effects of the Third Embodiment]

[0079] With the configuration described above, liquid introduced through the opening 32Ac of the inlet 32A passes through the second pipe portion 32Ab and the first pipe portion 32Aa, and then through the through-hole 30h1 and flows into the flow path 35. That is, the liquid flows into the flow path 35 from the long side wall portion 31LS on the +Y direction side. A portion of the liquid that has flowed in flows toward the long side wall portion 31LS on the −Y direction side. The other portion is detoured laterally by the first structure 34a toward the outlet 33A, and flows around to the underside of the first structure 34a toward the outlet 33. Some of the flowing liquid accumulates in the groove formed between the first structure 34b and the second structure 34b, but the second structure 34b allows the majority of the liquid to continue its flow, flowing laterally through the lateral sides of the second structure 34b and below the second structure 34b. The liquid that has flowed into the through hole 30h2 passes through the through hole 30h2, then passes through the fourth pipe portion 33Ab and the third pipe portion 33Aa of the outlet 33A, and is discharged to the outside from the opening 33Ac. That is, the liquid that has flowed through the flow path 35 is discharged to the outside from the long side wall portion 31LS on the +Y direction side.

[0080] This reduces the flow rate of liquid flowing through the shortest path compared to when the first and second structures 34a and 34b are not present (i.e., when the structure is incomplete). Furthermore, because the liquid flows in a lateral detour, it can be efficiently directed to the area outside the shortest path. That is, compared to when the structure is incomplete, it is possible to reduce the bias in the flow rate of liquid between the shortest path and the area outside it. Furthermore, liquid is introduced and discharged from the long side wall 31LS on the +Y direction side and from the ends of the flow path 35 on the −X direction and +X direction. This allows liquid to flow along the short side wall 31SS on the −X direction and +X direction sides of the flow path 35. Therefore, compared to the first embodiment, in which the inlet and outlet are provided at the top of the main body 30, it is possible to suppress the generation of bubbles at the ends of the flow path 35 on the −X direction and +X direction. [Modifications of the Third Embodiment] Next, first to fourth modifications of the third embodiment of the present invention will be described. FIGS. 27 and 28 are diagrams showing first to fourth modifications of the third embodiment. [First Modification] [Configuration] The first modification of the third embodiment differs from the third embodiment in the positions at which the first structure 36a and the second structure 36b are provided. Hereinafter, the same components as those described in the third embodiment will be denoted by the same reference numerals, and descriptions thereof will be omitted as appropriate, and differences will be described in detail. Fig. 27(a) is a partial plan view showing the schematic configuration of a fluid sensor 1L according to a first modification of the third embodiment.

[0081] As shown in Fig. 27(a), a fluid sensor 1L according to the first modification includes a flow path structure 3L instead of the flow path structure 3K in the fluid sensor 1K of the third embodiment. The flow path structure 3L includes a main body 30L instead of the main body 30K of the third embodiment. The main body 30L is the same as the main body 30K of the third embodiment, except that the positions where the first structure 34a and the second structure 34b are provided are the center position in the Y direction of the main body 30L. [Effects of the first modification]

[0082] With the configuration described above, the fluid sensor 1L has the first structures 34a and second structures 34b formed near the shortest path. Therefore, compared to the configuration of the third embodiment, in which the structures are formed along the shortest path, the bubble suppression effect throughout the flow path is slightly reduced, but still sufficient. In particular, compared to the configuration of the first embodiment, bubble generation at the −X and +X ends of the flow path 35 can be suppressed more effectively. [Second Modification] [Configuration] The second modification of the third embodiment differs from the first modification of the third embodiment in the positions of the inlet 32A and outlet 33A. Below, the same components as those described in the first modification are denoted by the same reference numerals, and their descriptions are omitted where appropriate. Differences will be described in detail. Figure 27(b) is a partial plan view showing the schematic configuration of a fluid sensor 1M according to the second modification of the third embodiment.

[0083] As shown in FIG. 27( b), a fluid sensor 1M according to the second modification includes a flow path structure 3M instead of the flow path structure 3L of the fluid sensor 1L of the first modification. The flow path structure 3M includes a main body 30M instead of the main body 30L of the third embodiment. The main body 30M has the same configuration as the main body 30L of the first modification, except that the through holes 30h1 and 30h2, the inlet 32A, and the outlet 33A are provided in the side wall portion on the −X direction side and the side wall portion on the +X direction side of the main body 30M. Specifically, the through hole 30h1 is provided in the side wall portion on the −X direction side of the main body 30M, at a position overlapping the short side wall portion 31SS in the X direction. Similarly, the through hole 30h2 is provided in the side wall portion on the +X direction side of the main body 30M, at a position overlapping the short side wall portion 31SS in the X direction. When the inlet 32A is rotated 90 degrees counterclockwise from the orientation of the first modified example, the end of the first pipe section 32Aa on the +X direction side is connected to the through-hole 30h1. As a result, the inlet 32A and the flow path 35 communicate with each other via the through-hole 30h1. On the other hand, when the outlet 33A is rotated 90 degrees clockwise from the orientation of the first modified example, the end of the third pipe section 33Aa on the -X direction side is connected to the through-hole 30h2. As a result, the outlet 33A and the flow path 35 communicate with each other via the through-hole 30h2. [Effects of the second modified example]

[0084] With the configuration described above, in the fluid sensor 1M, liquid flows into the flow path 35 from the short side wall 31SS on the -X direction side via the inlet 32A. The flowing liquid is diverted to both sides in the Y direction by the first structure 34a and flows toward the outlet 33A, and then flows around to the underside of the first structure 34a and toward the outlet 33A. The liquid that flows into the outlet 33A side passes through the through-hole 30h2, then passes through the fourth pipe 33Ab and the third pipe 33Aa, and is discharged to the outside through the opening 33Ac. In other words, the liquid is discharged to the outside from the short side wall 31SS on the +X direction side.

[0085] This reduces the flow rate of liquid flowing through the shortest path compared to a non-body structure. Furthermore, because the liquid flows in a lateral detour, it can be efficiently directed to the area outside the shortest path. That is, compared to a non-body structure, it reduces the bias in the flow rate of liquid between the shortest path and the area outside it. Furthermore, liquid is introduced from the end of the short side wall 31SS on the −X direction side and discharged from the end of the short side wall 31SS on the +X direction side. In the first embodiment, the inlet 32 ​​and outlet 33 were provided on the ceiling of the fluid sensor 1 and extended in the −Z direction. Because the momentum of the liquid moving in the −Z direction caused some of the liquid to flow to the bottom of the fluid sensor 1K, reducing the flow rate of the liquid through the shortest path accordingly. In contrast, in the fluid sensor 1M, due to the positions of the inlet 32A and outlet 33A, the liquid introduced through the inlet 32A flows through the shortest path with force, resulting in a greater flow rate of the liquid through the shortest path than in the first embodiment. This makes it possible to suppress the generation of bubbles at the ends of the flow path 35 on the -X direction side and the +X direction side, compared to a configuration in which the inlet and outlet are provided at the top of the main body 30 as in the first embodiment. [Third Modification] [Configuration] The third modification of the third embodiment differs from the second modification in that it includes an inlet 32 ​​instead of the inlet 32A. Below, the same components as those described in the second modification are denoted by the same reference numerals and their description will be omitted as appropriate, and differences will be described in detail. Figure 28(a) is a partial plan view showing the schematic configuration of a fluid sensor 1N according to the third modification of the third embodiment.

[0086] As shown in FIG. 28A , the fluid sensor 1N according to the third modification includes a flow path structure 3N instead of the flow path structure 3M of the fluid sensor 1M according to the second modification. The flow path structure 3N includes a main body 30N instead of the main body 30M according to the second modification. The main body 30N has the through-hole 30h1 removed from the main body 30M according to the second modification, and includes an inlet 32 ​​instead of the inlet 32A. The inlet 32 ​​is formed in the same position as in the fluid sensor 1 according to the first embodiment. That is, the fluid sensor 1N is configured such that, instead of the outlet 33 of the fluid sensor 1 according to the first embodiment, an outlet 33A is provided in the side wall portion on the +X direction side. [Effects of the Third Modification] With the configuration of the fluid sensor 1N, liquid is discharged from the end of the short side wall portion 31SS on the +X direction side, and liquid can be guided to the end of the flow path 35 on the +X direction side. This can suppress the generation of bubbles at the end of the flow path 35 on the +X direction side. This is based on the mechanism described in the second modified example of the third embodiment. That is, compared to the first embodiment in which both the inlet 32 ​​and the outlet 33 are provided in the ceiling, the outlet 33A extends in the +X direction, which increases the momentum of the liquid toward the outlet 33A and increases the flow rate of the liquid through the shortest path. As a result, air bubbles can be suppressed. While the degree of bubble suppression is not sufficient compared to the second modified example of the third embodiment, it is greater than that of the first embodiment. Note that in the third modified example, the inlet 32 ​​is provided in the upper part of the main body 30N and the outlet 33A is provided in the sidewall portion on the +X direction side of the main body 30N. However, this configuration is not limiting, and the positions of the inlet and outlet may be reversed. In this case, the inlet 32A is provided in the sidewall portion on the −X direction side of the main body 30N, and the outlet 33 is provided in the upper part on the +X direction side of the main body 30N. As a result, because the inlet 32A extends in the −X direction, the momentum of the liquid toward the shortest path increases and the flow rate of the liquid through the shortest path increases. As a result, air bubbles can be suppressed. [Fourth Modification] [Configuration] The fourth modification of the third embodiment differs from the third modification in that an outlet 33A is provided in a side wall portion in the longitudinal direction of the main body. Hereinafter, the same components as those described in the third modification will be assigned the same reference numerals and their description will be omitted as appropriate, and different parts will be described in detail.FIG. 28B is a partial plan view showing a schematic configuration of a fluid sensor 1P according to a fourth modified example of the third embodiment.

[0087] 28(b), a fluid sensor 1P according to the fourth modification includes a flow path structure 3P instead of the flow path structure 3N in the fluid sensor 1N of the third modification. The flow path structure 3P includes a main body 30P instead of the main body 30N in the flow path structure 3N of the third modification. The main body 30P has a configuration in which the outlet 33A in the main body 30N of the third modification is provided in the side wall portion on the −Y direction side of the main body 30 and at the end on the +X direction side.

[0088] Specifically, the through-hole 30h2 is provided at the end of the +X direction of the side wall portion on the -Y direction side of the main body 30, and at a position overlapping with the long side wall portion 31LS in the Y direction. When the outlet 33A is in an orientation rotated 90 degrees clockwise from the orientation of the third modified example, the end of the third pipe portion 33Aa on the +Y direction side is connected to the through-hole 30h2. [Effects of the fourth modified example]

[0089] With the above-described configuration, the fluid sensor 1P discharges liquid from the outlet 33A at the end on the +X direction side and on the long side wall 31LS on the -Y direction side, resulting in a flow of liquid along the short side wall 31SS on the +X direction side of the flow path 35. Therefore, compared to the configuration in which the outlet is provided at the top of the main body 30 as in the first embodiment, the generation of air bubbles at the end on the +X direction side of the flow path 35 can be suppressed. In this case, as in the third embodiment and other modifications, the flow rate of liquid passing through the shortest path or near the shortest path is high, thereby suppressing air bubbles. Note that in the third modification, the inlet is provided at the top of the main body 30P and the outlet is provided in the side wall on the -Y direction side of the main body 30P. However, this configuration is not limited to this, and the positions of the inlet and outlet may be reversed. In this case, the outlet 33 is provided at the top of the main body 30P on the +X direction side, and the inlet 32A is provided in the side wall on the -X direction and -Y direction side of the main body 30P.

[0090] Furthermore, the fluid sensor 1P may be configured to have the inlet 32A and through-hole 30h1 of the third embodiment instead of the inlet 32. With this configuration, it is possible to generate a flow of liquid along the short side wall portion 31SS even on the −X direction side of the flow path 35. As a result, it is possible to suppress the generation of bubbles at the end of the flow path 35 on the −X direction side. (Other Modifications)

[0091] In the above-described embodiments and their modifications, the various structures are integrally formed with the ceiling portion 31c of the inner wall portion 31 of the flow path structure, but this is not a limitation. For example, the structures may be attached to the ceiling portion 31c as separate bodies, or may be provided as separate bodies from the flow path structure. In the above-described first embodiment and its modifications, the first and second structures 34a and 34b and the structure 34A have rectangular planar shapes, but this is not a limitation and other shapes may be used.

[0092] Furthermore, in the first embodiment and its modified examples described above, the widths of the first and second structures 34a and 34b and structure 34A in the Y direction are configured to be the same as or approximately the same as the diameter of the inlet 32, but this configuration is not limited to this. For example, the widths may be narrower or wider than the diameter of the inlet 32 ​​as long as the bubble suppression effect is maintained. Similarly, the lengths and positions of the first and second structures 34a and 34b and structure 34A in the X direction may also be configured to be other lengths and positions as long as the bubble suppression effect is maintained.

[0093] In the above-described embodiments and their modifications, the flow path structure 3 is configured to cover a portion of the surface 21S of the measurement unit 11. However, this configuration is not limited thereto. For example, the flow path structure 3 may be configured to cover the measurement unit 11, including the pair of reflectors 22 on the piezoelectric substrate 10. In this configuration, the flow path structure 3 covers the pair of reflectors 22 in addition to the comb-shaped electrode 20, so that the pair of reflectors 22 are also present within the flow path 35. Therefore, it is desirable to cover the entire pair of reflectors 22 with a protective film to prevent electrical conduction with the liquid. In this configuration, the surface of the protective film covering the pair of reflectors 22 and the surface including the surface 21S correspond to the first inner wall. In the above-described embodiments and their modifications, the various fluid sensors are configured as a resonance type using surface acoustic waves. However, this configuration is not limited thereto, and other configurations, such as a delay type or a resonance type using bulk acoustic waves, may also be used. FIG. 24 is a plan view showing a schematic configuration example of a delay type fluid sensor 1F according to a modification of the present invention. As shown in Figure 24, the fluid sensor 1F is configured such that, in the fluid sensor 1 of the first embodiment described above, instead of the measurement substrate 2 having a resonance type configuration, a measurement substrate 2A having a delay type configuration is provided.

[0094] The measurement substrate 2A includes a measurement section 11A instead of the measurement section 11 of the measurement substrate 2, and the measurement section 11A is configured by removing the comb electrode 20 from the measurement section 11, and by replacing the reflector 22 on the inlet 32 ​​side of the fluid sensor 1 with a first comb electrode 23, and replacing the reflector 22 on the outlet 33 side with a second comb electrode 24. The first comb electrode 23 and the second comb electrode 24 have the same basic structure as the comb electrode 20 of the first embodiment, and each is composed of a pair of comb electrodes.

[0095] The first comb electrode 23 is an electrode on the transmitting side of the surface acoustic wave SAW, and the second comb electrode 24 is an electrode on the receiving side. That is, in the transmitter 101 of the detection device 100 according to the first embodiment, a surface acoustic wave SAW generated by applying a high-frequency voltage to the first comb electrode 23 travels in the X direction (the direction of the arrow in FIG. 24 ) and reaches the second comb electrode 24. That is, the surface acoustic wave SAW transmitted by the first comb electrode 23 crosses the portion of the surface of the piezoelectric substrate 10 that overlaps with the surface 21S and reaches the second comb electrode 24. The second comb electrode 24 converts the received surface acoustic wave SAW into a signal and outputs it to the receiver 102. Therefore, the measuring device 103 measures the phase difference between the high-frequency signal transmitted by the transmitter 101 and the high-frequency signal received by the receiver 102, and the detector 104 can detect a target substance in the liquid based on the measured phase difference.

[0096] In the example shown in FIG. 24 , the flow path structure 3 does not cover the first and second comb electrodes 23 and 24. However, this configuration is not limited thereto, and the first and second comb electrodes 23 and 24 may also be covered. In this case, it is desirable to cover the entire first and second comb electrodes 23 and 24 with a protective film. FIG. 25 is a cross-sectional view showing a schematic configuration example of a resonant fluid sensor 1H using bulk acoustic waves according to a modified example of the present invention. As shown in FIG. 25 , the fluid sensor 1H is configured such that, instead of the measurement substrate 2 having a resonant configuration using surface acoustic waves in the fluid sensor 1 of the first embodiment, a measurement substrate 2B having a resonant configuration using bulk acoustic waves is provided. The measurement substrate 2B has a configuration in which an acoustic reflection film 13, a lower electrode 14, a piezoelectric layer 15, an upper electrode 16, a protective film 17, and a sensitive film 21 are stacked on a support substrate 12. That is, the surface 21S of the sensitive film 21 is provided at a position overlapping the lower electrode 14 and the upper electrode 16 in the stacking direction. The planar shape of the support substrate 12 is a rectangle with its long sides extending in the X direction.

[0097] The acoustic reflection film 13 is configured by alternately laminating films with low acoustic impedance and films with high acoustic impedance. By making the thickness of each film approximately ¼ of the wavelength of the acoustic wave, the acoustic wave is reflected by the acoustic reflection film 13. Here, the bottom layer of the acoustic reflection film 13 is a high-impedance film, and the top layer is a low-impedance film. The high-impedance film can be configured from an oxide layer containing one or more elements selected from the group consisting of niobium (Nb), tantalum (Ta), tungsten (W), and molybdenum (Mo). The low-impedance film can be configured from, for example, silicon dioxide (SiO ２ The piezoelectric element 14 may be composed of an oxide layer containing a low-impedance oxide element such as SiO 2 . The planar shape of the lower electrode 14 and the upper electrode 16 is a rectangle with the longer side in the X direction. The lower electrode 14 and the upper electrode 16 correspond to a first electrode and a second electrode, respectively. The lower electrode 14 has a predetermined width and extends continuously in the +X direction from the end of the adhesive member 40 on the −X direction side to the end of the sensitive film 21 on the +X direction side. The predetermined width is, for example, the same width as the sensitive film 21. The upper electrode 16 has a predetermined width and extends continuously in the −X direction from the end of the adhesive member 40 on the +X direction side to the end of the sensitive film 21 on the −X direction side. The predetermined width is, for example, the same width as the sensitive film 21. The region where the piezoelectric layer 15, the lower electrode 14, and the upper electrode 16 overlap is a resonance region. The protective film 17 protects the upper electrode 16 and the piezoelectric layer 15 from moisture and the like.

[0098] With this configuration, in the fluid sensor 1H, when a high-frequency voltage is applied to the lower electrode 14 and the upper electrode 16 by the transmitter 101 of the detection device 100, bulk acoustic waves, such as those in a thickness-extensional vibration mode or a thickness-shear vibration mode, resonate within the resonance region. In other words, the measurement substrate 2B of the fluid sensor 1H constitutes a bulk acoustic wave resonator. The measuring device 103 of the detection device 100 measures frequency information of the bulk acoustic waves, and the detector 104 can detect a target substance in the liquid based on the measured frequency information.

[0099] Instead of the acoustic reflection film 13, a laminate including the lower electrode 14 may be formed on the support substrate 12, and then a recess may be formed in the support substrate 12 to form a void, or a sacrificial layer may be formed between the lower electrode 14 and the support substrate 12 and removed by etching to form a void. These structures form a film bulk acoustic resonator (FBAR).

[0100] DESCRIPTION OF SYMBOLS 1, 1A to 1H, 1K to 1N, 1P... fluid sensor, 3, 3A to 3D... flow path structure, 11... measurement section, 12... support substrate, 13... acoustic reflection film, 14... lower electrode, 15... piezoelectric film, 16... upper electrode, 17... protective film, 20... comb-shaped electrode, 21... sensitive film, 21S... surface, 22... reflector, 23... first comb-shaped electrode, 24... second comb-shaped electrode, 30... main body, 30B... bottom surface, 31... inner wall portion, 31c...ceiling portion, 31S...side wall portion, 31LS...long side wall portion, 31SS...short side wall portion, 32, 32A...inlet, 33, 33A...outlet, 34A...structure, 34a, 36a, 36Aa...first structure, 34b, 36b, 36Ab...second structure, 35...flow path, 35s...bypass path, 100...detection device, 101...transmitter, 102...receiver, 103...measuring device, 104...detector

Claims

a first inner wall including the surface; a second inner wall provided on the piezoelectric body and facing the first inner wall, a plurality of third inner walls surrounding the sides, a first opening for introducing liquid and a second opening for discharging liquid to the outside, the first inner wall, the second inner wall, and the plurality of third inner walls forming a flow path for liquid; and a structure provided at a position between the first opening and the second opening of the second inner wall, extending from the second inner wall side to the first inner wall side, and provided at a distance from the first inner wall and the plurality of third inner walls.

2. A sensor according to claim 1, wherein the structure includes a first structure disposed on the upstream side of the flow path and a second structure disposed on the downstream side of the flow path.

3. A sensor as claimed in claim 1, wherein the structure is composed of at least one of a first structure arranged to surround the first opening and having an opening on the upstream side of the flow path when viewed from the normal direction to the surface, and a second structure arranged to surround the second opening and having an opening on the downstream side of the flow path.

4. A sensor as claimed in claim 3, wherein the first structure or the second structure is configured such that the end on the second opening side extends towards the second opening side, or the end on the first opening side extends towards the first opening side.

5. A sensor according to claim 1, wherein the structure extends continuously from the upstream side to the downstream side of the flow path.

6. A sensor according to claim 1, wherein the structure has a width at least equal to or greater than the widths of the first opening and the second opening.

7. A sensor according to claim 1, wherein the distance between the two third inner walls opposing each other in the width direction of the flow path and the structure is substantially constant from the upstream side to the downstream side.

8. A sensor according to claim 1, wherein the distances between both side surfaces of the structure opposing each other in the width direction of the flow path and the two third inner walls opposing each other in the width direction of the flow path are approximately equal.

9. The sensor according to claim 1, wherein the flow path is closed except for the first opening and the second opening by the first inner wall, the second inner wall and the plurality of third inner walls.

10. A sensor as claimed in claim 1, wherein the pair of electrodes is a pair of comb-shaped electrodes provided on the underside of the surface of the piezoelectric body, and the sensor has reflectors provided at opposing positions in the longitudinal direction of the flow path, sandwiching the pair of comb-shaped electrodes.

11. The sensor according to claim 1, wherein the pair of electrodes is a pair of first comb electrodes for transmitting the elastic waves and a pair of second comb electrodes for receiving the elastic waves, which face each other in the longitudinal direction of the flow path, sandwiching the surface therebetween.

12. A sensor as claimed in claim 1, wherein the pair of electrodes is a first electrode and a second electrode stacked with the piezoelectric body sandwiched therebetween, and the sensitive film is provided at a position where its surface overlaps with the first electrode and the second electrode in the stacking direction.

13. A detection device comprising: a transmitter that transmits a high-frequency signal for generating the elastic wave to the pair of electrodes of a sensor described in any one of claims 1 to 12; a measuring instrument that measures information about the elastic wave propagated to at least the portion of the piezoelectric body where the piezoelectric body overlaps with the surface; and a detector that detects the target substance based on the information measured by the measuring instrument.

14. A sensor comprising: a piezoelectric body; a sensitive membrane provided on the piezoelectric body, having a surface opposite to the piezoelectric body, and reacting with a target substance; a pair of electrodes provided on the piezoelectric body, propagating elastic waves in at least a region of the piezoelectric body where the piezoelectric body and the surface overlap; a first inner wall including the surface; a second inner wall provided on the piezoelectric body and facing the first inner wall, and a plurality of third inner walls surrounding the sides, a flow path structure having a first opening for introducing liquid and a second opening for discharging liquid to the outside, the first inner wall, the second inner wall, and the plurality of third inner walls being provided apart from each other on the second inner wall, the flow path structure forming a flow path for liquid including the first inner wall, the second inner wall, and the plurality of third inner walls; and a structure provided in a position facing the surface in the flow path with a predetermined interval therebetween, for blocking a portion of the liquid introduced from the first opening and flowing toward the second opening, and for diverting the liquid in both directions in the width direction of the flow path.

15. A flow path structure comprising: a piezoelectric body; a sensitive membrane provided on the piezoelectric body, having a surface opposite to the piezoelectric body, and reacting with a target substance; a pair of electrodes provided on the piezoelectric body for propagating elastic waves at least in a region of the piezoelectric body where the piezoelectric body and the surface overlap; a first inner wall including the surface; a second inner wall provided on the piezoelectric body and facing the first inner wall, a plurality of third inner walls surrounding the sides, a first opening for introducing a liquid and a second opening for discharging the liquid to the outside, the first opening and the second opening being provided apart from each other on either the second inner wall or the third inner wall, or either the first opening or the second opening being provided on the second inner wall and the one of the first opening and the second opening not provided on the second inner wall being provided on the third inner wall; and a structure extending from the second inner wall side to the first inner wall side and spaced apart from the first inner wall at a position between the first opening and the second opening.

16. The sensor according to claim 15, wherein the first opening or the second opening is provided in the third inner wall, and the structure is provided away from the first inner wall and the plurality of third inner walls.

17. A flow path structure comprising: a piezoelectric body; a sensitive membrane provided on the piezoelectric body, having a surface opposite to the piezoelectric body, and reacting with a target substance; a pair of electrodes provided on the piezoelectric body for propagating elastic waves to at least a region in the piezoelectric body where the piezoelectric body and the surface overlap; a first inner wall including the surface; a second inner wall provided on the piezoelectric body and facing the first inner wall, a plurality of third inner walls surrounding the sides, a first opening for introducing a liquid and a second opening for discharging the liquid to the outside, the first opening and the second opening being provided apart from each other on either the second inner wall or the third inner wall, or either the first opening or the second opening being provided on the second inner wall and the one of the first opening and the second opening not provided on the second inner wall being provided on the third inner wall; and a structure provided at a position between the first opening and the second opening, extending from the second inner wall side to the first inner wall side, spaced apart from the first inner wall, and provided at a position passing through a line segment having a shortest distance between the first opening at one end and the second opening at the other end.

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