Channel structure, microchannel device, and wearable device

Abstract

The purpose of the present invention is to provide a technique for reducing effects of air bubbles generated from a liquid in a microchannel device.　One channel structure according to the present invention forms a part of a microchannel device. The channel structure is characterized by comprising: an inflow channel through which a liquid flows; a liquid accumulation part connected to the inflow channel; a gas accumulation part provided vertically upward of the liquid accumulation part; and an outflow channel connected to the liquid accumulation part.

Description

Channel structure, microchannel device, and wearable device

[0001] The present invention relates to a channel structure, a microchannel device, and a wearable device.

[0002] Microfluidic devices have micrometer-sized channels and are used to process or manipulate liquids within the channels. Applications of microfluidic devices include DNA analysis and cell analysis. Compared to conventional devices, microfluidic devices have the advantage of being able to use smaller amounts of chemicals, samples, and reagents for testing and analysis. In recent years, technological developments have been progressing regarding the manufacturing of microfluidic devices and testing methods.

[0003] In testing and analysis using microchannel devices, processes are performed to manipulate the flow of liquid by branching, expanding, or contracting the flow channel, or to heat the liquid using a heater or the like, and the reactions to these processes are sensed. During the process, gas dissolved in the liquid may be generated as bubbles. Bubbles can have a significant impact on measurement results, for example, by remaining in the flow channel and obstructing the flow, or by adhering to the sensing part and interfering with normal testing. Examples of technologies for suppressing the effects of bubbles in such microchannels include the following Patent Documents 1 and 2.

[0004] Patent Document 1 aims to reduce the risk of air bubbles being mixed into a liquid when the liquid flows through the channel in a channel device, and discloses the following content regarding the channel device: "One embodiment of the channel device according to the present invention includes a channel, and a first space and a second space located in the channel. The channel has a side surface along the direction of the liquid flow. The second space is connected to the first space. The upper end of the second space is located at a different height from the upper end of the first space. At least a portion of the first space is located between the side surface of the channel and at least a portion of the outer periphery of the second space." Furthermore, Patent Document 2 aims to provide a microchannel chip that can remove air bubbles generated in a microchannel and can prevent adhesive components from eluting into the channel, thereby suppressing reaction inhibition of the solution in the channel, and a method for manufacturing the same, and discloses the following content regarding the microchannel chip and the method for manufacturing the microchannel chip. "The microchannel chip 1 comprises a substrate 10, a partition layer 11 that forms a channel on the substrate 10, and an upper cover layer 12 that is formed on the surface of the partition layer 11 opposite the substrate 10 and serves as a lid for the channel section 3, and the upper cover layer 12 is provided with a bubble removal section 7 that is part of the upper cover layer 12 and removes bubbles that occur in the channel section 3, and no adhesive layer is provided between the partition layer 11 and the upper cover layer 12."

[0005] International Publication No. 2021 / 107003 Japanese Patent Application Laid-Open No. 2023-18620

[0006] Patent Document 1 considers preventing bubbles from being mixed into the liquid flowing through the channel, but does not consider bubbles that are generated within the channel. Furthermore, Patent Document 2 describes a bubble removal unit that is applicable to microchannels with a specific structure, and leaves room for further consideration for microchannels with other structures. Therefore, an object of the present invention is to provide a technology that suppresses the effects of bubbles that are generated from the liquid in a microchannel device.

[0007] In order to solve the above problems, one representative flow channel structure of the present invention is a flow channel structure that constitutes part of a microchannel device, characterized in that the flow channel structure comprises an inlet flow channel through which a liquid flows, a liquid reservoir connected to the inlet flow channel, a gas reservoir provided vertically upward from the liquid reservoir, and an outlet flow channel connected to the liquid reservoir.

[0008] According to the present invention, it is possible to suppress the effects of bubbles generated from the liquid in the microchannel device. Problems, configurations, and effects other than those described above will become apparent from the description of the following embodiments of the invention.

[0009] FIG. 1 is a diagram schematically showing a flow path structure of Example 1. FIG. 2 is a diagram showing a control process for an inlet valve and an outlet valve. FIG. 3 is a diagram schematically showing forces acting on bubbles. FIG. 4 is a flowchart showing the operation of an inlet valve and an outlet valve. FIG. 5 is a diagram schematically showing a flow path structure of Example 2. FIG. 6 is a flowchart showing the operation of the flow path structure of Example 2. FIG. 7 is a diagram schematically showing a wearable device of Example 3.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to this embodiment. In addition, in the description of the drawings, the same parts are designated by the same reference numerals.

[0011] Furthermore, the position, size, shape, and range of each component shown in the drawings may not represent the actual position, size, shape, and range in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the position, size, shape, and range disclosed in the drawings. Furthermore, in this disclosure, "upper" refers to the vertically upward direction when a plate-like member or layer is placed horizontally. Furthermore, "upper" and its opposite, "lower," are sometimes referred to as the "positive z-axis direction" and the "negative z-axis direction." Furthermore, the distance in the z-axis direction is sometimes referred to as the "height," and the distance in the x-axis direction or the y-axis direction is sometimes referred to as the "width." Furthermore, the portion in the negative z-axis direction that is parallel to the z-axis direction is sometimes referred to as the "bottom." Furthermore, "planar shape" and "planar view" refer to the shape of a surface or layer viewed from above. Furthermore, "cross-sectional shape" and "cross-sectional view" refer to the shape of a plate-like member or layer viewed horizontally when cut in a specific direction.

[0012] Furthermore, the term "liquid" refers to a liquid reagent, a solvent containing a solute, etc. It is not limited to a liquid only, but also includes a viscous state and a state in which a liquid and a solid are mixed.

[0013] (Causes of bubble generation) The cause of bubble generation in a liquid is that the amount of gas dissolved in the liquid exceeds the saturated solubility. Generally, the saturated solubility varies depending on the type of solution, the type of gas, and the temperature and pressure at which the solution and gas exist.

[0014] When microfluidic devices are used for testing and analysis, for example, a liquid may be heated and its reaction analyzed. As the temperature increases, the saturated solubility of gas generally decreases, causing excess dissolved gas to appear as bubbles.

[0015] When a gas is dissolved in a liquid that exceeds the saturation solubility, it is called supersaturation. In the case of supersaturation, when the liquid is vibrated or stirred, the gas forms bubbles.

[0016] (Example 1) (Channel Structure) First, the channel structure of a microchannel device will be described with reference to Fig. 1. Fig. 1 is a diagram schematically illustrating the channel structure of Example 1, with Fig. 1(a) showing a plan view of the channel structure 1 and Fig. 1(b) showing a cross-sectional view of the channel structure 1. The channel structure 1 constitutes a part of the microchannel device, and includes an inflow channel 10 through which a liquid flows, a liquid reservoir 11 connected to the inflow channel 10, a gas reservoir 12 provided vertically above the liquid reservoir 11, and an outflow channel 13 connected to the liquid reservoir 11. A specific description will be given below.

[0017] 1, the arrow fd indicates the flow direction, and in the example of Fig. 1, the liquid flows from the minus x direction to the plus x direction. Therefore, when devices for performing inspection, analysis, etc. are provided at the end of the flow direction fd, the flow path structure 1 is provided upstream of these devices.

[0018] The flow channel structure 1 can be applied to any microchannel device without being limited by the shape, application, material, etc. of the microchannel device. For example, the flow channel structure 1 of the present disclosure can be applied even when the microchannel device is composed of a first substrate and a second substrate, and the flow channel is composed of a groove in the first substrate and the second substrate attached to the first substrate so as to cover the groove. Furthermore, two or more flow channel structures 1 can be provided in a microchannel device.

[0019] The inflow channel 10 is connected to the upstream side of the liquid reservoir 11 and introduces liquid into the liquid reservoir 11. The liquid reservoir 11 is a space that retains the liquid introduced from the inflow channel 10. The outflow channel 13 is connected to the downstream side of the liquid reservoir 11 and allows the liquid retained in the liquid reservoir 11 to flow out. An inflow valve 14 is provided between the inflow channel 10 and the liquid reservoir 11, and an outflow valve 15 is provided between the liquid reservoir 11 and the outflow channel 13. When the outflow valve 15 is closed, communication between the liquid reservoir 11 and the outflow channel 13 is blocked. When the outflow valve 15 changes from a closed state to an open state, the outflow valve 15 has a structure that opens so that its opening widens from the bottom side of the outflow channel 13. The inflow valve 14 and the outflow valve 15 will be described later.

[0020] In a cross-sectional view perpendicular to the flow direction fd, the reservoir 11 has a larger channel area than the inflow channel 10 and the outflow channel 13. Specifically, as shown in FIG. 1( a), the reservoir 11 has a width (e.g., width W2) larger than the width W1 of the inflow channel 10 and the outflow channel 13, and has an arc-shaped contour with a continuously changing width. Also, as shown in FIG. 1( b), the inflow channel 10, the reservoir 11, and the outflow channel 13 share a common bottom. When this bottom is used as a reference, the height H of the reservoir 11 is approximately the same as or higher than the height h1 of the inflow channel 10, and is higher than the height h2 of the outflow channel 13. Incidentally, when the bottom of the microchannel device is placed horizontally, the liquid level in the outflow channel 13 is lower than the liquid level in the inflow channel 10. In this way, since the flow path area of ​​the liquid reservoir 11 is larger than the flow path area of ​​the inflow flow path 10, it is possible to reduce the flow rate of the liquid when the liquid is introduced into the liquid reservoir 11 from the inflow flow path 10. Furthermore, since the flow area of ​​the liquid reservoir 11 is larger than the flow area of ​​the inflow flow path 10, it is possible to cause the liquid to accumulate in the liquid reservoir 11. Furthermore, since the flow path area of ​​the liquid reservoir 11 is larger than the flow path area of ​​the outflow flow path 13, it is possible to suppress the outflow amount of the liquid accumulated in the liquid reservoir 11 without it flowing out to the outflow flow path 13 all at once.

[0021] The liquid reservoir 11 is disposed between the inlet valve 14 and the outlet valve 15, and has a length D1. In a section from the inlet valve 14 in the positive x-axis direction with a length D2, the liquid reservoir 11 has a connecting flow path 11a having the same shape as the inlet flow path 10. If the liquid were introduced directly from the inlet flow path 10 to the liquid reservoir 11 without providing the connecting flow path 11a, the change in the flow path would be large, causing sudden turbulence in the liquid and potentially generating secondary bubbles. By providing the connecting flow path 11a, a buffer section is formed between the inlet flow path 10 and the liquid reservoir 11, making it possible to suppress the impact on the liquid flow.

[0022] Although the shape of the liquid reservoir 11 has been described above, the present disclosure is not limited thereto. The shape of the liquid reservoir 11 may be any shape as long as it has the function of retaining liquid. Furthermore, since the flow channel structure 1 is incorporated into the flow channels of a microchannel device, the structures of the inflow channel 10 and the outflow channel 13 can also be adapted to suit the structure of the microchannel device. For example, the cross sections of the inflow channel 10 and the outflow channel 13 in a direction perpendicular to the flow direction fd may be rectangular or circular. Alternatively, a shape suitable for the flow channel structure 1 can be selected as appropriate.

[0023] The gas reservoir 12 is provided vertically upward (in the positive z-axis direction) of the liquid reservoir 11 and is a space in which gas can exist. Bubbles generated from the liquid remaining in the liquid reservoir 11 turn into gas and are released from the liquid into the gas reservoir 12. As shown by the angle θ1 in FIG. 1( b), the gas reservoir 12 is configured so that the space narrows toward the flow direction fd. This shape makes it possible to prevent the gas accumulated in the gas reservoir 12 from reentering the outflow flow path 13.

[0024] Although the shape of the gas reservoir 12 has been described above, the present disclosure is not limited thereto. The shape of the gas reservoir 12 may be any shape as long as it functions to retain gas. The gas reservoir 12 retains bubbles or gas generated while the liquid is retained in the liquid reservoir 11. If the liquid penetrates into the gas reservoir 12 while retaining the liquid in the liquid reservoir 11 and the gas reservoir 12 becomes filled with liquid, the function of the gas reservoir 12 may not be fully realized. Furthermore, even if gas is retained in the gas reservoir 12, if the pressure in the gas reservoir 12 increases, the gas in the gas reservoir 12 may dissolve back into the liquid. The shape of the gas reservoir 12 is determined taking into consideration the type of liquid, the flow rate of the liquid, the size of the microchannel device, and the like.

[0025] The flow path structure 1 may also include other components, such as a sensor for measuring the flow velocity of the liquid, a sensor for measuring the flow rate, a drive mechanism for driving the inlet valve 14 and the outlet valve 15, a heating element for heating the liquid, and the like.

[0026] (Effects of the liquid reservoir and gas reservoir) While the liquid is temporarily retained in the liquid reservoir 11, bubbles generated from the liquid rise up in the liquid. As a result, bubbles or liquid containing many bubbles are present on the upper side of the liquid reservoir 11, mainly near the liquid surface, while liquid from which the bubbles have been removed is present on the lower side of the liquid reservoir 11. Furthermore, the bubbles collected on the upper side of the liquid reservoir 11 are held as gas in the gas reservoir 12, and are prevented from dissolving back into the liquid. In this way, the flow path structure 1 can extract the liquid from which the bubbles have been removed and flow it downstream by utilizing the property of bubbles floating up without the application of any external force.

[0027] Furthermore, when electrochemical measurements are performed using a microfluidic device, the presence of air bubbles on the measurement sensor can degrade measurement sensitivity. By providing the liquid reservoir 11 and the gas reservoir 12 as in the present disclosure, the liquid from which the air bubbles have been removed can reach the sensor, thereby suppressing the influence of the air bubbles on the measurement.

[0028] (Control of Inlet and Outlet Valves) Next, control of the inlet valve 14 and the outlet valve 15 will be described with reference to Figures 2 to 4. By controlling the inlet valve 14 and the outlet valve 15 in addition to the liquid reservoir 11 and the gas reservoir 12, it is possible to further suppress the effects of bubbles. The inlet valve 14 and the outlet valve 15 are adjustment valves that can control the flow of liquid, and operating the inlet valve 14 and the outlet valve 15 promotes the guidance of bubbles generated from the liquid to the upper side of the liquid reservoir 11. Note that, for example, solenoid valves can be used as the inlet valve 14 and the outlet valve 15, but the present disclosure is not limited to the case of solenoid valves.

[0029] 2 is a diagram showing the control process of the inlet valve 14 and the outlet valve 15. FIG. ６2 shows the processes performed from the generation of bubbles to their removal, and also shows the process from the generation of bubbles to their removal. Note that in Fig. 2, the dimensions of the components included in the flow path structure 1 are changed for ease of understanding, but the present disclosure is not limited to the embodiment shown in Fig. 2.

[0030] The flow path structure 1 further includes an absorbent member that absorbs gas in the gas reservoir portion 12. FIG. 2 shows an example in which a remover 43 is provided as an absorbent member at the boundary between the liquid reservoir portion 11 and the gas reservoir portion 12. The remover 43 can be selected depending on the type of gas contained in the bubbles. For example, if bubbles 40 containing carbon dioxide are expected to be generated, a remover containing activated carbon can be provided as the remover 43. For example, a film-like absorbent member, such as an absorbent sheet, can be used. The relationship between the generated gas and the absorbent is shown in the following table. While a solid material can generally be used as the absorbent 43, if a liquid absorbent is used, it is possible to hold the liquid absorbent in a hydrophilic and water-absorbent material and then place it within the flow path structure 1. Using a sheet that absorbs VOCs (volatile organic compounds) as the absorbent member also has the advantage of reducing environmental impact.

[0031] In Fig. 2, t = 0 indicates the time when bubbles 40 are generated. The bubble factor section 41 is a location where there is a cause for generating bubbles from the liquid, and indicates a location where bubbles 40 can be generated. Examples of the bubble factor section 41 include a heat source for heating the liquid, a structure that is provided on the flow path and stirs the liquid, or a location where vibration is applied due to a user operation. When bubbles are generated by the bubble factor section 41, the flow velocity meter 42 measures the flow velocity of the liquid. The flow velocity of the bubbles 40 is calculated by multiplying the flow velocity of the liquid by v ０ The generation of the bubble 40 may be determined by using the occurrence of a causative event as a trigger, or by detecting the bubble 40 itself. After the bubble 40 is generated in the bubble-causing portion 41, it flows through the inflow channel 10 having a length L.

[0032] t=t １shows a case where bubbles 40 flow through the inlet flow path 10 and reach the inlet valve 14. In this case, the outlet valve 15 is closed to block the flow path, and the liquid containing bubbles 40 is prevented from flowing into the outlet flow path 13.

[0033] Now, referring to FIG. 3, t １ 3 is a diagram showing a schematic diagram of the forces acting on the bubble 40. In FIG. 3, the buoyancy force F １ and gravity F ２ and fluid resistance F ３ is shown. Note that ρ ｆ is the density of the liquid [kg / m ３ ], V ｇ is the volume of the bubble 40 [m ３ ], g is the gravitational acceleration [m / s ２ ], ρ ｇ is the density of the bubble 40 [kg / m ３ ], C ｄ is the resistance coefficient, A ｇ is the reference area of ​​the bubble 40 [m ２ ], v ｆ is the flow velocity of the liquid [m / s]. The reference area is the cross-sectional area of ​​the bubble, which is the projected area in the flow direction fd.

[0034] The bubbles 40 in the liquid are subjected to a buoyancy F generated by the difference in density between the liquid and the gas. １ (force trying to rise) and gravity F ２ (vertical downward force) and the drag force F generated by the viscosity of the liquid ３ Buoyancy F １ is the volume V of the bubble 40 ｇ is proportional to the drag force F ３ is the cross-sectional area (projected area) of the bubble. ｇ and velocity v ｆ Generally, the buoyancy force F １ is gravity F ２ The volume of the sphere V is larger than the volume of the bubble 40, and the bubble 40 rises vertically upward in the liquid. ｇ is proportional to the cube of the radius, and the cross-sectional area A ｇ is proportional to the square of the radius of the bubble, so when the radius of the bubble increases, the cross-sectional area A ｇ Compared to the increase in volume V ｇIn other words, the larger the radius of the bubble 40, the larger the drag force F ３ than buoyancy F １ Since the rate at which the bubbles increase is greater than the rate at which they rise, the larger the bubbles, the faster they tend to rise.

[0035] Here, when only the force acting in the flow direction fd of the bubble 40 is considered, the following equation of motion (1) is derived for the x-axis direction: m represents the mass of the bubble 40.

[0036] In this case, at t = 0, the velocity of the bubble v ｘ =v ０ The distance traveled by the bubble from the bubble-causing portion 41 (in other words, the distance traveled by the bubble from the end of the inflow channel 10) is set to x=0. １ In this case, ｘ =v ｆ Let x = L. Solving equation (1) under these conditions, we get t as in equation (2). １ is derived.

[0037] If we substitute the following values ​​for the variables and calculate equation (2), t １ = 1.048 [s]. ｇ :1.293 [kg / m ３ ] (Air density when bubbles are air) Fluid density ρ ｆ : 997 [kg / m ３ ] (density of water when the liquid is water) Bubble volume V ｇ : 5 x 10 －４ x5 x 10 －４ x 3.14 = 7.85 x 10 －７ [m ３ ] (assuming the bubble diameter is 1 mm) Initial bubble velocity v ０ :0.01 [m / s] Flow velocity v ｆ : 0.01 [m / s] Drag coefficient C ｄ : 0.45 [-] Length L of inflow channel 10: 0.02 [m] Reference area A ｇ : 3.14 × (1 × 10 －３ ) 2 / 4 = 7.85 x 10 －７ [m ２ ]

[0038] t=t ２ indicates a state in which the inlet valve 14 is closed and the flow path is blocked. As a result, the liquid containing the bubbles 40 remains in the liquid reservoir 11. ２ is t １ It may be the same time as, for example, t １ In this case, the flow path may be completely closed by the inlet valve 14, and then the operation of the outlet valve 15 may be started. ０ Considering t ２ may be set.

[0039] t=t ３ indicates the case where the liquid containing the bubbles 40 is retained in the liquid reservoir 11. ２ From t ３ During this time, the liquid containing the bubbles 40 is allowed to remain in the liquid reservoir 11, thereby making it possible to cause the bubbles 40 to rise to the upper side of the liquid reservoir 11.

[0040] Referring to FIG. 3, the time t required for the bubble 40 to move from the bottom of the liquid pool 11 to the liquid surface is ３ａ (=t ３ -t ２ ) is derived. ２ At t=t, bubbles are present at the bottom of the liquid pool 11. ３ Assume that bubbles rise to the top of the liquid pool 11. The following equation of motion (3) is derived for the vertical direction:

[0041] In this case, at t = 0, the velocity of the bubble v ｚ = 0, and the distance traveled by the bubble from the bottom of the liquid pool 11 is z = 0. Also, t = t ３ａ In this case, let z = H. When equation (3) is solved under these conditions, t is obtained as in equation (4). ３ａ is derived.

[0042] If we substitute the following values ​​for the variables and calculate equation (4), t ３ａ = 0.00163 [s]. ｇ:1.293 [kg / m ３ ] Fluid density ρ ｆ : 997 [kg / m ３ ] Gravitational acceleration g: 9.8 [m / s ２ Height H of the liquid pool 11: 0.01 m

[0043] t ３ａ is the maximum time required for the air bubble 40 to reach the upper side of the liquid pool 11. ３ａ By keeping the inflow valve 14 closed during this time, it is possible to allow the bubbles 40 to reach the upper side of the liquid reservoir 11. Note that a backflow of liquid may occur between the inflow valve 14 and the inflow channel 10.

[0044] Referring to FIG. 2, t=t ４ indicates a case where the air bubbles 40 are removed. The air bubbles 40 that reach the upper side of the liquid reservoir 11 are absorbed by the remover 43. Note that, although the case where the remover 43 is installed is shown here, the present disclosure is not limited to this. It is also possible to install only the gas reservoir 12 without providing the remover 43, or to install a gas-permeable membrane between the liquid reservoir 11 and the gas reservoir 12. The gas-permeable membrane allows gas to pass from the liquid reservoir 11 to the gas reservoir 12 but does not allow liquid to pass through. The gas-permeable membrane can prevent liquid from leaking into the discharge mechanism 21. Alternatively, the air bubbles 40 may be removed by retaining the gas released from the air bubbles 40 in the gas reservoir 12.

[0045] The time required to remove the air bubbles 40, in other words, t ３ From t ４ The time until the bubble 40 is removed can be set depending on how the bubble 40 is removed. ３ and ４ may be the same.

[0046] t=t ５ indicates the case where the outflow valve 15 is opened. The liquid retained in the liquid reservoir 11 is in a state where the air bubbles 40 have been removed, and is discharged to the outflow channel 13.

[0047] t=t ６indicates the case where the inlet valve 14 is opened. The liquid flows into the liquid reservoir 11. When bubbles are generated, the time from t=0 to t=t ６ The above process is repeated.

[0048] Here, from t=0 to t=t ６ Estimate the time required for one cycle up to t １ From t ２ Time until, t ３ From t ４ Time until, t ４ From t ５ Time until, t ５ From t ６ If the time from 1 to 1000 is 1 second, then one cycle takes 5.05963 seconds. Although the addition of flow channel structure 1 may affect the flow of liquid through the microchannel device, the time required for one cycle is approximately 5 seconds, so the effect is thought to be minimal.

[0049] (Flowchart of Regulating Valve Control) FIG. 4 is a flowchart showing the operation of the inlet valve 14 and the outlet valve 15. As shown in FIG.

[0050] First, in step S1, a liquid is introduced into the microchannel device having the channel structure 1. Then, in step S2, the flow velocity of the liquid immediately after bubbles are generated by the bubble generating unit 41. The time at this point is defined as time t=0.

[0051] Subsequently, in step S3, when the air bubble 40 reaches the inlet valve 14, the inlet valve 14 and the outlet valve are closed to retain the liquid containing the air bubble in the liquid reservoir 11. １ or t ２ This corresponds to the control performed on the

[0052] Subsequently, in step S4, the air bubbles 40 are caused to rise to the upper side of the liquid pool 11 and are removed by the remover 43. Step S4 is performed at time t ３ and t ４ This corresponds to the control performed on the

[0053] Subsequently, in step S5, the outflow valve 15 is opened to discharge the liquid in the liquid reservoir 11. ５ This corresponds to the control performed on the

[0054] Subsequently, in step S6, the inlet valve 14 is opened. ６ This corresponds to the control performed on the

[0055] (Action and Effect of Controlling the Inlet and Outlet Valves) By controlling the inlet valve 14 and the outlet valve 15, it is possible to retain liquid in the liquid reservoir 11 and ensure a period of time for air bubbles to rise to the upper side of the liquid reservoir 11. Furthermore, by opening the outlet valve 15 before the air bubbles dissolve back into the liquid, it is possible to discharge the liquid from which the air bubbles have been removed into the outlet flow path 13. Furthermore, in the liquid reservoir 11, the liquid at the upper side is more likely to contain residual air bubbles than the liquid at the lower side. Therefore, the flow path flowing downstream from the outlet valve 15 is lower in height than the upstream flow path, thereby allowing as much of the lower liquid as possible to flow, with minimal air bubbles. In other words, by making the height h2 of the outlet flow path 13 lower than the height h1 of the inlet flow path 10 and lowering the height h2 than the height H of the liquid reservoir 11, it is possible to allow as much of the lower liquid as possible to flow, free of air bubbles. By repeatedly and appropriately controlling the inlet valve 14 and outlet valve 15, the liquid from which air bubbles have been removed can be flowed downstream without worrying about the generation of air bubbles.

[0056] The flow velocity of the liquid decreases when passing through the liquid reservoir 11. Since the kinetic energy of the liquid decreases when the liquid flows out of the flow path structure 1, it is possible to suppress secondary generation of bubbles downstream of the flow path structure 1.

[0057] Example 2 Example 2 differs from Example 1 in that a discharge mechanism 21 is provided in the gas reservoir portion 12 and that a partition member 22 is provided instead of the outflow valve 15. In the following description, components that are the same as or equivalent to those in Example 1 described above are denoted by the same reference numerals, and their description will be simplified or omitted.

[0058] (Channel Structure) The channel structure of the microchannel device of Example 2 will be described with reference to Fig. 5. Fig. 5 is a diagram schematically showing the channel structure of Example 2. Fig. 5(a) shows a plan view of channel structure 1a, and Fig. 5(b) shows a cross-sectional view of channel structure 1a. Fig. 5(a) is a cross-sectional view taken along line AA' in Fig. 5(b). Fig. 5(c) is a cross-sectional view taken along line BB' in Fig. 5(b).

[0059] In Example 2, the bottom of the liquid reservoir 11 is at a different height from the bottom of the inflow channel 10 and the bottom of the outflow channel 13. When the bottom of the liquid reservoir 11 is used as a reference, the bottom of the inflow channel 10 is at a height d1. The bottom of the outflow channel 13 is at a height d2. The height d1 is greater than the height d2. The widths (size in the xy plane) and heights (size in the xz plane) of the inflow channel 10 and the outflow channel 13 may be the same as in Example 1, or may be set to match the configuration of the channel structure 1a.

[0060] The exhaust mechanism 21 is a mechanism that opens the space of the gas accumulation portion 12 to the outside of the microchannel device. The exhaust mechanism 21 is, for example, an exhaust path that connects to the outside of the microchannel device. Compared to using a gas absorbing member such as a remover, the exhaust mechanism has the advantage that it does not require replacement of the member and can be used for a long period of time.

[0061] The partition member 22 is disposed in the liquid reservoir 11 and has a surface extending in a direction perpendicular to the flow direction fd. In a cross-sectional view perpendicular to the flow direction fd, the partition member 22 covers an area including a liquid level height wd, which is the liquid level reached by the liquid remaining in the liquid reservoir. The shape of the partition member 22 changes so that the area it covers narrows as it extends vertically downward from the liquid level height wd. Specifically, as shown in FIG. 5( c), the liquid reservoir 11 has a trapezoidal shape. An upper base 22a of the trapezoid is located within the gas reservoir 12 and has a width greater than the width W3 of the liquid reservoir 11 and the gas reservoir 12. A lower base 22b of the trapezoid is located inside the liquid reservoir 11 and has a width smaller than the width W3. As shown in Fig. 5(c), partition member 22 does not completely close liquid reservoir 11, and a gap 25 through which liquid can flow is formed between partition member 22 and the side surface of liquid reservoir 11. Note that partition member 22 is provided on a side of liquid reservoir 11 closer to outflow channel 13 than to inflow channel 10, as shown in Fig. 5(b).

[0062] The washing flow path 23 is a flow path for introducing a washing liquid. For example, when introducing a different liquid into the microchannel device, the washing liquid is flowed into the liquid reservoir 11 via the washing flow path 23 to wash away the liquid remaining in the liquid reservoir 11. It is also assumed that a sensor is installed in the liquid reservoir 11. In order to wash the sensor, the washing liquid is flowed into the liquid reservoir 11 via the washing flow path 23. Note that while the microchannel device is being used, a stopper 24 blocks communication between the washing flow path 23 and the liquid reservoir 11.

[0063] (Operation of Example 2) Next, we will explain the operation of the flow path structure 1a of Example 2. In the first step, the inlet valve 14 is opened, and the liquid is introduced into the liquid reservoir 11 through the inlet flow path 10. Here, the stopper 24 of the cleaning flow path 23 is closed in advance to prevent the liquid from flowing out.

[0064] In the second step, the introduction of the liquid continues, and the liquid accumulates in the liquid reservoir 11. At this time, because a step of height d1 is provided between the bottom of the inflow channel 10 and the bottom of the liquid reservoir 11, the liquid gains momentum when it is introduced from the inflow channel 10 into the liquid reservoir 11. This causes the liquid to be agitated in the liquid reservoir 11, making it more likely for bubbles to be generated. Due to their nature, bubbles gradually rise to the surface of the liquid accumulated in the liquid reservoir 11.

[0065] The partition member 22 is provided in the liquid reservoir 11 so as to separate the internal space of the liquid reservoir 11 up to a position slightly higher than the height of the outflow channel 13. Specifically, when the bottom of the liquid reservoir 11 is used as the reference, the height pd of the partition member 22 is higher than the height of the outflow channel 13 (a height similar to the height wd of the liquid surface in the liquid reservoir 11). This is to prevent air bubbles generated in the gas reservoir 12 from flowing out toward the outflow channel 13 as much as possible.

[0066] However, when viewed from the flow direction fd, if the partition member 22 completely separates the liquid reservoir 11 and has a height sufficient to reach the gas reservoir 12, when the liquid overflows from the upper side of the partition member 22 into the outflow channel 13, the liquid may be agitated, generating bubbles, which may actually increase the number of bubbles. To avoid this, as shown in FIG. 5( c), the partition member 22 has a shape that forms a gap 25, which is an area between the partition member 22 and the liquid reservoir 11, and this gap 25 allows a certain amount of liquid to move in and out. Although there is a possibility that bubbles may move from the gap 25 toward the outflow channel 13, the effect is considered to be negligible.

[0067] Furthermore, since the air bubbles gradually rise from the liquid remaining in the liquid reservoir 11, there are more of them at the upper side than at the lower side of the liquid reservoir 11. The partition member 22 is structured such that the upper side thereof prevents the liquid from overflowing from the liquid reservoir 11 into the outflow flow path 13, and the lower side thereof allows the liquid remaining in the liquid reservoir 11 to properly flow out into the outflow flow path 13.

[0068] In FIG. 5( b ), the liquid level wd in the liquid reservoir 11 and the height of the outflow channel 13 (the liquid level in the outflow channel 13) are substantially the same, but the present disclosure is not limited to this. The liquid level in the liquid reservoir 11 and the liquid level in the outflow channel 13 can also be made different. Also, as shown in FIG. 5( c ), the gap 25 has a shape that is symmetrical across the partition member 22, but the present disclosure is not limited to this. The size, shape, and position of the gap 25 can be set depending on the properties of the liquid and the structure of the liquid reservoir 11.

[0069] Continuing with the explanation of the operation, in the third step, when the liquid accumulates in the liquid reservoir 11 up to the height of the outflow channel 13, the inflow valve 14 is closed slightly to reduce the opening of the inflow valve 14. By doing so, the amount of liquid flowing into the liquid reservoir 11 can be reduced. The state of the liquid accumulated in the liquid reservoir 11 approaches a static state, creating a situation in which air bubbles are likely to rise to the liquid surface. Note that if the inflow valve 14 is completely closed, liquid may flow in forcefully when the inflow valve 14 is opened again, creating a situation in which air bubbles are likely to be generated. Although the generated air bubbles basically accumulate in the liquid reservoir 11 and have little impact, there is a possibility that the air bubbles may leak into the outflow channel 13. For this reason, it is preferable to avoid completely closing the inflow valve 14.

[0070] Next, in a fourth step, the bubbles that have accumulated near the liquid surface in the liquid reservoir 11 are discharged to the outside of the flow path structure 1a using a discharge mechanism. Specifically, the gas generated from the bubbles is discharged from the discharge mechanism 21 to the outside of the microflow path device including the flow path structure 1a. Furthermore, if the gas tends to accumulate near the liquid surface in the liquid reservoir 11, it is also possible to place an absorbent or other absorbing material near the liquid surface and allow the gas to be adsorbed by the absorbing material.

[0071] Subsequently, in a fifth step, the liquid that has accumulated in the liquid reservoir 11 up to the same height as the outflow channel 13 is discharged into the outflow channel 13. That is, of the liquid that has accumulated in the liquid reservoir 11, the liquid that exceeds the height of the bottom of the outflow channel 13 is discharged from the outflow channel 13, and the discharged liquid has had air bubbles removed.

[0072] Next, in the sixth step, it is detected that the liquid level in the liquid reservoir 11 has dropped and liquid is no longer flowing out from the liquid reservoir 11 to the outflow channel 13. If liquid is not being discharged into the outflow channel 13, the inflow valve 14 is opened and the operation is repeated from the first step.

[0073] Furthermore, if the inlet valve 14 is left closed, liquid will remain in the liquid reservoir 11, so in order to drain the liquid, the stopper 24 of the cleaning flow path 23 will be opened and the liquid will be drained from the liquid reservoir 11.

[0074] (Flowchart of Operation in Second Embodiment) Next, the operation of the second embodiment will be described with reference to Fig. 6. Fig. 6 is a flowchart showing the operation of the flow path structure 1a of the second embodiment.

[0075] First, in step S20, a liquid is introduced into the microchannel device having the channel structure 1a.

[0076] Subsequently, in step S21, the inlet valve 14 is opened to introduce the liquid into the liquid reservoir 11. Step S21 corresponds to the first step.

[0077] Subsequently, in step S22, the introduction of the liquid continues. Step S22 corresponds to the second step described above.

[0078] Next, in step S23, it is detected whether or not the liquid flows out into the outflow channel 13. If no outflow is detected (No in step S23), the liquid injection in step S22 continues. If outflow is detected (Yes in step S23), the process proceeds to step S24.

[0079] In step S24, the opening of the inlet valve 14 is adjusted to be smaller. Step S24 corresponds to the third step.

[0080] While the opening of the inlet valve 14 is being adjusted to be small, bubbles generated in the liquid reservoir 11 are removed (step S25, fourth step). Specifically, the gas generated from the bubbles is discharged to the outside of the microchannel device by the discharge mechanism 21. Furthermore, the gas remaining near the liquid surface in the liquid reservoir 11 is adsorbed by an absorbent such as a remover. Furthermore, the liquid is discharged from the liquid reservoir 11 to the outlet channel 13 (step S26, fifth step).

[0081] Next, in step S27, it is detected whether or not liquid is flowing out from the liquid reservoir 11 to the outflow channel 13. Step S27 corresponds to the sixth step. If liquid is no longer flowing out (No in step S27), the process returns to step S21 again, and the inflow valve 14 is opened to inject liquid. If liquid is flowing out (Yes in step S27), the detection in step S27 is performed again.

[0082] (Effects of Example 2) In the flow path structure 1a, a liquid reservoir 11 that temporarily stores liquid is provided at the end of the inflow path 10 in the flow direction fd. When the liquid reservoir 11 is filled with liquid, the liquid naturally flows into the outflow path 13. Because the flow rate of the liquid passing through the outflow path 13 is reduced, it is possible to suppress the secondary generation of bubbles when the liquid passes through the outflow path 13.

[0083] Furthermore, the partition member 22 is provided on a side of the liquid reservoir 11 closer to the outflow channel 13 than the inflow channel 10. By increasing the distance over which the liquid injected into the liquid reservoir 11 reaches the partition member 22, the liquid can be retained in the liquid reservoir 11 for as long as possible, ensuring a period during which air bubbles can be removed. Furthermore, by adjusting the opening of the inflow valve 14, a state close to a static state can be created in the liquid reservoir 11, making it possible to more effectively remove air bubbles.

[0084] Example 3 Example 3 illustrates a case where a microfluidic device having a channel structure according to the present disclosure is used in a wearable device. Possible applications of the wearable device include, for example, testing and analyzing components of sweat (e.g., cortisol) generated by the human body, such as so-called healthcare monitoring. While the following description illustrates a case where the microfluidic device is worn on the human body, the present disclosure is not limited to this. It is also possible to use the microfluidic device as a sensor that acquires human body information in a non-contact or unconstrained manner.

[0085] A wearable device according to a third embodiment will be described with reference to FIG. 7 . FIG. 7 is a diagram illustrating a wearable device according to a third embodiment. FIG. 7( a) illustrates a cross section of the wearable device, and FIG. 7( b) illustrates the state in which the wearable device is in use. The wearable device 300 is equipped with a microfluidic device having a channel structure according to the present disclosure, and includes a holding mechanism 30 that holds the gas reservoir 12 so that it faces vertically upward relative to the liquid reservoir 11. A detailed description will be given below.

[0086] FIG. 7A shows a cross-sectional view of a wearable device 300. The wearable device 300 includes a liquid reservoir 11 and a gas reservoir 12 in the flow channel structure 1 or 1a of the mounted microchannel device, and a holding mechanism 30. The holding mechanism 30 includes rollers 31 and a support 32. The flow channel configuration and the microchannel device are omitted here to explain the positional relationship between the liquid reservoir 11 and the gas reservoir 12. For example, glass or resin members that constitute the microchannel device may be present between the liquid reservoir 11 and the holding mechanism 30, but these are omitted in FIG. 7. Furthermore, the structure of the holding mechanism 30 is omitted in detail to explain the positional relationship between the liquid reservoir 11 and the gas reservoir 12.

[0087] Liquid reservoir 11 is positioned vertically upward relative to gas reservoir 12. Establishing this positional relationship causes air bubbles generated in liquid reservoir 11 to rise to the upper side of liquid reservoir 11 and be removed in liquid reservoir 11, thereby removing gas remaining in gas reservoir 12. In order for wearable device 300 to function properly, it is necessary to maintain the vertical positional relationship between liquid reservoir 11 and gas reservoir 12.

[0088] 7(b) shows a case where the wearable device 300 is attached to a human body 33. The human body 33 is a part of the human body, and may be, for example, the wrist, fingers, head, or neck depending on the mode of the wearable device. The device is not limited to being in direct contact with human skin, and may be attached to clothing worn by the human.

[0089] The roller portion 31 is located between the liquid pool portion 11 and the support portion 32. The roller portion 31 is a rolling element that rotates around the x-axis direction. While four roller portions 31 are shown in Figure 7, each roller portion 31 is disposed at a predetermined position on the support portion 32.

[0090] The support portion 32 is fixed to the human body 33. As shown in (1) and (2) of FIG. 7B , when the orientation of the human body 33 changes, the orientation of the support portion 32 also changes along with the human body 33. Meanwhile, the liquid reservoir 11 and the gas reservoir 12 move on the roller portion 31 along the shape of the support portion 32. During this movement, the gas reservoir 12 is maintained in a vertically upward position relative to the liquid reservoir 11. It is also possible to arrange a weight member facing the gas reservoir 12 across the liquid reservoir 11, so that when the orientation of the wearable device 300 changes, the weight member moves vertically downward, making it easier for the gas reservoir 12 to maintain its vertically upward position. FIG. 7 illustrates only one example of a configuration, and the present disclosure is not limited thereto. The configuration and shape of the roller portion 31 and the support portion 32 can also be appropriately set.

[0091] (Effects of Example 3) Generally, the orientation of a wearable device changes in response to the movement of the human body while it is in use. For this reason, it may be difficult to utilize the function of the gas reservoir portion, which is the space above the flow path structure described in Examples 1 and 2 of the present disclosure.

[0092] In contrast, the wearable device of Example 3 has a holding mechanism 30 having a support portion 32 on which roller portions 31 are arranged. When a change occurs in the body of the person wearing the wearable device, the liquid reservoir portion 11 moves to a vertically downward position, so that the flow path structure attempts to maintain as horizontal a position as possible. This allows the positional relationship between the liquid reservoir portion 11 and the gas reservoir portion 12 to be maintained so that the function of collecting air bubbles can be exerted.

[0093] (Aspects of the Present Disclosure and Their Effects) As described above, the present disclosure includes the following aspects. Furthermore, according to these aspects, it is possible to suppress the effects of bubbles generated from liquid in a microchannel device. The effects of each aspect of the present disclosure are explained as follows. (First Aspect) A channel structure constituting part of a microchannel device, the channel structure comprising: an inflow channel through which liquid flows; a liquid reservoir connected to the inflow channel; a gas reservoir provided vertically upward from the liquid reservoir; and an outflow channel connected to the liquid reservoir. [Effects of the First Aspect] When sensing in a system using a microchannel device, it is possible to prevent bubbles from migrating to the sensing portion, thereby reducing problems during measurement. It is possible to reduce the generation of bubbles that affect the flow of liquid in the microchannel device.

[0094] (Second Aspect) The flow channel structure according to the first aspect further comprises an inlet valve provided between the inlet channel and the liquid reservoir, and an outlet valve provided between the liquid reservoir and the outlet channel, wherein the inlet valve and the outlet valve are adjustment valves capable of controlling the flow of the liquid, and by operating the inlet valve and the outlet valve, bubbles generated from the liquid are guided to the upper side of the liquid reservoir. [Advantages of the Second Aspect] - Backflow can be prevented by appropriately controlling the microchannel with the valve. - Bubbles can be easily guided to the upper side of the liquid reservoir. - Secondary generation of bubbles during passage through the flow channel can be suppressed by reducing the kinetic energy of the liquid when it flows out.

[0095] (Third Aspect) The flow channel structure according to the first or second aspect, characterized in that, in a cross-sectional view perpendicular to the flow direction, the direction in which the liquid flows is the flow direction, the liquid reservoir has a larger flow channel area than the inflow channel and the outflow channel. (Fourth Aspect) The flow channel structure according to any one of the first to third aspects, characterized in that, when the microchannel device is placed, the liquid level in the outflow channel is lower than the liquid level in the inflow channel. [Effects of the Third and Fourth Aspects] - By providing flow channels at different height positions before and after the liquid reservoir (the flow channel in front of the liquid reservoir (the inflow channel) is higher than the outflow channel) and providing a space above the liquid reservoir, it is possible to trap air bubbles using only the structure without using external force.

[0096] (Fifth Aspect) A flow path structure according to any one of the first to fourth aspects, characterized in that the flow direction is the direction in which the liquid flows, the partition member is provided in the liquid reservoir and has a surface that extends in a direction perpendicular to the flow direction, wherein, in a cross-sectional view perpendicular to the flow direction, the partition member covers an area that includes a liquid level that is the height of the liquid level reached by the liquid remaining in the liquid reservoir, and the shape of the partition member changes so that the area that covers the liquid reservoir narrows as it extends vertically downward from the liquid level. [Advantages of the Fifth Aspect] Secondary bubbles are less likely to be generated while the liquid is passing through the flow path.

[0097] (Sixth Aspect) The flow channel structure according to any one of the first to fifth aspects, characterized in that the gas trap portion is provided with a discharge mechanism that opens the space of the gas trap portion to the outside of the microchannel device. [Advantages of the Sixth Aspect] - Because it is an open system, trapped gas is discharged to the outside, allowing for long-term use.

[0098] (Seventh Aspect) The flow path structure according to any one of the first to sixth aspects, further comprising an absorbing member for absorbing gas in the gas accumulation portion. [Advantages of the Seventh Aspect] - The absorbing member (e.g., an absorption sheet) can reliably trap air bubbles inside the device. - The use of a sheet that absorbs VOCs (volatile organic compounds) leads to a reduction in environmental impact.

[0099] (Eighth Aspect) The flow path structure according to any one of the first to seventh aspects, further comprising a gas-permeable membrane between the liquid reservoir and the gas reservoir. [Advantages of the Eighth Aspect] The gas-permeable membrane can prevent leakage of the liquid sample from the discharge mechanism.

[0100] (Ninth Aspect) The flow path structure according to any one of the first to eighth aspects, further comprising a cleaning flow path for introducing a cleaning liquid into the liquid reservoir. [Advantages of the Ninth Aspect] - The liquid reservoir can be cleaned.

[0101] (10th Aspect) A microchannel device having the channel structure according to any one of Aspects 1 to 9. [Advantages of the 10th Aspect] A microchannel device capable of suppressing the effects of bubbles generated from a liquid can be obtained.

[0102] (Eleventh Aspect) A wearable device equipped with a microchannel device having the channel structure according to any one of the first to ninth aspects, characterized in that the wearable device comprises a holding mechanism that holds the gas reservoir portion so that it faces vertically upward relative to the liquid reservoir portion. [Effects of the Eleventh Aspect] Even when a channel is incorporated into the wearable device, rollers can be provided between the wearable device and the channel provided therein to ensure as much space as possible above the channel, even if the channel is tilted due to exercise or the like, so that the channel can be kept as horizontal as possible.

[0103] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention.

[0104] In addition, bubbles often exist in the flow channel due to changes in temperature and pressure, but when the flow channel is used as a biodevice, CO is inevitably generated due to the respiration of microorganisms. ２ In addition, CO2 can be emitted during alcohol fermentation in brewing processes that use yeast. ２ In many cases, microfluidic devices are used as biodevices rather than to observe physical changes, and in fields such as microbiology and brewing, it is thought that there will be an increasing need for a technology that can anticipate the presence of many bubbles and remove them as much as possible.

[0105] 1, 1a: flow path structure, 10: inlet flow path, 11: liquid reservoir, 11a: connection flow path, 12: gas reservoir, 13: outlet flow path, 14: inlet valve, 15: outlet valve, 21: discharge mechanism, 22: partition member, 22a: upper base, 22b: lower base, 23: cleaning flow path, 24: stopper, 25: gap, 30: holding mechanism, 31: roller portion, 32: support portion, 33: human body, 40: air bubble, 41: air bubble generating portion, 42: flow rate meter, 43: remover, 300: wearable device

Claims

1. A flow channel structure constituting part of a micro flow channel device, comprising: an inflow channel through which a liquid flows; a liquid reservoir connected to the inflow channel; a gas reservoir provided vertically upward from the liquid reservoir; and an outflow channel connected to the liquid reservoir.

2. The flow path structure described in claim 1, further comprising an inlet valve provided between the inlet flow path and the liquid pool, and an outlet valve provided between the liquid pool and the outlet flow path, wherein the inlet valve and the outlet valve are adjustment valves capable of controlling the flow of the liquid, and by operating the inlet valve and the outlet valve, air bubbles generated from the liquid are guided to the upper side of the liquid pool.

3. The flow path structure according to claim 1, characterized in that, when viewed in a cross-sectional view perpendicular to the flow direction, the direction in which the liquid flows is the circulation direction, the liquid pool portion has a flow path area larger than those of the inlet flow path and the outlet flow path.

4. The flow path structure according to claim 1, characterized in that, when the micro-flow path device is placed, the liquid level in the outflow path is lower than the liquid level in the inflow path.

5. A flow path structure as described in claim 1, characterized in that the direction in which the liquid flows is the flow direction, the partition member is provided in the liquid pool portion and has a surface that extends in a direction perpendicular to the flow direction, wherein, when viewed in cross-section in the direction perpendicular to the flow direction, the partition member covers an area that includes a liquid level height that is the liquid level reached by liquid retained in the liquid pool portion, and the shape of the partition member changes so that the area it covers narrows as it moves vertically downward from the liquid level height.

6. The flow path structure according to claim 1, characterized in that the gas accumulation portion is provided with an exhaust mechanism that opens the space of the gas accumulation portion to the outside of the micro flow path device.

7. The flow path structure according to claim 1, further comprising an absorbing member for absorbing gas in the gas accumulation portion.

8. The flow path structure according to claim 1, further comprising a gas-permeable membrane between said liquid pool and said gas pool.

9. The flow path structure according to claim 5, further comprising a cleaning flow path for introducing a cleaning liquid into said liquid reservoir.

10. A microchannel device having a channel structure according to any one of claims 1 to 9.

11. A wearable device equipped with a microchannel device having a channel structure described in any one of claims 1 to 9, characterized in that the wearable device is provided with a holding mechanism that holds the gas pool portion so that it is positioned vertically upward relative to the liquid pool portion.

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