Flow path structure, flow path structure unit, and production method of lipid particle

Abstract

To provide a flow path structure capable of promoting mixing of two fluids, a flow path structure unit, and a production method of a lipid particle.SOLUTION: A flow path structure of an embodiment includes a first flow path, a second flow path, and a third flow path. The second flow path is connected to the first flow path, and the third flow path is connected to the first flow path and the second flow path. When a distance between a top surface and a bottom surface of the flow path is defined as a flow path depth, the flow path depth of the second flow path in an opening through which the first flow path is connected with the second flow path is not constant, and the maximum value of the flow path depth of the second flow path in the opening is smaller than the flow path depth of the first flow path.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present embodiment relates to a flow channel structure, a flow channel structure unit, and a method for producing lipid particles. [Background technology]

[0002] To ensure uniform chemical reactions in liquids, it is necessary to forcibly promote the mixing of reactants by stirring them to create vortices or turbulence. Therefore, there is a need for a mixing method that can further promote the mixing of two liquids. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-167074 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a flow channel structure, a flow channel structure unit, and a method for producing lipid particles that can further promote mixing of two fluids. [Means for solving the problem]

[0005] The flow path structure of the embodiment includes a first flow path, a second flow path, and a third flow path. The second flow path is connected to the first flow path, and the third flow path is connected to the first and second flow paths. When the distance between the top and bottom surfaces of the flow paths is defined as the flow path depth, the flow path depth of the second flow path at the opening where the first flow path connects to the second flow path is not constant, and the maximum value of the flow path depth of the second flow path at the opening is smaller than the flow path depth of the first flow path. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a perspective view showing an example of a flow path structure according to a first embodiment. [Figure 2]FIG. 2 is a schematic view showing an example of a flow path structure according to the first embodiment. [Figure 3] FIG. 2 is a plan view showing an example of a flow path structure according to the first embodiment. [Figure 4] FIG. 10 is a diagram showing an example of a simulation result of the mixing of two liquids. [Figure 5] FIG. 2 is a schematic diagram showing the mixing of two liquids. [Figure 6] 3 is an example of a cross-sectional view taken along the main flow direction of a first flow path and a third flow path of the flow path structure according to the first embodiment. FIG. [Figure 7] 10 is an example of a cross-sectional view taken along the main flow direction of a first flow path and a third flow path of a flow path structure in a first modified example. [Figure 8] FIG. 10 is a schematic diagram showing how two liquids are mixed in a first modified example. [Figure 9] 10 is an example of a cross-sectional view taken along the main flow direction of a first flow path and a third flow path of a flow path structure in a second modified example. [Figure 10] 10A and 10B are schematic diagrams showing variations of the flow path structure 100 in a third modified example. [Figure 11] 10 is an example of a plan view of a flow path structure according to a second embodiment. [Figure 12] FIG. 2 is a schematic diagram of an example of a flow path structure unit. [Figure 13] FIG. 2 is a schematic diagram of an example of a flow path structure unit. [Figure 14] FIG. 2 is a schematic diagram of an example of a flow path structure unit. [Figure 15] 1A to 1C are schematic diagrams illustrating an example of a method for manufacturing a flow path structure. [Figure 16] FIG. 10 is a diagram showing an example of a lipid particle according to a sixth embodiment. [Figure 17] 1 is a flowchart illustrating an example of a method for producing lipid particles. [Figure 18] FIG. 10 is a diagram showing an example of a flow path structure used in a method for producing lipid particles according to a sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments will be described with reference to the accompanying drawings. In each embodiment, substantially identical components are denoted by the same reference numerals, and some of their descriptions may be omitted. The drawings are schematic, and the relationship between the thickness of each component and the planar dimensions, the thickness ratio of each component, etc. may differ from the actual ones.

[0008] When a fluid flows through the flow path structure, the direction of the main flow in the flow path is as shown by the arrow in the drawing, and the description will be given assuming that the direction is substantially along the pipe axis direction.

[0009] In this specification, a "channel" refers to a space formed inside a channel structure through which a fluid can flow. The channel has openings on both the upstream and downstream sides of the fluid. The channel has walls made of a base material such as resin, glass, ceramics, or metal, and the top or bottom of the channel is sealed by the base material of the channel structure. In this specification, a liquid will be used as an example of the fluid.

[0010] (First embodiment) FIG. 1 is a perspective view showing an example of a flow path structure 100 according to a first embodiment. In this embodiment, the flow path structure includes a first flow path 1, a second flow path 2 connected to the first flow path 1, and a third flow path 3 connected to the first flow path 1 and the second flow path 2. In this specification, the second flow path 2 is indicated by a dotted pattern. Furthermore, when the distance between the top and bottom surfaces of the flow path is defined as the flow path depth, the flow path depth of the second flow path 2 at the opening where the first flow path 1 connects to the second flow path 2 is not constant. Furthermore, the maximum flow path depth (h2) of the second flow path 2 at the opening is smaller than the flow path depth (h1) of the first flow path 1. The arrows in the figure indicate the main flow directions of the liquid flowing inside the flow path structure. The liquids flowing through the first flow path 1 or the second flow path 2 merge and flow through the third flow path 3. In this embodiment, when liquid is flowed through the flow path structure, the downstream side of the second flow path 2 is connected to the downstream side of the first flow path 1, and the third flow path 3 is connected further downstream of the first flow path 1 and the second flow path 2. Here, "connected" to a flow path refers to a state in which an end of a flow path is liquid-tightly connected to another flow path so that the internal space of the flow path communicates with the internal space of the other flow path, forming a continuous space. The material of the flow path structure 100 is not particularly limited, but is, for example, a solid resin such as cycloolefin polymer (COP). The material of the flow path structure 100 will be described in detail later. The first flow path 1, the second flow path 2, and the third flow path 3 are spaces formed by cutting a bulk solid such as COP to form grooves.

[0011] FIG. 2(a) is a plan view showing an example of a flow channel structure 100 according to a first embodiment. In this specification, unless otherwise specified, the flow channel wall surface located closest to the page in FIG. 2(a) is referred to as the top surface, the flow channel wall surface facing the top surface and located further back than the top surface is referred to as the bottom surface, and the flow channel wall surface intersecting the top and bottom surfaces is referred to as the flow channel side surface. The dimension of the flow channel perpendicular to the page, i.e., the distance between the top and bottom surfaces, is referred to as the flow channel depth. Unless otherwise specified, the flow channel depth is based on a plane including the top surface. In this specification, unless otherwise specified, the dimension perpendicular to the pipe axis direction and parallel to the page in FIG. 2(a) is referred to as the flow channel width. As shown in FIGS. 1 and 2, the top surfaces of the first flow channel 1, the second flow channel 2, and the third flow channel 3 are preferably included in a single plane. This allows the flow channel structure 100 to be fabricated easily and accurately. Details will be described in later embodiments.

[0012] The width and depth of the first flow path 1, the second flow path 2, and the third flow path 3 are appropriately determined in consideration of various conditions such as the type and flow rate of the liquid supplied to the flow path structure. For example, the Reynolds number Re is a numerical value that takes into consideration the shape of the flow path structure 100, the type and flow rate of the liquid, etc. The Reynolds number Re is expressed as ρ [kg / m 3 ] is the density of the liquid, V [m / s] is the velocity of the liquid, L [m] is the characteristic length, and μ [Pa·s] is the viscosity of the liquid, and is a dimensionless number defined by the following equation (1). Re=ρVL / μ…(1)

[0013] In calculating the Reynolds number of the flow channel according to this embodiment, the hydraulic diameter d H is the characteristic length L. Hydraulic diameter d H is defined by the following equation (2), where A is the cross-sectional area of ​​the flow path and P is the cross-sectional edge length of the flow path. d H =4A / P…(2)

[0014] The characteristic length L when calculating the Reynolds number of a liquid flowing through a channel is the hydraulic diameter d H However, the flow path depth, the flow path width, or the average value thereof may also be used as the representative length.

[0015] In order to achieve the effects of the present invention, the Reynolds number calculated from the above formula (1) is preferably 10 or more in the flow path structure. In order to generate uniform vortices and avoid the occurrence of turbulence in the flow paths, the Reynolds number is preferably less than 2300 in the flow path structure. The Reynolds number is also preferably less than 2300 at the point where the second flow path 2 joins the first flow path 1, where the area of ​​the flow path cross section perpendicular to the pipe axis direction is smallest in the figure. Note that, in order to further promote the generation of uniform vortices and further prevent the occurrence of turbulence in the flow paths, it is more preferable that the Reynolds number in the flow path structure be approximately 50 or more and 1000 or less. Note that the cross-sectional area perpendicular to the pipe axis direction of the flow paths included in the flow path structure 100 is 100 mm 2 It is preferable that the width and depth of the flow channel are equal to or less than 5 μm. However, from the viewpoint of suppressing cavitation in the flow channels and avoiding clogging due to bubbles or the like in the flow channels, the width and depth of the flow channel are preferably equal to or more than 5 μm, and since the accuracy of mold molding or cutting, which is a method for producing the flow channel structure 100, is generally 5 μm, taking into consideration the machining accuracy of the flow channels, it is desirable that the width and depth of the flow channel are equal to or more than 10 μm. Furthermore, from the viewpoint of ensuring the strength of the mold for producing the flow channel structure 100, it is preferable that the depth of the flow channel be equal to or less than the width of the first flow channel 1, the second flow channel 2, and the third flow channel 3.

[0016] Hereinafter, each part of the flow path structure in this embodiment will be described in detail.

[0017] The first flow path 1 has a constant flow path width and flow path depth in most regions. However, this does not apply to a mixing region 13 near the confluence of the first to third flow paths. For example, at the point where the second flow path 2 connects to the first flow path 1, when the surface surrounded by the ridge lines at the end of the second flow path 2 is defined as the second opening 12, the flow path width of the first flow path 1 is defined as the shortest distance (d1 in the figure) between the second opening 12 and the side of the first flow path 1 facing the second opening 12. At the boundary between the first flow path 1 and the third flow path 3, when the surface surrounded by the ridge lines at the end of the first flow path 1 is defined as the first opening 11, the flow path width of the first flow path 1 is defined as the shortest distance (d2 in the figure) from any point on the first opening 11 to the second opening 12. The flow path width defined by the first opening 11 and the second opening 12 decreases downstream. In this embodiment, the width and d1 of the first flow path 1 outside the mixing region 13 are, for example, 0.3 mm, and the flow path depth is, for example, 0.3 mm. The average flow velocity of the liquid flowing through the first flow path 1 is preferably approximately 0.1 m / s or greater. Assuming that the liquid is similar to water and the representative length is the hydraulic diameter, the Reynolds number at room temperature is approximately 30. When using a pump to introduce liquid into the flow path structure of this embodiment, it is preferable to use a pump that does not generate pulsation. Such pumps with a liquid delivery rate of approximately 1 mL / sec are readily available. Considering this, the width and depth of the first flow path 1 are preferably approximately 3 mm or less, i.e., a so-called microflow path. Note that the first flow path 1 may also be described as the main flow path in the flow path structure 100.

[0018] The second flow path 2 has a constant flow path width in most regions. However, this does not apply to the mixing region 13. For example, at the point where the second flow path 2 connects to the first flow path 1, the flow path width of the second flow path 2 is the shortest distance (d3 in the figure) between the second opening 12 and the flow path wall surface of the second flow path 2 on the side connecting to the third flow path 3. In this embodiment, the flow path width of the second flow path 2 other than the mixing region 13 is, for example, 0.3 mm.

[0019] At the point where the second flow path 2 connects to the first flow path 1, the flow path width of the second flow path 2 is the shortest distance from any point on the second opening 12 to the flow path wall surface of the second flow path 2 that is farther from the first flow path 1. The flow path width defined by the second opening 12 and the side surface of the second flow path 2 becomes smaller toward the downstream side.

[0020] Furthermore, the second flow path 2 has a different flow path depth depending on the position. FIG. 2(b) is an example of a cross-sectional view of the flow path structure 100 according to the first embodiment, taken along the main flow direction of the first flow path 1 and the third flow path 3. As described above, the second flow path 2 is indicated by dotted hatching. The maximum flow path depth (h2) of the second flow path 2 is equal to or less than the flow path depth (h1) of the first flow path 1. The depth of the second flow path 2 at the point where the second flow path 2 connects to the first flow path 1 varies along the width direction of the second flow path 2. FIG. 2(b) illustrates an example in which the flow path depth of the second flow path 2 varies at a constant gradient, and the flow path depth (h2) of the second flow path 2 at the point where the flow path side surface of the second flow path 2 and the flow path side surface of the first flow path 1 meet is greater than the flow path depth (h3) of the second flow path 2 at the flow path wall surface on the opposite side of the second flow path 2 at the point where the flow path side surface of the second flow path 2 and the flow path side surface of the first flow path 1 meet. That is, the depth of the second flow path 2 at the point where the second flow path 2 connects to the first flow path 1 becomes shallower as it approaches the opposite flow path wall surface. This reduces the cross-sectional area of ​​the flow path, making it possible to increase the flow rate of the liquid passing through. The maximum flow path depth (h2) of the second flow path 2 is preferably ½ or less, more preferably ⅓ or less, of the flow path depth (h1) of the first flow path. That is, in the flow path structure 100 shown in this embodiment, when the flow path depth of the first flow path 1 is, for example, 0.3 mm, the maximum depth (h2) of the second flow path 2 is preferably 0.15 mm or less, more preferably 0.10 mm or less. However, as explained above in the description of the first to third flow paths, for reasons of flow path fabrication and practicality, the maximum depth (h2) of the second flow path 2 is preferably 5 μm or more, more preferably 10 μm or more. Furthermore, the minimum depth (h3) of the second flow path 2 only needs to be smaller than the maximum value, and may be 0 mm (where the cross-sectional shape of the second flow path 2 in FIG. 2(b) is triangular). The second flow path 2 shown in this embodiment has a flow path width of, for example, 0.3 mm, a maximum flow path depth of 0.1 mm, and a minimum flow path depth of 0.0 mm. It is preferable that the average flow velocity of the liquid flowing through the second flow path 2 is approximately 0.1 m / s or more. If the liquid is assumed to be similar to water and the characteristic length is taken as the hydraulic diameter, the Reynolds number at around room temperature is around 30.When a pump is used as a device for introducing liquid into the flow channel structure according to this embodiment, it is preferable to use a pump that does not generate pulsation. Such pumps are readily available with a liquid delivery rate of approximately 1 mL / sec. Taking this into consideration, it is preferable that the second flow channel 2 has a width and depth of approximately 3 mm or less, that is, a so-called micro-flow channel. Note that the second flow channel 2 may be described as a sub-flow channel in the flow channel structure 100.

[0021] The third flow path 3 may have a constant width and depth throughout most of the region. However, this does not apply to the mixing region 13. For example, where the first flow path 1 connects to the third flow path 3, the width of the third flow path 3 is the shortest distance from any point on the first opening 11 to the wall of the third flow path 3 that connects to the second flow path 2. The width defined by the side of the first opening 11 and the third flow path 3 increases toward the downstream side. In this embodiment, the third flow path 3 has a flow path of, for example, 0.3 mm and a flow depth of 0.3 mm. The average flow velocity of the liquid flowing through the third flow path 3 is preferably approximately 0.1 m / s or greater. Assuming the liquid is similar to water and the representative length is the hydraulic diameter, the Reynolds number at room temperature is approximately 30. When a pump is used to introduce liquid into the flow path structure of this embodiment, it is preferable to use a pump that does not generate pulsation. Such pumps with a liquid delivery rate of approximately 1 mL / sec are readily available. Considering this situation, it is preferable that the third flow path 3 has a width and depth of approximately 3 mm or less, that is, a so-called micro flow path. Note that the third flow path 3 may be described as a merging flow path in the flow path structure 100.

[0022] FIG. 3 is a plan view showing an example of a flow path structure 100 according to the first embodiment. The angle between the first flow path and the second flow path will be described using this figure. As shown in FIG. 3, in the flow path structure 100 according to the first embodiment, the axial direction of the first flow path 1 does not coincide with the axial direction of the third flow path 3. That is, the first flow path 1 and the third flow path 3 are not a continuous straight line. By connecting the first flow path 1 so that the flow direction of the third flow path 3 intersects, a vortex is formed in the third flow path 3 between the liquid passing through the first flow path 1 (flow from the main flow path) and the liquid passing through the second flow path 2 (flow from the sub-flow path), enabling rapid mixing. The first flow path 1 and the second flow path 2 are symmetrical with respect to the third flow path 3. The angle between the side of the first flow path 1 and the side of the third flow path 3 is β, and the angle between the side of the second flow path 2 and the side of the third flow path 3 is γ. While β and γ may be different, they are preferably equal. By setting the values ​​of β and γ to a predetermined value greater than 0°, it is possible to prevent the flow from the main flow path and the flow from the sub-flow path from merging in a substantially parallel manner, thereby maintaining the mixing speed in the third flow path 3. Specifically, when the second flow path 2 merges perpendicularly to the first flow path 1 (i.e., the sum of β and γ is 90°), the opening area of ​​the second opening 12 becomes small, resulting in the fastest mixing speed. Furthermore, by setting the values ​​of β and γ to a predetermined value or less, it is possible to prevent the flow from the main flow path and the flow from the sub-flow path from colliding head-on, thereby facilitating the generation of an orderly vortex and maintaining uniform mixing. Therefore, it is preferable that the first flow path 1 and the second flow path 2 intersect at an angle within a predetermined range. Therefore, it is preferable that the sum of β and γ is 60° or more and 120° or less, and particularly preferably 90°. Furthermore, it is more preferable that the first flow path 1 and the second flow path 2 are symmetrical with respect to the third flow path 3. Therefore, it is preferable that β and γ are each 30° or more and 60° or less, and it is particularly preferable that β = γ = 45°. When a liquid flows through the flow path structure 100 described here, the angle formed by the mainstream direction of the liquid flowing through the first flow path 1 and the mainstream direction of the liquid flowing through the third flow path 3 corresponds to β, and the angle formed by the mainstream direction of the liquid flowing through the second flow path 2 and the mainstream direction of the liquid flowing through the third flow path 3 corresponds to γ.

[0023] In this way, the flow channel structure 100 has a structure in which the flow channel depth of the sub-channels changes along the flow direction in the main channel, so that the liquid that passes through the main channel and flows into the confluence channel and the liquid that passes through the sub-channel and flows into the confluence channel can be mixed quickly and efficiently, thereby promoting the mixing of the two liquids. Furthermore, this can be achieved with a relatively simple structure.

[0024] 4A and 4B show an example of the results of a simulation of the mixing of two liquids. FIG. 4A shows the flow path structure 100 as viewed from the top surface, and FIG. 4B shows the degree of mixing at each point when sliced ​​perpendicularly to the main flow direction of the liquid flowing through the third flow path 3. The flow from the first flow path 1 is shown in black, and the flow from the second flow path 2 is shown in white. From FIGS. 4A and 4B, it can be seen that a vortex is generated in the third flow path 3, causing the two liquids to mix.

[0025] FIG. 5 is a schematic diagram showing the mixing of two liquids. FIG. 5(a) is an example of a cross-sectional view of the flow path structure 100 according to the first embodiment, taken along the main flow direction of the first flow path 1 and the third flow path 3. The liquid passing through the second flow path 2 (hereinafter referred to as "Liquid A") is indicated by hatching, and the main flow direction of the liquid passing through the first flow path 1 and the third flow path 3 is indicated by arrows. Liquid A experiences flow separation below the step due to the widened step at the connection from the second flow path 2 to the first flow path 1. This separation is stretched downstream by the flow in the first flow path 1, generating a coaxial small vortex structure downstream where the two flows converge. Furthermore, a larger vortex (commonly referred to as a swirl) generated by the two convergences further stabilizes and reinforces the small vortex structure. Because the initial small vortex tends to form in the direction of the step, it is advantageous to generate it downstream in order to stretch the vortex structure downstream. Therefore, in the second flow path 2, the sub-flow path upstream of the first flow path 1 must be deep on the main flow path side, and the flow width must be wide. In this structure, small vortices are more smoothly elongated than when the bottom surface of the second flow path 2 is a uniformly shallow flow path of the flow path structure 100 and the top and bottom surfaces are parallel. This results in a more orderly vortex formed by liquid A immediately after merging with the liquid passing through the first flow path 1 (hereinafter referred to as "liquid B"). Furthermore, because the vortexes that can be generated within a limited flow path width are limited, excessive flow rates of liquid A result in some liquid A not being caught in the vortex, hindering rapid mixing. However, by shallowing the depth of the second flow path 2 downstream of the first flow path 1, the flow rate of liquid A flowing from the second flow path 2 to the first flow path 1 can be reduced to a level that allows liquid A to be caught in the vortex. Figure 5(b) is a cross-sectional view of the flow path structure 100 perpendicular to the main flow direction of the third flow path 3. The positions of the dashed lines in Figure 5(a) and the cross-sectional view in Figure 5(b) are shown to facilitate understanding of the concept of mixing. The actual degree of mixing may vary depending on various conditions, such as the liquid properties, temperature, flow velocity, and flow path dimensions. Immediately after joining the first flow path 1, liquid A is pushed along while swirling, and a substantially multi-layered concentric vortex as shown in the figure is formed in the third flow path 3. In the flow path structure 100 shown in this embodiment, the proportion of the substantially multi-layered concentric vortex as shown in the figure in the third flow path 3 is large, and the amount of liquid that does not form vortices is relatively small, so liquid A and liquid B are mixed quickly.

[0026] It is not essential that liquid A and liquid B are the same type of liquid, and they may have different properties including viscosity, temperature, flow rate, etc. The shape of the bottom surface of second flow path 2 may be designed to be linear or curved according to the properties of these two liquids.

[0027] In this way, the flow channel structure 100, which includes a main flow channel, a sub-flow channel, and a merging flow channel and has a structure in which the depth of the sub-flow channel varies along the width direction of the sub-flow channel, can quickly and efficiently mix the flows from the main flow channel and the sub-flow channel in the merging flow channel, further promoting the mixing of the two liquids.Furthermore, this can be achieved with a relatively simple structure.

[0028] The flow path structure 100 may be a tubular structure made of a resin such as acrylic, polyethylene glycol (PEG), ethylene, polypropylene, polycarbonate, or the like, glass, ceramic, or metal, or may be a flow path structure embedded in a solid such as a resin such as acrylic, polyethylene, polypropylene, polycarbonate, or the like, glass, ceramic, or metal, etc. When the flow path structure 100 is embedded in a solid, the liquid inlet ports located upstream of the first flow path 1 and the second flow path 2 and the liquid outlet located downstream of the third flow path 3 communicate with the outside of the solid.

[0029] It is preferable that the top surfaces of the first flow path 1, the second flow path 2, and the third flow path 3 are included in a single plane. When the top surface of the flow path structure 100 is made of a single flat plate, the flow paths can be easily sealed by forming the flow paths by pressing or cutting using a mold, and then covering the flow paths with the top surface.

[0030] The side surface of the second flow path 2 does not necessarily have to be perpendicular to the top surface. Fig. 6 is an example of a cross-sectional view of the flow path structure 100 according to the first embodiment, taken along the main flow direction of the first flow path 1 and the third flow path 3. As shown in Fig. 6, by making the side surface of the second flow path 2 located on the upstream side of the flow in the first flow path 1 oblique to the side surface of the second flow path 2 located on the downstream side of the flow in the first flow path 1, it becomes easier to manufacture the flow path structure 100, and mass productivity can be improved.

[0031] In the first embodiment, an example was described in which the flow path widths of the first flow path 1, the second flow path 2, and the third flow path 3 are constant, but the embodiment of the present invention is not limited to this, and the flow path width may change from upstream to downstream.

[0032] In this embodiment, the proportion of the flow that does not form a vortex in the third flow path 3 may be further reduced by further adjusting the flow rates in the first flow path 1 and the second flow path 2.

[0033] (First Modification) The same reference numerals are used to denote components common to the first embodiment, and descriptions of components with the same configurations and functions are omitted. The modified example will be described below.

[0034] FIG. 7 is an example of a cross-sectional view of the first flow path 1 and the third flow path 3 of the flow path structure 100 in this modified example, taken along the main flow direction. Unlike the first embodiment, the depth of the second flow path 2 at the point where the second flow path 2 connects to the first flow path 1 becomes deeper as it approaches the third flow path 3. The second flow path 2 shown in this modified example has a flow path width of 0.3 mm, a maximum flow path depth of 0.1 mm, and a minimum flow path depth of 0.0 mm. In this case, it is preferable that the average flow velocity of the liquid flowing through the second flow path 2 is approximately 0.1 m / s or more. Assuming that the liquid is similar to water and the characteristic length is the hydraulic diameter, the Reynolds number at around room temperature is approximately 30. Note that the second flow path 2 may be described as a sub-flow path in the flow path structure 100.

[0035] FIG. 8 is a schematic diagram showing the mixing of two liquids in this modified example. FIG. 8(a) is an example of a cross-sectional view taken along the mainstream direction of the first flow path 1 and the third flow path 3 of the flow path structure 100 in this modified example. Liquid A is indicated by hatching, and the mainstream direction of the liquids passing through the first flow path 1 and the third flow path 3 is indicated by arrows. In the second flow path 2, because the flow path depth on the upstream side of liquid A is small, small vortices caused by liquid A are distorted by the flow of liquid B and are swirled and swept away from the upstream to downstream of liquid B. FIG. 8(b) is a cross-sectional view of the flow path structure 100 in this modified example, taken perpendicular to the mainstream direction of the third flow path 3. The formation of vortices can promote mixing of the two liquids.

[0036] (Second Modification) The same reference numerals are used to denote components common to the first embodiment, and descriptions of components with the same configurations and functions are omitted. The modified example will be described below.

[0037] 9 is an example of a cross-sectional view of the flow path structure 100 according to this modification, taken along the main flow direction of the first flow path 1 and the third flow path 3. The second flow path 2 is indicated by hatching. As shown in the figure, the distance between the top surface and the bottom surface of the second flow path 2, i.e., the flow path depth, may be changed by inclining the top surface of the second flow path 2.

[0038] (Third Modification) The same reference numerals are used to denote components common to the first embodiment, and descriptions of components with the same configurations and functions are omitted. The modified example will be described below.

[0039] FIG. 10 is a schematic diagram showing a variation of the flow path structure 100 according to this modification. The arrow indicates the main flow direction of the flow entering from the second flow path 2. In the example shown in FIG. 10(a), the point of the second flow path 2 that is equidistant from the two flow path side surfaces (shown by the dashed line in the figure) coincides with the intersection point of the extensions of the wall surfaces of the first flow path 1 and the third flow path 3. Using this structure as a reference, consider a case where the position of the second flow path 2 is shifted toward the first flow path 1 or the third flow path 3. FIG. 10(b) shows the state where the second flow path 2 is shifted toward the first flow path 1. In FIG. 10(b), the end of the side surface of the second flow path 2 farther from the first flow path 1 coincides with the intersection point (corner) of the extensions of the wall surfaces of the first flow path 1 and the third flow path 3. In this case, most of the flow from the second flow path 2 does not collide with the side surface of the first flow path 1, as in the case of FIG. 10(a), and a separation vortex is formed in the third flow path 3. FIG. 10(c) shows the state where the second flow path 2 is further shifted toward the first flow path 1. If the second flow path 2 moves away from the mixing region 13, the flow from the second flow path 2 collides with the wall surface of the first flow path 1, disrupting the separation vortex. Therefore, when the second flow path 2 is shifted toward the first flow path 1, it is preferable to limit the shift amount to a distance L from the second opening 12 to the corner, which is approximately half the width of the second flow path 2 (as shown in (c)). (d) shows the state in which the second flow path 2 has shifted toward the third flow path 3. In (d), the end of the side surface of the second flow path 2 closer to the first flow path 1 coincides with the point (corner) where the extensions of the wall surfaces of the first flow path 1 and the third flow path 3 intersect. If the second flow path 2 shifts significantly toward the third flow path 3 and moves away from the mixing region 13, the flow from the second flow path 2 sticks to the side surface of the third flow path 3, making it difficult for separation vortexes to form. Therefore, when the second flow path 2 is shifted toward the third flow path 3, it is preferable to limit the shift amount to an extent that the corner is included in the second opening 12 (as shown in (d)).

[0040] (Second embodiment) The same reference numerals are used to denote components common to the first embodiment, and descriptions of components having the same configurations and functions are omitted. The second embodiment will be described below.

[0041] FIG. 11 is an example of a plan view of a flow channel structure 110. The flow channel structure 110 is a larger flow channel structure that partially includes the flow channel structure 100. The flow channel structure 110 further includes a flow channel having a branching structure and a merging structure on the opposite side of the third flow channel 3 from the first flow channel 1 and the second flow channel 2. In addition to the flow channel structure 100, the flow channel structure 110 also includes a mixing flow channel 4. The mixing flow channel 4 includes a branching section where one flow channel branches into two or more flow channels and a merging section where the branched flow channels rejoin. In FIG. 11, a section of the mixing flow channel 4 that is shallower than other sections and has parallel top and bottom surfaces is indicated by diagonal lines. Hereinafter, in this specification, a region shallower than other sections will be referred to as a "shallow section." Using a flow channel that includes a shallow section, such as the mixing flow channel 4 in the figure, can generate transverse vortices within the flow channel, thereby enabling better mixing and agitation of the fluids. The bottom or top surface of the second flow path 2 is inclined in the same manner as in the first embodiment, allowing the liquids injected into the first flow path 1 and the second flow path 2 to be quickly mixed in the third flow path 3.

[0042] Although the drawing shows the mixing flow channel 4 with a predetermined section as a shallow section, the shape of the mixing flow channel 4 is not limited to this. For example, the section between the branching section and the merging section may be sloping along the pipe axis of the flow channel, or the section between the branching section and the merging section may have a curved structure.

[0043] (Third embodiment) The same reference numerals are used to denote components common to the first and second embodiments, and descriptions of components having the same configurations and functions are omitted. The third embodiment will be described below.

[0044] FIG. 12 is a schematic diagram of an example of a flow channel structure 100 used in combination with a plurality of mixing channels 4, etc. Hereinafter, a unit formed by combining a plurality of mixing channels 4 and a flow channel structure equivalent to the mixing channels 4 will be described as a "flow channel structure unit." FIG. 12(a) illustrates an example in which three mixing channels 4 are connected in series. As shown in the figure, the flow channel structure unit 201 may be provided with an outlet 30 on the downstream side that can discharge liquid to the outside of the flow channel structure unit 201. By connecting a plurality of mixing channels 4 in series in this way, repeated vortices can be generated, enabling more rapid mixing of different types of liquids.

[0045] 12(a), the flow channel structure unit 202 shown in FIG. 10(b) includes a mixing channel 5. The position of the shallow portion of the mixing channel 5 is different from that of the mixing channel 4, but the other configurations are the same as those of the mixing channel 4. The mixing channel 5 can also be said to have a structure that is line-symmetrical with respect to the mixing channel 4, with the third channel 3 as the axis. The flow channel structure unit 202, which includes a structure in which the mixing channels 4 and the mixing channels 5 that are line-symmetrical with respect to the third channel 3 as the axis are alternately arranged, can mix the two types of liquids that have flowed in from the flow channel structure 100 more evenly.

[0046] Although the number of mixing channels included in the channel structure units 201 and 202 shown in the drawing is three, the number of mixing channels may be one or two, or may be four or more.

[0047] (First Modification) The same reference numerals are used to denote components common to the second embodiment, and explanations of components with the same configurations and functions are omitted. The following describes the modified example.

[0048] FIG. 13 is a schematic diagram of an example of a combination of the flow channel structure 100 and multiple mixing channels 4. FIG. 13 illustrates an example in which three mixing channels 4 are arranged and connected in parallel. The flow channel structure unit 203 has a branching section downstream of the third flow channel 3, and each branching point has a mixing channel 4. The liquid is branched upstream, passes through multiple mixing channels 4, and then merges back into a single channel downstream. This arrangement can reduce the resistance to liquid transport even when the flow rate is high, compared to a serial arrangement. When a liquid transport pump is used to transport liquid toward the flow channel structure unit 203, the load on the pump can be reduced.

[0049] (Second Modification) The same reference numerals are used to denote components common to the second embodiment, and explanations of components with the same configurations and functions are omitted. The following describes the modified example.

[0050] FIG. 14 is a schematic diagram illustrating an example of a combination of the flow channel structure 100 and multiple mixing channels 4. FIG. 14 illustrates a structure that combines a series arrangement and a parallel arrangement. In this case, the resistance to liquid transport can be adjusted and the mixing effect can be enhanced. For example, the flow channel structure unit 204 shown in FIG. 14 includes four flow channel structure units each having two mixing channels 4 arranged in series, and these four flow channel structure units are arranged in parallel. Furthermore, in the portion where the fluids converge downstream of the parallel flow channel structure units, it is preferable that at least one flow channel has a structure in which the depth of the flow channel varies in the width direction of the flow channel, as with the second flow channel 2, to promote mixing and mixing. The flow channel structure that combines a series arrangement and a parallel arrangement is not limited to the example shown in FIG. 14 and can be modified depending on the type or application of the fluid.

[0051] (Fourth embodiment) In this embodiment, a method for manufacturing the flow path structure 100 and flow path structure units 201 to 204 (hereinafter collectively referred to as "flow path structure 100") described in the first to third embodiments will be described below with reference to Fig. 15. As shown in Fig. 15(a), the flow path structure 100 includes a substrate 102 having a groove 101 formed therein that functions as a flow path, and a plate-like lid portion 103 joined to the substrate 102 so as to cover the top surface of the groove 101.

[0052] The material of the substrate 102 may be selected appropriately depending on the application from resins such as acrylic, polyethylene, polypropylene, and polycarbonate, glass, ceramics, or metal. For example, if the flow path structure 100 is for medical use, cycloolefin polymer (COP) is also a preferred example. If the flow path structure 100 is to be reused multiple times, ceramics such as glass and quartz are preferred due to their stability, and if temperature and other factors are to be adjusted, metals with corrosion-resistant surfaces may be used. The grooves 101 correspond to the first flow path 1, the second flow path 2, and the third flow path 3, and can be formed, for example, by pressing or cutting a bulk solid using a mold. The grooves 101 in the areas corresponding to the shallow portions may be formed or cut shallower than in other areas.

[0053] The material of the lid portion 103 can be, for example, the same material as that described for the substrate 102. The lid portion 103 can be, for example, in the form of a plate. Alternatively, a thin film-like lid portion 104 may be used as shown in FIG. 15(b).

[0054] The film-like lid portion 104 can be fitted with a sensor terminal 105 for monitoring the state of the fluid. Alternatively, the film-like lid portion 104 can be given various functions or properties, such as high thermal conductivity or the ability to perform specific processing on specific substances (not shown).

[0055] If there is a concern that the film-shaped lid portion 104 may bulge due to internal pressure, the bulge may be suppressed by pressing a pressure plate 106 against the film-shaped lid portion 104 from above, as shown in Fig. 22(c). The pressure plate 106 may include a heat medium flow path 107 for heat exchange disposed therein, or an electric terminal (not shown) having a sensor function.

[0056] In this way, the flow channel structure 100 can be manufactured by a simple procedure of forming the groove 101 in the substrate 102 and joining the lid portion 103 or the film-like lid portion 104. Therefore, for example, it is not necessary to form grooves in both the substrate 102 and the lid portion 103, and therefore it is not necessary to precisely align the two, which makes it highly suitable for mass production.

[0057] Furthermore, a channel with a variable depth may be formed by setting the depth of the groove 101 at the location where the channel depth becomes smaller to the same depth as the other portions, and attaching a film-like lid 104 whose thickness varies depending on the position to the corresponding location. That is, in a channel formed in this manner, the channel depth varies because the thickness of the top surface varies depending on the position. With this structure, as with a structure in which the shape of the bottom surface varies depending on the position, highly uniform mixing can be achieved.

[0058] (Fifth embodiment) In this embodiment, a fluid agitation method is provided. The fluid agitation method includes flowing a fluid to be agitated through the fluid flow path structure 100 of the embodiment. According to the fluid agitation method, by using the fluid flow path structure 100 of the embodiment, the fluid can be more effectively mixed and agitated.

[0059] When the flow channel structure 100 of the first to fourth embodiments is used, this method includes flowing a liquid so that the liquid passes through the first flow channel 1 or the second flow channel 2 and then flows through the third flow channel 3. In this method, the liquid flowing in the flow channel may be two or more different types of fluid, and the flow channel structure 100 of the first to fourth embodiments can quickly mix and stir these fluids.

[0060] (Sixth embodiment) In this embodiment, a method for producing lipid particles 400 encapsulating a drug 402 using the flow channel structure 100 of the embodiment will be described.

[0061] First, a lipid particle 400 produced by this method will be described. Fig. 16 is a diagram showing an example of a lipid particle of this embodiment. As shown in Fig. 16, the lipid particle 400 is made of a lipid membrane formed by arranging lipid molecules, and has a hollow, approximately spherical shape. A drug 402 is encapsulated in the lumen 401 of the lipid particle 400. The lipid particle 400 can be used, for example, to deliver the drug 402 into a cell.

[0062] FIG. 17 is a flowchart showing an example of a method for producing lipid particles 400. The method for producing lipid particles 400 includes the following steps: (1) using the flow channel structure 100 of the embodiment, flowing a first solution containing lipids, which are the material for the lipid particles 400, in an organic solvent through one of the inlets (first inlet) located upstream of the first flow channel 1; (2) flowing a second solution containing a drug 402 in an aqueous solvent through another inlet (second inlet) located upstream of the first flow channel 1 to mix the first solution with the second solution to obtain a mixed solution (mixing step S1); (3) reducing the concentration of the organic solvent in the mixed solution to particulate the lipids to produce lipid particles 400 encapsulating the drug 402 (particulation step S2); and (4) concentrating the solution of lipid particles 400 (concentration step S3). FIG. 18 is a diagram showing an example of a flow channel structure 300 used in the method for producing lipid particles of the present embodiment. This production method can be performed using, for example, the flow channel structure 300. The mixing step S1 is performed in region 310 in the figure, and the particulation step S2 is performed in region 320.

[0063] An example of the procedure of this manufacturing method will be described below.

[0064] First, a first solution and a second solution are prepared. The first solution contains lipids in an organic solvent. The lipids are the material that constitutes the lipid particles 400. The second solution contains a drug 402 in an aqueous solvent.

[0065] ·Mixing process S1 The first solution and the second solution are mixed. The second solution can be prepared by mixing a drug 402 with any of the above aqueous solvents selected according to its type. The drug 402 is a nucleic acid or the like, and a non-nucleic acid drug 402 includes, for example, a protein, a peptide, an amino acid, another organic compound, or an inorganic compound as an active ingredient. The drug 402 may be, for example, a therapeutic drug or a diagnostic drug for a disease. However, the drug 402 is not limited to these and may be any substance that can be encapsulated in the lipid particle 400.

[0066] The drug 402 may further include, as needed, reagents such as a pH adjuster, an osmotic pressure adjuster, and / or a drug activator. The pH adjuster may be, for example, an organic acid such as citric acid or a salt thereof. The osmotic pressure adjuster may be, for example, a sugar or an amino acid.

[0067] The first solution can be prepared by mixing a lipid with an organic solvent. The lipid can be, for example, a lipid that is a major component of a biological membrane. Alternatively, the lipid can be artificially synthesized. The lipid can include, for example, a base lipid such as a phospholipid or sphingolipid, e.g., diacylphosphatidylcholine, diacylphosphatidylethanolamine, ceramide, sphingomyelin, dihydrosphingomyelin, cephalin, or cerebroside, or a combination thereof.

[0068] The organic solvent of the first solution is, for example, ethanol, methanol, isopropyl alcohol, ether, chloroform, benzene, or acetone.

[0069] The first solution and the second solution are mixed in region 310 shown in Fig. 18. In Fig. 18, the structure between region 310 and region 320 is omitted, but in reality, any flow path structure unit may be included between region 310 and region 320.

[0070] ·Particleization process S2 Next, in the particulation step S2, the concentration of the organic solvent in the mixed solution is reduced. For example, it is preferable to relatively reduce the organic solvent concentration by adding a large amount of aqueous solution to the mixed solution. For example, an aqueous solution three times the volume of the mixed solution is added to the mixed solution. The aqueous solution can be the same as the aqueous solvent used in the first solution. By reducing the organic solvent concentration, the lipids are particulated, and lipid particles 400 encapsulating the drug 402 can be produced. As a result, a lipid particle solution containing lipid particles 400 is obtained.

[0071] Region 320 is, for example, a Y-shaped flow path. The upstream end of one of the branched Y-shaped flow paths is connected to the most downstream end of region 310, from which the mixed liquid is supplied. The upstream end of the other flow path is provided with, for example, an aqueous solution inlet, from which the aqueous solution flows. As a result, in region 320, where the mixed liquid that has passed through region 310 and the aqueous solution injected from the aqueous solution inlet join, the aqueous solution is mixed with the mixed liquid. As a result, the lipids are granulated, and lipid particles 400 encapsulating the drug 402 are generated, and a lipid particle solution containing the lipid particles 400 is obtained.

[0072] The particulate forming step S2 does not necessarily have to be performed using a flow path, and for example, an aqueous solution may be added to the mixed liquid collected in the container.

[0073] In this manner, lipid particles 400 can be produced.

[0074] ·Concentration process S3 The lipid particle production method of the embodiment may further include concentrating the lipid particle solution as needed (concentration step S3). Concentration can be performed, for example, by removing a portion of the solvent and / or excess lipid and drug 402 from the lipid particle solution. Concentration can be performed, for example, by ultrafiltration. For ultrafiltration, it is preferable to use an ultrafiltration filter with a pore size of 2 nm to 100 nm. For example, Amicon (registered trademark) Ultra-15 (Merck) or the like can be used as the filter.

[0075] The flow of fluid within the flow path, the injection of fluid into the flow path, the removal of fluid from a tank and / or the storage of lipid particle solutions in a container can be performed, for example, by a pump or extrusion mechanism configured and controlled so that these operations are performed automatically.

[0076] If the drug 402 is a nucleic acid, a condensation step of condensing the nucleic acid (drug 402) may be performed before the mixing step S1. The nucleic acid drug 402 may be, for example, a nucleic acid containing DNA, RNA and / or other nucleotides, such as mRNA of a specific gene, DNA encoding a gene, DNA containing a gene expression cassette containing a gene and other sequences for expressing the gene, such as a promoter, or a vector.

[0077] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims.

[0078] Furthermore, in this specification, the pipe axis direction and the direction of the main flow of the flow path structure have been described as being as shown by the arrows in FIG. 1, but the pipe axis direction and the direction of the main flow of the flow path structure are not limited to this.

[0079] Furthermore, the "tube axis" described in this specification may refer to, for example, the central axis of a flow channel. However, this definition does not limit the interpretation of the "tube axis" in a narrow sense, and it should be interpreted appropriately without detracting from the spirit of the invention described in the embodiments.

[0080] Furthermore, the embodiments and modifications described in this specification can be combined in any manner.

[0081] Furthermore, the present disclosure includes examples according to the following appendices.

[0082] [Appendix 1] a first flow path; a second flow path connected to the first flow path; a third flow path connected to the first flow path and the second flow path; When the distance between the top surface and the bottom surface of the flow path is defined as the flow path depth, the flow path depth of the second flow path at an opening where the first flow path is connected to the second flow path is not constant, and the maximum value of the flow path depth of the second flow path at the opening is smaller than the flow path depth of the first flow path. Flow path structure.

[0083] [Appendix 2] The flow path depth of the second flow path changes at a constant gradient. 2. The flow path structure of claim 1.

[0084] [Appendix 3] The maximum value of the flow path depth of the second flow path is ½ or less of the flow path depth of the first flow path. 3. A flow path structure according to any one of appendices 1 and 2.

[0085] [Appendix 4] The top surfaces of the first flow path, the second flow path, and the third flow path are included in a single plane. 4. A flow path structure according to any one of claims 1 to 3.

[0086] [Appendix 5] The first flow path, the second flow path, and the third flow path are formed by cutting or pressing a bulk solid. 5. A flow path structure according to any one of claims 1 to 4.

[0087] [Appendix 6] a flow path depth of the second flow path at a location where a flow path side surface of the second flow path and a flow path side surface of the first flow path contact each other is greater than a flow path depth of the second flow path at a flow path wall surface on the opposite side across the second flow path at a location where a flow path side surface of the second flow path and a flow path side surface of the first flow path contact each other. 6. A flow path structure according to any one of claims 1 to 5.

[0088] [Appendix 7] The first flow path and the second flow path are symmetrical with respect to the third flow path. 7. A flow path structure according to any one of claims 1 to 6.

[0089] [Appendix 8] an angle formed between a side surface of the first flow path and a side surface of the third flow path, and an angle formed between a side surface of the second flow path and a side surface of the third flow path are each 30° or more and 60° or less; 8. A flow path structure according to any one of claims 1 to 7.

[0090] [Appendix 9] the flow path depth is equal to or less than the flow path widths of the first flow path, the second flow path, and the third flow path; 9. A flow path structure according to any one of claims 1 to 8.

[0091] [Appendix 10] The cross-sectional area of ​​the flow path included in the flow path structure perpendicular to the pipe axis direction of the flow path is 100 mm 2 Below is the 10. The flow path structure according to any one of claims 1 to 9.

[0092] [Appendix 11] The first flow path and the second flow path are provided at one end, and the second flow path further comprises a flow path having at least one of a branch structure and a junction structure at the other end. 11. A flow path structure according to any one of claims 1 to 10.

[0093] [Appendix 12] a flow path structure according to Supplementary Note 1; A fluid structure unit comprising: a flow path having a plurality of branch structures and a confluence structure.

[0094] [Claim 13] A method for producing lipid particles encapsulating a drug using the flow channel structure according to any one of Supplementary Notes 1 to 10, comprising: a step of flowing a first solution containing lipids, which are materials for the lipid particles, in an organic solvent from a first inlet located upstream of the first flow path, and flowing a second solution containing the drug in an aqueous solvent from a second inlet located upstream of the first flow path, thereby mixing the first solution and the second solution to obtain a mixed solution; and reducing the concentration of the organic solvent in the mixed solution to particulate the lipids, thereby producing lipid particles encapsulating the drug. [Explanation of symbols]

[0095] 1 First flow path 2 Second flow path 3 Third flow path 4 Mixing channel 5 Mixing channel 11 First opening 12 Second opening 13 Mixed area 30 Exit section 100 Flow path structure 101 Groove 102 Circuit Board 103 Lid 104 Lid 105 Sensor terminal 106 board 107 Heat transfer medium flow path 110 Flow path structure 201~204 Flow path structure unit 300 Flow path structure 310 areas 320 areas 400 lipid particles 401 Lumen 402 Drugs

Claims

1. A first flow path; a second flow path connected to the first flow path; a third flow path connected to the first flow path and the second flow path; When the distance between the top surface and the bottom surface of the flow path is defined as the flow path depth, the flow path depth of the second flow path at an opening where the first flow path is connected to the second flow path is not constant, and the maximum value of the flow path depth of the second flow path at the opening is smaller than the flow path depth of the first flow path. Flow path structure.

2. The flow path depth of the second flow path changes at a constant gradient. The flow path structure according to claim 1 .

3. The maximum value of the flow path depth of the second flow path is equal to or less than half of the flow path depth of the first flow path. The flow path structure according to claim 1 .

4. The top surfaces of the first flow path, the second flow path, and the third flow path are included in a single plane. The flow path structure according to claim 1 .

5. The first flow path, the second flow path, and the third flow path are formed by cutting or pressing a bulk solid. The flow path structure according to claim 1 .

6. a flow path depth of the second flow path at a location where a flow path side surface of the second flow path and a flow path side surface of the first flow path contact each other is greater than a flow path depth of the second flow path at a flow path wall surface on the opposite side across the second flow path at a location where a flow path side surface of the second flow path and a flow path side surface of the first flow path contact each other; The flow path structure according to claim 1 .

7. The first flow path and the second flow path are symmetrical with respect to the third flow path. The flow path structure according to claim 1 .

8. an angle formed between a side surface of the first flow path and a side surface of the third flow path, and an angle formed between a side surface of the second flow path and a side surface of the third flow path are each 30° or more and 60° or less; The flow path structure according to claim 1 .

9. the flow path depth is equal to or less than the flow path widths of the first flow path, the second flow path, and the third flow path; The flow path structure according to claim 1 .

10. The cross-sectional area of ​​the flow path included in the flow path structure perpendicular to the pipe axis direction of the flow path is 100 mm ２ Below is the The flow path structure according to claim 1 .

11. the first flow path and the second flow path are provided at one end, and the other end of the flow path has at least one of a branch structure and a junction structure; The flow path structure according to claim 1 .

12. The flow path structure according to claim 1 ; A fluid structure unit comprising: a flow path having a plurality of branch structures and a confluence structure.

13. A method for producing lipid particles encapsulating a drug using the flow channel structure according to any one of claims 1 to 10, comprising: a step of flowing a first solution containing lipids, which are materials for the lipid particles, in an organic solvent from a first inlet located upstream of the first flow path, and flowing a second solution containing the drug in an aqueous solvent from a second inlet located upstream of the first flow path, thereby mixing the first solution and the second solution to obtain a mixed solution; and reducing the concentration of the organic solvent in the mixed solution to particulate the lipids, thereby producing lipid particles encapsulating the drug.

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