JP5374446B2 - Microdroplet weighing structure, microfluidic device, and microdroplet weighing method - Google Patents

Description

  The present invention relates to a microdroplet weighing structure for weighing a predetermined amount of microdroplets called a microfluid, and more particularly, to quantitatively weigh microdroplets by controlling gas pressure. The present invention relates to a microdroplet weighing structure that enables the microdroplet, a microfluidic device including the microdroplet weighing structure, and a microdroplet weighing method.

  In recent years, microfluidic devices having a trace liquid control mechanism have attracted attention in specimen analysis and combinatorial compound synthesis. The microfluidic device is configured using a substrate having a size that can be easily handled by hand, for example. A fine channel structure for conveying a specimen, a reagent, a diluent, or the like is formed in the substrate. Further, in this fine channel structure, a reagent storage unit, a sample supply unit, a diluent storage unit, a reaction chamber, a mixing unit, a liquid feeding mechanism, a detection unit, and the like are appropriately provided as necessary.

A typical thickness of the substrate is about 0.5 to 10 mm. The plane area of the substrate is several hundred cm ² or less.

  The channel width of the fine channel structure is usually very thin, about 3 μm to 5 mm. A minute amount of droplets, that is, microfluids are transported in such a fine channel.

  Such microfluidic devices include human and animal body fluids such as blood, cerebrospinal fluid, tears or saliva, excrements, decomposed extracts from tissue fragments, seawater and fresh water, soil extracts, agricultural products, marine products or processed foods, etc. And liquid samples used for natural science research and biochemistry research are used for detection and quantitative measurement. It is also used in combinatorial chemistry for systematically synthesizing a series of related compounds, searching for crystallization conditions, searching for chemical reaction conditions, and a series of related compounds. In order to obtain accurate results with the microfluidic device, it is necessary to quantitatively handle the specimen or reagent to be used in the microfluidic device. Therefore, various microdroplet weighing structures used for microfluidic devices have been proposed.

  In the following Patent Document 1, the first flow path and the second flow path extending in a predetermined direction, and the first flow path and the second flow path are opened in the flow path walls, respectively. A trace liquid weighing structure having a third channel connecting the second channel and the second channel is disclosed. Here, the third flow path is narrower than the first flow path and the second flow path. The liquid introduced into the first flow path is drawn from the first flow path to the third flow path by capillary action, and then the liquid remaining in the first flow path is removed. Accordingly, it is possible to weigh a minute amount of liquid droplets according to the volume of the third flow path.

  Patent Document 2 below discloses a microdroplet weighing structure in a microchip having a fine flow path, that is, a microchannel structure. Here, a first flow path serving as a receiving volume section for receiving liquid, a second flow path serving as a delivery volume section for sending liquid to the first flow path, a first flow path, and a first flow path And a third flow path connecting the two flow paths. The third flow path is thinner than the first and second flow paths. The ratio of the perimeter of the cross section to the area of the cross section of the first flow path is substantially equal to the ratio of the perimeter of the cross section to the area of the cross section of the second flow path. The ratio of the circumferential length of the cross section to the area of the cross section of the path is set to be not less than 2 times and not more than 10 times the ratio in the second flow path.

  In the micro liquid weighing structure described in Patent Document 1 and Patent Document 2, it is said that the micro liquid droplet can be accurately weighed only by adjusting the on / off of the inflow of the gas that drives the micro liquid droplet. ing.

JP 2002-357616 A Japanese Patent No. 3782796

  However, the microdroplet weighing structure described in Patent Document 1 can only weigh microdroplets in an amount that is guided by capillary action. That is, it was not possible to weigh out a small amount of droplets exceeding the amount that can be drawn by capillary action.

  On the other hand, the microdroplet weighing structure described in Patent Document 2 has a problem that the same amount or more of liquid as the microdroplet to be weighed remains in the first flow path. Therefore, for example, when trying to obtain a two-component mixed liquid, it is difficult to mix in a large ratio such that the mixing ratio, which is the ratio of the volume of the larger droplet to the volume of the smaller droplet, is 10 times or more. Met. In addition, since many droplets remain in the first flow path, a useless sample is necessary, and it was impossible to perform analysis with high accuracy using a very small amount of sample.

  The object of the present invention is to reduce the amount of droplets left in the weighing process, and to reduce the amount of droplets left behind during weighing in view of the current state of the prior art described above. A microdroplet weighing structure and a microfluidic device provided with the microdroplet weighing structure, which can be suitably used even in the case of mixing at a large ratio exceeding 10 times when mixing droplets And providing a method for weighing microdroplets.

  A microdroplet weighing structure according to the present invention is a structure for weighing microdroplets, and includes a substrate and a channel provided in the substrate, and the channel is a droplet. And a first flow channel capable of transporting a droplet having one end connected to the inlet to which gas is supplied and the other end connected to the discharge port, a first branch part in the middle of the first flow channel, A first flow path comprising a second flow path that is connected to a second flow path that is located downstream of the first flow path and is a gas-selective flow path. The volume of the first flow path portion connecting the portion and the second branch portion is made equal to the volume of the minute droplets to be weighed.

  In a specific aspect of the microdroplet weighing structure according to the present invention, the flow path length of the first flow path portion from the first branch portion to the second branch portion is the second flow path. It is longer than twice the flow path length and shorter than 1000 times.

  In another specific aspect of the microdroplet weighing structure according to the present invention, a third branch portion is provided in the middle of the first flow path portion between the first branch portion and the second branch portion. One end of the third flow path is connected to the third branch portion, and the third flow path has a Laplace valve. Therefore, after the first flow path portion between the first branch portion and the first branch portion is filled with a minute droplet, one of the introduction port or the discharge port is closed and the other non-blocked discharge port is closed. By applying a gas pressure from the outlet or the introduction port, a minute droplet filled in the channel portion can be quickly taken out from the third channel.

  In still another specific aspect of the microdroplet weighing structure according to the present invention, the Laplace valve is composed of a narrow channel that has a hydraulic equivalent diameter of 40 μm or less. In this case, the Laplace valve can be easily formed by using a part of the third channel as a narrow channel.

  In still another specific aspect of the microdroplet weighing structure according to the present invention, the microdroplet weighing structure further includes a valve that is provided in the middle of the second flow path and opens and closes the second flow path. In this case, without providing the third flow path, with the minute liquid droplets being put out in the flow path portion, the second flow path is closed and only the gas pressure is applied from the introduction port. The liquid droplets weighed in the flow path portion can be taken out from the discharge port.

  In still another specific aspect of the microdroplet weighing structure according to the present invention, the first flow channel has an absolute value of a rate of change along the length direction of the flow channel cross-sectional area of 20% or more. The partial flow path is included. In this case, since a partial cross-sectional area of the first flow path is widened, a large volume can be weighed with a short flow path length, and a liquid flows inside the first flow path. The pressure loss at the time can be reduced. For this reason, the pressure difference between the first branch portion and the second branch portion is reduced, and it is possible to prevent the liquid from accidentally flowing into the second flow path, thereby making the operation of the weighing mechanism more reliable. it can.

  In the microdroplet weighing structure according to the present invention, the inlet of another microdroplet weighing structure configured according to the present invention is connected to the downstream side of the discharge port of the microdroplet weighing structure of the present invention. Has been. In this case, at least two microdroplet weighing structures of the present invention are connected in series. That is, the introduction port of the second microdroplet weighing structure is connected to the discharge port of the first microdroplet weighing structure. Since the residual liquid after the first weighing by the first microdroplet weighing structure is introduced into the second microdroplet weighing structure and the second weighing is performed, a plurality of trace liquids are obtained. Drops can be efficiently weighed.

  In still another specific aspect of the microdroplet weighing structure according to the present invention, an exhaust passage connected to the discharge port is further provided.

  In still another specific aspect of the microdroplet weighing structure according to the present invention, the microdroplet mixing unit further includes a microdroplet mixing unit, and at least two microdroplet weighing units are connected to the microdroplet mixing unit. At least one microdroplet weighing structure of at least two microdroplet weighing structures is a microdroplet weighing structure configured according to the present invention, and at least two microfluids in the microdroplet mixing section. Among the plurality of droplets supplied from the drop weighing structure, the volume ratio of the smallest droplet to the largest droplet is 1 to 10 or more. Accordingly, it is possible to perform mixing at an accurate mixing ratio in mixing in which the mixing ratio, that is, the ratio of the larger droplet volume to the smaller droplet volume exceeds 10 times.

  A microfluidic device according to the present invention includes a microdroplet weighing structure configured according to the present invention. Therefore, according to the present invention, it is possible to accurately and easily weigh microscopic droplets, so that detection / quantitative measurement and the like in a microfluidic device can be performed with high accuracy.

  A microdroplet weighing method according to the present invention is a microdroplet weighing method using a microdroplet weighing structure configured according to the present invention, wherein the microfluidic droplet weighing method is provided from the inlet to the first channel. Introducing a microdroplet having a volume larger than the volume of the first flow path portion from the first branch portion to the second branch portion by a gas pressure; and the rear end of the introduced microdroplet is After the discharge from the discharge port, the balance remaining liquid separated from the liquid droplets weighed in the partial flow path for subsequent weighing reaches the first branching portion and closes the discharge port. And a step of discharging the minute droplets stored in the first flow path portion between the first branch portion and the second branch portion from the third flow path by gas pressure. .

  In the microdroplet weighing structure according to the present invention, a minute amount having a volume larger than the volume of the first channel portion connecting the first branch portion and the second branch portion from the inlet to the first channel. When the droplet is introduced and moved by the gas pressure and the trailing end of the minute droplet reaches the first branch portion, the gas flows into the second channel which is the gas selective channel, The droplets are divided at the two branch portions, and a minute amount of the droplets corresponding to the volume is reliably weighed in the first flow path portion between the first branch portion and the second branch portion. be able to. Accordingly, it is possible to reliably weigh a minute amount of liquid droplets with a relatively simple structure and according to a predetermined volume, that is, a volume of a flow path portion connecting the first branch portion and the second branch portion. . In Patent Document 1, only a minute amount of a droplet that can be pulled in due to a capillary phenomenon can be weighed, whereas the minute droplet weighing structure of the present invention does not have such a restriction. Therefore, it is possible to reliably weigh a small volume of a large volume of liquid droplets that are difficult to weigh by droplet operation by drawing due to capillary action.

  In addition, since a large volume of minute droplets can be accurately and easily weighed, even in a large ratio mixing application in which the mixing ratio of the minimum amount of droplets to the maximum amount of droplets exceeds 10 times, The microdroplet weighing structure according to the present invention can be suitably applied. That is, even in the case of the above mixing ratio exceeding 10 times, a large number of minute droplets can be easily and accurately weighed and supplied to the mixing unit.

1 is a schematic plan view for explaining the principle of a microdroplet weighing structure according to a first embodiment of the present invention. In the 2nd Embodiment of this invention, it is a typical top view for demonstrating the modification by which the 3rd flow path is connected to the 1st flow path. (A)-(i) is each typical top view for demonstrating the process of weighing the trace amount droplet in the trace amount weighing structure shown in FIG. (A)-(f) is each typical top view for demonstrating the microdroplet weighing method using the microdroplet weighing structure of 3rd Embodiment of the microdroplet weighing structure of this invention. It is. (A)-(d) is each typical top view for demonstrating the other modification of the microdroplet weighing structure of this invention. It is a typical top view for demonstrating the microdroplet weighing structure which concerns on the 4th Embodiment of this invention provided with the timing control mechanism. FIG. 10 is a schematic plan view showing a microdroplet weighing structure including a mixing unit according to a fifth embodiment of the microdroplet weighing structure according to the present invention. FIG. 10 is a schematic plan view for explaining a sixth embodiment of a microdroplet weighing structure according to the present invention, and describes a microdroplet weighing mechanism that enables large-ratio mixing with automatic timing control; FIG. 1 is a schematic plan view showing an example of a microfluidic device provided with a microdroplet weighing structure according to the present invention.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention.

  FIG. 1 is a schematic plan view for explaining a microdroplet weighing structure according to an embodiment of the present invention.

  The microdroplet weighing structure that is the subject of the present invention is a structure for weighing a predetermined amount of microdroplets, and in fact, a flow path for feeding microdroplets into the substrate is formed. The The relationship between the substrate and the flow path will be described by taking a microfluidic device described later as an example.

  FIG. 1 is a schematic plan view showing a microdroplet weighing structure of the present invention provided in a substrate. As shown in FIG. 1, the microdroplet weighing structure 1 has a first flow path 4 having one end connected to the inlet 2 and the other end connected to the outlet 3. Trace droplets and gas are supplied from the inlet 2 to the first flow path 4.

  The first flow path 4 is a flow path capable of transporting droplets. In other words, the inner surface has a property of being able to carry a microfluid which is a minute droplet. The entire inner surface of the first flow path 4 may be hydrophilic, or a part of the first flow path 4 may be subjected to a water-repellent treatment within a range that does not impede the transport of a minute droplet. The width of the first flow path is about 30 μm to 5 mm. Note that the height of the first flow path 4 is also about 30 μm to 5 mm. The first flow path 4 is not limited to a rectangular cross section, and the cross section may be an arbitrary shape such as a circle, an ellipse, a semicircle, or a triangle. When the cross section is circular, the channel diameter may be about 30 μm to 5 mm. In the case of other shapes, the flow path diameter may be about 30 μm to 5 mm as a hydraulic equivalent diameter. Here, the hydraulic equivalent diameter De is a size defined by De = 4 × (flow cross-sectional area) / (wetting side length of the flow path). The equivalent hydraulic diameter is also called the equivalent hydraulic diameter.

  The second flow path 5 is provided so as to connect the first branch portion 6 and the second branch portion 7 provided in the first flow path 4. That is, in the first flow path 4, the first branch portion 6 is provided on the downstream side of the introduction port 2, and one end of the second flow path 5 is connected to the first branch portion 6. . A second branch portion 7 is provided downstream of the first branch portion 6 and upstream of the discharge port 3. The end of the second flow path 5 opposite to the end connected to the first branch 6 is connected to the second branch 7.

  Now, let the 1st flow path part from the 1st branch part 6 to the 2nd branch part 7 be the flow path part 4A. In the present embodiment, the volume of the flow path portion 4A is equal to the volume of a minute droplet to be weighed. That is, the volume of the flow path portion 4A is determined so as to be equal to the volume of the minute droplets to be weighed.

  The second channel 5 is a gas selective channel. That is, it is a channel through which gas passes but does not flow under the working pressure of the microdroplet weighing structure. Since the second flow path 5 is a gas selective flow path, the liquid droplet introduced from the inlet 2 to the first flow path 4 does not reach the second flow path 5 even if it reaches the first branching portion. It moves toward only the flow path portion 4A without going to it.

  The working pressure here refers to the pressure experienced by the first branching section from the passage of the liquid droplet tip to the passage of the gas-liquid interface to the first branching section to which the second flow path 5 is connected. It is a range, and usually indicates a range of pressure minus 1 Pa to 100 Pa. Under special conditions, the pressure may be higher than this, but even under special conditions, the pressure is at most about 10 kPa. In addition, the pressure of the 1st branch part here is a gauge pressure on the basis of the pressure of the 2nd branch part.

  In order for the second flow path 5 to be a gas-selective flow path through which gas passes but liquid droplets do not flow, a method in which the whole or at least a part of the inner surface of the second flow path 5 is a water repellent surface, At least part of the second channel 5 connected to the first branch and the second branch connected to the first channel is more than the channel portion 4A of the first channel. It can be configured using means such as a method of making it much smaller.

  Here, the water repellent surface refers to a surface having a contact angle θ between water and the channel surface in a range of 50 ° <θ <180 °. Such a water-repellent surface can be formed by forming the surface with a hydrophobic material and by providing a surface structure at a submicron level. By making the inner surface of the second channel a water-repellent surface, it is configured so that water does not enter the second channel at a pressure that introduces a minute droplet into the inlet of the minute droplet weighing mechanism. Can do.

  The opening diameter of the portion where the second flow path 5 is connected to the first flow path 4 is usually about 0.1 μm to 40 μm. There may be a plurality of openings where the second flow path 5 is connected to the first flow path 4. More specifically, the second flow path 5 may be connected to the first flow path 4 with a porous membrane interposed.

  The length of the second flow path 5 is about 5 μm to 5 mm.

  In addition, in the 2nd flow path 5, the diameter expansion part which a cross-sectional area spreads in the middle of a flow path may be provided, and the valve structure may be added. For example, an open / close valve that can be operated from the outside can be provided. Although there is no restriction | limiting in the kind of on-off valve, the on-off valve which obstruct | occludes a gas selection flow path with the liquid flow path provided in the gas selection flow path can be implement | achieved simply.

  In the microdroplet weighing structure 1 of the present embodiment, a microdroplet having a volume larger than the volume of the channel portion 4A is guided from the inlet 2 to the first channel 4. Thereafter, gas is supplied from the introduction port 2 by a pump or the like (not shown), and the introduced micro-droplet is moved. The microdroplet moves along the first flow path 4 toward the discharge port 3, but the second flow path 5 is a gas-selective flow path. Does not enter and moves through the flow path portion 4A.

  When the rear end, that is, the end of the minute droplet reaches the first branch portion 6, the gas pushing the minute droplet flows into the second flow path 5 and reaches the second branch portion 7. . As a result, the minute droplets that exist from the flow path portion 4 </ b> A beyond the second branch portion 7 are divided by the gas at the point of the second branch portion 7. Thereafter, for each of the two droplets generated by the separation, the droplets in the channel portion 4A between the first branch portion 6 and the second branch portion 7 of the first channel 4 are removed. The weighed droplets and another droplet near the discharge port will be referred to as weighed residual liquid. Since the gas pressures of the first branch part 6 and the second branch part 7 are equal, the weighed droplets in the flow path part 4A do not move. Further, by supplying the gas, the weighing residual liquid located downstream from the second branch portion 7 is discharged from the discharge port 3.

  As a result, trace droplets remain in the flow path portion 4A, and it is possible to weigh trace droplets having a volume equal to the volume of the flow path portion 4A. That is, a predetermined amount of minute droplets can be easily and reliably weighed only by introducing a gas from the introduction port 2 following the introduction of the minute droplets from the introduction port 2.

  Moreover, since the capillary phenomenon is not utilized, the volume of the flow path portion 4A can be made much larger than the volume of the liquid that can be drawn into the capillary phenomenon. Therefore, a sufficiently large volume of a trace liquid can be reliably weighed by a relatively simple operation such as introduction of a minute droplet and introduction of gas.

  It should be noted that various structures can be used when taking out the minute droplets weighed in the flow path portion 4A. For example, as schematically shown in FIG. 1, a structure in which an opening / closing valve V is provided in the second flow path 5 is an example. That is, when weighing the microdroplet, the open / close valve V is opened and the second flow path 5 is opened. After the microdroplet is weighed in the flow path portion 4A, the open / close valve V is closed and the second flow path 5 is closed. Thereafter, if further gas is supplied from the inlet 2, a minute amount of liquid droplets existing in the flow path portion 4 </ b> A can be sent to the outlet 3, and a predetermined amount of minute droplets can be taken out from the outlet 3. it can.

  However, not only the structure in which the opening / closing valve V is provided in the second flow path, but also a microdroplet weighing structure according to the second embodiment of the present invention shown in FIG. 2 may be used. In the microdroplet weighing structure 1 </ b> A of the second embodiment shown in FIG. 2, as in the microdroplet weighing structure 1 in the first embodiment, the introduction port 2, the discharge port 3, and the first flow path 4. And the 2nd flow path 5 is formed. Furthermore, in the microdroplet weighing structure 1A, one end of the third flow path 8 is connected to the flow path portion 4A. More specifically, in the present embodiment, the third branch portion 9 is provided at the central position in the flow channel length direction of the flow channel portion 4A that connects the first branch portion 6 and the second branch portion 7. One end of the third flow path 8 is connected to the third branch portion 9. The third flow path 8 constitutes a Laplace valve.

  The Laplace valve is a general term for a valve structure in which the liquid stops when the Laplace pressure caused by the surface tension at the gas-liquid interface balances with the back pressure of the fluid. The upper limit of the back pressure at which the liquid is stopped is determined by the surface tension of the gas-liquid interface and the radius of curvature of the gas-liquid interface according to Laplace's law.

When the shape of the gas-liquid interface can be considered as a spherical surface represented by one radius of curvature (R), Laplace's equation shows the following relationship between the back pressure (P _G ) and the tension (σ) in the gas-liquid interface. It states that it is in the formula, ie, P _G = 2σ / R. For a gas-liquid interface of an arbitrary shape, the shape can be displayed with two principal radii of curvature that are orthogonally separated. When the principal radii of curvature are R ₁ and R ₂ , respectively, the Laplace pressure is P _G = σ ( 1 / R ₁ + 1 / R ₂ ).

When the flow path D has a rectangular cross section, the length of one side of the rectangle is a, and the length of the other side is b. When 0.5 <a / b <2, R ₁ = a / 2, R ₂ = b / 2 can be approximated, and P _G = 4σ (1 / a + 1 / b). When a / b <0.1, it is approximated as P _G = 4σ / a, and when a / b> 10, it is approximated as P _G = 4σ / b. Here, σ is a temperature-dependent physical property value. For example, in the case of pure water, σ is about 70 to 75 mN / m in the range of 5 ° C. to 35 ° C.

Even when the cross-sectional shape of the third channel 8 is not rectangular, if the cross-sectional area is S and the peripheral length of the cross-section is L, the Laplace pressure is approximately approximated as P _G = σL / S. The In addition,
4 · S / L is called hydraulic equivalent diameter.

  More specifically, the Laplace valve can be constituted by at least one narrowly-squeezed channel having a water-repellent or hydrophilic surface, or a large number of parallelly-squeezed narrow channels or a porous body. The narrowest diameter of the narrow channel or the narrowest diameter of the hole of the porous body is desirably 40 μm or less, and more desirably 10 μm or less. The Laplace valve can also be constituted by a weir part, a slit, an emboss, a pillar, a sponge, a fine particle filling, a water repellent finish, and the like.

  The end of the third flow path 8 opposite to the third branch portion 9 is connected to the chamber 10. The chamber 10 has a volume capable of storing the liquid weighed in the flow path portion 4A. In FIG. 2, the plane area of the chamber 10 is shown to be smaller than the plane area of the flow path portion 4A, but in reality, the chamber 10 has a height dimension larger than that of the flow path portion 4A. The size is such that a small amount of liquid droplets weighed in the flow path portion A is stored.

  The fourth flow path 11 is for discharging the air in the chamber 10, and one end of the fourth flow path 11 is connected to the chamber 10 and the other end is connected to the exhaust port 12. The fourth flow path 11 is preferably configured as a Laplace valve. However, when the chamber 10 is connected to a different liquid operation element, the fourth flow path 11 may not be a Laplace valve. is there.

  In addition, the position of the 3rd branch part 9 is located in the center in the length direction of 4 A of flow-path parts between the 1st branch part 6 and the 2nd branch part 7 like this embodiment. Is desirable. Thereby, as will be described later, it is possible to quickly weigh the minute droplets weighed from the third flow path 8 to the flow path portion 4A. But the 3rd branch part 9 may be slightly biased and provided in the 1st branch part 6 side or the 2nd branch part 7 side.

  Moreover, the opening diameter of the connection part of the 3rd flow path 8 and the 1st flow path may be changed.

  Next, a microdroplet weighing method using the microdroplet weighing structure 1A according to the second embodiment will be described with reference to FIGS.

  FIG. 3A is a diagram showing an initial state of the microdroplet weighing structure 1A. In the initial state, the minute droplets and gas are not introduced into the first flow path 4.

  Next, the microdroplet 13 is introduced from the inlet 2 into the first channel 4. The introduction of the minute droplet 13 is performed by connecting a flow path for pushing the droplet with a gas pressure using a pump (not shown) to the introduction port 2 or connecting an injection means such as a syringe to the introduction port 2. Can be performed. The minute droplet 13 moves in the first flow path 4 from the inlet 2 toward the outlet 3. As the microdroplet 13 to be introduced, a microdroplet having a volume larger than the volume of the flow path portion 4A is used.

  As shown in FIGS. 3B to 3E, the microdroplet 13 introduced into the first channel 4 moves in the first channel 4 from the inlet 2 toward the outlet 3 side. To do. In this case, it does not move into the second flow path 5 as shown in FIG. Then, as shown in FIG. 3 (e), when the end 11 a of the minute droplet 13 exceeds the first branch portion 6, the gas pushing the minute droplet 13 flows into the second flow path 5. It will be. Therefore, as shown in FIG. 3 (f), the microdroplet 13 is divided by the gas that flows out from the second flow path 5 at the position of the second branch portion 7.

  As shown in FIG. 3 (f), since the gas pressures of the first branch portion 6 and the second branch portion 7 are equal, the minute droplet 13A located in the flow path portion 4A does not move and is divided. Further, the minute droplet portion 13B on the downstream side moves toward the discharge port 3 by the gas pressure. Therefore, as shown in FIG. 3G, when the minute droplet portion 13B is discharged from the discharge port 3, the minute droplet equal to the volume of the channel portion 4A is added to the channel portion 4A of the first channel 4. 13A will be weighed.

Thereafter, the discharge port 3 is closed. When supplying again the gas from the inlet 2, when the gas pressure P _G is to satisfy the relation of P _G> 2 [sigma] / R, the third channel 8, it is possible to trace droplet 13A is supplied, the chamber The microdroplet 13 </ b> A moves to 10. Therefore, as shown in FIG. 3I, the weighed microdroplet 13A is finally transferred to the chamber 10 and weighed.

In the above formula, σ represents the surface tension (unit: mN / m) of the inner surface of the third flow path 8, and R represents the radius of curvature (unit: m). When the cross-sectional size is a × b and the contact angle is θ, R is approximated as 1 / R = 2 (1 / a + 1 / b), and P _G = 4σ (1 / a + 1 / b). Here, P _G gas pressure measured by the gauge (in Pa) is.

  That is, in the present embodiment, the third flow path 8 is configured to satisfy the above formula, in other words, a Laplace valve. Accordingly, the minute droplet 13A weighed in the flow path portion 4A is reliably stored in the chamber 10, and the gas supplied thereafter is discharged from the exhaust port 12 through the fourth flow path 11.

  The chamber 10 is an example of a transfer destination of the weighed microdroplet 13A. Instead of the chamber 10, other flow paths or other fluid elements may be used. Further, as described in the embodiment of FIG. 1 described above, the third flow path 8 and the chamber 10 may be reduced when it is not necessary to transfer the chamber 10 or the like outside.

  4A to 4F are schematic plan views for explaining a microdroplet weighing structure according to a third embodiment of the present invention. As shown in FIG. 4A, in the third embodiment, two microdroplet weighing structures 1 of the first embodiment are connected in series.

  The first microdroplet weighing structure 1 is connected to the introduction port 2, and corresponds to the downstream end of the first flow path 4 of the first microdroplet weighing structure 1, that is, the discharge port 3. The part is connected to the inlet of the subsequent microdroplet weighing structure 1B. That is, two microdroplet weighing structures 1 and 1B are connected in series. The microdroplet weighing structure 1B is configured in the same manner as the microdroplet weighing structure 1.

  Thus, in the present invention, a plurality of microdroplet weighing structures may be connected in series. Thereby, as described below, it is possible to weigh a plurality of minute droplets having a predetermined volume.

  FIG. 4A shows an initial state. As shown in FIG. 4B, the microdroplet 13 is introduced into the first channel 4 from the inlet 2. The microdroplet 13 has a volume of trace liquid larger than the sum of the microdroplet amount weighed by the microdroplet weighing structure 1 and the microdroplet amount weighed by the microdroplet weighing structure 1B. Drops are introduced. The introduction may be performed in the same manner as in the case of the microdroplet weighing method shown in FIG.

  As shown in FIGS. 4B and 4C, the microdroplet 13 is formed in the first flow path 4 of the upstream microdroplet weighing structure 1 and the downstream of the microdroplet weighing structure 1B on the downstream side. 1 channel 4 is filled. Thereafter, when the gas is continuously supplied from the introduction port 2, as shown in FIG. 4 (d), the gas flows through the third flow path 5 in the microscopic droplet weighing structure 1 on the upstream side, In the branch part 7, the minute droplet 13 is divided. In this state, the first branch portion 6 and the second branch portion 7 are in the same pressure state.

  Thereafter, by further supplying gas, the microdroplet 13 moves through the first flow path 4 of the microdroplet weighing structure 1B on the downstream side. Further, as shown in FIG. A gas flows from the first branch portion 6 of the droplet weighing structure 1B to the second flow path 5. As a result, also in the microdroplet weighing structure 1B, the pressures of the first branch portion 6 and the second branch portion 7 become equal, and the microdroplet 13 is divided. Accordingly, the downstream minute droplet 13C shown in FIG. 4 (e) is discharged from the discharge port 3, and as shown in FIG. 4 (f), the minute droplet weighing structure 1B also has a minute amount in the flow path portion 4A. The droplet 13A is weighed. As a result, in the microdroplet weighing structures 1 and 1B, the microdroplets 13A and 13A having a volume equal to the volume of the flow path portion 4A can be respectively weighed.

  In the present embodiment, the microdroplet weighing structures 1 and 1B are configured similarly, but may be configured differently. That is, the volume of the flow path portion 4 of the microdroplet weighing structure 1B may be different from the flow path portion 4 of the microdroplet weighing structure 1. Thereby, microdroplets of different volumes can be weighed in the microdroplet weighing structures 1 and 1B, respectively.

  In the present embodiment, the two microdroplet weighing structures 1 and 1B are connected in series, but three or more microdroplet weighing structures may be connected in series.

  In the embodiment described above, the cross section of the flow path portion 4A is shown to be constant along the length direction of the flow path. However, as shown in FIG. The area of the surface may be changed along the length direction of the flow path. As described above, when a portion where the cross-sectional area of the flow path gradually increases is provided in the flow path portion 4A, it is possible to weigh a small volume of a small volume droplet. Further, it is possible to more quickly weigh trace droplets into the flow path portion 4A. In addition, it is preferable that the area of a cross section changes 20% or more along a flow path length direction. As a result, more weighing can be performed with a shorter flow path length, and the disadvantage of the pressure loss that occurs when the droplets flow in the first flow path 4 can be avoided, and a reliable weighing operation can be performed. It can be carried out.

  As shown in FIG. 5B, the channel portion 4B reaching the channel portion 4A and the downstream channel portion 4C may be arranged in parallel to each other. Moreover, as shown in FIG.5 (c), it is good also considering the planar shape of the flow-path part 4A as V shape. Furthermore, as shown in FIG. 5 (d), the first flow paths 4 may be brought close to each other in the portions where the first and second branch portions 6 and 7 are provided. In this way, it is possible to increase both the volume of the flow path portion 4A and to shorten the length of the second flow path 5.

  As shown in FIGS. 5A to 5D, the planar shape of the first channel 4 and the planar shape of the first channel portion 4A in the present invention can be appropriately modified.

  FIG. 6 is a schematic plan view showing a microdroplet weighing structure according to a fourth embodiment of the present invention. In the microdroplet weighing structure of the fourth embodiment, one end of the fourth channel 21 is connected to the inlet 2 of the microdroplet weighing structure 1A of the second embodiment, and the fourth flow A reagent storage unit 22 is connected to the upstream end of the passage 21. The reagent storage unit 22 is connected to the reagent introduction port 23 via the fifth flow path 24. The fifth flow path 24 is configured to supply a liquid reagent to the reagent storage unit 22. The reagent inlet 23 is connected to another flow path or a syringe. A liquid reagent is supplied from the reagent introduction port 23 to the reagent storage unit 22 via the fifth flow path 24.

  The reagent storage unit 22 is connected to an exhaust port 26 via a flow path 25 that is a gas selective flow path. The reagent storage unit 22 is connected to the stimulus-responsive gas generating member 29 via the gas flow path 28. The gas generated by the stimulus-responsive gas generating member 29 is supplied to the reagent storage unit 22 through the gas flow path 28, and the introduced liquid reagent is supplied from the introduction port 2 through the fourth flow path 21. 1 to the channel 4.

  The discharge port 3 at the downstream end of the first flow path 4 is connected to the sixth flow path 30 having selective gas permeability and the downstream end of the sixth flow path 30 instead of the structure for discharging the liquid. The opening 31 is formed. The sixth flow path 30 is a flow path that allows only a gas to pass without passing a minute amount of liquid droplets, and functions as a stop valve that passively stops liquid feeding without an external operation. Such a stop valve is configured by forming the sixth flow path 30 so as to have a Laplace pressure higher than the Laplace pressure of the third flow path 9. That is, the above-described stop valve can be configured by configuring a relatively narrow channel so as to have a higher Laplace pressure than the third channel 9 and opening the end to the atmosphere. Since the stop valve is provided, the portion corresponding to the discharge port of the microdroplet weighing structure 1 is automatically closed so as not to discharge the microdroplet.

  Therefore, according to the present embodiment, after the microdroplet is weighed in the flow path portion 4A, the gas divides the microdroplet at the second branch portion via the second flow path 5, and the microdroplet The balance remaining liquid generated as a result of the division is pushed out into the gas and reaches the downstream side of the first flow path 4, and the air in the flow path from which the balance residual liquid is pushed out is released from the stop valve. The remaining liquid is stopped by the stop valve and does not reach the opening 31. Therefore, the operation of closing the discharge port in the embodiment described with reference to FIG. 3 is performed spontaneously without any external operation, and then the gas pressure in the first flow path 4 increases, and the flow path portion 4A. A predetermined amount of the minute droplets weighed in the step is transferred to the chamber 10 via the Laplace valve of the third flow path 9. That is, it is possible to automatically perform weighing of a predetermined amount of minute droplets and transfer of the weighed minute droplets to the chamber 10 simply by introducing the droplets from the introduction port by gas pressure.

  FIG. 7 is a schematic plan view showing a microdroplet weighing structure according to a fifth embodiment of the present invention. In the present embodiment, the microdroplet weighing structure 1 </ b> D is connected to the mixing chamber 41. The microdroplet weighing structure 1D is configured similarly to the microdroplet weighing structure shown in FIG. The difference is that the other end of the third flow path 8 is replaced by the mixing chamber 41 instead of the chamber 10. The mixing chamber 41 is supplied with a microdroplet equal to the volume of the channel portion 4A from the microdroplet weighing structure 1D as in the first embodiment described above.

  On the other hand, in the mixing chamber 41, a second microdroplet weighing structure 42 is connected. The microdroplet weighing structure 42 has a channel 45 that connects the inlet 43 and the outlet 44. A weighing unit 46 is connected in the middle of the flow path 45. The volume of the weighing unit 46 is substantially equal to the volume of the minute droplets supplied to the mixing chamber 41. The end of the weighing unit 46 opposite to the side connected to the flow channel 45 is connected to the mixing chamber 41 by a flow channel 47. The channel 47 is configured in the same manner as the third channel 8 described above.

  Such a microdroplet weighing structure 42 is configured in the same manner as a conventional microdroplet weighing structure as described in Patent Document 2. Therefore, the minute droplets weighed by the weighing unit 46 are guided to the mixing chamber 41 via the flow path 47.

  In the present embodiment, the minute droplets weighed by the weighing unit 46 and the minute droplets weighed by the flow path portion 4 </ b> A are mixed in the mixing chamber 41. Therefore, two kinds of minute droplets can be mixed in the mixing chamber 41 at a ratio of the volume of the flow path portion 4 </ b> A and the volume of the weighing unit 46. In the microdroplet weighing structure 1D, as described above, a microdroplet having a volume larger than that of a microdroplet that can be derived by capillary action can be weighed. Therefore, according to the present embodiment, the mixing ratio of the minute droplets supplied from the weighing unit 46 and the flow path portion 4A can be set to 1 to 10 or more in volume ratio.

  As apparent from the embodiment shown in FIG. 7, in the present invention, at least two microdroplet weighing structures are connected to the mixing chamber 41 which is a microdroplet mixing unit, and at least one microdroplet among them is connected. The weighing structure can be a microdroplet weighing structure constructed according to the present invention. Thereby, a plurality of components can be mixed so that the volume ratio of the largest component to the smallest component is 10 times or more.

  FIG. 8 is a schematic plan view showing the channel structure of the microfluidic device according to the sixth embodiment of the present invention.

  In the microfluidic device of this embodiment, the portion indicated by the alternate long and short dash line A is configured in substantially the same manner as the microdroplet weighing structure shown in FIG. Accordingly, the same parts are denoted by the same reference numerals, and the description thereof is omitted. In the present embodiment, a waste liquid storage unit 51 is provided instead of the discharge port of the microdroplet weighing structure 1D. The waste liquid storage unit 51 is connected to the exhaust port 52 via the exhaust passage 53.

  Similarly, in the microdroplet weighing structure 40, a liquid reservoir 54 is provided instead of the discharge port 44, and the liquid reservoir 54 is connected to the exhaust port 55 via the exhaust channel 53. ing. Further, a gas generator 56 is connected via a gas supply channel 57 between the introduction port 2 of the microdroplet weighing structure 1D and the channel portion 4A. Similarly, a gas generator 58 is connected to the upstream side of the mixing chamber 41 via a gas flow path 59.

  The downstream end of the mixing chamber 41 is connected to the mixing unit 60. The mixing unit 60 is formed by a flow path having a meandering planar shape. By such a meander-shaped channel, the mixing of the minute droplets is ensured by the effect of increasing the staying time of the mixed minute droplets and the shear flow for each bent portion. The downstream end of the mixing unit 60 is connected to the discharge port 61.

  In the flow path structure of the microfluidic device of the present embodiment, the first minute droplets are supplied from the introduction port 2 and the gas is supplied from the gas generation unit 56. Thereby, a predetermined amount of minute droplets are weighed in the flow path portion 4A.

  Similarly, in the microdroplet weighing structure 40, a predetermined amount of microdroplets are weighed by the weighing unit 46. These two kinds of minute droplets are supplied to the mixing chamber 41 and are sent to the mixing unit 60 and mixed by the gas generated by the gas generating unit 58. Therefore, a micro droplet in which two types of micro droplets are mixed can be taken out from the discharge port 61. In that case, the supply of the minute droplets 13, the mixing of the minute droplets, and the extraction of the mixed minute droplets can be automatically performed only by supplying the gas from the gas generating units 56 and 58.

  Although FIG. 8 shows the flow path structure of the minute droplets of the microfluidic device according to the embodiment of the present invention, a plurality of such flow path structures may be integrated.

  FIG. 9 is a schematic plan view of a microfluidic device including a large number of microdroplet channel structures shown in FIG. The microfluidic device 71 has a substrate 72. The base material 72 can be obtained by, for example, a synthetic resin laminated plate or a structure in which a glass plate or the like is laminated on a synthetic resin plate. The illustrated flow path structure is formed in the base material 72. FIG. 9 is a plan view schematically showing the internal flow path structure through the base material from the upper surface side of the base material 72.

  In the microfluidic device 71, eight microdroplet weighing structures 73A to 73H are formed. Among these, the microdroplet weighing structure 73A, 73B, 73C, 73F, 73G, 73H is the microdroplet weighing structure according to the embodiment of the present invention. The microdroplet weighing structures 73A, 73B, and 73C are connected in series. Further, the microdroplet weighing structures 73D, 73E, and 73F are connected in series to the microdroplet weighing structure 73C. The microdroplets sequentially mixed by these microdroplet weighing structures 73A to 73C and the microdroplets mixed by the microdroplet weighing structures 73D to 73F are mixed in the mixing chamber 74, and the mixing unit 75 is mixed. Is supplied to the reaction chamber 76. On the other hand, the microdroplets weighed by the microdroplet weighing structure 73G are also supplied to the reaction chamber 76. The microdroplet after the reaction is fed to the mixing chamber 78 via the mixing unit 77. In the mixing chamber 78, the microdroplets weighed by the microdroplet weighing structure 73H are also supplied and mixed. In this manner, the finally mixed microdroplets containing the liquid analyte reaction product are supplied to the PCR unit 80 via the mixing unit 79. The PCR unit 80 includes a zone 80A having a temperature of 60 ° C., a zone 80B having a temperature of 72 ° C., and a zone 80C having a temperature of 98 ° C. Therefore, it is possible to amplify the specimen by heating a minute droplet formed by mixing a plurality of kinds of specimens and reagents in the PCR unit 80.

  It should be noted that the microfluidic device 71 shown in FIG. 9 is merely an example of a microfluidic device to which the microdroplet weighing structure of the present invention is applied. Thus, by accumulating a plurality of microdroplet weighing structures of the present invention, it can be suitably used for a microfluidic analyzer that handles many reagents and specimens.

DESCRIPTION OF SYMBOLS 1,1A, 1B, 1D ... Trace drop weighing structure 2 ... Inlet 3 ... Discharge 4 ... 1st flow path 4A, 4B, 4C ... Flow path part 5 ... 2nd flow path 6 ... 1st Branch part 7 ... Second branch part 8 ... Third flow path 9 ... Third branch part 10 ... Chamber 11 ... Fourth flow path 11a ... Terminal 12 ... Exhaust port 13 ... Small droplets 13A, 13C ... Small amount Droplet 13B: Trace droplet portion 21 ... Fourth channel 22 ... Reagent storage unit 23 ... Reagent inlet 24 ... Fifth channel 25 ... Channel 26 ... Exhaust port 28 ... Gas channel 29 ... Stimulus responsiveness Gas generating member 30 ... sixth flow path 31 ... opening 40 ... trace droplet weighing structure 41 ... mixing chamber 42 ... trace droplet weighing structure 43 ... introduction port 44 ... discharge port 45 ... flow channel 46 ... weighing unit 47 ... Flow path 51 ... Waste liquid storage part 52 ... Exhaust port 53 ... Exhaust flow path 54 ... Liquid storage part 55 ... Exhaust port 56 ... Gas Generating part 57 ... Gas supply flow path 58 ... Gas generating part 59 ... Gas flow path 60 ... Mixing part 61 ... Discharge port 71 ... Microfluidic device 72 ... Substrate 73A to 73H ... Trace droplet weighing structure 74 ... Mixing chamber 75 ... Mixing unit 76 ... Reaction chamber 77 ... Mixing unit 78 ... Mixing chamber 79 ... Mixing unit 80 ... PCR unit 80A, 80B, 80C ... Zone

Claims (11)

A structure for weighing a small amount of droplets,
A substrate and a flow path provided in the substrate;
The flow path has a first flow path having one end connected to an inlet to which droplets and gas are supplied and the other end connected to a discharge port;
A gas selective flow is formed by connecting a first branch part in the middle of the first flow path and a second branch part located on the downstream side of the first flow path with respect to the first branch part. A second flow path comprising a path,
A microdroplet weighing structure in which the volume of the first flow path portion connecting the first branching portion and the second branching portion is equal to the volume of the microdroplet to be weighed.   The flow path length of the first flow path portion from the first branch section to the second branch section is longer than twice the flow path length of the second flow path and shorter than 1000 times. Item 2. The microdroplet weighing structure according to Item 1.   A third branch part is provided in the middle of the first flow path part between the first branch part and the second branch part, and one end of the third flow path is provided at the third branch part. The microdroplet weighing structure according to claim 1, wherein the third channel has a Laplace valve.   4. The microdroplet weighing structure according to claim 3, wherein the Laplace valve is composed of a narrowed flow path having a hydraulic equivalent diameter of the flow path of 40 μm or less.   The microdroplet weighing structure according to claim 1, further comprising a valve that is provided in the middle of the second flow path and opens and closes the second flow path.   2. The first flow path and / or the second flow path includes a portion in which an area of a cross section has an absolute value of a change rate along a length direction of the flow path of 20% or more. The microdroplet weighing structure according to any one of -5.   The other microdroplet weighing structure according to any one of claims 1 to 6, on the downstream side of the discharge port of the microdroplet weighing structure according to any one of claims 1 to 6. A microdroplet weighing structure that is connected to the inlet.   The microdroplet weighing structure according to any one of claims 1 to 7, further comprising an exhaust flow path connected to the discharge port.   A microdroplet mixing unit is further provided, and at least two microdroplet weighing structures are connected to the microdroplet mixing unit, and at least one microdroplet weighing unit of the at least two microdroplet weighing structures is connected. The microdroplet weighing structure according to any one of claims 1 to 8, wherein a plurality of components supplied from at least two microdroplet weighing structures in the microdroplet mixing unit are provided. 9. The microdroplet weighing structure according to claim 1, wherein the volume ratio of the smallest component to the largest component is 1 to 10 or more.   A microfluidic device provided with the microdroplet weighing structure according to claim 1. A microdroplet weighing method using the microdroplet weighing structure according to any one of claims 1 to 9,
Introducing, by gas pressure, a microdroplet having a volume larger than the volume of the first channel portion from the first branch portion to the second branch portion from the inlet to the first channel; ,
Clogging the outlet after the trailing edge of the introduced microdroplet reaches the first branch,
Discharging the trace droplets stored in the first flow path portion between the first branch section and the second branch section from the third flow path. Method.

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