JP4775039B2 - Microfluidic chip - Google Patents

Description

  The present invention relates to a microfluidic chip, and as a detailed example, in a liquid feeding device used for analyzing a biological fluid such as blood, a biological fluid or a fluid such as a diluent or a reaction product solution is used. The present invention relates to a configuration of a micro flow channel for transferring to the site.

  As a device for analyzing biological fluids such as blood, devices have been developed to measure and evaluate accurately and simply with a small amount of sample. In such a device, a sample or diluent, a reaction called a microfluidic chip is developed. A flow path for transferring a fluid such as a product solution to a target site is formed, and the flow is generated by gravity acting on the flow path, capillary force or centrifugal force by rotation, pressurization by a pump, and aerodynamic force of suction. An inspection chip is used in which a fluid flows in the passage.

  As one of the methods for controlling the flow of fluid in the microfluidic chip, a means including a siphon and transferring liquid by the rotational motion of the rotating device by the siphon is disclosed. (For example, refer to Patent Document 1.) In this method, the liquid is transferred by capillary force and centrifugal force. In this case, by using capillary force such as giving exhalation water to the siphon, While the liquid can be transported in the opposite direction, the inner wall of the flow path needs to be hydrophilic, so that hydrophilic treatment is generally performed.

On the other hand, a method of hydrophilizing the inner wall of the flow path of a plastic substrate capable of injection molding with good productivity is also disclosed. (For example, see Patent Document 2.)
In this way, by utilizing the capillary force of the channel subjected to the hydrophilic treatment, not only the unidirectional flow control from the rotation inner periphery side to the rotation outer periphery side by centrifugal force but also the rotation inner side from the rotation outer periphery side. The flow to the circumferential side can be controlled.

  Further, Patent Document 2 discloses that a plurality of cuvettes are arranged radially outward with respect to the collection chamber. In this way, when one flow path is branched and fluid is divided into a plurality of cuvettes (chambers), it is sometimes required to accurately divide and distribute the fluid. The quantification at this time is configured so that a desired volume of fluid is sent to each chamber using a centrifugal force after quantification based on the volume of a flow path formed by a capillary tube upstream of each chamber.

  FIG. 7 shows a microfluidic chip 101 used in a conventional blood test apparatus. The microfluidic chip 101 has a disk shape with a diameter of 100 mm. A cross section AA of the microfluidic chip 101 is shown in FIG. The microfluidic chip 101 is formed, for example, to form a lower panel 2 made of a resin-made flat surface made of polycarbonate, an upper panel 3 in which only a chamber shape is formed on the flat surface by cutting or the like, and a capillary and a chamber. The spacer 4 of a hot melt sheet having a thickness of 0.1 mm is formed by heat bonding, and can be rotated around the rotation center 100 by, for example, a stepping motor or the like (not shown).

  In FIG. 7, the depths of the first to eighth chambers 11, 12, 103, 104, 105, 16, 17, 18 are the cutting depth of the upper panel 3 of 0.5 mm and the thickness of the spacer 4. The depth of each channel from the first channel 21 to the fifth channel 25 is 0.1 mm of the thickness of the spacer 4. Further, the surfaces of the lower panel 2 and the upper panel 3 are subjected to a hydrophilic treatment so that the contact angle with plasma is about 10 degrees. On the other hand, the cut surface of the upper panel 3 is not subjected to a hydrophilic treatment, and thus the contact angle is about 60 degrees. That is, the contact angle of the capillary inner wall is 10 degrees, and the contact angle of the chamber inner wall is 10 degrees on one side of the lower panel 2 but 60 degrees on the other side.

When the cross section of the capillary is defined as shown in FIG. 9, the capillary force is generated according to Equation 1, so, for example, in the narrowest part of the second to fifth channels, the width is 1 mm, the height is 0.1 mm, and the plasma Since the surface tension is about 0.04 N / m, a capillary force of about 850 N / m ² is generated at a cross-sectional pressure of about 85 μN.

@ 0001
The specimen, which is a liquid, is caused to flow by the capillary force and the centrifugal force generated by rotating around the rotation center 100.

  Hereinafter, the operation of the microfluidic chip 101 will be described with reference to FIGS. 10 to 14 showing the state of the liquid specimen (blood, plasma).

  First, when, for example, blood, which is a sample, is injected into the first chamber 11 from the sample injection port 31 with a dropper or the like, the sample is introduced into the first flow path 21 formed of a capillary connected to the first chamber 11 by capillary action as shown in FIG. The blood flows in and blood (hatched portion in FIG. 10) stops at the connection place between the first flow path 21 and the second chamber 12.

  In this state, when the microfluidic chip 101 is rotated with the rotation center 100 as an axis at a rotation speed of, for example, 4000 rpm, the specimen in the first chamber 11 moves to the second chamber 12 through the first flow path 21. Thereafter, by holding the microfluidic chip 101 at 4000 rpm, for example, for 5 minutes, as shown in FIG. 11, the blood sample has a relatively high specific gravity of red blood cells or white blood cells (in FIG. 11, the fine hatched portion) is centrifuged. On the other hand, plasma having a relatively small specific gravity (rough hatched portion in FIG. 11) is separated to the rotation center 100 side, so-called centrifugal separation occurs.

  By stopping the rotation of the microfluidic chip 101 in this state, only the plasma separated to the rotation center 100 side is caused to flow into the second flow path 22 formed in a siphon shape by capillary force as shown in FIG. When the microfluidic chip 101 is rotated again after the second flow path 22 is filled with plasma, the plasma is divided by the air flowing in from the air holes 32, and as shown in FIG. It flows into the 4th chamber 104 and the 5th chamber 105, respectively. Thus, a desired amount of plasma is diverted to the third chamber 103, the fourth chamber 104, and the fifth chamber 105 depending on the flow path shape of the second flow path 22. The plasma flowing into the third chamber 103, the fourth chamber 104, and the fifth chamber 105 is mixed with the reagent 41, the reagent 42, and the reagent 43 that are sealed in advance in the microfluidic chip 101, respectively. Here, the rotation speed of the microfluidic chip 101 is repeatedly accelerated and decelerated between 4000 rpm and 1500 rpm, and in each of the third chamber 103, the fourth chamber 104, and the fifth chamber 105, the sample plasma and each reagent 41, Promotes mixing with 42 and 43.

  Thereafter, the rotation of the microfluidic chip 101 is stopped again, so that plasma flows into the third flow path 23, the fourth flow path 24, and the fifth flow path 25 made of capillary tubes, and the third flow path 23 and the fourth flow path 25 24. After the fifth flow path 25 is filled with plasma, the microfluidic chip 101 is rotated again to finally analyze the sample optically or electrically, the sixth chamber 16 and the seventh chamber 17. The plasma mixed with the reagents 41, 42, and 43 can be transported to the eighth chamber 18, respectively (FIG. 14).

As described above, the microfluidic chip 101 is configured to transfer the specimen to the analysis chamber through blood injection, centrifugation, plasma quantification, and mixing with a reagent by using capillary force and centrifugal force. ing.
Japanese National Patent Publication No. 5-508709 JP 2000-46797 A

  However, when the liquid sent into the chamber having a hydrophilic surface is stopped, it is controlled by the capillary force and gravity generated by the contact angle with each wall surface constituting the chamber and its own surface tension. Move. In other words, there is no longer a conceptual upstream / downstream relationship from the rotating shaft side to the outer peripheral side, and the liquid accumulated in the chamber flows into the downstream capillary tube and similarly upstream to the chamber wall surface. It will also flow toward the side. In addition, the wall surface constituting the chamber has a microscopic contact angle and surface roughness variation, which causes a force imbalance and may flow largely upstream. In this case, a so-called back flow occurs in which the liquid flows into the upstream capillary tube.

  The present invention solves the above-mentioned conventional problems, and provides a mechanism for preventing the liquid accumulated in the chamber from flowing into the upstream capillary tube when the rotation is stopped. It is an object to provide a liquid transport device that can be reliably transferred.

In order to solve the above-described conventional problems, the microfluidic chip of the present invention is filled with a tunnel-shaped first flow path through which a liquid to be inspected flows and the liquid in which the first flow path is connected at the bottom surface. A hollow chamber for performing the operation, a tunnel-like second flow channel connected to the bottom surface of the chamber for discharging the liquid stored in the chamber, and an inner wall thickness of the chamber within the chamber. Protruding portions that are continuous in the width direction of the chamber having a small height are provided , and the cross-sectional area of the gap formed by the protruding portions is larger than the cross-sectional area of the first flow path. It is a thing.

  Further, the present invention is characterized in that the connection portion of the first flow path in the chamber is at a position opposite to the connection portion of the second flow path.

  In addition, the present invention is characterized in that the protrusion is provided at a position where the liquid does not exist when the chamber is filled with the liquid.

  Furthermore, the present invention is characterized in that the surfaces of the first and second flow paths and the inner wall of the chamber are processed so as to have hydrophilicity.

  According to the microfluidic chip of the present invention, the liquid can be reliably fed without deteriorating the productivity of the microfluidic chip.

Hereinafter, embodiments of the microfluidic chip of the present invention will be described in detail with reference to the drawings.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a microfluidic chip 1 used in the blood test apparatus according to this embodiment. In the microfluidic chip 1 in the present embodiment, projections 53, 54, and 55 according to the present invention are formed in the third chamber 13, the fourth chamber 14, and the fifth chamber 15, respectively. Since the other structure is the same as that of the conventional microfluidic chip 101 shown in FIG. 7, detailed description thereof is omitted.

  FIG. 2 is an enlarged view of the third chamber 13 and a sectional view thereof. The second flow path 22 formed on the upstream side of the third chamber 13 has a width of 1 mm and a height of 0.1 mm, and the height is reduced to 0.1 mm so that the capillary force acts. ing. The third chamber 13 is formed with a width of 3 mm, a length of 11 mm, and a height D of 0.6 mm. The third flow path 23 formed on the downstream side of the third chamber 13 has a width of 1 mm and a height of 0.1 mm, and a capillary force acts similarly to the second flow path 22.

  Here, the protrusion 53 according to the present invention of the third chamber 13 has a width of 3 mm and a height d of 0.5 mm, and this protrusion causes the gap to be the same as that of the second flow path 22 and the third flow path 23. It is 1 mm. Protruding 53 to protrude from a part of the third chamber 13 in this manner is to cut the shape of the third chamber 13 to the upper panel 3 by cutting, like other capillary channels such as the second channel 22. It can be formed by not performing cutting when processing. Further, since the gap of the third chamber 13 is narrowed by the protrusion 53, a capillary force is generated as in the second flow path 22 and the third flow path 23. Here, for convenience, the space of the third chamber 13 above the protrusion 53 is referred to as a chamber upper portion 61, and the space of the third chamber 13 below the protrusion 53 is referred to as a chamber lower portion 62. The volume of the chamber lower part 62 is formed larger than the volume of the liquid flowing into the third chamber 13 from the second flow path 22. In the present embodiment, the volume of the chamber lower portion 62 is about 9 ul, which is 5 mm long × 3 mm wide × 0.6 mm high. On the other hand, the volume of the liquid flowing into the third chamber 13 is about 6 μl.

  Thus, by making the volume of the chamber lower part 62 larger than the volume of the liquid, when the microfluidic chip 1 is rotated and the liquid is transferred from the second flow path 22 to the third chamber 13, the third chamber 13 All the liquid flowing into the chamber can be stored in the chamber lower part 62. Further, the gap cross-sectional area of the third chamber 13 narrowed by the protrusion 53 is 3 mm × 0.1 mm = 0.3 mm 2, while the cross-sectional area of the second flow path 22 is 1 mm × 0.1 mm = 0.1 mm 2, Since it is formed larger than the cross-sectional area, the protrusion 53 does not prevent the liquid from flowing into the chamber lower part 62 in the process of transferring the liquid from the second flow path 22 to the third chamber 13.

  Hereinafter, in order to clarify the superiority of the effect of the protrusions of the present invention, the third chamber 13 according to the present invention in which the protrusions 53 are formed and the third chamber 103 in the conventional example without the protrusions are compared. The effect of the protrusion will be described.

  FIGS. 3A and 3B show the state of plasma in the third chamber 13 and the third chamber 103 when rotation is stopped in order to cause plasma to flow into the third flow path 23. Since there is no centrifugal force when the rotation is stopped, the plasma flows into the third flow path 23, and at the same time, the wall of the third chamber 13 and the third chamber 103 formed by the hydrophilic surface of the lower panel 2 is connected. To flow. In the third chamber 13 in which the protrusion 53 is formed, the capillary force is generated by forming the protrusion 53, so that the flow of plasma upstream from the protrusion 53 is prevented, and so-called reverse flow in the direction of the second flow path 22. Is reliably prevented. On the other hand, in the conventional third chamber 103, since the protrusion 53 is not formed, the plasma continues to flow in the upstream direction. As shown in FIG. 3B, ideally, the upstream flow occurs in a state close to left-right symmetry, so that the reverse flow of inflow into the second flow path 22 does not occur. However, in actuality, there are many cases where the fluid flows as shown in FIG. 4A or FIG. 4B due to variations in the microscopic state of the wall surface. In particular, when it becomes like FIG. 4 (B), the backflow of the plasma to the 2nd flow path 22 will arise.

  In particular, when the upstream-side second flow path 22 includes a branch as in the present embodiment, a mixed solution of plasma and reagent that has flowed back from the third chamber 103, for example, by the next rotation operation is the fourth chamber 14. In addition to not being able to quantify plasma and reagents and making testing impossible, analysis is performed with incomplete quantification, and medical diagnosis is made based on incorrect analysis results. In the worst case, you can make life-threatening mistakes.

  However, in the third chamber 13 having the protrusions 53 according to the present invention, the plasma that has flowed in by centrifugal force flows into the chamber lower part 62 formed on the downstream side of the protrusions 53. The plasma surely flows into the third flow path 23, and the backflow can be prevented by preventing the plasma flow to the upstream side by the protrusion 53.

  When rotating again in this state, the mixed solution of plasma and reagent 41 flowing into the third chamber 13 flows through the third flow path 23 and further flows into the sixth chamber 16 on the downstream side.

  As described above, in the third chamber 13 in which the projection 53 according to the present invention is formed, the plasma can be quantitatively flowed into the sixth chamber 16 by reliably preventing the backflow of the inflowed plasma.

  In addition, since the air hole 32 is provided in the chamber upper portion 61, the internal pressure of the chamber upper portion 61 is surely equal to the external pressure where the microfluidic chip 1 is placed, and even if the plasma flows, the plasma flows out. The pressure does not become lower than that of the lower chamber 62, and backflow due to a pressure difference can be reliably prevented. Further, as shown in FIG. 5, an air hole 32 may be provided in the chamber lower part 62. In this case, when the backflow prevention mechanism 53 is filled with the liquid, the pressure of both the chamber upper portion 61 and the chamber lower portion 62 can be made equal to the external pressure, and the liquid flow due to the air pressure difference can be prevented. it can.

  In addition, the height d of the protrusion 53 formed at 0.5 mm in the present embodiment is d> 0.8 D or more so that the backflow of the solution can be prevented by the capillary force due to the protrusion. desirable. By setting the height d in this way, a capillary force of 5 times or more can be generated by the protrusion 53. At that time, when the liquid is blood, it is desirable to secure 0.01 mm or more so that red blood cells, white blood cells, etc. having a diameter of about 0.008 mm constituting about half of the blood can flow reliably. When d is 0.8 D or less, a sufficient capillary force cannot be generated, and thus the effect as in the present embodiment does not occur.

  Further, although the contact angle of the wall surface constituting the capillary tube in this embodiment is 10 degrees, FIG. 6 shows the relationship between the contact angle and the capillary force when the channel width is 1 mm and the channel thickness is 0.1 mm. As described above, when the contact angle is 45 degrees or more, the capillary force is remarkably reduced. Therefore, the contact angle of the hydrophilic surface is desirably 45 degrees or less as in this embodiment.

  The fourth chamber 14 and the fifth chamber 15 in which the protrusions 54 and 55 are respectively formed have the same configuration as that of the third chamber 13 in which the protrusions 53 are formed. In the microfluidic chip 1 in the present embodiment, the liquid does not flow into the second flow path 22 due to the back flow.

  As described above, when the protrusion according to the present invention is formed, it is possible to provide a microfluidic chip that reliably prevents backflow and can be quantified.

  In this embodiment, the contact angle of the capillary inner wall is 10 degrees, the contact angle of the chamber inner wall is 10 degrees on one side, and the other surface is 60 degrees. For example, the contact angles of all the wall surfaces are hydrophilic surfaces. Even if the contact angles of all the inner walls of the chamber are set to 10 degrees, it is possible to prevent the backflow by the difference in capillary force between the protrusion 53 and the chamber upper part 61 and the chamber lower part 62.

  In addition, in the present embodiment, the effect of the present invention has been described using the microfluidic chip 1 used for blood tests. However, the effect of the present invention is generally effective for a microfluidic chip having a hydrophilic surface. Needless to say, it is not limited to a microfluidic chip for blood tests.

  The microfluidic chip according to the present invention has a configuration that enables high-precision flow rate control in a microchannel, and is useful as a technique that enables high-precision flow rate control in biological fluid analysis.

  The microfluidic chip according to the present invention can be widely applied to flow channel designs that require highly accurate flow rate control.

Diagram of microfluidic chip according to the present invention Enlarged view of chamber according to the present invention Diagram showing sample flow in chamber Diagram showing sample flow in chamber Enlarged view of chamber according to the present invention Diagram showing the relationship between capillary force and contact angle Figure of conventional microfluidic chip Cross-sectional view of a conventional microfluidic chip Diagram for explaining capillary force Diagram showing sample flow process Diagram showing sample flow process Diagram showing sample flow process Diagram showing sample flow process Diagram showing sample flow process

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Microfluidic chip 2 Lower panel 3 Upper panel 4 Spacer 11 1st chamber 12 2nd chamber 13 3rd chamber 14 4th chamber 15 5th chamber 16 6th chamber 17 7th chamber 18 8th chamber 21 1st flow path 22 Second channel 23 Third channel 24 Fourth channel 25 Fifth channel 31 Sample inlet 32 Air hole 41, 42, 43 Reagent 53, 54, 55 Protrusion 61 Upper chamber 62 Lower chamber 100 Center of rotation 101 Conventional Microfluidic chip 103 Conventional third chamber 104 Conventional fourth chamber 105 Conventional fifth chamber

Claims (8)

A tunnel-shaped first flow path through which the liquid to be inspected flows, a hollow chamber for filling the liquid with the first flow path connected at the bottom, and the liquid stored in the chamber is discharged A tunnel-like second flow path connected to the bottom surface of the chamber, and a protrusion continuous in the width direction of the chamber having a height smaller than the inner wall thickness of the chamber is provided inside the chamber. The microfluidic chip in which the cross-sectional area of the gap formed by the protrusion is larger than the cross-sectional area of the first flow path . 2. The microfluidic chip according to claim 1, wherein a connection portion of the first flow path in the chamber is located at a position opposite to a connection portion of the second flow path. The microfluidic chip according to claim 1, wherein the protrusion is provided at a position where the liquid does not exist when the chamber is filled with the liquid. 2. The microfluidic chip according to claim 1, wherein surfaces of the first and second flow paths and the inner wall of the chamber are processed so as to have hydrophilicity. 2. The microfluidic chip according to claim 1, wherein the height h of the protrusion is represented by h> 0.8D, where D is the inner wall thickness D of the chamber. The microfluidic chip of claim 1, wherein the chamber has air holes. Wherein the chamber, one and the other air hole before Symbol projections is one, the microfluidic chip according to claim 1. The microfluidic chip according to claim 1, wherein the bottom surface of the chamber is hydrophilic with a contact angle of 45 degrees or less.

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