KR102374148B1 - Aspiration mediated microliquid patterning method within a microfluidic device - Google Patents

Abstract

An object of the present invention is to provide a microfluidic patterning method based on suction in a microfluidic device for patterning a fluid in an open microfluidic device capable of rapidly and precisely microfluidic patterning while repeating injection and aspiration into the microfluidic device. . The suction-based microfluidic patterning method in a microfluidic device according to an embodiment of the present invention has a different height and is connected to a rail structure including a fluid injection unit and a fluid suction unit, a rail structure and a lower communication line, and a culture medium for cell culture. A microfluidic device preparation step of preparing a microfluidic device formed in an open structure, including a chamber portion having a culture medium storage unit capable of injection, by injecting a fluid through a fluid injection line of a rail structure with the culture medium storage unit at the lower part of the rail structure A rail structure fluid filling step that isolates the communication line, and the formation of a microfluidic patterning barrier rib that sucks the fluid injected into the rail structure through the fluid suction part of the rail structure and forms an empty space surrounded by the microfluidic patterning barrier at the lower part of the rail structure includes steps.

Description

Aspiration-based microfluidic patterning method in microfluidic devices

The present invention relates to a suction-based microfluidic patterning method in a microfluidic device.

Microfluidic devices are being used in various research fields such as biology and chemistry, including the development of organ-on-a-chip through three-dimensional cell co-culture. The organ imitation chip is a technology that imitates the organ's, dynamics, and physiological functions by culturing the characteristic cells that make up the organs of the human body. Using such a chip, it is possible to study the mechanism of cellular response to physical and chemical stimuli, and it has the potential to be used as a model to evaluate the performance and toxicity of drugs in the preclinical stage of new drug development.

Co-culture of various cells constituting an organ plays a key role in mimicking an environment similar to the human body in the organ-simulating chip, and the structure within the microfluidic device helps to arrange cells similar to the organ. With respect to cell co-culture using a microfluidic device, Korean Patent Application No. 10-2012-0040613 provides an ex vivo blood vessel generating apparatus. The '613 patent discloses that a plurality of microfluidic channels for microfluid patterning are separated by micropillars that are repeated at specific intervals, and a plurality of microfluidic channels are used by using the property that the fluid does not easily move through the narrow gaps between the micropillars. A hydrogel containing different cells can be patterned in each channel. In the patterning method using the bursting pressure in the narrow gap of these micro-pillars, the patterning success rate is different depending on the skill of the experimenter because the injection pressure must be smaller than the bursting pressure. In addition, since the surface must have hydrophobic properties, it is generally made of polydimethylsiloxane (PDMS), but PDMS has a disadvantage in that it is not suitable for mass production. As such, the microfluidic device according to the prior art is not suitable for mass production or has a large error between experimenters, so that there is a limitation in yield and efficiency in securing a large number of experimental results.

Korean Patent Application No. 10-2012-0040613

An object of the present invention is to provide a microfluidic patterning method based on suction in a microfluidic device for patterning a fluid in an open microfluidic device capable of rapidly and precisely microfluidic patterning while repeating injection and aspiration into the microfluidic device. .

Another object of the present invention is to provide a method for co-culturing heterogeneous cells using the patterning method of the present invention.

The suction-based microfluidic patterning method in a microfluidic device according to an embodiment of the present invention has a different height and is connected to a rail structure including a fluid injection unit and a fluid suction unit, a rail structure and a lower communication line, and a culture medium for cell culture. A microfluidic device preparation step of preparing a microfluidic device formed in an open structure including an injectable culture medium storage unit, injecting fluid through the fluid injection unit of the rail structure to isolate the culture medium storage unit and the communication line from the lower part of the rail structure A fluid filling step, and a microfluidic patterning barrier rib forming step of sucking the fluid injected into the lower part of the rail structure through the fluid suction part of the rail structure to form an empty space surrounded by the microfluidic patterning barrier rib in the lower part of the rail structure.

Here, the rail structure includes a first rail having a first height with respect to the bottom surface of the chamber unit, and a first rail having a second height lower than the first height and provided along the longitudinal direction of the first channel from both sides of the first rail in the width direction. 2 rails may be included. The first rail has openings on both sides along the longitudinal direction and can be selectively used as a fluid injection part or a fluid suction part.

In the microfluidic patterning barrier rib forming step, the fluid located under the first rail is sucked through the fluid suction unit, and the fluid located at the second rail remains to form the microfluidic patterning barrier rib, and as a result, the first rail and the patterning barrier rib under the first rail , it is possible to form a channel surrounded by the bottom surface. Here, the condition for allowing only the liquid under the first rail to be sucked without the liquid under the second rail being sucked is determined through comparison between the critical capillary pressures of the air-liquid interfaces of the liquid filled under the rail structure.

At least a surface of the microfluidic device in contact with the fluid may be formed of a hydrophilic material.

If the suction-based microfluidic patterning method in the microfluidic device of the present invention is used in an open microfluidic device including a rail structure, when the sufficiently injected fluid under the rail structure is sucked, the fluid can be patterned only in the portion where the capillary force is strongly applied. can

According to an embodiment of the present invention, the rail structure is in a form in which a second rail with a short length spaced apart from the bottom part provided in the lower part of the chamber in the height direction surrounds the first rail with a relatively long length spaced apart from the bottom part. Therefore, when the fluid is injected and sucked through the opening located on the first rail, the fluid can be patterned only under the second rail.

Using the suction-based microfluidic patterning method in a microfluidic device of the present invention, it is possible to rapidly and precisely pattern microfluids while suctioning excess fluid with a pipette and then repeating injection and suction into several microfluidic devices.

In addition, when the second rail surrounds the plurality of first rails, it is possible to form a plurality of microfluidic channels by one suction of the hydrogel solution by adjusting the size of the opening. Therefore, the suction-based microfluidic patterning method in a microfluidic device of the present invention can maximize the efficiency of an experiment using a microfluidic device, and in particular, can be effectively used for co-culture of multiple cells.

1 is a diagram illustrating a basic structure of a microfluidic device for microfluidic patterning according to an embodiment of the present invention.
2 is a diagram illustrating a microfluidic patterning process based on suction in a microfluidic device according to an embodiment of the present invention.
3 is a diagram illustrating variables of a rail structure affecting microfluidic patterning.
4 is a view showing the patterning result according to the relative magnitude of the critical capillary pressure of each interface.
5 is a diagram illustrating a theoretical dimensional condition (yellow green region) that succeeds in patterning with the critical capillary pressure of each interface obtained earlier in the basic rail structure and a theoretical dimensional condition (pink region) that fails. Green dots and red marks indicate experimental success and failure conditions, respectively.
6 is a diagram illustrating an open microfluidic device capable of forming a plurality of microfluidic channels by one suction of a hydrogel solution.
7 is a diagram illustrating a process of forming a plurality of microfluidic channels through a single suction in the microfluidic device of FIG. 6 .
8 is a diagram illustrating an open microfluidic device for comparison of angiogenesis capability.
9 is a diagram illustrating an embodiment of comparison of blood vessel generating ability.
FIG. 10 is a diagram illustrating a blood vessel generation result for each cell in a region of interest (ROI) of FIG. 9 .
FIG. 11 is a diagram quantitatively illustrating the ability of each cell to generate blood vessels through the image analysis of FIG. 10 .

The terminology used herein is for the purpose of referring to specific embodiments only, and is not intended to limit the invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. The meaning of "comprising," as used herein, specifies a particular characteristic, region, integer, step, operation, element and/or component, and other specific characteristic, region, integer, step, operation, element, component, and/or group. It does not exclude the existence or addition of

Although not defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Commonly used terms defined in the dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and unless defined, are not interpreted in an ideal or very formal meaning.

Hereinafter, with reference to the accompanying drawings, the embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein.

1 illustrates a microfluidic device 100 in a basic form capable of performing a microfluidic patterning method according to an embodiment of the present invention. Referring to FIG. 1 , the microfluidic device 100 according to an embodiment of the present invention includes a rail structure 120 having a different height and including a fluid injection unit and a fluid suction unit, and a rail structure 120 and a lower communication line. It may be formed in an open structure including a chamber unit 110 having a culture medium storage unit 130 that is connected and capable of injecting a culture medium for cell culture. The rail structure 120 may be connected to a well wall forming an outer wall of the chamber unit 110 . The well wall is attached to the bottom part 112 to provide a function of supporting the rail structure 120 and a culture solution storage unit 130 capable of filling the culture solution during cell culture. The chamber part 110 and the bottom part 112 may be integrally formed as needed. The microfluidic device 100 according to the embodiment of the present invention may be formed of a hydrophilic material so that at least a surface in contact with the fluid has a hydrophilic surface. Here, the fluid may include a hydrogel solution. The rail structure 120 has a first rail 122 having a first height with respect to the bottom surface of the chamber unit 110 , and a second height lower than the first height from both sides in the width direction of the first rail 122 . A second rail 124 provided along the length direction of the first rail 122 may be included. The rail structure 120 may be formed in such a way that a short second rail 124 spaced apart from the bottom part 112 surrounds the first rail 122 with a relatively long length spaced apart from the bottom part 112 . can The rail structure 120 may include a second rail 124 surrounding the first rail 122 . The first rail 122 has openings 126 on both sides along the longitudinal direction and may be selectively used as a fluid injection unit or a fluid suction unit. Here, the opening 126 may include a first opening 126a and a second opening 126b. However, the first opening 126a and the second opening 126b are separated in terms of location, and the functions of the first opening 126a and the second opening 126b may be substituted if necessary. For example, the opening 126 through which the fluid is introduced or sucked may be divided into the first opening 126a and the opening 126 through which the air is sucked may be divided into the second opening 126b. Accordingly, unless otherwise limited, the fluid may be introduced through any one of the openings 126 . And when the fluid is sucked through one of the openings 126 , it may be described that air is introduced through the other opening 126 on the opposite side. In this aspect, when the fluid is injected and sucked through the first opening 126a located in the first rail 122 , the fluid may be patterned only under the second rail 124 . On the other hand, when the second rail 124 surrounds the plurality of first rails 122 , a plurality of empty spaces may be formed by one suction of the hydrogel solution through size adjustment of the opening 126 . When patterning with a hydrogel solution, a plurality of empty spaces form a microfluidic channel surrounded by the hydrogel partition wall, the first rail 122 , and the bottom part 112 . Therefore, the efficiency of the experiment using the microfluidic device 100 can be maximized. In particular, it can be effectively used for co-culture of multiple cells.

2 is a diagram sequentially illustrating a process of a microfluidic patterning method according to an embodiment of the present invention. Referring to FIG. 2, the microfluidic patterning method based on suction in a microfluidic device according to an embodiment of the present invention includes a microfluidic device preparation step (S210), a rail structure lower fluid filling step (S220), a fluid suction step (S230), And it includes a microfluidic patterning barrier rib forming step (S240).

In the microfluidic device preparation step (S210), the rail structure 120 having a different height and including a fluid part and a fluid suction part, the rail structure 120 and the lower communication line are connected, and the culture solution for cell culture can be injected. This is a step of preparing the microfluidic device 100 formed in an open structure including the chamber part 110 having the storage part 130 .

The rail structure fluid filling step (S220) is a step of isolating a communication line with the culture solution storage unit 130 from the lower portion of the rail structure 120 by injecting a fluid through the fluid injection unit of the rail structure 120 .

The fluid suction step S230 is a step of sucking the fluid injected into the rail structure 120 through the fluid suction part of the rail structure 120 . The fluid suction step may be continuously implemented in one step with the microfluidic patterning barrier rib forming step.

The microfluidic patterning barrier rib forming step S240 is a step of forming the barrier rib 140 so that the lower portion of the first rail is emptied and the liquid remains under the second rail so that the lower portion of the first rail becomes a new flow path. In the microfluidic patterning barrier rib forming step (S240), the fluid injected into the first rail 122 is sucked through the fluid suction part, and the fluid injected into the second rail 124 remains in a preset shape, so that the microfluidic patterning barrier rib 140 ) can be formed. As described above, using the suction-based microfluidic patterning method in the microfluidic device according to the embodiment of the present invention, in the open microfluidic device 100 including the rail structure 120 , it is sufficiently injected under the rail structure 120 . When the fluid is sucked, the fluid can be patterned only on the part where the capillary force is strongly applied. If several microfluidic devices 100 are in a ready state, after sucking the excess fluid with a pipette, repeat injection and suction of the fluid into several microfluidic devices 100 to form microfluidic patterning quickly and precisely. there is.

)은 수학식 1로 표현할 수 있다.When the fluid is filled under the rail structure 120 by injecting the fluid through the first opening 126a of the first rail 122 and sucked, air is introduced into the second opening 126b, which is the opposite opening 126, which is sucked in. The space below the first rail 122 is emptied as it enters. In more detail, the reason why the fluid is patterned only under the second rail 124 will be described. By sufficiently filling the underside of the rail structure 120 with fluid, a fluid-gas interface is created in the side under the second rail 124 and in the second opening 126b opposite the first opening 126a for injection. Then, when the fluid is sucked, the interfaces change shape as the volume of the fluid decreases, and when the critical capillary pressure that each interface can have is exceeded, the interface moves. Capillary pressure can be calculated by the Young-Laplace equation (Δp=γκ=γ(1/R ₁ +1/R ₂ )) expressed as the product of surface tension coefficient (γ) and curvature (κ). And the maximum capillary pressure that an interface can have can be assumed when the interface is concave and semicircular (when the radius of curvature (R) is the smallest) because the surface is hydrophilic. Critical capillary pressure at the interface from the side under the second rail 124 (

) can be expressed by Equation 1.

[Equation 1]

/h+1/η)Δp = γ(2cos

/h+1/η)

는 접촉각, h는 제2 레일(124)의 높이, η는 레일 길이방향의 곡률반경을 나타낸다.here,

is a contact angle, h is a height of the second rail 124, η is a radius of curvature in the longitudinal direction of the rail.

~0°이므로 제2 레일(124) 아래의 임계 모세관 압력(

)은 수학식 2로 간략히 표현할 수 있다.Since h<<η and it is a hydrophilic surface,

~0°, so the critical capillary pressure below the second rail 124 (

) can be expressed briefly in Equation (2).

[Equation 2]

)은

으로 표현된다. 이 두 임계 압력의 상대적인 크기에 의해 이동하는 계면이 결정된다.

일 경우 개구부(126)쪽 계면이 이동하면서 제1 레일(122)의 아래쪽에 새로운 계면이 형성된다. By the same logic, the critical capillary pressure at the interface at the opposite opening 126 sucking in

)silver

is expressed as The moving interface is determined by the relative magnitude of these two critical pressures.

In this case, as the interface toward the opening 126 moves, a new interface is formed under the first rail 122 .

)은 수학식 3으로 표현된다.The new interface under the first rail 122 can also be calculated by the Young-Laplace equation, and the critical capillary pressure below the first rail 122 (

) is expressed by Equation (3).

[Equation 3]

)

)

은 제1 레일(122)의 폭,

는 제1 레일(122)의 높이를 나타낸다.here,

is the width of the first rail 122,

represents the height of the first rail 122 .

일때, 제1 레일(122) 아래의 계면이 빨아들이는 개구부(126)까지 이동하여 공기가 빨리기 시작하면 유체의 부피 감소는 종료되고 결국 제2 레일(124)의 아래에만 유체가 남는다.The moving interface is determined by the relative magnitude of the critical capillary pressure of the interface under the first rail 122 and the side interface under the second rail 124 .

At one time, when the interface under the first rail 122 moves to the suction opening 126 and the air starts to speed up, the volume reduction of the fluid ends and the fluid remains only under the second rail 124 .

)이 가장 큰 경우로, 제2 레일(124)의 아래쪽에 유체가 계속 남아있는다. 이와는 달리, 가운데 열은 빨아들이는 반대편 개구부(126)에서 기체가 들어오지 못하고 제2 레일(124) 아래의 계면이 이동하면서 패터닝에 실패하는 경우를 나타낸다. 그리고 오른쪽 열은 반대편 개구부(126)에서 기체가 들어오기는 했지만 제1 레일(122) 아래 계면의 임계 모세관 압력이 더 커서 제2 레일(124) 아래의 계면이 이동하여 패터닝에 실패한 경우를 보여준다. 3 shows the parameters of the rail structure affecting microfluidic patterning, and FIG. 4 shows the patterning results according to the relative magnitude of the critical capillary pressure at each interface. Referring to FIG. 4 , the left column shows the critical capillary pressure below the second rail 124 (

) is the largest, and the fluid continues to remain under the second rail 124 . Contrary to this, the middle row indicates a case in which the gas does not enter through the suction opposite opening 126 and patterning fails as the interface under the second rail 124 moves. And, the right column shows a case where gas entered from the opposite opening 126 but the critical capillary pressure at the interface under the first rail 122 was greater, so that the interface under the second rail 124 moved and patterning failed.

일 때_, 즉,

을 기준으로 이론적 경계가 나누어지고 실제 실험에서는 대체로 만족하는 것을 확인하였다. 아래 그래프는 제2 레일 아래 측면에 있는 계면과 제1 레일 아래에 있는 계면에서의 패터닝을 위한 치수 조건을 나타낸다.

일 때, 즉

)을 기준으로 이론적 경계가 나누어지고 실제 실험에서도 일치하는 경향을 확인하였다.FIG. 5 shows dimensional conditions for successful patterning and failure for patterning with the critical capillary pressure of each interface obtained earlier in the basic rail structure having a length of 5 mm and a width of 1 mm. The graph above shows the dimensional conditions for patterning at the interface at the side under the second rail and at the interface at the opening opposite to the sucking.

When _, that is,

It was confirmed that the theoretical boundary is divided based on , and that it is generally satisfactory in the actual experiment. The graph below shows the dimensional conditions for patterning at the interface under the second rail and at the interface under the first rail.

when i.e.

), the theoretical boundaries are divided and the tendency to agree in actual experiments was confirmed.

By utilizing this design rule, as shown in FIG. 6 , several broken fluid channels can be formed by one suction in the rail structure. 6 is an open microfluidic device in which three first rails of 'S', 'N', and 'U' are surrounded by a second rail of rectangular shape. It becomes smaller as it goes up to U1. In this structure, when the fluid is sufficiently filled under the rail and sucked in, a channel is sequentially formed as gas flows in from an opening having a large opening as shown in FIG. 7 .

As described above, the suction-based hydrogel patterning method in the microfluidic device can pattern the fluid only under the second rail by using the phenomenon of movement from the interface where the magnitude of the critical capillary pressure is small. And when the hydrogel solution is patterned, a new channel is formed and another fluid can be injected. In addition, multiple channels can be formed with one suction.

8 is a structural diagram of a microfluidic device used in a multi-cell co-culture experiment using such a patterning method. Referring to FIG. 8, in a form in which four first rails 250 μm away from the bottom are surrounded by a second rail 75 μm away from the bottom of 5 mm x 5 mm, Four microfluidic channels can be formed by injecting and then aspiration of the hydrogel solution through the opening located in the

9 shows an example in which the angiogenesis ability of various cells is compared through multicellular co-culture. After mixing and patterning the vascular cells with the hydrogel under the second rail, different cells for comparison in the angiogenesis ability are mixed in the hydrogel and cultured for 5 days in the four channels created by the patterned hydrogel barrier. Vascular cells were stained and imaged. Lung fibroblasts (LF) were injected into the upper left channel, the glioblastoma cell line U87MG into the upper right channel, lung cancer cell line H1299 into the lower left channel, and cell-free hydrogel into the lower right channel. A region of interest was set around the channel into which cells to compare the angiogenesis ability were injected.

FIG. 10 is a diagram illustrating an angiogenesis result for each cell in a region of interest (ROI) of FIG. 9 , and FIG. 11 is a diagram quantitatively illustrating an angiogenesis ability for each cell through the image analysis of FIG. 10 . . 10 shows the results of angiogenesis in a region of interest for each cell. By quantifying the area of blood vessels in the region of interest, as shown in FIG. 11 , the ability to generate blood vessels for each cell can be compared.

The microfluidic patterning method proposed in the embodiment of the present invention uses a method of injecting and sucking a fluid under the rail structure 120. When the fluid is injected and sucked, the fluid can be patterned only under the second rail. In this microfluidic patterning method, the patterning result may be determined according to the magnitude of the relative maximum capillary pressure of the fluid-air interfaces generated when the rail structure 120 is filled below. In the case of using a general laboratory micropipette at the fluid-air interface, the effect of suction pressure by the pipette is insignificant within the pressure range that the pipette can apply. volume remains. On the other hand, in the method of patterning by injecting a fluid into the inner edge of the microwell to pattern the fluid in the microfluidic channel coupled with the microwell, when the volume of the fluid injected by the pipette is not constant, the volume of the fluid patterned on the rail structure The quantity will not be constant. Therefore, when the accuracy of the pipette is lowered because a quantitative volume must be injected, the shape of the hydrogel interface changes depending on the volume difference, so that different results can be obtained during co-culture. In order to inject a large number of devices when using a general pipette, it is necessary to repeat the suction and injection of a fixed amount of fluid. However, the method used in the embodiment of the present invention can pattern a constant volume of fluid regardless of the accuracy of a used pipette because a certain amount is left by over-injecting and then sucking the fluid. Thanks to these advantages, it is possible to rapidly pattern by suctioning enough hydrogel to fill a number of microfluidic devices, then injecting it into all the rail structures 120 of each microfluidic device and repeating the suction. Due to the nature of the hydrogel, it gradually hardens over time and the properties change sensitively accordingly, so by quickly filling all microfluidic devices, the deviation of physical properties between patterned hydrogels in the same experiment can be minimized.

In addition, since the injection method at the corner cannot fix the tip of the pipette, it has factors that reduce the accuracy of patterning, such as irregular patterning positions and shaking during fluid injection. In the embodiment of the present invention, since the opening is defined, it is possible to provide a user with an accurate patterning position and stability during fluid injection and suction.

The conventional microfluid patterning method using a hydrophilic surface is a method of patterning the fluid at the bottom of the rail by flowing a fluid through the edge of the microwell. Therefore, for microfluidic patterning, the inner edge path of the microwell must form one or more closed curves. However, the microfluidic patterning method according to the embodiment of the present invention has an advantage in that the degree of freedom of the structure is higher when designing the microfluidic device because the rail structure 120 can be positioned regardless of the edge path of the microwell.

Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and it is possible to carry out various modifications within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and this is also It goes without saying that they fall within the scope of the present invention.

100 ; microfluidic device 110 ; chamber part
112 ; bottom 120 ; rail structure
122; first rail 124 ; 2nd rail
126 ; opening 126a; first opening
126b; second opening 130 ; culture medium storage
140 ; microfluidic patterned barrier ribs

Claims (10)

It is formed in an open structure including a rail structure having different heights and including a fluid injection unit and a fluid suction unit, and a chamber unit connected to the rail structure and a lower communication line and having a culture medium storage unit capable of injecting a culture material for cell culture. A microfluidic device preparation step of preparing a microfluidic device,
A rail structure fluid filling step of injecting a fluid through the fluid injection part of the rail structure to fill the lower portion of the rail structure with liquid, and
A microfluidic patterning barrier rib forming step of forming an empty space surrounded by the patterned liquid barrier rib under a part of the rail structure by sucking the fluid injected into the rail structure through the fluid suction part of the rail structure
includes,
The condition for forming the microfluidic patterning barrier rib is a suction-based microfluidic patterning method in a microfluidic device that is determined by the magnitude of the relative critical capillary pressure (Δp) of the gas-liquid interface of the liquid injected under the rail structure. In claim 1,
The rail structure is
A first rail having a first height with respect to the bottom surface of the chamber part, and
A suction-based microfluidic patterning method in a microfluidic device comprising a second rail having a second height lower than the first height and provided along a longitudinal direction of the first rail on both sides of the width direction of the first rail. In claim 2,
The first rail
A suction-based microfluidic patterning method in a microfluidic device having openings on both sides along the longitudinal direction and selectively used as the fluid injection unit or the fluid suction unit. In claim 3,
In the microfluidic patterning barrier rib forming step, when suction is performed through the fluid suction unit, the fluid located under the first rail is sucked and the fluid located under the second rail remains, forming the microfluidic patterning barrier. Suction in the microfluidic device based microfluidic patterning method. In claim 4,
The critical capillary pressure (Δp) is a microfluidic patterning method based on suction in a microfluidic device expressed by Equation (1).
Equation (1)
Δp=γκ
where γ is the surface tension and κ is the curvature of the gas-liquid interface In claim 5,
Critical capillary pressure below the second rail (

) is a microfluidic patterning method based on suction in a microfluidic device expressed by Equation (2).
Equation (2)

here

is the contact angle, h is the height of the second channel, η is the radius of curvature in the longitudinal direction of the channel In claim 5,
the critical capillary pressure of the opening (

) is a microfluidic patterning method based on suction in a microfluidic device expressed by Equation (4).
Equation (4)

where D is the diameter of the opening In claim 5,
Critical capillary pressure below the first rail (

) is a microfluidic patterning method based on suction in a microfluidic device expressed by Equation (3).
Equation (3)

Here, W _HR is the width of the first rail, H is the height of the first rail In claim 5,
The condition for forming the microfluidic patterning barrier rib is the critical capillary pressure (

) is the critical capillary pressure at the interface of the opening (

) and the critical capillary pressure at the interface below the first rail

A larger case, aspiration-based microfluidic patterning method in microfluidic devices. In claim 1,
In the microfluidic device, at least a surface in contact with the fluid is formed of a hydrophilic material.

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