JP2023147914A - Fluid passage and use thereof - Google Patents

Abstract

To provide a fluid passage high in design freedom of transfer characteristics such as transfer directivity and a driving force of a fluid and easily manufactured.SOLUTION: This fluid passage comprises one, two or more transfer regions 2 having fine structures 4 formed so as to incline as surface free energy is gradually larger in the transfer direction of a fluid 10. The transfer regions 2 are configured to be gradually smaller in surface tension of the fluid 10 in the transfer direction. The transfer regions 2 have structural slopes of the fine structures 4.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD This specification relates to a fluid flow channel that can control fluid transfer, etc., and its use.

A fluid transfer device that moves fluid in an intended direction without using external energy is disclosed (Patent Document 1). This transfer device uses a series of alternating patterns of hydrophobic and hydrophilic surfaces to contact each surface with a single droplet, thereby directing the droplet to a surface with a large contact angle. to a surface with a small contact angle. By causing this to occur continuously, the liquid is transferred in the pattern forming direction.

Separately, a serrated convex portion with an inclined serrated surface is continuously formed, and the serrated surface has a high contact angle near the base and a low contact angle at the tip. is moved to the lower contact angle side of the sawtooth. By causing this to occur continuously, the liquid is transported in the direction in which the sawtooth is formed.

Special Publication No. 2012-503137

In the device described in US Pat. No. 5,301,300, a liquid is autonomously transported in a single intended direction when applied to a predetermined surface of the device. However, in the above-mentioned device, it is necessary to use different materials or to form sawtooth-like protrusions along the transport direction. For this reason, although it is relatively easy to transfer liquid in a single direction, it has been difficult to configure the device to transfer fluid in various directions or patterns. Furthermore, the above-mentioned apparatus utilizes transfer by repeated movement toward the low contact angle side, and the driving force for transfer cannot be said to be large.

The present specification provides a fluid flow path that has excellent flexibility in designing transfer characteristics such as directionality of fluid transfer and driving force, and can be easily manufactured. Furthermore, this specification provides use in devices and the like using such fluid flow channels.

The present inventors believe that if an inclined energy field can be created on the channel surface in which the surface free energy (surface tension) of the fluid gradually decreases, the fluid can be transferred in the direction of decreasing its surface free energy. Ta. Furthermore, since the surface free energy of a solid surface changes greatly depending on the microstructure, etc., the present inventors have found that by giving a gradient to the microstructure that increases the surface free energy of the solid, the surface free energy of the solid can be increased. We thought that it would be possible to form an energy field in which the energy gradually increases.

The present inventors gradually lowered the surface free energy of the fluid in contact with the channel surface by forming a sloped energy field so that the surface free energy of the channel surface gradually increased. It was discovered that transport is possible. On the other hand, by forming a sloped energy field so that the surface free energy of the channel surface gradually decreases, the surface free energy of the fluid in contact with the channel surface gradually increases, thereby inhibiting fluid transfer, i.e. , it has been found that it is possible to stop or hold it. This specification provides the following means based on this knowledge.

[1] A fluid flow path,
A fluid channel comprising one or more transfer regions having a microstructure formed such that the surface free energy gradually increases in the direction of fluid transfer.
[2] The fluid flow path according to [1], wherein the transfer region is configured such that the surface tension of the fluid gradually decreases along the transfer direction.
[3] The fluid flow path according to [1] or [2], wherein the transfer region has a structural slope of the microstructure.
[4] The fluid flow path according to any one of [1] to [3], wherein the fine structure includes a convex portion and/or a concave portion on the surface of the transfer region.
[5] The fluid flow path according to [4], wherein the convex portion and/or the concave portion are formed by processing the surface of the material constituting the transfer region into a concave shape.
[6] The fluid flow path according to any one of [1] to [5], wherein the transfer region has increasing chemical affinity for the fluid along the transfer direction.
[7] A part of the transfer region or separate from the transfer region, a transfer inhibition region having a fine structure formed such that the surface free energy gradually decreases in the direction of inhibiting the transfer of the fluid. The fluid flow path according to any one of [1] to [6].
[8] A fluid flow path,
A fluid flow channel comprising a transfer inhibiting region having a microstructure formed to have a slope in which surface free energy gradually decreases in a fluid transfer inhibiting direction.
[9] A fluid device comprising the fluid channel according to any one of [1] to [8].
[10] A method for manufacturing a fluid flow path, comprising:
The surface of the material constituting the fluid channel is processed to have a concave shape, and the plurality of convex and/or concave portions are inclined so that the surface free energy gradually increases in the direction of transport of the fluid transferred through the fluid channel. Alternatively, a manufacturing method comprising the step of forming a plurality of convex portions and/or concave portions so that the surface free energy gradually decreases in the direction of inhibiting the transfer of the fluid transferred through the fluid flow path. .

FIG. 3 is a diagram showing an example of an outline of the transfer region disclosed in this specification, in which (a) shows an example of the slope of surface free energy of a microstructure, and (b) shows a diagram showing an example of the slope of the surface free energy of a microstructure; (c) shows a droplet downstream of the transfer region; FIG. 3 is a diagram showing the structure of a transfer area in Example 1. FIG. 3 is a diagram showing the state of liquid transfer in the transfer region of Example 1. 7 is a diagram illustrating the structure of a transfer region and the liquid transfer state in Example 2. FIG.

TECHNICAL FIELD The disclosure herein relates to fluid flow paths and their uses. According to the fluid flow path disclosed in this specification, the transfer region in the flow path can have a microstructure formed such that the surface free energy of the flow path surface gradually increases. This, therefore, allows the transfer region to be formed without the use of dissimilar materials or the use of specific repeating patterns of serrations to autonomously transfer fluid in the intended direction. Similarly, it is also possible to have a microstructure formed so that the surface free energy of the channel surface has a slope that gradually decreases. As a result, the transfer of liquid can be easily and autonomously inhibited, as described above.

As described above, the fluid flow path disclosed in this specification has a fine structure that changes the surface free energy, so that it is possible to design the fluid transfer direction, driving force, stopping/holding, etc. With degrees of freedom, fluid transfer can be easily controlled.

FIG. 1(a) is an enlarged view of an example of the transfer region 2 of the fluid flow path. As shown in FIG. 1(a), the microstructure 4 in the transfer region 2 is made of solid material, and has a large number of cylindrical convex portions 6 whose diameter gradually decreases in the direction of the arrow. The bottom portion 8 is arranged so as to be relatively enlarged. Note that this transfer region 2 is formed by etching the surface of the Si substrate to form a convex portion 6, and the exposed bottom portion 8 and side surfaces of the convex portion 6 have a surface free energy larger than that of the convex portion 6. It is equipped with

In FIG. 1(a), the diagonally upper right side of the transfer region 2 is a region where the surface free energy of the solid is small. Here, if the surface free energy of the solid is small, the liquid (fluid) 10 on the solid has the effect of minimizing the surface free energy of the liquid itself, and as a result, as shown in FIG. 1(b), As the liquid 10 reduces its surface area, ie the contact angle increases. In this state, the surface free energy of the liquid 10 maintains a constant height.

On the other hand, in FIG. 1(a), the diagonally lower left side of the transfer region 2 is a region where the surface free energy of the solid is large. If the surface energy of the solid is large, the effect of adsorbing the liquid to the solid surface is dominant so that the surface free energy of the solid itself is minimized, and as a result, as shown in FIG. 1(c), the liquid 10 is absorbed onto the solid surface. It is adsorbed and spreads, reducing the contact angle. In this state, the surface free energy of the liquid 10 has decreased.

Objects including the liquid 10 tend to be in a state where their surface free energy becomes smaller. On the fine structure 4 where the surface free energy of the solid gradually increases, the liquid 10 will be driven to the side of the solid having a larger surface free energy in order to make its own surface free energy smaller. .

On the other hand, the surface free energy of the solid gradually decreases from the diagonally lower left to the upper right of the transfer region 2, and the surface free energy of the liquid 10 increases. will be suppressed.

Thus, the transfer region of the fluid flow path disclosed herein is achieved by driving the liquid in a direction that reduces the surface free energy of the liquid by means of a microstructure with a slope that increases the surface free energy of the solid. , capable of transporting liquids.

In FIG. 1, due to the etching of the Si substrate, the bottom 8 etc. and the top surface of the convex portion 6 have different surface free energies in the transfer region 2, and as a result, the surface free energy of the solid is The slope has been increased. However, it is clear that the surface free energy of a solid can be increased solely by the structural gradient of the microstructure, and the transfer region of the fluid flow path disclosed herein is limited to the configuration shown in FIG. It is not something that will be done.

Hereinafter, the fluid flow path (hereinafter also simply referred to as a fluid flow path) and the manufacturing method thereof disclosed in this specification will be described in detail.

(Fluid flow path)
The fluid flow path has a fluid transfer region. Here, fluid means liquid. The type of liquid is not particularly limited, and by selecting the material for forming the transfer area, a transfer area for transferring various liquids can be formed.

Examples of the liquid include hydrophilic liquids such as water, an aqueous solution containing a solute, a mixed solution with an organic solvent that is compatible with water, and a highly polar organic solvent that is compatible with water. Further, the liquid may be a lipophilic liquid, such as a non-polar organic solvent, oil or fat, or a mixture thereof.

The transfer area is an area for transferring fluid in the intended transfer direction. A fluid flow path can have one or more transfer regions. The material constituting the transfer region is not particularly limited, but a material is selected that has surface free energy suitable for controlling the direction of liquid transfer by controlling the microstructure. Those skilled in the art can appropriately select the liquid to be transferred and a material suitable for transferring such a liquid from known materials. For example, a fluid flow path has one transfer region formed from a single material. By being formed of a single material, it is easy to control the movement direction of this one transfer region, and it is also easy to manufacture such a transfer region. All transfer areas of the fluid flow path may be of the same material.

The transfer direction of the fluid in the transfer region may be a straight line, or may be a combination of two or more directional linear components, that is, a straight line having a bending point. Further, the transfer direction may be a curve. Since the transfer direction in the transfer region can be designed by the inclination of the microstructure, a variety of transfer directions can be formed even in one transfer region.

Furthermore, the transport direction may be a direction in a generally horizontal plane, but in certain cases may be a direction in an inclined plane having an angle to the vertical direction. In the case of a direction on an inclined surface, it may be directed in a direction that follows gravity (so-called downward direction), or may be directed in a direction that opposes gravity.

The transfer region has a microstructure formed such that the surface free energy gradually increases in the direction of fluid transfer. Here, the fine structure specifically refers to a geometric surface unevenness structure on the surface of the transfer region. Such an uneven structure is not particularly limited, but includes, for example, convex portions and concave portions on the surface, and a combination thereof, such as a regular or irregular repeated uneven structure.

Here, when the convex portions are formed on the surface so that they can be counted individually, the convex and convex structure can be characterized by the convex portions. Further, when the concave portions are formed on the surface so that the concave portions can be counted independently, the concave and convex structure can be characterized by the concave portions. In addition, the shape of the cross section parallel to the surface or the shape of the opening of the convex portion and the concave portion is not particularly limited, and may be rectangular, spherical, or the like. In addition, the convex portion and the concave portion may have a cross section perpendicular to the surface or an opening shape in the depth direction, but are not particularly limited to the shape of a rectangle, triangle, sphere, hemisphere, or trapezoid.

Further, examples of the regular uneven repeating structure include a wavy line structure, a comb-tooth structure, a sawtooth structure, and a fractal surface. Examples of the irregular repeating uneven structure include a surface roughened by plasma treatment, etching treatment, or the like.

In other words, a fine structure having a slope in which the surface free energy gradually increases in the direction of transport, in other words, the liquid repellency of the liquid decreases as the surface tension of the liquid gradually decreases in the direction of transport. It can be said that it is structured as follows.

Such a gradient of surface free energy can be imparted by a structural gradient of the uneven structure. In imparting such a structural gradient, in addition to the surface free energy inherent in the material constituting the transport region, the Wenzel equation for rough surfaces in the Wenzel state, which is well known to those skilled in the art, and the Cassie-Baxter equation for composite surfaces, , pinning effect, etc. are referred to as appropriate. In addition to the individual shape, the pattern and orientation of the uneven structure are important for the relationship between the uneven structure and liquid repellency. may reduce the liquid repellency of

In other words, the microstructure has a slope in which the surface free energy gradually increases in the direction of transport, in other words, the surface tension of the liquid gradually decreases in the direction of transport, and the liquid repellency decreases. It can be said that it is configured. Reducing the liquid repellency may be achieved by, for example, increasing the characteristics opposite to the various known uneven structures that improve liquid repellency.

In order to change the liquid repellency, a different number and/or a different size and/or a different arrangement density may be applied to the uneven structure. For example, the number of convex portions or concave portions may be increased or decreased, the size may be increased or decreased, and the density may be increased or decreased. For example, gradually decreasing the number/size/density of convexities or concavities may increase the surface free energy, and vice versa.

Another example is an increase/decrease in the amplitude, period, etc. of the unevenness in the uneven repeating structure. For example, by gradually decreasing the amplitude/period of the asperities in a concavo-convex repeating structure, the surface free energy may increase, and vice versa.

Furthermore, in addition to or independently of these, the shape of the uneven structure itself may be gradually changed to increase the surface free energy.

In addition to such changes in the uneven structure, by increasing the chemical affinity with the liquid in at least a portion of the uneven structure, the surface free energy of the uneven structure can be increased as a result. For example, if the surface of the material forming the transfer region is processed into a concave shape by chemical etching or plasma etching to form convex portions, concave portions, and a repeated structure of these concave and convex portions, the surface of the material that forms the transfer region is etched and exposed from the material. In addition to improving physical affinity due to surface roughening caused by etching, chemical species generated by etching may be generated or impurities may remain on the etched surface. The formation of such surface conditions may increase chemical affinity for liquids. For example, when multiple convex parts are formed by machining the surface of a material into concave shapes, the tops of the convex parts have the same chemical affinity as before processing, but the exposed areas around the convex parts Since the bottom portion and the side surface of the convex portion are exposed due to processing, the physical affinity and chemical affinity for the liquid may change as a result of processing.

For example, if the liquid is water and the material forming the transfer region is a monocrystalline or polycrystalline Si-based material, the exposed surface will form an uneven structure and increase the chemical affinity for water. This may increase the driving force for liquid transfer.

Also disclosed herein are transport regions that are sloped such that such concavities result in increased surface free energy of the solid, such as by creating a heterogeneous surface and increasing chemical affinity for the liquid. included in the transfer region of the fluid flow path.

As described above, in the transfer region of the fluid channel, the direction of liquid transfer can be controlled by providing a fine structure with an inclination that increases the surface free energy. Therefore, precise control of the transfer direction is also possible. In addition, in this transfer region, by applying fine structure manufacturing techniques in semiconductors or the like, it is possible to easily form a gradient in surface free energy in the fine structure.

According to this specification, by gradually increasing the surface free energy of the transfer region, it is possible to transfer the liquid according to the direction of the inclination. At the same time, it is also possible to form a transport-suppressing region having a microstructure formed such that the surface free energy gradually decreases. In such a transfer suppression area, transfer of liquid in the inclined direction can be suppressed. That is, the liquid can be stopped or held. By providing such a transfer inhibiting area, the control of the liquid transfer direction can be further facilitated and the accuracy can be further improved. Further, by providing such a transfer inhibiting area, the liquid can be held or stopped in the intended area.

The fluid flow path may include such a transfer inhibiting region as part of or independent of the transfer region. The transfer inhibiting area may be formed, for example, at a portion or an end of the transfer area, or may be formed simultaneously with the transfer area from a material constituting the transfer area.

(fluid device)
The fluidic devices disclosed herein include the various transfer regions or fluid flow paths described above. Such fluidic devices can easily transport fluid in multiple different directions. Therefore, it is possible to provide a fluid device that is smaller in size and capable of highly accurate liquid control than in the past. Fluid devices are not particularly limited as long as they involve the flow of liquid, but include various chemical devices such as biodevices used for various diagnoses, tests, and measurements, evaluation devices for environmental evaluation, etc. Examples include fluidic devices that perform reactions.

(Method for manufacturing fluid channel)
The method for manufacturing a fluid channel disclosed herein involves processing the surface of a material constituting the fluid channel into a concave shape to form a plurality of convex portions and/or concave portions for the fluid to be transferred through the fluid channel. The surface free energy gradually increases in the direction of inhibiting the transfer of the fluid transferred through the fluid flow path. The method may include a step of forming the surface to have a slope that becomes smaller. According to this manufacturing method, the surface free energy can be changed easily and in various forms, making it possible to highly control the transfer of liquid.

Such a plurality of concave portions and convex portions can be obtained by processing the material constituting the transfer region into a concave shape by various types of etching, cutting, etc. As these various concave processing methods, methods known in the semiconductor field can be appropriately adopted. For example, when physical etching such as sputter etching, gas etching, and plasma etching including reactive ion etching (RIE) is used, the processed surface can be expected to become rougher (increase in the uneven area), leading to an increase in surface free energy. It can be effective.

Hereinafter, examples will be described as specific examples to more specifically explain the disclosure of this specification. The following examples are intended to illustrate the disclosure herein and are not intended to limit its scope.

In this example, a transfer region was formed using a Si single crystal substrate, a predetermined amount of water was dropped onto the transfer region, and the movement of water on the transfer region was observed.

As shown in Fig. 2, the surface of the Si single crystal substrate was etched by RIE on the short side of the substrate, including point A in the figure, under conditions in which physical etching due to the impact of CF4 gas on the substrate was dominant. A plurality of cylindrical bodies with a diameter of 50 μm and a height of 200 nm are formed in a band-shaped region extending along the direction (see frame A in the figure), and further, columns with gradually smaller diameters and the same height (see frame A in the figure) are formed in a band-shaped region extending along the direction An array of cylindrical bodies with a diameter of 200 nm and a height of 200 nm was formed across multiple strip regions, and in a strip region including point B in the figure, an array of cylindrical bodies with a diameter of 200 nm and a height of 200 nm was formed (see frame B in the figure). ). The left diagram in FIG. 2 is an optical microscope image showing the periodic structure in the substrate, and the right diagram is an electron microscope image in the vicinity of point A and point B.

In this substrate, the top surface of the cylinder has the surface free energy of the original Si substrate, but on the outer peripheral surface and exposed bottom of the cylinder, due to the action of RIE, chemical species remained and the rough surface It is thought that both the chemical affinity and the physical affinity are improved by the oxidation, and it can be said that the surface free energy of these surfaces is higher than that of the top surface. As a result, it was considered that the surface free energy of the transfer region gradually increased from the A point side to the B point side.

A droplet of 1 to 3 μl of pure water was continuously dropped at point A on the surface of the processed Si substrate, and the shape of the droplet on the substrate was observed. Furthermore, 1 to 5 μl of pure water droplets were continuously dropped at point B and observed in the same manner. The results are shown in Figure 3.

As shown in the left diagram of FIG. 3, the pure water dropped at point A showed a tendency to gradually expand toward point B (in the X direction) as the amount of dropped water increased. On the other hand, as shown in the right diagram of FIG. 3, the pure water dropped at point B could not expand toward point A and tended to remain at point B even if the amount of water dropped increased.

From the above, by forming a fine structure like the Si substrate produced in this example, the surface free energy in the transfer region can be increased from point A to point B, and the direction of liquid transfer can be changed to A. It turns out that it is possible to control the direction from point to point B. It has also been found that by decreasing the surface free energy from point B to point A, it is possible to retain or stop the liquid at point B.

In this example as well, a transfer region was formed using a Si single crystal substrate, a predetermined amount of water was dropped onto the transfer region, and the movement of water on the transfer region was observed.

As shown in the left figure of Figure 4, the surface of a Si single crystal substrate is etched in a reverse direction from the center of the substrate to the left and right sides using RIE, under conditions where physical etching is dominant due to the collision effect of CF4 gas on the substrate. A plurality of V-shaped strip areas were set in the vertical direction of the substrate. In the strip-shaped region at the uppermost end of the substrate, a plurality of cylindrical bodies were formed which gradually decreased in diameter from 5 μm to 4 μm (height 200 nm) in the left-right direction from the center. Further, in a band-shaped region toward the lower end of the substrate, an array of cylindrical bodies (height: 200 nm) was formed in the horizontal direction from the center of the substrate, starting from a diameter smaller than 5 μm and gradually decreasing in diameter in the horizontal direction. These strip-shaped regions are sequentially formed, and in the strip-shaped region at the bottom of the substrate, an array of cylindrical bodies (height 200 nm) whose diameter gradually decreases from 1.2 μm to 0.2 μm from the center of the substrate in the left-right direction is formed. did. As a result, in the center of the substrate, the diameter size of the cylinders decreases from 5 μm to 1.2 μm, and at both ends of the substrate, the diameter size of the cylinders decreases from 4 μm to 0.2 μm. became. Note that the left diagram in FIG. 4 is an optical microscope image showing a periodic structure.

In this substrate, as in Example 1, the top surface of the cylinder has the surface free energy of the original Si substrate, but the outer peripheral surface and exposed bottom of the cylinder have chemical affinity and physical free energy. It can be said that the surface free energy of these surfaces is higher than that of the top surface. In other words, a single-crystal substrate has a gradient surface free energy structure in which the surface free energy gradually increases from the center of the substrate in the left-right direction, and also gradually increases from the top to the bottom of the substrate. It was thought that this was done.

A droplet of 5 μl of pure water was continuously dropped at point C on the surface of the processed Si substrate, and the shape of the droplet on the substrate was observed. The results are also shown in FIG. 3.

As shown in the right diagram of FIG. 3, the pure water dropped at point C moved diagonally downward to the right from the band-shaped region including point C, and further moved downward, but did not cross the center line.

From the above, in the Si substrate manufactured in this example, the surface free energy gradually increases in the horizontal direction from the center of the substrate, and also gradually increases from the top to the bottom of the substrate. It is thought that due to the formation of a free energy gradient structure, a driving force directed diagonally downward acted on the droplet, causing it to move diagonally downward to the right.
In this way, it has been found that by combining the surface free energy gradient structures (in this example, a combination of bidirectional gradient structures), it is possible to design the direction of liquid transport and direct it in any direction.

Claims (10)

A fluid flow path,
A fluid channel comprising one or more transfer regions having a microstructure formed such that the surface free energy gradually increases in the direction of fluid transfer. The fluid flow path according to claim 1, wherein the transfer region is configured such that the surface tension of the fluid gradually decreases along the transfer direction. 3. A fluid flow path according to claim 1 or 2, wherein the transfer region has a structural slope of the microstructure. The fluid flow path according to any one of claims 1 to 3, wherein the microstructure includes convex portions and/or concave portions on the surface of the transfer region. The fluid flow path according to claim 4, wherein the convex portion and/or the concave portion are formed by processing a surface of a material forming the transfer region into a concave shape. A fluid flow path according to any preceding claim, wherein the transfer region has increasing chemical affinity for the fluid along the transfer direction. A transfer inhibiting region is provided, which is part of the transfer region or separate from the transfer region, and has a microstructure formed such that the surface free energy gradually decreases toward a direction in which the fluid transfer is inhibited. Item 7. The fluid flow path according to any one of Items 1 to 6. A fluid flow path,
A fluid flow channel comprising a transfer inhibiting region having a microstructure formed to have a slope in which surface free energy gradually decreases in a fluid transfer inhibiting direction. A fluidic device comprising the fluid flow path according to any one of claims 1 to 8. A method of manufacturing a fluid channel, the method comprising:
The surface of the material constituting the fluid channel is processed to have a concave shape, and the plurality of convex and/or concave portions are inclined such that the surface free energy gradually increases in the direction of transport of the fluid transferred through the fluid channel. Alternatively, a manufacturing method comprising the step of forming a plurality of convex portions and/or concave portions so that the surface free energy gradually decreases in the direction of inhibiting the transfer of the fluid transferred through the fluid flow path. .