JP2009233843A - Micro-machining method and apparatus for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new micro-machining method as a micro-size machining method using a flexible and self-adhesive resin capable of supporting a variety of patterns demanded by end users and machining complicated three-dimensional shapes highly efficiently and highly accurately in place of a conventional photolithography technology. <P>SOLUTION: The micro-machining method applies cryogenic cooling to a flexible and self-adhesive polymeric material to cool it to a glass transition temperature or lower into a glass state and applies ductile mode cutting with a per-blade cut-off amount set in a submicro scale, thereby enabling to form a micro-size groove or a hole extremely accurately by mechanical cutting work, and in particular, a micro flow passage with an extremely highly smooth cutting surface obtained. Furthermore, the micro-machining method can form a specially shaped groove or a hole by elastically deforming the material into an optional shape at room temperature, applying cryogenic cooling to it, and performing cutting work. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a micromachining method for a flexible and self-adhesive polymer material substrate, particularly to a micromachining method suitable for manufacturing a microchannel, and an apparatus therefor.

A microfluidic device is a device called a microfluidic device, a lab-on-chip, a micro-TAS (micro total analysis system), or the like. By using this microfluidic device, the sample solution can be placed in a place equipped with an analytical instrument, etc. Not only can it be analyzed immediately on site without sending it, but it also has the advantage that analysis with a very small sample volume is possible.
Such microfluidic devices are considered to be used in a wide range of fields such as the medical field, the industrial field, the agricultural field, and gene analysis.

The micro flow path formed in the microfluidic device, that is, the material constituting the micro flow path reacts with the components of various samples such as blood and DNA flowing through the flow path, and the components of the sample after the reaction. Without affecting the chemical reaction or analysis. Moreover, the material which can form a microchannel on the one surface and was excellent in adhesiveness and adhesiveness with a board | substrate is preferable.
A typical material having such characteristics is polydimethylsiloxane (PDMS) which is a kind of silicone resin.

PDMS is a flexible and self-adhesive resin, and the microchannel in a PDMS substrate having such characteristics is usually a mold produced by photolithography, and liquid PDMS is poured into it and cured. (See Patent Documents 1 and 2).
FIG. 11 shows a micro-channel forming method using PDMS. After a thin film is formed by spin-coating a photoresist on a silicon substrate, a mask on which a channel pattern is drawn is superimposed and exposed to be cured. Then, the uncured part is dissolved and removed to form a convex pattern on the silicon substrate. Subsequently, liquid PDMS is poured into the mold, cured, and then removed from the mold, and the concave pattern is transferred to the PDMS.
By pressing the PDMS on which the concave pattern is formed in this way against the sensor chip, a fine space is generated on the chip. By feeding the liquid into the space, analysis of a minute amount becomes possible.

However, the microfabrication method using the photolithographic method is suitable for mass production of chips with a simple flow path and a constant flow path pattern. It is not suitable for small-scale production of multivariate species. In addition, since a multi-step process is required, there are problems such as a processing time of several days and a very large environmental load due to the use of a solvent, a developer, an etching solution, and the like.
Further, in the conventional method of transferring a concave mold, it is necessary to make a pulling angle in order to remove it from the mold, and it has been impossible to form a groove with a bottom surface and a wall surface that are perpendicular to each other with high accuracy.
Furthermore, in the microfluidic device, it is necessary to make it three-dimensional in order to add various functions to the chip, and in recent research, a three-dimensional fine structure is formed by stacking chips having a two-dimensional groove. Although it has been proposed to realize a simple groove (see Non-Patent Document 1), the processing by the photolithography method requires a more complicated process, and the processing time is significantly increased.

On the other hand, when plastic products are produced in small quantities and in a wide variety, a method often used is cutting.
When the micro-channel is formed by this cutting method, there is a problem in processing accuracy, particularly in terms of the smoothness of the surface of the channel. In Patent Document 3, the bottom blade flat, that is, the radial angle This problem is solved by using an end mill having a bottom blade of 0 ° C., and a micro flow path can be formed on a plastic substrate such as an acrylic resin.
However, mechanical processing methods such as cutting can be applied when a hard resin substrate such as an acrylic resin is used. As described above, including PDMS, which is preferable as a material for a microchannel, Fine processing by a mechanical processing method such as cutting is difficult for a flexible and self-adhesive resin material.

Conventionally, it has been known that a soft material is freeze-cured and subjected to freeze-cured mechanical processing such as polishing, drilling, and cutting (Patent Documents 4, 5, etc.). , Using a soft material such as sponge rubber, foamed urethane, etc., and there is no example applied to a resin material having self-adhesiveness, and high accuracy that satisfies the high smoothness required for the microchannel It was not intended for micro-size machining.
JP 2004-296099 A JP 2007-315936 A JP 2007-283437 A JP-A-9-57694 Japanese Patent Publication No. 2001-208042 Yi-Chung, Katsuo Kuribayashi, A Single-Layer PDMS-on-Silicon Hybrid Microactuator with Multi-Axis Out-of-plane Motion Capabilities-Patr 2: Fabrication and Characterization, Journal of Microelectromechanical Systems, Vol. 14, No. 3 (2005), pp.558-566

In this way, microfabrication using photolithographic techniques is used for micro-size processing such as the formation of microchannels on flexible and self-adhesive polymer substrates such as PDMS. However, there is a problem of high cost in the production of varieties and variable quantities, and in the microfluidic device, it is required to add various functions to the chip, and the three-dimensional microchannel formed is made Is currently required.
The present invention has been made in view of the above circumstances, and is required by end users in place of conventional photolithography technology in a micro-size processing method using a flexible and self-adhesive resin. It is an object of the present invention to provide a new micromachining method that can deal with various patterns and that can process a complicated three-dimensional shape with high efficiency and high accuracy.

  As a result of studying to solve the above problems, the present inventor applied cryogenic cooling to a flexible and self-adhesive polymer material to cool it to a glass transition temperature or lower, and in a glass state, per blade By applying ductile mode cutting with a cut-off amount of sub-micro scale, micro-sized grooves and holes can be formed with high accuracy by mechanical cutting, and the obtained cutting surface has extremely high smoothness. I found out. As a result of further studies, it has been found that grooves and holes having special shapes can be formed by elastically deforming into an arbitrary shape at room temperature and then cooling it to a cryogenic temperature for cutting.

The present invention has been completed based on these findings, and provides the following inventions.
(1) After a flexible and self-adhesive polymer material substrate is cured by cooling to a temperature lower than the glass transition temperature of the polymer material, micro-sized grooves and / or holes are obtained by mechanical cutting. A micro-machining method characterized by forming.
(2) The micromachining method according to (1), wherein the substrate is cooled in liquid nitrogen.
(3) The micromachining method according to (1) 1 or (2), wherein the shape of the concave path has a three-dimensional shape.
(4) The micro-machining method according to (1) or (2), wherein the substrate is cooled in advance after being deformed into a predetermined shape to form a specially shaped groove and / or hole.
(5) The micromachining method according to claim 4, wherein the deformation is curved.
(6) The micromachining method according to (4), wherein the deformation is a twist along a center line, and the hole is formed by being shifted from the center line in a twisted state.
(7) The micromachining method according to any one of (1) to (6), wherein the flexible and self-adhesive polymer material is polydimethylsiloxane.
(8) The micromachining method according to any one of (1) to (7), wherein the micromachining method is a microchannel manufacturing method.
(9) An apparatus for forming micro-sized grooves and / or holes in a flexible and self-adhesive polymer material substrate by mechanical cutting, at least a chamber for storing liquid nitrogen; A substrate holder installed in the chamber; means for flowing liquid nitrogen in a flow path provided in the substrate holder; a clamp for fixing the substrate provided on an upper surface of the substrate holder; and an upward direction of the substrate And a small-diameter end mill capable of moving in three axial directions.

  According to the present invention, a micro-sized groove and / or hole having a high shape accuracy or a micro-sized groove and / or hole having a more complicated three-dimensional shape is formed on a flexible and self-adhesive polymer material substrate in a short time. In addition, it is possible to form a groove whose bottom surface and wall surface are perpendicular to each other, which cannot be formed by the conventional transfer method. Further, it is possible to easily form a minute bent hole or a specially shaped fine groove, which could not be formed by the conventional method, in a short time.

According to the method of the present invention, a flexible and self-adhesive polymer material substrate is cooled to an extremely low temperature not higher than the glass transition temperature, and then the substrate is subjected to mechanical cutting to form a micro-sized microchannel or the like. A micromachining method characterized by forming grooves and / or holes.
In the present invention, micro-size processing means forming a groove and / or a hole having a width of 1 mm or less and a depth of 1 mm or less, and preferably a groove having a width of 100 μm or less and a depth of 100 μm or less. Further, the shape such as the length, presence or absence of bending, branching or the like is not limited, and the shape of the groove is not particularly limited to a rectangle.
Further, the cutting in the present invention is not particularly limited as long as such micro-sized grooves and / or holes are cut by mechanical processing, and if it is mechanical cutting, There are also no particular restrictions on the type of device, the details of the apparatus, the shape, material, and surface condition of the cutting jig.

Examples of the flexible and self-adhesive polymer material used in the present invention include polydimethylsiloxane (PDMS), silicone rubber, silicone gel, and the like.
Hereinafter, the present invention will be described in more detail using PDMS, which is a typical substrate material of a microfluidic device.

PDMS is a polymer material having a Si—O bond as the main chain, but since the atomic radius of Si is larger than the atomic radius of C, this Si—O bond is easy for molecular motion, and at room temperature, rubber Is in a state.
A polymer material such as PDMS has a glass transition point, and when the temperature becomes lower than the glass transition point, molecular motion is suppressed and the rubber state transitions to the glass state.
In the method of the present invention, a flexible and self-adhesive polymer material such as PDMS is maintained at a temperature sufficiently lower than its glass transition temperature (PDMS Tg: −123 ° C.). By performing ductile mode cutting with a cut-out amount of sub-micro scale, processing with extremely high accuracy is possible.

Specifically, when held in liquid nitrogen at −196 ° C. or lower, PDMS changes from a rubber state to a glass state, and a PDMS having a hardness that enables high precision and fine processing can be obtained. is there.
FIG. 1 shows the result of measuring the change in hardness of PDMS when cooled with liquid nitrogen using a durometer, and as is clear from the figure, at a very low temperature below the glass transition temperature. The hardness of PDMS is extremely higher than that of PDMS at room temperature, and it has been found that a hardness close to that of PMMA (polymethyl methacrylate) known as a hard resin can be obtained.

When the microchannel is formed by the method of the present invention, the processing accuracy of the formed channel surface is particularly important, and the surface roughness is required to be 0.1 μm or less in terms of Ra. If the surface roughness Ra is more than this, optical detection in the microchannel becomes difficult, and the performance as a biochip or microanalysis chip is deteriorated.
In the present invention, it is preferable to use a small-diameter end mill such as a micro square end mill for micro machining with a smooth machining surface and high vertical accuracy between the groove bottom surface and the wall surface.
In the method of the present invention, when a cryogenic cooled PDMS having a glass transition temperature or lower is cut using a small diameter end mill, the processing conditions are such that ductile mode cutting with a cutting amount per blade being sub-microscale can be realized. It is desirable. As specific processing conditions, the tool diameter is φ1.0 mm or less, and the smoother the surface is obtained as the feed rate is slower, preferably 2000 mm / min or less, more preferably 200 mm / min or less, and 10 mm / min. Then, it was found that a smoothness of Ra = 50 nm was obtained.
Further, the higher the rotation speed, the higher the smoothness is obtained. However, it is preferably 5000 rpm or more, more preferably 50000 rpm or more, and it was found that the smoothness of Ra = 50 nm can be obtained at the rotation speed of 20000 rpm.

Hereinafter, the apparatus used for the micromachining method of the present invention will be described.
FIG. 2 is a diagram schematically showing an example of the apparatus of the present invention.
A substrate holder is installed in a chamber containing liquid nitrogen.
The chamber has an aluminum inner wall having high thermal conductivity and a heat insulating wall provided on the outer periphery thereof. The heat insulating wall blocks heat and prevents liquid nitrogen from becoming gaseous.
The substrate holder is made of aluminum having high thermal conductivity like the inner wall of the chamber, and has a clamp for fixing the substrate placed on the upper surface in a predetermined position. A flow path for flowing liquid nitrogen is provided.
In order to be able to process the substrate in liquid nitrogen, a small-diameter endomi is installed above the substrate so as to be movable in three axial directions.

According to the method of the present invention, it is possible to perform special-shaped groove / hole processing on the substrate by utilizing the property of the substrate at low temperature and low elasticity and being machineable at extremely low temperatures. .
3 and 4 are diagrams schematically showing an example thereof.
In the method shown in FIG. 3, a flexible and self-adhesive substrate is curved into an arbitrary shape at room temperature, cooled at a cryogenic temperature, and subjected to simple groove processing in the curved state (step (a)). By returning this to room temperature, a specially shaped groove can be formed (step (b)).
Also, the method shown in FIG. 4 is to twist a flexible and self-adhesive substrate along the center line at room temperature (step (a)), cool it at a low temperature, and shift it from the center line in a twisted state. A hole with a bent shape can be formed by performing hole processing (step (b)) and then returning it to the original shape at room temperature (step (c)).

As described above, according to the method of the present invention, a flexible polymer material is elastically deformed into an arbitrary shape at room temperature, and this is cooled at a cryogenic temperature to perform normal hole processing and groove processing, and then this is performed at room temperature. By returning to the original shape, it is possible not only to process with conventional lithography and molds, but also with specially shaped fine holes and grooves, which were impossible with normal machining, such as bent holes. Special holes and trapezoidal or elliptical special grooves can be easily machined.
Further, the processing shape can be arbitrarily controlled by adjusting the elastic deformation amount (twist amount or bending amount).
In particular, in the nanofluidic chip, it becomes possible to develop a nanofluidic chip having a three-dimensionally shaped nanochannel by processing using tension, or to manufacture a joint of a microfluidic chip by bending hole processing.
Furthermore, this special shape processing method can be applied to a flexible polymer material having no self-adhesiveness.

Hereinafter, although the example which formed the microchannel on the PDMS board | substrate using the apparatus shown in FIG. 2 is described, this invention is not limited by these Examples.
Example 1
PDMS monomer (Shin-Etsu Silicone Co., Ltd., product number KE-1606) and curing agent (Shin-Etsu Silicone Co., Ltd., product number CAT-RG) are mixed, air bubbles are removed, and the mixture is poured into a mold at room temperature. -It was allowed to stand for 24 hours under reduced pressure to be cured.
The cured PDMS was peeled off from the mold, placed on the work holder shown in FIG. 2, and finely processed using a two-blade microsquare end mill (φ0.5 mm, manufactured by Nisshin Tool Co., Ltd.). The rotational flare accuracy of the tool was 3 μm or less, and the cutting conditions were a rotational speed of 5000 rpm and a processing speed of 10.0 mm / min.
For comparison, fine processing was performed in the same manner as in Example 1 except that liquid nitrogen was not used.

FIG. 5 is a photograph of the shape of the cutting groove observed with an electron microscope (SEM).
In the figure, (a) on the left side shows the cutting results at room temperature, (b) on the right side shows the cutting results at cryogenic temperature, the upper row is a photograph of the upper surface, and the lower row is a photograph of the side surface. It is a photograph.
As shown in (a), it was not possible to process at room temperature at all, but as shown in (b), fine grooves could be formed under extremely low temperature in liquid nitrogen. The formed groove had a width of 516 μm and a depth of about 200 μm. The theoretical processing width considering heat shrinkage was 514 μm, and the processing accuracy was found to be ± 1%.
Next, when the feed rate was changed and the relationship with the generation of the cutting mark was examined, the lower the speed, the more the cutting mark did not appear, and a smooth surface was obtained. The surface roughness Ra reached 80 nm.
It has also been found that the surface roughness of the cutting surface can be further improved by increasing the rotational speed or decreasing the groove depth.

(Example 2)
In the same manner as in Example 1, a complicated three-dimensional flow path was formed. The time required for processing was 60 minutes. FIG. 6 is a photograph of the formed shape taken from above, and the right photograph is an enlarged view of a part of the left photograph.
It has been revealed that a complicated three-dimensional flow path that requires several days in conventional photolithography can be performed in tens of minutes to several hours with the method according to the present invention.

(Example 3)
In the present embodiment, the PDMS cured in the same manner as in the first embodiment is curved or stretched at room temperature, and the curved or stretched PDMS is placed on the work holder so that its shape is maintained, and a simple groove is formed. Was processed. Then, by returning this to room temperature, a specially shaped groove or a flow path finer than the actual tool diameter could be formed.
FIG. 7 is an electron micrograph of the cross-sectional shape of the groove obtained by bending the PDMS substrate, and it can be seen that a tapered groove having a bottom arc is formed.

Example 4
In this example, similarly to Example 3, the PDMS was curved along the center line, and the triangular groove was formed by shifting the groove from the center line using a square end mill.
FIG. 8 is an electron micrograph of a cross-sectional shape of the obtained special-shaped groove, and it can be seen that asymmetric triangular grooves are formed.

(Example 5)
In this example, a commercially available silicone rubber sheet having a size of 100 mm × 100 mm and a thickness of 1 mm (Irimagawa Rubber Co., Ltd. IS-825 hardness (A type): 50, heat resistance: 200 ° C.) was used.
Example: Using a two-blade microsquare end mill (φ0.5 mm, manufactured by Nisshin Tool Co., Ltd.) after removing the release sheets on the front and back surfaces of a commercially available silicone rubber sheet and placing them on the work holder shown in FIG. Under the same conditions as in No. 1, fine processing (very low temperature) using liquid nitrogen and fine processing (normal temperature) not using liquid nitrogen were performed.
FIG. 9 is a photograph of the shape of the cutting groove observed with an electron microscope (SEM).
In the figure, (a) on the left side shows the cutting results at room temperature, (b) on the right side shows the cutting results at cryogenic temperature, the upper row is a photograph of the upper surface, and the lower row is a photograph of the side surface. It is a photograph.

(Example 6)
In this example, a commercially available silicone gel sheet having a size of 100 mm × 100 mm and a thickness of 1 mm (GELS penetration by MISUMI Corporation: 55) was used.
The surface of a commercially available silicone gel sheet is coated with an anti-sticking powder, and the back surface is provided with a release paper because it has a pressure-sensitive adhesive layer. Compared to the cured PDMS used, it is very soft and sticky, so it was placed on the work holder shown in Fig. 2 without removing the release paper, and a two-blade microsquare end mill (φ0.5mm, Nisshin) Using a tool company), fine processing using liquid nitrogen (very low temperature) and fine processing without using liquid nitrogen (room temperature) were performed under the same conditions as in Example 1.
FIG. 10 is a photograph of the shape of the cutting groove observed with an electron microscope (SEM).
In the figure, (a) on the left side shows the cutting results at room temperature, (b) on the right side shows the cutting results at cryogenic temperature, the upper row is a photograph of the upper surface, and the lower row is a photograph of the side surface. It is a photograph.

  According to the present invention, it is possible to easily form in a short time a micro hole or micro groove having a special shape that could not be formed by a conventional method, and thus has a flexible and self-adhesive property typified by PDMS. In addition to forming a micro flow path having a complicated three-dimensional shape using a resin material substrate, it can be applied to various fine processing fields. Specifically, special holes such as bent holes, specially shaped grooves such as trapezoids and ellipses, and fine grooves below the tool diameter can be easily machined, and the amount of elastic deformation such as torsion, bending, and tension. It is possible to control the processing shape by adjusting. In particular, in a nanofluidic chip, it becomes possible to realize a microfluidic chip joint or the like by developing a nanofluidic chip having a three-dimensionally shaped nanochannel by processing using a tensile force or by bending a hole. In the case of silicone gel, since it is very flexible and high in self-adhesiveness compared with PDMS, it could not be processed by general machining so far, but according to the present invention, machining by machining is not possible. It becomes possible, and it is expected that the use in the bio field and the medical field will expand more and more. Furthermore, the method of the present invention can also be applied to elastic materials that are not self-adhesive.

The figure which shows the result of having measured the hardness of PDMS under normal temperature and very low temperature The schematic diagram which shows the outline | summary of an example of the apparatus of this invention Schematic diagram showing an example of the special shape grooving process Schematic diagram showing an example of a curved hole machining process Electron micrograph showing the processing results of PDMS at room temperature and cryogenic temperature Photograph of complex three-dimensional flow path formed in Example 2 Electron micrograph showing the shape of the groove formed in Example 3 Electron micrograph showing the shape of the groove formed in Example 4 Electron micrograph showing the processing results of silicone rubber sheet at room and cryogenic temperatures Electron micrograph showing the processing results of silicone gel sheet at normal and cryogenic temperatures Schematic diagram showing a conventional micro-channel formation method using lithography

Claims (9)

  After a flexible and self-adhesive polymer material substrate is cured by cooling to a temperature below the glass transition temperature of the polymer material, micro-sized grooves and / or holes are formed by mechanical cutting. A micromachining method characterized by the above.   The micromachining method according to claim 1, wherein the substrate is cooled in liquid nitrogen.   The micromachining method according to claim 1, wherein the shape of the concave path has a three-dimensional shape.   3. The micromachining method according to claim 1, wherein the substrate is cooled in a predetermined shape and then cooled to form a specially shaped groove and / or hole.   The micromachining method according to claim 4, wherein the deformation is a curve.   5. The micromachining method according to claim 4, wherein the deformation is twisting along a center line, and the hole is formed by being shifted from the center line in a twisted state.   The microfabrication method according to any one of claims 1 to 6, wherein the flexible and self-adhesive polymer material is polydimethylsiloxane.   The micromachining method according to claim 1, wherein the micromachining method is a microchannel manufacturing method.   An apparatus for forming micro-sized grooves and / or holes in a flexible and self-adhesive polymer material substrate by mechanical cutting, comprising at least a chamber for storing liquid nitrogen, An installed substrate holder, means for flowing liquid nitrogen in a flow path provided in the substrate holder, a clamp for fixing the substrate provided on the upper surface of the substrate holder, and an upward direction of the substrate. And a small-diameter end mill movable in three axial directions.