JP2010085337A - Method of forming fine channel using nano wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a fine channel such as micro and nano channels with simplicity and excellent mass-productivity. <P>SOLUTION: A fine channel such as micro and nano channels is formed by growing vertically a nano wire using plasma CVD or thermal CVD and metal nano fine particles arranged in a pattern on a substrate as growth nuclei after vapor-depositing the metal nano fine particles in a pattern for the growth nuclei of the nano wire on the substrate. A fine channel is formed by growing vertically a water-repellent nano wire at a catalyst pattern site formed on a hydrophilic substrate. The portion where the water-repellent nano wire has been grown comes to a side wall of the fine channel (groove portion) and the portion where the hydrophilic substrate has been exposed comes to a bottom portion of the fine channel (groove portion). Alternatively, a fine channel is formed by growing vertically a hydrophilic nano wire at a site of a catalyst pattern formed on a water-repellent substrate, and the portion where a hydrophilic nano wire has been grown comes to a channel space (groove itself) of the fine channel. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for producing a microchannel such as a microchannel or a nanochannel used in microchemical analysis, a microreactor, or the like, using a nanowire such as a carbon nanotube.

  A microdevice is expected as a device that can separate a substance (for example, a biomolecule such as a protein) having a very fine size of several nanometers to several tens of nanometers (see, for example, Patent Document 1). This micro device has a micro flow channel inside, and has a merit of reducing the amount of reagents and waste liquid, cost associated therewith, shortening reaction time, and improving temperature responsiveness by performing a chemical reaction inside. Such a micro device is a complicated three-dimensional structure, and a microchannel having a nano-order level microstructure and a method for manufacturing the nanochannel have been studied and developed.

  In producing such microchannels and nanochannels, conventionally, an apparatus such as a LIGA process using radiant light is used. The LIGA process is a manufacturing method that combines X-ray lithography, electroforming, and molding to create a shape with a large aspect ratio (ratio of depth (height) to processing width). By transferring the pattern through an X-ray mask using X-rays generated from a synchrotron radiation (SR) optical device having excellent straightness as the material, the depth (height) is several hundred μm or more. It is possible to manufacture a complicated three-dimensional structure having an arbitrary shape in the lateral direction. However, devices such as the LIGA process require large devices such as synchrotron radiation (SR) optical devices. The equipment is large and expensive, and the running cost is high.

  In addition, lithography technology that performs drawing using light or an electron beam is known as a two-dimensional processing technology for manufacturing semiconductors and the like, and patterns are refined from several tens of nanometers to several nanometers. It is possible. However, the processing speed and resolution are insufficient to process complex three-dimensional structures such as microchannels and nanochannels.

  Also, silicon, glass, etc. are usually used as the material for the microchannel and nanochannel, and anisotropic dry etching, wet etching using hydrofluoric acid, etc. are used as the pattern forming method. Yes. On the other hand, resin materials such as acrylic have been studied as materials for microchannels and nanochannels in consideration of cost and mass productivity, and as a pattern formation method using resin materials, soft lithography, optical A nanoimprint method, a hot embossing method, and the like are known (see, for example, Patent Document 2).

  Each of the above-described techniques forms a groove-like channel on a substrate or a thin film layer formed on the substrate when forming a microchannel pattern such as a microchannel or a nanochannel. is there.

JP 2001-4628 A JP 2005-42073 A

As described above, conventionally, as a method of manufacturing a micro flow channel or nano flow channel with high processing accuracy, a large-scale device such as a LIGA process using synchrotron radiation is required, and the device introduction cost and the running cost are high. There was a problem with mass productivity.
An object of this invention is to provide the manufacturing method of microchannels, such as a microchannel / nanochannel, which was simple and excellent in mass productivity.

  The present inventors have been conducting research on nanowires such as carbon nanotubes for many years. In forming microchannels such as microchannels / nanochannels, the nanowires can be formed without digging grooves as in the prior art. The idea has been to apply the formation of the flow channel by application, and the manufacturing method of the fine flow channel using the nanowire of the present invention has been completed.

  The method for producing a microchannel according to the present invention uses chemical vapor deposition (CVD), in particular, plasma CVD or thermal CVD after pattern deposition of metal nanoparticles as a growth core of nanowires on a substrate. Then, the nanowires are vertically grown using the metal nanoparticles arranged in a pattern on the substrate as a growth nucleus, and a microchannel and a microchannel such as a nanochannel are manufactured. According to this manufacturing method, a large number of microchannels and nanochannels can be manufactured easily and at a time.

According to a first aspect of the present invention, there is provided a method for producing a fine flow path comprising a step of forming a predetermined catalyst pattern on a hydrophilic substrate and a step of substantially vertically growing water-repellent nanowires on the hydrophilic substrate. Is provided.
In the present invention, the hydrophilic substrate is one having a hydrophilic group such as a hydroxyl group on the substrate surface, and specific examples thereof include a glass plate and a quartz glass plate. In the present invention, the glass plate may be coated with silicon oxide or the like. Further, the size of the substrate to be used may be appropriately selected depending on the analytical instrument, the analysis target, and the like.

  In addition, the formation of a predetermined catalyst pattern refers to pattern deposition of metal nano-particles serving as nanowire growth nuclei on a substrate. Here, the growth nuclei are ultrafine metal particles such as Ni (nickel), Co (cobalt), Fe (iron), etc., and ultrafine particles having a particle diameter of several nm to several tens of nm are particularly preferable. When using ultrafine metal particles as growth nuclei, it is created by attaching ultrafine particles created by gas evaporation method to the substrate surface, by depositing ultrathin metal film and annealing at 300-1000 ° C in a reducing atmosphere Is possible.

  In addition, the nanowire in the present invention refers to a linear structure having a thickness of several nanometers to several tens of nanometers and an aspect ratio (length ratio to thickness) of 10 or more.

  In the first aspect of the present invention, a nanochannel having water repellency is grown substantially vertically at a catalyst pattern position formed on a hydrophilic substrate to produce a fine channel. The portion where the water-repellent nanowire is grown is used as the side wall (of the groove portion) of the fine channel, and the portion where the hydrophilic substrate is exposed is used as the bottom portion (of the groove portion) of the fine channel.

The first aspect of the present invention preferably further includes a step of heating the water-repellent nanowire and a step of placing a thermosoftening resin material on the water-repellent nanowire.
Here, the thermosoftening resin material is, for example, an acrylic plate formed of an acrylic resin. After water-repellent nanowires are grown substantially vertically and then heated, a heat-softening resin material is placed on top of the water-repellent nanowires, heat is transferred to the heat-softening resin material and softens, and the heat-softening resin material adheres to the water-repellent nanowire It is possible to enclose a liquid such as water.

  Here, the water-repellent nanowire is preferably a carbon nanotube. The carbon nanotube is a water-repellent nanowire having super water repellency and chemical stability. In the case of the carbon nanotube, the carbon nanotube can be grown vertically to the catalyst pattern position. Carbon nanotubes are widely studied nanomaterials, and unlike metallic nanowires, carbon nanotubes exhibit good conductivity, even on a nanoscale, with high conductivity efficiency, stronger and lighter than iron. .

The catalyst metal that serves as the growth nucleus of the carbon nanotube is a metal material that functions as a catalyst in the production of graphite, such as transition metal materials such as Ni (nickel), Co (cobalt), and Fe (iron). Including alloy materials.
The type of the carbon nanotube in the present invention is not limited and may be a single-walled carbon nanotube, a multi-walled carbon nanotube, or a mixture thereof.
Further, the carbon nanotube in the present invention may be either oriented or non-oriented. In addition, the orientation tends to keep air and may improve water repellency. On the other hand, when the non-oriented material is patterned, the aspect ratio is smaller than that of the oriented material, and overflow may occur when a fluid is flowed as the flow path.

  Next, from the second aspect of the present invention, unlike the first aspect of the present invention, a step of forming a predetermined catalyst pattern on the water-repellent substrate, and hydrophilic nanowires are grown substantially vertically on the water-repellent substrate. And a method of manufacturing a fine flow path comprising:

In the present invention, the water-repellent substrate includes not only a substrate itself having water repellency but also a substrate subjected to a water-repellent treatment and a substrate on which a water-repellent film is laminated (coated). In addition to graphite and water repellent glass, a resin, plastic, ceramic, or metal substrate having water repellency may be used.
In the present invention, the hydrophilic nanowire refers to, for example, a silicon nanowire or a fluorinated hydrophobic nanowire.

  In the second aspect of the present invention, a nanochannel having hydrophilicity is grown substantially vertically at a catalyst pattern position formed on a water-repellent substrate to produce a fine channel. As in the first aspect of the present invention, the portion where the hydrophilic nanowires are grown is the side wall (of the groove portion) of the fine channel, and the portion where the water-repellent substrate is exposed is the bottom portion (of the groove portion) of the fine channel. Instead, in the second aspect of the present invention, the portion where the hydrophilic nanowires are grown is used as a channel space (groove portion itself) in the fine channel.

Next, in the method for manufacturing a fine flow path according to the first aspect or the second aspect of the present invention, the step of forming a predetermined catalyst pattern on the substrate is performed by using a patterned metal mask to grow nanowire growth nuclei. The metal nano-particles to be obtained are pattern-deposited on the substrate.
By forming a catalyst pattern by such a method, a fine channel having a nano-order line width can be easily and accurately constructed.

  In addition, the step of forming a predetermined catalyst pattern on the substrate is performed by patterning and applying metal nano-particles that serve as the growth nuclei of the nanowires to any position on the substrate surface by sputtering, ion beam lithography, or lithography. It doesn't matter. For example, in the case of a photolithography method, a substrate coated with a photoresist thin film is exposed with light through a mask, and a pattern corresponding to the mask shape is formed on the substrate. As light, ultraviolet light (UV) is usually used. As an exposure method through a mask, an electron beam drawing method using an electron beam, an exposure method using X-rays, or the like can be employed.

  In the photolithography method, a photomask pattern is transferred to a substrate by irradiating light such as ultraviolet rays. In electron beam drawing, a pattern is drawn by irradiating an electron beam. According to the electron beam drawing method, a finer pattern can be drawn as compared with a method using photolithography.

  According to the method for producing a microchannel of the present invention, instead of digging a microchannel groove, a nanowire such as a carbon nanotube is vertically grown to form a groove, and a water-repellent nanowire and a hydrophilic substrate, or By combining a hydrophilic nanowire and a water-repellent substrate and making the nanowire part into a water-repellent region or channel, a microchannel / nanochannel, such as a microchannel / nanochannel, excellent in mass productivity can be manufactured. It has such an effect.

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

In Example 1, a method of manufacturing a fine channel using carbon nanotubes will be described. The method for producing a fine channel of Example 1 is a method for producing a fine channel by vertically growing carbon nanotubes having water repellency at catalyst pattern positions formed on a hydrophilic silicon oxide substrate. .
FIG. 1 (1) shows an image diagram of the fine flow path of Example 1. FIG. As shown in FIG. 1 (2), carbon nanotubes having water repellency are vertically grown at catalyst pattern positions (3a, 3b) formed on a silicon oxide substrate 10 having hydrophilicity, thereby aligning carbon nanotube groups. (1a, 1b) is used as a bank to form a fine channel.
FIG. 1 (2) shows that the water (or liquid) 2 is poured into the channel portion of the manufactured microchannel, that is, the portion sandwiched by the banks formed by the oriented carbon nanotube groups (1a, 1b). It shows the state. Since the silicon oxide substrate 10 has hydrophilicity and the oriented carbon nanotube groups (1a, 1b) have water repellency, the water (or liquid) 2 flows smoothly through the flow path portion by capillary action. .

Next, the manufacturing method of the fine channel of Example 1 will be described by dividing into the following two steps (a) and (b) with reference to FIG.
(A) Step of forming a predetermined catalyst pattern on a hydrophilic substrate First, a hydrophilic silicon oxide substrate is prepared as a substrate for aligning carbon nanotubes. For example, Si (100) is used for the silicon oxide substrate. This is because the surface is flat, and it is also a vacuum material and is widely used as a substrate. As a pretreatment of the silicon oxide substrate, first, Si is cut into a square shape of about 8 mm, and then the cut substrate is subjected to ultrasonic cleaning for 5 minutes each in the order of ethanol and pure water. Thereafter, oxidation is performed for preparing the SiO ₂ film. The oxidation conditions are a heating temperature of 800 ° C. and a heating time of 120 minutes in a 100% oxygen atmosphere.

  Thereafter, metal fine particle patterns (3a to 2d) serving as a catalyst are formed on the silicon oxide substrate 10 using metal masks (2a to 2c) ((1) and (2) in FIG. 2). See). The catalytic metal fine particles of iron are formed by agglomerating the catalytic metal fine particles by an annealing process after depositing the catalytic metal fine particles having a thickness of, for example, 3 nm by a vacuum deposition method. Note that the density of the catalytic metal fine particles formed on the silicon oxide substrate can be controlled by annealing conditions (temperature, processing time).

  The annealing conditions for aggregating the iron catalytic metal fine particles are, for example, using hydrogen as a reaction gas, a hydrogen flow rate of 50 sccm, a pressure of 20 Pa, a substrate temperature of 700 ° C., and a reaction time of 30 minutes.

(B) Step of vertically growing water-repellent nanowires on a hydrophilic substrate Next, carbon nanotubes (1a to 1d) are grown on a silicon oxide substrate 10 on which iron catalyst metal fine particle patterns (3a to 2d) are formed. Let The carbon nanotube is obtained by a thermal CVD method, for example, using a mixed gas of acetylene and hydrogen as a reaction gas, an acetylene flow rate of 50 sccm, a hydrogen flow rate of 100 sccm, a pressure of 1.0 × 10 ³ Pa, and a substrate temperature of 700 ° C. The growth time is 30 minutes.

In the step (a), for example, JEE-400 manufactured by JEOL can be used as the vacuum vapor deposition apparatus, and iron catalytic metal fine particles are vacuum vapor deposited on a silicon oxide substrate. Further, in order to control the position of the generated carbon nanotube, patterning is performed using a metal mask. The metal mask uses a stainless steel mask. In addition, in order to investigate the amount of catalyst metal deposition, a quartz crystal microbalance (Quartz)
The film pressure is measured by Crystal Microbalance (QCM).

  Here, the vacuum vapor deposition method is a method of manufacturing a thin film by evaporating a metal, an alloy or the like in a vacuum vessel and condensing it on the surface of a substrate previously placed in the vessel. Compared with other thin film fabrication methods, chemical precipitation methods, gas phase reaction methods, and sputtering methods, the vacuum deposition method does not matter whether the film and the substrate are non-metallic, the temperature of the substrate does not increase, and the evaporation molecules go straight The thin film distribution is advantageous because it is mainly determined by the geometrical arrangement of the evaporation source and the substrate, while it is possible to produce a uniform film on a surface with a small curvature or a complex shape. The point that the residual gas pressure needs to be a vacuum of about 10-4 Torr or less, the point that the substrate material needs to be evaporated or the gas needs to be released so that it does not harm the adhesion of the film, and simple There is a demerit in that alloys and compounds that can produce a film with a simple apparatus and operation are limited.

Further, FIG. 3 shows an apparatus configuration diagram of thermal CVD used for using the thermal CVD method. A muffle furnace is used as a heating device. C ₂ H ₂ , H ₂ , and Ar are used as the introduction gas, and all the gases can be controlled with a flow meter. Here, the thermal CVD method is a technique in which a gas or liquid raw material is vaporized at a high temperature and a thin film is formed by a chemical reaction in the vapor phase of the vapor or on the surface of the substrate. Excited by When a volatile compound composed of elements including the film material to be produced is vaporized and supplied as uniformly as possible on a substrate heated to a high temperature using a carrier gas such as hydrogen, argon or nitrogen, it is decomposed and reduced on the substrate. A chemical reaction such as substitution occurs and a thin film can be formed. The thermal CVD method is known as a highly convenient manufacturing method as it has a relatively simple apparatus and is excellent in mass productivity.

The detailed procedure of the thermal CVD method is as follows.
(1) A silicon oxide substrate sample on which a metal catalyst is deposited is introduced into a quartz tube. After sample introduction, the pressure in the chamber is reduced to about 2 Pa by a rotary pump.
(2) The temperature of the muffle furnace is set to 700 ° C., and the substrate surface is annealed for a predetermined time in an H 2 atmosphere.
(3) A mixed gas (C ₂ H ₂ , H ₂ , Ar) is introduced by adjusting a valve so as to have a predetermined mixing ratio and pressure, thereby generating carbon nanotubes.
(4) After the reaction, the introduction of the mixed gas is stopped, the pressure in the reaction furnace is lowered to about 2 Pa, and natural cooling is performed.
(5) A sample is taken out, and then the morphology of the sample is observed by SEM.

Next, an encapsulating apparatus using a transparent substrate such as a glass substrate as a lid is prepared for the fine channel manufactured by the above-described manufacturing method.
FIG. 4 shows a state in which water is injected into the flow path using a syringe with respect to the produced fine flow path. In the syringe injection method, since the pressure, speed, volume, and the like of water to be introduced are not constant, performance cannot be evaluated by quantitative measurement and comparison, but the functionality for introducing water as a fine channel can be confirmed.
As shown in FIG. 4, in the state where the produced microchannel 5 is attached to a sealing device having a transparent substrate such as a glass substrate as a lid, the syringe needle 43 is formed on the silicon oxide substrate 10. Water is introduced from the end of the path 5. In FIG. 4, a meandering circuit figure that performs continuous refraction as a fine flow path is taken as an example.

FIG. 5 shows a procedure for covering the produced fine channel with an acrylic plate. A carbon nanotube (1a, 1b) grown on a silicon oxide substrate 10 on which a pattern of iron catalytic metal fine particles is formed is shown in FIG. 5 (1). The parts are different for each carbon nanotube. Therefore, there is a case where a liquid such as water in the flow path cannot be sealed with a glass substrate pressed.
Therefore, the carbon nanotubes forming the fine flow path are heated, and an acrylic plate that is a thermosoftening resin material is used as the lid.
First, after the carbon nanotubes (1a, 1b) are vertically grown, the silicon oxide substrate 10 is heated to heat the carbon nanotubes (1a, 1b). When the acrylic plate 45, which is a thermosoftening resin material, is placed on the carbon nanotubes (1a, 1b), heat is transmitted to the acrylic plate 45 and the surface portion is softened. As shown in FIG. 5 (2), the acrylic plate 45 can be brought into close contact with the carbon nanotubes (1a, 1b) by softening the surface portion of the acrylic plate 45, and a liquid such as water can be enclosed.

FIG. 6 shows the shape of the metal mask used in Example 1. The metal mask shown in FIG. 6 has a 1 mm wide straight line figure, a branch-like branch figure, a Y-shaped figure for merging, a meandering circuit figure for continuous refraction, and a Fermat spiral figure transmission hole in a few mm square. A pattern is formed (see FIGS. 6 (1) to (5)).
Here, it is known that the flow path of the branch-like branch figure can separate water oil efficiently by processing one bottom surface of the branch destination to be hydrophilic and the other bottom surface to be hydrophobic. It is possible to construct a two-phase oil-water combined / phase-separated flow path by combining with a Y-shaped flow path for performing the above.

  In addition, since the flow path of the meandering circuit figure that performs continuous refraction has a large surface area per unit volume that can affect the fluid, heat the carbon nanotube as an electrode or introduce a heater or the like into the uneven structure. For example, the fluid can be effectively heated and cooled in a very small space.

  FIG. 7 shows the patterning of iron (Fe) metal fine particles as a catalyst on the silicon oxide substrate using the above metal mask, and the growth of carbon nanotubes on the pattern of catalytic metal fine particles on the silicon oxide substrate. The results obtained were observed with an optical microscope (see FIGS. 7 (1) to (5)).

  The manner in which the product obtained by the manufacturing method of the fine flow path of Example 1 described above actually functions as a fine flow path will be described with reference to a fine flow path having a Fermat spiral flow path pattern as an example. Here, the flow pattern of the Fermat spiral has a rotation structure in the clockwise direction, and has a structure in which it is reversed at the center and rotated in the counterclockwise direction. Unlike the flow path of the meandering circuit figure that performs continuous refraction as described above, the curvature of the curve is large and the surface area per unit volume can be increased without imposing a large load on the fluid.

  FIG. 8 shows a state in which water is introduced into a fine channel formed with a Fermat spiral channel pattern using a syringe with a digital microscope for microscope (manufactured by Shimadzu Rika Co., Ltd., Moticam2000).

The photograph observed with the digital microscope of FIG. 8 shows an observation photograph of frame advance every 1/488 seconds. From the observation result of the introduction of water, it can be seen that the fine channel formed with the Fermat spiral channel pattern functions as a channel of water.
With respect to the flow channels of other shapes, the flow of water can be confirmed without any leakage or breakage due to a rapid pressure change of the fluid, as in the case of the fine flow channel having the Fermat spiral flow channel pattern.

The method for producing a microchannel according to the present invention includes a small analyzer (μTAS) for reacting a very small amount of liquid reagent, a micromachine, a microelectromechanical system, a microchip device, a lab-on-a-chip, Useful for biochips, healthcare chips, etc.
It replaces the existing microchannel / nanochannel, is ultra-compact and lightweight, and can be mass-produced. Therefore, industrial applications such as medical, analysis, and measurement such as μTAS (Total Analytical System) are available. Highly expected.

Image of fine channel in Example 1 Schematic diagram of the production procedure of the fine channel of Example 1 Thermal CVD equipment configuration diagram Introducing water with a syringe Schematic diagram of the manufacturing procedure of the lid of the fine channel of Example 1 The shape of the metal mask used in Example 1 A photograph of the result of growing carbon nanotubes on a pattern of catalytic metal particles on a silicon oxide substrate, observed with an optical microscope A photograph of a digital microscope observing the introduction of water into a microchannel with a Fermat spiral channel pattern using a syringe

Explanation of symbols

1, 1a to 1d Carbon nanotube 2 Water (or liquid)
2a to 2c Metal mask 3a to 3d Metal catalyst 10 Silicon oxide substrate 30 Sample 31 Flow meter 32 Quartz tube 33 Muffle furnace 34 Pressure gauge 35 Rotary pump 40 Encapsulating plate 42 Syringe 43 Syringe needle 45 Acrylic plate

Claims (7)

  A method for producing a fine channel, comprising: a step of forming a predetermined catalyst pattern on a hydrophilic substrate; and a step of substantially vertically growing water-repellent nanowires on the hydrophilic substrate.   2. The method of manufacturing a microchannel according to claim 1, wherein a portion where the water-repellent nanowire is grown is used as a side wall of the microchannel, and a portion where the hydrophilic substrate is exposed is used as a bottom portion of the microchannel. .   The method for producing a microchannel according to claim 1, further comprising: heating the water-repellent nanowire; and placing a thermosoftening resin material on the water-repellent nanowire. .   4. The method for producing a fine channel according to claim 1, wherein the water-repellent nanowire is a carbon nanotube.   A method for producing a fine flow path, comprising: a step of forming a predetermined catalyst pattern on a water-repellent substrate; and a step of substantially vertically growing hydrophilic nanowires on the water-repellent substrate.   6. The method for producing a microchannel according to claim 5, wherein a portion where the hydrophilic nanowire is grown is used as a channel space in the microchannel. The step of forming a predetermined catalyst pattern on the substrate is a method of pattern-depositing metal nanoparticles serving as a growth core of nanowires on the substrate using a patterned metal mask. 5. A method for producing a fine flow path according to 5.