JP4766516B2 - Method for hydrophilizing microchannels - Google Patents

Description

  The present invention is used as a fluid transfer means in microchemistry and the like that are being promoted in many fields such as medicine, pharmacy, biology, and engineering, such as microreactors, biosensors, analytical tools, capillary columns, and filtration filters. The present invention relates to a method for hydrophilizing a fine channel.

  In recent years, with progress in microfabrication technology, research on microchemistry such as downsizing and nanotechnology has been conducted in various research fields. For example, in the field of microchemical plants, extraction, separation, concentration, mixing and reaction, Research on integration of unit operations such as heating and one-chip research, research on exhaust gas treatment, removal of fine particles, deodorization, etc. in the field of environmental conservation, development of reformers for fuel cells and oil refining in the field of energy Research is actively promoted. In such a microchemical world, the micro-channel is not just a means of mass transfer between unit operations, but a micro-channel that is indispensable for reacting fluids with high accuracy and at high speed and with high efficiency. In order to control the fluid in the fine channel, the inner wall surface of the channel is subjected to a hydrophilic treatment or a hydrophobic treatment.

  For example, in Japanese Patent Laid-Open No. 2003-272,654, in order to suppress the formation of a puddle in the gas flow path of the fuel cell separator, particularly the U-turn portion, hydrophilicity is formed on the inner wall surface of the gas flow path. There has been proposed a method of hydrophilizing by applying droplets or surfactants containing high carbon particles. However, in this method, since only a surfactant or the like is applied, even if it is temporarily effective, if this surfactant or the like is washed away, the effect does not appear, and a hydrophilic effect is obtained over a long period of time. There is a problem that it is difficult to sustain.

  Japanese Patent Application Laid-Open No. 2004-117,179 is provided with a microfluidic channel for moving a sample solution formed of a polymer material substrate having a recess and a polymer material cover covering the recess of the substrate. In the analysis tool, after the reformed gas comprising fluorine gas and oxygen gas is brought into contact with the inner surface of the concave portion, water or water vapor is brought into contact with the inner surface of the concave portion to hydrophilize the inner surface of the concave portion, and the contact angle of the inner surface of the concave portion with respect to water is set to 0 A hydrophilic treatment method of 80 ° is disclosed. In this hydrophilic treatment, the fluorine gas and oxygen gas and water or water vapor are brought into contact with the inner surface of the concave portion to introduce a carboxyl group, which is a hydrophilic group, into the polymer chain on the inner surface of the concave portion. It cannot be applied to inorganic materials such as glass, metal oxides, and plating films.

  Furthermore, Japanese Patent Laid-Open No. 2001-159,618 discloses a biosensor that includes a cavity for collecting a liquid sample such as blood by capillary action and analyzes a specific component by reaction with a reagent. Formed with a resin material containing an activator, formed with a film whose surface is coated with a surfactant on the sensor side wall, or subjected to plasma discharge treatment, coupling reaction treatment, ozone treatment, UV treatment, etc. on the sensor side wall Thus, a method of hydrophilizing has been proposed. The biosensor proposed here is made of a resin such as polyethylene terephthalate or polycarbonate, and is not described as being applied to a fine channel formed of an inorganic material or the like.

  Furthermore, Japanese Patent Application Laid-Open No. 7-276,629 discloses a high concentration of, for example, several thousand to several tens of thousands ppm in order to make the ink flow path inner wall surface of an ink jet recording head provided with a plastic ink jet container hydrophilic. There has been proposed a method of generating oxygen / ozone gas containing ozone and circulating this high-concentration ozone-containing oxygen / ozone gas through an ink flow path. The proposed hydrophilic treatment method for an ink jet recording head is also applied to a plastic ink flow path, and is not described as being applied to a fine flow path formed of an inorganic material or the like.

  Japanese Patent Application Laid-Open No. 8-108,535 discloses an alkali cleaning using an alkaline cleaning liquid containing a surfactant in order to make the inner wall surface of the ink flow path of the ink jet recording head hydrophilic with an ink contact angle of 10 ° or less. There has been proposed a hydrophilic treatment method for an ink jet recording head which is further subjected to ozone treatment after the treatment. The proposed hydrophilic treatment method for an ink jet recording head is also applied to a plastic ink flow path, as in the case of Japanese Patent Application Laid-Open No. 7-276,629, and a fine flow formed of an inorganic material or the like. There is no mention of application to roads.

  In the case of hydrophilizing the surface to be treated of the fine flow path, in the conventional method of applying a liquid such as a surfactant or a hydrophilic paint, even if the shape of the fine flow path is an open groove shape, In addition, it is difficult to apply the liquid to every corner of the surface to be processed on the inner surface of the fine channel. If the shape of the fine channel is tubular or hole-shaped, it takes time to introduce and dry the liquid. And there is a problem that productivity is poor.

  In addition, in the conventional methods using gases such as fluorine gas, oxygen gas, and ozone-containing gas, the material of the fine channel is an organic polymer such as resin, and a part of the polymer chain is oxidized. It decomposes with the above strong gas and reacts to introduce a hydrophilic polar group such as a carboxyl group, and is not described for application to a fine channel formed of an inorganic material or the like.

  Here, in a fine channel made of an inorganic material, bubbles are often entrained and residual bubbles are generated in the channel. As a result, a slag flow phenomenon (alternate flow of water / gas / water) occurs, or flow resistance is increased or blocked, resulting in a state that hinders fluid movement. In addition, in order to form a multilayer flow in which water and an organic solvent do not mix with each other in the fine channel, it is necessary to control water wettability (contact angle is an index) with respect to the channel wall surface. Since water exists everywhere in the atmosphere, liquid, and solid surfaces, multilayer flow is not only liquid / liquid mixing but also liquid / gas and gas / gas mixed flows. Not too long. In addition, devices that incorporate fine channels made of inorganic materials are fundamentally used repeatedly by washing, unlike polymer disposable products, so proteins and oils that cause bubbles in the flow channel are used. It is necessary to completely remove adhesion residues such as droplets, and surface modification that reduces the adhesion affinity of these residues is required. As a method for solving such a problem, it is considered to be an effective means to hydrophilize the inner surface of the fine channel so that the contact angle of water droplets is 10 ° or less.

  By the way, the surface treatment of the inorganic material using ozone-containing dry oxygen gas has been conventionally performed. For example, a method is known in which a stainless steel polished to have a surface roughness of 1 μm is subjected to a heat oxidation treatment by treating it at an ozone concentration of 0.5 to 10 vol% and a temperature of 150 to 300 ° C. for 1 to 10 hours. (Japanese Patent Laid-Open No. 5-287,496).

  This method is intended to form a dense oxide film and is expected to suppress the elution of impurities from the member. However, when applied to a stainless steel microchannel, excessive oxidation of the surface may occur. It occurs, and iron surface concentration and chromium oxide decrease occur, and the surface is easily altered by the adsorption of proteins and the like. Furthermore, when applied to thin-walled tubular passages, hole-like passages, continuous void passages, etc., the large specific interface area causes problems such as thermal distortion of the fine structure and surface roughness, which is a problem in general structures. Even minor changes that are not possible are fatally affected. This minute change of the surface is not limited to a microstructure member made of stainless steel, but is a phenomenon that occurs even when formed of aluminum, glass, or a plating film.

  For the purpose of controlling the charge characteristics of stainless steel and promoting cleaning by decomposing surface dirt, an ozone treatment method has been proposed in which treatment is performed at an ozone concentration of 0.025 to 0.5% by volume and a temperature of 5 to 40 ° C. (Patent No. 2,944,985). In this method, the contact angle decreases only to about 40 to 55 °, and sufficient hydrophilic treatment cannot be performed. Thus, it is difficult to hydrophilize the contact angle of water droplets to 10 ° or less without any physical, chemical, or physicochemical changes in the fine flow path by the known ozone treatment. It is.

Japanese Patent Laid-Open No. 2003-272,654 JP 2004-117,179 A JP 2001-159,618 Japanese Unexamined Patent Publication No. 7-276,629 Japanese Patent Laid-Open No. 8-108,535 Japanese Patent Laid-Open No. 5-287,496 Japanese Patent No. 2,944,985

  Thus, as a result of intensive investigations to solve such problems, the present inventors have determined that a predetermined ozone content is present on the surface to be treated of the fine flow path even if the fine flow path is formed of an inorganic material. It was found that the contact angle of water droplets on the surface to be processed of the fine flow path can be reduced to 10 ° or less by contacting with dry oxygen gas under predetermined processing conditions, thereby completing the present invention.

  Accordingly, an object of the present invention is to provide a method for hydrophilizing a microchannel that can impart hydrophilicity with a contact angle of water droplets of 10 ° or less to the surface to be treated of the microchannel.

That is, the present invention provides a tubular channel, the channel diameter (diameter, depth or width) a hole shape path or groove-like passage is 5～600Myuemu, the fine flow path for fluid to flow, As a A method for hydrophilizing a fine channel for hydrophilizing a surface to be treated, wherein a dry oxygen gas having an ozone content of 0.2 to 30% by volume is treated at a treatment temperature of 100 to 200 ° C. This is a method for hydrophilizing a fine channel that is contacted under a treatment condition of a treatment time of 5 minutes or more and less than 60 minutes.

  In the present invention, the material of the fine channel to be hydrophilized is not particularly limited. However, since a uniform surface heating treatment at a relatively high temperature is necessary, the fine channel is preferably at least covered. The treated surface should be an inorganic material, and from the viewpoints of corrosion resistance, chemical resistance and cleanability, more preferably at least the treated surface is a metal such as aluminum, aluminum alloy, stainless steel, titanium, or borosilicate glass. It is formed of one or more materials selected from glass such as soda glass, metal oxides such as alumina and titania, and plating films such as nickel alloy plating and nickel composite plating. It is good.

  As for the shape of the fine flow path, for example, tubular paths such as pipes, injection nozzles, capillary columns, hole paths such as aluminum anodized pores and filtration filters, groove paths such as microchannels, ceramics, etc. Examples of the compacted body of particles and sintered metal, non-woven fabric, and continuous void paths such as columns packed with inorganic fine particles can be given as examples of products having such fine channels. Examples include biosensors, analytical tools, melt spinning production apparatuses, injection molding machines, various filtration apparatuses, and high-pressure water cutters.

  And the size or dimension (hereinafter referred to as “channel diameter”) such as the diameter, depth, width, etc. of the fine channel suitable for applying the hydrophilization method of the present invention is not particularly limited. However, from the viewpoint of the surface area to volume ratio (specific interfacial area), it is possible to hydrophilize a fine channel of 1 μm or more and 1,000 μm or less, but preferably 5 μm or more and 600 μm or less, more preferably 10 μm or more and 100 μm or less. If it is smaller than 5 μm, it is difficult to uniformly distribute ozone gas, and if it exceeds 600 μm, the specific interface area becomes small, and the reforming effect may be apparently reduced.

  The treatment conditions for hydrophilizing the surface to be treated of such a fine flow path are dry oxygen gas having an ozone content of 0.2 volume% to 30 volume%, preferably 2 volume% to 15 volume%. The processing temperature must be 100 ° C. or higher and 200 ° C. or lower, preferably 130 ° C. or higher and 180 ° C. or lower, and the processing time should be 5 minutes or longer and less than 60 minutes, preferably 10 minutes or longer and 30 minutes or shorter. . When the ozone content in the dry oxygen gas is lower than 0.2% by volume, the oxidizing power is insufficient. On the other hand, when it is higher than 30% by volume, the problem of excessive oxidation occurs, and when the processing temperature is lower than 100 ° C., the surface Condensation and dehydration of the hydroxyl group becomes insufficient. On the other hand, when the temperature is higher than 200 ° C., the problem of excessive oxidation occurs. Further, if the treatment time is shorter than 5 minutes, the surface to be treated may not reach an equilibrium state. When the time is longer than 60 minutes, improvement of the treatment effect cannot be expected, and the surface of iron may be concentrated due to excessive oxidation, so that the surface may easily deteriorate due to protein adsorption or the like.

The ozone-containing dry oxygen gas used in the hydrophilization treatment of the present invention preferably has a higher ozone concentration in terms of reaction kinetics. By the way, the ozone concentration obtained with a discharge-type ozonizer generally used is about 5% by volume, and this may be used by diluting with dry oxygen gas, or adsorbed on an adsorbent such as silica gel. You may concentrate and use. As the raw material gas supplied to the ozonizer, a high purity oxygen gas cylinder is generally used, and it can be said that a raw material gas having a high oxygen concentration is preferable in terms of reaction kinetics, but the oxygen capacity is at least 99.999. (5N) volume% or more, preferably 99.9999 (6N) volume% or more. If such a high purity oxygen gas cylinder is used, no additional drying treatment is necessary.
As for the heating method during the hydrophilization treatment, the temperature of the surface to be processed of the fine channel (object) may be heated to a predetermined temperature as a result. It is preferable to use a heating chamber or the like that is uniformly heated. Further, in the case where only the inner surface is processed like a tubular path or a hole-like path, the surface to be processed can be handled by partial heating from the outside of the processed object, and the heating chamber can be omitted.

  For example, the hydrophilization treatment method of the present invention is applied to a microreactor of a microreactor that is formed of a metal material such as aluminum, stainless steel, titanium, or the like and may flow an aqueous substance and an oily substance alternately. Then, by setting the hydrophilicity of the inner wall surface of the flow channel to 10 ° or less, water molecules are preferentially adsorbed on the inner wall surface of the flow channel, thereby suppressing the adsorption of oil droplets as much as possible. Further, wetting and spreading of the adsorbed oil droplets can be suppressed, and furthermore, oily substances adhering to the inner wall surface of the fine channel can be easily removed simply by flowing warm water through the fine channel. Therefore, the effect of reducing the flow resistance and promoting the introduction of liquid in the fine flow path is also exhibited.

  According to the method for hydrophilizing a microchannel according to the present invention, even if the microchannel is formed of an inorganic material, the contact angle of water droplets on the surface to be treated of the microchannel can be easily reduced to 10 ° or less. Can be reduced.

  Hereinafter, preferred embodiments of the present invention will be described in detail based on examples and comparative examples.

[Example 1]
Using a glass tube with an inner diameter of 0.6 mm and a length of 120 mm, the inner surface of this glass tube (the surface to be treated of a fine channel consisting of tubular channels) is prepared with a discharge-type ozonizer using high-purity oxygen gas (6N volume%) as a raw material. The resulting dried oxygen gas having an ozone content of 2% by volume was contacted for 30 minutes under heating at 150 ° C. while overflowing in one direction, and subjected to a hydrophilic treatment.

  About the glass tube after a hydrophilization process, after crushing a part of glass tube, it was set horizontally and the hydrophilic property of the inner surface was investigated. As a result, it was found that the contact angle of water droplets was 5 ° or less. In addition, the glass tube after this hydrophilization treatment is set up vertically and its lower end is submerged to a depth of 2 mm from the water surface, and the height of water rising in the glass tube due to capillary action (water capillary rising height) is measured. did. As a result, the capillary height of water was 48 mm.

[Comparative Example 1]
For the glass tube of Example 1 before the hydrophilization treatment, the contact angle of water droplets and the height of the water capillary were examined in the same manner as in Example 1 above. As a result, the contact angle of the water droplet was 25 to 30 °, and the capillary height of water was 12 mm.

[Example 2]
A fine flow path composed of a groove-like path having a depth of 100 μm × width of 100 μm is formed on the surface of the aluminum plate, and Example 1 is formed on the surface to be treated (the right and left side walls and the bottom face of the groove-like path). A dry oxygen gas having an ozone content of 2% by volume prepared in the same manner as described above was brought into contact in the same manner as in Example 1 and subjected to a hydrophilic treatment.

The contact angle of water droplets on the treated surface of the microchannel after the hydrophilization treatment was measured at the flat portion beside the groove-like path subjected to the hydrophilic treatment simultaneously with the groove-like path. As a result, the contact angle of the water droplet was 3 to 8 °.
In addition, water droplets (0.01 cc) are dropped into the fine channel from above, and the length of the water droplet spreads in the length direction of the fine channel in the fine channel (the extended length of the water droplet in the fine channel) Was measured. As a result, the extended length of the water droplet was 74 mm.

[Comparative Example 2]
For the same fine channel as in Example 2 before the hydrophilization treatment, the contact angle of the water droplet and the extended length of the water droplet in the fine channel were examined in the same manner as in Example 2. As a result, the contact angle of the water droplet was 68 °, and the extended length of the water droplet was 12 mm.

[Example 3 and Comparative Examples 3 and 4]
A stainless steel column (4 mmφ × 50 mm) having a particle size of 87 μm obtained by subjecting a dry oxygen gas having an ozone content of 2% by volume prepared in the same manner as in Example 1 to a heating ozone treatment at 150 ° C. for 10 minutes and a hydrophilization treatment. Stainless steel particles (Example 3), untreated stainless steel particles with a particle size of 87 μm (Comparative Example 3), or stainless steel particles with a particle size of 87 μm that were heated and ozone treated at 150 ° C. for 5 hours (Comparative Example) 4) was packed, and a fine channel composed of continuous void channels was formed in the column.

For each of the obtained fine channels of Example 3, Comparative Example 3 and Comparative Example 4, oil-in-water (O / O) obtained by dispersing gelatin in an amount of 5% by weight each using salad oil as an emulsifier as an oil component. W) Type emulsion was passed at a flow rate of 0.3 ml / min to contaminate the stainless steel particles forming each of the fine channels, and then 60 ° C hot water was passed at a flow rate of 0.3 ml / min. The emulsion desorbed in the warm water was collected over time, and a washing curve of washing time (min) -residual residual amount (mg) was created to examine the detergency of stainless steel particles with warm water.
The results are shown in FIG.

  As is clear from the results shown in FIG. 1, in the case of Example 3 (◯) according to the present invention, the cleaning speed is remarkably improved as compared with the case of untreated in Comparative Example 3 (●). I understand. In addition, in the case of Comparative Example 4 (Δ) in which the treatment time was 5 hours, although the ozone content and the heating temperature were the same as Example 3 (◯) of the present invention, excessive oxidation due to long-time treatment was performed. This problem occurs, and the cleaning speed is lower than that of the untreated case of Comparative Example 3 (●).

  According to the method for hydrophilizing a fine channel of the present invention, even if the fine channel is formed of an inorganic material, a dry oxygen gas having a predetermined ozone content is used on the surface to be treated of the fine channel. By contacting under predetermined processing conditions, the contact angle of water droplets on the surface to be processed of the fine channel can be easily reduced to 10 ° or less. For example, a microreactor, biosensor, analytical tool, capillary column, It can be suitably applied as a method for hydrophilizing a microchannel used as a fluid moving means in microchemistry, etc., which is promoted in many fields such as medicine, pharmacy, biology, engineering, etc. such as filtration filters. it can.

FIG. 1 is a graph of a cleaning curve of cleaning time (minutes) −residual residual amount (mg) showing the results of examining the cleaning performance in each fine channel of Example 3, Comparative Example 3 and Comparative Example 4.

Claims (4)

Tubular passage, the flow path diameter (diameter, depth or width) a hole shape path or groove-like path is that 5～600Myuemu, the fine flow path for fluid to flow, hydrophilic surface to be processed of their A method for hydrophilizing a fine channel to be treated, wherein a dry oxygen gas having an ozone content of 0.2 to 30% by volume is treated on a treatment surface of the fine channel at a treatment temperature of 100 to 200 ° C. and a treatment time of 5 minutes or more 60 A method for hydrophilizing a microchannel, wherein the contact is performed under a processing condition of less than a minute.   The method for hydrophilizing a fine channel according to claim 1, wherein at least a surface to be treated of the fine channel is formed of an inorganic material.   The method for hydrophilizing a microchannel according to claim 2, wherein a surface to be processed of the microchannel is formed of one or more materials selected from metal, glass, metal oxide, and plating film. . The method for hydrophilizing a microchannel according to claims 1 to 3 , wherein the contact angle of water droplets on the surface to be treated of the microchannel after the hydrophilization treatment is 10 ° or less.

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