Patent Description:
In recent years, microchips have been developed in which an area and/or a channel or channels for performing chemical and biological analyses are provided by application of micro-machining techniques used in the semiconductor industry. These microchips have begun to be utilized for electrochemical detectors in liquid chromatography, small electrochemical sensors in medical service sites, and the like.

Analytical systems using such microchips are called micro-TAS (micro-Total-Analysis System), lab-on-a-chip, bio chip or the like, and is paid attention to as a technology by which chemical and biological analyses can be enhanced in speed, efficiency and level of integration or by which analyzing devices can be reduced in size.

The micro-TAS, which enables analysis with a small amount of sample and enables disposable use of microchips, is expected to be applied particularly to biological analyses where precious trace amounts of samples or a multiplicity of specimens are treated.

An application example of the micro-TAS is a particulate analyzing technology in which characteristics of particulates such as cells and microbeads are analyzed optically, electrically or magnetically in channels arranged on microchips. In the particulate analyzing technology, fractional collection of a population satisfying a predetermined condition or conditions from among particulates on the basis of analytical results of the particulates is also conducted.

Patent Literature <NUM>, for example, discloses "a particulate fractionation microchip having a channel for introducing particulate-containing solution, and a sheath flow forming channel arranged on at least one lateral side of the introducing channel. " The particulate fractionation microchip further has "a particulate measuring section for measuring the particulates introduced, at least two particulate fractionating channels disposed on the downstream side of the particulate measuring section so as to perform fractional collection of the particulates, and at least two electrodes disposed in the vicinity of channel ports opening from the particulate measuring section into the particulate fractionating channels so as to control the moving direction of the particulates.

The particulate fractionation microchip disclosed in Patent Literature <NUM>, typically, is so designed that fluid laminar flows are formed by a "trifurcated channel" having a channel for introducing a particulate-containing solution and two sheath flow forming channels (see "<FIG>" of the literature).

<FIG> show a trifurcated channel structure according to related art (<FIG>), and sample liquid laminar flows formed by the channel structure (<FIG>). In the trifurcated channel, a sample liquid laminar flow passing through a channel <NUM> in the direction of solid-line arrow in <FIG> can be sandwiched, from the left and right sides, by sheath liquid laminar flows introduced through channels <NUM>, <NUM> in the directions of dotted-line arrows in the figure. By this, as shown in <FIG>, the sample liquid laminar flow can be fed through the center of the channel. Incidentally, in <FIG>, the sample liquid laminar flow is depicted in solid lines, and the channel structure in dotted lines.

According to the trifurcated channel shown in <FIG>, the sample liquid laminar flow is sandwiched by the sheath liquid laminar flows from the left and right sides, whereby with respect to the sandwiching direction (the Y-axis direction in <FIG>), the sample liquid laminar flow can be fed in the state of being deflected to an arbitrary position in the channel. With respect to the vertical direction (the Z-axis direction in <FIG>) of the channel, however, it has been very difficult to control the sample liquid feeding position. In other words, in the trifurcated channel according to related art, it has only been possible to form the sample laminar flow that is oblong in the Z-axis direction.

Therefore, the microchip having the trifurcated channel according to related art has the problem that in the case where, for example, a particulate-containing solution as a sample liquid is made to flow through a channel and subjected to optical analysis, there would be a dispersion of the feeding position of the particulates in the vertical direction (depth direction) of the channel. Therefore, there has been the problem that the flowing speed of particulates differs depending on the feeding position of the particulates, variation of detection signals increases, and the accuracy of analysis is degraded.

Patent Literature <NUM> discloses a channel structure that introduces a sample liquid into the center of a sheath liquid laminar flow from an opening at the center of the channel through which the sheath liquid laminar flow is fed to thereby feed the sample liquid laminar flow being surrounded by the sheath liquid laminar flow (see <FIG> and <FIG> of the literature). The channel structure enables the sample liquid to be introduced into the center of the sheath liquid laminar flow, thereby eliminating the dispersion of the feeding position of the particulates in the depth direction of the channel, so that the high accuracy of analysis can be obtained.

<FIG> show a channel structure according to related art applied for introducing a sample liquid to the center of a sheath liquid laminar flow (<FIG>), and a sample liquid laminar flow formed by the channel structure (<FIG>). In this channel structure, the sheath liquid laminar flow is introduced into each of channels <NUM> and <NUM> in the direction of arrow T in <FIG> and fed to a channel <NUM>. Then, the sample liquid fed to a channel <NUM> in the direction of arrow S can be introduced from an opening <NUM> to the center of the sheath liquid laminar flow fed through the channel <NUM>. The sample liquid laminar flow can be thereby fed, being converged to the center of the channel <NUM>, as shown in <FIG>. In <FIG>, the sample liquid laminar flow is depicted in solid lines, and the channel structure in dotted lines.

On the other hand, in Patent Literature <NUM>, it is pointed out that, when introducing the sample liquid laminar flow into the sheath liquid laminar flow in such a channel structure, turbulence occurs in the sample liquid laminar flow, which raises the case where the sample liquid laminar flow is not a flat and stable laminar flow (see the rows <NUM> to <NUM> in the right column on page <NUM> of the literature). Note that "flat laminar flow" indicates a laminar flow converted in the depth direction (the Z-axis direction) of the channel in <FIG>, and "non-flat laminar flow" indicates a laminar flow dispersed and spread in the depth direction of the channel.

In the above Patent Literature, it is proposed to provide the opening of the channel through which the sample liquid laminar flow is introduced with a pair of plate projections (see the reference numeral <NUM> in <FIG> of the literature) or the like in order to suppress the turbulence (wake) of the laminar flow at the merging portion of the sample liquid laminar flow and the sheath liquid laminar flows. The plate projections <NUM> extend from the opening wall of the channel through which the sample liquid laminar flow is introduced in the flowing direction of the sample liquid laminar flow and guides the sample liquid flowing out from the opening.

<CIT> is related to a sheath flow type flow-cell device. Herein, a sheath flow type flow-cell device for photo-particle-analyzer comprises a substantially flat top surface, at least one first inlet for sheath fluid, at least one first flow passage communicated with the at least one first inlet and contracted toward downstream to be a straight capillary flow passage, a discharge port provided at a terminal end of the straight capillary flow passage, a second inlet for sample fluid, a second flow passage for sample fluid communicated with the second inlet and contracted toward downstream, and coupling portions for sealingly coupling with the particle photo-analyzer. The second flow passage is opened within the at least one first flow passage so as to keep a part of the at least one first flow passage above and below an opening of the second flow passage. The opening is faced in the same direction as the straight capillary flow passage. A wall portion on which the opening locates is rounded. The wall portion is further chamfered and a pair of projections are extended from the wall portion.

<CIT> relates to a method for the hydrodynamic focusing of a fluid flow in a fluidic channel structure, in particular a microfluidic channel structure, according to which the fluid flow is hydrodynamically focused. To achieve this, the fluid flow is conducted in a fluid sheath flow with a swirling action that hydrodynamically focuses the fluid flow in a focusing channel section of the fluidic channel structure.

With the plate projections <NUM> disclosed in the above Patent Literature <NUM>, it is possible to guide the sample liquid flowing out from the opening and let the sample liquid flow through the channel as a stable laminar flow converged in the depth direction of the channel.

However, the channel structure is complicated when such a guide structure is provided at the opening of the channel through which the sample liquid laminar flow is introduced. Further, it is necessary to laminate three or more substrate onto one another in order to form such a channel structure on a microchip. Therefore, high accuracy is needed for the formation of the channel structure on each substrate and the lamination of the substrates, which increases the manufacturing cost of the microchip.

In light of the foregoing, it is desirable to provide a microchip capable of feeding a sample liquid laminar flow converged to the center of a channel and easily manufacturable.

This object is solved by the teachings of the independent claims.

There is provided a microchip according to claim <NUM>.

In the above microchip, a channel depth of the first introduction channel may be smaller than a channel depth of the second introduction channels, and a communicating port of the first introduction channel to the merge channel may be disposed at a substantially center position in a channel depth direction of the second introduction channels.

Further, a communicating port of the first introduction channel to the merge channel preferably opens in an area including respective channel walls of the second introduction channels.

There is provided a particulate analyzing device which includes the above microchip, wherein the microchip has a detecting portion that detects a particulate contained in a fluid fed from the first introduction channel on a downstream side of the contracted portion in the merge channel.

It should be noted that the "particulates" in the present embodiment widely include microscopic bioparticles such as cells, microorganisms, liposome, etc. as well as synthetic particles such as latex particles, gel particles, industrial particles, etc..

The microscopic bioparticles include chromosome, liposome, mitocondria, organelle, etc. which constitute various cells. The cells here include animal cells (blood corpuscle cells, etc.) and plant cells. The microorganisms includes bacteria such as colibacillus, etc., viruses such as tobacco mosaic virus, etc., and fungi such as yeast, etc. Further, the microscopic bioparticles may include also microscopic biopolymers such as nucleic acid, proteins, and complexes thereof.

The industrial particles may be, for example, organic or inorganic polymer materials, metals or the like. The organic polymer materials include polystyrene, stylene-vinylbenzene, and polymethyl methacrylate. The inorganic polymer materials include glass, silica, and magnetic materials. The metals include gold colloid and aluminum.

The shape of these particulates is usually spherical, but may be non-spherical. Besides, the particulates are not particularly limited as to size, mass or the like.

According to the embodiments of the present invention described above, a microchip capable of feeding a sample liquid laminar flow converged to the center of a channel and easily manufacturable is provided.

Preferred embodiments for carrying out the present invention will be described hereinafter with reference to the drawings. Note that the embodiments described below are typical exemplary embodiments of the present invention, and the invention is not to be narrowly construed due to the embodiments. The description will be given in the following order.

Fluid Velocity Vector Field in Channel Structure According to Related Art The channel structure according to related art which is applied for introducing a sample liquid to the center of a sheath liquid laminar flow, shown in <FIG>, has the problem that, when introducing the sample liquid laminar flow into the sheath liquid laminar flow, turbulence occurs in the sample liquid laminar flow, and the sample liquid laminar flow is not converted to the center of the channel.

Specifically, referring to <FIG>, in the case where a sample liquid laminar flow S is introduced from an opening <NUM> to the center of sheath liquid laminar flows T respectively introduced to channels <NUM> and <NUM> and flowing through a channel <NUM>, the sample liquid laminar flow S is dispersed in the depth direction of the channel (the Z-axis direction) in some cases. If the sample liquid laminar flow S is not converted to the center of the channel, the feeding position of the particulates contained in the sample liquid laminar flow S is dispersed in the depth direction of the channel, and therefore, the detection signal of the particulates also varies, which causes degradation of the accuracy of analysis.

The inventors of the present invention have conducted numerical calculation of the fluid velocity vector field (flow field) in the channel structure in order to find a factor of the turbulence of the sample liquid laminar flow occurring in the channel structure according to related art. As a result, they have found that the spiral flow field generated after the merging of the sample liquid laminar flow and the sheath liquid laminar flows causes the turbulence of the sample liquid laminar flow.

The fluid velocity vector field in the channel structure according to related art is described with reference to <FIG> and <FIG> are schematic sectional diagrams of the channel structure according to related art, in which <FIG> shows section P-P, <FIG> shows section Q-Q, and <FIG> shows section R-R, respectively in <FIG>.

When the sample liquid laminar flow S is introduced from the opening <NUM> into the center of the sheath liquid laminar flow T fed through the channel <NUM>, a high velocity vector appears at the center in the depth direction of the channel immediately after the introduction (see the arrows in <FIG>). It is considered that the high velocity vector occurs because the merged sample liquid laminar flow S and sheath liquid laminar flows T are concentrated on the center of the depth direction of the channel for flowing faster.

Further, in the process that the flow fields from the channel <NUM> and the channels <NUM> and <NUM> are merged into one flow field, a high velocity vector occurring at the center in the depth direction of the channel grows into the flow field that rotates in the Z-axis positive or negative direction as shown in <FIG>, and further grows into the spiral flow field as shown in <FIG>. Then, it has been founded that the sample liquid laminar flow S is stretched out in the Z-axis positive and negative direction and dispersed in the depth direction of the channel. It has been also found that the deformation of the sample liquid laminar flow S due to the spiral flow field becomes more significant depending on the flow rate of the sheath liquids fed from the channels <NUM> and <NUM>.

Furthermore, the inventors of the present invention have found, as a result of the numerical calculation of the fluid velocity vector field (flow field), that a slow flow field occurring near the opening for introducing the sample liquid laminar flow into the center of the sheath liquid laminar flow causes the turbulence of the sample liquid laminar flow.

<FIG> schematically illustrates a slow flow field occurring in the vicinity of an opening <NUM> of the channel structure according to related art, shown in <FIG>, which is applied for introducing the sample liquid to the center of the sheath liquid laminar flow.

In the vicinity of the opening <NUM>, a shear force occurs between the sheath liquid laminar flows T and the sample liquid laminar flow S due to the merging of the sheath liquids fed from the channels <NUM> and <NUM> and the sample liquid flowing out from the opening <NUM>. It has been found that, by the shear force, a slow velocity vector occurs in the vicinity of the opening <NUM>, and an unstable flow field with a stagnant flow is generated. Due to the stagnant flow field, the sample liquid laminar flow S becomes unstable and dispersed in the depth direction of the channel. It has been also found that the deformation of the sample liquid laminar flow S due to the stagnant flow field becomes more significant as the flow rate of the sample liquid flowing out of the opening <NUM> is lower.

A first feature of a microchip according to an embodiment of the present invention is to provide a channel structure that suppresses the above-described spiral flow field generated after merging of the sample liquid laminar flow and the sheath liquid laminar flows and thereby avoids the turbulence of the sample liquid laminar flow. A second feature of a microchip according to an embodiment of the present invention is to provide a channel structure that suppresses the above-described stagnant flow field generated in the vicinity of an opening for introducing the sample liquid laminar flow to the center of the sheath liquid laminar flow and thereby avoids the turbulence of the sample liquid laminar flow.

<FIG> are schematic diagrams illustrating a channel structure formed on a microchip according to a first example not part of the present invention, in which <FIG> shows a top view and <FIG> shows a sectional view.

In the figures, the reference numeral <NUM> indicates a first introduction channel (which is referred to hereinafter as a sample liquid introduction channel <NUM>) through which a first fluid (referred to hereinafter as a sample liquid) is introduced. The reference numerals <NUM> and <NUM> indicate second introduction channels (referred to hereinafter as sheath liquid introduction channels <NUM> and <NUM>) which are arranged to sandwich the sample liquid introduction channel <NUM> and merged with the sample liquid introduction channel <NUM> from the both sides thereof, and through which a second fluid (referred to hereinafter as a sheath liquid) is introduced. Further, the reference numeral <NUM> indicates a merge channel which is connected to the sample liquid introduction channel <NUM> and the sheath liquid introduction channels <NUM> and <NUM> and through which the sample liquid and the sheath liquids fed from the respective channels are merged and flow.

The sample liquid introduction channel <NUM> has, at the merging portion with the sheath liquid introduction channels <NUM> and <NUM>, a communicating port <NUM> for introducing the sample liquid into the center of the merge channel <NUM> through which the sheath liquid laminar flow T flows. The channel depth of the sample liquid introduction channel <NUM> in the Z-axis direction is designed to be smaller than the channel depth of the sheath liquid introduction channels <NUM> and <NUM>, and the communicating port <NUM> is disposed at substantially the center position in the channel depth direction of the sheath liquid introduction channels <NUM> and <NUM>. Further, the communicating port <NUM> is also disposed at substantially the center position in the channel width direction (the Y-axis direction) of the merge channel <NUM>.

By introducing the sample liquid laminar flow S to the center of the sheath liquid laminar flow T from the communicating port <NUM>, the sample liquid laminar flow S can be fed in the state of being surrounded by the sheath liquid laminar flow T (see also <FIG> described next). Note that the position where the communicating port <NUM> is placed is not limited to the center position of the channel depth direction of the sheath liquid introduction channels <NUM> and <NUM> and may be in its vicinity, as long as it allows the sample liquid laminar flow S to be fed into the merge channel <NUM> in the state of being surrounded by the sheath liquid laminar flow T. Likewise, the position of the communicating port <NUM> in the channel width direction of the merge channel <NUM> is not limited to the center position and may be in its vicinity.

In the figures, the reference numeral <NUM> indicates a tapered portion that functions to suppress the spiral flow field generated after the merging of the sample liquid laminar flow and the sheath liquid laminar flows illustrated in <FIG>. The tapered portion <NUM> is disposed in the merge channel <NUM> in close proximity to the merging portion of the sample liquid introduction channel <NUM> with the sheath liquid introduction channels <NUM> and <NUM>. The tapered portion <NUM> is formed so that the channel width in the sandwiching direction (the Y-axis direction) along which the sample liquid introduction channel <NUM> is sandwiched by sheath liquid introduction channels <NUM> and <NUM> is enlarged gradually along the feeding direction.

The fluid velocity vector field in the merge channel <NUM> and the function of the tapered portion <NUM> are described with reference to <FIG> and <FIG> are schematic sectional diagrams of the merge channel <NUM>, in which <FIG> shows section P-P, <FIG> shows section Q-Q, and <FIG> shows section R-R, respectively in <FIG>.

When the sample liquid laminar flow S is introduced from an opening <NUM> into the center of the sheath liquid laminar flow T flowing through the merge channel <NUM>, a high velocity vector appears at the center in the depth direction of the channel immediately after the introduction (see the dotted-line arrows in <FIG>). The high velocity vector occurs because the merged sample liquid laminar flow S and sheath liquid laminar flows T are concentrated on the center of the depth direction of the channel for flowing faster as described earlier.

At the tapered portion <NUM>, when the laminar flow width of the merged sample liquid laminar flow S and sheath liquid laminar flow T is enlarged in the Y-axis direction, a flow field (see the solid-line arrows in <FIG>), which is in reverse direction to the high velocity vector generated at the center in the depth direction of the channel, is generated. By generating the reverse flow field, the tapered portion <NUM> cancels out the flow field generated at the center in the depth direction of the channel and thereby prevents the flow field from growing into the spiral flow field. As a result, the sample liquid laminar flow S is maintained in the state of being converted to the center of the channel without being stretched out in the Z-axis direction by the spiral flow field (see <FIG>).

In the figures, the reference numeral <NUM> indicates a contracted portion that functions to narrow down the laminar flow width of the merged sample liquid laminar flow S and sheath liquid laminar flow T in the Y-axis direction and the Z-axis direction. The contracted portion <NUM> is disposed on the downstream side of the tapered portion <NUM>. The contracted portion <NUM> is formed so that the channel width is reduced gradually along the feeding direction. Further, the contracted portion <NUM> is formed so that the channel depth is also reduced gradually along the feeding direction. Specifically, the channel wall of the contracted portion <NUM> is formed to be narrowed along the feeding direction in the Y-axis and the Z-axis directions, and the contracted portion <NUM> is formed so that the area of the vertical section with respect to the feeding direction (the X-axis positive direction) decreases gradually. With such a shape, the contracted portion <NUM> feeds the liquids by narrowing down the laminar flow width of the merged sample liquid laminar flow S and sheath liquid laminar flow T in the Y-axis direction and the Z-axis direction.

<FIG> and <FIG> are schematic diagrams illustrating a structure of the communicating port <NUM>. The channel depth of the sample liquid introduction channel <NUM> in the Z-axis direction is designed to be smaller than the channel depth of the sheath liquid introduction channels <NUM> and <NUM>, and the communicating port <NUM> is placed at substantially the center position of the channel depth direction of the sheath liquid introduction channels <NUM> and <NUM> (see <FIG>). Further, in order to suppress the stagnant flow field generated in the vicinity, the communicating port <NUM> opens in an area including channel walls <NUM> and <NUM> of the sheath liquid introduction channel <NUM> and the sheath liquid introduction channel <NUM>.

This is described specifically with reference to <FIG>. First, a structure of the opening <NUM> in the channel structure according to related art (see <FIG>) is described with reference to <FIG>. In the channel structure according to related art, by a shear force which occurs between the sheath liquid laminar flows T and the sample liquid laminar flow S due to the merging of the sheath liquids fed from the channels <NUM> and <NUM> and the sample liquid flowing out from the opening <NUM>, an unstable flow field with a stagnant flow (the diagonally shaded area in <FIG>) is generated in the vicinity of the opening <NUM> (see also <FIG>).

In this case, the sample liquid flows out to the stagnant, unstable flow field from the opening <NUM>. Consequently, the sample liquid laminar flow S becomes unstable before coming into contact with the fast-flowing sheath liquids fed from the channels <NUM> and <NUM> and dispersed in the depth direction of the channel.

On the other hand, because the communicating port <NUM> of the microchip according to the embodiment opens in an area including the channel walls <NUM> and <NUM> of the sheath liquid introduction channel <NUM> and the sheath liquid introduction channel <NUM>, the sample liquid flowing out of the communicating port <NUM> comes into direct contact with the fast-flowing sheath liquids fed through the sheath liquid introduction channels <NUM> and <NUM>. Consequently, the sample liquid laminar flow S is accelerated by the sheath liquids immediately after flowing out of the communicating port <NUM> and thereby maintained in the stable state of being converted to the center of the channel without being dispersed in the depth direction.

Note that the shape of the communicating port <NUM> described herein may be regarded as a shape that the side end of the communicating port <NUM> of the sample liquid introduction channel <NUM> is cut out by the channel walls <NUM> and <NUM> of the sheath liquid introduction channel <NUM> and the sheath liquid introduction channel <NUM>. Because the shape of the communicating port <NUM> is made by the cutout by the channel walls <NUM> and <NUM> of the sheath liquid introduction channel <NUM> and the sheath liquid introduction channel <NUM>, the channel width indicated by the symbol W in <FIG> is designed to be smaller than the channel width after cutout indicated by the symbol C.

<FIG> illustrates the case where the tapered portion <NUM> is disposed in the merge channel <NUM> on the downstream side of the communicating port <NUM>, which is the merging portion of the sample liquid introduction channel <NUM> with the sheath liquid introduction channels <NUM> and <NUM>. However, the position where the tapered portion <NUM> is disposed is not limited to the position shown in <FIG>, as long as it is in close proximity to the merging portion of the sample liquid introduction channel <NUM> with the sheath liquid introduction channels <NUM> and <NUM>.

<FIG> show alternative examples of the tapered portion <NUM>, in which the upper part shows a top schematic view and the lower part shows a sectional schematic view. As shown in <FIG>, for example, the tapered portion <NUM> may be placed so that the point at which the channel width in the Y-axis direction begins to increase is located on the upstream side of the communicating port <NUM>. Further, as shown in <FIG>, the tapered portion <NUM> may be placed so that the point at which the channel width in the Y-axis direction begins to increase is located at the position coinciding with the communicating port <NUM>. Note that <FIG> shows the case where the point at which the channel width in the Y-axis direction begins to increase is located on the downstream side of the communicating port <NUM> and the tapered portion <NUM> is placed on the downstream side of the communicating port <NUM>.

<FIG> are schematic diagrams illustrating a channel structure on a microchip according to a second example not part of the present invention, in which <FIG> shows a top view and <FIG> shows a sectional view.

In the figures, the reference numeral <NUM> indicates a sample liquid introduction channel through which a sample liquid is introduced. The reference numerals <NUM> and <NUM> indicate sheath liquid introduction channels which are arranged to sandwich the sample liquid introduction channel <NUM> and merged with the sample liquid introduction channel <NUM> from the both sides thereof, and through a sheath liquid is introduced. Further, the reference numeral <NUM> indicates a merge channel which is connected to the sample liquid introduction channel <NUM> and the sheath liquid introduction channels <NUM> and <NUM> and through which the sample liquid and the sheath liquids fed from the respective channels are merged and flow.

The sample liquid introduction channel <NUM> has, at the merging portion with the sheath liquid introduction channels <NUM> and <NUM>, a communicating port <NUM> for introducing the sample liquid into the center of the merge channel <NUM> through which the sheath liquid laminar flow T flows.

The channel depth of the sample liquid introduction channel <NUM> in the Z-axis direction is designed to be smaller than the channel depth of the sheath liquid introduction channels <NUM> and <NUM>, and the communicating port <NUM> is disposed at substantially the center position in the channel depth direction of the sheath liquid introduction channels <NUM> and <NUM>. Further, the communicating port <NUM> is also disposed at substantially the center position in the channel width direction (the Y-axis direction) of the merge channel <NUM>.

In the figures, the reference numeral <NUM> indicates a tapered portion that functions to suppress the spiral flow field generated after the merging of the sample liquid laminar flow and the sheath liquid laminar flows illustrated in <FIG>. The tapered portion <NUM> is disposed in the merge channel <NUM> in close proximity to the merging portion of the sample liquid introduction channel <NUM> with the sheath liquid introduction channels <NUM> and <NUM>. The tapered portion <NUM> is formed so that the channel depth in the vertical direction (the Z-axis direction) perpendicular to the plane (X-Y plane) containing the sample liquid introduction channel <NUM> and the sheath liquid introduction channels <NUM> and <NUM> is narrowed gradually along the feeding direction.

At the tapered portion <NUM>, when the laminar flow width of the merged sample liquid laminar flow S and sheath liquid laminar flow T is narrowed in the Z-axis direction, a flow field (see the solid-line arrows in <FIG>), which is in reverse direction to the high velocity vector generated at the center in the depth direction of the channel, is generated. By generating the reverse flow field, the tapered portion <NUM> cancels out the flow field generated at the center in the depth direction of the channel and thereby prevents the flow field from growing into the spiral flow field. As a result, the sample liquid laminar flow S is maintained in the state of being converted to the center of the channel without being stretched out in the Z-axis direction by the spiral flow field (see <FIG>).

In the figures, the reference numeral <NUM> indicates a contracted portion that functions to narrow down the laminar flow width of the merged sample liquid laminar flow S and sheath liquid laminar flow T in the Y-axis direction and the Z-axis direction. The structure and the action of the contracted portion <NUM> are the same as those in the microchip according to the first embodiment and not redundantly described. Further, the structure and the action of the communicating port <NUM> are also the same as those in the microchip according to the first embodiment.

<FIG> illustrates the case where the tapered portion <NUM> is disposed so that the point at which the channel depth in the Z-axis direction begins to decrease coincides with the position of the communicating port <NUM>. However, the position where the tapered portion <NUM> is disposed is not limited to the position shown in <FIG>, as long as it is in close proximity to the merging portion of the sample liquid introduction channel <NUM> with the sheath liquid introduction channels <NUM> and <NUM>.

<FIG> show alternative examples of the tapered portion <NUM>, in which the upper part shows a top schematic view and the lower part shows a sectional schematic view, of the tapered portion <NUM>. As shown in <FIG>, for example, the tapered portion <NUM> may be placed so that the point at which the channel depth in the Z-axis direction begins to decrease is located on the upstream side of the communicating port <NUM>. Further, as shown in <FIG>, the tapered portion <NUM> may be placed so that the point at which the channel depth in the Z-axis direction begins to decrease is located on the downstream side of the communicating port <NUM>. Note that <FIG> shows the case where the point at which the channel depth in the Z-axis direction begins to decrease is located at the position coinciding with the communicating port <NUM> as in the case of <FIG>.

A taper angle (see the symbol (theta)z in <FIG>) in the channel depth direction of the tapered portion <NUM> may be set to any value as long as the function of the tapered portion <NUM> can be exerted. By setting the taper angle (theta)z to be larger than the merging angle (see the symbol (theta)y in <FIG>) of the sheath liquid introduction channels <NUM> and <NUM> with the sample liquid introduction channel <NUM>, the effect of suppressing the generation of the spiral flow field can be enhanced. Further, in the case where the channel width of the merge channel <NUM> is designed to be reduced gradually along the feeding direction, by setting the taper angle (theta)z to be larger than the draw angle (see the symbol (theta)y in <FIG>) of the merge channel <NUM>, the sufficient effect of suppressing the spiral flow field can be obtained.

Although the case where the tapered portion <NUM> and the contracted portion <NUM> are formed discontinuously is illustrated in <FIG>, the tapered portion <NUM> and the contracted portion <NUM> may be formed continuously as illustrated in <FIG>.

<FIG> are schematic diagrams illustrating a channel structure on a microchip according to a first third embodiment of the present invention, in which <FIG> shows a top view and <FIG> shows a sectional view, respectively of the microchip.

In the figures, the reference numerals <NUM> and <NUM> indicate tapered portions that function to suppress the spiral flow field generated after the merging of the sample liquid laminar flow and the sheath liquid laminar flows illustrated in <FIG>. The tapered portions <NUM> and <NUM> are disposed in the merge channel <NUM> in close proximity to the merging portion of the sample liquid introduction channel <NUM> with the sheath liquid introduction channels <NUM> and <NUM>. The tapered portion <NUM> is formed so that the channel width in the sandwiching direction (the Y-axis direction) along which the sample liquid introduction channel <NUM> is sandwiched by sheath liquid introduction channels <NUM> and <NUM> is enlarged gradually along the feeding direction. Further, the tapered portion <NUM> is formed so that the channel depth in the vertical direction (the Z-axis direction) perpendicular to the plane (X-Y plane) containing the sample liquid introduction channel <NUM> and the sheath liquid introduction channels <NUM> and <NUM> is narrowed gradually along the feeding direction. In the microchip according to the embodiment, the tapered portions <NUM> and <NUM> are formed in a partially overlap area of the merge channel <NUM>.

The fluid velocity vector field in the merge channel <NUM> and the function of the tapered portions <NUM> and <NUM> are described with reference to <FIG> and <FIG> are schematic sectional diagrams of the merge channel <NUM>, in which <FIG> shows section P-P, <FIG> shows section Q-Q, and <FIG> shows section R-R, respectively in <FIG>.

At the tapered portion <NUM>, when the laminar flow width of the merged sample liquid laminar flow S and sheath liquid laminar flow T is enlarged in the Y-axis direction, and at the tapered portion <NUM>, when the laminar flow width of the merged sample liquid laminar flow S and sheath liquid laminar flow T is narrowed in the Z-axis direction, a flow field (see the solid-line arrows in <FIG>), which is in reverse direction to the high velocity vector generated at the center in the depth direction of the channel, is generated. By generating the reverse flow field, the tapered portions <NUM> and <NUM> cancel out the flow field generated at the center in the depth direction of the channel and thereby prevent the flow field from growing into the spiral flow field. As a result, the sample liquid laminar flow S is maintained in the state of being converted to the center of the channel without being stretched out in the Z-axis direction by the spiral flow field (see <FIG>).

Further, <FIG> illustrates the case where the tapered portion <NUM> is disposed so that the point at which the channel depth in the Z-axis direction begins to decrease coincides with the position of the communicating port <NUM>. However, the position where the tapered portion <NUM> is disposed is not limited to the position shown in <FIG>, as long as it is in close proximity to the merging portion of the sample liquid introduction channel <NUM> with the sheath liquid introduction channels <NUM> and <NUM>.

Furthermore, <FIG> illustrate the case where the point of the tapered portion <NUM> at which the channel depth in the Z-axis direction begins to decrease is disposed on the upstream side of the point of the tapered portion <NUM> at which the channel width in the Y-axis direction begins to increase. However, the point at which the tapered portion <NUM> begins and the point at which the tapered portion <NUM> begins may be different or the same. Likewise, although <FIG> illustrate the case where the point of the tapered portion <NUM> at which the channel width in the Y-axis direction ends to increase and the point of the tapered portion <NUM> at which the channel depth in the Z-axis direction ends to decrease are disposed on the same position, the point at which the tapered portion <NUM> ends and the point at which the tapered portion <NUM> ends may be different or the same.

<FIG> shows an alternative example of the tapered portions <NUM> and <NUM>. In this alternative example, the positions of the point of the tapered portion <NUM> at which the channel width in the Y-axis direction begins to increase and the point of the tapered portion <NUM> at which the channel depth in the Z-axis direction begins to decrease both coincide with the communicating port <NUM>. Further, the positions of the point at which the tapered portion <NUM> ends and the point at which the tapered portion <NUM> ends also coincide with each other.

Further, although the case where the tapered portion <NUM> and the contracted portion <NUM> are formed discontinuously is illustrated in <FIG>, the tapered portion <NUM> and the contracted portion <NUM> may be formed continuously as illustrated in <FIG> in a further example not part of the present invention.

The material of the microchip according to the embodiment of the present invention may be glass or various kinds of plastic (PP, PC, COP, PDMS). In the case where the analysis using the microchip is carried out optically, it is preferred to select a material having light transmittance, with low autofluorescence, and with small optical errors because of small wavelength dispersion.

In order to maintain the light transmittance of the microchip, its surface is preferably coated with a so-called hard coat layer which is used for an optical disc. If a stain such as fingerprints is attached to the surface of the microchip, particularly, the surface of an optical detector, the amount of light transmission decreases to cause the degradation of accuracy of optical analyses. By depositing the hard coat layer with high transparency and stain resistance on the surface of the microchip, the degradation of accuracy of analysis can be prevented.

The hard coat layer can be formed by use of one of the hard coating agents which are used ordinarily, for example, a UV-curing type hard coating agent admixed with a fingerprint stain-proofing agent such as a fluoro or silicone stain-proofing agent. <CIT> discloses an active energy ray curable composition (P) as a hard-code agent which contains a multifunctional compound (A) having at least two polymerizable functional groups capable of being polymerized under active energy rays, modified colloidal silica (B) whose average particle diameter is <NUM> to <NUM>, and whose surface has been modified by a mercaptosilane compound in which an organic group having a mercapto group and a hydrolysable group or hydroxyl group are bonded to silicon atom, and a photopolymerization initiator (C).

Forming of the sample liquid introduction channel <NUM>, the sheath liquid introduction channels <NUM> and <NUM>, the merge channel <NUM> having the tapered portions <NUM> and <NUM> and the contracted portion <NUM> and the like arranged in the microchip can be carried out by wet etching or dry etching of a glass-made substrate layer, or by nanoimprint technique or injection molding or cutting of a plastic-made substrate layer. Then, the two substrates on which the sample liquid introduction channel <NUM> and the like is formed are laminated onto each other, whereby the microchip can be fabricated. The lamination of the substrates onto each other can be carried out by appropriately using a known method, such as heat fusing, adhesion with an adhesive, anodic bonding, bonding by use of a pressure sensitive adhesive-coated sheet, plasma-activated bonding, ultrasonic bonding, etc..

A manufacturing method of the microchip according to the embodiment of the present invention is described hereinafter with reference to <FIG> and <FIG>. <FIG> show top schematic diagrams of substrates constituting the microchip according to the embodiment of the present invention. <FIG> show sectional diagrams of the microchip according to the embodiment of the present invention. <FIG> shows section P-P in <FIG>.

First, part of the sheath liquid introduction channels <NUM> and <NUM> and part of the merge channel <NUM> are made on a substrate a (see <FIG>). On the substrate a, a sample liquid supply port <NUM> for supplying a sample liquid to the sample liquid introduction channel <NUM>, a sheath liquid supply port <NUM> for supplying a sheath liquid to the sheath liquid introduction channels <NUM> and <NUM>, and an discharge port for discharging the sample liquid and the sheath liquid from the merge channel <NUM> are also made. Next, the sample liquid introduction channel <NUM>, part of the sheath liquid introduction channels <NUM> and <NUM> and part of the merge channel <NUM> are made on a substrate b (see <FIG>).

Next, the substrate a and the substrate b are laminated onto each other by thermocompression bonding or the like as shown in <FIG>, whereby the microchip can be fabricated. In this step, the sheath liquid introduction channels <NUM> and <NUM> are created at different depths on the substrates a and b so that the sample liquid introduction channel <NUM> is located at substantially the center in the channel depth direction of the sheath liquid introduction channels <NUM> and <NUM>.

As described above, the microchip according to the embodiment of the present invention may be manufactured by laminating the substrates a and b on which the sample liquid introduction channel <NUM> and the like is made. Therefore, differently from the microchip disclosed in the above-described Patent Literature <NUM> in which the guide structure is provided at the opening of the channel for introducing the sample liquid laminar flow, the microchip according to the embodiment of the present invention can be manufactured by the lamination of two substrates only. The formation of the channel structure onto each substrate and the lamination of the substrates are thus easy, thereby suppressing the manufacturing cost of the microchip.

The above-described microchip can be incorporated into a particulate analyzing device according to an embodiment of the present invention. The particulate analyzing device is applicable as a particulate fractionating device that analyzes the characteristics of particulates and performs fractionation of particulates on the basis of the analytical results.

In the particulate analyzing device, a detector (see the symbol D in <FIG>) for detecting particulates contained in the sample liquid fed from the sample liquid introduction channel <NUM> is placed on the downstream side of the tapered portion <NUM> or <NUM> and the contracted portion <NUM> in the merge channel <NUM> of the microchip.

The microchip according to the embodiment of the present invention makes it possible, with the tapered portion <NUM>, <NUM>, to feed the sample liquid laminar flow S in the state of being converted to the center of the merge channel <NUM> and thereby eliminate the dispersion of the feeding position of the particulates in the depth direction of the channel and the difference in the flowing speed of the particulates caused by the dispersion (see <FIG> etc.). Thus, by placing the detecting portion D on the downstream side of the tapered portion <NUM>, <NUM> and detecting particulates, it is possible to eliminate the variation of detection signals caused by the difference in the flowing speed of the particulates and thereby achieve the detection of particulates with high accuracy.

Further, the microchip according to the embodiment of the present invention makes it possible, with the contracted portion <NUM>, to feed the liquids by narrowing down the laminar flow width of the sample liquid laminar flow S and the sheath liquid laminar flow T in the channel width direction and depth direction. By narrowing down the laminar flow width of the sample liquid laminar flow S and the sheath liquid laminar flow T, the particulates can be made to be arranged in a row in the sample liquid laminar flow S, and the dispersion of the feeding position of the particulates in the depth direction of the channel and the difference in the flowing speed of the particulates caused by the dispersion can be further reduced. Thus, by placing the detecting portion D on the downstream side of the contracted portion <NUM> and detecting particulates, it is possible to detect the particulates one by one and also make detection by eliminating the variation of detection signals caused by the difference in the flowing speed of the particulates as much as possible.

The detecting portion D may be configured as an optical detection system, an electrical detection system, or a magnetic detection system. Those detection systems may be configured in the same manner as those in particulate analyzing systems using microchips according to related art.

Specifically, the optical detection system includes a laser beam source, an irradiation section composed of a condenser lens and the like for condensing the laser beam and irradiating each of the particulates with the laser beam, and a detection system for detecting the light generated from the particulate upon irradiation with the laser beam by use of a dichroic mirror, a bandpass filter and the like. The detection of the light generated from particulates may be made by an area image pick-up element such as a PMT (photo multiplier tube), a CCD or a CMOS device, for example.

Further, the electrical detection system or the magnetic detection system places micro-electrodes on the channel of the detecting portion D and thereby measure, for example, resistance, capacitance, inductance, impedance, variation in electric field between the electrodes or the like, or, alternatively, magnetization, variation in magnetic field or the like.

The light, resistance, magnetization or the like generated from the particulates detected in the detecting portion D is converted into an electrical signal and output to a total control unit. Note that the light to be detected may be forward scattered light or side-way scattered light from the particulate, or scattered light, fluorescent light or the like arising from Reyleigh scattering, Mie scattering or the like.

Based on the electrical signal inputted, the total control unit measures the optical characteristics of the particulates. A parameter for the measurement of the optical characteristics is selected according to the particulates under consideration and the purpose of fractional collection. Specifically, forward scattered light is adopted in the case of determining the size of the particulates, side-way scattered light is adopted in the case of determination of structure, and fluorescent light is adopted in the case of determining whether a fluorescent material labeling the particulate is present or absent.

Further, the particulate analyzing device according to the embodiment of the present invention may be provided with the particulate fractionating channel as disclosed in the above Patent Literature <NUM> and an electrode for controlling the moving direction of particulates disposed near a channel port to the particulate fractionating channel, so as to analyze the characteristics of the particulates by the total control unit and perform fractionation of the particulates based on the analytical results.

Claim 1:
A microchip formed by two substrate layers (a, b) laminated onto each other and on which a fluid channel structure is formed, the fluid channel structure comprising:
- a first introduction channel (<NUM>);
- two second introduction channels (<NUM>, <NUM>) arranged to sandwich the first introduction channel (<NUM>) and merged with the first introduction channel (<NUM>) from both sides; and
- a merge channel (<NUM>) connected to the first introduction channel (<NUM>) and the second introduction channels (<NUM>, <NUM>), where fluids fed from the first and the second introduction channels are merged and flow,
wherein the merge channel (<NUM>) has a tapered portion (<NUM>) to suppress spiral flow field generated after the merging and formed so that a channel depth in a direction perpendicular to a plane containing the first introduction channel (<NUM>) and the second introduction channels (<NUM>, <NUM>) gradually decreases along a fluid feeding direction and a channel width in a sandwiching direction along which the first introduction channel (<NUM>) is sandwiched by the second introduction channels (<NUM>, <NUM>) gradually increases along a fluid feeding direction, and a contracted portion (<NUM>) disposed downstream of the tapered portion (<NUM>) and formed so that that the channel depth and the channel width gradually decrease along the fluid feeding direction, the tapered portion (<NUM>) and the contracted portion (<NUM>) are formed discontinuously,
wherein a part of the second introduction channels (<NUM>, <NUM>) and a part of the merge channel (<NUM>) are made on a first substrate layer (a),
wherein the first introduction channel (<NUM>), a part of the second introduction channels (<NUM>, <NUM>) and a part of the merge channel (<NUM>) are made on a second substrate layer (b), wherein the merge channel (<NUM>) downstream of the tapered portion (<NUM>) and the contracted portion (<NUM>) is made on the second substrate layer (b), and wherein the merge channel (<NUM>) upstream of the contracted portion (<NUM>), including the tapered portion (<NUM>), and the contracted portion (<NUM>) are fabricated on the two substrate layers (a, b).