Patent Publication Number: US-2010123457-A1

Title: Microparticle analysis device, micro-fluidic chip for microparticle analysis, and microparticle analysis method

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application claims priority to Japanese Priority Patent Application JP 2009-001471 filed in the Japan Patent Office on Jan. 7, 2009 and Japanese Priority Patent Application JP 2008-295086 filed in the Japan Patent Office on Nov. 19, 2008, the entire content of which is hereby incorporated by reference. 
     BACKGROUND 
     In recent years, development has advanced on micro-fluidic chips obtained by providing region and microfluidic channel for performing chemical and biological analysis on a substrate made of silicon or glass by applying microfabrication techniques in the semiconductor industry. These micro-fluidic chips have been used as e.g. electrochemical detectors for liquid chromatography and small electrochemical sensors in medical scenes. 
     The analysis system with such a micro-fluidic chip is referred to as a micro-total-analysis system (μ-TAS), a lab-on-chip, a biochip, and so on, and attracts attention as a technique that allows enhancement in the speed, efficiency, and integration degree of chemical and biological analysis and size reduction of analysis devices. 
     The μ-TAS has features that analysis can be performed with a small amount of sample and disposable (throwaway) micro-fluidic chips can be used. Therefore, the μ-TAS is expected to be applied to biological analysis in which a tiny amount of precious sample or a large number of specimens is treated particularly. 
     Application examples of the μ-TAS include a microparticle analysis technique in which characteristics of microparticles such as cells or microbeads are analyzed optically, electrically, or magnetically in a microfluidic channel provided on a micro-fluidic chip. In this microparticle analysis technique, fractional collection of a population (group) satisfying a predetermined condition from microparticles as a result of the analysis is also carried out. 
     For example, Japanese Patent Laid-open No. 2003-107099 (hereinafter referred to as Patent Document 1) discloses “a microparticle fractionation micro-fluidic chip having a microfluidic channel for introducing a solution containing microparticles and a sheath flow forming microfluidic channel disposed on at least one side of the microfluidic channel.” This microparticle fractionation micro-fluidic chip further has “a microparticle measurement part for measuring introduced microparticles, at least two microparticle fractionation microfluidic channels that are disposed on the downstream side of the microparticle measurement part and serve for fractional collection of microparticles, and at least two electrodes that are disposed near a microfluidic channel port from the microparticle measurement part to the microparticle fractionation microfluidic channel and serve to control the movement direction of microparticles.” 
     According to Patent Document 1, the microparticle fractionation micro-fluidic chip and the microparticle fractionation device having this micro-fluidic chip disclosed therein allow fractional collection of a population (group) satisfying a predetermined condition from microparticles. However, analysis by use of this microparticle fractionation device and so on takes a long time because the device is based on a system in which all of the introduced microparticles are measured by the microparticle measurement part and the microparticles satisfying the predetermined condition among the measured microparticles are sorted one by one into the microparticle fractionation microfluidic channel by the electrodes. Therefore, the analysis efficiency is significantly low particularly in the case of sorting a very small number of microparticles satisfying the predetermined condition among a large number of microparticles. 
     Accordingly, there is a need to provide a microparticle analysis device capable of efficiently sorting a population (group) satisfying a predetermined condition from microparticles. 
     SUMMARY 
     The present disclosure relates to microparticle analysis devices, micro-fluidic chips for microparticle analysis, and microparticle analysis methods. More specifically, the present disclosure relates to a microparticle analysis device and so on for chemical and biological analysis, capable of introducing a sample liquid containing magnetic microparticles and non-magnetic microparticles into a micro-fluidic chip to separate the microparticles by a magnetic field and analyzing the separated microparticles optically, electrically, or magnetically in a microfluidic channel. 
     According to an embodiment, there is provided a microparticle analysis device including (1) a micro-fluidic chip configured to have a region into which a sample liquid containing a magnetic microparticle and a non-magnetic microparticle is introduced, and a microfluidic channel communicating with the region on the downstream side in the liquid sending direction, (2) a magnetic field generator configured to form a magnetic field in the internal space of the region, and (3) a detector configured to detect an optical, electrical, or magnetic characteristic of a microparticle passing through the microfluidic channel. 
     This microparticle analysis device allows the following procedure. Specifically, the sample liquid containing the magnetic microparticle and the non-magnetic microparticle is introduced into the region on the micro-fluidic chip, having the internal space in which a magnetic field is formed by the magnetic field generator. Furthermore, the magnetic microparticle that does not pass through a magnetic space generated by the magnetic field generator is held in the region and simultaneously the non-magnetic microparticle that passes through the magnetic space generated by the magnetic field generator is sent to the microfluidic channel connected to the region on the downstream side in the liquid sending direction. In addition, a characteristic of the microparticle is analyzed by the optical, electrical, or magnetic detector in the microfluidic channel. 
     Furthermore, this microparticle analysis device allows the following procedure. Specifically, the sample liquid containing the magnetic microparticle and the non-magnetic microparticle is introduced into the region on the micro-fluidic chip, having the internal space in which a magnetic field is formed by the magnetic field generator. Furthermore, the magnetic microparticle that does not pass through a magnetic space generated by the magnetic field generator is held in the region and simultaneously the non-magnetic microparticle that passes through the magnetic space generated by the magnetic field generator is sent to the microfluidic channel connected to the region on the downstream side in the liquid sending direction. In addition, the non-magnetic microparticle is collected. 
     Moreover, this microparticle analysis device allows the following procedure. Specifically, the sample liquid containing the magnetic microparticle and the non-magnetic microparticle is introduced into the region on the micro-fluidic chip, having the internal space in which a magnetic field is formed by the magnetic field generator. Furthermore, the magnetic microparticle that does not pass through a magnetic space generated by the magnetic field generator is held in the region and simultaneously the non-magnetic microparticle that passes through the magnetic space generated by the magnetic field generator is sent to the microfluidic channel connected to the region on the downstream side in the liquid sending direction. Thereafter, the magnetic field formation by the magnetic field generator is stopped to send the magnetic microparticle held in the region to the microfluidic channel, and the magnetic microparticle is collected. 
     In this microparticle analysis device, the micro-fluidic chip of (1) includes a microtube that is connected to the region and introduces a sample liquid sent from the region into the microfluidic channel to form a sample liquid laminar flow in a sheath liquid laminar flow passing through the microfluidic channel. Due to this feature, the liquid can be sent to the microfluidic channel in such a way that the sample liquid laminar flow introduced from the microtube is surrounded by the sheath liquid laminar flow. 
     The microfluidic channel of the micro-fluidic chip of (1) has a narrowing part at a position that is closer to the downstream side in the liquid sending direction than the position of introduction of a sample liquid by the microtube and is closer to the upstream side in the liquid sending direction than a detection part at which detection of a characteristic of a microparticle by the detector is carried out, and the microfluidic channel inner diameter of the narrowing part is decreased gradually or in a stepwise manner in the liquid sending direction. Due to this feature, the sheath liquid laminar flow and the sample liquid laminar flow can be sent to the detection part in such a way that the laminar flow widths thereof are narrowed. Due to the narrowed sample liquid laminar flow, the liquid can be sent in such a way that the microparticles contained in the sample liquid are continuous with each other on one line in the microfluidic channel. Thus, at the detection part, at which detection of a characteristic of the microparticle by the detector is carried out, the microparticles can be individually analyzed optically, electrically, or magnetically one by one. 
     The microfluidic channel of the micro-fluidic chip of (1) has two sheath liquid discharge paths arising from branching into trifurcate paths from the microfluidic channel as the center of the branching at a branch part closer to the downstream side in the liquid sending direction than the detection part. This feature allows a part of the sheath liquid laminar flow To be separated from the microfluidic channel after passing through the detection part. These sheath liquid discharge paths can separate the sheath liquid introduced into the microfluidic channel with a large amount from the sample liquid laminar flow. Thus, dilution of the sample liquid by the excess sheath liquid can be prevented, and the concentration of the collected sample liquid can be kept at proper concentration. 
     The microparticle analysis device includes a liquid sending controller configured to return a sample liquid sent to a position closer to the downstream side in the liquid sending direction than the branch part of the microfluidic channel into the region or introduce the sample liquid into a collection tank. Due to the return of the sample liquid, the microparticle in the sample liquid passes through the magnetic space generated by the magnetic field generator in the region again. This can enhance the purity of the separation between the magnetic microparticle and the non-magnetic microparticle in the sample liquid. 
     In the micro-fluidic chip of (1), the space inner diameter of the internal space of the region along the direction of a magnetic field formed by the magnetic field generator is increased gradually or in a stepwise manner in the liquid sending direction. Due to this feature, magnetic acting force between the magnetic microparticle contained in the sample liquid introduced into the region and the magnetic field is increased gradually or in a stepwise manner in the liquid sending direction. This feature can prevent excess deposition of the magnetic microparticle on the sample liquid introduction part in the internal space of the region, and thus can evenly hold the magnetic microparticle in the internal space of the region. 
     In the micro-fluidic chip of (1), the region can be formed as a turn-back microfluidic channel made in a magnetic space generated by the magnetic field generator. Due to the turn-back microfluidic channel, the microparticle in the sample liquid passes through the magnetic space generated by the magnetic field generator in the region again. This can enhance the purity of the separation between the magnetic microparticle and the non-magnetic microparticle in the sample liquid. 
     In the micro-fluidic chip of (1), small projections and recesses may be processed on a region surface facing the internal space of the region or a film composed of a magnetic material may be formed on the region surface. Due to the region surface on which the small projections and recesses are processed, the effective area of the magnetic field generator can be increased, and the magnetic microparticle can be evenly held in the internal space of the region. Furthermore, by forming the film composed of a magnetic material on the region surface facing the internal space of the region, the efficiency of the magnetic field generator can be enhanced, and the magnetic microparticle can be efficiently held. Moreover, in the micro-fluidic chip of (1), a magnetic tube having a hollow shape can be provided in the internal space of the region. By providing the magnetic tube in such a way that its longitudinal direction corresponds with the liquid sending direction, the flow of the microparticle in the internal space can be adjusted. In addition, the magnetic microparticle can be efficiently held on the hollow surface and outside surface of the magnetic tube. 
     According to other embodiments, there are provided the micro-fluidic chip of (1) and a microparticle analysis device including this micro-fluidic chip, (2) magnetic field generating means for forming a magnetic field in the internal space of the region of the micro-fluidic chip, and (3) detecting means for detecting an optical, electrical, or magnetic characteristic of a microparticle passing through the microfluidic channel. 
     The embodiments provide a microparticle analysis device capable of efficiently sorting a population (group) satisfying a predetermined condition from microparticles and analyzing only the sorted microparticles optically, electrically, or magnetically. 
     Additional features and advantages are described herein, and will be apparent from the following Detailed Description and the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic diagram for explaining the configuration of a microparticle analysis device according to an embodiment; 
         FIG. 2  is a schematic diagram for explaining the configuration of a micro-fluidic chip for microparticle analysis according to the embodiment; 
         FIG. 3  is a schematic sectional view corresponding to the section along line P-P in  FIG. 2 ; 
         FIG. 4  is a schematic diagram showing another preferred form of the micro-fluidic chip for microparticle analysis according to the embodiment, in which hollow magnetic tubes are provided in the internal space of a region; 
         FIGS. 5A to 5D  are schematic diagrams for explaining preferred structures of a magnetic tube,  FIGS. 5A to 5C  are perspective views and  FIG. 5D  is a sectional view; 
         FIGS. 6A and 6B  are schematic sectional views showing a sheath liquid laminar flow and a sample liquid laminar flow formed in a microfluidic channel of a micro-fluidic chip,  FIG. 6A  corresponds to the section along line Q-Q in the enlarged view of  FIG. 2 , and  FIG. 6B  corresponds to the section along line R-R in the enlarged view of  FIG. 2 ; 
         FIG. 7  is a schematic sectional view that shows plural microtubes packed into a bundle, and corresponds to the section along line R-R in the enlarged view of  FIG. 2 ; 
         FIGS. 8A and 8B  are schematic sectional views showing the sheath liquid laminar flow and the sample liquid laminar flow around the upstream side and the downstream side, respectively, of a narrowing part of the micro-fluidic chip,  FIG. 8A  corresponds to the section along line M 1 -M 1  in  FIG. 6A , and  FIG. 8B  corresponds to the section along line M 2 -M 2  in  FIG. 6A ; 
         FIGS. 9A and 9B  are schematic sectional views showing the narrowing part whose microfluidic channel inner diameter is decreased in a stepwise manner in the liquid sending direction; 
         FIGS. 10A to 10C  are schematic diagrams for explaining a structural example of a branch part for sheath liquid discharge paths,  FIG. 10A  is a schematic perspective view,  FIG. 10B  is a sectional view corresponding to the section along line N 1 -N 1  in  FIG. 10A , and  FIG. 10C  is a sectional view corresponding to the section along line N 2 -N 2  in  FIG. 10A ; 
         FIGS. 11A to 11C  are schematic diagrams for explaining a structural example of the branch part for the sheath liquid discharge paths,  FIG. 11A  is a schematic perspective view,  FIG. 11B  is a sectional view corresponding to the section along line N 1 -N 1  in  FIG. 11A , and  FIG. 11C  is a sectional view corresponding to the section along line N 2 -N 2  in  FIG. 11A ; 
         FIG. 12  is a schematic diagram for explaining a structural example of the branch parts for the sheath liquid discharge paths  26  and  27 ; 
         FIG. 13  is a flowchart for explaining the steps of a microparticle analysis method (negative selection) according to the embodiment; 
         FIG. 14  is a flowchart for explaining the steps of the microparticle analysis method (positive selection) according to the embodiment; and 
         FIGS. 15A and 15B  are schematic perspective views showing the structures of the micro-fluidic chip a in which the surface of a detection part is recessed. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the present invention will be described below with reference to the drawings. The description will be made in the following order. 
     1. Outline of Configuration of Microparticle Analysis Device and Analysis-subject Microparticle
         (1) Outline of Device Configuration   (2) Analysis-subject Microparticle       

     2. Details of Configuration and Operation of Microparticle Analysis Device
         (1) Separation of Microparticle by Magnetic Field Generator   (2) Formation of Laminar Flow by Microtube   (3) Narrowing of Laminar Flow Width by Narrowing Part   (4) Characteristic Detection by Detector   (5) Concentration of Sample Liquid by Sheath liquid discharge path   (6) Collection or Return of Sample Liquid by Liquid Sending Controller       

     3. Microparticle Analysis Method
         (1) Sorting of Magnetically-unlabeled cell (Negative Selection)
           (1-1) Cell Labeling   (1-2) Cell Separation and Characteristic Detection   (1-3) Characteristic Determination and Collection or Return
               (1-3-1) Characteristic Determination   (1-3-2) Collection   (1-3-3) Return   
               
           (2) Sorting of Magnetically-Labeled Cell (Positive Selection)
           (2-1) Cell Labeling   (2-2) Cell Separation and Characteristic Detection   (2-3) Characteristic Determination and Collection or Return
               (2-3-1) Characteristic Determination   (2-3-2) Collection   (2-3-3) Return   
               
               

     4. Micro-fluidic Chip 
     1. Outline of Configuration of Microparticle Analysis Device and Analysis-subject Microparticle 
     (1) Outline of Device Configuration 
     With reference to  FIGS. 1 and 2 , the outline of the device configuration of a microparticle analysis device according to the embodiment of the present invention will be described below.  FIG. 1  is a schematic diagram showing a part of the configuration of the microparticle analysis device according to the present embodiment.  FIG. 2  is a schematic diagram showing the configuration of a micro-fluidic chip for microparticle analysis, incorporated in this microparticle analysis device. 
     Referring to  FIG. 1 , the microparticle analysis device indicated by symbol A includes a micro-fluidic chip a for microparticle analysis (hereinafter, referred to simply as “micro-fluidic chip a”), a magnetic field generator b that forms a magnetic field in a predetermined region (region  1 ) of this micro-fluidic chip a, and detectors c 1  and c 2  that detect an optical characteristic of microparticles at a predetermined part (microfluidic channel  2 ) of the micro-fluidic chip a. Although the magnetic field generator b is so shown in  FIG. 1  as to be separated from the micro-fluidic chip a for convenience, it is provided in contact with or be in proximity to the magnetic field formation region of the micro-fluidic chip a. Specifically, if the magnetic field generator b is provided as an external component of the micro-fluidic chip a, it is disposed at a part in contact with or in proximity to the magnetic field formation region on the device main body. If the magnetic field generator b is provided as an internal component of the micro-fluidic chip a, it is so provided as to be fabricated in the vicinity of the magnetic field formation region on the micro-fluidic chip a. 
     The micro-fluidic chip a has the region  1  (the region surrounded by the dotted line in  FIGS. 1 and 2 ) into which a sample liquid containing magnetic microparticles and non-magnetic microparticles is introduced. A magnetic field can be formed in the internal space of this region  1  by the magnetic field generator b. In the present embodiment, the region  1  is formed as a turn-back microfluidic channel formed in the magnetic space generated by the magnetic field generator b. In  FIGS. 1 and 2 , numerals  12  and  13  each indicate a turn-back part of the turn-back microfluidic channel. The region  1  is formed as the turn-back microfluidic channel that is inverted by 180 degrees at the turn-back parts  12  and  13 . The region  1  may be obtained by forming the region surrounded by the dotted line as e.g. one straight-line microfluidic channel having large width, and can be formed with any of various shapes in the magnetic space generated by the magnetic field generator b. 
     The sample liquid introduced from a sample liquid inlet indicated by numeral  11  in  FIGS. 1 and 2  into the region  1  by a liquid sending pump (not shown) is sent in the magnetic space generated by the magnetic field generator b via the turn-back parts  12  and  13  and sent to the microfluidic channel (see numeral  2  in the diagrams) formed in communication with the region  1 . The communication between the region  1  and the microfluidic channel  2  is obtained via a microtube  3  to be described later. 
     The sample liquid sent to the microfluidic channel  2  is subjected to detection of a characteristic of microparticles by the detectors c 1  and c 2 . The detectors c 1  and c 2  can be formed as an optical detection system, an electrical detection system, or a magnetic detection system similar to one in a microparticle analysis system with use of a micro-fluidic chip of a related art. Specifically, e.g. the optical detection system includes the detector c 1  composed of a laser light source, a condensing lens for focusing laser light on microparticles passing through the microfluidic channel  2  to irradiate the microparticles with the laser light, and so on, and the detector c 2  that detects light generated from the microparticles due to the laser light irradiation by using a dichroic mirror, a bandpass filter, and so on. The detector c 2  may be e.g. a photo multiplier tube (PMT) or an area imaging element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) element. The light detected by the detector c 2  is converted to an electrical signal and output to an overall controller f. Hereinafter, unless a particular reference is made, the description will be made based on the assumption that the detectors c 1  and c 2  are formed as the optical detection system and detect an optical characteristic of microparticles. 
     In  FIGS. 1 and 2 , numeral  21  denotes a sample liquid outlet for discharging the sample liquid from the microfluidic channel  2  to the outside of the micro-fluidic chip a. After the detection of an optical characteristic of the microparticles by the detectors c 1  and c 2 , the sample liquid discharged from the sample liquid outlet  21  is sent to a collection tank d or the sample liquid inlet  11 . In  FIG. 1 , symbols e 1  and e 2  denote liquid sending controllers for sending the sample liquid discharged from the sample liquid outlet  21  to either the collection tank d or the sample liquid inlet  11  selectively. The liquid sending controllers e 1  and e 2  can be formed with a generally-used valve, a liquid sending pump, and so on. When the liquid sending controller (valve) e 1  is closed and the liquid sending controller (valve) e 2  is opened, the sample liquid is introduced into the collection tank d. This collection tank d may be provided in plurality. In this case, the liquid sending controller (valve) e 2  is provided with a function to select any one or more collection tanks d and send the sample liquid into the selected tanks d. When the liquid sending controller (valve) e 1  is opened and the liquid sending controller (valve) e 2  is closed, the sample liquid is introduced into the sample liquid inlet  11  and returned into the region  1 . 
     A signal from the overall controller f is output to the magnetic field generator b and the liquid sending controllers e 1  and e 2  (see  FIG. 1 ). In response to this output, the magnetic field generator b forms a magnetic field or stops the formation of a magnetic field. Furthermore, in response to the output, the liquid sending controllers e 1  and e 2  send the sample liquid discharged from the sample liquid outlet  21  to either the collection tank d or the sample liquid inlet  11 . 
     (2) Analysis-Subject Microparticle 
     In the embodiment, the “microparticle” contained as the analysis subject in the sample liquid broadly encompasses biologically relevant microparticles such as cells, microorganisms, and liposomes, synthetic particles such as latex particles, gel particles, and industrial particles, and so on. 
     The biologically relevant microparticles encompass chromosomes, liposomes, mitochondrias, organelles, and so on included in various kinds of cells. The cells as the subject encompass animal cells (hemocyte cells and so on) and plant cells. The microorganisms encompass bacteria such as coliforms, viruses such as tobacco mosaic viruses, fungi such as yeasts, and so on. Moreover, the biologically relevant microparticles also encompass biologically relevant polymers such as nucleic acids, proteins, and complexes of these substances. The industrial particles may be composed of e.g. an organic or inorganic polymer material or a metal. The organic polymer material encompasses polystyrene, styrene divinylbenzene, polymethylmethacrylate, and so on. The inorganic polymer material encompasses glass, silica, magnetic materials, and so on. The metal encompasses gold colloids, aluminum, and so on. In general, the shape of these microparticles is a sphere. However, it may be a nonspherical shape, and the size, mass, and so on of the microparticles are also not particularly limited. 
     The “magnetic microparticle” refers to a magnetically-labeled biologically relevant microparticle or a synthetic particle containing e.g. a ferromagnetic material such as iron, cobalt, or nickel or a ferrite such as magnetite or chromite. The “non-magnetic microparticle” refers to a biologically relevant microparticle that is not magnetically labeled or a synthetic particle that contains neither a ferromagnetic material nor a ferrite. 
     The magnetic labeling of a biologically relevant microparticle can be carried out by using e.g. a magnetic bead antibody. The magnetic bead antibody refers to a material obtained by chemically coupling e.g. a ferromagnetic material or a ferrite formed as a spherical microbead to an antibody having the specific binding ability to a specific substance (antigen) by using a cross-linking agent. Currently, magnetic bead antibodies for various substances are commercially available. By coupling these magnetic bead antibodies to a substance contained in microparticles (particularly, a substance existing on the surface of the microparticles), the microparticles can be magnetically labeled. Furthermore, it will also be possible that the magnetic labeling of a biologically relevant microparticle is carried out e.g. by stirring powders of a ferromagnetic material, a ferrite, or the like and the biologically relevant microparticle under the existence of a flocculant such as poly aluminum chloride to thereby make a magnetic floc (magnetic aggregate). 
     2. Details of Configuration and Operation of Microparticle Analysis Device 
     The details of the respective device components in the microparticle analysis device A and the operation thereof will be described below by taking as an example the case of performing analysis and sorting of cells with use of a sample liquid containing cells that are magnetically labeled with a magnetic bead antibody as “magnetic microparticles” and cells that are not magnetically labeled with a magnetic bead antibody as “non-magnetic microparticles.” The cells that are magnetically labeled with a magnetic bead antibody will be referred to as “magnetically-labeled cells,” and the cells that are not magnetically labeled with a magnetic bead antibody will be referred to as “magnetically-unlabeled cells.” 
     (1) Separation of Microparticle by Magnetic Field Generator 
     As described with  FIG. 1 , the sample liquid introduced from the sample liquid inlet  11  into the region  1  by a liquid sending pump (not shown) is sent in the magnetic space generated by the magnetic field generator b via the turn-back parts  12  and  13 . 
       FIG. 3  is a schematic sectional view corresponding to the section along line P-P in  FIG. 2 . The sample liquid is sent from the right to the left in the diagram (in the X-axis negative direction). The magnetic field generator b is provided in contact with or in proximity to the region  1 , and a magnetic field is formed in the internal space of the region  1  by the magnetic field generator b. The block arrowheads in the diagram indicate the direction of the magnetic field formed by the magnetic field generator b. 
     The magnetic field generator b is formed as a unit capable of controlling formation and stop of a magnetic field, such as an electrically-applied electromagnet. As described above, if the magnetic field generator (electromagnet) b is provided as an external component of the micro-fluidic chip a, it is disposed at a part in contact with or in proximity to the region  1  on the device main body. If the magnetic field generator b is provided as an internal component of the micro-fluidic chip a, it is disposed near the region  1  on the micro-fluidic chip a; for example it is provided below the region  1  as shown in  FIG. 3 . If the magnetic field generator b is provided as an internal component, it is formed e.g. by fabricating an electromagnet in the substrate of the micro-fluidic chip a or by stacking the electromagnet on the substrate. 
     If the sample liquid containing the magnetically-labeled cells and the magnetically-unlabeled cells is introduced into the region  1  in the state in which a magnetic field is formed in the internal space of the region  1 , magnetic acting force works between the magnetization of the magnetically-labeled cells and the magnetic field. Due to this magnetic acting force, the magnetically-labeled cells are so held in the region  1  as to remain in the internal space of the region  1  against the liquid sending pressure of the sample liquid or be absorbed by the surface facing the internal space of the region  1 . On the other hand, the magnetically-unlabeled cells are sent to the microfluidic channel  2  (see  FIG. 1 ), which communicates with the region  1 , in accordance with the liquid sending pressure of the sample liquid because the magnetic acting force does not work between the magnetically-unlabeled cells and the magnetic field. 
     In this manner, the region  1  and the magnetic field generator b exert a function to separate the cells contained in the introduced sample liquid into the magnetically-labeled cells that do not pass through the magnetic space generated by the magnetic field generator b and the magnetically-unlabeled cells that pass through the magnetic space. This makes it possible to separate only the magnetically-unlabeled cells from the cells contained in the sample liquid and send the magnetically-unlabeled cells to the microfluidic channel  2  while a magnetic field is formed by the magnetic field generator b. 
     If, after the sending of the magnetically-unlabeled cells to the microfluidic channel  2 , the magnetic field formed by the magnetic field generator b is stopped to release the magnetic acting force on the magnetically-labeled cells, only the magnetically-labeled cells held in the region  1  can be sent to the microfluidic channel  2 . 
     To surely separate the magnetically-unlabeled cells from the magnetically-labeled cells, it is preferable to hold the magnetically-labeled cells in the region  1  by making them be absorbed by the surface facing the internal space of the region  1  (e.g. the bottom surface of the region  1 ). For this purpose, the magnetic field generator b forms a magnetic field with such intensity that sufficient magnetic attractive force can be generated between the magnetic field and the magnetization of the magnetically-labeled cells. 
     If the magnetically-labeled cells are held by making them be absorbed by the surface facing the internal space of the region  1 , a larger number of magnetically-labeled cells can be absorbed by the surface by forming small projections and recesses on the surface to thereby increase the surface area. Furthermore, the magnetic attractive force acting on the magnetically-labeled cells can be enhanced by coating the surface facing the internal space of the region  1  with a magnetic material such as iron, cobalt, nickel, or a ferrite by welding, vapor deposition, or another method. Alternatively, by filling the internal space with magnetic beads coated with the magnetic material such as iron, cobalt, nickel, or a ferrite by welding, vapor deposition, or another method, the surface area of the internal space can be increased and thus a larger number of magnetically-labeled cells can be absorbed by the surface. 
     In the case of holding the magnetically-labeled cells by making them be absorbed by the surface facing the internal space of the region  1 , if a large number of magnetically-labeled cells are unevenly absorbed at a certain part of the surface, possibly the internal space of the region  1  is narrowed by the magnetically-labeled cells held at this part and the sending of the sample liquid is inhibited. In particular, a large number of magnetically-labeled cells are contained in the sample liquid at the initial stage of the introduction thereof into the region  1 . Therefore, if strong magnetic attractive force acts on the magnetically-labeled cells on the upstream side of the region  1 , the magnetically-labeled cells are absorbed by the bottom surface of the region  1  at once and the narrowing easily occurs. To prevent this, it is preferable to allow comparatively-weak magnetic attractive force to act on the magnetically-labeled cells on the upstream side of the region  1  and gradually increase the magnetic attractive force in the flow sending direction toward the downstream side, to thereby permit the magnetically-labeled cells in the sample liquid to be evenly absorbed by the surface. 
     In the microparticle analysis device A, the space inner diameter of the inside of the region  1  (see symbol H in  FIG. 3 ) along the direction of the magnetic field formed by the magnetic field generator b is gradually increased in the liquid sending direction in order to gradually increase the magnetic attractive force acting on the magnetically-labeled cells. In the case of  FIG. 3 , in which the magnetic field generator b is disposed below the region  1  and a magnetic field along the Z-axis positive direction is formed in the internal space of the region  1  for making the magnetically-labeled cells be absorbed by the bottom surface of the region  1 , the bottom surface of the region  1  is formed as an inclined surface whose surface height in the Z-axis direction is gradually decreased in the liquid sending direction. Due to this feature, the distance between the magnetically-labeled cells passing through the region  1  and the magnetic field generator b (see symbol D in the diagram) is gradually decreased in the liquid sending direction. 
     When the distance D between the magnetically-labeled cells and the magnetic field generator b is smaller and thus the magnetically-labeled cells are closer to the magnetic field generator b, the magnetic attractive force acting on the magnetically-labeled cells is larger. In contrast, when the distance D between the magnetically-labeled cells and the magnetic field generator b is larger and thus the magnetically-labeled cells are farther away from the magnetic field generator b, the magnetic attractive force acting on the magnetically-labeled cells is smaller. Therefore, if the distance D is gradually decreased in the liquid sending direction, the magnetic attractive force acting on the magnetically-labeled cells passing through the region  1  can be gradually increased and thereby the magnetically-labeled cells can be evenly absorbed by the surface. 
     In the case of  FIG. 3 , the magnetic field generator b is disposed below the region  1  and the bottom surface of the region  1  is formed as an inclined surface, to thereby adjust the magnetic attractive force acting on the magnetically-labeled cells. However, the top surface or a side surface facing the internal space of the region  1  may be formed as an inclined surface depending on the position of the magnetic field generator b and the direction of the magnetic field formed by the magnetic field generator b. Furthermore, the surface (bottom surface, top surface, side surface) facing the internal space of the region  1  may be formed as a multi-stage surface having a shape of stairs instead of an inclined surface. 
     To make the magnetically-labeled cells be absorbed and held in the internal space of the region  1 , as shown in  FIG. 4 , a magnetic tube  14  (see also  FIGS. 5A to 5D ) having a hollow shape may be provided in the internal space of the region  1 . The magnetic tube  14  is so provided that its longitudinal direction corresponds with the liquid sending direction (see the arrowhead fin the diagram). 
       FIG. 4  is a schematic sectional view corresponding to the section along line P-P in  FIG. 2A . In the case of  FIG. 4 , the magnetic tubes  14  each formed into a hollow cylindrical shape are provided in the internal space of the region  1  at three stages in the Z-axis direction. In  FIG. 4 , the magnetic tubes  14  are provided in plurality also in the Y-axis direction. The number of magnetic tubes  14  provided in the internal space of the region  1  is not particularly limited. The number can be at least one, preferably two or more. The shape of the magnetic tube  14  is not limited to a cylindrical shape as long as it has a hollow shape, and the section thereof may have a polygonal shape such as a triangle or a quadrangle. 
     The magnetic tube  14  is formed of a magnetic material such as iron, cobalt, nickel, or a ferrite, and is formed into a hollow shape as shown in  FIG. 5A . If the magnetic tubes  14  are provided in the internal space of the region  1  as shown in  FIG. 4 , the magnetically-labeled cells introduced into the region  1  are sent through the hollow of the magnetic tube  14  or the gap between the magnetic tubes  14 . In addition, if a magnetic field is formed by the magnetic field generator b, the magnetically-labeled cells sent through the inside and outside of the magnetic tubes  14  are absorbed by the hollow surfaces and outside surfaces of the tubes. If the inner diameter, outer diameter, and length of the magnetic tube  14  are defined as r 1 , r 2 , and 1, respectively, the area S of the surface that can absorb the magnetically-labeled cells, of each magnetic tube  14 , is “S=2π1(r 1 +r 2 ).” Therefore, similarly to the above-described case in which the internal space of the region  1  is filled with magnetic beads coated with a magnetic material, the area of the surface capable of absorbing the magnetically-labeled cells can be increased and the magnetically-labeled cells can be efficiently held in the internal space of the region  1 . 
     Moreover, the flow of the cells in the internal space of the region  1  can be adjusted by providing the magnetic tubes  14  to thereby allow the cells introduced into the region  1  to be sent through the hollow of the magnetic tube  14  or the gap between the magnetic tubes  14 . This feature also makes it possible to prevent inhibition of the sample liquid sending due to the clogging of the cells in the internal space of the region  1 . 
     If small projections and recesses are formed on the hollow surface and outside surface of the magnetic tube  14 , the area of the surface capable of absorbing the magnetically-labeled cells can be further increased. Furthermore, it is also possible that, as shown in  FIGS. 5B and 5C , small holes  141  are formed in the tube wall of the magnetic tube  14  or the magnetic tube  14  is formed into a coil shape (spring shape) having gaps  142 . If such a magnetic tube  14  is provided, the magnetically-labeled cells that move into/from the inside/outside of the magnetic tube  14  via the holes  141  or the gaps  142  can be absorbed by the surfaces of the holes  141  or the gaps  142 . This can further increase the area of the surface capable of absorbing the magnetically-labeled cells. 
     It is preferable that the magnetic tube  14  be formed into a hollow cylinder having small wall thickness in order to suppress the rise of the liquid sending pressure and prevent the clogging of the cells in the tube hollow. Furthermore, it is also possible that, as shown in  FIG. 5D , the magnetic tube  14  is formed into a hollow cylinder having a tapered tube wall so that the inner diameter of the tube on the upstream side in the liquid sending direction (see the arrowhead f in the diagram) may be wider whereas the inner diameter on the downstream side be narrower. This is also effective to prevent the clogging of the cells in the tube hollow. 
     (2) Formation of Laminar Flow by Microtube 
     The sample liquid sent in the region  1  is introduced from the region  1  to the microfluidic channel  2  by the microtube (see numeral  3  in  FIGS. 1 and 2 ) connected to the end part of the region  1 . The sample liquid introduced to the microfluidic channel  2  contains either the magnetically-unlabeled cells that are separately sent while a magnetic field is formed by the magnetic field generator b or the magnetically-labeled cells that are sent thereafter while the magnetic field formation by the magnetic field generator b is stopped. 
     In the enlarged view of  FIG. 2 , numeral  31  denotes an opening of the microtube  3  closer to the end part of the region  1 , and numeral  32  denotes an opening of the microtube  3  closer to the microfluidic channel  2 . To the microfluidic channel  2 , a sheath liquid is introduced from a sheath liquid inlet indicated by numeral  22  in the diagram by a liquid sending pump (not shown). The sheath liquid introduced from the sheath liquid inlet  22  forms a laminar flow and is sent toward the downstream side of the microfluidic channel via bent parts  23  and  24  at which the microfluidic channel is bent by substantially 90 degrees. 
     The sample liquid supplied from the opening  31  passes through the microtube  3  and is introduced into the sheath liquid laminar flow passing through the microfluidic channel  2  from the opening  32 . By introducing the sample liquid into the sheath liquid laminar flow passing through the microfluidic channel  2  by the microtube  3  in this way, the liquids can be sent in such a way that the sample liquid laminar flow is surrounded by the sheath liquid laminar flow. 
       FIGS. 6A and 6B  are schematic diagrams showing the sheath liquid laminar flow and the sample liquid laminar flow formed in the microfluidic channel  2 . 
       FIG. 6A  is a schematic sectional view corresponding to the section along line Q-Q in the enlarged view of  FIG. 2 , and shows the opening  32  of the microtube  3  and a narrowing part  25  (to be described later) of the microfluidic channel  2  in an enlarged manner.  FIG. 6B  is a schematic sectional view corresponding to the section along line R-R in the enlarged view of  FIG. 2 , and shows the opening  32  viewed straightforward from the downstream side of the microfluidic channel  2 . 
     By introducing the sample liquid into the sheath liquid laminar flow (see symbol T in the diagram) passing through the microfluidic channel  2  by the microtube  3 , the liquids can be sent in such a way that the sample liquid laminar flow (see symbol S in the diagram) is surrounded by the sheath liquid laminar flow T as shown in  FIG. 6A . 
     In the structure shown in  FIGS. 6A and 6B , the microtube  3  is so provided that the center thereof is coaxial with the center of the microfluidic channel  2 . In this case, the sample liquid laminar flow S is introduced into the center of the sheath liquid laminar flow T passing through the microfluidic channel  2 . The formation position of the sample liquid laminar flow S in the sheath liquid laminar flow T can be set to any position through adjustment of the provision position of the microtube  3  in the microfluidic channel  2 . 
     In the case of  FIGS. 6A and 6B , the microtube  3  is provided as one tube. However, the microtube  3  is not limited thereto. For example, as shown in  FIG. 7 , it may be provided as a bundle of plural tubes (four tubes, in the diagram). If a bundle of tubes is employed as the microtube, for example, the sample liquid can be introduced from any one of microtubes  3   a ,  3   b ,  3   c , and  3   d  while solutions other than the sample liquid and the sheath liquid can be introduced from the other microtubes. The number of microtubes packed into a bundle can be two or more and is set to any number depending on the number of solutions to be introduced. At the opening of each microtube on the opposite side to the opening closer to the microfluidic channel  2 , an inlet for supplying a solution is provided and a liquid sending pump or the like is connected. 
     Specifically, e.g. the following usage will be possible. A sample liquid containing magnetically-unlabeled cells or magnetically-labeled cells is introduced from the microtube  3   a , and a solution containing a substance that can react with these cells (reactive substance) is introduced from the microtubes  3   b ,  3   c , and  3   d , for causing the reaction between the cells and the substance in the laminar flow formed in the microfluidic channel  2 . Examples of the reactive substance include an antibody that can be coupled to the cell surface and a compound that can chemically react with the cell. 
     In the case of detecting an optical characteristic of the cells in the microfluidic channel  2  by the detectors c 1  and c 2 , it is also possible to, for example, introduce a fluorescent-labeled antibody that can be coupled to the surfaces of magnetically-unlabeled cells or magnetically-labeled cells from any of the microtubes  3   b ,  3   c , and  3   d  and cause fluorescent labeling of the cells at the time of laminar flow formation by the microtube  3 , to thereby detect the characteristic based on the fluorescent substance. Furthermore, the sample liquid discharged from the sample liquid outlet  21  can be returned to the region  1  by the liquid sending controllers e 1  and e 2 . In this case, for example, it is possible that a compound is introduced from the microtube  3   b  and analysis is performed and thereafter another compound is introduced from the microtube  3   c  into the returned sample liquid and analysis is performed again. 
     (3) Narrowing of Laminar Flow Width by Narrowing Part 
     The laminar flow widths of the sample liquid and the sheath liquid set to the state in which the sample liquid laminar flow S is surrounded by the sheath liquid laminar flow T by the microtube  3  are narrowed by the narrowing part (see numeral  25  in  FIG. 2 ) formed on the downstream side in the liquid sending direction. 
     The narrowing part  25  is so formed that the inner diameter of the microfluidic channel gradually decreases in the liquid sending direction from the upstream side of the microfluidic channel toward the downstream side. Specifically, as shown in the enlarged view of  FIG. 2 , the microfluidic channel in the narrowing part  25  is gradually narrowed in the Y-axis direction along the liquid sending direction, and the narrowing part  25  is formed into a spindle shape in top view. This shape allows the narrowing part  25  to exert the function to narrow the laminar flow widths of the sheath liquid laminar flow T and the sample liquid laminar flow S in the Y-axis direction. Moreover, as shown in  FIG. 6A , the narrowing part  25  is so formed that the microfluidic channel bottom surface is an inclined surface whose height in the depth direction (Z-axis direction in the diagram) increases in the liquid sending direction. This can narrow the laminar flow widths also in the Z-axis direction. 
       FIGS. 8A and 8B  are schematic diagrams showing the sheath liquid laminar flow T and the sample liquid laminar flow S around the upstream side ( FIG. 8A ) and the downstream side ( FIG. 8B ) of the narrowing part  25 .  FIG. 8A  is a schematic sectional view corresponding to the section along line M 1 -M 1  in  FIG. 6A , and  FIG. 8B  is a schematic sectional view corresponding to the section along line M 2 -M 2  in  FIG. 6A . 
     The feature that the narrowing part  25  is so formed that the microfluidic channel diameter gradually decreases in the Y-axis and Z-axis directions along the liquid sending direction can narrow the laminar flow widths of the sheath liquid laminar flow T and the sample liquid laminar flow S shown in  FIG. 8A  in the Y-axis and Z-axis directions as shown in  FIG. 8B . In the present embodiment, simultaneously with the narrowing of the laminar flow widths of the sheath liquid laminar flow T and the sample liquid laminar flow S, both the laminar flows are biased toward the top surface of the micro-fluidic chip a (in the Z-axis positive direction in the diagram). By sending the liquids in such a way that the laminar flow widths of the sheath liquid laminar flow T and the sample liquid laminar flow S are narrowed in this manner, high detection sensitivity can be obtained in characteristic detection to be described next (details will be described later). 
     This narrowing of the laminar flow widths of the sheath liquid laminar flow T and the sample liquid laminar flow S can be achieved also by forming each of the microfluidic channel bottom surface and the top surface of the narrowing part  25  as an inclined surface. In addition, as shown in  FIG. 9A , the microfluidic channel top surface (and/or the bottom surface) of the narrowing part  25  may be formed as a multi-stage surface having a shape of stairs from the upstream side toward the downstream side. In this case, also in top view, the narrowing part  25  is formed into a shape of stairs, which narrows the microfluidic channel in a stepwise manner. If the microfluidic channel diameter of the narrowing part  25  is decreased in the Y-axis and Z-axis directions in a stepwise manner along the liquid sending direction in this manner for the narrowing of the laminar flow widths, advantages in the shaping of the narrowing part  25  are achieved. 
     As described later, the shaping of the micro-fluidic chip a, the narrowing part  25 , and so on can be carried out by wet etching or dry etching of a glass substrate layer, or nanoimprinting, injection molding, or cutting processing of a plastic substrate layer. The shaping of the narrowing part  25  is easier and particularly shaping by mechanical processing or optical molding can be carried out more easily when the narrowing part  25  has a shape of stairs than when it has an inclined surface. 
     For example, in the case of mechanical processing, a drill needs to be reciprocated many times in units of several micrometers for cutting in order to form a surface of the narrowing part  25  as an inclined surface. This process is very laborious. Furthermore, the wear of the drill easily progresses and a burr is often generated at the cut part. On the other hand, when the narrowing part  25  is formed into a shape of stairs with only several stages, cutting is easier and the wear of the drill is less and a burr is generated less readily. Also in the case of optical molding, when the narrowing part  25  is formed into a shape of stairs with only several stages, the number of times of the repetition of a CAD (Computer Aided Design) process and an optical molding process can be greatly decreased and thus the manufacturing time and the cost can be reduced. This point applies also to the case in which, as described above with  FIG. 3 , the bottom surface and so on of the region  1  is formed as a multi-stage surface with a shape of stairs in order to make magnetically-labeled cells be evenly absorbed by the surface facing the internal space of the region  1 . 
     In the case of decreasing the microfluidic channel inner diameter of the narrowing part  25  in a stepwise manner in the liquid sending direction for narrowing, it is also possible to, as shown in  FIG. 9B , decrease the microfluidic channel diameter to the inner diameter corresponding to the laminar flow widths resulting from the completion of the narrowing at one time. Also in this case, the sheath liquid laminar flow T and the sample liquid laminar flow S can be narrowed in the Y-axis and Z-axis directions without the occurrence of a turbulent flow. 
     It may also be possible to form the sheath liquid laminar flow T and the sample liquid laminar flow S whose laminar flow widths are narrowed in advance, if the microfluidic channel  2  is formed as a sufficiently-thin microfluidic channel and the sample liquid is introduced into the sheath liquid laminar flow passing through this microfluidic channel  2  by using the microtube  3  whose diameter is small. However, this case possibly causes a problem that the microparticles contained in the sample liquid get stuck in the microtube  3  due to the small diameter of the microtube  3 . 
     In the micro-fluidic chip a, the sample liquid laminar flow S and the sheath liquid laminar flow T are formed with use of the microtube  3  whose diameter is sufficiently larger than that of the microparticles contained in the sample liquid, and thereafter the laminar flow widths are narrowed by the narrowing part  25 . This configuration can eliminate the problem of the clogging of the microtube  3 . 
     The inner diameter of the microtube  3  can be accordingly set depending on the diameter of the microparticles contained in the sample liquid as the analysis subject. For example, the preferable inner diameter of the microtube  3  for analysis of cells is about 10 to 500 μm. Furthermore, the width and depth of the microfluidic channel  2  are accordingly set depending on the outer diameter of the microtube  3 , which reflects the diameter of the microparticles as the analysis subject. For example, when the inner diameter of the microtube  3  is about 10 to 500 μm, it is preferable that each of the width and depth of the microfluidic channel  2  be about 100 to 2000 μm. The sectional shapes of the microtube  3  and the microfluidic channel  2  are not limited to a circular shape but may be any shape such as an ellipsoidal shape, a quadrangular shape, or a triangular shape. 
     The laminar flow widths of the sheath liquid laminar flow T and the sample liquid laminar flow S before the narrowing by the narrowing part  25  change depending on the width and depth of the microfluidic channel  2  and the diameter of the microtube  3 . However, the laminar flow widths can be narrowed to any width by accordingly adjusting the microfluidic channel diameter of the narrowing part  25 . For example, if the microfluidic channel length of the narrowing part  25  is defined as L and the inclination angle of the microfluidic channel bottom surface thereof is defined as θ Z  in  FIG. 6A , the amount of narrowing of the laminar flow widths of the sheath liquid laminar flow T and the sample liquid laminar flow S in the narrowing part  25  is L·tan θ Z . Therefore, any amount of narrowing can be set by accordingly adjusting the microfluidic channel length L and the inclination angle θ Z . Furthermore, if the narrowing angles of the microfluidic channel side surfaces of the narrowing part  25  in the Y-axis direction are defined as θ Y1  and θ Y2  in  FIG. 2  and these angles are equalized to the angle θ Z , the sheath liquid laminar flow T and the sample liquid laminar flow S can be narrowed with isotropic width reduction as shown in  FIGS. 8A and 8B . 
     (4) Characteristic Detection by Detector 
     The sample liquid laminar flow S that is surrounded by the sheath liquid laminar flow T and has the laminar flow width narrowed by the narrowing part  25  is subjected to characteristic detection (optical characteristic detection, in this embodiment) by the detectors c 1  and c 2  (see  FIG. 1 ). The sample liquid laminar flow S contains at least one of magnetically-unlabeled cells that are separately sent while a magnetic field is formed by the magnetic field generator b or magnetically-labeled cells that are sent thereafter while the magnetic field formation by the magnetic field generator b is stopped. 
     The detector c 1  focuses laser light on the magnetically-unlabeled cells or the magnetically-labeled cells contained in the sample liquid laminar flow S sent through the microfluidic channel  2  for irradiating the cells with the laser light. The detector c 2  detects light generated from the cells due to the laser light irradiation. The light detected by the detector c 2  may be scattered light or fluorescence, such as forward scattered light, side scattered light, Rayleigh scattered light, or Mie scattered light. The light is converted to an electrical signal and output to the overall controller f (see  FIG. 1 ). Hereinafter, the position at which the characteristic detection by the detectors c 1  and c 2  is carried out in the microfluidic channel  2  will be referred to as “detection part.” 
     In the microparticle analysis device A, the laminar flow widths of the sample liquid laminar flow S and the sheath liquid laminar flow T are narrowed by the narrowing part  25 . Thus, the focus position of the laser light can be matched with the flow sending position of the cells at the detection part and the cells can be irradiated with the laser light with high accuracy. In particular, the narrowing part  25  can narrow the laminar flow width of the sample liquid laminar flow S not only in the horizontal direction of the micro-fluidic chip a (Y-axis direction in  FIG. 2 ) but also in the vertical direction (Z-axis direction in  FIGS. 6A and 6B ). Thus, the focus position of the laser light in the depth direction of the microfluidic channel  2  can be exhaustively matched with the flow sending position of the cells. Accordingly, it is possible to irradiate the cells with the laser light with high accuracy and obtain high detection sensitivity. 
     Based on the input electrical signal, the overall controller f determines an optical characteristic of the cell by employing, as a parameter, the intensity of the scattered light or fluorescence, such as forward scattered light, side scattered light, Rayleigh scattered light, or Mie scattered light. The light employed as the parameter for the determination of the optical characteristic differs depending on the microparticle as the analysis subject. Specifically, forward scattered light is employed to determine the size of the microparticle, side scattered light is employed to determine the structure, and fluorescence is employed to determine whether or not a fluorescent substance as a label on the microparticle is present. The result of the determination of the optical characteristic by the overall controller f is output to the magnetic field generator b and the liquid sending controllers e 1  and e 2 . 
     Although the detectors c 1  and c 2  are formed as an optical detection system in the present example, it is also possible to form them as an electrical detection system or a magnetic detection system. If the detectors c 1  and c 2  are formed as an electrical detection system or a magnetic detection system, an electrical characteristic or a magnetic characteristic is detected as a characteristic of the microparticle. In this case, microelectrodes are disposed as the detectors. Furthermore, e.g. any of the resistance, the capacitance, the inductance, the impedance, and the value of change in an electric field between the electrodes is measured. Alternatively, e.g. any of magnetization and a magnetic field change relating to the microparticles is measured. Two or more of these characteristics may be simultaneously measured. Also in the case of measuring an electrical or magnetic characteristic of microparticles, the measurement position of the microelectrodes can be exhaustively matched with the flow sending position of the microparticles and the characteristic can be detected with high sensitivity due to the effect of the narrowing part  25  similarly. The magnetic detectors can also determine whether or not a magnetic antibody attaches to microparticles sent in the sample flow via the internal space. Therefore, it is also possible to measure the amount of magnetically-labeled cells that should be held in the internal space originally but could not be separated and the purity and concentration of magnetically-labeled cells with respect to magnetically-unlabeled cells. 
     (5) Concentration of Sample Liquid by Sheath Liquid Discharge Path 
     In  FIG. 2 , numerals  26  and  27  denote sheath liquid discharge paths arising from branching into trifurcate paths from the microfluidic channel  2  as the center of the branching. The position of the branching from the microfluidic channel  2  into the sheath liquid discharge paths  26  and  27  is set closer to the downstream side in the liquid sending direction than the detection part of the microfluidic channel  2 . The sheath liquid discharge paths  26  and  27  function to separate only the sheath liquid laminar flow T from the sheath liquid laminar flow T and the sample liquid laminar flow S after the characteristic detection by the detectors c 1  and c 2  and send the concentrated sample liquid to the sample liquid outlet  21 . The sheath liquid separated into the sheath liquid discharge paths  26  and  27  is discharged from sheath liquid outlets indicated by numerals  261  and  271  to the outside of the micro-fluidic chip a. 
       FIGS. 10A to 10C  and  11 A to  11 C are diagrams schematically showing the sheath liquid laminar flow T and the sample liquid laminar flow S sent through the branch part for the sheath liquid discharge paths  26  and  27 . In each of  FIGS. 10A to 10C  and  11 A to  11 C, each of  10 A and  11 A is a schematic perspective view, and  10 B and  11 B and  10 C and  11 C are sectional views. In each of  FIGS. 10A to 10C  and  11 A to  11 C, each of  10 B and  11 B corresponds to the section along line N 1 -N 1  in each of  10 A and  11 A, and each of  10 C and  11 C corresponds to the section along line N 2 -N 2  in each of  10 A and  11 A. 
       FIGS. 10A to 10C  show the case in which the microfluidic channel  2  is branched into trifurcate paths at the branch part in such a way that the microfluidic channel widths of the sheath liquid discharge paths  26  and  27  in the Y-axis direction and the microfluidic channel width of the microfluidic channel  2  resulting from the branching are each ⅓ of that of the microfluidic channel  2  before the branching. In this case, of the sheath liquid laminar flow T on the upstream side of the branch part shown in  FIG. 10B , partial portions T 1  and T 2  arising from division into three partial portions in the Y-axis direction at the branch part are separated into the sheath liquid discharge paths  26  and  27 . Thus, the sheath liquid laminar flow T on the downstream side of the branch part is only a partial portion T 3  including the sample liquid laminar flow S as shown in  FIG. 10C . Due to this separation of a part of the sheath liquid laminar flow T into the sheath liquid discharge paths, the sample liquid is concentrated by a factor of about three. 
       FIGS. 11A to 11C  show the case in which the microfluidic channel widths of the sheath liquid discharge paths  26  and  27  in the Y-axis direction at the branch part are each 4/9 of that of the microfluidic channel  2  before the branching and the microfluidic channel width of the microfluidic channel  2  at the branch part is 1/9 of that of the microfluidic channel  2  before the branching. In this case, as shown in  FIG. 11C , the sheath liquid laminar flow T on the downstream side of the branch part is only a partial portion T 3  that corresponds to a 1/9 portion arising from division into nine partial portions in the Y-axis direction and includes the sample liquid laminar flow S. Thus, the sample liquid is concentrated by a factor of about nine. 
     The rate of the separation of the sheath liquid laminar flow T into the sheath liquid discharge paths  26  and  27 , i.e. the concentration rate of the sample liquid, can be set to any rate through adjustment of the ratio of the microfluidic channel widths of the sheath liquid discharge paths  26  and  27  to the microfluidic channel width of the microfluidic channel  2  at the branch part. The ratio of the microfluidic channel width between the sheath liquid discharge paths  26  and  27  and the microfluidic channel  2  at the branch part is so adjusted that the desired concentration rate is achieved, in consideration of the width and depth of the microfluidic channel  2 , the inner diameter of the microtube  3 , and so on at the time of laminar flow formation. In addition, the provision position of the microtube  3  in the microfluidic channel  2  also needs to be taken into consideration so that the partial portion T 3  including the sample liquid laminar flow S may be sent toward the downstream side of the microfluidic channel  2 . 
     The number of branch parts of the microfluidic channel  2  is not limited to one but may be two or more.  FIG. 12  shows the case in which two branch parts for the sheath liquid discharge paths are provided on the microfluidic channel  2 . In the structure shown in the diagram, the branch part shown in  FIG. 11A  is connected to the microfluidic channel  2  on the downstream side of the branch part for the sheath liquid discharge paths  26  and  27  shown in  FIG. 10A . In this example, the sample liquid can be concentrated by a factor of about three at the first branch part, and can be further concentrated by a factor of about nine at the next branch part. Accordingly, the sample liquid can be sent to the sample liquid outlet  21  after being concentrated by a factor of about 27. 
     (6) Collection or Return of Sample Liquid by Liquid Sending Controller 
     The sample liquid that has passed through the branch part for the sheath liquid discharge paths and is discharged from the sample liquid outlet  21  to the outside of the micro-fluidic chip a is sent to either the collection tank d or the sample liquid inlet  11  selectively by the liquid sending controllers e 1  and e 2 . 
     A signal is output from the overall controller f to the liquid sending controllers e 1  and e 2  (see  FIG. 1 ). In response to this output, the liquid sending controllers e 1  and e 2  carry out control of switching of the sending destination of the sample liquid to either the collection tank d or the sample liquid inlet  11 . The control by the liquid sending controllers e 1  and e 2  is carried out in linkage with the control by the magnetic field generator b, which forms a magnetic field or stops magnetic field formation in response to the output from the overall controller f. The details of the linked control of the liquid sending controllers e 1  and e 2  and the magnetic field generator b by the overall controller f will be described in the following chapter “microparticle analysis method.” 
     3. Microparticle Analysis Method 
     A microparticle analysis method according to the embodiment will be described below. The following description will deal with an example in which analysis and sorting of cells by the microparticle analysis device A are performed with use of a sample liquid containing magnetically-labeled cells as “magnetic microparticles” and magnetically-unlabeled cells as “non-magnetic microparticles.” The cells as the sorting subject may be either the magnetically-unlabeled cells or the magnetically-labeled cells. The case of sorting the magnetically-unlabeled cells and the case of sorting the magnetically-labeled cells will be described below in turn. 
     (1) Sorting of Magnetically-Unlabeled Cell (Negative Selection) 
     (1-1) Cell Labeling 
     Initially, a method in which the magnetically-unlabeled cells are the sorting subject (hereinafter, referred to as “negative selection method”) will be described below with reference to  FIG. 13  and  FIG. 1 . In the negative selection method, of the cells contained in the sample liquid, the cells that are not the sorting subject (non-target cells) are magnetically labeled by using a magnetic bead antibody (see a step S 1  in  FIG. 13  and “Table 1”). On the other hand, the cells that are the sorting subject (target cells) are labeled with a substance that can be detected by the detectors c 1  and c 2 . For example, if the detectors c 1  and c 2  are formed as an optical detection system, the target cells are fluorescent-labeled by using a fluorescent-labeled antibody. If the detectors c 1  and c 2  are an electrical or magnetic detector, the target cells are electrically or magnetically labeled. 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 &lt;Negative Selection Method 1&gt; 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   
                 target cell: e.g. fluorescent-labeled 
               
               
                   
                 non-target cell: magnetically labeled 
               
               
                   
                   
               
            
           
         
       
     
     (1-2) Cell Separation and Characteristic Detection 
     The sample liquid containing the labeled cells is introduced from the sample liquid inlet  11  of the micro-fluidic chip a into the region  1  (see a step S 2  in  FIG. 13 ). A magnetic field by the magnetic field generator b is formed in the internal space of the region  1 , and the target cells and the non-target cells contained in the sample liquid introduced into the region  1  are sent in the magnetic space generated by the magnetic field generator b via the turn-back parts  12  and  13  (see  FIG. 1 ). 
     At this time, magnetic acting force works between the magnetically-labeled non-target cells and the magnetic field. Due to this magnetic acting force, the non-target cells are so held in the region  1  as to remain in the internal space of the region  1  against the liquid sending pressure of the sample liquid or be absorbed by the surface facing the internal space of the region  1 . As a result, the cells contained in the sample liquid are separated into the non-target cells, which do not pass through the magnetic space generated by the magnetic field generator b, and the magnetically-unlabeled target cells, which pass through the magnetic space, and the sample liquid containing only the target cells is introduced from the end part of the region  1  via the microtube  3  into the microfluidic channel  2 . 
     The sample liquid introduced into the microfluidic channel  2  is turned to a laminar flow surrounded by a sheath liquid laminar flow and its laminar flow width is narrowed by the narrowing part  25 . Thereafter, the sample liquid laminar flow is subjected to characteristic detection by the detectors c 1  and c 2 . The sample liquid laminar flow sent to the detection part contains the target cells, which are fluorescent-labeled for example. In addition to the target cells, a part of the non-target cells that are not separated but introduced into the microfluidic channel  2  due to failure in sufficient working of the magnetic acting force in the region  1  is also contained in the sample liquid laminar flow possibly. About these cells, the detectors c 1  and c 2  carry out characteristic detection based on e.g. fluorescence generated from the fluorescent substance labeled on the target cells. Furthermore, the detectors c 1  and c 2  convert the detection result to an electrical signal and output the signal to the overall controller f. 
     (1-3) Characteristic Determination and Collection or Return 
     (1-3-1) Characteristic Determination 
     The overall controller f carries out characteristic determination about the cells detected by the detectors c 1  and c 2  based on the input electrical signal (see a step S 3  in  FIG. 13 ). The characteristic determination is carried out by performing gating of the detected cells by use of the intensity of the fluorescence from the fluorescent substance, the scattered light intensity, or the like as a parameter. 
     (1-3-2) Collection 
     If the cells as a predetermined ratio of the detected cells fall within the gating for the cells as the sorting subject and it is determined that the ratio of the target cells to all of the cells passing through the microfluidic channel  2  is equal to or higher than a predetermined value, the overall controller f outputs a determination result “Yes” to the liquid sending controllers e 1  and e 2 . In response to this output, the liquid sending controllers e 1  and e 2  send the sample liquid discharged from the sample liquid outlet  21  to the collection tank d (see a step S 4  in  FIG. 13 ). Thus, the sample liquid containing the target cells at the predetermined ratio can be collected in the collection tank d. At this time, dilution of the sample liquid to be collected is prevented by the sheath liquid discharge paths  26  and  27  (see  FIGS. 10A to 10C  and so on). 
     (1-3-3) Return 
     On the other hand, if the ratio of the cells that fall within the gating for the cells as the sorting subject to the cells detected by the detectors c 1  and c 2  is lower than the predetermined value and it is determined that a large number of non-target cells pass through the microfluidic channel  2 , the overall controller f outputs a determination result “No” to the liquid sending controllers e 1  and e 2 . In response to this output, the liquid sending controllers e 1  and e 2  introduce the sample liquid discharged from the sample liquid outlet  21  to the sample liquid inlet  11  and return it into the region  1  (see a step S 5  in  FIG. 13 ). For the returned sample liquid, the step S 2  of “Separation and Characteristic Determination” is carried out again. Dilution of the sample liquid to be returned is prevented by the sheath liquid discharge paths  26  and  27  (see  FIGS. 10A to 10C  and so on). 
     The steps of the characteristic determination S 3 , the return S 5 , and the separation and characteristic detection S 2  are repeated until the cells as a predetermined ratio of the detected cells fall within the gating for the cells as the sorting subject and it is determined that the ratio of the target cells to all of the cells passing through the microfluidic channel  2  is equal to or higher than the predetermined value. At the timing when the ratio of the target cells has become equal to or higher than the predetermined value, the sample liquid is introduced into the collection tank d, so that the sample liquid containing the target cells at the predetermined ratio is collected. 
     As above, the sample liquid containing the target cells at the predetermined ratio can be collected by magnetically labeling the non-target cells and carrying out the separation between the target cells and the non-target cells in the region  1  until the ratio of the target cells to all of the cells passing through the microfluidic channel  2  becomes equal to or higher than the predetermined value. In this method, the cells do not need to be sorted into the sorting microfluidic channels one by one by electrodes or the like differently from a method in a related-art microparticle sorting device. Thus, the analysis time is shorter and the target cells can be efficiently sorted. In addition, the target cells with high purity can be collected into the collection tank d by repeating the steps of the characteristic determination S 3 , the return  55 , and the separation and characteristic determination S 2  until the ratio of the target cells to all of the cells passing through the microfluidic channel  2  becomes the desired value. 
     It is also possible to, in this negative selection method, carry out the step S 1  of the cell labeling with the combination shown in “Table 2.” 
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 &lt;Negative Selection Method 2&gt; 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   
                 target cell: not labeled 
               
               
                   
                 non-target cell: magnetically labeled and e.g. fluorescent-labeled 
               
               
                   
                   
               
            
           
         
       
     
     (2) Sorting of Magnetically-Labeled Cell (Positive Selection) 
     (2-1) Cell Labeling 
     A method in which the magnetically-labeled cells are the sorting subject (hereinafter, referred to as “positive selection method”) will be described below with reference to  FIG. 14  and  FIG. 1 . In the positive selection method, for the target cells among the cells contained in the sample liquid, both magnetic labeling by use of a magnetic bead antibody and labeling with a substance that can be detected by the detectors c 1  and c 2  are carried out (see a step S 1  in  FIG. 14  and “Table 3”). On the other hand, the non-target cells are not labeled. 
     
       
         
           
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 &lt;Positive Selection Method 1&gt; 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   
                 target cell: magnetically labeled and e.g. fluorescent-labeled 
               
               
                   
                 non-target cell: not labeled 
               
               
                   
                   
               
            
           
         
       
     
     (2-2) Cell Separation and Characteristic Detection 
     The sample liquid containing the labeled cells is introduced from the sample liquid inlet  11  of the micro-fluidic chip a into the region  1  (see a step S 2  in  FIG. 14 ). A magnetic field by the magnetic field generator b is formed in the internal space of the region  1 , and the target cells and the non-target cells contained in the sample liquid introduced into the region  1  are sent in the magnetic space generated by the magnetic field generator b via the turn-back parts  12  and  13 . 
     At this time, magnetic acting force works between the magnetically-labeled target cells and the magnetic field. Due to this magnetic acting force, the target cells are so held in the region  1  as to remain in the internal space of the region  1  against the liquid sending pressure of the sample liquid or be absorbed by the surface facing the internal space of the region  1 . As a result, the cells contained in the sample liquid are separated into the target cells, which do not pass through the magnetic space generated by the magnetic field generator b, and the magnetically-unlabeled non-target cells, which pass through the magnetic space, and the sample liquid containing only the non-target cells is introduced from the end part of the region  1  via the microtube  3  into the microfluidic channel  2 . 
     The sample liquid introduced into the microfluidic channel  2  is turned to a laminar flow surrounded by a sheath liquid laminar flow and its laminar flow width is narrowed by the narrowing part  25 . Thereafter, the sample liquid laminar flow is subjected to characteristic detection by the detectors c 1  and c 2 . The sample liquid laminar flow sent to the detection part contains the non-target cells, which are not labeled. In addition to the non-target cells, a part of the target cells that are not separated but introduced into the microfluidic channel  2  due to failure in sufficient working of the magnetic acting force in the region  1  is also contained in the sample liquid laminar flow possibly. About these cells, the detectors c 1  and c 2  carry out characteristic detection based on e.g. fluorescence generated from the fluorescent substance labeled on the target cells. Furthermore, the detectors c 1  and c 2  convert the detection result to an electrical signal and output the signal to the overall controller f. 
     (2-3) Characteristic Determination and Collection or Return 
     (2-3-1) Characteristic Determination 
     The overall controller f carries out characteristic determination about the cells detected by the detectors c 1  and c 2  based on the input electrical signal (see a step S 3  in  FIG. 14 ). The characteristic determination is carried out by performing gating of the detected cells by use of the intensity of the fluorescence from the fluorescent substance or the scattered light intensity as a parameter. 
     (2-3-2) Collection 
     If the ratio of the cells that fall within the gating for the cells as the sorting subject to the detected cells is lower than a predetermined value and it is determined that the number of target cells that are not separated but pass through the microfluidic channel  2  is sufficiently small, the overall controller f outputs a determination result “Yes” to the liquid sending controllers e 1  and e 2 . In response to this output, the liquid sending controllers e 1  and e 2  send the sample liquid discharged from the sample liquid outlet  21  to a collection tank d 1  (see a step S 4  in  FIG. 14 ). Thus, the sample liquid containing the non-target cells is collected in the collection tank d 1 . The non-target cells collected in the collection tank d 1  may be discarded as unnecessary cells. 
     Subsequently, the overall controller f outputs the determination result “Yes” to the magnetic field generator b to thereby stop the magnetic field formation. Due to this operation, the holding of the target cells in the region  1  is released, so that the target cells are sent to the microfluidic channel  2 . Simultaneously, the overall controller f outputs the determination result also to the liquid sending controllers e 1  and e 2  to thereby introduce the sample liquid discharged from the sample liquid outlet  21  into a collection tank d 2  (see a step S 5  in  FIG. 14 ). Thus, the sample liquid containing the target cells at the predetermined ratio can be collected in the collection tank d 2 . At this time, dilution of the sample liquid to be collected is prevented by the sheath liquid discharge paths  26  and  27  (see  FIGS. 10A to 10C  and so on). 
     The following operation may be carried out in the step S 5  of the collection of the target cells. Specifically, after the magnetic field formation is stopped, the characteristic detection by the detectors c 1  and c 2  is carried out for the target cells sent to the microfluidic channel  2 , and it is confirmed that the cells as a predetermined ratio of the detected cells fall within the gating for the target cells. 
     (2-3-3) Return 
     On the other hand, if the ratio of the cells that fall within the gating for the cells as the sorting subject to the cells detected by the detectors c 1  and c 2  is equal to or higher than the predetermined value and it is determined that a large number of target cells pass through the microfluidic channel  2 , the overall controller f outputs a determination result “No” to the liquid sending controllers e 1  and e 2 . In response to this output, the liquid sending controllers e 1  and e 2  introduce the sample liquid discharged from the sample liquid outlet  21  to the sample liquid inlet  11  and return it into the region  1  (see a step S 6  in  FIG. 14 ). For the returned sample liquid, the step S 2  of “Separation and Characteristic Determination” is carried out again. Dilution of the sample liquid to be returned is prevented by the sheath liquid discharge paths  26  and  27  (see  FIGS. 10A to 10C  and so on). 
     The steps of the characteristic determination S 3 , the return S 6 , and the separation and characteristic detection S 2  are repeated until the ratio of the cells that fall within the gating for the cells as the sorting subject is lower than the predetermined value and it is determined that the number of target cells that are not separated but pass through the microfluidic channel  2  is sufficiently small. At the timing when the ratio of the target cells has become lower than the predetermined value, the sample liquid containing the non-target cells is introduced into the collection tank d 1  first. Subsequently, after the magnetic field formation by the magnetic field generator b is stopped, the sample liquid containing the target cells is introduced into the collection tank d 2 , so that the sample liquid containing the target cells at the predetermined ratio is collected. 
     As above, the sample liquid containing the target cells at the predetermined ratio can be collected also by magnetically labeling the target cells and carrying out the separation between the target cells and the non-target cells in the region  1  until the ratio of the target cells to all of the cells passing through the microfluidic channel  2  becomes lower than the predetermined value. 
     It is also possible to, in this positive selection method, carry out the step S 1  of the cell labeling with the combination shown in “Table 4.” 
     
       
         
           
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 &lt;Positive Selection Method 2&gt; 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   
                 target cell: magnetically labeled 
               
               
                   
                 non-target cell: e.g. fluorescent-labeled 
               
               
                   
                   
               
            
           
         
       
     
     4. Micro-fluidic Chip 
     The micro-fluidic chip a for microparticle analysis according to the embodiment has a configuration including the region  1 , the microfluidic channel  2 , the microtube  3 , and so on, which are described above for the microparticle analysis device A. The micro-fluidic chip a may include the magnetic field generator b for forming a magnetic field in the internal space of the region  1 . In this case, the magnetic field generator b is provided by fabricating it as an electromagnetic in the substrate of the micro-fluidic chip a or stacking an electromagnetic on the substrate. Details of the respective components and operation of the micro-fluidic chip a are as described above, and therefore description thereof is omitted. 
     Glass or any of various kinds of plastic (PP, PC, COP, PDMS) can be used as the material of the micro-fluidic chip a. In the case of detecting an optical characteristic of microparticles by the detectors c 1  and c 2 , the micro-fluidic chip a is formed by using a material that has optical transparency, low autofluorescence, small wavelength dispersion, and few optical errors. Furthermore, in this case, it is preferable that a so-called hard coat layer used for an optical disk is stacked on the surface of the micro-fluidic chip a. If dirt such as a fingerprint is attached to the surface of the micro-fluidic chip a, possibly the amount of light passing therethrough is decreased and the optical analysis accuracy is lowered. In particular, if dirt is attached to the surface of the detection part at which the optical characteristic detection by the detectors c 1  and c 2  is carried out in the microfluidic channel  2 , accurate analysis possibly fails. By stacking a hard coat layer excellent in the transparency and the dirt repellency on the surface of the micro-fluidic chip a, the lowering of the analysis accuracy due to such dirt can be prevented. 
     The hard coat layer can be formed by using a generally-used hard coat agent. For example, it can be formed by using a UV-curing hard coat agent to which an agent for preventing fingerprint attachment, such as a fluorine-based or silicon-based dirt repellent additive agent, is added. Japanese Patent Laid-open No. 2003-157579 discloses, as the hard coat agent, (P) an active-energy-beam-curing composition including the following substances: (A) a polyfunctional compound having at least two polymerizable functional groups that can be polymerized by an active energy beam, (B) modified colloidal silica that has an average particle diameter of 1 to 200 nm and has the surface modified with a mercaptosilane compound in which an organic group having a mercapto group and a hydrolyzable group or a hydroxyl group are coupled to a silicon atom, and (C) a photopolymerization initiator. 
     For preventing dirt attachment to the surface of the detection part in the microfluidic channel  2 , it is also effective to, as shown in  FIGS. 15A and 15B , recess the surface of the detection part (see symbol F in the diagram) relative to the surface of the other part of the micro-fluidic chip a to thereby prevent contact of a fingertip and dirt to the surface of the detection part.  FIG. 15A  shows the case in which a dimple is formed at the part corresponding to the detection part on the surface of the micro-fluidic chip a.  FIG. 15B  shows the case in which a groove including the part corresponding to the detection part is formed on the surface of the micro-fluidic chip a. 
     As the microtube  3 , a tube composed of a metal, glass, ceramics, or any of various kinds of plastic (PP, PC, COP, PDMS) can be employed. As for a silica tube, tubes each having an inner diameter of several tens to several hundreds of micrometers are commercially available. Therefore, the silica tube can be favorably employed as the microtube  3  because a tube having a suitable diameter can be accordingly utilized. The silica tube has high heat resistance, and therefore thermal deformation hardly occurs even in thermocompression bonding of the substrate layer. 
     The shaping of the region  1 , the microfluidic channel  2 , and so on provided on the micro-fluidic chip a can be carried out by wet etching or dry etching of a glass substrate layer, or nanoimprinting, injection molding, or cutting processing of a plastic substrate layer. The microtube  3  is disposed on the substrate layer in which the region  1  and so on is shaped in such a manner as to be fitted into a groove formed to allow communication between the end part of the region  1  and the microfluidic channel  2 . After the microtube is disposed, the substrate layer in which the region  1  and so on is shaped is covered and sealed by a substrate layer composed of the same material or a different material, so that the micro-fluidic chip a is formed. 
     The bonding of the substrate layers can be carried out e.g. by any of the following publicly-known methods: heat fusion, an adhesive, anodic bonding, bonding by use of an adhesive sheet, plasma-activated bonding, and ultrasonic bonding. The groove into which the microtube  3  is fitted is sealed by an adhesive for fixing the microtube  3  to the substrate layer. Due to the sealing of the groove, the communication between the region  1  and the microfluidic channel  2  is achieved only via the microtube  3 . This allows the sample liquid sent to the end part of the region  1  to be introduced into the microfluidic channel  2  by the microtube  3 . 
     It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.