Abstract:
Disclosed is a microfluidic structure and a microfluidic device comprising the microfluidic device, which is suitable for detecting a target material. The microfluidic structure mixes the beads, biological samples, and the detection probe to react and washes and separates the beads after the reaction.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This application is a continuation application of U.S. application Ser. No. 12/851,819, filed Aug. 6, 2010 (now allowed), which is a continuation in part of Ser. No. 11/850,129, filed Sep. 5, 2007 (U.S. Pat. No. 7,776,267), which claims the benefit of Korean Patent Application Nos. 10-2006-0085372, filed on Sep. 5, 2006 and 10-2007-0003401, filed Jan. 11, 2007, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a centrifugal force-based microfluidic device which controls fluid flow by centrifugal force in a microfluidic structure prepared on a body of revolution. The present invention also relates to a centrifugal force-based microfluidic device for detecting target protein from a biological sample. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, a microfluidic structure constituting a microfluidic device may include a chamber, a channel, a valve, and a plurality of functional units, wherein the chamber stores a small amount of fluid, the fluid flows through the channel, the valve controls fluid flow, and the functional units receive the fluid to perform certain functions. This microfluidic structure, which is formed on a chip-type substrate for conducting experiments including a biochemical reaction, is referred to as a bio-chip. In particular, a device manufactured to perform several steps of processes and operations in one chip is referred to as a lab-on-a chip. 
         [0006]    In order to transfer fluid in the microfluidic structure, driving pressure is needed. Capillary pressure and pressure by an additional pump may be used as the driving pressure. Recently, centrifugal force-based microfluidic devices in which microfluidic structures are disposed on a compact disk (CD)-type body of revolution have been suggested. Such a device is referred to as a Lab CD. However, in this case, since a body of revolution is not fixed onto a frame and thus moves, it is difficult to control fluid flow and temperature of the functional units in the body of revolution. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a centrifugal force-based microfluidic device including a microfluidic structure and a microfluidic system including the microfluidic device and devices to operate the microfluidic device. The microfluidic device can detect presence of target protein, through a series of processes performed in the microfluidic structure such as moving biomaterial samples using centrifugal force when the biomaterial samples such as blood are injected into the microfluidic structures prepared on a body of revolution. 
         [0008]    According to an aspect of the present invention, there is provided a centrifugal force-based microfluidic device for biomolecule detection, including: a body of revolution a body of revolution having a rotation center and a circumference; a microfluidic structure disposed in the body of revolution comprising a plurality of chambers, channels connecting the chambers to each other and forming a path of fluid flow between the chambers, and valves disposed in the channels to control the fluid flow between the chambers, the microfluidic structure transmitting fluid using centrifugal force due to rotation of the body of revolution, wherein one of the plurality of chambers receives a fluid biological sample beads disposed in the microfluidic structure, the beads having a first probe to capture a target molecule from a fluid biological sample, the first probe selectively binds to the target molecule; and a second probe disposed in the microfluidic structure and selectively binding to the target molecule, and which comprises a substance emitting an optical signal, wherein the microfluidic structure mixes the beads, the biological sample, and the second probe to bring them into contact with each other to produce a bead-target molecule-second probe complex, if the fluid biological sample contains the target molecule; and separates the bead-target molecule-second probe complex. 
         [0009]    The microfluidic device may further include a substrate solution contained in the microfluidic structure, wherein the substrate solution is brought into contact with the bead-target molecule-second probe complex to generate an optical signal. That is, the optical signal emission materials may generate an optical signal independently such as fluorescence and color or may generate an optical signal by a reaction of a substrate and an enzyme included in the substrate solution. 
         [0010]    The valves may be selected from the group consisting of a capillary valve, a hydrophobic valve, a mechanical valve, and a phase-change valve. Here, each of the valves may include a phase-change valve, the phase-change valve which comprises a valve plug in which heat generating particles and phase-change materials are included, wherein the heat generating particles absorb electromagnetic waves from an external energy source and the phase-change material is melted by heat generated from the heat generating particles, and controls the fluid flow in the channels, by opening or closing the channels. The phase-change valve may include an opening valve which is disposed to close the channel at an initial stage, wherein the valve plug is melted by heat generated by the heat generating particles, thereby opening the channel. The phase-change valve may include a closing valve which is disposed in a valve chamber connected to the channel which is opened at an initial stage, wherein the valve plug is melted and expanded by heat generated by the heat generation particles to flow into the channel, thereby closing the channel. 
         [0011]    According to another aspect of the present invention, there is provided a microfluidic device including: a body of revolution having a rotation center and a circumference; a microfluidic structure disposed in the body of revolution comprising a plurality of chambers, channels connecting the chambers to each other and forming a path of fluid flow between the chambers, and valves disposed in the channels to control the fluid flow, the microfluidic structures transmitting fluid using centrifugal force due to rotation of the body of revolution, wherein one of the plurality of chambers receives a fluid biological sample; beads having a first probe to capture a target molecule from a fluid biological sample, the first probe selectively binds to the target molecule; and a second probe selectively binding to the target molecule and including a substance emitting an optical signal, wherein the microfluidic structure comprises: a sample chamber which receives a sample solution containing the fluid biological sample; a buffer chamber which receives a buffer solution; a bead chamber which receives a bead solution containing the beads; a mixing chamber which is fluid connected to the sample chamber, the buffer chamber, and the bead chamber through the channel; which receives a solution containing the second probe; which comprises an inlet to receive a fluid and an outlet to discharge the fluid, the outlet being disposed with a greater distance from the rotation center of the body of revolution than the inlet, and the outlet being provided with a valve to control a flow of the fluid discharged from the mixing chamber; and in which the sample and the beads are brought into contact with each other to produce a bead-target molecule-second probe complex, if the fluid biological sample contains the target molecule; and separates the bead-target molecule-second probe complex; a waste chamber which is fluid connected to the outlet of the mixing chamber through a channel, the waste chamber receiving the fluid discharged from the mixing chamber by changes of phases of a valve; and an optical signal emission chamber connected to the outlet of the mixing chamber through a channel, in which a substrate solution is brought into contact with the bead-target molecule-second probe complex to generate an optical signal. 
         [0012]    The mixing chamber may be disposed with a greater distance from the center of the body of revolution than the sample chamber, the buffer chamber, and the bead chamber and is disposed with a smaller distance from the center of the body of revolution than the waste chamber and the optical signal emission chamber. The channel connecting the mixing chamber and the waste chamber may be connected such that a space can be provided in the channel where the beads can be collected between a part connected to the channel and the outlet of the mixing chamber. 
         [0013]    The channel connecting the mixing chamber and the waste chamber may include a valve which can open and close, In this case, the channel connecting the mixing chamber and the waste chamber can open and close at least two times. 
         [0014]    The channels connecting the buffer chamber and the mixing chamber may be connected corresponding to various levels of the fluid in the buffer chamber and each channel may include valves, each of which is operated, independently. 
         [0015]    In this case, as a number of water levels, a number of openings and closings of the channel connecting the mixing chamber and the waste chamber is determined. 
         [0016]    The microfluidic device may further include magnetic field forming materials which are disposed at a location which allows the optical signal emission chamber to draw and concentrate the magnetic beads contained in the optical signal emission chamber by magnetic force of the magnetic field forming materials. 
         [0017]    In addition, the microfluidic device may further include a centrifuging unit connected to a channel which connects the sample chamber and the mixing chamber, the centrifuging unit centrifuging the fluid biological sample contained in the sample chamber, prior to discharging the fluid biological sample into the mixing chamber. 
         [0018]    In the microfluidic device, the optical signal emission chamber receives the substrate solution, which is brought into contact with the bead-target molecule-second probe complex to generate an optical signal. 
         [0019]    Each of the valves may be selected from the group consisting of a capillary valve, a hydrophobic valve, a mechanical valve, and a phase-change valve. 
         [0020]    Here, each of the valves may include a phase-change valve, the phase-change valve comprising a valve plug in which heat generating particles and phase-change materials are included, wherein the heat generating particles absorb electromagnetic waves from an external device and the phase-change material is melted by heat generated from the heat generating particles, and controlling fluid flow, wherein the fluid passes through the channels, according to a position of the valve plug in the channels. 
         [0021]    The phase-change valve may include an opening valve which is disposed to close the channel at an initial stage, wherein the valve plug prepared after the valve plug is melted by heat generated by the heat generation particles, thereby opening the channel. The phase-change valve may include a closing valve which is disposed in a valve chamber connected to the channel which is opened at an initial stage, wherein the valve plug is melted and expanded by heat generated by the heat generation particles, thereby closing the channel. 
         [0022]    According to another aspect of the present invention, there is provided a microfluidic system including: a centrifugal force-based microfluidic device as described above; a rotation operating unit which rotates the body of revolution of the microfluidic device; and a light detecting unit which detects an optical signal of the microfluidic device. 
         [0023]    The microfluidic system may further include a substrate solution contained in the microfluidic structure, wherein the substrate solution is bought into contact with the bead-target-molecule-second probe complex to generate an optical signal. 
         [0024]    Each of the valves may be selected from the group consisting of a capillary valve, a hydrophobic valve, a mechanical valve, and a phase-change valve. 
         [0025]    The microfluidic system may further include an external energy source which irradiates electromagnetic waves onto a region selected on the microfluidic device. 
         [0026]    Here each of the valves may include a phase-change valve which comprises a valve plug in which heat generating particles and phase-change materials are included, wherein the heat generating particles absorb an electromagnetic wave from an external device and the phase-change material is melted by heat generated from the heat generating particles, and controls the flow of fluid in the channels by opening or closing the channels. 
         [0027]    According to another aspect of the present invention, there is provided a microfluidic system including: the microfluidic device described above, a rotation operating unit which rotates the body of revolution of the microfluidic device; and a light detecting unit which detects an optical signal of the microfluidic device. 
         [0028]    The microfluidic system may further include an external energy source which irradiates electromagnetic waves onto a region of the microfluidic device. Here, each of the valves may include a phase-change valve, which comprises a valve plug in which heat generating particles and phase-change materials are included, wherein the heat generating particles absorb an electromagnetic wave from an external energy source and the phase-change material is melted by heat generated from the heat generating particles, and controls the flow of fluid in the channels, by opening or closing the channels. 
         [0029]    According to another aspect of the present invention, there is provided a microfluidic system comprising: a body of revolution provided with a rotational axis and a circumference; a microfluidic structure disposed in the body of revolution comprising a plurality of chambers, channels connecting the chambers to each other and valves disposed in the channels to control fluid flow, the microfluidic structures transmitting fluid using centrifugal force due to rotation of the body of revolution, wherein one of the plurality of chambers receives a fluid biological sample; magnetic beads included in any one of the chambers which selectively capture a target molecule from the fluid biological sample flowing into the corresponding chamber; a revolution plate formed to be integral with the body of revolution on one side of the body of the revolution, the revolution plate being provided with a rotation axis and a circumference which each correspond to the rotational axis and the circumference of the body of the revolution; a guide rail disposed in the revolution plate which has a form of a path to connect various positions having each different distance from the rotational axis of the revolution plate and includes a magnet therein so as to move the magnet; and an external magnet disposed outside of the revolution plate to be temporarily fixed to at least a specific position corresponding to any one of the positions in the guide rail, wherein the microfluidic structure includes: a sample chamber which receives a sample solution; a buffer chamber which receives a buffer solution; a bead chamber which receives a bead solution containing the beads; a mixing chamber containing which is fluid connected to the sample chamber, the buffer chamber, and the bead chamber through the channel; which receives a solution containing the second probe; which comprises an inlet to receive a fluid and an outlet to discharge the fluid, the outlet being disposed with a greater distance from the rotation center of the body of revolution than the inlet, and the outlet being provided with a valve to control a flow of the fluid discharged from the mixing chamber; and in which the sample and the beads are brought into contact with each other to produce a bead-target molecule-second probe complex, if the fluid biological sample contains the target molecule; and separates the bead-target molecule-second probe complex; a waste chamber which is fluid connected to the outlet of the mixing chamber through a channel, the waste chamber receiving the fluid discharged from the mixing chamber by changes of phases of a valve; and an optical signal emission chamber connected to the outlet of the mixing chamber through a channel, in which a substrate solution is brought into contact with the bead-target molecule-second probe complex to generate an optical signal. 
         [0030]    In another embodiment of the invention, there is provided microfluidic device comprising: a body of revolution having a rotation center and a circumference; a microfluidic structure disposed in the body of revolution comprising a plurality of chambers, channels connecting the chambers to each other and forming a path of fluid flow between the chambers, and valves disposed in the channels to control the fluid flow, the microfluidic structures transmitting fluid using centrifugal force due to rotation of the body of revolution, wherein one of the plurality of chambers receives a fluid biological sample; beads having a first probe to capture a target molecule from a fluid biological sample, the first probe selectively binds to the target molecule; and a conjugate which is composed of a second probe selectively binding to the target molecule and including a label, wherein the microfluidic structure comprises: a sample chamber which contains a sample solution containing the fluid biological sample; a buffer chamber which contains a buffer solution; a substrate solution chamber which contains a substance to generate detectable optical signal when it contracts with the conjugate; a mixing chamber which is interconnected to the sample chamber, and the buffer chamber through the channel; which holds the beads and receives a solution containing the second probe and at least one type of the target molecule; which comprises an inlet to receive a fluid and an outlet to discharge the fluid, the outlet being disposed with a greater distance from the rotation center of the body of revolution than the inlet, and the outlet being provided with a valve to control a flow of the fluid discharged from the mixing chamber; in which the sample and the first probe are brought into contact with each other and the second probe to produce a first probe-target molecule-second probe complex, if the fluid biological sample contains the target molecule; and separates the first probe-target molecule-second probe complex and in which a substrate solution is brought into contact with the first probe-target molecule-second probe complex to generate an optical signal; a waste chamber which is fluid connected to the outlet of the mixing chamber through a channel, the waste chamber receiving the fluid discharged from the mixing chamber by changes of phases of a valve; and an optical signal measuring chamber connected to the outlet of the mixing chamber through a channel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    The file of this patent contains at least one drawing executed in color. Copies of this patent with color drawing(s) will be provided by the Patent and Trademark Office upon request and payment of the necessary fee. 
           [0032]    The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
           [0033]      FIG. 1  is a plan view schematically illustrating a microfluidic device according to an embodiment of the present invention; 
           [0034]      FIG. 2  is an enlarged view illustrating a part of the microfluidic device of  FIG. 1 , according to an embodiment of the present invention; 
           [0035]      FIG. 3  is a plan view schematically illustrating a microfluidic device according to another embodiment of the present invention; 
           [0036]      FIG. 4  is a plan view schematically illustrating a microfluidic device according to another embodiment of the present invention; 
           [0037]      FIG. 5  is a plan view schematically illustrating a microfluidic device according to another embodiment of the present invention; 
           [0038]      FIG. 6  is a cross-sectional view of an opening valve which controls fluid flow in a microfluidic device according to an embodiment of the present invention; 
           [0039]      FIG. 7  is a plan view of a closing valve which controls fluid flow in a microfluidic device according to an embodiment of the present invention; 
           [0040]      FIG. 8  is a cross-sectional view of the closing valve of  FIG. 7  according to an embodiment of the present invention; 
           [0041]      FIG. 9  is a detailed perspective view of the microfluidic device of  FIG. 5  according to an embodiment of the present invention; 
           [0042]      FIG. 10  is a perspective view schematically illustrating a microfluidic system according to an embodiment of the present invention; 
           [0043]      FIG. 11  is a series of schematic diagrams illustrating a process of an immunoassay using beads performed in a microfluidic device according to an embodiment of the present invention; 
           [0044]      FIGS. 12A through 12P  are photographic images illustrating a process of detecting Hepatitis virus B surface antibody (Anti-HBs) using a microfluidic device according to an embodiment of the present invention; and 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0045]    Hereinafter, the present invention will be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. 
         [0046]      FIG. 1  is a plan view schematically illustrating a microfluidic device according to an embodiment of the present invention. Referring to  FIG. 1 , the microfluidic device includes a body of revolution  100  and one or more microfluidic structures  101  disposed on the body of revolution  100 . According to the current embodiment of the present invention, the body of revolution  100  may be a disk-shaped platform. The platform can be easily manufactured and formed of plastic materials such as an acryl and PDMS and the surface of the platform is deactivated. However, the materials are not limited to the examples above and may be any materials having chemical and biological stability (i.e., inactivity), optical transparency, and mechanical processability. The body of revolution  100  may have a hole at the center thereof. Since the hole receives a rotation operating unit (not illustrated) and a spindle (not illustrated), the body of revolution  100  can rotate. Thus, the center of the body of revolution  100  acts as a rotational axis. 
         [0047]    The body of revolution  100  may include one or more microfluidic structures  101  therein. The body of revolution  100  may be formed of a pair of a first disk and a second disk. Or, the body of revolution  100  may be formed of a first disk, a second disk, and a lid disk. These disks are adhered to each other at, for example their circumferences by known methods. Such microfluidic structures  101  may be provided by a three-dimensional pattern formed on any one or both of the first and the second disks. The lid disk may have a plurality of through holes which serve as an inlet and/or outlet. A double-sided bonding layer may be interposed between the two disks. However, the structure of the microfluidic structures  101  is not limited thereto. When two or more microfluidic structures  101  are included in the body of revolution  100 , a target molecule such as a protein, polypeptide, carbohydrate, or the like can be detected from various samples, for example, blood specimens from a number of people at the same time. In addition, different target molecules can be detected from one sample in respective individual microfluidic structure  101 . 
         [0048]      FIG. 2  is an enlarged view illustrating one section of the microfluidic device of  FIG. 1 , according to an embodiment of the present invention. The microfluidic structure  101  schematically illustrated in  FIG. 1  is described below with respect to an exemplary usage. The top part and lower part of the section of the body of revolution  100  of  FIG. 1 , as depicted on the sheet of drawing, are each a center and a circumference part of the body of revolution  100 , respectively. The microfluidic structure  101  according to the current embodiment of the present invention includes a sample chamber  11 , a buffer chamber  12 , and a bead chamber  13 , wherein the sample chamber  11  receives a fluid sample, the buffer chamber  12  receives a buffer solution, and the bead chamber  13  includes a plurality of particles such as beads. Each of the sample chamber  11 , the buffer chamber  12 , and the bead chamber  13  include an inlet through which samples, a buffer solution, and a bead solution can be introduced by, for example injection. The target molecule which is to be separated from the fluid biological samples may be a protein, polypeptide, or carbohydrate, etc. In the present specification, a protein is exemplified as a target molecule to be separated, but it should be noted that the present invention may be applied to the separation of different molecules of interest using, for example, different capture probes, buffer solutions, and the like. 
         [0049]    The distance from a center of the rotation body  100  to the mixing chamber  14  is greater than the distances from the center to the sample chamber  11 , the buffer chamber  12 , and the bead chamber  13 . The mixing chamber  14  is fluid connected to the sample chamber  11 , the buffer chamber  12 , and the bead chamber  13  through channels  21 ,  22 , and  23 , respectively, wherein the channels  21 ,  22 , and  23  are fluid transfer passages. Valves  31 ,  32 , and  33  which control fluid flow are disposed in the channels  21 ,  22 , and  23 , respectively. The three valves  31 ,  32 , and  33  may be opening valves which are closed normally and open when desired. The mixing chamber  14  has an outlet at a location farthest from the center (or rotation axis) of the body of revolution  100 , wherein the outlet includes a valve  34  (hereinafter, referred to as outlet valve). The mixing chamber  14  may have a shape with different cross-sectional dimensions along the radial direction of the rotation body  100 . For example, it has a smaller dimension near its outlet portion, i.e., near the circumference of the body of revolution  100  than its center portion, as depicted in  FIG. 2 . Also, the narrower outlet area can have an extended length. In this case, a portion of the inside of the outlet valve  34  can be formed as a channel. Meanwhile, the mixing chamber  14  may contain a detection probe solution introduced in advance. In addition, a fluid sample, a buffer solution, and a beads (M 1 ) solution may be introduced to the mixing chamber  14  from the sample chamber  11 , the buffer chamber  12 , and the bead chamber  13 , respectively. 
         [0050]    A waste chamber  15  is disposed far away from the rotation axis of the body of revolution  100  than the mixing chamber  14 . The waste chamber  15  can be connected to the outlet area of the mixing chamber  14 , through a channel  25 . In this case, there should be enough space between the place of the mixing chamber  14  to which the channel  25  is connected and the outlet valve  34  so that the beads M 1  are collected in the bottom area (i.e., where there is an outlet of the mixing chamber  14 ). 
         [0051]    The fluids can flow into the waste chamber  15  from the mixing chamber  14  at least two times. First, sample residue obtained after a reaction with the beads M 1  flows into the waste chamber  15  and then a buffer solution which rinses the beads M 1  flows into the waste chamber  15 . Therefore, the channel  25  may include a valve which can open and close at least two times. When a single use valve which can either open or close a channel once is used, the channel  25  may include at least two branch channels  25   a  and  25   b  through which the fluids flow into the waste chamber  15  from the mixing chamber  14  to be used one at a time. In addition, the two branch channels  25   a  and  25   b  may be closed after each channel transfers the fluids once. Accordingly, opening valves  35   a  and  35   b  and closing valves  45   a  and  45   b  can be disposed in the branch channels  25   a  and  25   b.    
         [0052]    Moreover, an optical signal expression chamber  16  is disposed further away from the center of the body of revolution  100  than the outlet of the mixing chamber  14 . The optical signal expression chamber  16  is connected with the outlet valve  34  disposed in the mixing chamber  14  through a channel  26 . The optical signal expression chamber  16  may contain a substrate solution introduced in advance, wherein the substrate binds to a target protein captured by the beads M 1 , and then the substrate is allowed to react with an optical signal expression material of the detection probe solution flowing into the optical signal expression chamber  16  and to express an optical signal. The substrate solution may include a substrate and an enzyme which are needed to generate optical signal after reacting with the optical signal expression material of the detection probe. In addition, a magnetic material which generates a magnetic field, for example, a magnet  230  may be disposed near the optical signal expression chamber  16 . When the beads M 1  are of magnetic materials, the magnet  230  attracts the magnetic beads, which then are collected in the mixing chamber  14 . Beads M 1  will be explained in more detail hereinafter. 
         [0053]    Meanwhile, the magnet  230  may move to various positions along a radial direction of the body of revolution  100  and supports a position control of the magnetic beads. For example, the magnet  230  moves the magnetic beads, which are separated and collected using centrifugal force, at the outlet of the bead chamber  13  or the mixing chamber  14  to the center of each chamber (bead chamber  13  or the mixing chamber  14 ) so that the magnetic beads can be easily dispersed in a fluid contained in the chambers. 
         [0054]    In order for the beads M 1  to capture a target biological material (including an antigen on the surface of a pathogen) from biomaterial samples such as whole blood, saliva, and urine, the beads M 1  have probes that capture the target material through a specific binding to the target material. For example, the capture probes may be antibodies that are coupled to the surfaces of the beads M 1 . The antibodies have a unique affinity for a specific target material, for example, an antigen protein on the surface of certain cells and viruses and thus are useful when detecting cells and viruses of a significantly low concentration. The magnetic beads coupled with antibodies which can specifically bind to antigens are commercially available from, for example Invitrogen and Qiagen. Examples of the magnetic beads may be DYNABEADS® Genomic DNA Blood (Invitrogen), DYNABEADS® anti- E.coli  0157 (Invitrogen), CELLECTION™ Biotin Binder Kit (Invitrogen), and MAGATTRACT Virus Min M48 Kit (Qiagen).  Diphtheria toxin, Enterococcus faecium, Helicobacter pylori, Hepatitis B  virus (HBV),  Hepatitis C  virus (HCV), Human immunodeficiency virus (HIV),  Influenza A, Influenza B, Listeria, Mycoplasma pneumoniae, Pseudomonas  sp.,  Rubella virus,  and  Rotavirus  can be separated using magnetic beads combined with specific antibodies. Alternatively, desired magnetic beads which has desired probes may be fabricated by a method explained in commonly owned co-pending application Ser. Nos. 11/752,321 and 11/839,023, contents of which are incorporated herein in their entirety by reference. 
         [0055]    The size of the beads M 1  may be 50 nm to 10 mm, for example, 1 μm-50 μm for chamber-to-chamber moving beads, and 150 μm to 5 mm for one-chamber-confined beads. The beads M 1  may be a mixture of two or more types of beads having different sizes. In other words, the beads M 1  may have uniform sizes or various sizes. 
         [0056]    The beads M 1  may be formed of any magnetized materials. In particular, the beads M 1  may include one or more materials selected from the group of ferromagnetic metals consisting of Fe, Ni, and Cr and oxides thereof. 
         [0057]    The beads M 1  may be formed of a non-magnetic material. For example, the non-magnetic material may be PS (polystyrene) PMMA (polymethylmethacrylate). 
         [0058]    In the detection probes including the optical signal expression material, materials for detection probes used in a conventional enzyme-linked immunosorbent assay (ELISA) can be used. For example, when a primary antibody is adhered to the surfaces of the beads M 1  as a capture probe for detecting a target antigen or an antigen on a target material, a second antibody in which a marker such as horseradish peroxidase (HRP) is combined can be employed as the detection probes. In this case, the optical signal emit chamber  16  may include a substrate solution including a substrate and an enzyme. The substrate and the enzyme produce changes in colors due to a reaction with HRP. Even though a HRP is explained above with respect to an optical signal emitter, other optical signal emitting substances, which are known in the art, may be used. Also, instead of optical signal emitting substances, other types of signal emitter may be used for the same purposes. 
         [0059]      FIG. 3  is a plan view schematically illustrating a microfluidic device according to another embodiment of the present invention. The microfluidic device according to the current embodiment of the present invention includes a microfluidic structure  102  which is similar to the microfluidic structure  101  of  FIG. 2  according to the previous embodiment of the present invention, except the structure of the channel  22  which fluid connects the mixing chamber and the buffer chamber  12  and the addition of a second waster chamber  15 . The buffer chamber  12  of the microfluidic structure  102  is formed here larger than that of the microfluidic structure  101 . In addition, the channel  22  connecting the buffer chamber  12  and the mixing chamber  14  is branched off in a number of channels and thus each branched channel can be connected with positions corresponding to various levels of fluid in the buffer chamber  12 . Here, each of the branched channels may include valves  32   a,    32   b,  and  32   c,  wherein the valves  32   a,    32   b,  and  32   c  may be opening valves which can be operated individually and independently. In this embodiment, the microfluidic structure  101  has a second waste chamber  15 . Channels  25   c  and  25   d  and valves  35   c  and  35   d  can be added, wherein the channels  25   c  and  25   d  and valves  35   c  and  35   d  discharge the fluids from the mixing chamber  14  to the second waste chamber  15  as fluid flows into the mixing chamber, and then are closed. Accordingly, a small amount of a buffer solution contained in the buffer chamber  12  is provided to the mixing chamber  14  to wash the beads M 1 , and remaining of the buffer solution separated from the beads M 1  is discharged into the waste chamber  15  each time. 
         [0060]      FIG. 4  is a plan view schematically illustrating a microfluidic device according to another embodiment of the present invention. The microfluidic device according to the current embodiment of the present invention includes a microfluidic structure  103  which is similar to the microfluidic structure  102  of  FIG. 3  according to the previous embodiment of the present invention. The differences between the microfluidic structure  103  and the microfluidic structure  102  are as follows. The microfluidic device  103  further includes a centrifuging unit  18  which is disposed between the outlet of the sample chamber  11  and the mixing chamber  14 . The centrifuging unit  18  includes a supernatant channel  182  and a precipitate collecting unit  181 , and a portion of the supernatant channel  182  is fluid connected with the mixing chamber  14  through the valve  31  and the channel  21 , wherein the supernatant channel  182  is extended from the outlet of the sample chamber  11  towards the circumference of the body of revolution  100  and the precipitate collecting unit  181  having expanded width is disposed at a distance toward the circumference of the body of revolution  100 . The supernatant channel  182  and the precipitate collecting unit  181  are fluid connected through a channel. Here, the precipitate collecting unit  181  and the supernatant channel  182  can also be connected to each other through a bypass channel  183 . The bypass channel  183  acts as an exhaust pipe of the precipitate collecting unit  181  and supports the sample chamber  11  in providing a fixed amount of the sample fluid into the mixing chamber  14 , even if an excessive amount of the sample fluid is introduced into the sample chamber  11 . 
         [0061]    A detailed description of an operation of the centrifuging unit  18  is as follows. When whole blood is introduced into the sample chamber  11  and then the body of revolution  100  is rotated, blood cells (e.g., red blood cells, white blood cells, platelets, etc) are collected in the precipitate collecting unit  181  and serum is received in the supernatant channel  182 . In this case, when the valve  31  of the channel  21 , which fluid connects the supernatant channel  182  to the mixing chamber  14 , is opened, serum in the supernatant channel  182  flows into the mixing chamber  14  by centrifugal force. That is, the serum in the supernatant channel  182  is positioned closer to the center of the body of revolution  100  than the channel  21  and transferred to the mixing chamber  14  when the valve  31  is open. Accordingly, in the microfluidic device  103  according to the current embodiment of the present invention, blood cells which may interfere with an accurate detection of a target material can be removed from the sample fluid beforehand. 
         [0062]      FIG. 5  is a plan view schematically illustrating a microfluidic device according to another embodiment of the present invention. The microfluidic device according to the current embodiment of the present invention includes a microfluidic structure  104  which is similar to the microfluidic structure  103  of  FIG. 4  according to the previous embodiment of the present invention. However, the differences between the microfluidic structure  104  and the microfluidic structure  103  are as follows. The microfluidic structure  104  may further include a stopping chamber  17  connected to the optical signal expression chamber  16  by a valve  37  which is disposed between the stopping chamber  17  and the optical signal expression chamber  16 . The stopping chamber  17  includes the substrate solution included in the optical signal expression chamber  16  and a stopping solution which stops reaction of the optical signal expression material of the detection probe. Thanks to the action of the stopping solution, a reaction which generates optical signal emission is stopped when the valve  37  is opened and a mixed fluid of the substrate solution and the beads M 1 , which have surface adhesion materials flows into the stopping chamber  17 . As such, the strength of the optical signal can be maintained constantly. Accordingly, the time to progress a reaction of optical signal emission can be uniformly controlled. Thus, during detecting an optical signal using a light detecting unit ( 70 , refer to  FIG. 10 ), regardless of the point of time of measuring the signal, an objective comparison of the strengths of the detected optical signal is possible. 
         [0063]    Although the above embodiments illustrate that the mixing chamber  14  receives the bead solution supplied from the bead chamber  13 , the bead solution may be directly injected into the mixing chamber  14 . Further, if the bead solution is received in the mixing chamber  14 , the microfluidic structures  101 ,  102 ,  103 , and  104  may not be provided with the bead chamber  13 . 
         [0064]    Differing from the description in the above embodiments, the beads M 1  may not move to the optical signal expression chamber  16 . For this purpose, non-magnetic beads having a large size so as not to pass through the channel  26  may be used. The substrate solution may be directly injected into the mixing chamber  14  so as to react with the second probe binding to the surfaces of the non-magnetic beads together with the target protein. Further, if the substrate solution reacts with the second probe in the mixing chamber  14 , the termination solution may be directly injected into the mixing chamber  14  so as to stop reaction to express an optical signal. 
         [0065]    The valves  31 ,  32   a  through  32   c,    33 ,  34 ,  35   a  through  35   d,  and  45   a  through  45   d  described in the above embodiments can be selected from the group consisting of a capillary valve, a hydrophobic valve, a mechanical valve, and a phase-change valve. The phase-change valve may include a valve plug including heat generating particles and phase-change materials, and the heat generating particles absorbing an energy, for example electromagnetic wave and generate heat to melt the phase-change materials. The phase-change valve control the flow of fluid passing through the channels according to positions of the valve plug in the channels. 
         [0066]    Here, the phase-change valve may include an opening valve, wherein the opening valve is disposed for the valve plug to close the channel at an initial stage and moves to a space which is adjacent to the initial position of the valve plug after the valve plug is melted by heat, to open the channel. In addition, the phase-change valve may also include a closing valve which is disposed in a valve chamber connecting with the channel for the valve plug to open the channel at an initial stage and to flow into the channel after the valve plug is melted and expanded by heat, to close the channel. Hereinafter, the phase-change valve which can be employed in the microfluidic device according to the current embodiment of the present invention described above will be described more fully. Examples of valve units comprising phase-change valve, which may be implemented into the microfluidic systems according to embodiments of the present invention, other modifications and changes are described, for example, in a commonly owned, co-pending application Ser. No. 11/770,762, disclosure of which is incorporated by reference. 
         [0067]      FIG. 6  is a cross-sectional view of an exemplary opening valve which may be used to control the fluid flow in a microfluidic device according to an embodiment of the present invention. The opening valve  30  which is an example of the phase-change valve (corresponding to the valves  31 ,  32 ,  33 ,  34 ,  35   a  through  35   d,  and  37  of  FIGS. 2 through 5 ) includes a valve plug  301  in which heat generating particles are dispersed in phase-change materials, wherein the phase-change materials are at a low viscosity stage (e.g., solid) at ambient temperature. In a lower part and an upper part of a channel  20  which is adjacent to the initial position of the valve plug  301 , wherein the valve plug  301  is in a solid state, a pair of channel expansion units  302  providing an available space prepared by expanding the width or the depth of the channel expansion unit  302  are disposed. 
         [0068]    The valve plug  301 , which is introduced through a through hole  110 A when it is in a melted state and then solidified, prevents flow of fluids F from an inlet I by blocking the channel  20  at ambient temperature. 
         [0069]    When the valve plug  301  is melted at high temperature, it moves to the adjacent channel expansion units  302  and thus is solidified while the channel  20  is opened. 
         [0070]    In order to heat the valve plug  301 , an external energy source (not illustrated) is disposed outside the microfluidic device, and the external energy source can radiate an electromagnetic wave to a region including the initial position of the valve plug  301 . Here, the external energy source may be laser light source irradiating a laser beam L, visible rays, a light emitting diode irradiating infrared rays, or a xenon lamp. In particular, in the case of a laser light source, at least one laser diode can be included. The external energy source can be selected according to a wavelength of the electromagnetic wave, which can be absorbed by heat generating particles included in the valve plug  301 . 
         [0071]    The channel  20  can be provided by a three-dimensional pattern formed on an inner part of a first disk  110  or an inner part of a second disk  120 , both form together the body of revolution  100 . The first disk  110  transmits electromagnetic waves irradiated from the external energy source (not illustrated) to be incident onto the valve plug  301 . In addition, the first disk  110  may be formed of optically transparent material in order to observe the fluid F from the outside. For example, glass or transparent plastic have excellent optical transparency and low manufacturing costs. 
         [0072]    The size of the heat generating particles dispersed in the valve plug  301  may be of the order of thousands of μm, and thus, can freely move in the channel  20 . When an electromagnetic wave is irradiated, the temperature of the heat generating particles is rapidly increased by the energy so as to generate heat, and the heat generating particles are uniformly dispersed in phase changing materials such as wax. In order for the heat generating particles to be dispersed uniformly in a phase changing material, the heat generating particles may have structures including a core having a metallic component and a hydrophobic shell. For example, the heat generating particles may include a core formed of Fe, which is a ferromagnetic material, and a shell formed of a plurality of surfactants which are bonded to Fe to surround the Fe core. In general, the heat generating particles are provided in a dispersed form on a carrier oil. In order for the heat generating particles having hydrophobic surfaces to be dispersed uniformly, the carrier oil may also be hydrophobic. The valve plug  301  can be manufactured by mixing the carrier oil containing the heat generating particles dispersed therein with the phase-change materials. The form of the heat generating particles is not limited to the examples above and may be polymer beads, quantum dots, or magnetic beads. 
         [0073]    The valve plug  301  may be formed of a phase-change material such as wax. When the radiation energy absorbed by the heat generating particles is dissipated in the form of heat energy, the wax is melted so as to have fluidity and thus a form of the valve plug  301  is broken down to open the flow channel of the fluids F. The wax forming the valve plug  301  may have an adequate melting point. When the melting point of the wax is too high, time required for the wax to be melted after laser irradiation is started is increased and thus an opening time is hardly controlled. When the melting point of the wax is too low, the fluids F can be leaked, since the wax is partially melted while laser is not irradiated. Examples of the wax may be paraffin wax, microcrystalline wax, synthetic wax, or natural wax. 
         [0074]    Meanwhile, the phase-change material may be gel or a thermoplastic resin. Example of the gel may include polyacrylamide, polyacrylates, polymethacrylates, and polyvinylamides. In addition, the thermoplastic resin may be COC (cyclic olefin copolymer), PMMA (polymethylmethacrylate), PC (polycarbonate), PS (polystyrene), POM (polyoxymethylene), PFA (perfluoralkoxy), PVC (polyvinylchloride), PP (polypropylene), PET (polyethylene terephthalate), PEEK (polyetheretherketone), PA (polyamide), PSU (polysulfone), or PVDF (polyvinylidene fluoride). 
         [0075]      FIG. 7  is a plan view of a closing valve which controls fluid flow in a microfluidic device according to an embodiment of the present invention and  FIG. 8  is a cross-sectional view of the closing valve of  FIG. 7  according to an embodiment of the present invention. 
         [0076]    The closing valve  40  (corresponding to the valves  45   a  through  45   d  of  FIGS. 2 through 5 ) which is another example of a phase-change valve, includes a channel  20 , a valve chamber  402 , and a valve plug  401 . Here, the channel  20  includes an inlet I and an outlet O and the valve chamber  402  is connected to the center of the channel  20 . In addition, the valve plug  401  in the valve chamber  402  in a solid-form at ambient temperature at an initial stage flows into the channel  20  after the valve plug  401  is melted and expanded by heating and is solidified again to block fluids F flowing through the channel  20 . 
         [0077]    Similar to the above-described opening valve  30 , the structure of the closing valve  40  can be provided by a three-dimensional pattern formed on an inner part of a first disk  110  or an inner part of a second disk  120 , both consisting of the body of revolution  100 . The first disk  110  may have a through hole  110 A which corresponds to the valve chamber  402  in order for electromagnetic waves (for example, a laser beam) to be easily incident onto the valve plug  401 . 
         [0078]    Phase-change materials P and heat generating particles M 2 , which form the valve plug  401 , are the same as those of the opening valve  30  described above. In addition, the external energy source (not illustrated) which provides an electromagnetic wave L to the valve plug  401  is as described above. 
         [0079]    When a laser beam is irradiated to the valve plug  401  including the phase-change materials P and the heat generating particles M 2 , both of which constitute a dispersing medium, the heat generating particles M 2  absorb radiation energy to heat the phase-change materials P. Accordingly, the volume of the valve plug  401  is expanded while the valve plug  401  is melted, and the valve plug  401  flows into the channel  20  through a channel  403  connected with the channel  20 . The valve plug  401  which is cooled down after contacting the fluids F in the channel  20 , blocks the fluids F flowing through the channel  20 . 
         [0080]      FIG. 9  is a detailed perspective view of the microfluidic device of  FIG. 5  according to an embodiment of the present invention. The microfluidic device including the microfluidic structure  104  according to the current embodiment of the present invention includes the first disk  110 , the second disk  120 , and a double-sided adhesive sheet  115  to adhere the first disk  110  and the second disk  120  to each other. The first disk  110  and the second disk  120  may be formed of a transparent plastic substrate, for example, a polycarbonate substrate. 
         [0081]    The first disk  110  includes a number of inlets  111  which penetrate the upper and lower surface of the first disk  110  and a number of through holes  110 A. The inlets  111  may be disposed to correspond to the sample chamber, the bead chamber, and the buffer chamber and the through holes may be disposed to correspond to the initial position of the valve plug in a number of phase-change valves. 
         [0082]    The second disk  120  includes a number of grooves  127  which have a certain depth so as to form a chamber structure when the second disk  120  is bonded to the first disk  110 . The depth may be, for example, 3 mm. In addition, the second disk  120  may further include intaglio structures including the channel expansion units  302  and valve chambers  402 . 
         [0083]    The double-sided adhesive sheet  115  may be prepared with a double-sided adhesive tape that is commonly used, for example, FLEXMOUNT™ DFM 200 Clear V-95150 POLY H-9 V-96 4, FLEXcon Inc., MA, USA. The double-sided adhesive sheet  115  includes a number of chamber outlines  117  corresponding to the grooves  127  and a number of channel outlines  116  corresponding to the channels described in  FIG. 4 . The channel outlines  116  may have the depth of 1 mm. Since the thickness of the double-sided adhesive tape that is commonly used is 100 μm, the depth of the channel formed by the first disk  110 , the second disk  120 , and the double-sided adhesive sheet  115  is 100 μm. The depth of the channel can be easily changed according to the thickness of the double-sided adhesive sheet  115 . 
         [0084]    The inlets  111 , through holes  110 A, grooves  127 , and the channel outlets  116  can be formed on each of the first disk  110 , the second disk  120 , and the double-sided adhesive sheet  115  by computer numerical control (CNC) machining 
         [0085]    The detailed structure and standard of the microfluidic device is only an example and is not limited thereto. For example, the first disk  110  and the second disk  120  can be adhered to each other by using various plastic bonding methods such as thermal bonding, low temperature bonding, chemical bonding, or ultrasonic bonding, instead of using the double-sided adhesive sheets  115 . The standard of the channels and chambers can become larger or smaller according to the size of the microfluidic device and an amount of samples to be processed. Meanwhile, when bonding means other than the double-sided adhesive sheets  115  are used, the channel can be formed in a trench form on the upper surface of the second disk  120 . In addition, in the embodiments described above, the microfluidic structure is prepared on one layer, however, can be formed on a plurality of layers, each layer having the microfluidic structure including channels and chambers. 
         [0086]      FIG. 10  is a perspective view schematically illustrating a microfluidic system according to an embodiment of the present invention. The microfluidic system according to the current embodiment of the present invention which includes at least one microfluidic structure  101  prepared on the body of revolution  100  includes any of the microfluidic devices according to the previous embodiments, a rotation operating unit  50  which rotates the body of revolution  100 , and a light detecting unit  70  which can optically detect the captured biomaterial of interest, which is obtained using the microfluidic device. In addition, the microfluidic system may further include an external energy source  60  which can irradiate an electromagnetic wave onto selected regions formed on the body of revolution  100 . The microfluidic system, which will be described in more detail, and other modifications, which may be used in the present application are described in commonly owned, co-pending application Ser. No. 11/847,623, filed Aug. 30, 2007, content of which is incorporated herein in its entirety by reference. 
         [0087]    The external energy source  60  can be used to maintain a temperature of chambers adequately in which reactions occur in the microfluidic device according to an embodiment of the present invention, for example, the mixing chamber  14  and the optical signal measuring chamber  16 . Here, laser light source, a light emitting diode, or a xenon lamp can be employed as described above. In addition, when a phase-change valve including heat generating particles M 2  such as magnetic beads is used in the microfluidic device, the external energy source  60  can be used to operate the phase-change valve. 
         [0088]    The microfluidic system may include an external energy source adjusting means (not illustrated) which adjusts position or direction of the external energy source  60  and concentrates electromagnetic waves irradiated from the external energy source  60  in a desired region on the body of revolution  100 , more specifically, a region corresponding to an element selected from a number of phase-change valves  31  and etc., the mixing chamber  14 , and the optical signal measuring chamber  16  included in the microfluidic device. 
         [0089]    Meanwhile, according to the current embodiment of the present invention, the microfluidic system may further include a magnet position control device which can move the magnet  230  to positions corresponding to various parts of the microfluidic device. The magnet position control device moves the magnetic beads in the microfluidic device or traps the magnetic beads to a specific position. Some elements of the magnet position control device can be formed as one body on the bottom surface of the lower disk  120  in the microfluidic device as illustrated in  FIG. 9 . For example, the magnet position control device may include a revolution plate  200  that is bonded with the body of revolution  100  at the bottom of the microfluidic device and an external magnet  231  disposed outside of the revolution plate  200 . The revolution plate  200  includes a guide rail  210  and the magnet  230  moves along the guide rail  210 . The shape of the guide rail  210  can be changed according to an arrangement of the chambers and the channels in the microfluidic device and the movement order of fluids including the magnetic beads. Thus, the guide rail  210  may be a path which can connect various positions having each different distance from the rotational axis of the revolution plate  200  and move the magnet  230 . 
         [0090]    The external magnet  231  can be disposed to be fixed to a specific position or to be temporarily fixed to a desired position while moving along a radial direction of the revolution plate  200 . The external magnet  231  influences magnetic force to the extent that the position of the magnet  230  in the guide rail  210  is moved and should not influence magnetic force to the extent that the magnetic beads in the microfluidic device are moved. 
         [0091]    When the microfluidic device and the revolution plate  200  are simultaneously rotated, centrifugal force of an outside direction of the radius and magnetic force (gravitation or repulsive force) are influenced to the magnet  230  in the guide rail  210  and thus the magnet  230  moves to a position where both forces are balanced. In addition, when the revolution plate  200  starts rotating, the magnet  230  can move in a circumferential direction due to inertial force influence to the magnet  230 . A permanent magnet can be employed as the magnet  230  and the external magnet  231 . An example of the permanent magnet may include a neodymium magnet (Nd—Fe—B). 
         [0092]    According to the current embodiment of the present invention, the guide rail  210  provides a path which connects the positions corresponding to the bead chamber  13 , the outlet and the center of the mixing chamber  14 , and the optical signal emission chamber  16 . The magnet  230  can move to a desired position according to the position of the external magnet  231  and a rotational direction and a rotational speed of the revolution plate  200 . The magnet  230  influences magnetic force to adjacent portion in the microfluidic device so as to move or trap the magnetic beads. 
         [0093]    An external energy source adjusting mean (not illustrated) in the microfluidic system of  FIG. 10  can move the external energy source  60  installed facing the body of revolution  100  in a direction indicated by an arrow, in other words, a radial direction of the body of revolution  100 . A mechanism of rectilinearly moving the external energy source  60  can be provided in various ways and is obvious to those of ordinary skill in the art. Therefore, a detailed description thereof is omitted. 
         [0094]    Meanwhile, the microfluidic system includes the rotation operating unit  50  which rotates the body of revolution  100 . The rotation operating unit  50  as illustrated in  FIG. 10  is to settle the body of revolution  100  and to transmit a turning force. In addition, while not illustrated in  FIG. 8 , a motor and related parts thereof for the body of revolution  100  to be constantly rotated and reversely rotated can be included in the microfluidic system. A detailed description of the configuration of the rotation operating unit  50  is omitted. The external energy source  60  can irradiate an electromagnetic wave concentrically on the selected region on the body of revolution  100  of the microfluidic device with the support of the external energy source adjusting means (not illustrated) and the rotation operating unit  50 . 
         [0095]    For example, when the phase-change valve  31  which should be operated at a certain point of time is selected, the position of the phase-change valve (not illustrated) is known at the starting point of irradiating the external energy source  60  and Δ (r,θ) (not shown), which is a deviation from the laser light source  60  to the phase-change valve, is obtained. Δθ is a distance to be moved in the rotation direction and Δr is a distance to be moved in the radial direction of the body of the revolution.  100  In addition, the body of revolution  100  can be reversely rotated by Δθ using the rotation operating unit  50  and the external energy source  60  can be moved toward a radial direction of the body of revolution  100  by Δr using the external energy source adjusting means (not illustrated). 
         [0096]      FIG. 11  is a series of schematic diagrams illustrating a process of an immunoassay using beads performed in a microfluidic device according to an embodiment of the present invention. First, beads including capture probes on the surface thereof, the capture probes having a unique affinity for specific target protein, are prepared to collect specific target protein using the beads. In the current embodiment of the present invention, streptavidin is coated onto the surface of the magnetic beads, the magnetic beads including a core formed of magnetic materials and a shell formed of agarose to surround the core, and biotinylated HBsAg (Hepatitis virus B surface antigen) is adhered onto the surface of the magnetic beads as the capture probe. 
         [0097]    When the beads prepared as above are mixed with the sample including Anti-HBs ( Hepatitis virus B  surface antibody), Anti-HBs binds to HBsAg of the capture probe. Here, when HBsAg (secondary antibody) conjugated to HRP is added as the detection probe, HBsAg of the detection probe binds to Anti-HBs. Accordingly, when the beads in which (HBsAg)-(Anti-HBs)-(HBsAg-HRP) binding is formed on the surface of the beads are washed using a buffer solution, free detection probes are all washed off and the detection probes bonded to the beads only remain as above. 
         [0098]    When the beads (which are) washed as above are mixed with materials which can express an optical signal due to a HRP action, for example, a substrate solution including an substrate and an enzyme, a transparent material included in the substrate expresses color (for example, blue) by an enzymatic reaction so as to express an optical signal. Since the optical signal is detected optically, presence of a target protein such as Anti-HBs in the sample can be detected. However, the above process is only an example. As another example, when a detection probe including fluorescein isothiocyanate (FITC) is used, optical detection through fluorescence manifestation is possible without additional reaction with a substrate solution. 
         [0099]      FIGS. 12A through 12P  are photographic images illustrating a process of detecting Anti-HBs using a microfluidic device according to an embodiment of the present invention. The process described in  FIG. 11  is performed in the microfluidic device of  FIG. 4  and is illustrated in  FIGS. 12A through 12P . 
         [0100]    As described above, 100 μl of a bead solution including the beads on which HBsAg is adhered was injected into the bead chamber, and 100 μl of whole blood was injected into the sample chamber as a sample ( FIG. 12A ). While the body of revolution was rotated, the sample was separated into blood cell and serum using the centrifuging unit ( FIG. 12B ). The phase-change valve  31  was opened using the external energy source and 30 μl of serum was transferred into the mixing chamber. A detection probe solution injected into the mixing chamber in advance and the serum were mixed ( FIG. 12C ). The valve connecting with the bead chamber was opened, and the bead solution was transferred into the mixing chamber ( FIG. 12D ). While the body of revolution was alternately rotated in clockwise and ant-clockwise directions using the rotation operating unit, the beads, the sample, and the detection probe solution were reacted. In this case, the temperature of the mixing chamber may maintain similar to in vivo condition using the external energy source ( FIG. 12E ). Then, beads contained in the mixing chamber were precipitated using centrifugal force ( FIG. 12F ). 
         [0101]    The channel connecting first with the waste chamber was opened to discharge residual sample (supernatant separated from the beads) to the waste chamber, wherein the residual sample is obtained after the reaction ( FIG. 12G ). The channel was closed again ( FIG. 12H ) and the channel connecting the buffer channel and the mixing chamber was opened to transfer the buffer solution to the mixing chamber ( FIG. 12I ). The body of revolution was alternately rotated in clockwise and ant-clockwise directions again to wash the beads contained in the mixing chamber for 1 minute using the buffer solution ( FIG. 12J ). After the beads were precipitated ( FIG. 12K ), another channel connecting with the waste chamber was opened to discharge residual buffer solution, wherein the buffer solution completes washing the beads ( FIG. 12L ). As described above, when a capacity of the buffer chamber is large and the channel including the valves disposed at each water level is connected with the buffer channel, the process illustrated in  FIG. 12I through 12L  can be repeated. In other words, the beads can be washed many times. 
         [0102]    Next, the outlet valve of the mixing chamber was opened and the washed beads were transferred to the optical signal emission chamber  16  ( FIGS. 12M and 12N ). The body of revolution was alternately rotated in clockwise and ant-clockwise directions and the substrate solution contained in the optical signal emission chamber and the beads were mixed to induce an optical signal ( FIG. 12O ). In this case, the temperature of the optical signal emission chamber can be also raised similar to a temperature of a biomaterial using the external energy source. The beads precipitated in the optical signal emission chamber and an optical signal due to a reaction between the detection probe and the substrate was detected using the light detecting unit ( FIG. 12P ). 
         [0103]    As described above, the microfluidic device including a plurality of microfluidic structures and the microfluidic system including the microfluidic device according to the present invention can detect a target biomaterial, e.g., a protein of interest from biomaterial samples, through a series of processes performed quickly in the microfluidic structures such as injecting a sample into the microfluidic device. Therefore, an immunoassay performed using a conventional (Enzyme-Linked ImmunoSorbent Assay (ELISA) process which requires much effort from those of ordinary skill in the art is simplified and thus, time and effort can be significantly saved. In addition, target protein can be detected using a small amount of samples only. 
         [0104]    While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.