JP3628351B2 - Fine particle separation method and apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to the separation of fine particles by light. More particularly, the present invention relates to a method and apparatus for separating fine particles with laser light.
[0002]
[Prior art and its problems]
Various methods and devices have been developed and used in the past to separate micrometer-order particles such as cells, microorganisms, biological particles such as ribosomes, or synthetic particles such as latex particles, gel particles, and industrial particles. Yes.
Among these, it is reported that the fine particles are separated and supplemented by using so-called laser trapping that condenses the laser light to confine the fine particles in the space [H. Misawa, et al. Chem. Lett. , 469 (1991)].
[0003]
This is to separate and supplement the fine particles by utilizing the action of confining the particles by the radiation pressure generated by the reflection and refraction of light, and is based on the following principle.
That is, a light beam having a light intensity gradient from the center of the beam toward the outside is coherent like a laser beam condensed by a lens in a solution in which fine particles having a refractive index larger than that of a solvent are dispersed. When condensed and irradiated, this light is refracted in the fine particle, and at this time, a force (radiation pressure of light) corresponding to a change in the momentum of the photon by refraction of the light acts on the fine particle according to the law of conservation of momentum. The light radiation pressure can be divided into two forces: a light pressure (radiation pressure) that pushes the fine particles in the light traveling direction and a light gradient force that draws the fine particles in the optical axis direction of the beam. By these light pressure and light gradient force, the fine particles are accelerated in the direction of light travel and the direction of strong light intensity distribution. The light pressure and the light gradient force both depend on the light intensity and the intensity distribution in the optical axis direction, that is, the degree of condensing by the lens or the like and the intensity distribution in the direction perpendicular to the optical axis. This also depends on the refractive index and the absorptivity (reflectance) and the particle size of the fine particles. Of these forces, by effectively utilizing mainly the light gradient force, the fine particles can be attracted in the direction of strong light intensity distribution, and the fine particles can be captured at the focal point of the lens having the strongest light intensity.
[0004]
In the fine particle separation method using laser trapping described above, light having a multi-ring intensity distribution is obtained by optically interfering laser light with water in which two types of polystyrene fine particles having different sizes are dispersed in water. Is condensed and irradiated. Then, a large number of fine particles are trapped on each ring by the light gradient force. If the ring size is changed in this state, small particles with weak trapping force will be ejected out of the ring and removed, and only large particles will continue to be trapped on the ring, resulting in selective separation of large particles. That's it.
[0005]
However, the above-described separation method can only capture the same kind of fine particles having different particle sizes only, that is, a group of particles made of the same material, and cannot simultaneously separate three or more types of particle groups. Also, it could not be said that the separation performance was high.
Under such circumstances, the inventors of the present invention have already proposed a method and apparatus capable of simultaneously separating three or more types of particle groups as a method capable of overcoming these limitations. .
[0006]
This method mainly separates particles by irradiating the moving particles with interference light from a laser beam from a direction orthogonal to the moving direction of the particles, and applying an action force according to the type of the particles. Content. Another method is to irradiate the moving particles with laser scanning light from the direction orthogonal to the moving direction of the particles, thereby applying an action force according to the type of the particles to perform particle sorting. Further, in another method, by irradiating laser light interference light or scanning light from a direction perpendicular to the moving direction of the particles to a plurality of regions of the non-linear flow path in which the particles move, It is characterized in that particles are separated by applying an action force according to the type.
[0007]
These are useful in that three or more types of particles can be efficiently and simultaneously separated as compared with the above-described method using particle trapping. In order to irradiate the particle from the direction perpendicular to the moving direction of the particle, it is necessary to accurately adjust the optical axis of the laser beam, which requires a high degree of skill and long adjustment. It was. In addition, interference light or scanning light irradiated from a direction orthogonal to the moving direction of the particles has a limit in the acting force on the particles, and the separation efficiency cannot be increased beyond a predetermined level. In addition, it is necessary to provide means for irradiating interference light or scanning light, means for adjusting the optical axis of interference light or scanning light, etc. in a direction perpendicular to the moving direction of the particles. I had to be.
[0008]
The present invention has been made in order to eliminate the drawbacks of the prior art as described above, and by effectively using mainly the light pressure among the radiation pressures of light, various types having different particle diameters and refractive indexes. It is an object of the present invention to provide a new method and an apparatus therefor that can easily and efficiently sort various fine particles simultaneously.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present invention irradiates light from the axial direction of the linear flow path to the linear flow path filled with the fine particle dispersion solution, and irradiates the fine particles with light radiation pressure. It is characterized by separating fine particles by accelerating along the direction .
[0010]
Furthermore, a liquid transport force is applied to the solution in the linear flow path filled with the fine particle dispersion solution in the direction opposite to the light irradiation direction, and the fine particles are formed by balancing the light radiation pressure and the liquid transport force. You may make it fractionate along the irradiation direction of light.
The fine particle separation device includes a linear flow path for moving the fine particle dispersion solution and fine particles dispersed in the solution in the linear flow path by irradiating light from the axial direction of the linear flow path. And a light irradiating means for applying the radiation pressure.
[0011]
In addition, an imparting unit that applies a liquid transport force from a direction opposite to the light irradiation direction to the solution in the linear flow path filled with the fine particle dispersion solution may be provided.
Furthermore, particle measuring means may be arranged in the middle of the linear flow path.
[0012]
[Action]
In this invention, as a method for fractionating fine particles, light is irradiated to a linear flow path filled with a fine particle dispersion solution, so that the fine particles are accelerated by the action of light radiation pressure, and the particle size and / or refractive index of the fine particles are accelerated. Sorted according to The degree of separation can be easily adjusted by performing a simple operation such as changing the light intensity.
[0013]
Further, when the light irradiation is performed from the axial direction of the linear flow path, it is easy to adjust the optical axis of the light.
Furthermore, when a liquid transport force is applied to the solution in the linear flow channel from the direction opposite to the light irradiation direction, and the light radiation pressure and the liquid transport force are balanced, the fine particles are reduced in size. It becomes possible to perform separation by stopping at a predetermined position corresponding to the refractive index.
[0014]
Therefore, many types (three or more types) of fine particles can be separated.
Since the fine particle sorting apparatus effectively uses the radiation pressure of light, the structure becomes simple. If the light irradiation means is arranged so as to apply the radiation pressure of light from the axial direction of the linear flow path, the adjustment of the optical axis is easy and the size can be reduced.
[0015]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. Of course, the present invention is not limited to the following examples.
Example 1
FIG. 1 is an apparatus configuration diagram showing an embodiment of the separation method and apparatus of the present invention.
[0016]
As illustrated in FIG. 1, in the separation apparatus of the present invention, the sample container (1), the separation container (6), the linear capillary tube (4), the particle measuring means (5), and the light focusing lens (9). A laser light source (10), a dispersion medium supply means (11), a fine particle dispersion solution supply means (12), and a sorted particle discharge means (13) are disposed.
The sample container (1) is provided with a transparent glass plate (2), and the laser beam (8) condensed by the condenser lens (9) passes through the glass plate (2) and the sample container (1). The fine particle dispersion solution (3) therein is irradiated. The capillary tube (4) is inserted into the sample container (1) so that the optical axis of the laser beam (8) and the axis of the capillary tube (4) are on the same line. As the fine particle dispersion solution (3), a solution composed of many kinds (three or more kinds) of fine particles having different particle diameters and refractive indexes and a dispersion medium can be used. Here, a dispersion medium having a specific gravity similar to that of the fine particles is appropriately selected, but usually water, a buffer solution, or the like is used. The fine particles having different particle sizes and refractive indexes mean either (a) those having different particle sizes, (b) those having different refractive indexes, or (c) those having different particle sizes and refractive indexes. It is intended for biologically related particles and molecules such as cells, viruses, microorganisms, ribosomes, DNA and RNA, synthetic particles such as latex particles and industrial particles, and foreign substances such as dust.
[0017]
In the separation operation, the separation container (6) is initially filled with the dispersion medium (7) containing no fine particles. A capillary tube (4) is inserted and disposed in the sorting container (6) and the sample container (1), and the capillary tube (4) is horizontal. In addition, it is preferable to provide an appropriate liquid feeding means (not shown) for feeding the dispersion medium or the dispersion solution from the sample container (1) to the separation container (6) through the capillary tube (4).
[0018]
The particle measuring means (5) is provided in the middle of the capillary tube (4). As the particle measuring means (5), one utilizing an optical, photoelectric, electrical, magnetic, or acoustooptic principle can be used. The laser light (8) generated by the laser light source (10) is focused by the focusing lens (9), passes through the transparent glass plate (2), and is introduced into the capillary tube (4). The fine particles in the dispersion solution are accelerated and flow into the capillary tube (4) by the action of the radiation pressure of the light, especially the light pressure, by the laser beam (8). It can be measured by the particle measuring means (5), and the fractionation state can be known based on the particle size and refractive index of the fine particles passing through the position where the particle measuring means (5) is provided.
[0019]
The laser light source (10) is provided with a beam expander as necessary. The wavelength of the laser light emitted from the laser light source (10) is preferably a wavelength region in which the light absorption of the fine particles is small. When the fine particles are living body related particles such as cells, the near infrared light is less damaged by light irradiation. The infrared wavelength region is preferred. For this, a TEM00 mode (Gaussian beam) laser light source such as a solid laser such as a YAG laser, a gas laser such as an argon laser, or a semiconductor laser can be used. Needless to say, the light source is not limited to a laser light source, and any light source that generates coherent light can be used. Since the radiation pressure of laser light depends on the particle size and / or refractive index of the fine particles and the amount of laser light, in order to set the threshold for separating the fine particles according to the particle size and refractive index of the fine particles, It is necessary to be able to adjust the irradiation intensity. Therefore, a means for adjusting the light emission intensity of the laser light source, a means for adjusting the amount of irradiation light such as a modulation element or a filter in the optical path, a lens system or a beam expander that can be adjusted for magnification, or It is preferable to provide a particle classification threshold value changing unit including an optical wavelength changing element. By using such various means and changing the laser light irradiation conditions, it becomes possible to flexibly sort various kinds of fine particles.
[0020]
The operation of the separation apparatus having the above configuration will be described. First, only the dispersion medium is supplied from the dispersion medium supply means (11) to fill the sample container (1), the capillary tube (4), and the separation container (6). Next, the dispersion medium is discharged from the separation container (6) via the discharge means (13), and the dispersion solution is supplied from the fine particle dispersion solution supply means (12) to the separation container (6) and the capillary tube (4). Is filled with only the dispersion medium and the dispersion solution is added to the sample container (1). In this state, the laser beam (8) is condensed by the condenser lens (9), and irradiated to the fine particle dispersion solution (3) in the sample container (1). FIG. 2 is a schematic view illustrating light collection in the tube (4). The fine particles are attracted in the direction of the optical axis where the intensity distribution of the light is strong due to the light gradient force of the laser light (8), and a propelling action is given in the light traveling direction by the light pressure. Since the laser light is introduced from the axial direction of the capillary tube (4), the light pressure acts on the fine particles in the capillary tube (4), and the fine particles are accelerated. The light pressure applied to the fine particles varies depending on the particle size and / or refractive index of the fine particles, the amount of light per unit area, and the wavelength, and the optical axis of the laser beam (8) and the axis of the capillary tube (4) are the same, so dispersion The fine particles in the solution (3) are separated in the capillary tube (4). Therefore, the particle measuring means (5) discharges fine particles having the same property to the separation container (6) while measuring the particle size and / or refractive index of the separated particles, and the particles having the same property are discharged via the discharging device (13). Separate for each fine particle. By repeating these operations, three or more kinds of fine particles are separated from the dispersion solution, separated and concentrated.
[0021]
Example 2
FIG. 3 is an apparatus configuration diagram showing another example of the sorting apparatus according to the present invention.
As illustrated in FIG. 2, the separation device of FIG. 1 is provided with fluid conveying means by electroosmotic flow.
Electroosmotic flow is known as a kind of interfacial conduction phenomenon, and is generated by a potential difference that occurs in the electric double layer at the interface between the glass tube wall and the solution. Normally, the glass tube wall is negatively charged by the dissociation of silanol groups. Therefore, the whole solution behaves like a cation and flows toward the negative electrode side. Although the description of the same configuration as that of Example 1 is omitted, this separation apparatus includes electrodes (15) and (16) connected to a power source (14) in the sample container (1) and the separation container (6), respectively. Thus, a transport force (liquid feeding force) is generated by electroosmotic action in the solvent from the separation container (6) to the sample container (1). The transport force in this direction can be applied to the solvent by changing the polarity of the electrodes (15) and (16) inserted into the sample container (1) and the separation container (6) according to the type of the solvent. . In the case of a buffer solution, the electrode (15) inserted into the sample container (1) is used as a positive electrode, and the electrode (16) inserted into the separation container (6) is used as a negative electrode. Can be generated, and the solution will flow toward the sample container (1) at a constant rate.
[0022]
Therefore, the apparatus of this example operates as follows.
That is, in the same manner as in Example 1, the separation container (6) and the capillary tube (4) are filled with the dispersion solvent for buffer solution (7), and the sample container (1) is filled with the dispersion solution. To do. Using the electrode (15) inserted into the sample container (1) as a positive electrode and the electrode (16) inserted into the separation container (6) as a negative electrode, the solvent is separated from the separation container (6) into the sample container (1) by electroosmosis. In addition to providing a solvent transporting force, laser light (8) is applied to the fine particle dispersion (3) in the sample container (1) to be introduced into the capillary tube (4), and the fine particles are separated into the separation container (6). Give the light pressure to go. The light pressure acts as a driving force and the solvent transport force acts as a braking force on the fine particles. Then, the light pressure acting on the fine particles depends on the particle size and / or refractive index of the fine particles, the amount of light per unit area, and the wavelength, while the transport force of the fine particle solvent depends on the particle size of the fine particles. Accordingly, each fine particle is stopped at a predetermined position of the capillary tube (4) where the effects of the light pressure acting on the fine particles and the solvent transport force are balanced. In this way, the fine particles separated at a predetermined position of the capillary tube (4) are discharged into the separation container (6), whereby the fine particles are separated and concentrated.
[0023]
Example 3
In order to give a transport force to the solvent, not only the above-described electroosmotic flow but also other methods, such as a pressure liquid feeding method using a pump or the like, a liquid feeding method using gravity, and the like can be adopted. By applying a liquid feeding force to the solvent, it is possible to adjust the separation ability of the fine particles, or to collect the fine particles after concentrating them.
[0024]
Therefore, the apparatus of FIG. 1 was arranged vertically or inclined, and the fine particles were separated using an apparatus in which gravity acts on the solvent. Introducing the results, 1 μm fine particles with the smallest diameter are separated from the three types of polystyrene particles having diameters of 1 μm, 3 μm, and 6 μm in the vicinity of the focal point of the laser beam (8). It was confirmed that 6 μm fine particles having a large diameter were separated in a region farthest from the focal point.
[0025]
【The invention's effect】
Since the present invention is configured as described in detail above, as a method for separating fine particles, light is irradiated to a linear flow path filled with a fine particle dispersion solution. , Accelerated, and fractionated according to the particle size and / or refractive index of the fine particles. The degree of separation can be easily adjusted by performing a simple operation such as changing the intensity of light.
[0026]
Furthermore, when the light irradiation is performed from the axial direction of the linear flow path, the optical axis of the light can be easily adjusted. Further, when a liquid transport force is applied to the solution in the linear flow path from the direction opposite to the light irradiation direction, and the light radiation pressure and the liquid transport force are balanced, the fine particles are reduced in size and / or Alternatively, it can be efficiently separated by stopping at a predetermined position corresponding to the refractive index.
[0027]
Therefore, many kinds (three or more kinds) of fine particles can be easily separated without requiring a high degree of skill.
The fine particle sorting apparatus has a simple structure because it effectively uses the radiation pressure of light, especially the light pressure. And if the light irradiation means is arranged so as to give the radiation pressure of light from the axial direction of the linear flow path, it is easy to adjust the optical axis, and it does not require a long time for adjustment and can be downsized. It becomes.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a sorting apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic view illustrating light collection in a tube.
FIG. 3 is a schematic diagram showing a sorting apparatus according to another embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sample container 2 Transparent glass plate 4 Capillary tube 5 Particle measuring means 9 Laser condensing lens 10 Laser light source

Claims (5)

The linear flow path filled with the fine particle dispersion solution is irradiated with light from the axial direction of the linear flow path, and the fine particles are accelerated along the light irradiation direction by the radiation pressure of the light to separate the fine particles. A method for fractionating fine particles, which is performed. Applying liquid transport force to the solution in the linear flow path filled with the fine particle dispersion solution from the opposite direction of the light irradiation direction, and balancing the light radiation pressure and liquid transport force, the light irradiation direction of the fine particles The method of fractionating fine particles according to claim 1 , wherein the fractionation is performed along the line. Light for irradiating light from the direction of the axis of the linear flow path and applying light radiation pressure to the linear flow path for moving the fine particle dispersion solution and the fine particles dispersed in the solution in the linear flow path fractionator fine particles and having an irradiation unit. 4. The fine particle separation device according to claim 3, further comprising an applying means for applying a liquid transport force to the solution in the linear flow path filled with the fine particle dispersion solution from the direction opposite to the light irradiation direction. 5. The fine particle sorting apparatus according to claim 3 , wherein a particle measuring means is disposed in the middle of the linear flow path.

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