Method for concentrating minute objects, kit for concentrating minute objects, and system for concentrating minute objects

Abstract

A micro-object concentration method comprises first to third steps. The first step is a step for preparing an optical fiber (50) having a tip provided with a metal thin film (52). The second step is a step for arranging the tip of the optical fiber (50) in a liquid in which a plurality of micro-objects are dispersed. The third step is a step in which light having a wavelength contained in the absorption wavelength region of the metal thin film (52) is introduced into the optical fiber (50), thereby heating the liquid around the tip of the optical fiber (50) and generating convection.

Description

[Technical Field]

[0001] The present disclosure relates to a method for concentrating minute objects, a kit for concentrating minute objects, and a system for concentrating minute objects, and more particularly to a technique for concentrating a plurality of minute objects dispersed in a liquid. [Background technology]

[0002] International Publication No. 2018 / 159706 (Patent Document 1) and International Publication No. 2020 / 218347 (Patent Document 2), for example, disclose techniques that can highly efficiently concentrate multiple microscopic objects dispersed in a liquid. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 159706 [Patent Document 2] International Publication No. 2020 / 218347 Summary of the Invention [Problem to be solved by the invention]

[0004] In the inventions disclosed in Patent Documents 1 and 2, a photothermal conversion region is provided on the bottom of a container, the main surface of a substrate, or the like. In this case, multiple minute objects dispersed in a liquid are concentrated in the vicinity of the photothermal conversion region. This means that the locations where minute objects can be concentrated are limited to the bottom of a container, the main surface of a substrate, etc. In order to expand the application of minute object concentration technology to various fields in the future, it is desirable to be able to concentrate minute objects at any location in a liquid.

[0005] The present disclosure has been made to solve the above-mentioned problems, and one of the objects of the present disclosure is to concentrate minute objects at any location in a liquid. [Means for solving the problem]

[0006] (1) A method for concentrating minute objects according to a first aspect of the present disclosure includes first to third steps. The first step is a step of preparing an optical fiber having a tip provided with a photothermal conversion material. The second step is a step of placing the tip in a liquid in which a plurality of minute objects are dispersed. The third step is a step of introducing light having a wavelength included in the absorption wavelength range of the photothermal conversion material into the optical fiber, thereby heating the liquid around the tip of the optical fiber and generating convection.

[0007] (2) The step of placing (second step) includes a step of adjusting the position or height of the tip of the optical fiber in the liquid.

[0008] (3) The preparing step (first step) includes a step of pretreating the photothermal conversion material so that the transmittance or extinction rate of the photothermal conversion material is stabilized against changes in the power of light propagating through the optical fiber.

[0009] (4) The step of generating convection (third step) includes the step of generating microbubbles at the tip of the optical fiber and concentrating a plurality of minute objects in the region between the tip and the microbubbles.

[0010] (5) The step of disposing includes a step of setting the arrangement of the optical fiber with respect to the substrate holding the liquid to one of a non-contact arrangement and a contact arrangement. The non-contact arrangement is an arrangement in which the propagation path of the optical fiber does not contact the substrate. The contact arrangement is an arrangement in which the propagation path of the optical fiber contacts the substrate.

[0011] (6) The step of placing includes a step of placing the optical fiber in a non-contact arrangement, and the step of generating convection includes a step of concentrating a plurality of micro-objects at the tip without generating microbubbles at the tip where the pretreatment has been performed.

[0012] (7) The step of placing is a step of placing the optical fiber in a contact arrangement, and the step of generating convection includes a step of concentrating a plurality of micro-objects along the optical path of the light emitted from the tip.

[0013] (8) The method for concentrating minute objects further includes a step of introducing a surfactant into the liquid prior to the step of generating convection (third step).

[0014] (9) The introducing step includes a step of adjusting the concentration of the surfactant in the liquid to a critical micelle concentration.

[0015] (10) Each of the plurality of microscopic objects is a quantum sensor, and the quantum sensor includes at least one of a nanodiamond, a fluorescent molecule, a quantum dot, a metal nanoparticle, and a metal nanorod.

[0016] (11) A method for concentrating minute objects according to a second aspect of the present disclosure concentrates a plurality of minute objects dispersed in a liquid. The method for concentrating minute objects includes the steps of preparing an optical fiber having a tip provided with a photothermal conversion material, and positioning the tip at a position where the liquid is heated and convection occurs in the liquid when light of a wavelength included in the absorption wavelength range of the photothermal conversion material is introduced into the optical fiber.

[0017] (12) The step of placing includes a step of placing the tip at a position where a photo-induced force is generated in the liquid in addition to convection, the photo-induced force including at least one of a photo-induced force due to light transmitted through the photothermal conversion material and a photo-induced force due to an evanescent wave induced by light propagating through the optical fiber to the surface of the substrate holding the liquid.

[0018] (13) A method for concentrating minute objects according to a third aspect of the present disclosure concentrates a plurality of minute objects dispersed in a liquid. The method for concentrating minute objects includes the steps of preparing an optical fiber having a tip and positioning the tip at a position where a photoinduced force is generated in the liquid when light is introduced into the optical fiber. The photoinduced force includes at least one of a photoinduced force due to light emitted from the tip and a photoinduced force due to an evanescent wave induced by light propagating through the optical fiber to the surface of a substrate holding the liquid.

[0019] (14) A kit for concentrating minute objects according to a fourth aspect of the present disclosure includes a substrate configured to hold, on a main surface thereof, a liquid in which a plurality of minute objects are dispersed, and an optical fiber having a tip provided with a photothermal conversion material. The optical fiber is configured so that the tip is disposed in the liquid when the liquid is held on the main surface.

[0020] (15) The color of the photothermal conversion material is the color that changes with the change in the power of the light propagating through the optical fiber.

[0021] (16) The tip of the optical fiber is a perfect circle. (17) The optical fiber is a multimode fiber.

[0022] (18) A minute object concentration system according to a fifth aspect of the present disclosure includes an optical fiber, an adjustment mechanism, and a light source. The optical fiber has a first end provided with a photothermal conversion material and a second end. The adjustment mechanism adjusts the position or height of the first end in the liquid while the liquid containing a plurality of minute objects dispersed therein is held in the concentration kit. The light source is optically coupled to the second end and emits light of a wavelength included in the absorption wavelength range of the photothermal conversion material.

[0023] (19) The light source generates microbubbles at the first end by heating the liquid around the first end with light. The system for concentrating micro-objects further includes an imaging device that captures an image of the region between the first end and the microbubbles, and a processor that calculates the concentration number of the multiple micro-objects in the region according to the following equation (1) obtained from the image.

[0024]

number

[0025] In formula (1), N represents the number of micro-objects concentrated. h represents the height of the concentrated region of the micro-objects. r1 represents the distance between the imaginary central axis of the microbubble extending perpendicular to the end face of the first end and the outer periphery of the concentrated region. r3 represents the distance between the central axis and the inner periphery of the concentrated region. r2 represents the distance between the central axis and the part of the concentrated region corresponding to the height. V represents the volume of each of the micro-objects. F represents the packing ratio of the hexagonal close-packed structure.

[0026] (20) The light source generates microbubbles at the first end by heating the liquid around the first end with light. The system for concentrating micro-objects further includes an imaging device that captures an image of the region between the first end and the microbubbles, and a processor that calculates the concentration number of the multiple micro-objects in the region according to the following equation (2) obtained from the image.

[0027]

number

[0028] In equation (2), N represents the number of micro-objects concentrated. h represents the height of the concentrated region of the micro-objects. r1 represents the distance between the imaginary central axis of the microbubble extending perpendicular to the end face of the first end and the outer periphery of the concentrated region. r3 represents the distance between the central axis and the inner periphery of the concentrated region. r2 represents the distance between the central axis and the part of the concentrated region corresponding to the height. V represents the volume of each of the micro-objects. F represents the packing fraction of the hexagonal close-packed structure. [Effects of the Invention]

[0029] According to the present disclosure, minute objects can be concentrated at any location in a liquid. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is an overall configuration diagram of a system for concentrating minute objects according to a first embodiment of the present disclosure. [Figure 2]FIG. 2 is a perspective view schematically showing the configuration of a concentration kit 11 and an optical fiber. [Figure 3] 3 is a cross-sectional view of the concentration kit and the optical fiber taken along line III-III in FIG. 2. [Figure 4] 10 is a flowchart showing the processing procedure of the concentration processing of minute objects in the first embodiment. [Figure 5] 1A to 1C are diagrams for explaining a method for forming a metal thin film. [Figure 6] FIG. 10 shows an image of an actually prepared optical fiber. [Figure 7] 10A and 10B are diagrams for explaining the concentration mechanism of minute objects in the concentration step. [Figure 8] 10 is a diagram showing the change in laser output from the fiber end when a metal thin film is provided / not provided. FIG. [Figure 9] FIG. 10 shows an example of the concentration of minute objects between the fiber end and the microbubbles. [Figure 10] FIG. 1 is a diagram for explaining the influence of a surfactant. [Figure 11] FIG. 10 is a diagram for explaining an example of a method for calculating the concentration number of minute objects. [Figure 12] FIG. 10 is a perspective view of a concentration kit according to a second embodiment. [Figure 13] 13 is a cross-sectional view of the concentration kit taken along line XIII-XIII in FIG. 12. [Figure 14] FIG. 2 is a schematic diagram for explaining the arrangement of fiber ends. [Figure 15] FIG. 10 is a diagram for explaining another example of a method for calculating the concentration number of minute objects. [Figure 16] This is the first figure showing the time series of the concentration results of minute objects when the fiber end is placed at the center of the sample. [Figure 17] This is the second figure showing the time series of the concentration results of minute objects when the fiber end is placed at the center of the sample. [Figure 18] The third figure shows the time series of the concentration results of minute objects when the fiber end is placed at the center of the sample. [Figure 19] FIG. 10 shows an example of the concentration results of minute objects when the fiber end is placed at the center of the sample. [Figure 20] FIG. 11 summarizes the concentration results of minute objects when the fiber end is placed at the center of the sample. [Figure 21] This is a fluorescent observation image showing the concentration of minute objects when the fiber end is placed at the center of the sample. [Figure 22] FIG. 10 shows the concentration efficiency of minute objects when the fiber end is placed at the center of the sample. [Figure 23] FIG. 10 shows an example of the concentration results of minute objects when the fiber end is placed at the bottom of the sample. [Figure 24] FIG. 10 shows a fluorescent observation image of the concentration result of minute objects when the fiber end is placed at the bottom of the sample. [Figure 25] FIG. 10 shows the size dependence of the concentration results of small objects when the fiber end is placed at the bottom of the sample. [Figure 26] FIG. 10 shows the concentration dependence of the concentration results of the minute objects when the fiber end is placed at the bottom of the sample. [Figure 27] FIG. 10 is a diagram showing the analysis results of the flow of thermal convection when the fiber end is placed at the bottom of the sample. [Figure 28] 10A and 10B are diagrams showing the transmittance and extinction rate of laser light when the drive current of the laser light source is changed. [Figure 29] 10A and 10B are diagrams showing images of a fiber end taken before and after a change in the driving current of a laser light source. [Figure 30] 10A and 10B are diagrams showing successive images of the concentration results of minute objects when no metal thin film is formed on the fiber end. [Figure 31] 10A and 10B are diagrams showing successive images of the concentration results of minute objects when a thin metal film is formed on the fiber end. [Figure 32] The first figure shows a time series of fluorescence observation images of bacterial concentration results. [Figure 33] The second figure shows fluorescent observation images of bacterial concentration results arranged in time series. [Figure 34]FIG. 10 is a diagram for comparing fluorescent observation images of the bacterial concentration results before and after irradiation with laser light. [Figure 35] FIG. 10 is a diagram showing the results of observing the state of bacteria after laser light irradiation was stopped. [Figure 36] FIG. 1 shows a fluorescent observation image of the nanodiamond concentration results. [Figure 37] This is a diagram summarizing the three modes of optical concentration. [Figure 38] FIG. 1 is a diagram for explaining the mechanism of long-distance optical concentration. [Figure 39] FIG. 10 is a time series of fluorescent observation images of the photoconcentration results in a comparative example. [Figure 40] FIG. 1 is a first diagram showing fluorescent observation images of the photoconcentration results in this example arranged in time series. [Figure 41] FIG. 2 is a second diagram showing fluorescent observation images of the photoconcentration results in this example arranged in time series. DETAILED DESCRIPTION OF THE INVENTION

[0031] <Terminology> In the present disclosure and embodiments, "nanometer order" includes a range of 1 nm to 1000 nm (= 1 μm). "Micrometer order" includes a range of 1 μm to 1000 μm (= 1 mm). Therefore, "a range from nanometer order to micrometer order" includes a range of 1 nm to 1000 μm. "A range from nanometer order to micrometer order" typically indicates a range of several nm to several hundred μm, preferably a range of 100 nm to 100 μm, and more preferably a range of several hundred nm to several tens of μm.

[0032] In the present disclosure and embodiments, the term "micro object" refers to an object having a size ranging from the nanometer order to the micrometer order. The shape of the micro object is not particularly limited, and may be, for example, a sphere, an ellipsoid, or a rod (bar shape). When the micro object is an ellipsoid, at least one of the length in the major axis direction and the length in the minor axis direction of the ellipsoid may be within the nanometer order to the micrometer order. When the micro object is a rod, at least one of the width and length of the rod may be within the nanometer order to the micrometer order.

[0033] Examples of microscopic objects include metal nanoparticles, metal nanoparticle aggregates, metal nanoparticle-enriched structures, semiconductor nanoparticles, organic nanoparticles, resin beads, and particulate matter (PM). Metal nanoparticles are metal particles with nanometer-order sizes. Metal nanoparticle aggregates are aggregates formed by the aggregation of multiple metal nanoparticles. Metal nanoparticle-enriched structures are structures in which multiple metal nanoparticles are fixed to the surface of a substrate (e.g., resin beads) via interaction sites, with gaps between them spaced at intervals less than the diameter of the metal nanoparticles. Semiconductor nanoparticles are semiconductor particles with nanometer-order sizes. Organic nanoparticles are particles made of organic compounds with nanometer-order sizes. Resin beads are particles made of resin with sizes ranging from nanometers to micrometers. PM is particulate matter with micrometer-order sizes. Examples of PM include PM2.5 and suspended particulate matter (SPM).

[0034] The minute objects may be biological materials (biological materials). More specifically, the minute objects may include cells, microorganisms (bacteria, fungi, etc.), drugs, biopolymers (proteins, nucleic acids, lipids, polysaccharides, etc.), antigens (allergens, etc.), and viruses.

[0035] In the present disclosure and embodiments, the term "microbubbles" refers to air bubbles on the order of micrometers.

[0036] In the present invention and its embodiments, the term "photoinduced force" is used as a general term for dissipative force, gradient force, and inter-substance photoinduced force. Dissipative force is a force generated when the momentum of light is imparted to a substance in a dissipative process such as light scattering or light absorption. Gradient force is a force that moves a substance with photoinduced polarization to a stable point of electromagnetic potential when the substance is placed in a non-uniform electromagnetic field. Inter-substance photoinduced force is the sum of the force due to the longitudinal electric field and the force due to the transverse electric field (radiation field) that arise from the induced polarization in multiple photoexcited substances. Note that photoinduced force may also be interpreted as light pressure (photoinduced force per unit area).

[0037] In the present disclosure and embodiments, the term "visible range" refers to a wavelength range of 360 nm to 760 nm, and the term "near-infrared range" refers to a wavelength range of 760 nm to 2 μm.

[0038] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, identical or corresponding parts are designated by the same reference numerals, and their description will not be repeated. In the following description, the x and y directions represent horizontal directions. The x and y directions are perpendicular to each other. The z direction represents the vertical direction. The direction of gravity is downward in the z direction. The upward z direction may be abbreviated as "upward," and the downward z direction may be abbreviated as "downward."

[0039] [Embodiment 1] <Overall structure> 1 is an overall configuration diagram of a micro-object concentration system according to a first embodiment of the present disclosure. The concentration system 1 includes a concentration kit 11, a sample stage 20, a sample adjustment mechanism 30, a laser light source 40, an optical fiber 50, a fiber stage 60, a fiber adjustment mechanism 70, an illumination light source 81, an objective lens 82, a lens 83, a camera 84, and a controller 100.

[0040] The enrichment kit 11 is configured to hold a sample (denoted by SP), which is a liquid specimen in which a plurality of minute objects are dispersed.

[0041] The sample stage 20 is configured so that the concentration kit 11 can be placed thereon. Although not shown, a large number of concentration kits 11 can be prepared. The large number of concentration kits 11 are placed in turn on the sample stage 20, and the concentration process (see FIG. 4) described below is carried out.

[0042] The sample adjustment mechanism 30 is, for example, an XYZ-axis stage. The sample adjustment mechanism 30 adjusts the horizontal position and vertical height of the sample stage 20 in accordance with commands from the controller 100. This makes it possible to adjust the relative positional relationship between the concentration kit 11 and the objective lens 82, and the relative positional relationship between the concentration kit 11 and the optical fiber 50.

[0043] The laser light source 40 emits a continuous wave (CW) laser light in accordance with a command from the controller 100. The wavelength of the laser light is included in the absorption wavelength range of a metal thin film 52 (described later) formed on the concentration kit 11, and is, for example, a wavelength in the near-infrared range.

[0044] The optical fiber 50 guides the laser light emitted from the laser light source 40 to the sample on the concentration kit 11. The configurations of the concentration kit 11 and the optical fiber 50 will be described in detail with reference to FIGS.

[0045] The fiber stage 60 is configured so that the optical fiber 50 can be installed thereon. Note that the optical fiber 50 is a consumable item because it can be damaged or contaminated. Therefore, it is desirable that the fiber stage 60 be configured so that the optical fiber 50 can be easily replaced.

[0046] The fiber adjustment mechanism 70 is, for example, an XYZ axis stage. The fiber adjustment mechanism 70 adjusts the position and height of the optical fiber 50 in accordance with instructions from the controller 100.

[0047] 1 can adjust the relative positional relationship between the enrichment kit 11 and the optical fiber 50 using either the sample adjustment mechanism 30 or the fiber adjustment mechanism 70. Therefore, both the sample adjustment mechanism 30 and the fiber adjustment mechanism 70 correspond to the "adjustment mechanism" according to the present disclosure. However, the enrichment system 1 may be configured to include only one of the sample adjustment mechanism 30 and the fiber adjustment mechanism 70.

[0048] The illumination light source 81 emits white light to illuminate the sample on the enrichment kit 11. As one example, a halogen lamp can be used as the illumination light source 81. The white light emitted from the illumination light source 81 passes through the sample. The objective lens 82 captures the white light that has passed through the sample. The lens 83 collects the white light captured by the objective lens 82 and directs it to the camera 84.

[0049] The camera 84 includes, for example, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The camera 84 photographs the sample on the enrichment kit 11 in accordance with instructions from the controller 100 and outputs the photographed image to the controller 100. The image photographed by the camera 84 may be a still image or a video. The camera 84 corresponds to the "photographing device" according to the present disclosure.

[0050] The controller 100 includes a processor 101 such as a CPU (Central Processing Unit), a memory 102 such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and an input / output port 103 through which various signals are input and output. The controller 100 controls each device in the concentration system 1 (the sample adjustment mechanism 30, the laser light source 40, the fiber adjustment mechanism 70, the illumination light source 81, and the camera 84). The controller 100 also calculates the number of micro-objects concentrated in the sample based on an image captured by the camera 84. The calculation method will be described later.

[0051] The optical system (illumination light source 81, objective lens 82, lens 83, and camera 84) for photographing the sample on the concentration kit 11 is merely an example. The optical system of the concentration system 1 may be configured, for example, so that white light from the illumination light source 81 irradiates the sample from below, and the camera 84 photographs the sample from above. The optical system of the concentration system 1 may include other optical components (mirrors, dichroic mirrors, beam splitters, filters, optical fibers, etc.) instead of or in addition to the objective lens 82 and lens 83.

[0052] <Concentration kit and optical fiber> Fig. 2 is a perspective view schematically showing the configuration of the concentration kit 11 and the optical fiber 50. Fig. 3 is a cross-sectional view of the concentration kit 11 and the optical fiber 50 taken along line III-III in Fig. 2. Note that the sample stage 20 and the fiber stage 60 are omitted from Figs. 2 and 3.

[0053] The sample is, for example, a liquid specimen in which resin beads (denoted by R) are dispersed. In the examples described below, polystyrene particles are used as the resin beads. The type of liquid (dispersion medium) is not particularly limited, but in this example it is water. A nonionic surfactant is added to the sample to promote concentration of the resin beads (see Figure 10).

[0054] In the first embodiment, the enrichment kit 11 is a flat substrate. The enrichment kit 11 holds a sample on its upper surface (main surface) 111. The enrichment kit 11 is made of a material that is transparent to white light. Examples of such materials include quartz and silicone. In this example, a glass substrate (cover glass) is used as the enrichment kit 11.

[0055] The concentration kit 11 may be a three-dimensional container having an internal space for holding a sample. Specifically, a cylindrical glass bottom dish may be used as the concentration kit 11.

[0056] One end (first end) 501 of the optical fiber 50 is disposed in the sample. The other end (second end) of the optical fiber 50 is optically coupled to the laser light source 40 (see FIG. 1). The optical fiber 50 is preferably a multimode fiber, and guides the laser light incident from the second end to the first end by propagating it in multiple modes. The optical fiber 50 includes a propagation path 51 and a metal thin film 52.

[0057] The phrase "the tip of the optical fiber 50 is disposed in the sample" includes, but is not limited to, a state in which the entire tip of the optical fiber 50 is contained in the sample as shown in Figures 2 and 3. The phrase "the tip of the optical fiber 50 is disposed in the sample" also includes a state in which the tip of the optical fiber 50 is located at the gas-liquid interface (the interface between the sample and the surrounding gas).

[0058] The propagation path 51 includes a core and a clad (neither of which is shown), and may be made of silica glass or plastic.

[0059] The metal thin film 52 is formed so as to cover the propagation path 51. While FIG. 3 shows an example in which the metal thin film 52 is formed on both the tip (first end) 501 and the side surface of the optical fiber 50, it is sufficient that the metal thin film 52 is formed at least on the tip of the optical fiber 50. The metal thin film 52 absorbs the laser light from the laser light source 40 and converts the light energy into thermal energy. More specifically, free electrons on the surface of the metal thin film 52 form surface plasmons, which are vibrated by the laser light. This causes polarization. The polarization energy is converted into lattice vibration energy by the Coulomb interaction between the free electrons and atomic nuclei. As a result, the metal thin film 52 generates heat. This effect is also called the "photothermal effect."

[0060] The material of metal thin film 52 is preferably a material that has a large photothermal effect in the wavelength range of the laser light (in other words, a high photothermal conversion efficiency). In the present embodiment, a gold thin film is formed as metal thin film 52. However, the material of metal thin film 52 is not limited to gold, and may be a metal element other than gold that can produce a photothermal effect (for example, silver), or a metal nanoparticle assembly structure that can produce a photothermal effect (such as a structure in which gold nanoparticles or silver nanoparticles are assembled).

[0061] The thickness of the metal thin film 52 is determined by design or experimentation, taking into consideration the wavelength of the laser light, the power of the laser light (laser output), the material properties of the metal thin film 52 (absorption wavelength range and photothermal conversion efficiency), etc. When the wavelength of the laser light is within the near-infrared range and the laser output is several hundred mW, the thickness of the metal thin film 52 may be determined to be on the order of nanometers. In an example described below, when the center wavelength of the laser light is 980 nm and the laser output is 200 mW to 500 mW, the thickness of the metal thin film 52 is determined to be 10 nm.

[0062] Hereinafter, the tip (first end) 501 of the optical fiber 50 will also be referred to as the "fiber end 501." Furthermore, the height of the fiber end 501 relative to the upper surface 111 of the enrichment kit 11 will be referred to as "H." The height H can be set to any value by the controller 100 controlling the sample adjustment mechanism 30 and / or the fiber adjustment mechanism 70.

[0063] The position of the fiber end 501 may be fixed so that the fiber end 501 is located in the sample when the sample is held on the upper surface 111. For example, the enrichment kit 11 may include a holder (not shown) for the optical fiber 50. The holder is placed on the upper surface 111 and fixes the position and height of the fiber end 501 to a preset value.

[0064] 2 and 3, the optical fiber 50 is inserted horizontally into the sample. This is because the optical system for photographing the sample is constructed vertically (see FIG. 1), and it is easier to photograph the fiber end 501 when the optical fiber 50 is inserted horizontally. The insertion direction of the optical fiber 50 is not limited to the horizontal direction. The optical fiber 50 can be inserted into the sample from any direction, such as vertically or obliquely.

[0065] <Flowchart> 4 is a flowchart showing the processing steps of the concentration process for minute objects in embodiment 1. The series of processes shown in this flowchart is called from a main routine (not shown) and executed when a predetermined condition is met (for example, when the concentration system 1 receives a start operation from the measurer). Each step is basically realized by software processing by the controller 100, but may also be realized by hardware (electrical circuitry) arranged within the controller 100. Hereinafter, step will be abbreviated as S.

[0066] In S1, the optical fiber 50 is prepared. For example, the optical fiber 50 can be prepared by a measurer performing pre-processing to form a thin metal film 52 on an unprocessed optical fiber. Dedicated optical fibers 50 with the thin metal film 52 provided on the tip may also be sold commercially.

[0067] FIG. 5 is a diagram illustrating a method for forming the metal thin film 52. FIG. 5 shows a top view (upper view) and a cross-sectional view (lower view) illustrating the state during the formation of the metal thin film 52. First, the coating is removed from the tip (first end) of the propagation path 51. Then, the propagation path 51 is fixed on a slide glass 91 so that a small portion (e.g., 1 to 2 cm) of the removed coating is exposed. Then, the metal thin film 52 (a gold thin film in this example) is formed on the exposed portion by ion sputtering. The metal thin film 52 can also be formed using other known techniques, such as electroless plating. Then, the other tip (second end) is optically coupled to an optical connector (e.g., an FC / PC connector). FIG. 6 shows an image of an actually prepared optical fiber 50.

[0068] Instead of the metal thin film 52, a material other than metal that has a high light absorption rate at the wavelength of the laser light may be disposed at the tip of the optical fiber 50. An example of such a material is a material similar to a blackbody (for example, a carbon nanotube blackbody). The region where the metal thin film 52 is formed and the region where the carbon nanotube blackbody or the like is disposed correspond to the "photothermal conversion region" according to the present disclosure.

[0069] Returning to Figure 4, in S2, a sample with dispersed micro-objects is prepared. As will be described in detail later, it is desirable to introduce a surfactant into the sample (S3). The sample prepared in S2 and S3 is stored in a sample supply unit (e.g., a dispenser) not shown. The processes in S2 and S3 are performed by the operator.

[0070] In S4, the controller 100 places the concentration kit 11 on the sample stage 20. This process can be achieved, for example, by a feed mechanism (not shown) for the concentration kit 11. Furthermore, the controller 100 controls a sample supply unit (not shown) to drip the sample so that an appropriate amount of sample is held on the upper surface 111 of the concentration kit 11, as shown in FIGS. 2 and 3. The amount of sample dripped may be a very small amount, for example, on the order of several tens to several hundreds of μL, or may be a larger amount.

[0071] In S5, the controller 100 starts photographing the sample. That is, the controller 100 controls the illumination light source 81 to emit white light for irradiating the sample on the concentration kit 11, and controls the camera 84 to start photographing the sample.

[0072] In S6, the controller 100 controls the sample adjustment mechanism 30 to adjust the position and height of the sample stage 20 to a position and height suitable for image capture by the camera 84. This process can be achieved by the controller 100 processing the image captured by the camera 84. For example, the controller 100 can adjust the position of the sample stage 20 so that the sample is positioned near the center of the image, and can also adjust the height of the sample stage 20 so that the sample is in focus. This process may also be performed manually by the operator.

[0073] In S7, the controller 100 controls the fiber adjustment mechanism 70 to adjust the position and height of the fiber end 501 in the sample. The position adjustment of the fiber end 501 can be achieved, for example, by extracting the fiber end 501 from an image captured by the camera 84 using a pattern recognition image processing technique. The initial value H0 of the height H of the fiber end 501 is a known value that was set when the optical fiber 50 was installed on the fiber stage 60. Therefore, the height adjustment of the fiber end 501 can be achieved by adding the amount of change ΔH in the height direction caused by the fiber adjustment mechanism 70 to the initial value H0. The amount of change ΔH is not limited to a positive value and can also be a negative value. The controller 100 may adjust the position and height of the fiber end 501 by controlling the sample adjustment mechanism 30 instead of the fiber adjustment mechanism 70.

[0074] In S8, the controller 100 controls the laser light source 40 to start irradiating the sample with laser light.

[0075] In S9, a concentration step is performed to concentrate the minute objects near the fiber end 501. The concentration step will be described in detail with reference to FIGS.

[0076] In S10, the controller 100 controls the laser light source 40 to stop irradiating the sample with laser light.

[0077] In S11, the controller 100 ends the photographing of the sample. That is, the controller 100 controls the illumination light source 81 to stop emitting white light, and controls the camera 84 to stop photographing the sample.

[0078] In S12, the controller 100 calculates the concentration number of minute objects near the fiber end 501 based on the image captured by the camera 84. This calculation method will be described with reference to Fig. 11. This completes the series of processes.

[0079] The steps S5, S6, and S11 are for capturing images of the minute objects being concentrated, and are not essential for the concentration of minute objects. The minute objects can be concentrated even when a flowchart that does not include the steps S5, S6, and S11 is executed.

[0080] <Mechanism> 7 is a diagram for explaining the concentration mechanism of minute objects in the concentration step (the process of S9 in FIG. 4). A metal thin film 52 is formed on the fiber end 501. Therefore, when irradiation of laser light begins, the photothermal effect of the metal thin film 52 locally heats the periphery (vicinity) of the fiber end 501. This causes the dispersion medium (water in this example) around the fiber end 501 to boil, generating microbubbles (denoted by MB) at the fiber end 501. The microbubbles grow over time.

[0081] In addition to microbubbles, regular thermal convection steadily occurs in the dispersion medium upon irradiation with laser light. The thermal convection may include buoyancy convection and Marangoni convection. For details on the reason why thermal convection occurs, refer to Patent Documents 1 and 2.

[0082] The direction of the thermal convection, as shown by the arrows in the figure, is first toward the fiber end 501 and then away from the fiber end 501. The minute objects are transported by the thermal convection toward the fiber end 501 and are captured by the microbubbles. More specifically, a "stagnation region," where the flow rate of the thermal convection is approximately zero, is formed between the microbubbles and the fiber end 501. As a result of the minute objects transported by the thermal convection being captured in the stagnation region, the minute objects are concentrated near the fiber end 501. The microbubbles function as stoppers that block the minute objects, thereby becoming an accumulation site for the minute objects.

[0083] The action of concentrating minute objects dispersed in a sample near the fiber end 501 according to the above mechanism can also be called "optical concentration." Note that "concentration" of minute objects means that the concentration of minute objects around the fiber end 501 becomes higher than the concentration of minute objects in other regions of the sample. Micro-objects can also be said to be concentrated when they accumulate in a stagnant region. As will be explained later in the second embodiment, the generation of microbubbles is not essential for optical concentration. Even if microbubbles are not generated, minute objects can be concentrated near the fiber end 501 by thermal convection.

[0084] The action of accumulating micro-objects by optical concentration at accumulation sites such as the solid-liquid interface between the fiber end 501 and the dispersion medium, the gas-liquid interface between the microbubbles and the dispersion medium, and the three-phase boundary of solid-liquid-gas may also be called "optical accumulation."

[0085] Controller 100 can move fiber end 501 to any position and height in the sample by controlling at least one of sample adjustment mechanism 30 and fiber adjustment mechanism 70. Therefore, according to this embodiment, minute objects can be concentrated at any location in the sample.

[0086] [Example 1] <Laser light extinction> 8 is a diagram showing the change in laser output from the fiber end 501 when the metal thin film 52 is provided / not provided. The horizontal axis represents the drive current supplied to the laser light source 40. The vertical axis represents the laser output (the power of the laser light introduced from the laser light source 40 into the optical fiber 50, propagated through the optical fiber 50, and output from the fiber end 501).

[0087] For comparison, Figure 8 shows the measurement results (see the solid line) for a configuration in which the metal thin film 52 is formed on the fiber end 501, as well as the measurement results (see the dashed line) for a configuration in which the metal thin film 52 is not formed on the fiber end 501. The difference in laser output between these two measurement results corresponds to the amount of laser light extinction (= absorption amount + reflection amount) by the metal thin film 52. This difference can be said to be evidence that the metal thin film 52 has been formed on the fiber end 501 (that is, the film formation has been successful).

[0088] In the current range of 500 mA to 700 mA, the extinction rate of the laser light was high, at approximately 20%. The extinction rate is the ratio of the amount of laser light extinction to the laser output in a configuration in which the metal thin film 52 is not formed on the fiber end 501. Since the photoheating effect of the metal thin film 52 depends on the amount of laser light absorbed, the higher the extinction rate of the laser light, the more efficiently microbubbles can be generated. In fact, it was confirmed that microbubbles are easily generated and grow within this current range.

[0089] [Example 2] <Concentration of polystyrene particles> FIG. 9 shows an example of the concentration of minute objects between the fiber end 501 and the microbubbles. Polystyrene particles with a diameter of 1 μm were used as the minute objects. The concentration of polystyrene particles in the sample was 4.55×10 7 The sample volume was 20 μL. The driving current of the laser light source 40 was set to 700 mA. The irradiation time of the laser light was 60 seconds. The diameter of the optical fiber 50 was 125 μm. In this measurement and the measurements described below, the driving current of 700 mA was set to a laser output of 401 μm. m A drive current of 600 mA corresponds to a laser output of 344 mW, and a drive current of 500 mA corresponds to a laser output of 287 mW.

[0090] Microbubbles larger than the diameter of fiber end 501 were generated at fiber end 501. It was also confirmed that polystyrene particles were concentrated (accumulated) between fiber end 501 and the microbubbles.

[0091] 9, it is desirable that the fiber end 501 is formed perpendicular to the side surface of the optical fiber 50. In other words, it is desirable that the shape of the fiber end 501 (cross-sectional shape perpendicular to the side surface) is a perfect circle rather than an ellipse. This allows the microbubbles to be stably held at the fiber end 501.

[0092] [Example 3] <Effect of surfactants> FIG. 10 is a diagram for explaining the influence of a surfactant. The measurement conditions are the same as those explained in FIG. 9. Tween 20 was used as the surfactant. The concentration of the surfactant was 9.05×10 -5 This concentration is close to the critical micelle concentration of Tween 20.

[0093] When the sample did not contain a surfactant (left graph), the number of concentrated polystyrene particles was lower than when the sample contained a surfactant (right graph). This is thought to be because when a surfactant was not included, the microbubbles were too large and the flow rate of the thermal convection was too fast. If the microbubbles were too large, the stagnation region that occurs between the fiber end 501 and the microbubbles and contributes to the capture of micro-objects would become smaller. Also, if the flow rate of the thermal convection was too fast, the polystyrene particles would be less likely to be captured in the stagnation region. This is thought to result in a lower number of concentrated polystyrene particles.

[0094] Surfactants suppress the growth of microbubbles by adsorbing to their surfaces, and also suppress the flow rate of Marangoni convection by reducing the surface tension of the microbubbles. Therefore, introducing surfactants into a sample can suppress excessive microbubble growth and moderately suppress the flow rate of thermal convection, thereby promoting the concentration of polystyrene particles in stagnation regions. In particular, adjusting the surfactant concentration to the critical micelle concentration (or a concentration close to it) can further promote the concentration of polystyrene particles.

[0095] [Example 4] <Calculating the concentration number> FIG. 11 is a diagram illustrating an example of a method for calculating the concentration number of minute objects. In this method, it is assumed that each minute object is spherical. Furthermore, it is assumed that in the region where the minute objects are concentrated and whose cross section is a truncated cone, the minute objects have a hexagonal close-packed structure. According to this geometric model, the concentration number N of minute objects is calculated according to the following formula (1).

[0096]

number

[0097] In equation (1), h represents the height of the micro-object enrichment region. r1 represents the distance between the central axis of the microbubble (denoted by AX) and the outer periphery of the enrichment region. The central axis of the microbubble is an imaginary axis extending perpendicular to the end face of the optical fiber 50. r2 represents the distance between the central axis of the microbubble and the highest part of the enrichment region. r3 represents the distance between the central axis of the microbubble and the inner periphery of the enrichment region. V represents the volume of each micro-object, a value known from the specifications of the micro-object. F is the packing fraction of the hexagonal close-packed structure, which is approximately 0.74.

[0098] The concentration number N of polystyrene particles in the measurement examples shown in Figures 8 to 10 was calculated according to formula (1) to be N = 24785 ± 3212 [particles]. From this, the concentration efficiency of polystyrene particles was calculated to be 2.7 ± 0.4%. The concentration efficiency is the ratio of the concentration number N of polystyrene particles to the total number of polystyrene particles in a sample. The concentration efficiency of 2.7% is more than one order of magnitude higher than the concentration efficiency of 0.15% described in Patent Document 1. Therefore, it can be said that according to embodiment 1, polystyrene particles were concentrated with high efficiency.

[0099] As described above, in the first embodiment, minute objects are concentrated near the tip of the optical fiber 50 by utilizing the photothermal effect of the metal thin film 52 formed at the tip of the optical fiber 50. The tip of the optical fiber 50 can be adjusted to any position and / or height within the sample. Therefore, according to the first embodiment, minute objects can be concentrated at any location within the sample. In addition, a significantly higher concentration efficiency of minute objects can be achieved compared to the configurations of Patent Documents 1 and 2.

[0100] [Embodiment 2] In the first embodiment, the concentration kit 11 is described as having a flat plate shape (see FIGS. 2 and 3). The concentration kit 11 can be said to have an "open system" structure in that the sample is open to the atmosphere. In the second embodiment, an example in which the concentration kit has a "closed system" structure will be described.

[0101] The overall configuration of the minute object concentration system according to embodiment 2 is the same as the overall configuration of the minute object concentration system 1 according to embodiment 1 (see FIG. 1). The processing procedure for the minute object concentration process according to embodiment 2 is basically the same as the processing procedure according to embodiment 1 (see FIG. 4). Therefore, detailed description thereof will not be repeated.

[0102] <Concentrated kit> Fig. 12 is a perspective view of a concentration kit according to embodiment 2. Fig. 13 is a cross-sectional view of the concentration kit taken along line XIII-XIII in Fig. 12. Referring to Figs. 12 and 13, concentration kit 12 not only holds a sample but is also configured to sandwich the sample from above and below in the vertical direction. Concentration kit 12 includes a substrate 121, a cover 122, and a spacer 123.

[0103] The substrate 121 is placed below the sample to hold the sample. The material of the substrate 121 is a material that is transparent to white light (glass, quartz, silicone, etc.). In this example, a glass substrate (cover glass) is used as the substrate 121.

[0104] The cover 122 covers the sample held on the substrate 121 from above. The cover 122 is made of a material that is transparent to white light, similar to the material of the substrate 121. In this example, the cover 122 is also made of a glass substrate.

[0105] The spacer 123 is disposed between the substrate 121 and the cover 122. The spacer 123 fixes the cover 122 to the substrate 121 and maintains the distance between the substrate 121 and the cover 122 at a set value. In this example, double-sided tape is used for the spacer 123. However, the material of the spacer 123 is not particularly limited, and other materials such as resin, rubber, glass, quartz, and silicone may also be used.

[0106] The spacer 123 can also function as a holder that fixes the position and height of the fiber end 501 at preset values. For example, the spacer 123 can be provided with a fine groove or through-hole through which the optical fiber 50 passes. This allows the enrichment kit 12 to be configured so that the fiber end 501 is positioned in the sample when the sample is held on the substrate 121.

[0107] Hereinafter, the distance between substrate 121 and cover 122 (i.e., the sample height) will be referred to as "D." Height H of fiber end 501 can be adjusted to any value within the range from 0 to D (0≦H≦D).

[0108] [Example 5] <Fiber end placement> The results of evaluating the effect of the arrangement of the fiber end 501 (specifically, the height H) on the concentration of minute objects will be described.

[0109] Fig. 14 is a schematic diagram for explaining the arrangement of the fiber end 501. As shown in Fig. 14, the concentration results of minute objects were compared when the fiber end 501 was arranged in the center of the sample (when H = D / 2) and when the fiber end 501 was arranged at the bottom of the sample (when H = 0). The sample height was D = 860 μm.

[0110] When the fiber end 501 is placed at the center of the sample, the propagation path of the optical fiber 50 does not contact the substrate 11, and therefore this arrangement is also referred to as a "non-contact arrangement." On the other hand, when the fiber end 501 is placed at the bottom of the sample, the propagation path of the optical fiber 50 contacts the substrate 11, and therefore this arrangement is also referred to as a "contact arrangement."

[0111] Figure 15 is a diagram for explaining another example of a method for calculating the concentration number of minute objects. In the following measurement example, the shape of the concentration region of minute objects was different from the shape shown in Figure 11, so the geometric model for calculating the concentration number N of minute objects was also changed. Specifically, the concentration number N of minute objects was calculated according to the following formula (2).

[0112]

number

[0113] ≪Non-contact placement≫ 16 to 18 are diagrams showing, in chronological order, the concentration results of minute objects when the fiber end 501 is placed at the center of the sample (non-contact placement). The concentration results of minute objects when the drive current of the laser light source 40 is different are shown. FIG. 19 is a diagram for comparing the concentration results of minute objects when the fiber end 501 is placed at the center of the sample. FIG. 19 shows an image taken 60 seconds after the start of laser light irradiation. FIG. 20 is a diagram summarizing the concentration results of minute objects when the fiber end 501 is placed at the center of the sample.

[0114] The driving current of the laser light source 40 was set to 700 mA (laser output 401 mW), 600 mA (laser output 344 mW), or 500 mA (laser output 287 mW). Polystyrene particles with a diameter of 1 μm were used. The concentration of the polystyrene particles was 4.55 × 10 6 ~4.55×10 8 The range of [particles / mL] was set. The sample volume was 20 μL. Tween 20 was used as the surfactant. The surfactant concentration was 0 to 9.05 × 10 -5 The range of M was prepared.

[0115] 16 to 20, when the driving current was set to 500 mA (sample numbers 6 to 8) or 600 mA (sample number 5), the concentration efficiency of polystyrene particles was lower than when the driving current was set to 700 mA (sample numbers 2 to 4). Furthermore, when no surfactant was introduced (sample number 1), the polystyrene particles were not concentrated even at a driving current of 700 mA.

[0116] Samples 2 to 4 share a driving current of 700 mA and a polystyrene particle concentration of 4.55 × 10 7While the [particles / mL] was the same for all samples, the surfactant concentrations were different. The concentration efficiencies of samples 2 to 4 were all about two orders of magnitude higher than the concentration efficiency (0.15%) described in Patent Document 1. Among them, sample 3, which had an intermediate surfactant concentration, had the highest concentration efficiency and the smallest variation in concentration efficiency. Sample 2, which had the lowest surfactant concentration, and sample 4, which had the highest surfactant concentration, both had sufficiently high concentration efficiencies, but the variation in concentration efficiency was relatively large.

[0117] The larger the driving current, the faster the flow rate of thermal convection (buoyancy convection and Marangoni convection) occurring in the sample. On the other hand, the higher the surfactant concentration, the more the growth of microbubbles is suppressed and the flow rate of thermal convection (particularly Marangoni convection) is suppressed. By optimizing the combination of the driving current magnitude and surfactant concentration, it is possible to adjust the size of microbubbles and the flow rate of thermal convection to a flow rate suitable for concentrating micro-objects, thereby achieving high and consistent concentration efficiency.

[0118] 21 is a fluorescent observation image showing the concentration of minute objects when the fiber end 501 is placed at the center of the sample (non-contact placement). The concentration of polystyrene particles with a diameter of 1 μm is 4.55×10 7 [particles / mL]. The concentration of Tween 20 was 5.43 × 10 -5 The laser output was set to 390 mW. The light irradiation time was 60 seconds. In the non-contact configuration, it can be seen that polystyrene particles are concentrated at the fiber end 501 (more specifically, at the three-phase boundary between the fiber end 501 (solid phase), the sample (liquid phase), and the microbubbles (gas phase)).

[0119] Figure 22 shows the concentration efficiency of minute objects when the fiber end 501 is placed at the center of the sample (non-contact placement). The measurement conditions are the same as those in Figure 21, except that the concentration of polystyrene particles was set to various values. The horizontal axis represents the concentration of polystyrene particles. The vertical axis represents the concentration efficiency of polystyrene particles. The lower the concentration of polystyrene particles, the higher the concentration efficiency. At the lowest concentration, a concentration efficiency of 11.6% was achieved.

[0120] ≪Contact arrangement≫ Figure 23 shows an example of the concentration results of minute objects when the fiber end 501 is placed on the bottom of the sample (contact placement). The driving current of the laser light source 40 was set to 700 mA, 600 mA, or 500 mA. Polystyrene particles with a diameter of 1 μm were used. The concentration of the polystyrene particles was 4.55 × 10 8 The sample volume was 20 μL. Tween 20 was used as the surfactant. The surfactant concentration was 5.43 × 10 -5 Prepared to M.

[0121] In the contact configuration, regardless of the driving current, the polystyrene particles were concentrated on the side of the optical fiber 50 (hereinafter referred to as "fiber side surface 502") rather than between the fiber end 501 and the microbubbles. This is presumably because, in the contact configuration, the substrate 121 located near the fiber end 501 causes thermal convection that differs from that in the non-contact configuration.

[0122] The temperature of the sample on the fiber side surface 502 is lower than that of the sample on the fiber end 501. Therefore, the contact arrangement is considered suitable for concentrating thermally sensitive microscopic objects (biological materials such as drugs and biopolymers). For example, by placing a cell near the fiber side surface 502 and optically concentrating a drug on the fiber side surface 502, it becomes possible to introduce the optically concentrated drug into the cell.

[0123] Figure 24 shows a fluorescent observation image of the concentration of minute objects when the fiber end 501 is placed on the bottom of the sample (contact placement). Four samples with different sizes and concentrations of polystyrene particles were prepared. The concentration of polystyrene particles (NYO) with a diameter of 500 nm was 3.64 x 10 8 The concentration of 1 μm diameter polystyrene particles (YG) was 4.55 × 10 7 The concentration of 2 μm diameter polystyrene particles (YG) was 4.55 × 10 7 [particles / mL] or 5.69 × 10 6 [particles / mL]. The concentration of Tween 20 was 5.43 × 10 -5 The laser power was set to 320 mW. The irradiation time was 60 seconds.

[0124] 24 shows that in the contact arrangement, polystyrene particles are concentrated on a large scale not only at the fiber end 501 but also at the fiber side surface 502. In the non-contact arrangement, polystyrene particles are concentrated at the optical fiber 50 (fiber end 501) (see FIG. 21), whereas in the contact arrangement, polystyrene particles are concentrated at a position relatively far from the optical fiber 50. In the contact arrangement, the region where polystyrene particles are concentrated is a region that is a distance from the fiber side surface 502 that is approximately the same as the diameter of the optical fiber 50 (125 μm in this example).

[0125] 25 shows the size dependence of the concentration results of minute objects when the fiber end 501 is placed on the bottom of the sample (contact placement). The horizontal axis represents the diameter of the polystyrene particles. The upper vertical axis represents the concentration number of polystyrene particles, and the lower vertical axis represents the concentration efficiency of the polystyrene particles.

[0126] The concentration of polystyrene particles (YG) with a diameter of 500 nm is 3.69 × 10 8 The concentration of 1 μm diameter polystyrene particles (YG) was 4.55 × 10 7The concentration of 2 μm diameter polystyrene particles (YG) was 4.55 × 10 7 The volume ratio of a single polystyrene particle among these three samples was calculated to be 500 μm:1 μm:2 μm = 0.125:1:8. Meanwhile, the concentration ratio of polystyrene particles in the samples was calculated to be 500 μm:1 μm:2 μm = 8.01:1:0.081. Therefore, the volume ratio of all polystyrene particles in the three samples was approximately the same.

[0127] The smaller the diameter of the polystyrene particles, the higher the enrichment number, but the lower the enrichment efficiency. This indicates that, when the volume ratio of all polystyrene particles in the sample is equal, the larger the diameter of the polystyrene particles, the higher the enrichment efficiency. In other words, large-sized particles can be enriched efficiently.

[0128] 26 is a graph showing the concentration dependence of the concentration results of minute objects when the fiber end 501 is placed on the bottom of the sample (contact placement). The horizontal axis represents the concentration of polystyrene particles. The upper vertical axis represents the number of concentrated polystyrene particles, and the lower vertical axis represents the concentration efficiency of polystyrene particles.

[0129] Polystyrene particles (YG) with a diameter of 2 μm were used. The concentration of polystyrene particles in one of the two samples was 5.68 × 10 6 The concentration of polystyrene particles in the other sample was 4.55 × 10 7 [particles / mL].

[0130] The concentration efficiency was higher at lower polystyrene particle concentrations, possibly because at higher concentrations, the accumulation sites around the microbubbles become saturated with accumulated polystyrene particles, making further accumulation difficult.

[0131] <Flow field analysis> 27 is a diagram showing the analysis results of the flow of thermal convection when the fiber end 501 is placed on the bottom of the sample (contact placement). 6 A sample containing polystyrene particles of [particles / mL] was used. Flow field analysis was performed using particle tracking to determine the flow velocity of thermal convection at the six locations shown in Figure 27.

[0132] The flow velocity at the fiber side surface 502 ( E and F ) is the flow velocity ( A ~ D ) This is one piece of evidence that, in the contact configuration, a stagnation region occurs on the fiber side surface 502, which becomes an accumulation site. Note that, in addition to thermal convection, the driving force for condensing the polystyrene particles on the fiber side surface 502 may also be due to capillary action occurring between the optical fiber 50 and the condensation kit 11 (cover glass in this example) and / or thermophoresis due to the temperature gradient generated at the fiber end 501.

[0133] [Example 6] <Changes in the properties of metal thin films> The influence of the change in the characteristics of the metal thin film formed on the fiber end 501 will be described.

[0134] 28 is a diagram showing the transmittance and extinction rate of laser light when the drive current of the laser light source 40 is changed. The horizontal axis represents the drive current of the laser light source 40. The vertical axis in the upper diagram represents the transmittance of the fiber end 501. The vertical axis in the lower diagram represents the extinction rate of the fiber end 501. The extinction rate satisfies the relational expression: extinction rate = absorptance + reflectance = 100% - transmittance.

[0135] In the measurements shown in Figure 28, the drive current was increased from 50 mA to 700 mA in 50 mA increments, and then decreased from 700 mA to 50 mA in 50 mA increments. The time interval between changes in the drive current was 10 seconds. As a result, the transmittance and extinction rate were different when the drive current was increased and then decreased. In other words, hysteresis occurred in the transmittance and extinction rate. In particular, when the drive current was increased and then decreased, the extinction rate at the fiber end 501 remained constant at approximately 20%.

[0136] Figure 29 shows images of the fiber end 501 taken before and after changing the drive current of the laser light source 40. The fiber end 501 has a flat end surface. Although it is somewhat difficult to see in the black and white image, a color change in the fiber end 501 was observed when the drive current was in the range of 150 mA to 350 mA as the drive current was gradually increased. The color change in the fiber end 501 was observed over a wide area, including the fiber end 501 and the fiber side surface 502. This suggests that the properties of the metal thin film 52 (in this example, the gold thin film) may have changed over a wide area. The mechanism behind the change in the properties of the metal thin film 52 is not clear at this stage, but a photothermal effect is thought to be one possible cause.

[0137] According to the results shown in Figures 28 and 29, a process of increasing the drive current before decreasing it can be added as a pre-processing step for the concentration step (processing S9 in Figure 4). This makes it possible to actively cause changes in the characteristics of the optical fiber 50 (fiber end 501 and fiber side surface 502). By causing changes in the characteristics of the optical fiber 50 in advance and stabilizing the characteristics, it is possible to suppress changes in characteristics that can occur when the drive current is changed during the concentration step (i.e., when the output of light propagating through the optical fiber 50 is changed). This makes it possible to fix the optical conditions for concentrating minute objects. Therefore, for example, when performing the concentration step on multiple samples, the conditions can be standardized between samples.

[0138] When microbubbles grow on the bottom surface of a container or the main surface of a substrate, as in Patent Documents 1 and 2, the size of the microbubbles may vary from measurement to measurement. In contrast, when microbubbles grow at the fiber end 501, the size of the microbubbles may depend on the diameter of the optical fiber 50 (the area of ​​the fiber end 501). Because the diameter of the optical fiber 50 is a fixed value (125 μm in this example) according to the specifications of the optical fiber 50, the use of the optical fiber 50 can reduce the variation in the size of the microbubbles. This also helps standardize the conditions between samples when performing a concentration process on multiple samples.

[0139] Fig. 30 shows a series of images of the concentration result of minute objects when no metal thin film 52 is formed on the fiber end 501. Fig. 31 shows a series of images of the concentration result of minute objects when a metal thin film 52 is formed on the fiber end 501. Fig. 31 shows the concentration result after adding a process that changes the properties of the metal thin film 52.

[0140] Polystyrene particles with a diameter of 1 μm were used as the micro-objects. The concentration of the polystyrene particles was 4.55 × 10 7 The sample volume was 20 μL. The driving current was set to 700 mA. The laser light irradiation time was set to 60 seconds. Tween 20 was used as the surfactant. The surfactant concentration was 5.43 × 10 -5 It was M.

[0141] When the metal thin film 52 was not formed, the polystyrene particles simply moved at a slow speed due to the photoinduced force generated by the irradiation of the laser light, and no thermal convection occurred. Therefore, photocondensation of the polystyrene particles did not occur (see FIG. 30). On the other hand, when the metal thin film 52 was formed, although microbubbles were not generated, the polystyrene particles were transported at high speed toward the fiber end 501 due to the photoinduced force (more specifically, the dissipation force) and the thermal convection, and were concentrated in front of the fiber end 501 (see FIG. 31).

[0142] The reason why microbubbles were not generated in the measurement shown in Figure 31 is thought to be because the temperature rise caused by laser light irradiation was relatively small. By carrying out the concentration process under these conditions, it is possible to accumulate and concentrate micro-objects with high efficiency while suppressing thermal damage that may be caused to the micro-objects and the concentration kit 11 (metal thin film 52, etc.). This effect is particularly important when the micro-objects are thermally sensitive, such as bacteria.

[0143] [Example 7] <Micro-objects capable of condensing light> We will explain the optical concentration results for various microscopic objects other than polystyrene particles.

[0144] ≪Bacteria≫ Figures 32 and 33 are chronologically arranged fluorescence observation images of bacterial concentration results. Figures 32 and 33 show bacterial concentration results when the bacterial concentrations are different. Figure 34 is a diagram for comparing fluorescence observation images of bacterial concentration results before and after laser light irradiation. Figure 35 is a diagram showing the results of observing the state of bacteria after laser light irradiation was stopped. Figure 35 shows the state of bacteria immediately after laser light irradiation was stopped and 5 seconds later.

[0145] Escherichia coli (or E. coli) was used as the bacteria. The bacterial concentration was 2.3 × 10 5 ,2.3×10 6 ,2.3×10 7 The concentration of cells was set to three different values ​​(cells / mL). SYTO9 (registered trademark) was used as the fluorescent dye. SYTO9 stains both live and dead bacteria. The driving current of the laser light source 40 was set to 700 mA (laser output 401 mW).

[0146] As shown in Figures 32 to 34, when the bacterial concentration was 2.3 × 10 6 or 2.3 x 10 7 It was confirmed that bacteria could be optically concentrated around the fiber end 501 (including the front of the fiber end 501) when the bacterial concentration was 2.3 × 107 35, when the laser light irradiation was stopped, the bacteria concentrated at the fiber end 501 were observed to diffuse into the sample.

[0147] Nanodiamonds Figure 36 shows a fluorescent image of the concentration results of nanodiamonds. Nanodiamonds undergo almost no discoloration and are a type of quantum sensor (quantum probe) that is important for cell imaging and evaluation of intracellular properties (temperature, pH, etc.). A quantum sensor is a sensor that uses the laws of quantum mechanics to measure minute physical quantities. Quantum sensors are expected to be a next-generation, ultra-sensitive sensing technology not only in life sciences but also in various fields such as IoT, the environment, and energy. For comparison, Figure 36 also shows the concentration results of polystyrene particles.

[0148] The concentration of nanodiamonds with a diameter of 100 nm is 5.43 × 10 10 The concentration of polystyrene particles with a diameter of 100 nm was also similar, at 4.55 × 10 10 The laser power was set to 320 mW in a non-contact configuration.

[0149] The concentration of nanodiamonds is (2.5±1.4)×10 7 [particles], where the concentration of polystyrene particles is (8.2±4.6) × 10 6 The enrichment efficiency of nanodiamonds was 2.3±1.3%, which was higher than that of polystyrene particles (0.89±0.5%).

[0150] In this way, it has been demonstrated that optical concentration of biological materials such as bacteria and cells is possible, as well as optical concentration of nanodiamonds, which are used in cell imaging, etc. In addition to nanodiamonds, quantum sensors can also include fluorescent molecules, quantum dots, metal nanoparticles, metal nanorods, etc. These quantum sensors (which may be of one type or multiple types) can also be optically concentrated, just like nanodiamonds.

[0151] [Example 8] <Long distance light concentration> A third embodiment of light concentration, which is different from the light concentration in the non-contact arrangement or contact arrangement described in the fifth embodiment, will be described.

[0152] Figure 37 is a diagram summarizing three modes of optical condensation. When an optical fiber having a tip (flat end face) that has undergone the characteristic change (stabilization of characteristics) described in Example 6 is placed in contact with the optical fiber, polystyrene particles are optically condensed over a long distance along the optical path of the laser light emitted from the tip of the optical fiber, as shown in the right diagram of Figure 37. This mode is called "long-distance optical condensation." In this example, the distance over which long-distance optical condensation occurs is longer than the vertical imaging range of 0.85 mm in the right diagram.

[0153] The optical concentration results for non-contact arrangement were 4.55 × 10 for polystyrene particles with a diameter of 1 μm. 7 The optical concentration in the contact configuration was performed by using 2 μm diameter polystyrene particles at a concentration of 5.68 × 10 6 The long-distance optical concentration was performed by using 2 μm diameter polystyrene particles at a concentration of 4.55 × 10 7 The solution was prepared at [particles / mL] and used.

[0154] Figure 38 is a diagram for explaining the mechanism of long-distance optical concentration. The left side shows side views in chronological order, and the right side shows top views in chronological order.

[0155] When laser light is irradiated, the vicinity of the fiber end 501 is locally heated due to the photothermal effect of the metal thin film 52 provided on the fiber end 501. This generates thermal convection. Additionally, the micro-objects are transported by the photo-induced force of the laser light transmitted through the metal thin film 52 acting on them. Furthermore, it is possible that evanescent waves are induced on the surface of the enrichment kit 11 (the surface of the cover glass constituting the enrichment kit 11), generating a photo-induced force. Thus, the transport of micro-objects by both thermal convection and photo-induced force may contribute to long-distance optical enrichment. The photo-induced force may be either the photo-induced force of the laser light transmitted through the metal thin film 52 or the photo-induced force of the evanescent waves induced on the surface of the enrichment kit 11, or both. It is also possible to transport micro-objects by only the photo-induced force of the laser light transmitted through the metal thin film 52 and / or the photo-induced force of the evanescent waves induced on the surface of the enrichment kit 11, without generating thermal convection.

[0156] Fig. 39 is a diagram showing a time series of fluorescent observation images of the optical condensation results in a comparative example, and Fig. 40 and Fig. 41 are diagrams showing a time series of fluorescent observation images of the optical condensation results in this example.

[0157] Figure 39 shows the results when no metal thin film 52 is provided. Figures 40 and 41 show the results when a metal thin film (10 nm thick) is provided at the tip of the optical fiber and the properties of the metal thin film are changed. In Figures 39 and 40, the size of the polystyrene particles (1 μm diameter) and the concentration (4.55 × 10 7 In Figure 41, the concentration of polystyrene particles (4.55 × 10 7 The concentration of the particles (particles / mL) was the same, but the size of the polystyrene particles (2 μm diameter) was different. In both cases, laser irradiation was performed in air at 540 mW for 1 minute, followed by laser irradiation in the sample at 485 mW for 5 minutes. The laser light was irradiated from the bottom to the top in the figure.

[0158] In Figure 39, which shows a comparative example, light condensation did not occur at the fiber end 501 (the lower part of each image), but occurred at a position away from the tip. In contrast, in Figure 40, which shows the present embodiment, light condensation was observed over a long distance and with high efficiency, starting from the fiber end 501. In Figure 41, where the diameter of the polystyrene particles was large, light condensation was observed over a long distance and with even higher efficiency than in Figure 40.

[0159] As described above, in the second embodiment, as in the first embodiment, minute objects are concentrated near the tip of the optical fiber 50 by utilizing the photothermal effect of the thin metal film 52 formed at the tip of the optical fiber 50. The tip of the optical fiber 50 can be adjusted to any position within the sample. Therefore, according to the second embodiment, minute objects can be concentrated at any location within the sample.

[0160] In the first and second embodiments, a configuration has been described in which the tip of the optical fiber 50 is disposed in the sample (including the gas-liquid interface). However, it is not essential that the tip of the optical fiber 50 be disposed in the sample in order to generate thermal convection; the tip of the optical fiber 50 may be disposed outside the sample. This is because even if the tip of the optical fiber 50 is disposed outside the sample, a temperature distribution can be generated in the sample by the photothermal effect as long as the distance between the optical fiber 50 and the sample is not excessively large. The tip of the optical fiber 50 is disposed at a position where the sample is heated and convection occurs in the sample when light with a wavelength included in the absorption wavelength range of the metal thin film 52 is introduced into the optical fiber 50.

[0161] In addition, Examples 1 to 4 were described in Embodiment 1, and Examples 5 to 8 were described in Embodiment 2. These Examples can be combined as appropriate. For example, contact arrangement / non-contact arrangement (Example 5) is naturally applicable to Examples 1 to 4 of Embodiment 1. The change in the properties of the metal thin film (Example 6) is applicable to Examples 1 to 4 of Embodiment 1, as well as to Examples 5 and 7 of Embodiment 2. The surfactant (Example 3) is also applicable to Examples 1, 2, and 4 of Embodiment 1 and Examples 5 to 8 of Embodiment 2.

[0162] [Aspect] It will be appreciated by those skilled in the art that the above exemplary embodiments are examples of the following aspects.

[0163] <Section 1> providing an optical fiber having a tip end provided with a photothermal conversion material; placing the tip in a liquid in which a plurality of microscopic objects are dispersed; A method for concentrating minute objects, comprising the step of introducing light of a wavelength included in the absorption wavelength range of the photothermal conversion material into the optical fiber, thereby heating the liquid around the tip and generating convection.

[0164] <Section 2> 2. The method for concentrating minute objects according to claim 1, wherein the step of placing includes a step of adjusting the position or height of the tip in the liquid.

[0165] <Section 3> A method for concentrating micro-objects described in paragraph 1 or 2, wherein the preparing step includes a step of pretreating the photothermal conversion material so that the transmittance or extinction rate of the photothermal conversion material is stabilized against changes in the output of light propagating within the optical fiber.

[0166] <Section 4> A method for concentrating minute objects according to any one of claims 1 to 3, wherein the step of generating convection includes the step of generating microbubbles at the tip and concentrating the plurality of minute objects in a region between the tip and the microbubbles.

[0167] <Section 5> the step of disposing includes a step of setting a position of the optical fiber with respect to a substrate holding the liquid to one of a non-contact position and a contact position; the non-contact arrangement is an arrangement in which the propagation path of the optical fiber does not contact the substrate, 4. The method for concentrating minute objects according to claim 3, wherein the contact arrangement is an arrangement in which the propagation path of the optical fiber is in contact with the substrate.

[0168] <Section 6> the step of placing the optical fiber is a step of placing the optical fiber in the non-contact position; 6. A method for concentrating micro-objects as described in claim 5, wherein the step of generating convection includes a step of concentrating the multiple micro-objects at the tip without generating microbubbles at the tip where the pretreatment has been performed.

[0169] <Section 7> the step of placing comprises placing the optical fiber in the contact configuration; 6. The method for concentrating minute objects described in item 5, wherein the step of generating convection includes a step of concentrating the plurality of minute objects along the optical path of light emitted from the tip.

[0170] <Section 8> 8. The method for concentrating minute objects according to any one of items 1 to 7, further comprising the step of introducing a surfactant into the liquid prior to the step of generating convection.

[0171] <Section 9> 9. The method for concentrating minute objects described in item 8, wherein the introducing step includes a step of adjusting the concentration of the surfactant in the liquid to a critical micelle concentration.

[0172] <Section 10> each of the plurality of microscopic objects is a quantum sensor; 10. The method for concentrating minute objects according to any one of claims 1 to 9, wherein the quantum sensor includes at least one of nanodiamonds, fluorescent molecules, quantum dots, metal nanoparticles, and metal nanorods.

[0173] <Section 11> A method for concentrating a plurality of minute objects dispersed in a liquid, comprising: providing an optical fiber having a tip end provided with a photothermal conversion material; A method for concentrating micro-objects, comprising the step of positioning the tip at a position where the liquid is heated and convection occurs in the liquid when light of a wavelength included in the absorption wavelength range of the photothermal conversion material is introduced into the optical fiber.

[0174] <Section 12> the step of placing includes a step of placing the tip at a position where a light-induced force is generated in the liquid in addition to the convection; the photoinduced force includes at least one of a photoinduced force caused by light transmitted through the photothermal conversion material and a photoinduced force caused by an evanescent wave induced on the surface of the substrate holding the liquid by light propagating through the optical fiber. No. 11 term A method for concentrating minute objects according to claim 1.

[0175] <Section 13> A method for concentrating a plurality of minute objects dispersed in a liquid, comprising: providing an optical fiber having a tip; and positioning the tip at a position where a light-induced force is generated in the liquid when light is introduced into the optical fiber; A method for concentrating micro-objects, wherein the optically induced force includes at least one of an optically induced force caused by light emitted from the tip and an optically induced force caused by an evanescent wave induced by light propagating through the optical fiber to the surface of a substrate holding the liquid.

[0176] <Section 14> a substrate configured to hold, on a main surface thereof, a liquid in which a plurality of microscopic objects are dispersed; an optical fiber having a tip provided with a photothermal conversion material; The optical fiber is configured so that the tip is positioned in the liquid when the liquid is held on the main surface.

[0177] <Section 15> 15. The kit for concentrating minute objects according to claim 14, wherein the color of the photothermal conversion material is a color that changes with a change in the output of light propagating through the optical fiber.

[0178] <Section 16> 16. The kit for concentrating minute objects according to claim 14 or 15, wherein the tip has a perfect circular shape.

[0179] <Section 17> 17. The kit for concentrating minute objects according to any one of items 14 to 16, wherein the optical fiber is a multimode fiber.

[0180] <Section 18> an optical fiber having a first end provided with a photothermal conversion material and a second end; an adjustment mechanism that adjusts the position or height of the first end in a liquid in which a plurality of micro objects are dispersed while the liquid is held in a concentration kit; a light source optically coupled to the second end and emitting light of a wavelength included in the absorption wavelength range of the photothermal conversion material;

[0181] <Section 19> the light source generates microbubbles at the first end by heating the liquid around the first end with the light; The micro-object concentration system comprises: an imaging device that captures an image of the region between the first end and the microbubble; and a processor for calculating a concentration number of the plurality of minute objects in the region according to the following formula (1) obtained from the image,

[0182]

number

[0183] In the formula (1), N represents the concentration number of the plurality of minute objects; h represents the height of the concentrated region of the plurality of micro objects; r1 represents the distance between an imaginary central axis of the microbubble extending perpendicular to the end face of the first end and the outer periphery of the enrichment region; r3 represents the distance between the central axis and the inner periphery of the enrichment region; r2 represents the distance between the central axis and a portion of the enrichment region corresponding to the height, V represents the volume of each of the plurality of minute objects; 19. A system for concentrating minute objects as described in paragraph 18, wherein F represents the packing fraction of a hexagonal close-packed structure.

[0184] <Section 20> the light source generates microbubbles at the first end by heating the liquid around the first end with the light; The micro-object concentration system comprises: an imaging device that captures an image of the region between the first end and the microbubble; and a processor for calculating the concentration number of the plurality of minute objects in the region according to the following formula (2) obtained from the image,

[0185]

number

[0186] In the formula (2), N represents the concentration number of the plurality of minute objects; h represents the height of the concentrated region of the plurality of micro objects; r1 represents the distance between an imaginary central axis of the microbubble extending perpendicular to the end face of the first end and the outer periphery of the enrichment region; r3 represents the distance between the central axis and the inner periphery of the enrichment region; r2 represents the distance between the central axis and a portion of the enrichment region corresponding to the height, V represents the volume of each of the plurality of minute objects; 19. A system for concentrating minute objects as described in paragraph 18, wherein F represents the packing fraction of a hexagonal close-packed structure.

[0187] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0188] 1 Concentration system, 11,12 Concentration kit, 111 top surface, 121 substrate, 122 cover, 123 spacer, 20 sample stage, 30 sample adjustment mechanism, 40 laser light source, 50 optical fiber, 51 propagation path, 52 metal thin film, 501 fiber end, 502 fiber side, 60 fiber stage, 70 fiber adjustment mechanism, 81 illumination light source, 82 objective lens, 83 lens, 84 camera, 91 slide glass, 100 controller, 101 processor, 102 memory, 103 input / output port.

Claims

1. providing an optical fiber having a tip end provided with a photothermal conversion material; placing the tip in a liquid in which a plurality of microscopic objects are dispersed; A method for concentrating micro-objects, comprising the step of introducing light of a wavelength included in the absorption wavelength range of the photothermal conversion material into the optical fiber, thereby heating the liquid around the tip and generating convection, thereby concentrating the multiple micro-objects at the tip.

2. The method for concentrating minute objects according to claim 1 , wherein the step of placing includes a step of adjusting the position or height of the tip in the liquid.

3. The method for concentrating micro-objects described in claim 1, wherein the preparing step includes a step of pretreating the photothermal conversion material so that the transmittance or extinction rate of the photothermal conversion material is stabilized against changes in the power of light propagating within the optical fiber.

4. The method for concentrating minute objects according to any one of claims 1 to 3, wherein the step of generating convection includes the step of generating microbubbles at the tip and concentrating the plurality of minute objects in a region between the tip and the microbubbles.

5. the step of disposing includes a step of setting a position of the optical fiber with respect to a substrate holding the liquid to one of a non-contact position and a contact position; the non-contact arrangement is an arrangement in which the propagation path of the optical fiber does not contact the substrate, The method for concentrating minute objects according to claim 3 , wherein the contact arrangement is an arrangement in which the propagation path of the optical fiber is in contact with the substrate.

6. the step of placing the optical fiber is a step of placing the optical fiber in the non-contact position; The method for concentrating micro-objects according to claim 5, wherein the step of generating convection includes a step of concentrating the plurality of micro-objects at the tip without generating microbubbles at the tip where the pretreatment has been performed.

7. the step of placing comprises placing the optical fiber in the contact configuration; The method for concentrating minute objects according to claim 5 , wherein the step of generating convection includes a step of concentrating the plurality of minute objects along an optical path of light emitted from the tip.

8. 4. The method for concentrating minute objects according to claim 1, further comprising the step of introducing a surfactant into the liquid prior to the step of generating convection.

9. The method for concentrating minute objects according to claim 8 , wherein the step of introducing includes a step of adjusting the concentration of the surfactant in the liquid to a critical micelle concentration.

10. each of the plurality of microscopic objects is a quantum sensor; The method for concentrating minute objects according to any one of claims 1 to 3, wherein the quantum sensor includes at least one of nanodiamonds, fluorescent molecules, quantum dots, metal nanoparticles, and metal nanorods.

11. A method for concentrating a plurality of minute objects dispersed in a liquid, comprising: providing an optical fiber having a tip end provided with a photothermal conversion material; A method for concentrating micro-objects, comprising the steps of: positioning the tip at a position where, when light of a wavelength included in the absorption wavelength range of the photothermal conversion material is introduced into the optical fiber, the liquid is heated and convection occurs in the liquid, thereby concentrating the multiple micro-objects at the tip.

12. the step of placing includes a step of placing the tip at a position where a light-induced force is generated in the liquid in addition to the convection; The method for concentrating micro-objects described in claim 11, wherein the photo-induced force includes at least one of a photo-induced force caused by light passing through the photothermal conversion material and a photo-induced force caused by an evanescent wave induced by light propagating through the optical fiber to the surface of a substrate holding the liquid.

13. A method for concentrating a plurality of minute objects dispersed in a liquid, comprising: providing an optical fiber having a tip; and positioning the tip at a position where a light-induced force is generated in the liquid when light is introduced into the optical fiber; A method for concentrating micro-objects, wherein the optically induced force includes at least one of an optically induced force caused by light emitted from the tip and an optically induced force caused by an evanescent wave induced by light propagating through the optical fiber to the surface of a substrate holding the liquid.

14. a substrate configured to hold, on a main surface thereof, a liquid in which a plurality of microscopic objects are dispersed; an optical fiber having a tip provided with a photothermal conversion material; A micro-object concentration kit, wherein the optical fiber is configured so that the tip is placed in the liquid when the liquid is held on the main surface, and so that the multiple micro-objects are concentrated at the tip when light of a wavelength included in the absorption wavelength range of the photothermal conversion material is introduced.

15. The kit for concentrating minute objects according to claim 14 , wherein the color of the photothermal conversion material is a color that changes with a change in the power of the light propagating through the optical fiber.

16. The kit for concentrating minute objects according to claim 14 or 15, wherein the tip has a perfect circular shape.

17. The kit for concentrating minute objects according to claim 14 or 15, wherein the optical fiber is a multimode fiber.

18. an optical fiber having a first end provided with a photothermal conversion material and a second end; an adjustment mechanism that adjusts the position or height of the first end in a liquid in which a plurality of micro objects are dispersed while the liquid is held in a concentration kit; a light source optically coupled to the second end and emitting light of a wavelength included in the absorption wavelength range of the photothermal conversion material.

19. the light source generates microbubbles at the first end by heating the liquid around the first end with the light; The micro-object concentration system comprises: an imaging device for capturing an image of a region between the first end and the microbubble; and a processor for calculating a concentration number of the plurality of minute objects in the region according to the following formula (1) obtained from the image, [Equation 1] In the formula (1), N represents the concentration number of the plurality of minute objects; h represents the height of the concentrated region of the plurality of micro-objects; r １ represents the distance between an imaginary central axis of the microbubble extending perpendicular to the end face of the first end and the outer periphery of the enrichment region, r3 represents the distance between the central axis and the inner periphery of the enrichment region; r2 represents the distance between the central axis and a portion of the enrichment region corresponding to the height, V represents the volume of each of the plurality of minute objects; The system for concentrating minute objects according to claim 18, wherein F represents the packing fraction of a hexagonal close-packed structure.

20. the light source generates microbubbles at the first end by heating the liquid around the first end with the light; The micro-object concentration system comprises: an imaging device for capturing an image of a region between the first end and the microbubble; and a processor for calculating a concentration number of the plurality of minute objects in the region according to the following formula (2) obtained from the image, [Equation 2] In the formula (2), N represents the concentration number of the plurality of minute objects; h represents the height of the concentrated region of the plurality of micro-objects; r １ represents the distance between an imaginary central axis of the microbubble extending perpendicular to the end face of the first end and the outer periphery of the enrichment region, r3 represents the distance between the central axis and the inner periphery of the enrichment region; r2 represents the distance between the central axis and a portion of the enrichment region corresponding to the height, V represents the volume of each of the plurality of minute objects; The system for concentrating minute objects according to claim 18, wherein F represents the packing fraction of a hexagonal close-packed structure.

Images