Photo-thermal conversion element, method for manufacturing the same, photo-thermal power generation device, and micro-object gathering system

Abstract

A method of manufacturing a light-heat conversion element (1, 2) includes a step of preparing a solid material, and a step of forming a machined machining region by irradiating laser light to the solid material. The forming step includes a step of particlizing the solid material to blacken the machining region (LP).

Description

Technical Field

[0001] This disclosure relates to photothermal conversion elements, methods for manufacturing photothermal conversion elements, photothermal power generation devices using photothermal conversion elements, and a system for aggregating micro-objects using photothermal conversion elements. Background Technology

[0002] In recent years, photothermal conversion elements, which convert white light such as sunlight into heat and utilize that heat, have attracted attention. The manufacture of these elements often involves complex methods, including chemical processing. Therefore, techniques for manufacturing photothermal conversion elements using simpler methods have been proposed.

[0003] For example, the photothermal conversion element disclosed in Japanese Patent Application Publication No. 2013-254940 (Patent Document 1) comprises a plurality of metal nanoparticle aggregate structures and a substrate. Each of the plurality of metal nanoparticle aggregate structures is formed by aggregating a plurality of metal nanoparticles. The substrate has a fixing surface on which the plurality of metal nanoparticle aggregate structures are fixed. A region in which the plurality of metal nanoparticle aggregate structures are densely packed is formed on this fixing surface.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2013-254940

[0007] Patent Document 2: International Publication No. 2017 / 195872

[0008] Patent Document 3: Japanese Patent Application Publication No. 2017-202446

[0009] Non-patent literature

[0010] Non-patent document 1: Atsuko Kosuga, Yasuyuki Yamamoto, Moe Miyai, Mie Matsuzawa, Yushi Nishimura, Shimpei Hidaka, Kohei Yamamoto, Shin Tanaka, Yojiro Yamamoto, Shiho Tokonami and Takuya Iida, "A high performance photothermal film with spherical shell-type metallic nanocomposites for solar thermoelectricconversion”,Nanoscale,2015,7,7580-7584 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] In photothermal conversion elements that convert light into heat, it is required to convert light into heat with the highest possible efficiency. Therefore, it is desirable to be able to manufacture such photothermal conversion elements using simple manufacturing methods.

[0013] This disclosure was made to solve the above-mentioned problems, and the purpose of this disclosure is to provide a photothermal conversion element capable of efficiently converting light into heat. Another purpose of this disclosure is to provide a simple method for manufacturing the photothermal conversion element.

[0014] Methods for solving problems

[0015] (1) A method for manufacturing a photothermal conversion element according to one aspect of the present disclosure includes a step of preparing a solid material and a step of forming a processing area by irradiating the solid material with a laser. The forming step includes a step of micronizing the solid material to blacken the processing area.

[0016] (2) The forming steps include scanning with a laser to cut microgrooves in the processing area.

[0017] (3) Solid materials include at least one of thermoelectric materials exhibiting thermoelectric effects and metal thin films.

[0018] (4) The photothermal conversion element according to other aspects of this disclosure comprises a solid material. The solid material includes regions where the solid material is blackened by the dispersion of a plurality of microparticles composed of the solid material. The plurality of microparticles generate local surface plasmon resonances on their respective surfaces when irradiated with light.

[0019] (5) Solid materials include at least one of thermoelectric materials exhibiting thermoelectric effects and metal thin films.

[0020] (6) According to another aspect of this disclosure, a solar thermal power generation device is capable of supplying the generated electricity to a load. The photoelectric heating device includes: a photothermal conversion element; and a thermoelectric conversion unit thermally connected to the photothermal conversion element and converting heat into electricity. The thermoelectric conversion unit includes: a P-type thermoelectric element; a first electrode electrically connected to the low-temperature side of the P-type thermoelectric element; an N-type thermoelectric element; and a second electrode electrically connected to the low-temperature side of the N-type thermoelectric element. The first electrode, the second electrode, and the load are connected.

[0021] (7) One of the P-type thermoelectric element and the N-type thermoelectric element, along with the photothermal conversion element, together constitute a photothermal conversion thermoelectric element.

[0022] (8) A photothermal conversion element according to another aspect of the present disclosure comprises: a substrate; and a metal thin film disposed on the substrate. The metal thin film includes regions where a plurality of particles made of the same material as the metal thin film are aggregated, causing the metal thin film to blacken. The plurality of particles generate local surface plasmon resonances on their respective surfaces when irradiated with light.

[0023] (9) A micro-object agglomeration system according to another aspect of the present disclosure, which agglomerates multiple micro-objects contained in a liquid. The micro-object agglomeration system includes: a holding member for holding a photothermal conversion element; and a light source that emits light that causes local surface plasmon resonances on the respective surfaces of the multiple particles. The light source agglomerates the multiple micro-objects by irradiating the region of the liquid held in the region with light, thereby generating convection in the liquid.

[0024] (10) The liquid is held on the upper surface of the aforementioned region. Light from the light source shines upwards from below the region. The thickness of the metal film is specified to make the region translucent relative to the light source.

[0025] Invention Effects

[0026] According to this disclosure, a photothermal conversion element capable of efficiently converting light into heat can be provided. Furthermore, according to this disclosure, such a photothermal conversion element can be easily manufactured. Attached Figure Description

[0027] Figure 1 This is a diagram schematically showing the overall structure of the laser processing system in Embodiment 1.

[0028] Figure 2 This is a diagram showing the structure of the photothermal conversion element in Embodiment 1.

[0029] Figure 3 This is a photograph of the manufactured photothermal conversion element.

[0030] Figure 4 This is a diagram showing the structure of other photothermal conversion elements in Embodiment 1.

[0031] Figure 5 This is a photograph of the manufactured photothermal conversion element.

[0032] Figure 6 This is Figure 1, which illustrates the laser processing conditions for photothermal conversion elements.

[0033] Figure 7 This is Figure 2, which illustrates the laser processing conditions for photothermal conversion elements.

[0034] Figure 8 This is a flowchart illustrating the manufacturing method of the photothermal conversion element in Embodiment 1.

[0035] Figure 9 This is a diagram showing the laser processing conditions of the photothermal conversion element in the embodiment of implementation 1.

[0036] Figure 10 This is a diagram showing the observation results of the photothermal conversion element in the embodiment of implementation 1.

[0037] Figure 11 This is a graph showing the measurement results of the absorption spectrum of the photothermal conversion element manufactured according to condition 1A.

[0038] Figure 12 This is a graph showing the measurement results of the absorption spectrum of the photothermal conversion element manufactured according to condition 1B.

[0039] Figure 13 This is a graph showing the measurement results of the absorption spectrum of the photothermal conversion element manufactured according to condition 1C.

[0040] Figure 14 This is a graph showing the measurement results of the absorption spectrum of a photothermal conversion element manufactured according to Condition 1D.

[0041] Figure 15 This is a diagram showing the laser processing conditions of another photothermal conversion element in the embodiment of implementation 1.

[0042] Figure 16 This is a diagram showing the observation results of the photothermal conversion element in the embodiment of implementation 1.

[0043] Figure 17 This is a graph showing the measurement results of the reflectance spectrum of the photothermal conversion element manufactured according to conditions 2A to 2E.

[0044] Figure 18 This is a diagram showing the overall structure of the solar thermal power generation device in Embodiment 2.

[0045] Figure 19 This is a diagram showing an example of a more detailed structure of a concentrated solar power (CSP) device.

[0046] Figure 20 This is another example of a more detailed structure of a concentrated solar power (CSP) device.

[0047] Figure 21 This is a diagram illustrating the simulation conditions for the temperature rise caused by the photothermal effect of the photothermal conversion element 2.

[0048] Figure 22 This is a graph showing the simulation results of the temperature rise of the photothermal conversion element caused by the photothermal effect.

[0049] Figure 23This is a diagram illustrating the simulation conditions for the photothermal conversion and thermoelectric conversion of a solar thermal power generation device.

[0050] Figure 24 This is a graph showing the simulation results of the power generation of a concentrated solar power (CSP) device.

[0051] Figure 25 This is a diagram showing the overall structure of the micro-object aggregation system of Embodiment 3.

[0052] Figure 26 This is an enlarged view of the photothermal conversion element held on the XYZ axis platform.

[0053] Figure 27 These are photographs taken of the sample under laser irradiation.

[0054] Figure 28 This is a conceptual diagram used to illustrate the aggregation mechanism of microbeads. Detailed Implementation

[0055] The present embodiment will now be described in detail with reference to the accompanying drawings. Furthermore, identical or equivalent parts in the drawings are given the same reference numerals and will not be described again.

[0056] <Terminology Explanation>

[0057] In this disclosure and its embodiments, "thermoelectric material" refers to a material exhibiting the thermoelectric effect (Seebeck effect), and more specifically, to a material having an absolute value of 50 [μV / K] or more of thermoelectric potential at room temperature (20°C) and a resistivity (specific resistance) of 100 [mΩ·cm] or less at room temperature. Although materials with an absolute value of 50 [μV / K] or more of thermoelectric potential may include insulators, insulators are excluded from thermoelectric materials based on the condition that the resistivity is 100 [mΩ·cm] or less. Examples of thermoelectric materials include: alloys (specifically constantan, Hessler alloys, semi-Hessler alloys, etc.), silicides (iron silicides, etc.), metals, semiconductors, ceramics, etc.

[0058] In addition, the absolute value of constantan's thermoelectric potential is approximately 75 [μV / K], and its resistivity is approximately 4.8 × 10⁻⁶. -2 [mΩ·cm]. For comparison, the absolute value of the thermoelectric potential of gold is approximately 1.94 [μV / K], and the resistivity of gold is approximately 2.4 × 10⁻⁶. -3 [mΩ·cm].

[0059] In this disclosure and its embodiments, "microparticle" refers to a particle having a size ranging from nanometer to micrometer. The shape of the microparticle is not limited to a sphere, but may also be an ellipsoid or rod-shaped particle, etc. Examples of microparticles include: metal nanoparticles, metal microparticles, semiconductor nanoparticles, semiconductor microparticles, aggregates of metal nanoparticles, aggregates of metal nanoparticles and metal microparticles, aggregates of semiconductor nanoparticles and semiconductor microparticles, etc.

[0060] In this disclosure and its embodiments, "micro-object" refers to a substance having a size ranging from nanometer to micrometer. The shape of a micro-object is not limited to a sphere, but may also be an ellipsoid, rod, or the like. When a micro-object is an ellipsoid, it is acceptable as long as at least one of its length along its major axis and its length along its minor axis is within the range of nanometer to micrometer. When a micro-object is rod-shaped, it is acceptable as long as at least one of its width and length is within the range of nanometer to micrometer. Examples of micro-objects include: metal nanoparticles, metal nanoparticle aggregates, metal nanoparticle clusters, semiconductor nanoparticles, organic nanoparticles, resin beads, and particulate matter (PM).

[0061] "Metal nanoparticles" refer to metal particles with nanometer-scale dimensions. "Metal micron particles" refer to metal particles with micron-scale dimensions. "Metal nanoparticle aggregates" refer to aggregates formed by the aggregation of multiple metal nanoparticles. "Metal nanoparticle aggregate structures" refer to structures, for example, multiple metal nanoparticles fixed to the surface of beads via interaction sites, with gaps between them, arranged at intervals less than the diameter of the metal nanoparticles. "Semiconductor nanoparticles" refer to semiconductor particles with nanometer-scale dimensions. "Semiconductor micron particles" refer to semiconductor particles with micron-scale dimensions. "Organic nanoparticles" refer to particles composed of organic compounds with nanometer-scale dimensions. "Resin beads" refer to particles composed of resin with nanometer to micron-scale dimensions. "PM" refers to particulate matter with micron-scale dimensions.

[0062] Tiny objects can be substances originating from living organisms (living matter). More specifically, tiny objects can include cells, microorganisms (bacteria, fungi, etc.), living macromolecules (proteins, nucleic acids, lipids, polysaccharides, etc.), antigens (allergens, etc.), and viruses.

[0063] In this disclosure and its embodiments, a "microgroove" refers to a groove with a width on the order of micrometers. When multiple microgrooves are cut, preferably, the spacing between a particular groove and its adjacent grooves is also on the order of micrometers. The shape of the microgroove is not limited to a straight line; it can also be curved. Furthermore, a microgroove can include a portion where a single groove branches into multiple grooves, or a portion where multiple grooves merge into a single groove. A microgroove can also be dashed.

[0064] In this disclosure and its embodiments, "nanoscale" includes the range from 1 nm to 1000 nm (= 1 μm). "Micrometer scale" includes the range from 1 μm to 1000 μm (= 1 mm). Therefore, "nanoscale to micrometer scale" includes the range from 1 nm to 1000 μm. The term "nanoscale to micrometer scale" generally refers to the range of several nm to several hundred μm, preferably the range of 100 nm to 100 μm, and more preferably the range of 1 μm to tens of μm.

[0065] In this disclosure and its embodiments, "white light" refers to light having a wavelength range (e.g., a wavelength range of 200 nm to 1100 nm) in the ultraviolet to near-infrared region. White light can be either continuous light or pulsed light.

[0066] In this disclosure and its embodiments, "transmittance" refers to the property that the intensity of light passing through a material is greater than zero. When light passes through a material, the remaining energy of the light can be absorbed, scattered, or reflected by the material. Furthermore, the wavelength region of this light can be any region among the ultraviolet, visible, and near-infrared regions, a region spanning two of these three regions, or a region spanning all three regions. Transmittance can be defined, for example, by the range of transmittance. In this case, the lower limit of the transmittance range is only required to be greater than 0, and there is no particular limitation.

[0067] In this disclosure and its embodiments, "microbubble" refers to bubbles at the micrometer scale.

[0068] [Implementation Method 1]

[0069] In Embodiment 1, two photothermal conversion elements 1 and 2 and their manufacturing methods are described. The photothermal conversion elements 1 and 2 in Embodiment 1 are manufactured using a laser processing system. Hereinafter, the x and y directions represent the horizontal direction. The x and y directions are orthogonal to each other. The z direction represents the vertical direction. The direction of gravity is below the z direction.

[0070] <Structure of a Laser Processing System>

[0071] Figure 1 This is a schematic diagram illustrating the overall structure of the laser processing system in Embodiment 1. (Refer to...) Figure 1The laser processing system 100 includes an XYZ axis platform 110, a laser oscillator 120, a laser driver 130, an objective lens 140, a scanning mechanism 150, and a control device 160.

[0072] The XYZ axis platform 110 holds photothermal conversion element 1 (or photothermal conversion element 2). Regarding the structure of photothermal conversion elements 1 and 2, in... Figures 2-5 The explanation is provided below.

[0073] The laser oscillator 120 emits pulsed laser light L. For example, a femtosecond laser that emits ultrashort pulses can be used as the laser oscillator 120. As a specific example of such a laser oscillator 120, a Ti:sapphire laser can be cited. Ti:sapphire lasers emit light with wavelengths contained in the near-infrared region (wavelengths in the range of 650 nm to 1100 nm, for example, a center wavelength of 1040 nm).

[0074] The laser driver 130 provides drive current to the laser oscillator 120 and controls the characteristics of the pulsed laser L emitted from the laser oscillator 120 (specifically, laser output, pulse width, and repetition frequency, etc.) according to the instructions of the control device 160.

[0075] Objective lens 140 converges the pulsed laser L from laser oscillator 120. The light converged by objective lens 140 illuminates photothermal conversion element 1, which is held on XYZ axis platform 110 before or during processing.

[0076] The scanning mechanism 150 can be configured to adjust the positions of the XYZ axis platform 110 in the x, y, and z directions according to the instructions of the control device 160. In this embodiment, the scanning mechanism 150 first sets the distance (the spot height H of the pulsed laser L described later) between the photothermal conversion element 1 and the objective lens 140 on the XYZ axis platform 110. Then, the scanning mechanism 150 scans the photothermal conversion element 1 with the pulsed laser L by adjusting the positions of the XYZ axis platform 110 in the x and y directions while keeping the spot height H constant.

[0077] In addition, Figure 1 In the example shown, the photothermal conversion element 1 is scanned by the pulsed laser L by moving the photothermal conversion element 1 based on the fixed irradiation position of the pulsed laser L. However, conversely, the irradiation position of the pulsed laser L can also be moved relative to the fixed photothermal conversion element 1.

[0078] Although not shown in the figures, the control device 160 is a microcomputer including a processor such as a CPU (Central Processing Unit), memory such as ROM (Read Only Memory) and RAM (Random Access Memory), and input / output ports. The control device 160 controls the various devices within the laser processing system 100 (laser driver 130 and scanning mechanism 150). Specifically, the control device 160 sets the irradiation conditions (laser processing conditions) of the pulsed laser L and outputs instructions for performing processing according to these laser processing conditions to the laser driver 130. Furthermore, the control device 160 outputs instructions for scanning with the pulsed laser L to the scanning mechanism 150.

[0079] Figure 2 This is a diagram showing the structure of the photothermal conversion element 1 in Embodiment 1. (Refer to...) Figure 2 The photothermal conversion element 1 includes a substrate 11 and a metal thin film 12 disposed on the substrate 11.

[0080] The substrate 11 is formed of a material that does not affect photothermal conversion and thermoelectric conversion (described later) and is transparent to the pulsed laser L (near-infrared light in this example) of the laser oscillator 120. Examples of such materials include quartz, silicon, and resin films. In this embodiment, a glass substrate (glass cover) is used as the substrate 11.

[0081] The material of the metal thin film 12 is preferably a material with high photothermal conversion efficiency in the wavelength region of the light irradiated onto the metal thin film 12 (white light WL in the example described later). Figure 2 In the example shown, the metal thin film 12 is a gold thin film with a thickness on the nanometer scale. The gold thin film can be formed on the glass substrate using known methods such as sputtering or electroless plating.

[0082] Furthermore, the metal thin film 12 may not be formed on the entire surface of the substrate 11, but only on at least a portion of the substrate 11. Moreover, the material of the metal thin film 12 is not limited to gold; it can be any material capable of photothermal conversion, such as silver or an alloy of constantan. The metal thin film 12 is an example of the "solid material" disclosed herein.

[0083] The metal thin film 12 includes a processed region LP formed by irradiating the metal thin film 12 with a pulsed laser L. Details are described later. The processed region LP contains metal nanoparticles formed by micronizing the metal thin film 12 through irradiation with the pulsed laser L; it is a blackened region (see reference). Figure 10 ).

[0084] Figure 3This is a photograph of the manufactured photothermal conversion element 1. Figure 3 In the example shown, the photothermal conversion element 1 includes two processing regions LP (processing regions LP1 and LP2). Thus, the number of processing regions LP is not limited to one, and can be any number of two or more. Furthermore, the processing regions LP can be formed only on a portion of the metal thin film 12, or the entire surface of the metal thin film 12 can be laser-processed to form the processing regions LP across the entire surface. Additionally, in Figure 3 In the middle, adhesive tape for fixing the photothermal conversion element 1 is pasted on the top, bottom, left and right sides of the photothermal conversion element 1.

[0085] Figure 4 This is a diagram showing the structure of another photothermal conversion element 2 in Embodiment 1. Figure 5 This is a photograph of the manufactured photothermal conversion element 2. (See reference) Figure 4 and Figure 5 The photothermal conversion element 2 can also be a metal plate. That is, the substrate 11, which serves as the base for forming the metal thin film 12, is not necessary. In this example, the material of the photothermal conversion element 2 is a copper-nickel alloy. In particular, a copper alloy with a nickel content of about 40% to 50%, namely constantan, can be used. The metal plate made of constantan or the like is another example of the "solid material" disclosed herein. However, the "solid material" can also be other thermoelectric materials that exhibit thermoelectric effects.

[0086] Similar to the metal thin film 12, the photothermal conversion element 2 includes a processing region LP formed by irradiating a metal material with a pulsed laser L. Figure 5 In the photograph shown, two blackened processing areas LP3 and LP4 are provided on the photothermal conversion element 2.

[0087] <Laser Processing Conditions>

[0088] Next, the irradiation conditions (laser processing conditions) of the pulsed laser L used to form the appropriate processing area LP will be explained. The laser processing conditions are defined by three parameters. Since the method of setting each parameter is common in either photothermal conversion element 1 or 2, the laser processing conditions of photothermal conversion element 1 will be explained representatively below.

[0089] Figure 6 Figure 1 illustrates the laser processing conditions for photothermal conversion element 1. (Refer to...) Figure 6 The first parameter specifying the laser processing conditions is the spot height H [μm]. The spot size (radius of the pulsed laser L) is smallest at the beam waist. The spot height H refers to the distance between the beam waist and the upper surface of the photothermal conversion element 1, with the beam waist position as the reference (H=0). Figure 6 The distance on the optical axis between the surfaces of the metal thin film 12 shown in the example is the distance between them.

[0090] Figure 7 This is Figure 2, used to illustrate the laser processing conditions of the photothermal conversion element 1. The second parameter defining the laser processing conditions is the scanning interval D [μm] of the pulsed laser L. In this embodiment, the pulsed laser L is scanned in the form of multiple parallel straight lines arranged at regular intervals. The scanning interval D refers to the distance between a certain straight line and other straight lines adjacent to it. Furthermore, the processing area LP for laser processing based on the pulsed laser L is a square of several millimeters (6mm × 6mm in the example described later).

[0091] The third parameter specifying the laser processing conditions is the laser output P. out [mW]. Laser output P out It is the output of the pulsed laser L after passing through the objective lens 140 (i.e., the position of the photothermal conversion element 1).

[0092] By appropriately combining the spot height H, scanning interval D, and laser output P out These three parameters can adjust the characteristics (optical properties and photothermal conversion properties) exhibited by the processing area LP. The measurement results of the characteristics of the processing area LP will be explained in detail later.

[0093] <Manufacturing process of photothermal conversion element>

[0094] Figure 8 This is a flowchart illustrating a method for manufacturing the photothermal conversion element 1 according to Embodiment 1. This flowchart is executed when predetermined conditions are met (e.g., when a user operates a start button not shown). The steps included in this flowchart are generally implemented through software processing of the control device 160, but may also be implemented, in part or in whole, through hardware (circuit) fabricated within the control device 160. Hereinafter, each step will be abbreviated as "ST".

[0095] Reference Figure 8 In ST1, the control device 160 sets the above three parameters (spot height H, scanning interval D, and laser output P). out The combination of these three parameters serves as the laser processing conditions. More specifically, by conducting prior experiments, an appropriate combination of these three parameters can be determined based on the type of photothermal conversion element 1 (the material and thickness of the metal thin film 12) and its intended use. Therefore, the control device 160 can select an appropriate combination from a plurality of pre-prepared combinations based on the type and intended use of the photothermal conversion element 1. Alternatively, the control device 160 can also accept user input specifying the combination of the aforementioned three parameters via an input device (such as a mouse or keyboard) not shown in the figure.

[0096] In ST2, the control device 160 sets the photothermal conversion element 1, before processing, on the XYZ axis platform 110. This process can be achieved, for example, by the feed mechanism (not shown) of the photothermal conversion element 1. Furthermore, the process of ST2 is equivalent to the "preparation step" of this disclosure.

[0097] In ST3, the control device 160 outputs a command to the scanning mechanism 150 and controls the height (position in the z-direction) of the XYZ axis platform 110. As a result, the control device 160 adjusts the spot height H to the value set in ST1.

[0098] In ST4, the control device 160 controls the laser driver 130 to start (or continue) the irradiation of the pulsed laser L according to the laser processing conditions set in ST1. Furthermore, the control device 160 controls the scanning mechanism 150 to scan with the pulsed laser L according to a pre-set scanning pattern. The processing in ST4 corresponds to the "manufacturing steps" of this disclosure.

[0099] In ST5, the control device 160 determines whether the predetermined end condition for laser processing is met. The control device 160 determines that the end condition for laser processing is met when the scanning pattern is completed. If the end condition is not met (not in ST4), the control device 160 returns the process to ST4. Thus, the irradiation of the pulsed laser L continues. When the end condition is met (yes in ST5), the control device 160 causes the process to proceed to ST6.

[0100] In ST6, the control device 160 controls the laser driver 130 to stop the irradiation of the pulsed laser L. Then, the control device 160 controls the feed mechanism of the photothermal conversion element 1 to remove the processed photothermal conversion element 1 from the XYZ axis platform 110 (ST7). Thus, the series of processes ends.

[0101] [Example of Implementation Method 1]

[0102] Next, the observation results and spectral measurement results of photothermal conversion elements 1 and 2 fabricated using the laser processing system 100 will be explained. First, the photothermal conversion element 1 (refer to...) after laser processing of the gold thin film formed on the glass substrate... Figure 2 and Figure 3 The evaluation results will be explained. In this example, the thickness of the gold film is 100 μm.

[0103] Figure 9 This is a diagram illustrating the laser processing conditions of the photothermal conversion element 1 in Embodiment 1. (Refer to...) Figure 9 ,according to Figure 9 The photothermal conversion element 1 is laser-processed under four conditions 1A to 1D shown. Under conditions 1A to 1D, the laser output P...out The common parameters are 800mW and scanning interval D = 50μm. However, the spot height H varies between conditions 1A and 1D. Furthermore, the pulse width of the pulsed laser L is set to 400fs, and the repetition frequency of the pulsed laser L is set to 100kHz.

[0104] Figure 10 This is a diagram showing the observation results of the photothermal conversion element 1 in the embodiment of implementation 1. Figure 10 The text shows the data based on... Figure 9 SEM (Scanning Electron Microscope) images of the photothermal conversion element 1 manufactured under conditions 1A to 1D as described in the text. (Refer to...) Figure 10 In the 350x magnification image, the lighter-colored areas (the areas between the two black lines) are those irradiated by pulsed laser L. In the 2000x or 5000x magnification images, under any of conditions 1A–1D, microparticle-sized gold was confirmed in the microgrooves formed by irradiation with pulsed laser L. Although most gold particles (diameter) ranged from tens to hundreds of nanometers, some exhibited micrometer-scale dimensions.

[0105] When gold nanoparticles (or gold microparticles) are irradiated with light of a specific wavelength, the free electrons of the gold nanoparticles form surface plasmon polaritons, which vibrate through the resonant light. This results in polarization. The energy of this polarization is converted into the energy of lattice vibrations through the Coulomb interaction between the free electrons and the atomic nuclei. As a result, the gold nanoparticles generate heat. This effect will also be referred to below as the "photothermal effect." By utilizing the photothermal effect of gold nanoparticles, it is possible to absorb broadband light and convert it into heat with high efficiency (see below). Figure 22 ).

[0106] Figure 11 This is a graph showing the measurement results of the absorption spectrum of the photothermal conversion element 1 manufactured according to condition 1A. Figure 12 This is a graph showing the measurement results of the absorption spectrum of the photothermal conversion element 1 manufactured according to condition 1B. Figure 13 This is a graph showing the measurement results of the absorption spectrum of the photothermal conversion element 1 manufactured according to condition 1C. Figure 14 This is a graph showing the measurement results of the absorption spectrum of the photothermal conversion element 1 manufactured according to condition 1D.

[0107] exist Figures 11-14In the figures, the upper section shows the results of local spectral measurements of the region along the black lines (the unirradiated area by pulsed laser L), and the lower section shows the results of local spectral measurements of the region between the black lines (the area where gold nanoparticles were observed). In the region along the black lines, a flat spectrum was obtained, similar to that of the unprocessed gold film. In contrast, in the region between the black lines, a broadened spectrum was observed, and a peak of local surface plasmon resonances from the gold nanoparticles was confirmed near a wavelength of 530 nm.

[0108] Thus, compared to the absorption spectrum of the region irradiated by pulsed laser L or the absorption spectrum obtained from a single metal nanoparticle, the absorption spectrum of the region irradiated by pulsed laser L is broadened and the peaks are shifted. This spectral change indicates the following.

[0109] High-density aggregation of gold nanoparticles is achieved through a physical process (non-chemical process) using only pulsed laser irradiation (L). This enhances the interaction of electron systems (such as localized surface plasmon resonances) within each gold nanoparticle via the electromagnetic field, broadening the absorption spectrum. Consequently, compared to the unprocessed solid material or individual particles, a broadband light-to-heat conversion (enhanced photothermal effect) is achieved. The blackening of the irradiated area can be visually observed as a result of this enhanced photothermal effect.

[0110] It should be noted that simply generating microparticles (gold nanoparticles in this example) from a solid material by laser irradiation does not result in blackening. Blackening occurs because the microparticles, composed of solid material, generated by laser irradiation aggregate at a high density; in other words, the microparticles are close to each other but dispersed.

[0111] By irradiating the gold film with a pulsed laser L to create microgrooves, the surface area of ​​the gold film can be increased. This means that the area of ​​the region where the generated gold nanoparticles are close to each other but can be dispersed can be increased (essentially, the area of ​​the trays for the densely aggregated gold nanoparticles). Therefore, creating microgrooves can further enhance the photothermal effect.

[0112] Next, the photothermal conversion element 2 (refer to) on the laser-processed platen after constantan processing... Figure 4 and Figure 5 The evaluation results are explained. The thickness of photothermal conversion element 2 is 500 μm.

[0113] Figure 15 This is a diagram illustrating the laser processing conditions of another photothermal conversion element 2 in an embodiment of implementation 1. In this example, according to... Figure 15 Laser processing is performed under the five conditions shown in 2A to 2E.

[0114] Figure 16This is a diagram showing the observation results of the photothermal conversion element 2 in the embodiment of implementation 1. (Refer to...) Figure 16 It was confirmed that multiple micronized constantan particles were densely aggregated in the irradiation area of ​​the pulsed laser L within the photothermal conversion element 2. The size of the multiple constantan particles ranged from tens to hundreds of nanometers.

[0115] Figure 17 This is a graph showing the measurement results of the reflectance spectrum of the photothermal conversion element 2 manufactured according to conditions 2A to 2E. Figure 17 The upper section, for comparison, shows the reflectance spectrum before laser processing (the reflectance spectrum after averaging the measurement results of the three samples). The middle section shows the reflectance spectrum after laser processing. The lower section shows a magnified view of the reflectance spectra obtained from conditions 2B to 2D.

[0116] Before laser processing, the reflectivity of the photothermal conversion element 2 in the visible light region (wavelength region of 400nm to 800nm) is in the range of approximately 40% to 50%. On the other hand, if laser processing is performed, the reflectivity of the photothermal conversion element 2 in the visible light region is less than 10% in any of conditions 2A to 2E. Specifically, the average reflectivity of the photothermal conversion element 2 after laser processing according to condition 2C (taking the average reflectivity in the visible light region) is 0.42%. The average reflectivity of the photothermal conversion element 2 after laser processing according to condition 2D is 0.31%. The blackening of the photothermal conversion element 2 after laser processing is also observed visually. As a method to reduce the reflectivity of the metal plate, blackening by electroplating is known. The average reflectivity of constantan blackened by electroplating is approximately 2%. Therefore, it can be said that the average reflectivity obtained by conditions 2C and 2D is significantly lower than the average reflectivity achievable by electroplating. It can be assumed that these significant reductions in reflectivity are due to the broadening and peak shift of the absorption spectrum of constantan particles generated by laser processing and with high density, compared to the absorption spectrum obtained from a single constantan particle.

[0117] Furthermore, compared with the laser output P in condition 2A out For a relative output of 400mW, the laser output P in conditions 2B to 2E is... out 800mW (reference) Figure 15 Since the average reflectivity of the photothermal conversion element 2 after laser processing according to conditions 2B-2E is lower than that after laser processing according to condition 2A, it can be concluded that there is laser output P. out There is a tendency for higher average reflectance to be lower.

[0118] The average reflectivity of the photothermal conversion element 2 after laser processing according to conditions 2C and 2D is particularly low, less than 0.5%. In conditions 2C and 2D, the scanning interval D of the pulsed laser L is dense (D = 50 μm), and the spot diameter of the pulsed laser L is large (spot height H > 50 μm). This is attributed to the narrowing of the intervals between the regions where constantan is atomized, and the atomization of constantan occurring over a large area, thus further reducing the average reflectivity.

[0119] As described above, in Embodiment 1, a processing area LP is formed on the photothermal conversion elements 1 and 2 by scanning with a pulsed laser L. The scanning with the pulsed laser L can be performed using readily available general laser processing equipment. Furthermore, as in... Figure 8 As described, the fabrication steps of photothermal conversion elements 1 and 2 do not include chemical treatment, and the fabrication time for photothermal conversion elements 1 and 2 is approximately 10 to 20 minutes. Furthermore, compared to the photothermal conversion element disclosed in Patent Document 1, it is significantly easier in that it does not require the formation of a metal nanoparticle aggregate structure. Thus, according to Embodiment 1, photothermal conversion elements 1 and 2 can be fabricated using a simple manufacturing method.

[0120] [Implementation Method 2]

[0121] In Embodiment 2, a solar thermal power generation device capable of generating electricity using the solar thermal conversion elements 1 and 2 of Embodiment 1 will be described.

[0122] Figure 18 This is a schematic diagram showing the overall structure of the solar thermal power generation device according to Embodiment 2. (Refer to...) Figure 18 White light source 91 is a light source that emits white light WL. White light source 91 is, for example, the sun, but it can also be other light sources such as simulated sunlight illumination, incandescent lamps, white LEDs (Light Emitting Diodes), fluorescent lamps, etc. In addition, as an alternative to white light source 91, a monochromatic light source that emits light in a wavelength range including the ultraviolet to near-infrared regions can be used, or a light source that emits light in multiple wavelength ranges can be used.

[0123] The concentrated solar power (CSP) device 200 generates electricity using white light WL emitted from a white light source 91 and supplies the generated power to an electrical load 92. The CSP device 200 includes a photothermal conversion unit 210 and a thermoelectric conversion unit 220. The photothermal conversion unit 210 receives the white light WL emitted from the white light source 91 and generates heat through the photothermal effect. The thermoelectric conversion unit 220 converts the heat energy generated by the photothermal conversion unit 210 into electrical energy. In other words, the thermoelectric conversion unit 220 generates electricity using the heat from the photothermal conversion unit 210. This electricity is supplied to the electrical load 92.

[0124] The electrical load 92 can be a circuit or a motor, but it is not particularly limited to any device that consumes electricity. Furthermore, although not shown, as an alternative to the electrical load 92, an energy storage device (such as a secondary battery) that stores electricity supplied from the solar thermal power generation unit 200 may be connected to the solar thermal power generation unit 200. The electrical load 92 or the energy storage device is equivalent to the "load" in this disclosure.

[0125] Figure 19 This is a diagram showing an example of a more detailed structure of the concentrated solar power (CSP) device 200. (Refer to...) Figure 19 In this example, the photothermal conversion unit 210 includes a photothermal conversion element 1. The substrate 11 of the photothermal conversion element 1 can be, for example, a conductive film (ITO-PEN film, etc.).

[0126] The thermoelectric conversion unit 220 includes a P-type thermoelectric element 221, an N-type thermoelectric element 222, a heat sink 223, electrodes 231 to 234, and conductive pastes 241, 242A, 242B, 243, 244A, and 244B.

[0127] The P-type thermoelectric element 221 is thermally and electrically connected to the electrode 231 via conductive paste 241. The electrode 231 is thermally and electrically connected to the substrate 11 (conductive film) of the photothermal conversion element 1. Furthermore, the P-type thermoelectric element 221 is thermally and electrically connected to the electrode 232 via conductive paste 242A. The electrode 232 (first electrode) is thermally connected to the heat sink 223 via conductive paste 242B, but is electrically insulated from the heat sink 223.

[0128] Similar to the P-type thermoelectric element 221, the N-type thermoelectric element 222 is thermally and electrically connected to the electrode 233 via conductive paste 243. The electrode 233 is thermally and electrically connected to the substrate 11 of the photothermal conversion element 1. The N-type thermoelectric element 222 is thermally and electrically connected to the electrode 234 via conductive paste 244A. The electrode 234 (the second electrode) is thermally connected to the heat sink 223 via conductive paste 244B, but is electrically insulated from the heat sink 223.

[0129] The heat sink 223 is formed of an insulating material (e.g., aluminum oxide).

[0130] White light WL emitted from white light source 91 irradiates the metal thin film 12 of photothermal conversion element 1. This generates localized surface plasmon resonance of multiple particles (e.g., gold nanoparticles or gold microparticles) in the processing area LP, thereby enhancing heat generation (photothermal effect). The heat generated by photothermal conversion element 1 is transferred to P-type thermoelectric element 221 and N-type thermoelectric element 222. Thus, a temperature difference is generated between the two ends of each of P-type thermoelectric element 221 and N-type thermoelectric element 222. More specifically, in P-type thermoelectric element 221, the temperature of the side of P-type thermoelectric element 221 closest to photothermal conversion element 1 (the side with electrode 231 and conductive paste 241) increases as photothermal conversion element 1 is heated. On the other hand, the temperature of the side of P-type thermoelectric element 221 closest to heat sink 223 (the side with conductive paste 242A, electrode 232, and conductive paste 242B) decreases due to heat dissipation from heat sink 223. This also applies to the N-type thermoelectric element 222.

[0131] Hereinafter, the side of the P-type thermoelectric element 221 or the N-type thermoelectric element 222 that is closer to the photothermal conversion element 1 will also be referred to as the "high temperature side", and the side that is closer to the heat sink 223 will also be referred to as the "low temperature side".

[0132] Inside the P-type thermoelectric element 221, holes diffuse and concentrate on the low-temperature side. Therefore, in the P-type thermoelectric element 221, the potential on the low-temperature side is higher than the potential on the high-temperature side. On the other hand, inside the N-type thermoelectric element 222, electrons diffuse towards the low-temperature side. Therefore, in the N-type thermoelectric element 222, the potential on the low-temperature side is lower than the potential on the high-temperature side. As a result, a potential difference is generated between the low-temperature side of the P-type thermoelectric element 221 and the low-temperature side of the N-type thermoelectric element 222. Thus, by connecting the electrical load 92 between electrodes 232 and 234, current can be extracted from electrode 232 to the electrical load 92. In this way, the solar thermal power generation device 200 can convert light energy into heat energy, and then convert that heat energy into electrical energy.

[0133] In addition, Figure 19 The diagram shows the structure of the thermoelectric conversion unit 220, which includes a P-type thermoelectric element 221 and an N-type thermoelectric element 222. However, the thermoelectric conversion unit 220 may also include multiple sets of P-type thermoelectric elements 221 and N-type thermoelectric elements 222.

[0134] Figure 20 This is another example of a more detailed structure showing the concentrated solar power (CSP) device 200. (See reference...) Figure 20In this example, the photothermal conversion unit 210 includes a photothermal conversion element 1 and a photothermal conversion element 2 (e.g., a laser-processed flat constantan). Thus, photothermal conversion element 1 and photothermal conversion element 2 can also be combined. Furthermore, photothermal conversion element 2 can be used instead of photothermal conversion element 1. Additionally, the electrode 233 connected to photothermal conversion element 2 and the electrode 231 connected to photothermal conversion element 1 are electrically connected.

[0135] exist Figure 20 In the example shown, the photothermal conversion element 2 also functions as an N-type thermoelectric element. That is, the photothermal conversion element 2 and the N-type thermoelectric element 222 are integrally formed, thereby realizing a "photothermal conversion thermoelectric element". In addition, although the photothermal conversion element 2 and the N-type thermoelectric element 222 are integrally formed in this example, depending on the material of the photothermal conversion element 2, it is also possible that the photothermal conversion element 2 and the P-type thermoelectric element 221 are integrally formed.

[0136] As in Figure 19 As explained, when the photothermal conversion element 1 and the N-type thermoelectric element 222 are each constructed separately, the photothermal conversion element 1 and the N-type thermoelectric element 222 are thermally connected via the substrate 11. The thermal conductivity of the substrate 11 is lower than that of most metals. Specifically, constantan has a thermal conductivity of 23 [W / m·K], while glass has a thermal conductivity of 1.0 [W / m·K], and PET (polyethylene terephthalate) film has a thermal conductivity of 0.20 to 0.33 [W / m·K]. Therefore, by integrally constructing the photothermal conversion element 2 and the N-type thermoelectric element without using the substrate 11, heat energy can be transferred more efficiently compared to a structure in which the photothermal conversion element 1 and the N-type thermoelectric element 222 are each constructed separately.

[0137] <Simulation of Photothermal Conversion>

[0138] When white light (sunlight) is irradiated onto the solar thermal power generation device 200, estimate how much the temperature of the photothermal conversion element 2 included in the solar thermal power generation device 200 will rise from room temperature. The results will be explained.

[0139] Figure 21 This is a diagram illustrating the simulation conditions used to explain the temperature rise caused by the photothermal effect of photothermal conversion element 2. (Refer to...) Figure 21 Let the illumination time of white light WL from white light source 91 be t [s], and let the illuminance of white light WL (sunlight in this example) be P(λ) [W / m]. 2 The area of ​​the white light WL irradiation surface (the area of ​​the processing region LP) in the photothermal conversion element 2 is set as S[m]. 2 Additionally, λ[m] is the wavelength of white light WL.

[0140] Furthermore, the absorptivity of the photothermal conversion element 2 for white light WL is set as A(λ) [%). The absorptivity A is expressed using reflectivity R and transmittance T as A = 1 - RT. In the case where the photothermal conversion element 2 is a plate-shaped constantan, since transmittance T ≒ 0, the absorptivity A ≒ 1 - R can be approximated. Therefore, based on the measured results of the reflectivity R of the photothermal conversion element 2 (refer to...), Figure 17 Calculate the absorption rate A.

[0141] In this case, the heat absorption Q[J] of the photothermal conversion element 2 is calculated according to the following formula (1).

[0142] [Mathematical Expression 1]

[0143]

[0144] Furthermore, when the specific heat capacity of the photothermal conversion element 2 is set to C [J / K·g] and the mass of the photothermal conversion element 2 is set to m [g], the temperature rise T of the photothermal conversion element 2, based on room temperature (25℃), is... up [K] can be calculated using the following formula (2).

[0145] T up =Q / (C×m)···(2)

[0146] In this simulation, the irradiation time of white light WL is set to t = 120 [s]. The area of ​​the irradiated surface of the photothermal conversion element 2 is set to S = 3.2 × 10⁻⁶. -4 [m 2 The specific heat capacity of the photothermal conversion element 2 is set to C = 0.41 [J / g·K], and the mass of the photothermal conversion element 2 is set to m = 1.4 [g].

[0147] Figure 22 This represents the temperature rise T of the photothermal conversion element 2. up The simulation results are shown in the figure. (Refer to...) Figure 22 The figure on the left shows the calculated temperature rise of the unprocessed constantan substrate (the substrate without the processing area LP) for the comparative example, which is approximately 27°C. In contrast, in the photothermal conversion element 2 that underwent laser processing, regardless of the laser processing conditions (conditions 2A to 2E, see reference 2A to 2E)... Figure 15 Which of the following conditions determines the temperature rise T? up All are above 45℃.

[0148] In addition, Figure 21 as well as Figure 22 The example using photothermal conversion element 2 will be explained below. However, photothermal conversion element 1 (see reference 1) can also be used. Figure 2 and Figure 3The photothermal conversion element 1 can be replaced by a metal thin film 12 disposed on the photothermal conversion element 1. By irradiating light onto the metal thin film 12 disposed on the photothermal conversion element 1, heat can also be generated efficiently using the photothermal effect.

[0149] <Simulation of Photothermal-Electroelectric Conversion>

[0150] Next, the simulation results of the power generation (output power) of the solar thermal power generation device 200 under the condition of irradiating white light WL (sunlight) onto the solar thermal power generation device 200 will be explained.

[0151] Figure 23 This is a diagram illustrating the simulation conditions for the power generation generated by the photothermal-electric conversion (photothermal conversion and thermoelectric conversion) of the concentrated solar power (CSP) device 200. (Refer to...) Figure 23 The material properties of the P-type thermoelectric element 221 and the N-type thermoelectric element 222 are set as follows.

[0152] The Seebeck coefficient S(T) of the N-type thermoelectric element 222 is set to -40 × 10⁻⁴. -6 ~-36×10 -6 [V / K]. Resistivity is set to ρ = 0.44 × 10⁻⁶. -6 ~0.46×10 -6 [Ω·m]. The thermal conductivity κ is set to 23–27 [W / m·K]. This thermal conductivity κ is a two-digit higher value compared to the thermal conductivity of PET film (≒0.20–0.33 [W / m·K]).

[0153] Similarly, the Seebeck coefficient S(T) for the P-type thermoelectric element 221 is set to 1.7 × 10⁻⁶. -6 ~2.4×10 -6 [V / K]. Resistivity is set to ρ = 17 × 10⁻⁶. -9 ~24×10 -9 [Ω·m]. The thermal conductivity κ is set to 400 [W / m·K].

[0154] Furthermore, regarding thermal conditions, the temperatures of the P-type thermoelectric element 221 and the N-type thermoelectric element 222, respectively, are used in... Figure 22 The temperature rise T described in the text up To perform the calculation (temperature = room temperature + temperature rise T) up The heat flux input to or output to the P-type thermoelectric element 221 and the N-type thermoelectric element 222 is calculated by dividing the heat absorption Q (refer to formula (1)) by the area S of the irradiated surface of the white light WL.

[0155] Furthermore, the P-type thermoelectric element 221 and the N-type thermoelectric element 222 are both designed as cuboids. Moreover, the cross-sectional area (area S) of the cuboid is set to 1 × 3 mm. 2Set the height of the cuboid to 4 mm.

[0156] Figure 24 This is a graph showing the simulation results of the power generation of the concentrated solar power (CSP) device 200. Figure 24 In the diagram, the horizontal axis represents the output current of the concentrated solar power (CSP) device 200. The left vertical axis represents the output voltage of the CSP device 200, and the right vertical axis represents the output power of the CSP device 200. For example... Figure 24 As shown, in the solar thermal power generation device 200, compared with the case of using an unprocessed constantan substrate (comparative example), the output power is more than 3 times higher.

[0157] As described above, according to Embodiment 2, the solar thermal power generation device 200, by using a solar thermal conversion unit 210 that includes a laser-processed solar thermal conversion element 2 (or solar thermal conversion element 1), can efficiently convert light into heat compared to a comparative example without laser processing, and can increase the heat generation of the solar thermal conversion element 2 (see reference). Figure 22 Furthermore, by converting the increased heat into electricity through the thermoelectric conversion unit 220, the power generation capacity can be increased (see reference). Figure 24 Thus, according to embodiment 2, light can be converted into electricity with high efficiency.

[0158] [Implementation Method 3]

[0159] In Embodiment 3, a micro-object aggregation system for aggregating multiple micro-objects contained in a liquid using the photothermal conversion element 1 of Embodiment 1 will be described. In the following example, beads (microbeads) with a size on the micrometer scale are aggregated.

[0160] Figure 25 This is a diagram showing the overall structure of the micro-object aggregation system of Embodiment 3. (Refer to...) Figure 25 The focusing system 300 includes an XYZ axis platform 310, an adjustment mechanism 320, a laser light source 330, an illumination light source 340, optical components 350, an objective lens 360, a camera 370, and a control device 380.

[0161] The XYZ axis platform 310 holds the photothermal conversion element 1. Furthermore, the XYZ axis platform 310 is equivalent to the "holding element" of this disclosure.

[0162] Figure 26 This is an enlarged view of the photothermal conversion element 1 held on the XYZ axis platform 310. (See image below.) Figure 26 As shown, sample SP is dropped onto photothermal conversion element 1. Microbeads B are dispersed in sample SP. In one embodiment (see...) Figure 27 In the sample SP, the material of microbead B is polystyrene, and the diameter of microbead B is 1 μm. The dispersion medium of sample SP is pure water.

[0163] Back Figure 25 The adjustment mechanism 320 adjusts the positions of the XYZ axis platform 310 in the x, y, and z directions according to the instructions of the control device 380. In this embodiment, the position of the objective lens 360 is fixed. Therefore, the relative positional relationship between the photothermal conversion element 1 and the objective lens 360 is adjusted by adjusting the position of the XYZ axis platform 310. The adjustment mechanism 320 can also adjust the position of the objective lens 360 relative to the fixed photothermal conversion element 1.

[0164] The laser source 330 emits laser L1 according to the instructions of the control device 380. The wavelength of laser L1 is, for example, a wavelength included in the near-infrared region (1064 nm in this embodiment). In addition, the laser source 330 is equivalent to the "light source" of this disclosure.

[0165] The illumination source 340 emits white light L2 to illuminate the sample SP on the photothermal conversion element 1, according to the instructions of the control device 380. As an example, a halogen lamp can be used as the illumination source 340.

[0166] Optical components 350 include, for example, mirrors, dichroic mirrors, prisms, and optical fibers. The optical system of the focusing system 300 is configured to guide the laser L1 from the laser source 330 to the objective lens 360 via optical components 350.

[0167] Objective lens 360 converges laser L1 from laser source 330. The light converged by objective lens 360 is irradiated onto sample SP on photothermal conversion element 1. Objective lens 360 is also used to obtain white light L2 irradiated from illumination source 340 onto photothermal conversion element 1. White light L2 obtained by objective lens 360 is guided to camera 370 by optical component 350.

[0168] The camera 370 takes a picture of the sample SP on the photothermal conversion element 1 that is irradiated with white light L2 according to the instructions of the control device 380, and outputs the captured image to the control device 380.

[0169] Although not shown in the figures, the control device 380 is a microcomputer including a processor such as a CPU, memory such as ROM and RAM, and input / output ports. The control device 380 controls the various devices in the aggregation system 300 (adjustment mechanism 320, laser light source 330, illumination light source 340, and camera 370).

[0170] The thickness of the metal thin film 12 is specified such that the processing area LP is transparent to light relative to the laser L1. In the following example, the thickness of the gold thin film is 100 nm. Thus, by making the processing area LP transparent, as... Figure 25As shown, the laser L1 can be irradiated onto the processing area LP from below and above, and the processing area LP can be observed from below by the camera 270.

[0171] Figure 27 This is a photograph of the sample SP under laser L1 irradiation. As photothermal conversion element 1, it is prepared for use in... Figure 9 and Figure 10 The components are fabricated under four laser processing conditions as described. The output P of the laser L1 irradiating the photothermal conversion element 1. out The power is 50mW. The objective lens has a magnification of 40x (360°). The irradiation time of laser L1 is 100 seconds.

[0172] The generation of microbubbles (MBs) was confirmed by irradiating the region between the black lines observed due to pulsed laser L with laser L1 (which may also generate gold microparticles). Furthermore, the aggregation of microbeads (B) towards the microbubbles (MBs) was observed. The aggregation mechanism of microbeads (B) is explained below.

[0173] Figure 28 This is a conceptual diagram used to illustrate the aggregation mechanism of microbeads B. (See reference...) Figure 28 When laser L1 irradiation begins, the area near the laser spot is locally heated due to the photothermal effect. As the temperature of the liquid surrounding this heated area (sample SP) rises, microbubbles (MB) are generated. These microbubbles (MB) continue to grow near the laser spot over time.

[0174] The closer to the laser spot, the higher the temperature of the liquid. That is, a temperature gradient is generated in the liquid due to light irradiation. This temperature gradient causes stable, regular thermal convection to occur in the liquid. As indicated by arrow AR, the direction of thermal convection is towards and away from the laser spot. Therefore, microsphere B is carried on thermal convection and transported towards the laser spot.

[0175] Between the microbubble MB and the metal film 12, a circumferential "stagnant region" with zero convection velocity is generated. Because thermal convection is blocked by the microbubble MB, some of the microbeads B transported to the laser spot remain near the stagnant region. As a result, the microbeads B aggregate near the laser spot. Further details regarding the aggregation mechanism of the microbeads B can be found, for example, in Patent Document 2 or Patent Document 3.

[0176] As described above, in Embodiment 3, microbubbles MB are generated and convection occurs through the photothermal effect of the photothermal conversion element 1. Through this convection, multiple microbeads B dispersed in the sample SP are aggregated in the stagnant region generated at the bottom of the microbubbles MB. By utilizing this mechanism, a large number of microbeads B can be aggregated efficiently.

[0177] The embodiments disclosed herein should be understood as exemplary and not restrictive in all respects. The scope of this disclosure is defined by the claims rather than the description of the embodiments described above, and is intended to include all modifications equivalent to and within the scope of the claims.

[0178] Symbol Explanation

[0179] 1, 2: Photothermal conversion element; 11: Substrate; 12: Metal thin film; 91: White light source; 92: Electrical load; 100: Laser processing system; 110: XYZ axis platform; 120: Laser oscillator; 130: Laser driver; 140: Objective lens; 150: Scanning mechanism; 160: Control device; 200: Photothermal power generation device; 210: Photothermal conversion unit; 220: Thermoelectric conversion unit; 221: P-type thermoelectric element; 222: N Type of thermoelectric element; 223: Heat sink; 231-234: Electrode; 241, 242A, 242B, 243, 244A, 244B: Conductive paste; 300: Aggregation system; 310: XYZ axis platform; 320: Adjustment mechanism; 330: Laser light source; 340: Illumination light source; 350: Optical component; 360: Objective lens; 370: Camera; 380: Control device; LP, LP1-LP4: Processing area.

Claims

1. A method for manufacturing a photothermal conversion element, comprising: Steps for preparing solid materials; The step of forming the processed area by irradiating the solid material with a laser; The forming step includes the step of micronizing the solid material to blacken the processing area; The forming step includes scanning with the laser to cut microgrooves in the processing area.

2. The method for manufacturing a photothermal conversion element according to claim 1, wherein the solid material comprises at least one of a thermoelectric material exhibiting a thermoelectric effect and a metal thin film.

3. Photothermal conversion element, made of solid material; The solid material includes regions where the solid material is blackened by the aggregation of multiple particles composed of the solid material; The plurality of particles generate local surface plasmon resonances on their respective surfaces when irradiated with light.

4. The photothermal conversion element according to claim 3, wherein the solid material comprises at least one of a thermoelectric material exhibiting a thermoelectric effect and a metal thin film.

5. A concentrated solar power (CSP) device, capable of supplying the generated electricity to a load, possessing: The photothermal conversion element as described in claim 3 or 4; Thermoelectric conversion unit is thermally connected to the photothermal conversion element and converts heat into electricity; The thermoelectric conversion unit includes: P-type thermoelectric element, The first electrode is electrically connected to the low-temperature side of the P-type thermoelectric element. N-type thermoelectric element, The second electrode is electrically connected to the low-temperature side of the N-type thermoelectric element; The first electrode is connected to the second electrode and the load.

6. In the solar thermal power generation device according to claim 5, one of the P-type thermoelectric element and the N-type thermoelectric element and the solar thermal conversion element are integrally formed as a solar thermal conversion thermoelectric element.

7. Photothermal conversion element, possessing: substrate; A metal thin film disposed on the substrate; The metal film includes regions where the metal film is blackened by the dispersion of multiple microparticles made of the material of the metal film; The plurality of particles generate local surface plasmon resonances on their respective surfaces when irradiated with light.

8. A system for the aggregation of minute objects, which is a system for the aggregation of multiple minute objects contained in a liquid, including: A retainer is provided to hold the photothermal conversion element as described in claim 7. The light source emits light that causes localized surface plasmon resonance on the respective surfaces of the plurality of particles; The light source gathers the multiple tiny objects by illuminating the liquid with light while the liquid is held in the area, causing convection in the liquid.

9. The micro-object aggregation system according to claim 8, wherein the liquid is held on the upper surface of the region; Light from the light source shines upwards from below the region; The thickness of the metal film is specified such that the region is translucent relative to the light source.

Images