Droplet generation device, ink jet device, and liquid medicine delivery device

Abstract

To provide a droplet generation device capable of generating droplets from a liquid with an energy density higher than conventionally and preventing damaging of a component, an ink jet device, and a liquid medicine delivery device.SOLUTION: A droplet generation device 100 fully reflects an incident laser beam LSR 1 on a full-reflection surface 6A to apply evanescent light EVL seeping out from the full-reflection surface 6A to a liquid body 2 to conductive nanoparticles 7. The droplet generation device 100 excites plasmon resonance at the conductive nanoparticles 7 by means of the evanescent light EVL, increases field intensity at a position separated from the full-reflection surfacer 6A to apply energy to the liquid body 2, and forms the liquid body 2 into droplets.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a droplet generation device, an inkjet device, and a chemical solution delivery device.

Background Art

[0002] In recent years, the technology of atomizing liquids is not only used for printing in printers as an inkjet device, but also has applications in various technical fields beyond the conventional framework, such as needleless injectors, chemical solution delivery devices, three-dimensional cell arrays, printing of electric circuits on flexible substrates, semiconductor processes, etc. As a technology for atomizing liquids, for example, inkjet technology using a thermal method is known. In the inkjet technology using a thermal method, a liquid (for example, ink) is Joule-heated by a resistance wire heater, and the generation of bubbles due to the evaporation of the liquid is utilized to eject the liquid in the form of droplets from a nozzle, thereby atomizing the liquid (for example, see Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technique disclosed in Non-Patent Document 1, in Joule heating by a resistance wire, the energy density is low, and it is difficult to generate droplets from a liquid at high speed. For this reason, there has been a problem that it is difficult to use in various other technical fields such as needleless syringes and drug delivery devices that require droplets to be ejected at high speed. On the other hand, if the energy density is simply increased, there is also a risk of damaging the components constituting the droplet generation device, and there is a possibility that the components will be damaged.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a droplet generation device, an inkjet device, and a drug delivery device that can generate droplets from a liquid with a higher energy density than conventional ones and can also prevent damage to components.

Means for Solving the Problems

[0006] The droplet generation device of the present invention is a droplet generation device that generates droplets from a liquid, and includes a total reflection surface that totally reflects laser light irradiated from a laser light source, and a total reflection prism in which the total reflection surface is disposed at a boundary with the liquid, and at least one or more conductive nanoparticles provided in an irradiation region of the laser light on the total reflection surface. By totally reflecting the laser light on the total reflection surface, evanescent light that oozes out from the total reflection surface into the liquid is irradiated onto the conductive nanoparticles, plasmon resonance is excited by the conductive nanoparticles, and the liquid is dropletized by enhancing the electric field strength at a position away from the total reflection surface.

[0007] The inkjet device of the present invention includes the above-described droplet generation device, and the liquid is ink.

[0008] The drug delivery device of the present invention includes the above-described droplet generation device, and the liquid is a drug solution.

Effects of the Invention

[0009] According to the present invention, evanescent light oozing from the irradiation region of laser light excites plasmon resonance in conductive nanoparticles to enhance the electric field strength. As a result, a high electric field strength can be realized by the interaction between the evanescent light and the conductive nanoparticles, and droplets can be generated from a liquid with a high energy density. Further, since the electric field strength can be enhanced at a position away from the total reflection surface of the total reflection prism, damage to the total reflection prism as a component can be prevented accordingly.

Brief Description of the Drawings

[0010]

Figure 1

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals are given to the same components, and redundant descriptions are omitted.

[0012] [1] Overall Configuration of the Droplet Generation Device of the Present Invention As shown in FIG. 1, the droplet generation device 100 includes a total reflection prism 1, a plurality of conductive nanoparticles 7, and a laser light source 8. In the droplet generation device 100, a liquid 2 is provided on the total reflection surface 6A of the total reflection prism 1. In FIG. 1, for the sake of simplicity in explaining the outline of the present invention, a configuration is adopted in which the liquid 2 is simply placed on the upper part of the total reflection prism 1 using surface tension.

[0013] The total reflection prism 1 has a configuration in which a flat transmissive plate 6 is provided on the flat surface of the lens portion 4 via an immersion liquid 5. The lens portion 4 according to the present embodiment is made of a light transmissive member such as glass and is formed in a hemispherical shape. The immersion liquid 5 is made of, for example, a refractive index matching oil such as silicone oil and is provided between the flat surface of the lens portion 4 and the transmissive plate 6 without a gap. The immersion liquid 5 prevents a gap from being formed between the lens portion 4 and the transmissive plate 6 and prevents the transmissive plate 6 from shifting in the lens portion 4. The transmissive plate 6 is formed of a flat glass substrate or the like. The transmissive plate 6 has its back surface provided on the flat surface of the lens portion 4 via the immersion liquid 5, and a plurality of conductive nanoparticles 7 are provided on the surface 6A facing the back surface.

[0014] The laser light source 8 irradiates the lens portion 4 with a laser beam LSR1 composed of pulsed laser light having a period of about 10 nanoseconds (for example, Nd:YAG pulsed laser light or the like). The laser light source 8 according to the present embodiment is configured to be movable circularly linearly around the origin O along the curved surface of the hemispherical lens portion 4, and the incident angle θ of the laser beam LSR1 can be changed from an incident angle of 0° to an incident angle of 90° with respect to the origin O.

[0015] The laser beam LSR1 emitted from the laser light source 8 is incident on the total reflection prism 1. The total reflection prism 1 transmits the laser beam LSR1 through the lens portion 4 and the immersion liquid 5 and reaches the transmissive plate 6, and totally reflects it at the surface 6A of the transmissive plate 6 provided with the conductive nanoparticles 7. Hereinafter, the surface 6A where the laser beam LSR1 is totally reflected in the total reflection prism 1 is referred to as the total reflection surface 6A. The total reflection prism 1 emits the laser beam LSR2 totally reflected at the total reflection surface 6A to the outside of the lens portion 4 through the transmissive plate 6, the immersion liquid 5, and the lens portion 4. Hereinafter, the laser beam LSR1 incident on the total reflection prism 1 is also referred to as the incident laser beam LSR1, and the laser beam LSR2 totally reflected by the total reflection prism 1 and emitted from the total reflection prism 1 is also referred to as the emitted laser beam LSR2.

[0016] The total reflection prism 1 makes the incident laser light LSR1 incident at an angle equal to or greater than the critical angle, totally reflects the incident laser light LSR1 on the total reflection surface 6A, and allows the evanescent light EVL to ooze out from the total reflection surface 6A toward the liquid 2 side. The evanescent light EVL is known as non-propagating light localized near the total reflection point. Here, the principle of the generation of the evanescent light EVL will be described. Here, the direction of the electric field of the laser lights LSR1 and LSR2 is taken as the y-axis direction, the direction in which the evanescent light EVL oozes out is taken as the z-axis direction, and the direction orthogonal to the y-axis direction and the z-axis direction is taken as the x-axis direction for explanation.

[0017] The evanescent light EVL is light that oozes out toward the liquid 2 and rapidly attenuates when the incident laser light LSR1 irradiated on the total reflection prism 1, which is the medium 1, is totally reflected on the total reflection surface 6A and exits as the reflected laser light LSR2 in a system composed of the total reflection prism 1 and the liquid 2, which is the medium 2 having a refractive index lower than that of the total reflection prism 1. The penetration thickness Λ of the evanescent light EVL (the distance from the total reflection surface 6A when the evanescent light EVL is attenuated to 1 / e) is defined by the following formula (1).

[0018]

Equation

[0019] Here, in order to realize the penetration depth Λ (824 nm) of the evanescent light EVL described above, for example, it is desirable to set the laser output of the incident laser beam LSR1 to about 5 MW. However, simply irradiating the total reflection surface 6A with a high-energy incident laser beam LSR1 may cause the following problems. Here, as shown in FIG. 2, the configuration will be described in which the conductive nanoparticles 7 are not provided on the total reflection surface 6A of the total reflection prism 1 (the total reflection surface 6A in FIG. 2).

[0020] When such a high-energy incident laser beam LSR1 is incident on the total reflection prism 1, as shown in FIG. 2, within the total reflection prism 1 near the total reflection surface 6A in the irradiation region of the incident laser beam LSR1, the incident laser beam LSR1 and the reflected laser beam LSR2 overlap (the cross-hatched region in FIG. 2). For this reason, the electric field strength in the region where the laser beams LSR1 and LSR2 overlap within the total reflection prism 1 becomes 1.75 times stronger.

[0021] In the configuration of FIG. 2, the electric field strength of the evanescent light EVL that leaks into the liquid 2 becomes maximum in the vicinity of the total reflection surface 6A, and rapidly decreases as it moves away from the total reflection surface 6A in the z-axis direction. For this reason, the evanescent light EVL has the maximum electric field strength in the vicinity of the total reflection surface 6A of the total reflection prism 1, and there is a problem that the total reflection surface 6A of the total reflection prism 1 may be damaged by the incident laser light LSR1, the reflected laser light LSR2, and the evanescent light EVL.

[0022] To address the above problem, as shown in FIG. 1, in the droplet generation device 100 according to the present embodiment, conductive nanoparticles 7 are provided on the total reflection surface 6A of the total reflection prism 1, and the evanescent light EVL that leaks from the total reflection surface 6A into the liquid 2 is irradiated onto the conductive nanoparticles 7. In the droplet generation device 100 according to the present embodiment, the focused pulsed laser light that is periodically irradiated at short time intervals enters the lens unit 4 as the incident laser light LSR1, and the focused incident laser light LSR1 is irradiated onto a small area region of the total reflection surface 6A. As a result, the evanescent light EVL with a high energy density confined in an extremely small region of the penetration thickness Λ (nm) is irradiated onto the conductive nanoparticles 7, and plasmon resonance is excited in the conductive nanoparticles 7, enhancing the electric field strength by the interaction between the evanescent light EVL and the conductive nanoparticles 7.

[0023] At this time, in the droplet generation device 100, the electric field strength can be enhanced at a position away from the total reflection surface 6A of the total reflection prism 1 (around the side surface of the conductive nanoparticles 7 away from the total reflection surface 6A) by the interaction between the evanescent light EVL and the conductive nanoparticles 7, so that the liquid 2 can be dropletized, and the droplet 3 can be ejected from the liquid 2 in the direction of the z-axis (the direction away from the total reflection surface 6A).

[0024] From the above, the droplet generation device 100 can enhance the electric field strength at a position away from the total reflection surface 6A by the interaction between the evanescent light EVL and the conductive nanoparticles 7, so that the droplet 3 can be ejected while preventing damage to the total reflection surface 6A.

[0025] Regarding the conductive nanoparticles 7 according to the present embodiment, if free electrons exist inside the particles, surface plasmon resonance is excited. Therefore, for example, in addition to metallic nanoparticles such as gold, iron, and aluminum, various other conductive nanoparticles such as non-metallic nanoparticles such as carbon can be applied. Further, the conductive nanoparticles 7 according to the present embodiment are formed in a spherical shape, and when formed in a spherical shape, it is desirable that the diameter is equal to or less than the penetration thickness Λ reached by the evanescent light EVL (in this embodiment, 1 μm or less). In the case of the present embodiment, a plurality of conductive nanoparticles 7 are fixed to the total reflection surface 6A of the total reflection prism 1. Note that conductive nanoparticles according to other embodiments will be described later.

[0026] Next, a method for fixing the conductive nanoparticles 7 to the total reflection surface 6A will be described. For example, a dispersion liquid in which a plurality of conductive nanoparticles 7 are dispersed is prepared in a solvent such as an organic solvent such as ethanol or toluene, or a surfactant solution that prevents aggregation of the particles. Then, the transmission plate 6 is ultrasonically cleaned with acetone and pure water. The prepared dispersion liquid is dropped onto the total reflection surface 6A of the transmission plate 6 and left to dry naturally. By repeating the dropping and natural drying of the dispersion liquid a plurality of times, a plurality of conductive nanoparticles 7 can be fixed on the total reflection surface 6A.

[0027] For example, assuming that the number of conductive nanoparticles 7 contained in 1 ml of the dispersion liquid is estimated to be 4×10 8 pieces, if these conductive nanoparticles 7 are assumed to spread uniformly on the total reflection surface 6A, the distance between the conductive nanoparticles 7 on the total reflection surface 6A is 400 nm. Here, FIG. 3 is a photograph of the total reflection surface 6A when a plurality of conductive nanoparticles 7 are fixed to the total reflection surface 6A along the above-described steps, taken with an atomic force microscope (AFM). Here, dropping and natural drying of a dispersion liquid (manufactured by Sigma-Aldrich) in which a plurality of conductive nanoparticles (gold nanoparticles) having a diameter of 100 nm are dispersed were repeated six times, and a plurality of conductive nanoparticles 7 were fixed to the total reflection surface 6A of the transmission plate 6. From FIG. 3, it was confirmed that the conductive nanoparticles 7 aggregate in units of several pieces and are distributed on the total reflection surface 6A.

[0028] The output of the laser from the laser light source 8 is preferably 3.5 MW or more and 5.0 MW or less. If the output of the laser is less than 3.5 MW, it is not preferable because the energy density of the local heat source due to the interaction between the conductive nanoparticles and the evanescent light cannot boil the liquid 2. If the output of the laser exceeds 5.0 MW, the lens unit 4 and the transmission plate 6 will be damaged by a single laser irradiation, which is not preferable. Therefore, the output of the laser from the laser light source 8 is preferably within the above numerical range. The calculation of 3.5 MW and 5.0 MW of the laser output is the value obtained by dividing the values actually measured with a power meter of 21 mJ and 30 mJ by 6 nanoseconds, respectively.

[0029] [2] Verification test Next, a verification test was conducted to confirm that the droplet generation device 100 described above was fabricated and droplets 3 could be generated from the liquid 2. As the lens unit 4, a hemispherical glass lens with a radius of 5 mm was used. As the transmission plate 6, a glass plate with a thickness of 1 mm was used. As the immersion liquid 5 for closely attaching the transmission plate 6 to the flat surface of the lens unit 4, an oil for immersion microscopy called benzyl benzoate was used. Approximately 0.02 ml of water was dropped and placed on the total reflection surface 6A as the liquid 2 on the transmission plate 6.

[0030] As the laser light source 8, a device that irradiates Nd:YAG laser light with a wavelength of 1064 nm as the incident laser light LSR1 was used. The output of the laser from the laser light source 8 was 3.8 MW. As shown in FIG. 1, the incident laser light LSR1 emitted from the laser light source 8 was irradiated from the curved surface of the hemispherical lens unit 4 toward the origin O, and was irradiated onto the conductive nanoparticles 7 (1 mm 2 ) fixed on the total reflection surface 6A of the transmission plate 6 with the origin O as the center. The incident angle θ of the incident laser light LSR1 with respect to the surface normal O1 of the total reflection surface 6A at the origin O was adjusted to the incident angle at which the incident laser light LSR1 is totally reflected by the total reflection surface 6A.

[0031] Under such conditions, the incident laser light LSR1 was irradiated from the laser light source 8, and the liquid 2 placed on the total reflection surface 6A at this time was continuously imaged with a high-speed camera. As a result, a photograph as shown in FIG. 4 was obtained. From the photograph shown in FIG. 4, it was confirmed that the droplets 3 were ejected from the liquid 2 at a high speed in the z-axis direction by 20 cm. Thus, it was confirmed that the interaction between the evanescent light EVL and the conductive nanoparticles 7 can impart high energy to the liquid 2 to cause the inkjet phenomenon. At this time, it was also confirmed that the total reflection surface 6A was not damaged.

[0032] In this system, when the laser light LSR1 was irradiated without previously arranging the conductive nanoparticles 7 on the total reflection surface 6A of the transmission plate 6, it was confirmed that damage occurred in the vicinity of the total reflection surface 6A of the transmission plate 6.

[0033] [3] Confirmation of the enhancement effect of the electric field strength due to the interaction between the evanescent light and the conductive nanoparticles Next, using wave optics simulation software (manufactured by COMSOL), a simulation was performed to confirm the magnification of the electric field strength generated by the plasmon resonance excited by the conductive nanoparticles 7 when the evanescent light EVL was irradiated on the conductive nanoparticles 7. Here, for the simulation, attention was paid only to the vicinity of the total reflection surface 6A of the total reflection prism 1 in the configuration of the droplet generation device 100 shown in FIG. 1, and a spherical conductive nanoparticle 7 was provided on the total reflection surface 6A.

[0034] FIG. 5 shows the space ER1 around the total reflection surface 6A where the simulation is performed. The total reflection prism 1 is made of glass, the liquid 2 is water, and the total reflection surface 6A corresponding to the interface between the total reflection prism 1 and the liquid 2 is an xy plane (a plane including the x-axis direction and the y-axis direction) with a side length of 750 nm. Also, the height of the total reflection prism 1 in the z-axis direction is 250 nm, and the height of the liquid 2 in the z-axis direction is 400 nm. The irradiation region by the incident laser light LSR1 is a rectangular region of 750 nm × 750 nm centered on the origin O, and the thickness Λ in the z-axis direction where the evanescent light EVL oozes out is 250 nm.

[0035] The refractive indices of the total reflection prism 1 and the liquid 2 were set to 1.51 and 1.33, respectively. As shown in Fig. 5, in the xz plane (the plane including the x-axis direction and the z-axis direction), the incident angle θ of the incident laser light LSR1 with respect to the surface normal O1 extending from the origin O of the total reflection surface 6A was changed, and the incident laser light LSR1 was irradiated onto one conductive nanoparticle 7 placed at the origin O. The diameter of the spherical conductive nanoparticle 7 was 100 nm.

[0036] Then, a simulation was conducted to examine the magnification of the increase in the electric field strength due to plasmon resonance when the incident angle θ of the incident laser light LSR1 was changed. The electric field strength of the incident laser light LSR1 was set to 23.8 V / m, and the magnification of the electric field strength was determined based on this value. The direction of the electric field was polarized in the y-axis direction.

[0037] As a result of the simulation, as shown in Fig. 6, when the incident angle θ of the incident laser light LSR1 was 0°, the magnification E0 of the increase in the electric field strength was 3.75 times. On the other hand, when the incident angle θ was 63° (equal to or greater than the critical angle of 61.7° according to Snell's law), it became 5.26 times, which was the maximum value. From the above, it was confirmed that the incident laser light LSR1 could achieve the maximum value of the electric field strength magnification by being incident at an incident angle θ equal to or greater than the critical angle at which total reflection occurs at the total reflection surface 6A. When the incident angle θ of the incident laser light LSR1 exceeded 63°, the projected area of the incident laser light LSR1 on the total reflection surface 6A became 1 / cosθ times larger, so the magnification of the electric field strength decreased rapidly.

[0038] Also, as shown in GR1 of FIG. 6, when the incident laser light LSR1 was irradiated at an incident angle of 0°, it was confirmed that the electric field intensity was uniformly distributed over the entire periphery of the conductive nanoparticles 7. Further, as shown in GR2 of FIG. 6, when the evanescent light EVL was irradiated on the conductive nanoparticles 7, it was confirmed that the electric field intensity around the conductive nanoparticles 7 became larger than that at an incident angle of 0°. Furthermore, it was confirmed that the electric field intensity was maximized at the side portion of the conductive nanoparticles 7 away from the total reflection surface 6A, and the electric field intensity at the point where the total reflection surface 6A and the conductive nanoparticles 7 were in point contact became smaller. That is, it was confirmed that the electric field intensity could be enhanced at a position away from the total reflection surface 6A in the z-axis direction. Here, if the electric field intensity at the grounding surface of the conductive nanoparticles 7 and the total reflection surface 6A becomes large, it is considered that the total reflection prism 1 will be damaged. From the above, since the electric field intensity can be enhanced at a position away from the total reflection surface 6A in the z-axis direction, it was confirmed that the damage to the total reflection prism 1 can be prevented accordingly.

[0039] Next, a simulation was performed on how much the electric field intensity increases when the incident laser light LSR1 is irradiated on a plurality of conductive nanoparticles 7. Here, a simulation was performed for the case where two conductive nanoparticles 7 were arranged in the space ER1 around the total reflection surface 6A as shown in FIG. 7. The conductive nanoparticle 7 shown on the left side of FIG. 8 indicates one conductive nanoparticle 7 whose electric field intensity was examined in the above-described simulation. The two conductive nanoparticles 7 shown in the center and on the right side of FIG. 8 indicate the arrangement of the conductive nanoparticles 7 whose electric field intensity is examined in the simulation here. The center of FIG. 8 shows a simulation model 7A in which two conductive nanoparticles 7 are arranged along the direction of the electric field of the incident laser LSR1 (y-axis direction). The right side of FIG. 8 shows a simulation model 7B in which two conductive nanoparticles 7 are arranged along the x-axis direction orthogonal to both the direction of the electric field of the incident laser light LSR1 (y-axis direction) and the z-axis direction.

[0040] The simulation conditions were the same as those of the simulation described in Fig. 5. Fig. 9 is a schematic diagram when the simulation model 7A is placed in the spatial ER1. In the simulation model 7A, for the case where the incident angle θ of the incident laser light LSR1 is 0°, and the case where the incident angle θ is 63° (equal to or greater than the critical angle of 61.7° according to Snell's law), the magnification of the electric field strength was obtained by changing the distance between the conductive nanoparticles 7, respectively. The magnification of the electric field strength was obtained with the electric field strength of the incident laser light LSR1 set to 23.8 V / m and using this value as a reference. The distance between the conductive nanoparticles 7 is the distance in nm between the side surface of one conductive nanoparticle 7 and the side surface of the other conductive nanoparticle 7. When the distance between the conductive nanoparticles 7 is 0 nm, it indicates a state where the conductive nanoparticles 7 are arranged in contact with each other's side surfaces.

[0041] As a result, the results as shown in Fig. 10 were obtained. From the results of Fig. 10, it was confirmed that even when the incident angle θ of the incident laser light LSR1 is 0° where the evanescent light EVL does not occur, the electric field strength increases. However, it was confirmed that the electric field strength increases significantly when the incident angle θ of the incident laser light LSR1 is 63° where the evanescent light EVL leaks out, rather than setting it to 0° where the evanescent light EVL does not occur. Also, it was confirmed that the electric field strength increases significantly by setting the distance between the conductive nanoparticles 7 to 0.5 nm or less.

[0042] Also in the simulation model 7B, similar to the simulation model 7A, for the case where the incident angle θ of the incident laser light LSR1 is 0°, and the case where the incident angle θ is 63° (equal to or greater than the critical angle of 61.7° according to Snell's law), the magnification of the electric field strength was obtained by changing the distance between the conductive nanoparticles 7, respectively. As a result, when the two conductive nanoparticles 7 are arranged without being aligned with the direction of the electric field (y-axis direction) of the incident laser light LSR1, it was confirmed that by setting the incident angle θ of the incident laser light LSR1 to 63°, the electric field strength becomes almost the same as the simulation result when there is one conductive nanoparticle 7. In the simulation model 7B, when the incident angle θ of the incident laser light LSR1 is 0°, a significant enhancement of the electric field strength could not be confirmed.

[0043] From the above, it was confirmed that in order to significantly increase the electric field strength, it is preferable to set the incident angle θ of the incident laser beam LSR1 to be equal to or greater than the critical angle from which the evanescent light EVL oozes out from the total reflection surface 6A. Further, when arranging a plurality of conductive nanoparticles 7, it was confirmed that it is more preferable because the electric field strength can be enhanced by arranging them along the direction that coincides with the direction of the electric field of the incident laser beam LSR1.

[0044] Next, as shown on the left side of FIG. 11, for a simulation model 7C in which six conductive nanoparticles 7 are arranged in a plane at equal intervals so as to surround the periphery of one conductive nanoparticle 7, a simulation was performed to examine the enhancement of the electric field strength under the same conditions as above. Further, as shown on the right side of FIG. 11, for a simulation model 7D in which six conductive nanoparticles 7 are arranged in a plane at equal intervals so as to surround the periphery of one conductive nanoparticle 7, and further twelve conductive nanoparticles 7 are arranged in a plane at equal intervals so as to surround the periphery thereof, a simulation was also performed to examine the enhancement of the electric field strength under the same conditions as above.

[0045] Note that in both the simulation models 7C and 7D, the conductive nanoparticles 7 are arranged so as to be aligned along the direction that coincides with the direction of the electric field of the incident laser beam LSR1. As a simulation result, the results as shown in Table 1 below were obtained. In the column with the notation "pieces" in Table 1, the number of conductive nanoparticles 7 is shown.

[0046]

Table 1

[0047] From Table 1, it was confirmed that the electric field strength is enhanced when the incident angle θ of the incident laser light LSR1 is set to 63° from which the evanescent light EVL oozes out. Note that it was confirmed that the magnification of the electric field strength is significantly increased in the simulation model 7A in which two conductive nanoparticles 7 are arranged as compared with the case where the conductive nanoparticle 7 is one. In any of the simulation models 7A, 7C, and 7D, since the conductive nanoparticles 7 are arranged along the direction that coincides with the direction of the electric field of the incident laser light LSR1, the electric field strength is enhanced even when the incident angle θ of the incident laser light LSR1 is 0°. However, it was confirmed that the electric field strength is enhanced when the incident angle is set to 63° from which the evanescent light EVL oozes out.

[0048] Also, when a plurality of conductive nanoparticles 7 are arranged, it was confirmed that the enhancement effect of the electric field strength becomes low when the distance between the adjacent conductive nanoparticles 7 is 2 nm or more.

[0049] [4] Action and effect According to the above configuration, the droplet generator 100 includes a total reflection surface 6A that totally reflects the incident laser light LSR1 irradiated from the laser light source 8, a total reflection prism 1 in which the total reflection surface 6A is disposed at the boundary with the liquid 2, and at least one or more conductive nanoparticles 7 provided in the irradiation region of the laser light on the total reflection surface 6A. The droplet generator 100 irradiates the conductive nanoparticles 7 with an evanescent light EVL that oozes out from the total reflection surface 6A into the liquid 2 by totally reflecting the incident laser light LSR1 on the total reflection surface 6A. Thereby, the droplet generator 100 excites surface plasmon resonance with the conductive nanoparticles 7 by the evanescent light EVL, enhances the electric field strength at a position away from the total reflection surface 6A, gives energy to the liquid 2, and atomizes the liquid 2 into droplets.

[0050] In this way, the droplet generator 100 excites surface plasmon resonance with the conductive nanoparticles 7 and enhances the electric field strength by the evanescent light EVL that oozes out from the irradiation region of the incident laser light LSR1. As a result, a high electric field strength can be realized by the interaction between the evanescent light EVL and the conductive nanoparticles 7, and the droplets 3 can be generated from the liquid 2 with a high energy density. Further, since the electric field strength can be enhanced at a position away from the total reflection surface 6A of the total reflection prism 1, the damage to the total reflection prism 1 as a component can be prevented accordingly.

[0051] Note that, for example, in a droplet generation device of another configuration in which a simple thin film made of a conductive member is provided on the total reflection surface 6A instead of the conductive nanoparticles 7, it is difficult to confine light in the surface direction in which the thin film spreads. On the other hand, in the droplet generation device 100 according to the present embodiment, unlike the thin film, since one or more conductive nanoparticles 7 are provided on the total reflection surface 6A, light can be confined by the conductive nanoparticles 7 also in the surface direction of the total reflection surface 6A. Therefore, it can be used as a heat source that confines light in three directions: the x-axis direction, the y-axis direction, and the z-axis direction, enabling more local heating. Further, in the droplet generation device 100 according to the present embodiment, since the conductive nanoparticles 7 can be provided in point contact with the total reflection surface 6A, the enhanced electric field strength generated around the conductive nanoparticles 7 can be separated from the total reflection surface 6A. And a high electric field strength can be realized by the interaction between the evanescent light EVL and the conductive nanoparticles 7.

[0052] [5] Other embodiments [5-1] About total reflection prism In the above-described embodiment, the droplet generation device 100 to which the total reflection prism 1 including the spherical lens portion 4, the immersion liquid 5, and the transmission plate 6 is applied has been described. However, the present invention is not limited to this. For example, as shown in FIG. 12, a droplet generation device 100b including a total reflection prism 1b composed only of a quadrangular pyramid-shaped lens portion 4b may be used. Further, various total reflection prisms such as a total reflection prism composed only of a triangular pyramid-shaped lens portion may be applied to the droplet generation device. In the total reflection prism 1b, the flat surface of the lens portion 4b serves as the total reflection surface 6A, and the conductive nanoparticles 7 are provided on the total reflection surface 6A of the lens portion 4b. Even with such a configuration, the same effects as those of the above-described embodiment can be achieved.

[0053] [5-2] Application to inkjet device Next, the case where the above-described droplet generation device 100 is applied to an inkjet device will be described. FIG. 13 is a schematic diagram showing the configuration of an inkjet device 10 provided with a plurality of droplet generation devices 100c that enhance the electric field strength by the interaction between the evanescent light EVL and the conductive nanoparticles 7. In this case, the inkjet device 10 includes a plurality of droplet generation devices 100c and an ink storage unit 12 as a liquid storage unit. These plurality of droplet generation devices 100c are arranged side by side using a single total reflection prism 11 in common, and the conductive nanoparticles 7 constituting each droplet generation device 100c are arranged on the total reflection surface 6A of the total reflection prism 11 with a predetermined interval therebetween.

[0054] The plurality of droplet generation devices 100c are separated by the ink storage unit 12. The ink storage unit 12 forms a storage space on the total reflection surface 6A of the total reflection prism 11 that can store the inks 2C, 2M, 2Y, and 2K as liquids for each droplet generation device 100c. A nozzle 12A that is tapered outward is formed at the discharge port facing the total reflection surface 6A of the total reflection prism 11. The ink storage unit 12 is provided with a nozzle 12A that discharges the inks 2C, 2M, 2Y, and 2K as droplets 3, respectively, for each droplet generation device 100c. The nozzle 12A is arranged so as to face the region of the total reflection surface 6A where the conductive nanoparticles 7 are arranged.

[0055] Since the plurality of droplet generation devices 100c have the same configuration, here, attention will be paid to one droplet generation device 100c and described below. The droplet generation device 100c includes a total reflection prism 11 that is shared with other droplet generation devices 100c and conductive nanoparticles 7. The total reflection prism 11 includes a total reflection surface 6A on which the incident laser light LSR1 emitted from a laser light source 8 (not shown) is totally reflected. The conductive nanoparticles 7 are provided on the total reflection surface 6A of the total reflection prism 11 that is in contact with the ink 2C. In FIG. 13, only one conductive nanoparticle 7 is shown for each droplet generation device 100c as the conductive nanoparticles 7, but actually, a plurality of conductive nanoparticles 7 are provided according to the irradiation region of the incident laser light LSR1 (for example, area: 1 mm 2 )).

[0056] Total reflection prism 11 totally reflects incident laser light LSR1 incident at or above the critical angle as reflected laser light LSR2 on total reflection surface 6A. At this time, evanescent light EVL oozes out from total reflection surface 6A toward the ink 2C side, and the evanescent light EVL is configured to be able to irradiate conductive nanoparticles 7.

[0057] In the accommodation space of ink accommodation portion 12, inks such as cyan ink 2C, magenta ink 2M, yellow ink 2Y, and black ink 2K are accommodated as liquids, and each can be discharged as droplets 3 from each ink accommodation portion 12 through nozzle 12A. By appropriately mixing inks 2C, 2M, 2Y, and 2K with different colors, printing in the YMCK color system becomes possible. The amount of droplets 3 discharged is controlled by adjusting the irradiation amount of incident laser light LSR1 according to inks 2C, 2M, 2Y, and 2K by a discharge control device for an inkjet (not shown).

[0058] Next, the operation of this embodiment will be described. For example, in droplet generation device 100c in which ink 2C is accommodated, when incident laser light LSR1 with an incident angle θ equal to or greater than the critical angle is incident on total reflection surface 6A of total reflection prism 11, incident laser light LSR1 is totally reflected on total reflection surface 6A, and evanescent light EVL oozes out from total reflection surface 6A toward the ink 2C side in the irradiation region of incident laser light LSR1. The oozed evanescent light EVL irradiates conductive nanoparticles 7, exciting plasmon resonance in conductive nanoparticles 7 and enhancing the electric field strength at a position away from total reflection surface 6A (the side surface position of the sphere of conductive nanoparticles 7). Ink 2C is rapidly heated by the enhanced electric field strength to generate bubbles Air. Due to the generation of bubbles Air, ink 2C near nozzle 12A is extruded from nozzle 12A, becomes droplets 3, and adheres to a printing medium (not shown) to form a printed matter.

[0059] According to the present embodiment, the ink 2C can be heated with a high energy density by the interaction between the evanescent light EVL generated at the total reflection surface 6A of the total reflection prism 11 and the conductive nanoparticles 7. Therefore, the ink 2C can be ejected at high speed. Further, by enhancing the electric field strength through the interaction between the evanescent light EVL and the conductive nanoparticles 7, the electric field strength can be enhanced at a position away from the total reflection surface 6A, so that damage to the total reflection prism 11 can be prevented.

[0060] Also, by making the irradiation region of the incident laser light LSR1 as small as 1 mm 2 the distance D1 between adjacent nozzles 12A can be reduced, and accordingly, high-definition printing of a printed matter by the inkjet device 10 can be realized.

[0061] [5-3] Application to a chemical solution delivery device Next, the case where the above-described droplet generation device 100 is applied to a chemical solution delivery device will be described. FIG. 14 is a schematic diagram showing the configuration of a chemical solution delivery device 20 provided with a plurality of droplet generation devices 100d that enhance the electric field strength by the interaction between the evanescent light EVL and the conductive nanoparticles 7. The chemical solution delivery device 20 is a device for allowing a chemical solution 2D to penetrate into the skin SK of a human body. In this case, the chemical solution delivery device 20 includes a droplet generation device 100d and a chemical solution storage unit 22 as a liquid storage unit.

[0062] The chemical solution storage part 22 is, for example, a circular cylindrical microtube with both ends open, and holds the chemical solution 2D by capillary action. The droplet generator 100d includes a total reflection prism 21 and one or more conductive nanoparticles 7 provided on the total reflection surface 6A of the total reflection prism 21. The total reflection prism 21 is provided so as to block one open end of the chemical solution storage part 22 with a flat surface, and the total reflection surface 6A is arranged in the space where the chemical solution 2D of the chemical solution storage part 22 is stored. In the total reflection prism 21 according to the present embodiment, a plurality of conductive nanoparticles 7 are arranged in the region of the total reflection surface 6A arranged at the circular center of the chemical solution storage part 22. In the region where the conductive nanoparticles 7 are provided on the total reflection surface 6A, incident laser light LSR1 emitted from a laser light source (not shown) is irradiated from the total reflection prism 21 side at an incident angle θ equal to or greater than the critical angle.

[0063] In the chemical solution delivery device 20 described above, the incident laser light LSR1 incident on the total reflection prism 21 is totally reflected by the total reflection surface 6A and is emitted outside the total reflection prism 21 as the reflected laser light LSR2. As a result, at the total reflection surface 6A, evanescent light EVL oozes out toward the chemical solution 2D side, and the evanescent light EVL irradiates a plurality of conductive nanoparticles 7 to excite surface plasmon resonance. In the chemical solution delivery device 20, due to the interaction between the evanescent light EVL and the conductive nanoparticles 7, the electric field strength is enhanced at a position away from the total reflection surface 6A, and energy is given to the chemical solution 2D to generate bubbles. The chemical solution 2D held by surface tension is pushed by the generation of bubbles to become droplets 3 and is ejected at high speed, and the droplets 3 penetrate the skin SK of the human body.

[0064] According to this embodiment, in addition to the effects of the above-described embodiments, there are the following effects. In the chemical solution delivery device disclosed in the conventional non-patent document 2 ("Inkjet Printing of Viscous Monodisperse Microdroplets by Laser-Induced Flow Focusing", PHYSICAL REVIEW APPLIED 6, 024003 (2016), DOI: 10.1103 / PhysRevApplied.6.024003), laser light was irradiated from the side wall of a cylindrical microtube to cause ablation in the chemical solution. However, in reality, the region of the chemical solution heated by the laser light was biased, making it easy for turbulent flow to occur and difficult to eject droplets in an appropriate direction. In contrast, in the chemical solution delivery device 20 of this embodiment, the evanescent light EVL that oozes into the chemical solution 2D can be arranged at the circular center portion of the chemical solution storage unit 22. Therefore, since the position where the electric field strength is enhanced and the discharge port of the chemical solution storage unit 22 can be arranged in a straight line to push the chemical solution 2D linearly toward the discharge port, the generation of turbulent flow in the chemical solution 2D can be suppressed, and the discharge direction of the chemical solution 2D can be easily controlled.

[0065] [6] Conductive nanoparticles according to other embodiments In the above-described embodiment, the spherical conductive nanoparticles 7 have been described as the conductive nanoparticles, but the present invention is not limited thereto. Any conductive nanoparticles of various other shapes may be applied as long as they are conductive nanoparticles in which plasmon resonance is excited by the irradiation of evanescent light EVL oozing out from the total reflection surface 6A.

[0066] Also, for example, as shown in FIG. 15, a nanosphere having a dielectric inside 711 and a gold thin film as an outer shell 712 covering the outside of the inside 711 may be applied as the conductive nanoparticles 71, and a nanosphere having a metal inside 721 and a dielectric film as an outer shell 722 covering the outside of the inside 721 may be applied as the conductive nanoparticles 72. Furthermore, other conductive nanoparticles made of a composite material in which the inside and the outer shell are formed of various materials may be applied.

[0067] As other shapes of the conductive nanoparticles, for example, as shown on the left side of FIG. 16, rod-shaped conductive nanoparticles 73 may be used. Also, as shown in the center of FIG. 16, conductive nanoparticles 74 in which protrusions 742 such as thorns are provided on the surface of spherical conductive nanoparticles 741 may be used. Furthermore, as shown on the right side of FIG. 16, conductive nanoparticles 75 in which protrusions 752 such as thorns are provided on the surface of rod-shaped conductive nanoparticles 751 may be used. In the conductive nanoparticles 73, 74, and 75 as shown in FIG. 16, they can be fixed to the total reflection surface 6A by point contact or line contact.

Explanation of Reference Numerals

[0068] 1, 1b, 11, 21 Total reflection prism 6A Total reflection surface 2 Liquid 2C, 2M, 2Y, 2K Ink (liquid) 2D Chemical solution (liquid) 3 Droplet 7, 71, 72, 73, 74, 75 Conductive nanoparticles 10 Inkjet device 12 Ink storage section (liquid storage section) 12A Nozzle 20 Chemical solution delivery device 22 Chemical solution storage section (liquid storage section) 100, 100b, 100c, 100d Droplet generation device

Claims

1. A droplet generation device for generating droplets from a liquid, comprising a total reflection prism having a total reflection surface for totally reflecting the laser light irradiated from a laser light source, the total reflection surface being disposed at the boundary with the liquid, and at least one or more conductive nanoparticles provided in the irradiation region of the laser light on the total reflection surface, and by totally reflecting the laser light on the total reflection surface, irradiating the evanescent light that oozes out from the total reflection surface into the liquid onto the conductive nanoparticles, exciting plasmon resonance with the conductive nanoparticles, and enhancing the electric field strength at a position away from the total reflection surface to atomize the liquid, a droplet generation device.

2. The droplets are ejected in a direction away from the total reflection surface, The droplet generation device according to claim 1.

3. The conductive nanoparticles are fixed in point contact or line contact with the total reflection surface, The droplet generation device according to claim 1.

4. A plurality of conductive nanoparticles are arranged on the total reflection surface, The droplet generation device according to claim 1.

5. The plurality of conductive nanoparticles are arranged along a direction that coincides with the direction of the electric field of the laser light, The droplet generation device according to claim 4.

6. comprising a liquid storage part for storing the liquid therein, the liquid storage part includes a discharge port for discharging the liquid stored therein to the outside, in the liquid storage part, the conductive nanoparticles provided on the total reflection surface of the total reflection prism are provided so as to be disposed inside the liquid storage part, the liquid is atomized by irradiating the total reflection surface with the laser light and discharged as droplets from the discharge port, The droplet generation device according to claim 1.

7. The discharge port is provided with a nozzle that is tapered outward. The droplet generation device according to claim 6.

8. Comprising the droplet generation device according to any one of claims 1 to 7, The liquid is ink. An inkjet device.

9. Comprising the droplet generation device according to any one of claims 1 to 7, The liquid is a chemical solution. A chemical solution delivery device.

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