Bubble generation device and bubble generation method

Abstract

A bubble generation device (20) generates nanobubbles in water, and comprises: a blade member (21) that is used in a state in which at least a section thereof is immersed in the interface (WF) of water (W1); a vibration imparting unit (22) that causes the blade member (21) to vibrate in a direction substantially parallel to the interface (WF) of the water (W1); and a control unit (23) that controls the vibration imparting unit (22) so as to cause the blade member (21) to be vibrated at a prescribed frequency.

Description

Bubble generating device and bubble generating method

[0001] The present disclosure relates to a bubble generating device and a bubble generating method.

[0002] In recent years, liquids containing nanobubbles with diameters of 1 μm or less have been used for various purposes, such as cleaning, sterilization, deodorization, etc. Because these tiny nanobubbles have higher internal pressure than bubbles with larger diameters, they can remain in water for long periods of time (several hours to several weeks) without immediately disappearing, and then disappear through the processes of "rising," "contraction," and "collapse."

[0003] In this process, nanobubbles have different cleaning power and life span from, for example, microbubbles, which have a larger diameter than nanobubbles, and provide various effects such as cleaning, sterilization, deodorization, etc. For example, Patent Document 1 discloses a method for producing nanobubbles by applying physical stimuli such as discharge, ultrasonic irradiation, compression, expansion, vortex flow, etc. to microbubbles contained in a liquid, thereby rapidly shrinking the microbubbles.

[0004] International Publication No. 2005 / 084718

[0005] However, the above-mentioned conventional nanobubble production methods have the following problems: In the nanobubble production methods disclosed in the above publications, for example, microbubbles are generated simultaneously with the generation of nanobubbles, making it difficult to efficiently and stably generate nanobubbles, particularly in small amounts of water.

[0006] An object of the present disclosure is to provide a bubble generator and a bubble generating method that can generate nanobubbles efficiently and stably. (Means for Solving the Problem) The bubble generator according to the present disclosure generates nanobubbles in water and includes a blade member that is used with at least a portion immersed in the water interface, a vibration imparting unit that vibrates the blade member in a direction substantially parallel to the water interface, and a control unit that controls the vibration imparting unit to vibrate the blade member at a predetermined frequency. (Effects of the Invention) The bubble generator according to the present disclosure can generate nanobubbles efficiently and stably.

[0007] 3B. A diagram showing the structure of bubbles produced by a bubble generator according to an embodiment of the present disclosure. A schematic diagram showing the structure of a bubble generator that generates the bubbles of FIG. 1. A conceptual diagram showing a state in which a blade member included in the bubble generator of FIG. 2 is vibrated (reciprocated) in a direction perpendicular to the recess. A conceptual diagram showing a state in which a blade member included in the bubble generator of FIG. 2 is vibrated (reciprocated) in a direction parallel to the recess. A graph showing the relationship between the elapsed time and the phase of bubbles generated by vibrating the blade member in the direction of FIG. 3A. A graph showing the relationship between the number (percentage) of bubbles generated by vibrating the blade member in the direction of FIG. 3A and the DLS scattering intensity (diameter). A graph showing the relationship between the elapsed time and the phase of bubbles generated by vibrating the blade member in the direction of FIG. 3B. A graph showing the relationship between the number (percentage) of bubbles generated by vibrating the blade member in the direction of FIG. 3B and the DLS scattering intensity (diameter). A graph showing the relationship between the elapsed time and the phase of bubbles generated by vibrating the blade member of FIG. 2 in the direction shown in FIG. 3A at a frequency of 240 Hz. A graph showing the relationship between the elapsed time and the phase of bubbles generated by vibrating the blade member of FIG. 2 in the direction shown in FIG. 3A at a frequency of 240 Hz. Graph showing the relationship between the size (diameter) and the number (percentage) of bubbles corresponding to FIG. 8A generated when the blade member of FIG. 2 is vibrated in the direction shown in FIG. 3A at a frequency of 240 Hz. Graph showing the relationship between the size (diameter) and the number (percentage) of bubbles corresponding to FIG. 8A generated when the blade member of FIG. 2 is vibrated in the direction shown in FIG. 3A at a frequency of 240 Hz. Graph showing the distribution of zeta potential of bubbles generated when the blade member of FIG. 2 is vibrated in the direction shown in FIG. 3A at a frequency of 207 Hz. Graph showing the distribution of zeta potential of bubbles generated when the blade member of FIG. 2 is vibrated in the direction shown in FIG. 3A at a frequency of 207 Hz. Graph showing the relationship between the size (diameter) and the number (percentage) of bubbles corresponding to FIG. 8A ... 3 is a conceptual diagram showing the blade member of FIG. 2 being vibrated in the direction of the arrow while being submerged almost entirely below the water interface.12B is a conceptual diagram showing the blade member being vibrated in the direction of the arrow with the position of the blade member raised higher than in FIG. 12A and the recessed portion of the blade member in FIG. 2 immersed below the water interface. 12C is a conceptual diagram showing the blade member being vibrated in the direction of the arrow with the position of the blade member raised higher than in FIG. 12B and part of the recessed portion of the blade member in FIG. 2 being exposed above the water interface. 12D is a conceptual diagram showing the blade member being vibrated in the direction of the arrow with the position of the blade member raised higher than in FIG. 12C and part of the recessed portion of the blade member in FIG. 2 being exposed below the water interface. 12A is a graph showing the relationship between the number (percentage) of bubbles generated by vibrating the blade member and the DLS scattering intensity (diameter). 12B is a graph showing the relationship between the number (percentage) of bubbles generated by vibrating the blade member and the DLS scattering intensity (diameter). 12C is a graph showing the relationship between the number (percentage) of bubbles generated by vibrating the blade member and the DLS scattering intensity (diameter). 12D is a graph showing the relationship between the number (percentage) of bubbles generated by vibrating the blade member and the DLS scattering intensity (diameter). 12D is a graph showing the relationship between the number (percentage) of bubbles generated by vibrating the blade member. ... Graph showing the distribution of zeta potential of bubbles generated when the blade member of FIG. 2 is vibrated in the direction shown in FIG. 3A at a frequency of 170 Hz. Graph showing the distribution of zeta potential of bubbles generated when the blade member of FIG. 2 is vibrated in the direction shown in FIG. 3A at a frequency of 170 Hz. Graph showing the relationship between the number (percentage) of bubbles corresponding to FIG. 16A and DLS scattering intensity (diameter) generated when the blade member of FIG. 2 is vibrated in the direction shown in FIG. 3A at a frequency of 170 Hz. Graph showing the relationship between the number (percentage) of bubbles corresponding to FIG. 16A and DLS scattering intensity (diameter) generated when the blade member of FIG. 2 is vibrated in the direction shown in FIG. 3A at a frequency of 170 Hz. Graph showing the distribution of zeta potential of bubbles generated when the blade member of FIG. 2 is vibrated in the direction shown in FIG. 3A at a frequency of 160 Hz. Graph showing the distribution of zeta potential of bubbles generated when the blade member of FIG. 2 is vibrated in the direction shown in FIG. 3A at a frequency of 160 Hz. 18A and 18B are graphs showing the relationship between the number (percentage) of bubbles corresponding to FIG. 18A and the DLS scattering intensity (diameter) generated when the blade member of FIG. 2 is vibrated in the direction shown in FIG. 3A at a frequency of 160 Hz.A graph showing the relationship between the number (percentage) of bubbles corresponding to FIG. 18A and the DLS scattering intensity (diameter) generated when the blade member of FIG. 2 was vibrated in the direction shown in FIG. 3A at a frequency of 160 Hz. A graph showing the distribution of the zeta potential of bubbles generated when the blade member of FIG. 2 was vibrated in the direction shown in FIG. 3A at a frequency of 4 Hz or less. A graph showing the relationship between the number (percentage) of bubbles and the DLS scattering intensity (diameter) generated when the blade member of FIG. 2 was vibrated in the direction shown in FIG. 3A at a frequency of 4 Hz or less. A conceptual diagram showing the configuration of a blade member (two blades) that is vibrated in a predetermined direction by the bubble generator of FIG. 2. A conceptual diagram showing the configuration of a blade member (four blades) that is vibrated in a predetermined direction by the bubble generator of FIG. 2. A conceptual diagram showing the configuration of a blade member (seven blades) that is vibrated in a predetermined direction by the bubble generator of FIG. 2. A graph showing the generation efficiency of bubbles generated when blade members with different numbers of blades shown in FIGS. 21A, 21B, and FIG. 21C were vibrated in a direction parallel or perpendicular to the direction of the blades. A graph showing the zeta potential of bubbles generated when blade members with different numbers of blades shown in FIGS. 21A, 21B, and FIG. 21C were vibrated in a direction parallel or perpendicular to the direction of the blades. A graph showing the change in the zeta potential of bubbles generated by changing the amount of water in which the blade member of FIG. 2 was immersed. A graph showing the change in the generation efficiency of the bubbles of FIG. 24. A graph showing that bubbles with a positive zeta potential are generated when the blade member of FIG. 2 is vibrated in the direction shown in FIG. 3A. A graph showing the relationship between the number (percentage) of bubbles and the DLS scattering intensity (diameter) of FIG. 26. A schematic diagram showing the interface of ultrapure water contained in a container. A schematic diagram showing the interface of nanobubble water contained in a container. A graph showing the relationship between the number (percentage) of bubbles and the DLS scattering intensity (diameter) of FIG. 26.

[0008] Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters or redundant description of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the applicant provides the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and is not intended to limit the subject matter described in the claims.

[0009] (Embodiment 1) A bubble generator 20 according to an embodiment of the present disclosure will be described below with reference to Figures 1 to 29. (1) Bubbles 10 Produced by the Bubble Generator 20 The bubbles 10 produced by the bubble generator 20 according to this embodiment are primarily nanobubbles having diameters of 1 μm or less (e.g., 10 to 1000 nm), as shown in Figure 1. The bubbles 10 go through the processes of "rising," "contracting," and "collapse" in water, disappearing within a few hours to a few weeks, and producing an effect according to their intended use, such as cleaning, sterilization, or deodorization.

[0010] Bubbles with a diameter of 1 μm or less have superior cleaning power and a longer lifespan than microbubbles with a larger diameter (e.g., 10 μm or less). Furthermore, the bubble water (liquid) containing the bubbles 10 can be, for example, distilled water, ultrapure water, or the like. In addition to distilled water and ultrapure water, other aqueous liquids containing the bubbles 10, including aqueous solutions in which the ionic product of water is established, can also be used.

[0011] The diameter of the bubble 10 is calculated using the following Stokes-Einstein equation: The diffusion coefficient D is determined by analyzing the autocorrelation function.

[0012] (However, D Ｈ: hydrodynamic diameter, D: diffusion coefficient, k: Boltzmann constant, T: temperature (K), η: viscosity) Dynamic light scattering (DLS) is a technique for measuring fine particles contained in suspensions and emulsions with high precision, and is capable of measuring, for example, the particle size, zeta potential, and molecular weight of nanobubbles based on Brownian motion (small particles move quickly and large particles move slowly).

[0013] Dynamic light scattering (DLS) involves irradiating particles undergoing Brownian motion with a laser beam and detecting scattered light signals at a certain angle. The scattered light is analyzed as fluctuations in light intensity or frequency corresponding to the particle diameter, and frequency analysis is performed in the frequency range of 1 Hz to 100 kHz. In addition to dynamic light scattering (DLS), particle trajectory analysis, laser diffraction / scattering, electrical detection zone analysis, resonant mass measurement, dynamic image analysis, and other methods can also be used to measure bubble behavior.

[0014] The zeta potential of the bubble 10 can be measured, for example, by electrophoresis. In electrophoresis, when an electric field is applied to charged particles suspended in an electrolyte, the charged particles move at a constant speed toward an electrode having a polarity opposite to the surface charge. Therefore, the zeta potential of the bubble can be measured by applying the following Henry's equation. The mobility of the charged particles is determined by the Doppler shift.

[0015] (However, U Ｅ : electrophoretic mobility, z: zeta potential, ε: dielectric constant, η: viscosity, F(ka): Henry's constant) (2) Bubble Generator 20 The bubble generator 20 according to this embodiment is, for example, a device that produces electrically charged bubbles contained in water, and mainly generates nanobubbles having a diameter of 1 μm or less (for example, 10 to 1000 nm) in water.

[0016] Specifically, as shown in Fig. 2, the bubble generator 20 includes a blade member 21 that vibrates in a predetermined direction while immersed in water W1 (e.g., distilled water, ultrapure water, etc.) contained in a container C1, a vibration applying unit 22 that vibrates (reciprocates) the blade member 21 in the predetermined direction, and a control unit 23 that controls the vibration applying unit 22. The blade member 21 is formed, for example, from aluminum, and as shown in Fig. 2, is a block-shaped member including a comb-like tip portion and has a plurality of recesses 21a. When vibrations are applied to the blade member 21 near the interface WF of the water W1 in the direction of the arrow (left-right direction in the figure) that is substantially parallel to the interface WF, nanobubbles are generated in the water W1.

[0017] The recesses 21a are parts of the blade member 21 that are used while immersed in water W1, and a plurality of recesses 21a are provided along the interface WF in the posture during use (see FIG. 2). As shown in FIG. 2, vibration is imparted to the blade member 21 mainly when a portion of the recesses 21a is above the interface WF between the water W1 and the air. In other words, when vibration application is initiated, vibration is imparted to the blade member 21 by the vibration imparting unit 22 when a portion of the recesses 21a is above the interface WF.

[0018] As a result, when vibration is applied to the blade member 21 while the tops of the multiple recesses 21a are above the interface WF, the tops of the recesses 21a act as air intakes and vibrate within the water W1, thereby enabling the desired nanobubbles to be generated efficiently. Note that, although three recesses 21a are provided on the blade member 21 in the configuration shown in Fig. 2, the number of recesses 21a may be more than three or may be two or less.

[0019] As shown in Fig. 2, the vibration imparting unit 22 is, for example, a linear motor connected to the blade member 21, and vibrates the blade member 21 at a predetermined frequency (for example, 100 to 300 Hz). As shown in Fig. 2, the vibration imparting unit 22 vibrates the blade member 21 in a direction approximately parallel to the interface WF while a portion of the blade member 21 is immersed in water W1. As shown in Fig. 2, the control unit 23 is connected to the vibration imparting unit 22, and controls the vibration imparting unit 22 to vibrate the blade member 21 at the predetermined frequency (for example, 100 to 300 Hz).

[0020] Here, the direction in which the blade member 21 is vibrated by the vibration applying unit 22 can be considered to be a direction that is substantially parallel to the interface WF and substantially perpendicular to the recess 21 a, as shown in Fig. 3A, or a direction that is substantially parallel to the interface WF and substantially parallel to the recess 21 a, as shown in Fig. 3B. For example, when the blade member 21 is vibrated in the direction shown in Fig. 3A, the upper part of the recess 21 a serves as an air intake near the interface WF of the water W1, thereby stirring the water W1 and efficiently generating bubbles in the water W1.

[0021] On the other hand, if the blade member 21 is completely immersed in water (see FIG. 12A), no air intake port is formed in the recess 21a, and the efficiency of nanobubble generation drops dramatically. Therefore, if the height position of the blade member 21 relative to the interface WF of the water W1 is such that the entire blade member 21 is immersed, there is a risk that almost no nanobubbles will be generated.

[0022] At this time, the generated bubbles 10 have a negative zeta potential of -26.97 mV, which is the average of the results of three experiments, as shown in Figure 4. In the graph shown in Figure 4, the horizontal axis represents the elapsed time (s) after a voltage was applied to the electrode unit, and the vertical axis represents the mobility (phase (rad)) of the bubbles 10 moving by electrophoresis in the bubble water. The graph shown in Figure 4 also shows data from three consecutive measurements of the behavior of the bubbles 10.

[0023] The same applies to the graphs shown in Figures 6, 8A and 8B, and 10A and 10B described below. Figure 5 shows data on backscattering (bubble diameter and number (%)) immediately after bubbles 10 are generated by vibrating the blade member 21 in the direction shown in Figure 3A. Therefore, it can be seen that the bubbles 10 having a negative zeta potential shown in Figure 4 have a number concentration of 10 to the power of 9 per cc and a diameter of approximately 50 to 200 nm, as shown in Figure 5.

[0024] The three lines in the graph of Fig. 5 represent the results of three consecutive measurements. The horizontal axis of the graph in Fig. 5 represents the diameter of the observed particles (bubbles), and the vertical axis represents the number (%) of bubbles. The same applies to the graphs shown in Figs. 7, 9A and 9B, 11A and 11B, 13A and 13B, and 14A and 14B, which will be described below.

[0025] Next, for example, when the blade member 21 is vibrated in the direction shown in Figure 3B, bubbles are generated in the water W1 near the interface WF of the water W1. At this time, the generated bubbles 10 have a negative zeta potential of -15.93 mV, the average of the results of three experiments, as shown in Figure 6. Figure 7 shows data on backscattering (bubble diameter and number (%)) immediately after the bubbles 10 are generated by vibrating the blade member 21 in the direction shown in Figure 3B.

[0026] Therefore, it can be seen that the bubbles 10 having a negative zeta potential shown in Fig. 6 have a diameter of about 20 to 100 nm, which is about half the diameter of the result shown in Fig. 5, as shown in Fig. 7. That is, whether the direction in which the blade member 21 is vibrated is substantially perpendicular to the recess 21a shown in Fig. 3A or parallel to the recess 21a shown in Fig. 3B, the generation of bubbles 10 of about 50 to 200 nm and about 20 to 100 nm was confirmed in both cases, although there was a difference in number concentration.

[0027] Next, the results of an experiment in which 10 ml of ultrapure water was placed in the container C1 shown in Fig. 2 and the blade member 21 was vibrated for 30 seconds at a frequency of 240 Hz in the direction shown in Fig. 3A will be described with reference to Figs. 8A, 8B, 9A, and 9B. That is, when the blade member 21 was vibrated for 30 seconds at a frequency of 240 Hz in the direction shown in Fig. 3A (a direction substantially perpendicular to the recess 21a), the generation of bubbles 10 with average negative zeta potentials of -26.60 mV and -28.70 mV was confirmed, as shown in Figs. 8A and 8B.

[0028] At this time, it can be seen that the diameter of the generated bubbles 10 is in the range of 30 to 400 nm, as shown in Figures 9A and 9B. Here, bubble water containing many generated bubbles 10 with diameters of 30 to 40 nm may exhibit higher viscosity, as shown in Figure 28B, compared to the ultrapure water shown in Figure 28A, based on changes in the interface WF.

[0029] Next, to confirm the frequency dependency of the generation of bubbles 10, 10 ml of ultrapure water was placed in container C1 shown in Fig. 2, and the blade member 21 was vibrated for 30 seconds at a frequency of 207 Hz in the direction shown in Fig. 3A. The results of the experiment will be described with reference to Figs. 10A, 10B, 11A, and 11B. That is, when the blade member 21 was vibrated for 30 seconds at a frequency of 207 Hz in the direction shown in Fig. 3A (a direction substantially perpendicular to the recess 21a), the generation of bubbles 10 with average negative zeta potentials of -22.43 mV and -20.43 mV was confirmed, as shown in Figs. 10A and 10B.

[0030] 11A and 11B, it can be seen that the diameter of the bubbles 10 generated is in the range of 30 to 400 nm. From the above, it has been found that when a small amount (for example, 10 ml) of water W1 is placed in the container C1 and vibrations at a frequency of about 207 to 240 Hz are applied to the blade member 21 in a direction approximately perpendicular to the recess 21 a, bubbles 10 with diameters of about 30 to 400 nm are generated in both cases.

[0031] Furthermore, the DLS scattering intensity was approximately 800 on average under conditions of a frequency of 240 Hz and approximately 320 on average under conditions of a frequency of 204 Hz. Therefore, it was found that a higher frequency, under the same water volume and generation time conditions, resulted in a higher zeta potential and an advantageous DLS scattering intensity (number concentration). Next, the experimental results obtained when the blade member 21 was vibrated in the direction shown in FIG. 3A for 30 seconds in 3 ml of water at frequencies of 160 Hz and 170 Hz will be described with reference to FIGS. 16A to 19B.

[0032] That is, when the blade member 21 was vibrated for 30 seconds at a frequency of 170 Hz in the direction shown in Fig. 3A (a direction substantially perpendicular to the recess 21a), the generation of bubbles 10 with average negative zeta potentials of -15.93 mV and -15.33 mV was confirmed, as shown in Fig. 16A and Fig. 16B. At this time, it was found that the diameters of the generated bubbles 10 were in the range of 25 to 300 nm, as shown in Fig. 17A and Fig. 17B.

[0033] Furthermore, when the blade member 21 was vibrated for 30 seconds at a frequency of 160 Hz in the direction shown in Fig. 3A (a direction substantially perpendicular to the recess 21a), the generation of bubbles 10 with average negative zeta potentials of -6.49 mV and -9.32 mV was confirmed, as shown in Fig. 18A and Fig. 18B. The diameters of the generated bubbles 10 were found to be in the range of 45 to 300 nm, as shown in Fig. 19A and Fig. 19B.

[0034] On the other hand, the experimental results when the frequency was decreased are as follows, using Figures 20A and 20B. That is, when the amount of water in which blade member 21 was immersed was 120 ml and vibration was performed in the direction shown in Figure 3A (a direction substantially perpendicular to recess 21a) at a frequency of approximately 4.1 Hz for one minute, the generation of bubbles 10 having a zeta potential of -0.43 mV was confirmed on average over three experiments, as shown in Figure 20A. However, when the size of the generated bubbles 10 was examined, almost no microbubbles or nanobubbles were generated, as shown in Figure 20B.

[0035] From the above results, it was found that results were almost the same as when the blade member 21 was vibrated at 207 Hz and 240 Hz as described above, and therefore that the frequency condition for the generation of nano-sized bubbles 10 is in the range of 4 to 300 Hz, preferably 160 to 240 Hz. Next, the relationship between the height position of the blade member 21 with respect to the interface WF and the generation of bubbles 10 when vibration is applied to the blade member 21 will be described using Figures 12A, 12B, 12C and 12D, 13A and 13B, and 14A and 14B.

[0036] In the experiment, the blade member 21 was immersed in the following states: until the entire recess 21a was below the interface WF of the water W1 (20 ml) (Figure 12A); until the upper end of the recess 21a was near the interface WF (Figure 12B); until the top of the recess 21a was above the interface WF (Figure 12C); and until only a portion of the recess 21a was below the interface WF (Figure 12D).The blade member 21 was vibrated at a predetermined frequency (216 Hz) for 30 seconds along the direction shown in Figure 3A.

[0037] At the immersion depth of the blade member 21 shown in Fig. 12A, the average of the results of three experiments was a zeta potential of -14.77 mV and a DLS scattering intensity of 64.03, and bubbles 10 having diameters of 35 to 300 nm were generated at a concentration of 25 to 35%, as shown in Fig. 13A. At the immersion depth of the blade member 21 shown in Fig. 12B, the average of the results of three experiments was a zeta potential of -17.78 mV and a DLS scattering intensity of 52.20, and bubbles 10 having diameters of 50 to 300 nm were generated at a concentration of 25 to 30%, as shown in Fig. 13B.

[0038] At the immersion depth of the blade member 21 shown in Fig. 12C, the average of the results of three experiments was a zeta potential of -14.41 mV and a DLS scattering intensity of 66.70, and bubbles 10 having diameters of 60 to 350 nm were generated at a concentration of 20 to 35%, as shown in Fig. 14A. At the immersion depth of the blade member 21 shown in Fig. 12D, the average of the results of three experiments was a zeta potential of -16.87 mV and a DLS scattering intensity of 59.07, and bubbles 10 having diameters of 50 to 400 nm were generated at a concentration of around 30%, as shown in Fig. 14B.

[0039] As described above, nanobubbles of about 50 to 300 nm were generated in all cases, and it is clear that the diameter of the generated bubbles can be adjusted to some extent by changing the position of the recess 21a of the blade member 21 relative to the interface WF. Therefore, by changing the immersion position of the blade member 21 at the interface WF relative to the immersion direction into the water W1, it is possible to control the generation ratio of nanobubbles and microbubbles of different diameters.

[0040] Furthermore, when the blade member 21 is vibrated while being completely immersed in the water W1, the average DLS scattering intensity is smaller than the lower detection limit of 30, as shown in Fig. 29, and it is therefore clear that almost no nanobubbles are generated. In other words, in the bubble generator 20 of this embodiment, it is important not to immerse the entire blade member 21 in the interface of the water W1, and it is preferable that at least a part of the blade member 21 is positioned above the interface of the water W1.

[0041] <Bubble Generation Method> The bubble generator 20 of this embodiment generates nanobubbles according to the flowchart shown in Fig. 15. That is, in step S11, the blade member 21 is set so that a part of the blade member 21 (the recess 21a) is immersed in the interface WF of the water W1 (setting step).

[0042] Next, in step S12, the control unit 23 applies vibrations from the vibration applying unit 22 such as a linear motor to the blade member 21 at a predetermined frequency in a direction substantially parallel to the interface WF of the water W1 from the state of step S11 (control step). Next, in step S13, bubbles 10 having a diameter of about 100 nm are generated in the water W1.

[0043] As described above, in the bubble generation method of this embodiment, desired nanobubbles can be generated efficiently and stably by vibrating the blade member 21 at a predetermined frequency substantially parallel to the interface WF with a portion of the blade member 21 immersed below the interface WF. <Main Features> The bubble generator 20 of this embodiment is a device for generating nanobubbles in water, and includes the blade member 21 that is used with at least a portion immersed in the interface WF of the water W1, a vibration imparting unit 22 that vibrates the blade member 21 in a direction substantially parallel to the interface WF of the water W1, and a control unit 23 that controls the vibration imparting unit 22 to vibrate the blade member 21 at the predetermined frequency.

[0044] As a result, by vibrating the blade member 21 at a predetermined frequency while at least a portion of the blade member 21 is immersed below the interface of the water W1, it is possible to efficiently generate nanobubbles having a diameter of, for example, about 100 nm in a small amount of water W1. As a result, it is possible to efficiently and stably generate nanobubbles, or to change the size of the nanobubbles that are generated.

[0045] Moreover, for example, various gases can be trapped in nanobubbles and sorted according to their size. Furthermore, by miniaturizing nanobubbles, higher number density and viscosity can be achieved, further expanding the industrial applications of nanobubbles, including cleaning. Here, the results of verifying the bubble generation method when the number of blades in the blade member 21 is changed are described below with reference to Figures 21A to 23.

[0046] That is, Figures 22 and 23 show experimental data obtained by using a blade member 121a with two blades as shown in Figure 21A, a blade member 121b with four blades as shown in Figure 21B, and a blade member 121c with seven blades as shown in Figure 21C, and vibrating blade members 121a, 121b, and 121c in a direction perpendicular (●) or parallel (▲) to the blade direction.

[0047] The derived count rate on the vertical axis of the graph shown in Figure 22 is the number of photon pulses per second detected by the light-receiving optical system using the photon correlation method, and is proportional to the detected scattered light intensity, expressed in units of cps (counts per second). As a result, when the blade members 121a, 121b, and 121c are vibrated in the direction perpendicular (●) to the blade orientation (the direction shown in Figure 3A), as shown in Figure 22, it can be seen that the variation in the generated bubbles 10 is suppressed by increasing the number of blades to two, four, and seven.

[0048] Furthermore, as shown in Fig. 23, it can be seen that changing the number of blades has almost no effect on the zeta potential of the generated bubbles 10. On the other hand, when the blade members 121a, 121b, and 121c are vibrated in a direction (▲) parallel to the blade orientation (the direction in Fig. 3B), as shown in Fig. 22, it can be seen that the number concentration of the generated bubbles 10 increases as the number of blades increases from two to four to seven.

[0049] 23, it can be seen that the absolute value of the zeta potential of the generated bubbles 10 increases as the number of blades increases from 2 to 4 to 7. Next, the results of verifying the generation of bubbles 10 when the amount of water in which the blade member 21 is immersed is changed will be explained below with reference to FIGS.

[0050] That is, as shown in Fig. 24, when the amount of water is changed to 3 ml, 10 ml, and 20 ml, the zeta potential of the generated bubbles 10 is found to be most stable when the amount of water is the smallest, 3 ml. Also, as shown in Fig. 25, the concentration of the generated bubbles 10 is the largest when the amount of water is the smallest, 3 ml, and is 10 ９ It can be seen that bubbles 10 are generated at a high concentration of bubbles per cc.

[0051] In the bubble generating device 20 and bubble generating method of the present embodiment, radicals (O ２ － It has also been found that nanobubble water containing hydroxyl groups such as hydroxyl groups, hydroxypropyl ...

[0052] (A) In the above embodiment, an example was described in which bubbles 10 were generated using a blade member 21 having a plurality of recesses 21 a. However, the present disclosure is not limited to this. For example, bubbles may be generated by vibrating a plate-shaped blade member that does not have recesses along the interface.

[0053] In addition, the number of recesses is not limited to multiple, and may be one. (B) In the above embodiment, an example was described in which bubbles were generated by vibrating the blade member 21 approximately parallel to the interface WF in directions approximately perpendicular and parallel to the recesses 21 a. However, the present disclosure is not limited to this.

[0054] For example, bubbles may be generated by vibrating the blade member in a direction oblique to the recess. (C) In the above embodiment, an example was given in which bubbles with a negative zeta potential were generated. However, the present invention is not limited to this.

[0055] For example, a configuration may be used in which bubbles with a positive zeta potential are generated. For example, bubbles 10 generated when a blade member 21 having four blades is vibrated in the direction shown in Figure 3A have a positive zeta potential immediately after the start of vibration, as shown in Figure 26. Furthermore, the size of the bubbles 10 is found to be concentrated in the range of 100 to 300 nm, as shown in Figure 27.

[0056] The generation of bubbles 10 with such a positive zeta potential may be due to, for example, using an aluminum blade member 21 without cleaning it. (D) In ​​the above embodiment, an example was described in which bubbles 10 were generated in water W1 using a single blade member 21 having multiple recesses 21a that was used while immersed in water W1. However, the present disclosure is not limited to this.

[0057] For example, the blade member used while immersed in water may be multiple, rather than just one. (E) In the above embodiment, aluminum is used as an example of the material for the blade member 21. However, the present disclosure is not limited to this.

[0058] For example, a configuration including a blade member molded using a resin-based material may be used. (F) In the above embodiment, an example was described in which the amount of water W1 in which the blade member 21 is immersed is 3 ml to 30 ml. However, the present disclosure is not limited to this. For example, the amount of water in which the blade member is immersed to generate nanobubbles is important, depending on the positional relationship between the water interface and the blade member, and is not limited to the total amount of water, and may be less or more than the above amount.

[0059] However, to obtain nanobubble water with a high number concentration, it is desirable to generate nanobubbles using a small amount of water (see the results in Figures 24 and 25 above). <Notes> The above description of the embodiments discloses the following technology. (Technology 1) A bubble generator according to technology 1 is a bubble generator that generates nanobubbles in water, and includes: a blade member that is used with at least a portion of it immersed in the water interface; a vibration imparting unit that vibrates the blade member in a direction approximately parallel to the water interface; and a control unit that controls the vibration imparting unit to vibrate the blade member at a predetermined frequency.

[0060] (Technology 2) The bubble generator according to Technology 2 is the bubble generator according to Technology 1, wherein the blade member is vibrated by the vibration imparting unit near the interface of the water. (Technology 3) The bubble generator according to Technology 3 is the bubble generator according to Technology 1 or 2, wherein the blade member has a recess formed along a direction intersecting the interface.

[0061] (Technology 4) A bubble generator according to Technology 4 is the bubble generator according to Technology 3, wherein when the application of vibration is started, vibration is applied to the blade member by the vibration applying unit in a state where a part of the recess is above the interface. (Technology 5) A bubble generator according to Technology 5 is the bubble generator according to Technology 3, wherein the blade member has a plurality of the recesses along the interface.

[0062] (Technology 6) A bubble generator according to Technology 6 is the bubble generator according to any one of Technology 1 to Technology 5, in which the immersion position of the interface of the blade member relative to the immersion direction in the water is changed to control the generation ratio of the nanobubbles and the microbubbles.

[0063] (Technology 7) The bubble generator according to Technology 7 is the bubble generator according to any one of Technology 1 to Technology 6, wherein a plurality of the blade members are provided. (Technology 8) The bubble generator according to Technology 8 is the bubble generator according to any one of Technology 1 to Technology 7, wherein the vibration applying unit is a linear motor.

[0064] The bubble generator of the present disclosure can generate nanobubbles efficiently and stably, or has the effect of changing the size of the generated nanobubbles, and is therefore widely applicable to devices that generate nanobubbles in water.

[0065] REFERENCE SIGNS LIST 10 Bubble 20 Bubble generator 21 Blade member 21a Recess 22 Vibration applying unit 23 Control unit C1 Container W1 Water (nanobubble water) WF Interface

Claims

1. A bubble generator that generates nanobubbles in water, comprising: a blade member that is used with at least a portion immersed in the water interface; a vibration imparting unit that vibrates the blade member in a direction approximately parallel to the water interface; and a control unit that controls the vibration imparting unit to vibrate the blade member at a predetermined frequency.

2. The bubble generator according to claim 1, wherein the blade member is vibrated by the vibration imparting unit near the interface of the water.

3. A bubble generator according to claim 1 or 2, wherein the blade member has a recess formed along a direction intersecting the interface.

4. The bubble generator according to claim 3, wherein the blade member is vibrated by the vibration imparting unit in a state where a portion of the recess is above the interface when the application of vibration begins.

5. The bubble generating device according to claim 3, wherein the blade member has a plurality of the recesses along the interface.

6. A bubble generator according to claim 1 or 2, wherein the immersion position of the interface of the blade member relative to the immersion direction in the water is changed to control the generation ratio of nanobubbles and microbubbles.

7. A bubble generator according to claim 1 or 2, wherein a plurality of the blade members are provided.

8. The bubble generator according to claim 1 or 2, wherein the vibration applying unit is a linear motor.

9. A bubble generating method for generating nanobubbles in water, comprising: a setting step of setting a blade member with at least a portion thereof immersed in the water interface; and a control step of controlling a vibration imparting unit to vibrate the blade member at a predetermined frequency in a direction approximately parallel to the water interface.

10. The bubble generation method according to claim 9, wherein the blade member has a plurality of blades, and in the setting step, the blade members with different numbers of blades are set, and in the control step, the blade members with different numbers of blades are vibrated at a predetermined frequency to change the concentration of nanobubbles generated.

11. The bubble generating method according to claim 9, wherein the concentration of nanobubbles generated is changed by changing the amount of water in which at least a portion of the blade member is immersed in the setting step.

12. The bubble generating method according to claim 9, wherein in the setting step, the direction in which the blade member is vibrated is changed to change the size of the nanobubbles.

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