Generation of nanobubbles in a liquid carrier

Abstract

Apparatus and methods for producing a composition comprising nanobubbles dispersed in a liquid carrier are described. One such method includes flowing a liquid carrier from an inlet through at least two channels, each containing a triboelectric material, such that the Reynolds number for the flow of the liquid carrier through the at least two channels is less than 3000. Flowing the liquid carrier through the at least two channels generates vibrational energy that (i) contacts the liquid carrier with the triboelectric material such that an electric charge is generated within the triboelectric material, and (ii) separates the liquid carrier from the triboelectric material such that an electric charge is discharged to the liquid carrier to form nanobubbles dispersed in the liquid carrier. TIFF2026504969000002.tif128153

Description

[Technical Field]

[0001] Priority claims This application claims priority to U.S. Patent Application No. 63 / 441,595, filed January 27, 2023, the entire contents of which are incorporated herein by reference.

[0002] Technical Field The present invention relates to an apparatus and method for producing a composition containing a liquid carrier and nanobubbles dispersed therein. [Background technology]

[0003] background Nanobubbles have several unique properties, including a long lifetime in liquids due to their negatively charged surfaces. Nanobubbles also have high gas solubility in liquids due to their high internal pressure. Conversely, microbubbles and macrobubbles are larger in size and therefore rise quickly and burst at the surface.

[0004] Nanobubbles have applications in a variety of fields and may have numerous beneficial effects from medical, industrial, and agricultural perspectives: for example, the presence of nanobubbles may promote physiological activity and increase metabolism in living organisms, resulting in enhanced ontogenetic growth.

[0005] To date, several methods have been proposed to produce nanobubbles. These methods include vortex-type liquid flow, venturi, high-pressure melting, ejector, direct-contact condensation of mixed vapors, and ultrasonic vibration. All of these methods are energy intensive and have had varying degrees of success in creating nanobubbles. Summary of the Invention

[0006] overview The inventors have discovered that high concentrations of nanobubbles can be surprisingly produced using an apparatus with a specific design and under specific processing parameters. Without being bound by theory, it is believed that the apparatus described herein, which has a conduit of a specific geometric shape and is composed of at least one triboelectric material, is designed to generate vibrational energy that causes contact between a flowing liquid carrier and the triboelectric material and separation of the flowing liquid carrier from the triboelectric material. Contact between the liquid carrier and the triboelectric material generates a charge within the triboelectric material, and separation discharges the charge into a volume of the liquid carrier. This process, called liquid-solid contact electrification, results in the formation of nanobubbles dispersed in the liquid carrier. Because the vibrational energy provided by the flowing liquid carrier generates nanobubbles in the liquid carrier (e.g., based on a liquid-solid contact electrification process), the apparatus and methods using the apparatus are advantageous in that they do not require the introduction of an external gas or the addition of an external energy source to generate nanobubbles. Furthermore, because the devices and methods described herein are capable of generating nanobubbles without an external gas or energy source, the device may be a miniaturized device, such as a microfluidic device.

[0007] The methods and devices described herein are capable of producing high concentrations of nanobubbles. In some embodiments, the device comprises a 1 cm 3 At least 10 per 6 Nanobubbles can be produced at a concentration of 1 cm. In some embodiments, the nanobubble concentration is 1 cm. 3 At least 10 per 7 pieces, 1 cm 3 At least 10 per 8 pieces, 1 cm 3 At least 10 per 9 pieces, 1 cm 3 At least 10 per 10 pieces or 1 cm 3 At least 10 per 11In some embodiments, the composition contains nanobubbles that are stable in a liquid carrier at ambient pressure and temperature for at least 1 month or at least 3 months.

[0008] The nanobubble concentration is 1 cm 3 Nanobubble concentration is expressed as the number of nanobubbles per 1000 µm sample. Nanobubble concentration is measured by collecting three samples from the electrolytic cell (which receives the effluent of the nanobubble generator) and analyzing each sample within 20 minutes of acquisition by Nanoparticle Tracking Analysis using a Nanosight NS3000 analyzer available from Malvern PANalytical. Each sample is filtered using a 0.45 µm filter before being analyzed using the Nanosight NS3000 analyzer.

[0009] In a first aspect, a method for producing a composition comprising nanobubbles dispersed in a liquid carrier is described. The method includes flowing the liquid carrier from an inlet through at least two channels, each containing a triboelectric material, such that the Reynolds number for the flow of the liquid carrier through the at least two channels is less than 3000, e.g., less than 2500. Flowing the liquid carrier through the at least two channels under this flow condition generates vibrational energy that brings the liquid carrier into contact with the triboelectric material such that an electric charge is generated within the triboelectric material. The generated vibrational energy also separates the liquid carrier from the triboelectric material such that an electric charge is discharged to the liquid carrier to form nanobubbles dispersed in the liquid carrier.

[0010] The liquid carrier may flow from the at least two channels to an outlet where the liquid carrier, now having nanobubbles dispersed therein, may be collected.

[0011] The step of flowing the liquid carrier through the at least two channels comprises flowing the liquid carrier through at least 3.79×10 -5 m 3 / min, or at least 3.79 x 10 -3 m 3 For example, the liquid carrier may be flowed at a flow rate of 3.79×10 / min. -5 m 3 / min~3.79 m 3 / min, 3.79×10 -3 m 3 / min~1.89 m 3 / min, 7.57×10 -3 m 2 / min~9.46×10 -1 m 3 / min, or 1.89 x 10 -1 m 3 / min~5.68×10 -1 m 3 1 / min through the at least two channels.

[0012] The method may include controlling the flow rate of the liquid carrier through the at least two channels, for example, using a flow controller disposed between the inlet and the channel. Controlling the flow rate may include, for example, pulsing the flow of the liquid carrier through the at least two channels.

[0013] Although the methods described herein do not require the use of an external power source to generate nanobubbles, the methods may involve generating a charge in the triboelectric material using an external power source. For example, the methods may include applying a vibration to the triboelectric material using a resonator or injecting a charge into the triboelectric material from a current source.

[0014] These methods produce flow conditions sufficient to promote solid-liquid contact electrification, for example, flow conditions of a liquid carrier through a channel sufficient to generate at least 90 J of vibrational energy.

[0015] In some embodiments, to achieve a Reynolds number of less than 3000, the liquid carrier is dispersed at a rate of at least 3.79×10 in channels having a geometry such that the ratio of the average channel circumference to the average flow path length of the channels is at least about 0.015. -5 m 3 It flows at a flow rate of / min.

[0016] In a second aspect, combinable with the first aspect, an apparatus for generating a composition containing nanobubbles dispersed in a liquid carrier is described, the apparatus including an inlet for receiving the liquid carrier from a liquid source, an outlet for dispensing the liquid carrier with the nanobubbles dispersed therein, and a housing for producing the nanobubbles.

[0017] The housing has (a) first and second ends fluidly connected to an inlet and an outlet, respectively; (b) at least two channels for receiving a liquid carrier from the inlet, wherein the ratio of an average perimeter of the channels to an average flow path length of the channels is at least 0.015; and (c) a flow rate of at least 15 microcoulombs per square meter (μC / m 2 and at least one triboelectric material having an absolute value of charge density of

[0018] The device is configured to generate vibrational energy while flowing a liquid carrier through its internal cavity without the use of an external power source or external gas. The geometry of the device is such that the liquid carrier is at least 3.79×10 -5 m 3The device is designed so that when flowing therethrough at a flow rate of 1 / min, the flow of the liquid carrier produces vibrations that cause the liquid carrier to contact and subsequently separate from the triboelectric material. When the flowing liquid carrier comes into contact with the triboelectric material, a charge is produced within the triboelectric material, which may further accumulate within the triboelectric material during contact. The vibrations produced by the flow of the liquid carrier also cause the flowing liquid carrier to separate from the triboelectric material so that the accumulated charge is discharged into the liquid carrier. The device described herein does not require the introduction of pressurized gas, as nanobubbles are formed and dispersed in the liquid carrier as a result of the release of charge from the triboelectric material into the liquid carrier. Rather, the vibrations and transferred charge interact with gas already dissolved in the liquid carrier to produce nanobubbles in the liquid carrier.

[0019] The triboelectric material has inherent properties to facilitate solid-liquid contact charging, such as an absolute value of charge density of at least 15 μC / m. In some embodiments, the triboelectric material has a charge density of at least 50 μC / m. 2 , at least 200 μC / m 2 , at least 500 μC / m 2 , at least 700 μC / m 2 , or at least 800 μC / m 2 The triboelectric material may have an absolute value of charge density of about 15 μC / m 2 ~Approx. 1,200 μC / m 2 , about 50 μC / m 2 ~Approx. 1,000 μC / m 2 , about 200 μC / m 2 ~about 950 μC / m 2 , or approximately 700 μC / m 2 ~about 900 μC / m 2 The triboelectric material may have a negative charge density or a positive charge density.

[0020] The triboelectric material may comprise a polymer. For example, the triboelectric material is PTFE. In some embodiments, the triboelectric material may comprise polytetrafluoroethylene (PTFE), polyethylene, polyvinyl chloride (PVC), polyethylene terephthalate glycol (PETG), acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), polyamide (PA), ethylene tetrafluoroethylene (ETFE), polymethyl methacrylate (PMMA), or a combination thereof.

[0021] The devices described herein contain features configured to contact a liquid carrier that are at least partially made of triboelectric material. For example, the device may include a channel defined by a wall at least a portion of which contains triboelectric material.

[0022] The channels of the device have dimensions designed to facilitate liquid-solid contact charging, e.g., the ratio of the average channel circumference to the average channel flow path length is in the range of about 0.015 to about 150, e.g., about 0.015 to about 30, or about 0.025 to about 15.

[0023] In some cases, at least a portion of the triboelectric material has a surface texture designed to facilitate liquid-solid contact electrification. For example, the triboelectric material has a surface texture designed to facilitate liquid-solid contact electrification. -8 meters ~ 1 × 10 -2 The standard deviation of the surface height distribution in meters (RMS or Rq) is approximately 0.5 × 10 -8 meters ~ 1 × 10 -2 The surface texture may be characterized by the average spacing (Si) of the contour peaks in meters.

[0024] The housing of the device contains multiple channels. The inlet and / or housing of the device may distribute the liquid carrier into at least two flow paths, where each flow path flows into a separate channel. Each channel may be in the form of a single-channel tubing or a channel of a multi-channel tubing. The housing defines at least two channels, but may define more than two channels, e.g., at least 10 channels, at least 25 channels, or at least 100 channels. The housing may define from about 2 channels to about 20 channels, from about 5 channels to about 50 channels, or from about 50 channels to about 1,000 channels.

[0025] Although the devices described herein do not require the use of an external power source to generate nanobubbles, in some embodiments, the device may include an external power source to increase the generation of charge within the triboelectric material. The external power source may apply electrical or vibrational energy to the device to increase the generation of charge within the triboelectric material. The external power source may be a resonator (e.g., an electromagnetic or mechanical resonator), a battery, or both.

[0026] The devices described herein may include a flow controller, such as a valve, configured to control the flow of the liquid carrier through the channels of the device. The flow controller may also include a processor or controller that controls the valve. For example, the flow controller may control the flow of the liquid carrier to produce a flow that promotes liquid-solid contact charging.

[0027] As used herein, the term "nanobubbles" refers to bubbles having a diameter of less than 1 micron. Larger than nanobubbles, microbubbles are bubbles having a diameter greater than or equal to 1 micron and less than 50 microns. Macrobubbles are bubbles having a diameter greater than or equal to 50 microns.

[0028] In a third aspect, combinable with the first or second aspect, a method is described for producing a composition containing nanobubbles dispersed in a liquid carrier using the above-described apparatus, the method including introducing the liquid carrier from a liquid source into the inlet and receiving the liquid carrier from the inlet into the at least two channels of the housing.

[0029] In an exemplary method in which a liquid carrier flows through a device of the invention, vibrational energy is generated that (i) contacts the liquid carrier with the triboelectric material such that a charge is produced within the triboelectric material, and (ii) separates the liquid carrier from the triboelectric material such that a charge is discharged into the liquid carrier to form nanobubbles dispersed in the liquid carrier. In some embodiments, the device generates vibrational energy that is at least 6×10 -7 m 3 at least 1 x 10 in a device with a volume of -6 cubic metres per minute (m 3 The vibrational energy generating device is configured to generate a minimum of about 90 Joules (J) of vibrational energy when the liquid carrier is flowing at a flow rate of 100 rpm (1 / min).

[0030] The above-described compositions having nanobubbles dispersed in a liquid carrier are useful in a number of applications. For example, the compositions can be used to treat water by transporting them to the water in need of treatment. Examples of water sources that can be treated include wastewater, oxygen-depleted water, drinking water, and water for aquaculture.

[0031] In another application, the compositions described above may be combined with a liquid to create a pumpable composition having a viscosity lower than that of the liquid, and the pumpable composition may be transported through a pipe to a desired destination. Examples of liquids include crude oil and drilling or hydraulic fracturing fluids.

[0032] In another application, the above-described compositions may be combined with a liquid to create an oxygen-rich composition that is then applied to the roots of plants to enhance plant growth.

[0033] In another application, the compositions described above may be applied in a medical procedure or introduced into a patient using a medical device.

[0034] In another application, the compositions described above may be used to inhibit the development of scale in a system, such as by circulating the composition in a cooling tower.

[0035] In another application, the compositions described above may be used in electrolysis, for example, the compositions may be used as or in conjunction with an electrolyte.

[0036] The details of one or more embodiments of the invention are set forth in the description that follows. Other features, objects, and advantages of the invention will become apparent from the description and from the claims. [Brief explanation of the drawings]

[0037] [Figure 1] 1-4, 5A-5B, and 6A-6B are diagrams of exemplary apparatus for producing compositions containing nanobubbles dispersed in a liquid carrier. [Figure 2] See legend to Figure 1. [Figure 3] See legend to Figure 1. [Figure 4] See legend to Figure 1. [Figure 5A] See legend to Figure 1. [Figure 5B] See legend to Figure 1. [Figure 6] See legend to Figure 1. [Figure 7] 1 illustrates an exemplary surface texture plot. [Figure 8] 1 is a flowchart. DETAILED DESCRIPTION OF THE INVENTION

[0038] Detailed Description Described herein are methods and devices for generating compositions containing nanobubbles dispersed in a liquid carrier under specified flow conditions. Because vibrational energy generated by the flow of the liquid carrier through the device results in the generation of nanobubbles in the liquid carrier (e.g., based on the aforementioned liquid-solid contact charging process), the device and methods using the device do not require the introduction of an external gas or the addition of an external energy source when generating nanobubbles. Furthermore, because the device and method described herein can generate nanobubbles without an external gas or energy source, the device can be a miniaturized device, such as a microfluidic device.

[0039] 1, an apparatus 100 for generating a composition containing nanobubbles dispersed in a liquid carrier includes an inlet 102 disposed at a first end of a housing 106 and an outlet 104 disposed at an opposite end of the housing 106. In the illustrated example, two flow channels 110a, 110b are defined within the housing 106, although other numbers of channels may also be used.

[0040] Channels 110a, 110b are fluidly coupled to inlet 102 and positioned to receive the liquid carrier from inlet 102. As the liquid carrier enters housing 106 from inlet 102, it is divided into two flow paths within distribution chamber 105 (e.g., as indicated by the arrows in FIG. 1 ); each flow path corresponds to a respective one of channels 110a, 110b. The liquid carrier flows through channels 110a, 110b with flow characteristics (e.g., velocity, pressure) based on the flow pattern of the liquid carrier through distribution chamber 105. For example, the presence of distribution chamber 105 between inlet 102 and channels 110a, 110b distributes the liquid carrier substantially evenly between channels 110a, 110b, e.g., such that the fluid pressure and flow rate of the liquid carrier are substantially consistent throughout channels 110a, 110b.

[0041] The liquid carriers exiting channels 110a, 110b are recombined in effluent chamber 107 and exit housing 106 through outlet 104. As described below, the liquid carrier exiting through outlet 104 contains a high concentration of nanobubbles.

[0042] In the illustrated example, each channel 110a, 110b is a flow path through a respective single-channel tube 112a, 112b disposed within the housing 106. In some embodiments, a single multi-channel tube is disposed within the housing 106, and two channels 110a, 110b are flow paths through each channel of the multi-channel tube. In some embodiments, the channels 110a, 110b are defined by holes extending through the thickness of a solid block of material. Other configurations for the channels 110a, 110b are also possible.

[0043] Referring also to the cross-sectional inset in FIG. 1 , the inner walls 114 of channels 110a, 110b contain a triboelectric material. A triboelectric material is, for example, a material that can become electrically charged when in contact with another material. In the example of FIG. 1 , tubes 112a, 112b themselves are composed of a triboelectric material, e.g., inner walls 114 of channels 110a, 110b are the inner walls of tubes 112a, 112b. In some embodiments, the triboelectric material is a coating disposed on the inner walls of tubes 112a, 112b, e.g., a continuous layer of triboelectric material, discontinuous regions of triboelectric material, or another suitable arrangement. All or a portion of inner walls 114 of channels 110a, 110b may include the triboelectric material. Other configurations are also possible, e.g., as described below.

[0044] The flow of the liquid carrier through the channels 110a, 110b from the inlet 102 to the outlet 104 of the housing generates vibrational energy that causes the liquid carrier to contact the inner walls 114 of the channels 110a, 110b, thereby contacting the triboelectric material, and to separate from the inner walls 114 of the channels 110a, 110b. This contact and separation causes the generation and accumulation of charge in the triboelectric material and the transfer of that charge to the liquid carrier, thereby forming nanobubbles in the liquid carrier. The vibrational energy can include, for example, the frequency, amplitude, and acceleration of the relative motion between the liquid carrier and the triboelectric material. For example, as the liquid carrier flows through the channels 110a, 110b, the vibrational energy generated by the flow causes the liquid carrier to contact the triboelectric material on the inner walls 114 of the channels 110a, 110b. This contact results in the generation and accumulation of charge in the triboelectric material. The vibrational energy produced by the flow of the liquid carrier through channels 110a, 110b also causes the liquid carrier to separate from the triboelectric material on the interior walls 114 of channels 110a, 110b. This separation causes the accumulated charge to discharge from the surface of the triboelectric material into the liquid carrier, forming nanobubbles in the liquid carrier. The repeated cycles of contact and separation, and the resulting charge generation and transfer, result in the production of a high concentration of nanobubbles in the liquid carrier.

[0045] Nanobubbles are generated in the liquid carrier when it flows through the channels 110a, 110b under laminar (e.g., non-turbulent) flow conditions. For example, nanobubbles are generated when the Reynolds number of the liquid carrier flowing through the channels 110a, 110b is less than 3,000, e.g., less than 2,500. Without being bound by theory, it is believed that the flow of the liquid carrier under these conditions generates vibrational energy that causes the liquid carrier to contact and separate from the inner walls 114 of the channels 110a, 110b at a frequency and intensity (e.g., amplitude) sufficient to generate nanobubbles. In one example, the flow of the liquid carrier generates vibrational energy of at least about 90 J when the Reynolds number of the flow is less than 3,000 or less than 2,500.

[0046] It is believed that vibrational energy resulting from the velocity and hydraulic pressure gradient of the liquid carrier as it flows through the channels generates mechanical forces on the inner walls 114 of the channels 110a, 110b. These mechanical forces can be converted into electrical energy via liquid-solid contact electrification. For example, when the liquid carrier contacts the triboelectric material on the inner walls 114 of the channels 110a, 110b, a charge is generated in the triboelectric material. When the liquid carrier separates from the triboelectric material, the accumulated charge is discharged from the triboelectric material to the liquid carrier, resulting in the generation of nanobubbles in the liquid carrier. The strength of the charge discharge depends on the flow of the liquid carrier through the channels 110a, 110b, including, for example, the frequency and amplitude at which the liquid carrier separates from the inner walls 114 of the channels 110a, 110b. By flowing the liquid carrier through channels 110a, 110b under conditions such that the Reynolds number is less than 3,000 or less than 2,500, a frequency and amplitude of separation sufficient to produce a high concentration of nanobubbles in the liquid carrier can be achieved.

[0047] A flow of the liquid carrier having a Reynolds number of less than 3,000 or less than 2,500 can be achieved by a combination of the channel geometry and the liquid carrier flow rate. For example, nanobubbles are generated in channels 110a, 110b when the channel geometry (e.g., size) meets the geometric criteria and the flow rate meets the flow rate criteria.

[0048] In some embodiments, geometric criteria for achieving a Reynolds number of less than 3,000 or less than 2,500 for the flow of a liquid carrier, e.g., water, specify that the ratio of the average circumference of the channels 110a, 110b in the housing 106 to the average length of the flow path through the channels 110a, 110b be at least about 0.015, e.g., about 0.15 to about 150, about 0.15 to about 30, or about 0.025 to about 15. We use the term "about" herein to mean ±10% of the stated value. The circumference of a given channel is defined as 2π*R, where R is the radius of the channel; the average circumference of a channel is the sum of the circumferences of each channel divided by the total number of channels. The length of a given channel is defined as the linear distance between the beginning and end of the channel. The average length of a flow path, L, is the sum of the lengths of each channel divided by the total number of channels.

[0049] In some embodiments, the flow rate criteria for achieving a Reynolds number of less than 3,000 or less than 2,500 for the flow of a liquid carrier, e.g., water, is, for example, 3.79×10 -5 m 3 / min~3.79 m 3 / min, 3.79×10 -3 m 3 / min~1.89 m 3 / min, 7.57×10 -3 m 2 / min~9.46×10 -1 m 3 / min, or 1.89 x 10 -1 m 3 / min~5.68×10 -1 m 3 / min, e.g. at least 3.79 x 10 -3 m 3 / min is at least 3.79 x 10 -5 m 3 The condition is specified as flowing the liquid carrier through the device at a flow rate of 1 / min.

[0050] In one embodiment, the Reynolds number of less than 3,000 or less than 2,500 is at least 6×10 -7 m 3 at least 1 x 10 in a device with a volume of -6 cubic metres per minute (m 3 This can be achieved when the liquid carrier is flowing at a flow rate of approximately 90 J / min. These flow and geometric conditions are sufficient to produce a minimum of approximately 90 J of vibrational energy, which is believed to be sufficient to enable the production of nanobubbles.

[0051] The triboelectric material has a sufficient charge density to allow the generation and transfer of charge to form nanobubbles. For example, the triboelectric material has a charge density of, for example, about 15 μC / m 2 ~Approx. 1,200 μC / m 2 , about 50 μC / m 2 ~Approx. 1,000 μC / m 2 , about 200 μC / m 2 ~about 950 μC / m 2 , or approximately 700 μC / m 2 ~about 900 μC / m 2 etc., e.g., at least about 50 μC / m 2 , at least about 200 μC / m 2 , at least about 500 μC / m 2 , at least about 700 μC / m 2 , or at least about 800 μC / m 2 At least about 15 microcoulombs per square meter (μC / m 2The charge density of the triboelectric material may have an absolute value (e.g., a positive charge density or a negative charge density) of 1 / (1 / 2) / (1 / 2). The charge density of the triboelectric material can be measured, for example, based on the method described in Di Liu, et al., "Standardized measurement of dielectric materials' intrinsic triboelectric charge density through the suppression of air breakdown," Nature Communications (2022) 13:6019, the contents of which are incorporated herein by reference in their entirety.

[0052] The triboelectric material may be a triboelectric polymer, such as polytetrafluoroethylene (PTFE), polyethylene, polyvinyl chloride (PVC), polyethylene terephthalate glycol (PETG), acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), polyamide (PA), ethylene tetrafluoroethylene (ETFE), polymethyl methacrylate (PMMA), high-density polyethylene (HDPE), polyvinyl alcohol (PVA), polyethylene terephthalate glycol (PETG), polylactic acid (PLA), polyurethane, polypropylene, acrylic, or another suitable triboelectric material, or a combination of two or more of these materials. The triboelectric material may be triboelectric glass, ceramic, or carbon fiber. The triboelectric material may be an electrically conductive triboelectric material, such as a metal (e.g., copper, aluminum, stainless steel), or an electrically conductive oxide (e.g., titanium oxide or aluminum oxide). In some embodiments, multiple types of triboelectric materials are used in the same device, such as multiple types of polymers, multiple types of ceramics, multiple types of metals, or a combination of two or more polymers, metals, and ceramics. For example, the triboelectric material may be a ceramic coated or doped with an electrode material such as titanium oxide, aluminum oxide, stainless steel, aluminum, or copper. In some embodiments, the triboelectric material may be a material such as a filament material suitable for use in additive manufacturing techniques, such as, for example, engineering PLA filaments, ABS filaments, PVA filaments, PETG filaments, nylon filaments, carbon fiber filament composites, high impact polystyrene (HIPS), flexible thermoplastic polyurethane filaments (TPU), polypropylene filaments, or other suitable additive manufacturing materials.

[0053] The triboelectric material may have a surface texture that promotes contact and separation between the liquid carrier and the triboelectric material as the liquid carrier flows through channels 110 a, 110 b. For example, the triboelectric material may have a roughness of about 0.5×10, as characterized by the method described in E.S. Gadelmawla, et al., “Roughness parameters,” Journal of Materials Processing Technology (10 April 2002), Vol. 123, No. 1, the entire contents of which are incorporated herein by reference. -8 meters ~ 1 × 10 -2 The standard deviation of the surface height distribution in meters (RMS or Rq) is approximately 0.5 × 10 -8 meters ~ 1 × 10 -2 The triboelectric material has a surface texture characterized by a mean spacing (Si) of profile peaks in meters. In some embodiments, the surface texture of the triboelectric material is provided during formation of the material (e.g., during deposition of the material, such as during an additive manufacturing process). In some embodiments, the triboelectric material so deposited is treated, such as by surface roughening, to achieve the desired surface texture.

[0054] Other configurations of flow channels may also be used to generate high concentrations of nanobubbles by flowing a liquid carrier through the channels under conditions such that the Reynolds number of the flow is less than 3,000 or less than 2,500. For example, while channels 110a and 110b in FIG. 1 are shown as straight channels, the channels need not be straight; for example, the channels may be curved. As another example, although channels 110a and 110b in FIG. 1 are shown as having circular cross-sections, channels with other cross-sectional shapes may also be used. As another example, channels 110a and 110b may contain one or more internal elements (e.g., rods disposed within each channel and extending along part or all of the length of the channel) that define additional interior walls containing triboelectric material. The channels of the device may have a uniform geometry (e.g., circumference, length, or cross-sectional shape), or one or more of the channels may have a geometry that differs from the geometry of the other channels.

[0055] In some embodiments, the device 100 may include a port for injecting a gas into the liquid carrier. The gas injection port may be upstream of the channels 110a, 110b. For example, the port may be for injecting a gas into a distribution chamber 105 disposed between the inlet port 102 and the channels 110a, 110b. Injecting a gas into the liquid carrier may further enhance nanobubble generation.

[0056] In some embodiments, an apparatus for producing a composition containing nanobubbles dispersed in a liquid carrier contains more than two flow channels, e.g., 2-20 channels, 5-50 channels, 10-100 channels, 100-500 channels, or 500-1000 channels, e.g., at least 10 channels, at least 25 channels, at least 100 channels, or at least 500 channels. Regardless of the number of channels in the apparatus, nanobubbles are produced when the flow of the liquid carrier through the apparatus has a Reynolds number of less than 3,000 or less than 2,500, e.g., when the channel geometry and liquid carrier flow rate meet the geometric and flow rate criteria described above.

[0057] 2 illustrates an apparatus 200 for generating a composition containing nanobubbles dispersed in a liquid carrier. A housing 206 of the apparatus 200 defines four flow channels 210a-210d, and the interior wall 214 of each flow channel 210a-210d contains a triboelectric material. The flow channels 210a-210d are fluidly connected to an inlet 202 via a distribution chamber 205. The liquid carrier, containing a high concentration of nanobubbles, exits the housing 206 through an outlet 204.

[0058] 2, flow channels 210a-210d have different lengths and generally similar circumferences. Nanobubbles are generated within flow channels 210a-210d of device 200 when the Reynolds number of the liquid carrier flow through device 200 is less than 3,000 or less than 2,500. For example, nanobubbles are generated within channels 210a-210d when the channel geometry (e.g., size) and liquid carrier flow rate meet the geometric and flow rate criteria described above. Notably, although the individual channels 210a-210d in device 200 have different lengths, the same geometric and flow rate criteria still apply.

[0059] 3, an apparatus 300 for generating a composition containing nanobubbles dispersed in a liquid carrier includes a housing 306 defining channels 310a-310b (collectively referred to as channels 310) fluidly connected to an inlet 302 and an outlet 304, e.g., as described above. Nanobubbles are generated when the Reynolds number of the flow of the liquid carrier through the apparatus 300 is less than 3,000 or less than 2,500, e.g., when the channel geometry (e.g., size) and the liquid carrier flow rate meet the geometric and flow rate criteria described above.

[0060] Apparatus 300 contains a flow controller 320, such as one or more valves, e.g., a throttle valve, to control the flow of the liquid carrier within distribution chamber 305 and, therefore, within channel 310. In the example of Figure 3, flow controller 320 is disposed between inlet 302 and channel 310. In some embodiments, the flow controller may be disposed upstream of inlet 302.

[0061] Flow controller 320 may include a processor or controller that controls the operation of the valves to produce a time-varying (e.g., pulsed) flow rate according to a flow waveform, such as a square wave 322, a sine wave 324, a triangular wave, a sawtooth wave, or another suitable waveform. The time-varying flow of the liquid carrier affects the hydrodynamic conditions of the flow within the channel, which affects nanobubble production, for example, by enhancing contact and separation between the liquid carrier and the inner walls of channel 310. For example, the time-varying flow of the liquid carrier through channel 310 results in the volume of liquid carrier flowing through channel 310 being divided by the volume of void space, which enhances contact and separation and therefore nanobubble production. In some embodiments, flow controller 320 may control the direction of flow, for example, so that the liquid carrier is provided to a subset or all of flow channels 310 at any given time.

[0062] 4, an apparatus 400 for generating a composition containing nanobubbles dispersed in a liquid carrier includes a housing 406 containing channels 410a-410b (collectively referred to as channels 410) fluidly connected to an inlet 402 and an outlet 404, e.g., as described above. Nanobubbles are generated when the Reynolds number of the flow of the liquid carrier through the apparatus 400 is less than 3,000 or less than 2,500, e.g., when the channel geometry (e.g., size) and the liquid carrier flow rate meet the geometric and flow rate criteria described above.

[0063] Apparatus 400 includes an external power source 420 configured to generate charge within the triboelectric material of channel 410, e.g., to supplement charge generated by contact between the liquid carrier and the triboelectric material. In some embodiments, external power source 420 is a resonator, such as an electromagnetic or mechanical resonator, that increases the frequency and amplitude of contact and separation between the liquid carrier and the inner wall of channel 410, thereby supplementing charge generation within the triboelectric material and enhancing charge transfer to the liquid carrier. For example, the resonator may be a jacket that completely or partially surrounds the housing. In some embodiments, the external power source is a current source, such as a battery, that is connected to the triboelectric material to inject charge into the triboelectric material. In some embodiments, the external power source is a magnetic field source configured to induce a current to inject charge into the triboelectric material.

[0064] 5A and 5B are schematic diagrams of an exemplary apparatus 500 for generating a composition containing nanobubbles dispersed in a liquid carrier. FIG. 5A is a top view of the apparatus, and FIG. 5B is a perspective view of the interior of the apparatus. The apparatus 500 contains a housing 506 having nine tubes 510 disposed therein that define channels. The tubes 510 are arranged in a two-dimensional (here, 3×3) array. The tubes 510 are fluidly connected to an inlet 502 defined in a top wall 512 of the housing 506. The liquid carrier entering the inlet 502 is distributed within a distribution chamber 505 to the nine tubes 510. The tubes are also fluidly connected to an outlet 504 defined in the top wall 512 of the housing. The liquid carrier having a high concentration of nanobubbles dispersed therein is collected at the outlet 504. In device 500, inlet 502 and outlet 504 are defined on the same wall 512 of housing 506, although in some embodiments the inlet and outlet may be defined on different walls of housing 506.

[0065] 6A and 6B are schematic diagrams of the exterior (FIG. 6A) and interior (FIG. 6B) of an exemplary miniaturized apparatus 600 for producing a composition containing nanobubbles dispersed in a liquid carrier. The apparatus 600 contains an inlet 602 disposed at a first end of a housing 606 and an outlet 604 disposed at an opposite end of the housing 606. In the illustrated example, two flow channels 610a, 610b are defined within the housing 606, although other numbers of channels may also be used. As noted above, the nanobubble generation techniques described herein do not require an external gas or energy source, making it possible to use the miniaturized apparatus for nanobubble generation.

[0066] Miniaturized devices such as device 600 can be used to produce nanobubbles when the channel geometry and liquid carrier flow rate meet the geometric and flow rate criteria described above, and when the device meets certain minimum sizes. For example, device 600 may have a length L1 of 10 mm, a width L2 of 7 mm, and a thickness T of 4 mm, and a diameter of 2.8×10-7 m 3 and the channel geometry and liquid carrier flow rate meet the geometric and flow rate criteria described above, the device is of sufficient size to produce nanobubbles.

[0067] In some embodiments, multiple devices described above may be assembled in series to generate nanobubbles in a larger volume of liquid carrier, and in some embodiments, multiple devices described above may be assembled in parallel to increase the concentration of nanobubbles generated in the liquid carrier.

[0068] As described above, the surface texture of the triboelectric material on the interior wall of a channel has a surface texture that promotes contact and separation between the liquid carrier and the triboelectric material as the liquid carrier flows through the channel. FIG. 7 includes plots of exemplary surface texture profiles for the interior wall of a channel used for nanobubble production, e.g., surface texture profiles that can promote the contact and separation dynamics associated with nanobubble production. The plot in FIG. 7 plots the thickness of the interior wall of the channel (e.g., the relative thickness of the interior wall to the average thickness of the interior wall) versus the length along the channel. The surface texture is characterized by the average thickness of the interior wall, the standard deviation of the thickness, and the rate of variation of the thickness along the length of the channel (e.g., dy / dx, or the change in thickness over the distance along the channel). As illustrated in the plot in FIG. 7, channels with smooth interior walls (e.g., a small standard deviation, a small rate of variation, or both) and channels with rougher interior walls (e.g., a larger standard deviation, a larger rate of variation, or both) can be used for nanobubble production.

[0069] In some embodiments, the material of the interior walls of the channels is selected to create a contact angle between the liquid carrier and the interior walls that facilitates the contact and separation dynamics involved in nanobubble generation. For example, the interior wall material may be selected to have a targeted hydrophobicity, e.g., a targeted surface energy.

[0070] 8, in an exemplary method for producing a composition containing nanobubbles dispersed in a liquid carrier, the liquid carrier is flowed from an inlet into at least two channels containing a triboelectric material (800). The liquid carrier is flowed through the channels such that the flow is laminar, e.g., the Reynolds number of the flow is less than 3,000 or less than 2,500 (802). For example, the liquid carrier is flowed through channels having a geometry such that the ratio of the average circumference of the channel to the average length of the flow path through the channel is at least about 0.015, at least 3.79×10 -5 m 3 The liquid carrier is flowed at a flow rate of 804 / min. The liquid carrier is collected at an outlet downstream of the channel and fluidly connected to the channel, where the liquid carrier collected at the outlet has nanobubbles dispersed therein.

[0071] Nanobubble-containing compositions produced according to the above-described approach are useful in numerous applications. Because nanobubbles are stable in liquid carriers, they can be transported over long distances without dissolving or coalescing in the liquid carrier. Furthermore, because of their high concentration in liquid compositions, nanobubbles are an efficient source for transporting gases to desired sources. Additionally, due to their smaller surface area and increased solubility, nanobubble-containing compositions are many times more efficient at transferring gases, such as oxygen, into liquids than conventional aeration.

[0072] One application of the nanobubble-containing composition produced based on the above-described approach relates to water treatment. For example, a composition containing nanobubbles dispersed in a liquid carrier is transported to a water source requiring treatment. Examples of water that can be treated include wastewater, oxygen-deficient water, drinking water, and water for aquaculture. In the case of drinking water, the nanobubble-containing composition may be used to make potable water. Nanobubbles may also be used in carbonated beverages.

[0073] One example of a water treatment application for these nanobubble compositions relates to environmental water remediation. Because nanobubbles have a long lifespan in water and significant mixing potential, the compositions can be used to improve the ecological balance of surface waters such as lakes, rivers, and oceans. Enriching water bodies with high oxygen content helps restore beneficial aerobic activity, which acts to destroy sludge, hydrogen sulfide, environmental toxins, and pathogenic organisms.

[0074] Another application of nanobubble-containing compositions produced according to the above-described approach relates to the transport of liquids, such as crude oil or drilling fluids, through pipes. Often, these liquids are viscous and must be transported over significant distances. A composition containing nanobubbles dispersed in a liquid carrier may be combined with a liquid (e.g., crude oil, drilling fluid, or hydraulic fracturing fluid) to create a pumpable composition having a viscosity less than that of the liquid, creating a pumpable composition that can be transported through a pipe to a desired destination.

[0075] Another application of the nanobubble-containing composition produced according to the above-described approach relates to treating plant roots to promote plant growth. For example, a composition containing nanobubbles dispersed in a liquid carrier can be combined with another liquid to create an oxygen-rich composition, which can then be applied to plant roots. Similarly, a composition containing nanobubbles in a liquid carrier can be used in aquaculture to create a high-oxygen environment that promotes the growth of fish and crustaceans.

[0076] Another application of nanobubble-containing compositions produced according to the above-described approach relates to improved heat transfer. For example, when liquids to be heated or cooled are injected with compositions containing nanobubbles in a liquid carrier, a faster rate of temperature change can be produced in the liquid. One non-limiting exemplary application is in cooling towers.

[0077] Another application of nanobubble-containing compositions produced according to the above-described approach relates to tissue preservation: when combined with tissue cells, the nanobubble composition can preserve the cells even after freezing.

[0078] Another application of nanobubble-containing compositions produced based on the above-described approach relates to evaporation. Compositions containing nanobubbles dispersed in a liquid carrier have a higher evaporation potential than regular water. Therefore, combining water in a cooling tower with a nanobubble composition can enhance evaporation in the cooling tower, improving the efficiency associated with the cooling process.

[0079] Another application of the nanobubble-containing composition produced based on the above-described approach relates to the use of the nanobubble composition to treat membranes or geothermal wells. When the membrane or geothermal well is continuously exposed to a composition containing nanobubbles in a liquid carrier, the composition can prevent the accumulation of contaminants on the surface of the membrane or geothermal well. This is because the nanobubbles are negatively charged and can form geometric structures (e.g., lattices) on the surface of the membrane or geothermal well that exclude certain contaminants, such as salts or organic contaminants.

[0080] Another application of nanobubble-containing compositions produced according to the above-described approaches relates to the use of the nanobubble compositions to reduce or prevent scale formation, for example, in cooling towers.

[0081] Another application of nanobubble-containing compositions produced according to the above-described approaches relates to the use of nanobubble compositions in the medical field.

[0082] Another application of the nanobubble-containing compositions produced according to the above-described approaches relates to the use of the nanobubble compositions in the context of electrolytic processes, such as the production of hydrogen, oxygen, chlorine, or other electrolytically produced elements or compounds. For example, the nanobubble-containing compositions may be incorporated into an electrolyte for electrolytic processes.

[0083] Certain aspects of the subject matter have been described above. Other aspects are within the scope of the following claims.

Claims

1. 1. A method for producing a composition comprising nanobubbles dispersed in a liquid carrier, comprising: flowing a liquid carrier from an inlet through at least two channels each containing a triboelectric material, the flow comprising flowing the liquid carrier such that a Reynolds number for the flow of the liquid carrier through the at least two channels is less than 3000; and flowing the liquid carrier through the at least two channels generates vibrational energy that (i) contacts the liquid carrier with the triboelectric material such that a charge is produced within the triboelectric material, and (ii) separates the liquid carrier from the triboelectric material such that the charge is discharged to the liquid carrier to form nanobubbles dispersed in the liquid carrier. The method.

2. The step of flowing the liquid carrier through the at least two channels comprises flowing the liquid carrier through at least 3.79×10 -5 m 3 10. The method of claim 1, comprising flowing at a flow rate of 1 / min.

3. 10. The method of claim 1, further comprising collecting the liquid carrier having nanobubbles dispersed therein at an outlet, wherein the liquid carrier flows from the channel into the outlet.

4. 10. The method of claim 9, further comprising controlling the flow rate of the liquid carrier through the at least two channels.

5. The method of claim 4, further comprising pulsing the flow of the liquid carrier through the at least two channels.

6. 10. The method of any one of the preceding claims, including generating an electric charge in the triboelectric material using an external power source.

7. 7. The method of claim 6, wherein the generating step includes applying vibrations to the triboelectric material using a resonator.

8. 8. The method of claim 6 or 7, wherein the step of generating a charge comprises injecting a charge into the triboelectric material from a current source.

9. 2. The method of claim 1, wherein flowing the liquid carrier through the at least two channels generates a vibrational energy of at least 90 J.

10. Flowing the liquid carrier such that the Reynolds number of the flow is less than 3000 may be performed by flowing the liquid carrier at least 3.79×10 -5 m 3 10. The method of claim 9, further comprising flowing the mixture at a flow rate of 100 / min / min and wherein the ratio of the average circumference of the channel to the average flow path length of the channel is at least about 0.

015.

11. an inlet for receiving the liquid carrier from a liquid source; Outlets; and (a) first and second ends fluidly coupled to the inlet and the outlet, respectively; (b) at least two channels for receiving the liquid carrier from the inlet, the at least two channels having a ratio of an average perimeter of the channels to an average flow path length of the channels of at least about 0.015; and (c) a flow rate of at least 15 microcoulombs per square meter (μC / m 2 and a triboelectric material having an absolute value of charge density of 1. An apparatus for generating a composition comprising nanobubbles dispersed in a liquid carrier, comprising: The liquid carrier is at least 3.79 x 10 -5 m 3 / min flowing through the device, the device is configured to generate vibrational energy that (i) contacts the liquid carrier with the triboelectric material such that a charge is produced within the triboelectric material, and (ii) separates the liquid carrier from the triboelectric material such that the charge is discharged into the liquid carrier to form nanobubbles dispersed in the liquid carrier. The device.

12. the absolute value of the charge density of the triboelectric material is at least 50 μC / m 2 12. The device of claim 11, wherein:

13. 13. The device of claim 11, wherein the ratio of the average circumference of said channels to the average flow path length of said channels is in the range of about 0.015 to about 150.

14. 14. The device of claim 11, wherein the triboelectric material comprises a polymer.

15. 15. The device of any one of claims 11 to 14, wherein the triboelectric material comprises PTFE.

16. 16. The device of any one of claims 11-15, wherein the triboelectric material is selected from the group consisting of polytetrafluoroethylene (PTFE), polyethylene, polyvinyl chloride (PVC), polyethylene terephthalate glycol (PETG), acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), polyamide (PA), ethylene tetrafluoroethylene (ETFE), polymethyl methacrylate (PMMA), and combinations thereof.

17. 17. The device of any one of claims 11 to 16, wherein the channel is defined by a wall configured to contact the liquid carrier, and at least a portion of the wall comprises the triboelectric material.

18. At least a portion of the triboelectric material is about 0.5×10 -8 meters to 1 x 10 -2 The standard deviation of the surface height distribution in meters (RMS or Rq) is approximately 0.5 x 10 -8 meters to 1 x 10 -2 18. The device of any one of claims 11 to 17, having a surface texture characterized by a mean spacing (Si) of contour peaks in meters.

19. 19. The device of any one of claims 11 to 18, wherein the inlet, housing, or both, distributes the liquid carrier into at least two flow paths, each flow path flowing into a separate channel.

20. 20. The device of any one of claims 11 to 19, wherein each channel is a single-channel tube.

21. 21. The device of any one of claims 11 to 20, wherein the at least two channels are contained within a multichannel tube.

22. 22. The device of any one of claims 11 to 21, wherein the housing defines at least two channels.

23. 23. The apparatus of any one of claims 11 to 22, including an external power source for further producing said charge in said triboelectric material.

24. 24. The device of any one of claims 11 to 23, wherein the external power source is a resonator, a battery, or both.

25. 25. The apparatus of claim 11, wherein the resonator is an electromagnetic resonator or a mechanical resonator.

26. 26. The device of any one of claims 11 to 25, comprising a flow controller configured to control the flow of the liquid carrier through the at least two channels.

27. 27. A method for producing a composition comprising nanobubbles dispersed in a liquid carrier using the device of any one of claims 11 to 26, comprising: introducing a liquid carrier from a liquid source into said inlet; and receiving the liquid carrier from the inlet into the at least two channels of the housing; Including, As the liquid carrier flows through the device, the device generates vibrational energy that (i) contacts the liquid carrier with the triboelectric material such that an electric charge is produced within the triboelectric material, and (ii) separates the liquid carrier from the triboelectric material such that the electric charge is discharged into the liquid carrier to form nanobubbles dispersed in the liquid carrier. The method.

28. 1.5×10 -7 ~6.5×10 -1 m 3 In the device having a flow path volume of 1×10 -6 cubic metres per minute (m 3 / min) ~4 m 3 28. The method of claim 27, wherein the device is configured to produce a minimum of about 90 joules (J) of vibrational energy when the liquid carrier is flowing at a flow rate of 1 / min.

29. 1. A method for treating water, comprising: Producing a composition comprising nanobubbles dispersed in a liquid carrier using the method of any one of claims 1 to 10; and transporting the composition to a water source requiring treatment. The method comprising:

30. 1. A method of transporting a liquid through a pipe, comprising: Producing a composition comprising nanobubbles dispersed in a liquid carrier using the method of any one of claims 1 to 10; combining the composition with a liquid to create a pumpable composition having a viscosity less than that of the liquid; and transporting said pumpable composition through a pipe to a desired destination. The method comprising:

31. 1. A method for delivering a liquid to the roots of a plant to promote plant growth, comprising: Producing a composition comprising nanobubbles dispersed in a liquid carrier using the method of any one of claims 1 to 10; combining the composition with a liquid to create an oxygen-enriched composition; and applying the composition to the roots of a plant to promote plant growth. The method comprising:

32. 1. A method of delivering a fluid during a medical procedure, comprising: Producing a composition comprising nanobubbles dispersed in a liquid carrier using the method of any one of claims 1 to 10; and applying the composition to a medical device or to a patient during a medical procedure. The method comprising:

33. 1. A method for regulating temperature in a system, comprising: Producing a composition comprising nanobubbles dispersed in a liquid carrier using the method of any one of claims 1 to 10; and applying said composition to said system to inhibit the formation of scale within said system. The method comprising:

34. 1. A method of electrolysis comprising: Producing a composition comprising nanobubbles dispersed in a liquid carrier using the method of any one of claims 1 to 10; and performing electrolysis using a fluid containing the composition as an electrolyte; The method comprising:

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