A nanobubble generator and a method of generating nanobubbles

Abstract

A nano-bubble generator 100 comprising: a container 102, for holding a liquid; an inlet 106, for introducing gas into the liquid as one or more bubbles; at least one propeller 108 for propelling the g

Description

TECHNOLOGICAL FIELD Examples of the disclosure relate to a nanobubble generator and a method of generating nanobubbles. Some relate to a nanobubble generator and a method of generating nanobubbles for introducing gas into a liquid as nanobubbles. BACKGROUND Nanobubbles have a number of unique properties, for example: low buoyancy; ability to transfer gas efficiently; pathogen inactivation; and small size. BRIEF SUMMARY The following portion of this ‘Brief Summary’ section describes various features that may be features of any of the examples described in the foregoing portion of the ‘Brief Summary’ section. The description of a function should additionally be considered to also disclose any means suitable for performing that function. According to various, but not necessarily all, examples there is provided a nanobubble generator comprising: a container, configured to hold a liquid; an inlet, configured to introduce gas into the liquid as one or more bubbles; at least one propeller configured to propel the gas in a first direction, away from the inlet; and a battering portion, configured to rotate about a central axis, the central axis extending in the first direction, wherein the battering portion is configured to batter the one or more bubbles to split the one or more bubbles into sub-bubbles. In some, but not necessarily all examples, the battering portion comprises at least one battering pair, the battering pair comprising: a first paddle pair, extending along a second axis; and a second paddle pair, extending along a third axis, the third axis substantially perpendicular to the second axis. In some, but not necessarily all examples, the second axis and the third axis are substantially perpendicular to the central axis. In some, but not necessarily all examples, the propeller and the battering portion are connected to a central rod, the central rod extending along the central axis, wherein the central rod is configured to rotate and cause rotation of the propeller and the battering portion. In some, but not necessarily all examples, the nanobubble generator comprises an output portion comprising at least one battering pair. In some, but not necessarily all examples, the nanobubble generator comprises a plurality of propellers. In some, but not necessarily all examples, the nanobubble generator comprises a plurality of battering portions. In some, but not necessarily all examples, each propeller is separated from another propeller by a battering portion. In some, but not necessarily all examples, the output portion is positioned below the lowest propeller. In some, but not necessarily all examples, the nanobubble generator comprises: four propellers; three battering portions, each battering portion comprising 20 battering pairs; and one output portion, the outlet portion comprising six battering pairs. In some, but not necessarily all examples, the container is a cylindrical container having a diameter sized to allow rotation of the propeller and the battering portion. In some, but not necessarily all examples, the nanobubble generator comprises a pump configured to pump liquid into the container. In some, but not necessarily all examples, the nanobubble generator comprises an outlet configured to allow egress of liquid and sub-bubbles from the container. In some, but not necessarily all examples, the nanobubble generator is configured to be submerged in liquid. In some, but not necessarily all examples, the battering portion is configured to batter the one or more bubbles until the one or more sub-bubbles comprise nanobubbles. In some, but not necessarily all examples, the liquid comprises water. In some, but not necessarily all examples, the gas comprises oxygen. According to various, but not necessarily all, examples there is provided a method of generating nanobubbles comprising: introducing gas from an inlet into a liquid as one or more bubbles, wherein the liquid is held by a container; propelling the gas in a first direction, away from the inlet, using a propeller; and battering the one or more bubbles to split the one or more bubbles into sub-bubbles using a battering portion. In some, but not necessarily all examples, the method comprises pumping the liquid into the container. In some, but not necessarily all examples, the method comprises allowing egress of liquid and sub-bubbles from the container. In some, but not necessarily all examples, the method is carried out, at least in part, by the nanobubble generator above. According to various, but not necessarily all, examples there is provided examples as claimed in the appended claims. While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all of the features described in respect of other examples of the disclosure, and vice versa. Also, it is to be appreciated that any one or more or all of the features, in any combination, may be implemented by / comprised in / performable by an apparatus, a method, and / or computer program instructions as desired, and as appropriate. BRIEF DESCRIPTION Some examples will now be described with reference to the accompanying drawings in which: FIG 1 schematically illustrates an example nanobubble generator; FIG 2 schematically illustrates an example nanobubble generator; FIG 3 illustrates an example battering pair; FIG 4 illustrates an example paddle; FIG 5 schematically illustrates an example nanobubble generator; FIGs 6A and 6B schematically illustrate an example nanobubble generator; FIG 7 illustrates an example method of generating nanobubbles; FIG 8 illustrates an example method of generating nanobubbles; FIG 9 illustrates an example controller; and FIG 10 illustrates an example computer program delivery apparatus. The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures. DETAILED DESCRIPTION The following description and the enclosed FIGs relate to various examples of a nanobubble generator 100 comprising: a container 102, configured to hold a liquid 104; an inlet 106, configured to introduce gas into the liquid 104 as one or more bubbles; at least one propeller 108 configured to propel the gas in a first direction x, away from the inlet 106; and a battering portion 110, configured to rotate about a central axis A, the central axis A extending in the first direction x, wherein the battering portion 110 is configured to batter the one or more bubbles to split the one or more bubbles into sub-bubbles. A nanobubble is a bubble with a size lower than a threshold size. In examples, the size is a diameter of a bubble. In examples, the threshold size is 100 pm, 50 pm or 10 pm. In other examples, the threshold size is 200 nm. In examples, the size of a nanobubble is such that nanobubbles cannot be seen by the human eye. In some such examples, if clouds of bubbles are visible in a liquid, those bubbles are not nanobubbles. In some such examples, the presence of nanobubbles may be identified by illuminating a portion of a liquid with a light source such as a laser. If nanobubbles are present in the portion of the liquid, the light will be diffracted by a refractive index that is different to a refractive index of the liquid. In examples in which the nanobubbles contain a gas, the presence of nanobubbles may be identified by determining if the gas is present in the liquid 104 in an amount above a threshold amount. For example, if the nanobubbles contain oxygen, the presence of nanobubbles may be detected using an oxygen meter. If the level of oxygen is above a threshold, nanobubbles are present. FIG 1 schematically illustrates an example of a nanobubble generator 100. FIG 2 illustrates features of the nanobubble generator 100. Features not illustrated in FIG 1 are illustrated in FIG 2. The nanobubble generator 100 comprises a container 102. The container 102 is configured to hold a liquid 104. In some, but not necessarily all, examples, the liquid 104 comprises water. In some, but not necessarily all, examples, the container 102 is a cylindrical container having a diameter sized to allow rotation of the propeller 108 and the battering portion 110. The nanobubble generator 100 comprises an inlet 106. The inlet 106 is configured to introduce gas into the liquid 104 as one or more bubbles. In some, but not necessarily all, examples, the gas comprises oxygen. In some examples, the gas comprises any one or more of: air; carbon dioxide, hydrogen; nitrogen; or ozone. In examples, the bubbles comprise aerosolized particles, for example medical drugs, fertilizers, nutrients or pesticides. In examples, the quantity of gas to be introduce into the container 102 is determined based on an optimal ratio of bubbles to liquid. In some, but not necessarily all, examples, the nanobubble generator 100 comprises a pump 118 configured to pump liquid 104 into the container 102. The nanobubble generator 100 comprises at least one propeller 108. The at least one propeller 108 is configured to propel the gas and the liquid 104 in a first direction x, away from the inlet 106. In examples, the propeller 108 comprises a plurality of blades, for example four blades. In examples, the blades are elongate blades with triangular cross-section. In some such examples, the cross-section of the blades is a right-angled triangle with a base angle of 30°. The nanobubble generator 100 further comprises a battering portion 110. The battering portion 110 is configured to batter the bubbles to form sub-bubbles. In 7 some examples, the battering portion 110 is configured to batter the bubbles to form nanobubbles. In examples, the propeller 108 and / or the battering portion 110 is configured to rotate about a central axis A, the central axis A extending in the first direction x. In some but not necessarily all examples, the propeller 108 and the battering portion 110 are connected to a central rod 114. The central rod 114 extends along the central axis A and is configured to rotate and cause rotation of the propeller 108 and the battering portion 110. In some examples, the nanobubble generator 100 comprises a motor 122 configured to rotate the rod 114. Rotation of the rod 114 causes rotation of at least one of: the propeller(s) 108, the battering portion(s) 110 or the output portion 116. In examples, the motor 122 causes rotation of the rod 114 at between 1000 and 4000RPM. In some examples the battering portion 110 comprises at least one battering pair 112. FIG 3 illustrates an example battering pair 112. The battering pair 112 comprises a first paddle pair 302, extending along a second axis B, and a second paddle pair 304, extending along a third axis C. The third axis C is substantially perpendicular to the second axis B. In some such examples, the second axis B and the third axis C are substantially perpendicular to the central axis A. In examples, the first paddle pair 302 and the second paddle pair 304 each comprise a first paddle 302a, 304a and a second paddle 302b, 304b. The first paddle 302a, 304a and the second paddle 302b, 304b are elongate paddles with rectangular crosssection. The first paddle 302a, 304a and the second paddle 302b, 304b are connected to a central portion 306. The first paddle 302a, 304a extends from a first position of the central portion 306 in a second direction y along the second axis B and a third direction z along the third axis C respectively. The second paddle 302b, 304b extends from a second position of the central portion 306, opposite the first position, negatively in the second direction y along the second axis B and negatively in the third direction z along the third axis C respectively. Thus, there are four paddles 302,304 in a battering pair 112 and each of the four paddles 302, 304 has an angle of 90° between itself and another paddle 302,304 of the battering pair 112. In some examples, such as the example illustrated in FIG 4, at least one of the paddles 302,304 comprises one or more transverse holes 402. The one or more transverse holes 402 are through-holes extending perpendicular to the second axis B or the third axis C, from a first face of the paddle 302, 304 to a second face of the paddle 302,304. The hole 402 has a first diameter on the first face and on the second face. The diameter decreases from the first face towards the second face until it reaches a second diameter at a first depth. The diameter of the hole 402 is then constant between the first depth and the second depth. The diameter increases from the second depth towards the second face until it reaches the first diameter. The holes 402 are venturi tubes, that is, the holes 402 are shaped to produce a venturi effect. The rotation of the paddles 302,304 forces the liquid 104 and the bubbles into the holes 402 under high pressure. The shape of the holes 402 causes a change of speed and pressure of the liquid 104 and the bubbles. The change in speed and pressure of the bubbles causes the bubbles to split into sub-bubbles. Thus, the combination of the battering portion 110 battering the bubbles and the venturi tubes applying the venturi effect to the bubbles causes a higher rate of bubble-splitting. In some, but not necessarily all, examples, the nanobubble generator 100 comprises a plurality of propellers 108 and / or a plurality of battering portions 110. In some such examples, each propeller 108 is separated from another propeller 108 by a battering portion 110. That is, there is at least one battering portion 110 between consecutive propellers 108. The rotation of the propeller(s) 108 creates a vortex in the liquid 104 which causes the gas to move in the first direction x. The vortex minimizes upwards movement, caused by buoyancy, of the bubbles / sub-bubbles. The battering portion 110 batters the bubbles by hitting the bubbles. Hitting the bubbles cause the bubbles to split into sub-bubbles. Sub-bubbles may be further hit to cause them to split into further sub-bubbles. In examples, the battering portion 110 is configured to batter the one or more bubbles until the one or more sub-bubbles comprise nanobubbles. In some, but not necessarily all examples, the nanobubble generator 100 comprises an output portion 116. The output portion 116 comprises at least one battering pair 112. In some such examples, the output portion 116 is positioned below the lowest propeller 108. In some, but not necessarily all examples, the nanobubble generator 100 comprises an outlet 120 configured to allow egress of liquid 104 and sub-bubbles from the container 102. In examples, the sub-bubbles have low buoyancy. The sub-bubbles may thus descend out of the outlet 120. In some, but not necessarily all, examples, the nanobubble generator 100 is configured to be submerged in liquid. In some such examples, the liquid in which the nanobubble generator 100 is submerged is the same type of liquid as the liquid 104 held in the container 102. In examples, the nanobubble generator 100 may be submerged in a river, lake, pool, or other natural or man-made body of water. In some such examples, the sub-bubbles exit the container 102 through the outlet 120 into the liquid in which the nanobubble generator 100 is submerged. Thus, the gas is introduced into the liquid in which the nanobubble generator 100 is submerged as sub-bubbles. In some such examples, the pump 118 is configured to pump a portion of the liquid in which the nanobubble generator 100 is submerged into the nanobubble generator 100. In some examples, the nanobubble generator 100 comprises a frame configured to hold the nanobubble generator 100 within the liquid. FIG 5 illustrates another example nanobubble generator 100. In the example of FIG 5, the nanobubble generator 100 comprises: four propellers 108; three battering portions 110; and one output portion 116. In some examples, each battering portion 110 comprises 20 battering pairs 112. In some examples, the output portion 116 comprises six battering pairs 112. FIG 5 is simplified for ease of viewing; therefore, in such examples, in FIG 5, each box illustrating a battering pair 112 of a battering portion 110 represents four battering pairs 112 and each box illustrating a battering pair 112 of the output portion 116 represents six battering pairs 112. In the example of FIG 5, the four propellers 108 create a vortex that causes liquid 104 and bubbles to move in the first direction x. The vortex overcomes the natural buoyancy of the bubbles to cause downwards movement in the first direction x. The bubbles are battered by the battering pairs 112 to split into sub-bubbles and the sub-bubbles continue to be moved in the first direction x by the vortex. The sub-bubbles are battered until they form nanobubbles. The low buoyancy of the nanobubbles in combination with the vortex cause the nanobubbles to move towards and out of the outlet 120 into the surrounding liquid (not shown). FIGs 6A and 6B illustrate a further example nanobubble generator 100. In the example of FIGs 6A and 6B, the nanobubble generator 100 comprises a plurality of central axes A1, A2. At least one first propeller 108a and at least one first battering portion 110a are configured to rotate about a first central axis A1 of the plurality of central axes. At least one second propeller 108b and at least one second battering portion 110b are configured to rotate about a second central axis A2 of the plurality of central axes. In examples, the at least one first propeller 108a and the at least one second propeller 108b overlap such that a portion of the at least one second propeller 108b is directly below a portion of the at least one first propeller 108a in the first direction x. In some such examples, the at least one first battering portion 110a and the at least one second battering portion 110b overlap such that a portion of the at least one second battering portion 110b is directly below a portion of the at least one first battering portion 110a in the first direction. In other examples, there is no overlap between at least one of: the at least one first propeller 108a and the at least one second propeller 108b; and the at least one first battering portion 110a and the at least one second battering portion 110b. In examples in which the nanobubble generator 100 comprises a plurality of first propellers 108a and a plurality of second propellers 108b, the plurality of first propellers 108a and the plurality of second propellers 108b overlap in an alternating manner. For example, a propeller 108a of the plurality of first propellers 108a may overlap two propellers 108b of the plurality of second propellers 108b such that a portion of the propeller 108a of the plurality of first propellers 108a is directly below a portion of one propeller 108b of the plurality of second propellers 108b and directly above a portion of another propeller 108b of the plurality of second propellers 108b in the first direction x. Additionally or alternatively, a propeller 108b of the plurality of second propellers 108b may overlap two propellers 108a of the plurality of first propellers 108a such that a portion of the propeller 108b of the plurality of second propellers 108b is directly below a portion of one propeller 108a of the plurality of first propellers 108a and directly above a portion of another propeller 108a of the plurality of first propellers 108a in the first direction x. In examples in which the nanobubble generator 100 comprises a plurality of first battering portions 110a and a plurality of second battering portions 110b, the plurality of first battering portions 110a and the plurality of second battering portions 110b overlap in an alternating manner. For example, a battering portion 110a of the plurality of first battering portions 110a may overlap two battering portions 110b of the plurality of second battering portions 110b such that a portion of the battering portion 110a of the plurality of first battering portions 110a is directly below a portion of one battering portion 110b of the plurality of second battering portions 110b and directly above a portion of another battering portion 110b of the plurality of second battering portions 110b in the first direction x. Additionally or alternatively, a battering portion 110b of the plurality of second battering portions 110b may overlap two battering portions 110a of the plurality of first battering portions 110a such that a portion of the battering portion 110b of the plurality of second battering portions 110b is directly below a portion of one battering portion 110a of the plurality of first battering portions 110a and directly above a portion of another battering portion 110a of the plurality of first battering portions 110a in the first direction x. In some examples, the nanobubble generator 100 comprises a plurality of output portions 116, for example the nanobubble generator 100 may comprise a first output portion and a second output portion. In some such examples, the first output portion and the second output portion overlap such that a portion of the second output portion is directly below a portion of the first output portion in the first direction. In other examples, there is no overlap between the first output portion and the second output portion. In some examples, there may be overlap between two or more of: the at least one propeller; the at least one battering portion; and the at least one output portion. In some examples, the nanobubble generator 100 comprises a plurality of outlets 120, for example the nanobubble generator 100 may comprise a first outlet and a second outlet. In other examples the nanobubble generator 100 comprises one outlet 120. In examples, the nanobubble generator 100 comprises a plurality of rods 114, for example the nanobubble generator 100 may comprise a first rod 114a and a second rod 114b. In examples, the at least one first propeller 108a and at least one first battering portion 108b are connected to a first rod 114a, wherein the first rod 114a extends along the first central axis A1 and is configured to rotate and cause rotation of the at least one first propeller 108a and the at least one first battering portion 110a. In examples, the at least one second propeller 108b and at least one second battering portion 110b are connected to a second rod 114b, wherein the second rod 114b extends along the second central axis A2 and is configured to rotate and cause rotation of the at least one second propeller 108b and the at least one second battering portion 110b. In some examples, the container 102 comprises two connected cylinders, each having a diameter sized to allow rotation of the propeller(s) 108 and the battering portion(s) 110. FIG 6B illustrates a top view of the container 102 in some such examples. In examples, the nanobubble generator 100 comprises a plurality of inlets 106, for example the nanobubble generator 100 may comprise a first inlet and a second inlet. In examples, the nanobubble generator 100 comprises a plurality of pumps 118, for example the nanobubble generator 100 may comprise a first pump and a second pump. In examples, the nanobubble generator 100 comprises a plurality of motors 122, wherein each motor 122 is configured to rotate a rod 114 of the plurality of rods 114. In other examples, the nanobubble generator 100 comprises one pump 118 and / or one motor 122. In the example of FIGs 6A and 6B, two central axes A1, A2 and corresponding components are illustrated, however it is to be appreciated that more than two central axes and corresponding components may be provided, or only one central axis and corresponding components may be provided. Features of the nanobubble generator 100 illustrated in FIG 6A and 6B may be implemented as described in any of the examples set out above. FIGs 7 and 8 illustrate an example method of generating nanobubbles, the method comprising: at block 602, introducing gas from an inlet into a liquid as one or more bubbles, wherein the liquid is held by a container; at block 604, propelling the gas in a first direction, away from the inlet, using a propeller; and at block 606, battering the one or more bubbles to split the one or more bubbles into sub-bubbles using a battering portion. In some, but not necessarily all, examples, the method further comprises, at block 608, pumping the liquid into the container. In some, but not necessarily all, examples, the method further comprises, at block 610, allowing egress of liquid and sub-bubbles from the container. In some examples, the method is carried out, at least in part, by a nanobubble generator 100 as described above. The nanobubble generator 100 and associated methods disclosed above may be used in any one or more of: fisheries and aquaculture (oxygenation and aeration; water quality management; disease prevention and treatment; nutrient delivery and feeding waste management; larval rearing and hatchery operations; algae control); treatment of sewage and pollution events; agriculture (irrigation and water management; nutrient delivery; soil aeration and conditioning; seed treatment; crop protection); and drug delivery. Fig 9 illustrates an example of a controller 800 suitable for use in an apparatus 100. Implementation of a controller 800 may be as controller circuitry. The controller 800 may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware). As illustrated in Fig 9 the controller 800 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions of a computer program 806 in a general-purpose or special-purpose processor 802 that may be stored on a computer readable storage medium (disk, memory etc) to be executed by such a processor 802. The processor 802 is configured to read from and write to the memory 804. The processor 802 may also comprise an output interface via which data and / or commands are output by the processor 802 and an input interface via which data and / or commands are input to the processor 802. The memory 804 stores a computer program 806 comprising computer program instructions (computer program code) that controls the operation of the apparatus 100 when loaded into the processor 802. The computer program instructions, of the computer program 806, provide the logic and routines that enables the apparatus to perform the methods illustrated in the accompanying Figs. The processor 802 by reading the memory 804 is able to load and execute the computer program 806. The apparatus 100 comprises: at least one processor 802; and at least one memory 804 including computer program code the at least one memory 804 and the computer program code configured to, with the at least one processor 802, cause the apparatus 100 at least to perform: a method 600 of generating nanobubbles comprising: introducing 602 gas from an inlet into a liquid as one or more bubbles, wherein the liquid is held by a container; propelling 604 the gas in a first direction, away from the inlet, using a propeller; and battering 606 the one or more bubbles to split the one or more bubbles into subbubbles using a battering portion. The apparatus 100 comprises: at least one processor 802; and at least one memory 804 storing instructions that, when executed by the at least one processor 802, cause the apparatus at least to: a method 600 of generating nanobubbles comprising: introducing 602 gas from an inlet into a liquid as one or more bubbles, wherein the liquid is held by a container; propelling 604 the gas in a first direction, away from the inlet, using a propeller; and battering 606 the one or more bubbles to split the one or more bubbles into subbubbles using a battering portion. As illustrated in Fig 10, the computer program 806 may arrive at the apparatus 100 via any suitable delivery mechanism 808. The delivery mechanism 808 may be, for example, a machine readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a Compact Disc Read-Only Memory (CD-ROM) or a Digital Versatile Disc (DVD) or a solid-state memory, an article of manufacture that comprises or tangibly embodies the computer program 806. The delivery mechanism may be a signal configured to reliably transfer the computer program 806. The apparatus 100 may propagate or transmit the computer program 806 as a computer data signal. Computer program instructions for causing an apparatus to perform at least the following or for performing at least the following: a method 600 of generating nanobubbles comprising: introducing 602 gas from an inlet into a liquid as one or more bubbles, wherein the liquid is held by a container; propelling 604 the gas in a first direction, away from the inlet, using a propeller; and battering 606 the one or more bubbles to split the one or more bubbles into subbubbles using a battering portion. The computer program instructions may be comprised in a computer program, a non-transitory computer readable medium, a computer program product, a machine readable medium. In some but not necessarily all examples, the computer program instructions may be distributed over more than one computer program. Although the memory 804 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable and / or may provide permanent / semi-permanent / dynamic / cached storage. Although the processor 802 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable. The processor 802 may be a single core or multi-core processor. References to ‘computer-readable storage medium’, ‘computer program product’, ‘tangibly embodied computer program’ etc. or a ‘controller’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single / multi- processor architectures and sequential (Von Neumann) / parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc. The blocks illustrated in the accompanying Figs may represent steps in a method and / or sections of code in the computer program 806. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted. The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to “comprising only one...” or by using “consisting”. In this description, the wording 'connect', 'couple' and 'communication' and their derivatives mean operationally connected / coupled / in communication. It should be appreciated that any number or combination of intervening components can exist (including no intervening components), i.e., so as to provide direct or indirect connection / coupling / communication. Any such intervening components can include hardware and / or software components. In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’, ‘can’ or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example. Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims. Features described in the preceding description may be used in combinations other than the combinations explicitly described above. Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not. The term ‘a’, ‘an’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a / an / the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’, ‘an’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning. The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and also to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result. In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described. The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure. Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance it should be understood that the Applicant may seek protection via the claims in respect of any patentable feature or combination of features 20 hereinbefore referred to and / or shown in the drawings whether or not emphasis has been placed thereon. l / we claim: 5

Claims

1. A nanobubble generator comprising:a container, configured to hold a liquid;an inlet, configured to introduce gas into the liquid as one or more bubbles;at least one propeller configured to propel the gas in a first direction, away from the inlet; anda battering portion, configured to rotate about a central axis, the central axis extending in the first direction,wherein the battering portion is configured to batter the one or more bubbles to split the one or more bubbles into sub-bubbles.

2. A nanobubble generator as claimed in claim 1, wherein the battering portion comprises at least one battering pair, the battering pair comprising:a first paddle pair, extending along a second axis; anda second paddle pair, extending along a third axis, the third axis substantially perpendicular to the second axis.

3. A nanobubble generator as claimed in claim 2, wherein the second axis and the third axis are substantially perpendicular to the central axis.

4. A nanobubble generator as claimed in any preceding claim, wherein the propeller and the battering portion are connected to a central rod, the central rod extending along the central axis, wherein the central rod is configured to rotate and cause rotation of the propeller and the battering portion.

5. A nanobubble generator as claimed in any of claims 2 - 4, comprising an output portion comprising at least one battering pair.

6. A nanobubble generator as claimed in any preceding claim, comprising a plurality of propellers.

7. A nanobubble generator as claimed in claim 6, comprising a plurality of battering portions.

8. A nanobubble generator as claimed in claim 7, wherein each propeller is separated from another propeller by a battering portion.

9. A nanobubble generator as claimed in any of claims 6-8 when dependent on claim 5, wherein the output portion is positioned below the lowest propeller.

10. A nanobubble generator as claimed in any of claims 6-9 when dependent on claim 5, wherein the nanobubble generator comprises:four propellers;three battering portions, each battering portion comprising 20 battering pairs; and one output portion, the outlet portion comprising six battering pairs.

11. A nanobubble generator as claimed in any preceding claim wherein the container is a cylindrical container having a diameter sized to allow rotation of the propeller and the battering portion.

12. A nanobubble generator as claimed in any preceding claim comprising a pump configured to pump liquid into the container.

13. A nanobubble generator as claimed in any preceding claim comprising an outlet configured to allow egress of liquid and sub-bubbles from the container.

14. A nanobubble generator as claimed in any preceding claim, wherein the nanobubble generator is configured to be submerged in liquid.

15. A nanobubble generator as claimed in any preceding claim, wherein the battering portion is configured to batter the one or more bubbles until the one or more sub-bubbles comprise nanobubbles.

16. A nanobubble generator as claimed in any preceding claim, wherein the liquid comprises water.

17. A nanobubble generator as claimed in any preceding claim, wherein the gas comprises oxygen.

18. A method of generating nanobubbles comprising:introducing gas from an inlet into a liquid as one or more bubbles, wherein the liquid is held by a container;propelling the gas in a first direction, away from the inlet, using a propeller; and battering the one or more bubbles to split the one or more bubbles into sub-bubbles using a battering portion.

19. A method of generating nanobubbles as claimed in claim 18, further comprising pumping the liquid into the container.

20. A method of generating nanobubbles as claimed in claim 18 or 19, further comprising allowing egress of liquid and sub-bubbles from the container.

21. A method of generating nanobubbles as claimed in any of claims 18-20, wherein the method is carried out, at least in part, by the nanobubble generator of any of claims 1-17.AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS:-18 03 25CLAIMS1. A nanobubble generator comprising:a container, configured to hold a liquid;an inlet, configured to introduce gas into the liquid as one or more bubbles;5 at least one propeller configured to propel the gas in a first direction, away from the inlet; anda battering portion comprising at least one battering pair configured to rotate about a central axis, the central axis extending in the first direction, the battering pair comprising:10 a first paddle pair (302), comprising a first paddle (302a) and a second paddle(302b) extending along a second axis, at least one of the first paddle (302a) and the second paddle (304a) comprising one or more transverse through-holes (402) extending perpendicular to the second axis (B), the transverse through-holes being shaped to produce a venturi effect; and15 a second paddle pair (304), comprising a first paddle (304a) and a secondpaddle (304b) extending along a third axis, the third axis substantially perpendicular to the second axis, at least one of the first paddle (304a) and the second paddle (304b) comprising one or more transverse through-holes (402) extending perpendicular to the third axis (C), the transverse through-holes being shaped to20 produce a venturi effect;wherein the battering portion is configured to batter the one or more bubbles and to apply the venturi effect to the one or more bubbles to split the one or more bubbles into sub-bubbles.25 2. A nanobubble generator as claimed in claim 1, wherein the second axis andthe third axis are substantially perpendicular to the central axis.

3. A nanobubble generator as claimed in any preceding claim, wherein the propeller and the battering portion are connected to a central rod, the central rod30 extending along the central axis, wherein the central rod is configured to rotate and cause rotation of the propeller and the battering portion.18 03 254. A nanobubble generator as claimed in any preceding claim, comprising an output portion comprising at least one battering pair.

5. A nanobubble generator as claimed in any preceding claim, comprising a 5 plurality of propellers.

6. A nanobubble generator as claimed in claim 5, comprising a plurality of battering portions.10 7. A nanobubble generator as claimed in claim 6, wherein each propeller isseparated from another propeller by a battering portion.

8. A nanobubble generator as claimed in any of claims 5-7 when dependent on claim 5, wherein the output portion is positioned below the lowest propeller.

159. A nanobubble generator as claimed in any of claims 5-8 when dependent on claim 4, wherein the nanobubble generator comprises:four propellers;three battering portions, each battering portion comprising 20 battering pairs; and20 one output portion, the output portion comprising six battering pairs.

10. A nanobubble generator as claimed in any preceding claim wherein the container is a cylindrical container having a diameter sized to allow rotation of the propeller and the battering portion.2511. A nanobubble generator as claimed in any preceding claim comprising a pump configured to pump liquid into the container.

12. A nanobubble generator as claimed in any preceding claim comprising an 30 outlet configured to allow egress of liquid and sub-bubbles from the container.

13. A nanobubble generator as claimed in any preceding claim, wherein the nanobubble generator is configured to be submerged in liquid.18 03 2514. A nanobubble generator as claimed in any preceding claim, wherein the battering portion is configured to batter the one or more bubbles until the one or more sub-bubbles comprise nanobubbles.

515. A nanobubble generator as claimed in any preceding claim, wherein the gas comprises oxygen.

16. A method of generating nanobubbles comprising:10 introducing gas from an inlet into a liquid as one or more bubbles, wherein the liquid is held by a container;propelling the gas in a first direction, away from the inlet, using a propeller; and battering the one or more bubbles and applying the venturi effect to the one or more bubbles to split the one or more bubbles into sub-bubbles, using a battering portion, 15 the battering portion comprising at least one battering pair, configured to rotateabout a central axis, the central axis extending in the first direction, the battering pair comprising:a first paddle pair, comprising a first paddle and a second paddle extending along a second axis, at least one of the first paddle and the second paddle20 comprising one or more transverse through-holes extending perpendicular to the second axis, the transverse through-holes being shaped to produce a venturi effect; anda second paddle pair, comprising a first paddle and a second paddle extending along a third axis, the third axis substantially perpendicular to the second 25 axis, at least one of the first paddle and the second paddle comprising one or more transverse through-holes extending perpendicular to the third axis, the transverse through-holes being shaped to produce a venturi effect.

17. A method of generating nanobubbles as claimed in claim 16, further30 comprising pumping the liquid into the container.

18. A method of generating nanobubbles as claimed in claim 16 or 17, further comprising allowing egress of liquid and sub-bubbles from the container.

19. A method of generating nanobubbles as claimed in any of claims 16-18, wherein the method is carried out, at least in part, by the nanobubble generator of any of claims 1-15.

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