• 专利附录
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    • 专利摘要:
    The invention describes a system (10) and method for generating monodisperse microbubbles in a co-flow configuration, wherein the system (10) comprises: a co-flow device (1) comprising an interior fluid channel (2); and at least one outer fluid channel (3), wherein the outer fluid channel (3) has a co-flow configuration with respect to the inner fluid channel (2), and wherein said outer fluid channel (3) surrounds substantially the interior fluid channel (2); and a force means (14) connected to the inner fluid channel (2) or to the outer fluid channel (3) of the co-flow device (1), wherein said force means (14) is configured to provide a variation periodically about its mean value in the flow of fluid through one of said inner channel (2) or said outer channel (3). (Machine-translation by Google Translate, not legally binding)
    公开号:ES2578283A1
    申请号:ES201630521
    申请日:2016-04-25
    公开日:2016-07-22
    发明作者:Carlos MARTÍNEZ BAZÁN；Cándido GUTIÉRREZ MONTES；Rocío BOLAÑOS JIMÉNEZ；Javier RUIZ RUS；José Ignacio JIMÉNEZ GONZÁLEZ；José Carlos CANO LOZANO；Manuel LORITE DÍEZ；Alejandro SEVILLA SANTIAGO
    申请人:Universidad Carlos III de Madrid；Universidad de Jaen；
    IPC主号:
    专利说明:

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    DESCRIPTION
    System and procedure for the generation of monodisperse microbubbles in co-flow configuration
    OBJECT OF THE INVENTION
    The present invention belongs to the field of fluid mechanics, and more particularly to the devices used for the generation of microbubbles.
    A first object of the present invention is a new system for the generation of monodisperse microbubbles in co-flow configuration that allows controlling the frequency of generation of the microbubbles by modulating the flow rate of one of the fluids.
    A second object of the present invention is a method associated with the previous system.
    BACKGROUND OF THE INVENTION
    The generation of micrometric and nanometric sized bubbles has attracted great attention in recent times because they have a large surface-volume ratio, a high solubility in an aqueous liquid, a low ascent rate [Zimmerman et al., 2013] , and a self-pressurization induced by surface tension. That is why they can improve gas exchange between the liquid and gas phases or enhance transport phenomena [Bird et al. 2007]. Likewise, microbubbles present unique and special opportunities such as being able to be photo-acoustically excited [Ashkin, 1997; Lauterborn and Kurz, 2010] or can be used as sensors or markers [Tremblay-Darveau et al., 2014]. For all the above, the application of micrometric sized bubbles is present in numerous industrial processes, such as those of biomedicine [Liu et al., 2006], food processing, gas-liquid reactors, or the generation of foams, among others, as well as in many areas of science, for example in the study of liquids with bubbles. The efficiency of the above processes depends largely on the use of bubbles of controllable sizes. However, the controlled formation of bubbles within the micrometric scales represents a very difficult goal to achieve today. At this point, the generation
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    of classical bubbles by means of gas injection through a hole or a nozzle [Davidson and Schuler, 1960, Ramakrishnan et al., 1968, Marmur and Rubin, 1970, Kumar and Kuloor, 1976, Longuet-Higgins et al. , 1991, Oguz and Prosperetti, 1993 and Bolaños-Jiménez et al., 2008] is limited to small flows and the minimum volumes attainable to the volume of Fritz (the one obtained by means of a balance between gravity and surface tension).
    Alternative techniques and devices have been proposed in recent decades, many of them based on the introduction of additional external forces to facilitate bubble shedding. MacIntyre (1967), or later other researchers such as Vejrazka et al. (2008), propose the control of the frequency and size of the bubbles through the vibration of the injector needle. In addition, Ohl (2001), and later Tomiyama et al. (2002), explored the intermittent injection of flows to control the release of bubbles. Similarly, Kariyasaki and Ousaka (2001) Sanada (2005), Najafi et al. (2008) or Shirota et al. (2008) studied the formation process by varying the feed pressure. However, the aforementioned techniques are not suitable for the mass production of microbubbles, since they are limited in bubble size and production frequency.
    On the other hand, the use of stirrers [Kawecki, 1967], hole mixers [Unno and Inoue 1980], multi-fluid mixers [Sadatomi et al. 2012] or Venturi injectors [Yin et al. 2015] provides massive productions of small bubbles. However, these techniques have drawbacks, such as the lack of generation of monodisperse bubbles, since a distribution of bubbles of different sizes is obtained, or the control of the frequency of bubbling, among others.
    Mass production of microbubbles with diameters in the range of 1 to 10 microns is also possible through insonation [Makuta et al. 2006] or mechanical agitation [J. Ellenberger and R. Krishna 2002], but these techniques provide polydisperse bubbles.
    In recent years, the production of small bubbles has been achieved through technologically advanced and sophisticated methods and devices, known as nano and microfluidic devices, whose use is based on the control of the production process they provide. At this point, the so-called T-junction devices (T junction) [P. Garstecki, et al. 2006, Fu and Ma, 2015] or flow-focusing [Gordillo et al. 2004, Gastecki et al 2004], provide bubbles
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    almost monodispersed on the order of a micrometer [Castro-Hernández et al. 2011, Kobayashi et al. 2007, Malloggi et al. 2009], However, these devices are complex and very expensive to manufacture, which limits their use. In addition, these techniques provide volume and frequency relationships that depend on the flow conditions, and independent control of the latest features is not possible. In this sense, recently, Hoeve et al. (2015), patent WO2013141695 A1, have proposed a method for producing monodisperse microbubbles of diameters of less than 10 pm. The microchannel emulsification technique [Yasuno et al. 2004] has also been studied to form microscopic gas bubbles. In addition, Stoffel et al. (2012) have recently designed and characterized a micrometric bubble generator, which allows the control of the frequency and volume of the bubble independently and produces monodisperse bubbles in a parallel channel. However, with this device the formation of monodisperse bubbles is achieved when only one channel is used, while polydispersion is observed when all the channels are used, mainly because of the coupling between the generators. In addition, these devices are also limited by the viscosity ratio of the fluids considered.
    The techniques discussed above have resulted in a significant number of patents, which have the aforementioned characteristics. For example, in the early 1990s, US005122312 (1992) proposed an injection system in the configuration of a modified bubble injector, combining the flow of liquid that provides the start of the bubbles (as in US3545731A (1970)), but that presents some drawbacks such as the coalescence of the bubbles in larger ones. Nor are these devices capable of generating a sufficient number of bubbles, nor are those generated monodispersed. In addition, the use of ultrafine or micron sized holes is required to produce microbubbles. On the other hand, US2006 / 0284325A1 (2006) proposes a microdevice based on the injection and dispersion of a gas through a porous body in a liquid, which implies the use of extremely small pores, and therefore very complicated of building In addition, control of the bubbles produced is also not possible with this method. In this sense, devices based on the technique of flow-focusing have been patented, such as in US006116516A (2000) or the most recent WO2013141695 A1, which are also considered microdevices, with their consequent constructive complexity.
    Electrolysis is used in US006689262B2 (2004), which limits working fluids and solutions, as well as prevents gas selection. In document US 7338551B2 (2008),
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    use the cavitation phenomenon to generate bubbles, but again without providing monodisperse bubbles and it is not possible to completely regulate the gas used. Finally, in US8186653B2 (2012), a small bubble generation apparatus is proposed that reduces their size by using the cut provided by a flow with rotation generated for this purpose. However, the device generates polydisperse micron sized bubbles.
    In conclusion, there is a lack of a system, different, simpler and cheaper than the use of microdevices, simple to build and capable of generating monodisperse microbubbles and that provides independent control of the volume of the bubbles and the frequency of formation.
    The use of a co-flow configuration constitutes an alternative to all the methods and techniques described above to massively generate small bubbles [Gordillo et al. 2001, Sevilla et al. 2002, Gordillo et al. 2004, Sevilla et al. 2005, Gordillo et al. 2007, Bolaños-Jiménez et al. 2011, Gutiérrez-Montes et al. 2013, Gutiérrez-Montes et al. 2014]. In addition, these types of devices are simple to build. However, the size and frequency of the bubbles are limited to a size of tens / hundreds of microns and a few hundred hertz, respectively. Likewise, individual and precise control of the volume of the bubble and the frequency of formation is not fully achieved.
    DESCRIPTION OF THE INVENTION
    The present invention solves the problems described, by allowing monodisperse microbubbles to be obtained in a much simpler way than the systems described in the prior art documents. In addition, this invention provides complete control of the formation process, which allows to independently select the frequency of generation of the microbubbles and the size of the bubbles generated. This constitutes a great advantage in relation to the systems described in the previous documents.
    In this document, the term "dispersed phase fluid" refers to the fluid supplied by the inner channel of the co-flow device, which will constitute the dispersed phase by being housed within the continuous phase fluid in the form of microbubbles, while that the term "continuous phase fluid" refers to the fluid supplied by the at least one outer channel of the co-flow device, which will constitute the continuous phase when remaining
    on the outside of the generated microbubbles.
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    In this document, the term "co-flow device" refers to a device provided with an inner fluid channel and, at least, an outer fluid channel where said channels are arranged essentially in parallel, such that at the outlet of them two streams of fluid are generated in co-flow arrangement. In this way, the inner fluid stream discharges into the outer fluid stream.
    In this document, the expression "the outer fluid channel substantially surrounds the inner fluid channel" means that the outer channel completely surrounds the entire inner channel, or that it surrounds almost all of said inner channel with the exception of some areas very small in relation to the total perimeter of the inner channel. This concept will become clearer later on from the description of the possible geometric configurations of the device of the invention.
    A first aspect of the invention is directed to a system for the generation of monodisperse microbubbles in a co-flow configuration that essentially comprises two elements:
    a) A co-flow device, which in turn comprises:
    - An inner fluid channel for a dispersed phase fluid.
    - At least one outer fluid channel for a continuous phase fluid, where the outer fluid channel has a co-flow configuration with respect to the inner fluid channel, and where said outer fluid channel substantially surrounds the inner fluid channel .
    b) A forcing means connected to the inner fluid channel or to the outer fluid channel of the co-flow device, wherein said forcing means is configured to provide a periodic variation around its average value in the fluid flow rate passing to through one of said inner channel or said outer channel.
    The inner fluid channel and the outer fluid channel of the co-flow device can be implemented by essentially thin parallel walls, as will be seen later in this document, so that the two fluids will come into contact in the
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    output end of the inner channel that stands between them. To operate this system, it is sufficient to supply a dispersed phase fluid to the co-flow fluid through the inner channel and a continuous phase fluid through at least one outer channel, applying a periodic flow variation around its mean value to one of the two fluids.
    In fact, the inventors of the present application have discovered that the addition of an oscillation in the flow rate of one of the two fluids that run respectively inside or outside the co-flow device channels, makes the interaction at the exit of the inner channel between the stream of the fluid in dispersed phase and the at least one stream of the fluid in continuous phase causes the generation of microbubbles at a frequency that coincides with the frequency of the fluctuations of the flow, and whose size depends on the flow of first fluid through the inner channel. Therefore, by controlling at least the flow rate of the first fluid passing through the inner channel and the frequency of the oscillations applied to the flow rate of one of the two fluids, the size and frequency of the microbubbles can be controlled independently.
    This contrasts with the characteristics of traditional co-flow generation methods (without forced means), where the diameter and frequency of the microbubbles is controlled through variations in the flow rates of the fluid in the continuous phase and in the dispersed phase. More specifically, in traditional generation methods, the lower the continuous phase / dispersed phase flow rate ratio, the greater the frequency of formation of the microbubbles obtained, so that the volume is determined by the relationship between the dispersed phase flow rate and the frequency of formation of the bubbles determined naturally. By incorporating into the system of the present invention a forced means to periodically modify the flow rate of one of the two fluids around a value, the appearance of additional phenomena that modify the thicknesses of the currents is induced, governing the process of formation of the microbubbles for sufficiently large modulation amplitudes. This allows to achieve that the frequency of generation of the microbubbles is that imposed by the forced means. Thanks to this, both the size of the microbubbles and their frequency of generation can be controlled independently.
    In principle, the inner fluid channel and the outer fluid channel of the co-flow device can have any geometry provided it meets the characteristics mentioned above. For example, in a preferred embodiment of the invention, the geometry of the co-flow device is chosen from the following: flat, cylindrical, annular,
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    and polyhedral.
    In this context, a flat configuration co-flow device refers in general to an essentially parallelepiped shaped co-flow device where a cross-sectional dimension of the inner and outer channels is much larger than the perpendicular dimension to the same. In a particular case of the flat configuration each cross section of the inner and outer channels is delimited by straight lines, in which case the cross section of the inner and outer channels will be rectangular in shape. However, other alternative forms of this flat configuration are possible, as will be detailed below. A cylindrical co-flow device generally refers to a co-flow device where the cross section of the inner channel is circular and the outer channel surrounds the inner channel externally. An annular configuration co-flow device generally refers to a co-flow device where the cross section of the inner channel is annular and the outer channel surrounds the inner channel internally and externally. A co-flow device of polyhedral configuration generally refers to a co-flow device where the cross-section of the inner channel is polyhedral and the outer channel surrounds the inner channel externally.
    Thus, returning to the definition of the expression "the outer fluid channel substantially surrounds the inner fluid channel", when the co-flow device of the invention has a cylindrical configuration, the outer channel completely surrounds the inner channel. Alternatively, when the co-flow device of the invention has a flat configuration, there are two outer channels of rectangular cross-section with a dimension much larger than the other that sandwich the perimeter of the cross-section of the inner fluid channel dispersed phase, whose cross section is also rectangular with a dimension much longer than the other. Therefore, in this case the two outer channels almost completely surround the inner channel except for the two side walls of the inner channel of dispersed phase fluid. The most generic case of the polyhedral configuration could combine or conform to any of the aforementioned characteristics.
    As for the exit end of the channels, according to a preferred embodiment of the invention the exit end of the inner channel has a transverse dimension of less than 1 mm and the exit end of the outer channel has a transverse dimension of less than 3 mm .
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    In this context, the term "transverse dimension" referring to the outlet end of the inner channel refers to its hydraulic diameter, in a cylindrical or similar configuration co-flow device, or to the width of its short side, in a flat configuration co-flow device. On the other hand, the "transverse dimension" referred to the outlet end of the at least one outer channel refers to the difference between its hydraulic diameter and the hydraulic diameter of the inner channel added to the thickness of the separating wall, in a device of co-flow of cylindrical configuration or similar, or to the width of the short side of one of the two channels, in a co-flow device of flat configuration. That is, for a cylindrical configuration co-flow device, the transverse dimension of the inner channel is the hydraulic diameter of the inner channel, and the transverse dimension of the outer channel is the difference between its hydraulic diameter and the hydraulic diameter of the inner channel added to the thickness of the separating wall. For a flat configuration co-flow device, the transverse dimension of the inner channel is the width of the short side of the inner channel and the transverse dimension of the outer channel is the width of the short side of one of the two outer channels.
    In another preferred embodiment of the invention, the outer fluid channel has a cross section that can be constant or decrease in the direction of the outlet end. In the case of a decrease in the cross section, which can respond to different geometries, it is intended to minimize pressure losses, guarantee stable supply conditions, as well as a profile of fluid velocities in a controlled continuous phase. For example, the cross-section may decrease in the area near the outlet end of the outer channel through a nozzle-shaped nozzle, by flat walls, or other shapes. A constant outer fluid cross section is also contemplated along the flow direction. In any case, preferably the geometry of the outer channel is symmetric with respect to the axis of the co-flow device (cylindrical or similar configuration) or central plane of the co-flow device (flat configuration).
    In another preferred embodiment of the invention, the outlet end of the outer fluid channel protrudes longitudinally relative to the outlet end of the inner fluid channel. This allows the flow direction to be improved in order to obtain a more effective effect of the modulation achieved through the forced means, which will be described later. Alternatively, the outlet end of the inner fluid channel may protrude longitudinally relative to the outlet end of the outer fluid channel or channels to favor microbubble breakage and therefore vary the frequency of formation of
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    the same.
    In addition, in another preferred embodiment of the invention the direction of the outlet end of the outer fluid channel is oriented towards the axis or plane of symmetry of the flow device. In this way, a transverse component of the fluid velocity is induced in the continuous phase and thus the breakage of the internal fluid stream in the dispersed phase in microbubbles is facilitated.
    On the other hand, in a preferred embodiment of the invention, the inner fluid channel has an essentially constant cross section. As for its length, it must be large enough to ensure complete control over the flow rate and preferential laminar regime conditions. In addition, preferably the outlet section of the inner fluid channel may have a decreasing cross-section to standardize the velocity profile of the dispersed phase fluid at the outlet of the inner channel and, thus, be able to alter the microbubble formation process.
    In yet another preferred embodiment of the invention, the walls delimiting the inner fluid channel have an outlet thickness of less than 0.5 mm. These walls can be made of any material or mixture of materials as long as the anchor point of the interphase of both fluids is perfectly controlled.
    Preferably, the profile of the wall edge of the outlet end of the inner fluid channel of the co-flow device has a shape that is chosen from: curvilinear in the exterior-interior direction, straight in the exterior-interior direction, flat, rounded and polygonal. Each of these particular forms will have a certain effect on the interphase between the inner fluid and the outer fluid, such as the variation in the amplitudes of the modulation necessary to control the process, the variation of the local thicknesses of the different currents or , in general, the conditions of the outflow and, therefore, the frequency. The latter is achieved by varying the relative position of the interphase of both fluids at the outlet. For example, in the case of a leading edge with a sharp edge, it is favored that the interphase of both fluids be fixed at the outer edge.
    Additionally, the invention contemplates the possibility that the geometry of the walls of the fluid channels presents different forms of action on the dynamics of the flow. For example, in a preferred embodiment of the invention directed to a co-flow device of flat or annular configuration, the outlet ends of the inner fluid channel and the flow channel
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    External fluid may comprise undulations configured to induce instabilities in the transverse direction that cause the current of the fluid in the dispersed phase to break in this direction. As will be seen in greater detail in the figures, these undulations can be arranged in a plane essentially parallel to the direction of the flow of the fluids, or in a plane essentially perpendicular to the direction of the flow of the fluids.
    In yet another preferred embodiment of the invention, in a co-flow device having a flat configuration the inner channel can be divided into a plurality of parallel sub-channels of fluid in dispersed phase and a plurality of parallel sub-channels of fluid in continuous phase arranged alternately. This configuration allows to considerably increase the number of bubbles generated.
    As for the forced means, in principle it can be of any type provided that it allows to periodically modify the flow rate of the fluid line in question around its average value. For example, it may be a positive displacement pump, such as a syringe pump, capable of generating a variable flow, connected to the first or second fluid line. Alternatively, a periodically variable volume container arranged in the first or second fluid line can be used. This vessel can have a movable surface whose position can be controlled through a mechanical, dynamic or acoustic actuator.
    In either case, the system may also comprise a controller connected to the forced means to allow the user to regulate the frequency and amplitude of the periodic flow variations generated.
    According to a second aspect of the invention, a method for the generation of monodisperse microbubbles in co-flow configuration is described by means of a co-flow device comprising an inner fluid channel for a dispersed phase fluid, and at least one outer fluid channel for a continuous phase fluid arranged in a co-flow configuration with respect to the inner fluid channel, where the outer fluid channel substantially surrounds the inner fluid channel. This method basically includes:
    a) Supply a first fluid to the inner fluid channel. This first fluid will be the
    dispersed phase fluid, which at the exit of the device will be locked in the
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    inside of the microbubbles.
    b) Supply a second fluid to the outer fluid channel. It is the fluid in continuous phase that will contain the microbubbles generated inside.
    c) Modify the flow rate of one of the first fluid and the second fluid so that it varies periodically around its average value.
    As described earlier in this document, the oscillation of the flow rate of one of the two fluids that run through the inner and outer channels respectively will cause the appearance of microbubbles at a frequency that coincides with the frequency of the fluctuations of the flow rate and whose size depends of the first fluid flow through the inner channel. Therefore, if the frequency of variation of the flow that varies periodically is modified, it is possible to control the frequency of generation of microbubbles. On the other hand, if the flow of the first fluid that passes through the inner channel is modified, the size of the microbubbles is controlled.
    In a preferred embodiment of the invention, the first fluid is a gas. In another preferred embodiment of the invention, the second fluid is a liquid, which may also contain a surfactant substance for the purpose of stabilizing the bubbles formed by forming a coating layer on its surface that ensures that they remain in the weather.
    BRIEF DESCRIPTION OF THE FIGURES
    Fig. 1 shows a schematic diagram of a system for the generation of monodisperse microbubbles comprising a device according to the invention.
    Figs. 2a and 2b respectively show a partial view of a co-flow device according to the invention of flat configuration and a partial view of a device according to the invention of cylindrical configuration.
    Figs. 3a, 3b and 3c respectively show a co-flow device according to the invention where the exit end of the outer channel protrudes with respect to the inner channel with constant section, a co-flow device according to the invention where the exit end of the channel exterior protrudes with respect to the interior channel with decreasing section, and a
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    co-flow device according to the invention where the inner channel protrudes with respect to the outer channel.
    Fig. 4 shows a co-flow device according to the invention where the walls of the outer channel are not parallel with respect to the central axis of the device, and therefore the flow of fluid in continuous phase has a non-zero transverse component towards the axis at the exit.
    Figs. 5a and 5b show two examples of end sections of an inner channel that have narrowings of different shapes, alternatives to the constant section.
    Fig. 6 shows different shapes of the wall profile that constitutes the exit end of the inner channel.
    Figs. 7a and 7b show a flat configuration co-flow device according to the invention whose output end of the inner and outer channels comprises oscillations respectively in a plane parallel to the current and in a plane perpendicular to the current.
    Fig. 8 shows a flat configuration co-flow device according to the invention whose inner channel is divided into a plurality of individual parallel sub-channels.
    Fig. 9 shows a graph depicting the temporary variations in pressure in the dispersed phase fluid when it is not forcedly applied.
    Fig. 10 shows a graph depicting the temporary variations in pressure in the dispersed phase fluid when forced is applied, reflecting the control of the formation frequency and the monodispersion of the bubbles produced.
    Fig. 11 shows a graph representing the temporal variations of the velocity in the continuous phase fluid produced by the force applied in Fig. 10.
    PREFERRED EMBODIMENT OF THE INVENTION
    In the following, the present invention is described in more detail with reference to the attached figures, which show several examples of constitution of the system (10) of
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    according to the present invention.
    Fig. 1 shows a schematic view of a system (10) for the generation of monodisperse microbubbles in co-flow configuration formed by a co-flow device (1) that is connected respectively to a first fluid line (12) through which a fluid that will constitute the dispersed phase, preferably a gas, flows to a second line (13) of fluid through which a fluid that will constitute the continuous phase flows. A forcing means (14) is connected to the respective fluid lines (12, 13) to cause a periodic variation of the flow rate of at least one of said fluid lines (12, 13) depending on the orders it receives from a control means (15) that is connected to it.
    The co-flow device (1) comprises an inner fluid channel (2) for the dispersed phase fluid to whose inlet the first fluid line (12) is connected and one or more external fluid channels (3) for the continuous phase fluid to which the second fluid line (13) is connected. In this specific example, it is a flat configuration co-flow device (1) where the inner fluid channel (2) has a constant cross section of essentially rectangular shape, and which comprises two outer fluid channels (3) that they also have an essentially rectangular cross section that narrows in the second half of its length as a nozzle. The two outer fluid channels (3) are arranged so as to surround almost all of the inner channel (2), which is sandwiched between them, in accordance with a flow configuration.
    When the inner and outer channels of the co-flow device (1), respectively, are supplied with fluids through the lines (12, 13), the interaction between both fluids at the outlet of the inner channel (2) ) causes the appearance of monodispersed microbubbles. To control the size of the microbubbles, it is sufficient to vary the flow rate of the fluid supplied through the first fluid line (12) corresponding to the inner channel (2), as discussed above. To further control the frequency of generation of the microbubbles, the forced means (14) apply a periodic variation of the flow rate around its average value in any of the two fluid lines (12, 13) according to a certain frequency. As a consequence, the generation of microbubbles will occur precisely at said predetermined frequency. The control means (15) acts on the forced means (14) to determine which line (12, 13) of fluid is being actuated at each moment and the characteristics of the periodic variation that is applied to it: frequency and amplitude of the oscillations.
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    Figs. 2a and 2b show two examples of geometric configuration of the co-flow device (1) of the present invention.
    Specifically, Fig. 2a shows a co-flow device (1) similar to that shown schematically in Fig. 1. It is a flat configuration device (1) where the cross-section of the inner channel (2) is essentially rectangular with a dimension much larger than another, and where there are two outer channels (3) that surround said inner channel (2) by its two long sandwich-like sides. The cross section of the inner channel (2) may decrease slightly along its length, while the cross section of the outer channels (3) undergoes a much larger decrease. In this example, the outlet ends of the inner (2) and outer (3) channels are aligned in the same plane perpendicular to the longitudinal plane of the flow device (1).
    Fig. 2b shows a cylindrical configuration co-flow device (1). The inner channel (2) has a cylindrical shape of constant section, while the outer channel (3) has a shape obtained from a revolution curve whose cross section is decreasing. As in the previous case, the inner (2) and outer (3) channels have their respective outlet ends aligned in the same plane perpendicular to the central longitudinal axis of the co-flow device (1).
    Figs. 3a and 3b show three examples of configuration of the output ends of the inner (2) and outer (3) channels. Specifically, Figs. 3a and 3b show an example of a co-flow device (1) where the exit end of the outer channel (3) protrudes longitudinally beyond the exit end of the inner channel (2) respectively without a decrease in cross-section and with a decrease in the cross section. This configuration allows more precise guidance of the fluid flow after the two fluids have come into contact. Alternatively, Fig. 3c shows another example of a co-flow device (1) where it is the inner channel outlet end (2) that protrudes longitudinally beyond the outlet end of the outer channel (3). As described above, the effects induced by this modification favor the breakage of the microbubbles and therefore modify their frequency of formation.
    Fig. 4 shows another example of configuration of the co-flow device (1) where the exit end of the outer channel (3) is inclined relative to a plane or central axis
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    longitudinal of the device (1). This causes the direction of the continuous phase fluid at the exit of the co-flow device (1) to form a certain angle of inclination in relation to the direction of the dispersed phase fluid, which coincides with the direction of said longitudinal central axis. As mentioned above, this has the effect of inducing a transverse component of the fluid velocity in the continuous phase and thus facilitating the breakage of the internal fluid stream in the dispersed phase in microbubbles.
    Figs. 5a and 5b show two examples of narrowings practiced in the end portion of the inner channel (2). The shape of the narrowing allows altering the velocity profile of the current at the output and modifying / controlling the conditions of microbubble generation.
    Fig. 6 shows different profiles of the edge of the outlet end of the inner channel (2) where the inner fluid in the dispersed phase comes into contact with the outer fluid in the continuous phase. From left to right, a curved profile in the outer-inner direction, a straight profile in the outer-inner direction, a flat profile, and a rounded profile is represented.
    Figs. 7a and 7b show another example of a flat configuration co-flow device (1) where the outlet ends of the inner channel (2) and the outer channel (3) have undulations respectively in a plane essentially parallel to the current and in a plane essentially perpendicular to the current. With this, instabilities are induced in the transverse direction that cause the breakage of the fluid stream in the dispersed phase in this direction.
    Fig. 8 shows a further example of the co-flow device (1) having a flat configuration where the inner channel (2) is subdivided into a multiplicity of individual sub-channels (2 ') of dispersed phase fluid arranged in parallel to each other along the longitudinal central plane of the co-flow device (1) which are separated from each other by means of a plurality of sub-channels (3 ') of continuous phase fluid also parallel. The inner channel (2) thus adopts the form of a row where sub-channels (2 ') of fluid in dispersed phase and sub-channels (3') of fluid in continuous phase alternate, and is also sandwiched between the two channels (3) exterior. In this co-flow device (1), each of the dispersed phase sub-channels (2 '), together with the two adjacent continuous phase sub-channels (3') and the corresponding portion of the channels (3) external walls, it constitutes a kind of individual microbubble generation sub-device, so that this co-flow device (1) as a whole allows simultaneous generation
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    in parallel of a plurality of microbubbles.
    As an example of the results achieved by the invention, Fig. 9 shows the pressure signal of the microbubbles formed in a conventional co-flow device (without forced means), in which different pressure peaks are observed within the fluid of dispersed phase that passes through the inner channel (2), which indicates the polydispersion of the formed microbubbles. Fig. 10 shows the results corresponding to the case in which the co-flow device (1) of the present document is operating with forced means, where the monodispersion is inferred from the peaks of constant amplitude pressure and formation frequency measured in the dispersed phase fluid during the microbubble formation process. Fig. 11 shows the speed modulation, in this case of the continuous phase passing through the outer channel (3), used in the case of Fig. 10.
    The tests carried out with a system (10) according to the invention of flat configuration and where the forced is carried out in the continuous phase of the outer channel (3) show increases in the frequency of microbubble formation up to values of order of kilo hertz (kHz) and reductions of dispersed phase flow of the inner channel (2) up to 20 times the values of the co-flow under natural conditions, with the consequent reduction of the size of the microbubbles generated. Likewise, the tests carried out with a system (10) according to the invention of cylindrical configuration and where the forcing is carried out in the dispersed phase of the inner channel (2) also show increases in the frequency of bubble formation up to values of order of kilo hertz (kHz)
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    权利要求:
    Claims (22)
    [1]
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    1. System (10) for the generation of monodisperse microbubbles in co-flow configuration, characterized in that it comprises:
    - a co-flow device (1) comprising:
    - a channel (2) of internal fluid for a dispersed phase fluid; Y
    - at least one outer fluid channel (3) for a continuous phase fluid, where the outer fluid channel (3) has a co-flow configuration with respect to the inner fluid channel (2), and where said channel ( 3) outer fluid substantially surrounds the inner fluid channel (2); Y
    - a forcing means (14) connected to the inner fluid channel (2) or to the outer fluid channel (3) of the co-flow device (1), wherein said forcing means (14) is configured to provide a variation periodically around its average value in the flow of fluid that passes through one of said inner channel (2) or said outer channel (3).
    [2]
    2. System (10) according to claim 1, wherein the co-flow device (1) has a geometry chosen from the following: flat, cylindrical, annular, and polyhedral.
    [3]
    3. System (10) according to any of the preceding claims, wherein the outlet end of the inner fluid channel (2) has a transverse dimension of less than 1 mm and the outlet end of the outer fluid channel (3) has a transverse dimension less than 3 mm.
    [4]
    4. System (10) according to any of the preceding claims, wherein the outer fluid channel (3) has a constant cross section or decreases in the direction of the outlet end.
    [5]
    5. System (10) according to any of the preceding claims, wherein the outlet end of the outer fluid channel (3) protrudes longitudinally relative to the outlet end of the inner fluid channel (2).
    [6]
    6. System (10) according to any of claims 1-4, wherein the outlet end of the inner fluid channel (2) protrudes longitudinally relative to the outlet end of the outer fluid channel (3).
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    [7]
    7. System (10) according to any of the preceding claims, wherein the direction of the outlet end of the external fluid channel (3) is oriented towards an axis or plane of symmetry of the co-flow device (1).
    [8]
    8. System (10) according to any of the preceding claims, wherein the inner fluid channel (2) has an essentially constant cross section.
    [9]
    9. System (10) according to any of the preceding claims, wherein the outlet section of the inner fluid channel (2) has a decreasing cross section.
    [10]
    10. System (10) according to any of the preceding claims, wherein the walls delimiting the inner fluid channel (2) have an outlet thickness of less than 0.5 mm.
    [11]
    11. System (10) according to any of the preceding claims, wherein the profile of the wall edge of the outlet end of the inner fluid channel (2) has a shape that is chosen from: curvilinear in the outer-inner direction, straight in the outer-inner direction, flat, rounded and polygonal.
    [12]
    12. System (10) according to any of the preceding claims, wherein the co-flow device (1) has a flat or annular configuration, and wherein the outlet ends of the inner fluid channel (2) and the channel ( 3) External fluid comprises undulations in a plane essentially parallel to the direction of the current.
    [13]
    13. System (10) according to any of claims 1-11, wherein the co-flow device (1) has a flat or annular configuration, and wherein the outlet ends of the inner fluid channel (2) and the External fluid channel (3) comprises undulations in a plane essentially perpendicular to the direction of the current.
    [14]
    14. System (10) according to any of the preceding claims, wherein the co-flow device (1) has a flat or annular configuration, and wherein the inner channel (2) is divided into a plurality of sub-channels ( 2 ') parallel of fluid in dispersed phase and a plurality of parallel sub-channels (3') of fluid in continuous phase arranged alternately.
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    [15]
    15. System (10) according to any of the preceding claims, wherein the forcing means (14) is chosen from: a positive displacement pump of variable flow generation connected to the first or second fluid line, and a periodically variable volume container arranged in the first or second fluid line.
    [16]
    16. System (10) according to any of the preceding claims, further comprising a controller (15) connected to the forced means to regulate the frequency and amplitude of the periodic flow variations generated.
    [17]
    17. Method for generating monodisperse microbubbles in co-flow configuration by means of a co-flow device (1) comprising an inner fluid channel (2), and at least one outer fluid channel (3) in co-flow configuration with respect to the inner fluid channel (2), wherein said outer fluid channel (3) substantially surrounds the inner fluid channel (2), characterized in that it comprises:
    - supplying a first fluid to the inner fluid channel (2);
    - supplying a second fluid to the external fluid channel (3);
    - modify the flow rate of one of the first and second fluid so that it varies periodically around its average value.
    [18]
    18. Method according to claim 17, which comprises modifying the frequency of flow variation that varies periodically to modify the frequency of microbubble generation.
    [19]
    19. Method according to any of the preceding claims, which comprises modifying the flow rate of the first fluid that passes through the inner channel (2) to modify the size of the microbubbles.
    [20]
    20. Method according to any of claims 17-19, wherein the first fluid is a gas.
    [21]
    21. Method according to any of claims 17-20, wherein the second fluid is a liquid.
    [22]
    22. Method according to claim 21, wherein the second fluid comprises a surfactant substance.
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    US7192562B1|2003-04-17|2007-03-20|Uop Llc|Hydrogen-oxygen mixer-sparger|
    US20090315203A1|2006-01-23|2009-12-24|National Cheng Kung University|Method For Producing Microparticles In A Continuous Phase Liquid|
    WO2013141695A1|2012-03-22|2013-09-26|Universiteit Twente|Apparatus and method for mass producing a monodisperse microbubble agent|
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