Microfluidic mixing

Abstract

This disclosure relates to microfluidic mixing. Aspects of the present invention relate to a microfluidic mixer, a microfluidic mixer system, a mixing method, and a method for manufacturing a microfluidic mixer.

Description

Technical Field

[0001] The present disclosure relates to microfluidic mixing. Aspects of the present invention relate to microfluidic mixers, microfluidic mixer systems, mixing methods, and methods of manufacturing microfluidic mixers.

Background Art

[0002] Microfluidic mixers use small structures and channels / ports in the micrometer-scale regime to mix fluids to produce, for example, solutions (in the case of two miscible fluids) or mixtures (in the case of immiscible fluids). Applications are wide-ranging and include, for example, molecular analysis, chemical production, and molecular biology. Microfluidic mixers have the potential to accelerate mixing processes within the millisecond to microsecond range of typical batch mixers and thus significantly below the mixing times in the second range. Faster mixing can, for example, improve the yield and byproduct profile of rapid chemical syntheses.

[0003] Due to their small scale and typically correspondingly low associated Reynolds numbers, most micromixers operate in the laminar flow regime and thus rely on diffusion as the mixing principle.

[0004] Since diffusion does not require an external energy input, mixers that rely on diffusion can potentially be more energy-efficient than turbulent mixers.

[0005] To further improve microfluidic mixers, design improvements may be required to improve at least one of mixing time, internal volume, pressure drop, and energy consumption. Often, performance improves when the structure and the size of the channels / ports can be made smaller. However, considering manufacturing solutions and quality, it may be difficult to continue reducing the size. Furthermore, increasing the volume of the mixed product generated is generally achieved by increasing the scale, which can lead to degradation in other performance areas (such as yield).

[0006] An object of the embodiments of the present invention is to mitigate at least one or more of the problems of the prior art. [Overview of the project] [Means for solving the problem]

[0007] According to a first aspect of the present invention, a microfluidic mixer is provided, which is arranged to mix a first fluid and a second fluid, comprising a mixing chamber and fluid delivery conduits, each having a fluid delivery port to the mixing chamber. The fluid delivery conduit comprises at least one first fluid delivery conduit arranged to deliver a first fluid to the mixing chamber, and at least one second fluid delivery conduit arranged to deliver a second fluid to the mixing chamber. The mixing chamber has a fluid delivery port portion having a cross-section that is at least substantially circular, and the fluid delivery conduit is arranged radially outward from the delivery port portion, such that the fluid delivery port forms a substantially continuous and substantially complete ring around the fluid delivery port portion. Furthermore, at least one first fluid delivery conduit is arranged such that the first fluid delivered by each of the first fluid delivery conduits forms a first flow in the mixing chamber, and at least one second fluid delivery conduit is arranged such that the second fluid delivered by each of the second fluid delivery conduits forms a second flow in the mixing chamber. The fluid delivery conduit is arranged so that the first and second flows converge at a substantially common convergence point inside the mixing chamber.

[0008] Adjacent fluid delivery conduits and ports surrounding the mixing chamber may mean that laminar flow is promoted (e.g., by appropriate selection of the flow rates from which the first and second fluids are delivered). In this laminar flow regime, mixing may be achieved by diffusion between the adjacent first and second flows. The convergence of the first and second flows at a common convergence point may result in hydrodynamic convergence and therefore faster mixing. The fluid delivery ports may offer several advantages because they form a substantially continuous and substantially complete ring around the fluid delivery port portion (e.g., higher-order rotational symmetry). Firstly, considering a mixing chamber from which fluid is injected from substantially all radial directions, for a given fluid delivery conduit size, there may be additional utilization / processing of fluid through the microfluidic mixer. In addition, the conditions encountered by each of the first and second flows may be substantially constant (e.g., only other adjacent flows moving toward the convergence point). The absence of rotational asymmetry may reduce or prevent asymmetric flow characteristics and / or flow rates, which may improve the mixing performance associated with the microfluidic mixer and / or reduce back pressure. The reduced pressure drop may be advantageous in that a smaller pump and / or less energy may be required. The improved mixing may provide a higher yield of the product of the mixing process using the microfluidic mixer. The mixing chamber may be, for example, substantially cylindrical in shape, but alternative configurations are also possible. For example, any shape that provides higher-order rotational symmetry resulting in a substantially circular cross-section at the fluid discharge port portion is possible (e.g., a regular octagon or a regular shape with more sides).

[0009] In some embodiments, the first and second fluids are different. They may, for example, have different chemical and / or biological properties. In addition or alternatively, the first flow and the second flow may comprise exclusively the first and second fluids, respectively, and / or may not include at least the other of the first and second fluids.

[0010] In some embodiments, a substantially common convergence point is located approximately in the center of the mixing chamber. The substantially common convergence point may be positioned, for example, on the same plane as the fluid delivery port and / or approximately equidistant from the fluid delivery port. Additionally or alternatively, the substantially common convergence point may be positioned on an axis that is substantially rotationally symmetric with respect to the mixing chamber. In this way, similar path lengths that each of the first and second flows may travel may mean that each of the first and second flows has a more consistent thickness, which may result in improved mixing and reduced pressure drop.

[0011] In some embodiments, the space inside the mixing chamber is rotationally symmetric. For example, the mixing chamber may define a continuous cavity (e.g., without an inner wall or other structure). The space inside the mixing chamber may not have radially extending walls within it. The absence of internal structure may mean that the first and second flows are not interrupted or obstructed as they mix and move to a substantially common convergence point. If radially extending walls are present, there may be "edge effects," for example, arising from the interaction between the laminar flow and the wall.

[0012] In some embodiments, the microfluidic mixer includes a fluid collection conduit having a fluid collection port, the fluid collection port located at a substantially common convergence point, and the fluid collection conduit is positioned to receive the product of the mixing of the first and second fluids in the mixing chamber. By positioning the fluid collection conduit in this manner, the first and second flows may flow substantially directly through and out of the mixing chamber (e.g., maintaining substantially straight flow paths and / or laminar flow, and substantially turbulent flow). This may reduce the pressure drop.

[0013] In some embodiments, the fluid collection port is located on the end wall of the mixing chamber, or the fluid collection conduit passes through the end wall. Thus, the fluid collection conduit may transport the mixed product away from the mixing chamber substantially axially. This may facilitate the absence of substantially radially extending fluid collection conduits, thereby preventing the formation of a substantially continuous and substantially complete ring of fluid discharge ports around the fluid discharge port portion and / or preventing the formation of substantially uninterrupted cavities inside the mixing chamber. To ensure proper recognition, the mixed product may be discharged by the fluid collection conduit to a storage section for further processing or use.

[0014] In some embodiments, the fluid collection conduit may be sized so as not to substantially introduce a pressure drop into the microfluidic mixer. This may be appropriate when the mixing is sufficiently effective within the mixing chamber so that further mixing is not necessary within the fluid collection conduit.

[0015] In some embodiments, the microfluidic mixer comprises multiple instances of a first fluid delivery conduit and a second fluid delivery conduit. As the number of fluid delivery conduits increases, the range for laminar flow contact between the instances of the first and second flows increases, and therefore diffusion mixing can increase.

[0016] In some embodiments, the microfluidic mixer is provided with sufficient fluid delivery conduits such that the fluid flows delivered by adjacent instances of those conduits are substantially parallel. For example, there may be only a small angle, or only a fraction of an angle, between the angles from which the main directions of adjacent fluid flows are delivered (a small difference in angle that provides focusing).

[0017] In some embodiments, the fluid delivery conduits are arranged to alternate circumferentially between instances of the first and second fluid delivery conduits. This may be desirable when increased mixing between the first and second fluids is desired. The fluid delivery conduits may be made to consistent dimensions to better promote consistent flow and mixing. In some embodiments, the fluid delivery ports have a width between approximately 1 and 50 micrometers. In some embodiments, the fluid delivery ports have a width between approximately 1 and 25 micrometers. In some embodiments, the fluid delivery ports have a width between approximately 1 and 10 micrometers. The width of the fluid delivery ports may be important in the performance of the microfluidic mixer, with performance improving as the width decreases.

[0018] In some embodiments, each first fluid delivery conduit connects its fluid delivery port to a first reservoir configured to house a supply of the first fluid. The microfluidic mixer may also have a first fluid inlet positioned to deliver the first fluid to the first reservoir. During use, the first fluid may be supplied to the first reservoir under pressure by a first pump. Pressure may facilitate the delivery of the first fluid to the mixing chamber through the first fluid delivery conduit. The first reservoir may be positioned to be axially displaced relative to the mixing chamber. Additionally or alternatively, the first reservoir may be positioned on the opposite side of the mixing chamber from the fluid collection conduit. This may make packaging the microfluidic mixer easier, in the sense that it may not be necessary to house both the first reservoir and the first fluid delivery to it on the side of the mixing chamber where the mixed product is collected.

[0019] In some embodiments, each second fluid delivery conduit connects its fluid delivery port to a second reservoir configured to accommodate a supply of the second fluid. The microfluidic mixer may also include a second fluid inlet positioned to deliver the second fluid to the second reservoir. During use, the second fluid may be supplied to the second reservoir under pressure by a second pump. The pressure may facilitate the delivery of the second fluid to the mixing chamber through the second fluid delivery conduit. The first and second pumps may pressurize their respective reservoirs to approximately the same pressure, thereby facilitating the delivery of the first and second fluids to the mixing chamber at approximately the same pressure. The second reservoir may be positioned to be axially displaced relative to the mixing chamber. Additionally or alternatively, the second reservoir may be positioned on the opposite side of the mixing chamber from the fluid collection conduit. This may simplify the packaging of the microfluidic mixer, in the sense that it may not be necessary to accommodate both the second reservoir and the second fluid outlet to it on the side of the mixing chamber where the mixed product is collected. The second reservoir may be located radially inward of the first reservoir. This may offer advantages in terms of reducing the length of the fluid outlet conduit and therefore the pressure drop, while still accommodating both the first and second reservoirs.

[0020] In some embodiments, each fluid delivery conduit includes a radially extending portion that extends substantially radially outward from its fluid delivery port within the mixing chamber. This may be configured so that the fluid inside the fluid delivery conduit moves substantially linearly / layered toward a substantially common convergence point when delivered through the corresponding fluid delivery port. In addition, it may allow the fluid delivery conduit to clean the mixing chamber.

[0021] In some embodiments, the radially extending portions are formed between radially extending walls, each substantially tapered to its edge in the mixing chamber. Considering that the radially extending walls are substantially tapered to a sharp edge or point, there may be virtually no gap between adjacent fluid delivery ports. This may promote proximity between the first and second flows and thus facilitate diffusion-mediated mixing in the laminar flow regime.

[0022] In some embodiments, each fluid delivery conduit comprises a radially extending portion and an axially extending portion between it and the corresponding one of the first and second reservoirs.

[0023] In some embodiments, at least a portion of the microfluidic mixer is formed by removing material from inside a substrate block. Thus, for example, one or more structures of the microfluidic mixer, such as a mixing chamber, a fluid delivery conduit, a fluid collection conduit, a first reservoir, a first fluid inlet, a second reservoir, and a second fluid inlet, may be formed in this manner.

[0024] In some embodiments, the material removal is performed by selective laser etching. Accordingly, a portion of the internal structure of the substrate block fabricated to correspond to a portion of the design of the microfluidic mixer that constitutes the voids (e.g., mixing chamber, fluid delivery conduit, fluid collection conduit, first reservoir, first fluid inlet, second reservoir, and second fluid inlet) may be irradiated around other non-void portions within the substrate block (e.g., walls of the mixing chamber, walls of the fluid delivery conduit (including walls between fluid delivery conduits), walls of the fluid collection conduit, walls of the first reservoir, walls of the first fluid inlet, walls of the second reservoir, and walls of the second fluid inlet). Subsequently, the irradiated material may be etched away (e.g., using a substance that etches the irradiated material at a faster rate than the non-irradiated material). The irradiation may be by a focused femtosecond laser. The etching may be by potassium hydroxide. The selective laser etching process may offer advantages when compared to alternatives such as two-photon polymerization and photolithography. In particular, selective laser etching may enable the fabrication of significantly finer structures and three-dimensional structures and / or may enable them to be fabricated in a more cost-effective manner. Finer structures (e.g., smaller fluid delivery port diameters) may offer improved mixing and thus yield.

[0025] In some embodiments, the substrate block comprises fused silica, glass, sapphire, or another transparent material.

[0026] When using the microfluidic mixer, the first and second fluids can be reagents, and the microfluidic mixer is used to mix them to promote a chemical reaction. Alternatively, the microfluidic mixer may be used to mix the first and second fluids (as chemical species or otherwise) to produce a mixture. In some cases, the first and second fluids may be biological materials and / or drugs. The same microfluidic mixer may be used for any such purpose in different cases.

[0027] According to a second aspect of the present invention, there is provided a microfluidic mixer system comprising a plurality of interconnected instances of the microfluidic mixer of the first aspect.

[0028] In some embodiments, the plurality of instances of the microfluidic mixer are interconnected in that their fluid collection conduits are arranged to deliver the mixed product to a common outlet. The common outlet may be, for example, a common reservoir or an inlet to a device or system for further processing or use. The plurality of instances of the microfluidic mixer may thus be considered to be arranged (e.g., connected) in parallel. Such interconnection may allow for a significant increase in the volume of the mixed product. This approach of increasing the volume may result in improved performance compared to commonly used alternatives such as enhancing the function of the microfluidic mixer (which tends to result in a loss of mixing performance). A microfluidic mixer system optionally including a common outlet may be formed by removing material from within a substrate block. This may also be achieved by selective laser etching.

[0029] In some embodiments, the plurality of instances of the microfluidic mixer and their interconnection to the common outlet are arranged such that substantially the same pressure drop occurs across the fluid flowing through each of the plurality of instances of the microfluidic mixer to the common outlet. Each of the plurality of instances of the microfluidic mixer may be substantially identical and / or have an interconnection configuration to the common outlet that is substantially the same. The plurality of instances of the microfluidic mixer may be arranged, for example, around the common outlet having interconnections of substantially the same shape and dimensions. The microfluidic mixer may be arranged, for example, equidistantly and / or symmetrically (e.g., radially outward and / or thereto in a common radial plane) around the common outlet.

[0030] In some embodiments, multiple instances of a microfluidic mixer are interconnected such that a first fluid collection conduit of the microfluidic mixer is arranged to deliver the mixed product to at least one second first fluid delivery conduit of the microfluidic mixer. This may be, for example, via a first reservoir and optionally a first fluid inlet of a second microfluidic mixer. In addition, this interconnection may be repeated further (e.g., a third, optionally fourth, and optionally subsequent, in the case of an instance of a microfluidic mixer). Multiple instances of the microfluidic mixer may therefore be considered to be arranged in series (e.g., connected). The interconnection in this manner may allow for further (and if necessary, rapid) microfluidic mixing of the mixed product from the first microfluidic mixer. An application of one embodiment of a microfluidic mixer system of this nature may be that it is desirable to mix the mixed product of the first microfluidic mixer with a third fluid (e.g., a quenching agent that (e.g., rapidly) stops a reaction initiated by mixing the first and second fluids in the first microfluidic mixer). The microfluidic mixer system may be formed by removing material from within a substrate block. This may also be achieved by selective laser etching. In some embodiments, the third fluid is different from the first and / or second fluids. They may, for example, have different chemical and / or biological properties.

[0031] In some embodiments, the series and parallel arrangements described above may be combined in any order or combination. For example, multiple instances of a microfluidic mixer may deliver the mixed product to a common outlet, which delivers the mixed product to at least one first fluid delivery conduit of another microfluidic mixer (or, in this regard, to several microfluidic mixers again connected in parallel).

[0032] A third aspect of the present invention provides a method for mixing a first fluid and a second fluid in a microfluidic manner, the method comprising delivering the first fluid in at least one first flow and the second fluid in at least one second flow from a position defining a substantially circular, substantially continuous and substantially complete ring toward a substantially common convergence point.

[0033] According to a fourth aspect of the present invention, a microfluidic mixer is provided which is formed by removing material from inside a substrate block by selective laser etching.

[0034] Selective laser etching may offer advantages in the fabrication of microfluidic mixers compared to alternatives such as photolithography. In particular, selective laser etching may enable the fabrication of remarkably fine structures and / or a more cost-effective method. Finer structures in microfluidic mixers can provide improved mixing and, consequently, yield.

[0035] Selective laser etching may be performed by irradiating the inner portions of the substrate block that constitute voids according to the microfluidic mixer design. These portions may be irradiated around other non-void portions of the design. Subsequently, the irradiated material may be etched away (for example, using a substance that etches the irradiated material at a faster rate than the non-irradiated material). Irradiation may be performed with a femtosecond laser. Etching may be performed with potassium hydroxide.

[0036] In some embodiments, the substrate block comprises glass, sapphire, or another transparent material.

[0037] In some embodiments, a microfluidic mixer is configured to mix a first fluid and a second fluid, and the microfluidic mixer comprises a mixing chamber and fluid delivery conduits, each having a fluid delivery port to the mixing chamber, the fluid delivery conduits comprising at least one first fluid delivery conduit configured to deliver the first fluid to the mixing chamber and at least one second fluid delivery conduit configured to deliver the second fluid to the mixing chamber, the at least one first fluid delivery conduit being delivered by each of the first fluid delivery conduits A first fluid is provided and arranged in the mixing chamber to form a first flow, and at least one second fluid delivery conduit is provided and arranged so that the second fluid delivered by each of the second fluid delivery conduits forms a second flow in the mixing chamber, with each first flow adjacent to at least one of the second flows or another of the first flows, and the fluid delivery conduits are provided and arranged so that the first and second flows converge to a substantially common convergence point inside the mixing chamber.

[0038] Adjacent fluid delivery conduits and ports surrounding the mixing chamber may mean that laminar flow is promoted (for example, by appropriate selection of the pressures at which the first and second fluids are delivered). In this laminar flow regime, mixing may be achieved by diffusion between the adjacent first and second flows. The convergence of the first and second flows at a common convergence point may result in hydrodynamic convergence and thus improved mixing.

[0039] In some embodiments, the mixing chamber has a fluid delivery port portion having a cross-section that is at least a substantially circular segment, where the fluid delivery conduit is arranged radially outward from the delivery port portion and the fluid delivery port is arranged around the delivery port portion. The chamber may be, for example, a substantially cylindrical segment or a substantially cylindrical shape.

[0040] In some embodiments, the mixing chamber has a fluid delivery port portion having a cross-section that is at least substantially circular, and the fluid delivery conduit is arranged radially outward from the delivery port portion, such that the fluid delivery port forms a substantially continuous and substantially complete ring around the fluid delivery port portion.

[0041] In some embodiments, a substantially common convergence point is located approximately in the center of the mixing chamber. The substantially common convergence point may be positioned, for example, on the same plane as the fluid delivery port and / or approximately equidistant from the fluid delivery port. Additionally or alternatively, the substantially common convergence point may be positioned on an axis that is substantially rotationally symmetric with respect to the mixing chamber.

[0042] In some embodiments, the space inside the mixing chamber is rotationally symmetric. For example, the mixing chamber may define a continuous cavity (e.g., without an inner wall or other structure). The space inside the mixing chamber may not have radially extending walls within it.

[0043] In some embodiments, the microfluidic mixer includes a fluid collection conduit having a fluid collection port, the fluid collection port located at a substantially common convergence point, and the fluid collection conduit is positioned to receive the product of the mixing of the first and second fluids in the mixing chamber. By positioning the fluid collection conduit in this manner, the first and second flows may flow substantially directly through and out of the mixing chamber (e.g., maintaining substantially straight flow paths and / or laminar flow, and substantially turbulent flow).

[0044] In some embodiments, the fluid collection conduit may be sized so as not to substantially introduce a pressure drop into the microfluidic mixer. This may be appropriate when the mixing is sufficiently effective within the mixing chamber so that further mixing is not necessary within the fluid collection conduit.

[0045] In some embodiments, the microfluidic mixer comprises multiple instances of a first fluid delivery conduit and a second fluid delivery conduit.

[0046] In some embodiments, the microfluidic mixer is provided with sufficient fluid delivery conduits such that the fluid flow from adjacent instances of those conduits is substantially parallel.

[0047] In some embodiments, the fluid delivery conduits are arranged to alternate circumferentially between instances of the first and second fluid delivery conduits. The fluid delivery conduits may be made to a consistent size to better promote consistent flow and mixing. In some embodiments, the fluid delivery ports have a width between approximately 1 and 50 micrometers. In some embodiments, the fluid delivery ports have a width between approximately 1 and 25 micrometers. In some embodiments, the fluid delivery ports have a width between approximately 1 and 10 micrometers. The width of the fluid delivery ports may be important in the performance of the microfluidic mixer, with performance improving as the width decreases.

[0048] In some embodiments, each first fluid delivery conduit connects its fluid delivery port to a first reservoir configured to house a supply of the first fluid. The microfluidic mixer may also have a first fluid inlet positioned to deliver the first fluid to the first reservoir. During use, the first fluid may be supplied to the first reservoir under pressure by a first pump. Pressure may facilitate the delivery of the first fluid to the mixing chamber through the first fluid delivery conduit. The first reservoir may be positioned so as to be axially displaced relative to the mixing chamber. Additionally or alternatively, the first reservoir may be positioned on the opposite side of the mixing chamber from the fluid collection conduit. This may make packaging the microfluidic mixer easier in the sense that it may not be necessary to house both the first reservoir and the first fluid delivery to it on the side of the mixing chamber where the mixing product is collected (e.g., for a substantially axial fluid collection conduit).

[0049] In some embodiments, each second fluid delivery conduit connects its fluid delivery port to a second reservoir configured to accommodate a supply of the second fluid. The microfluidic mixer may also include a second fluid inlet positioned to deliver the second fluid to the second reservoir. During use, the second fluid may be supplied to the second reservoir under pressure by a second pump. Pressure may facilitate the delivery of the second fluid to the mixing chamber through the second fluid delivery conduit. The first and second pumps may pressurize their respective reservoirs to approximately the same pressure, thereby facilitating the delivery of the first and second fluids to the mixing chamber at approximately the same pressure. The second reservoir may be positioned to be axially displaced relative to the mixing chamber. In some embodiments, the second reservoir may be positioned on the opposite side of the mixing chamber from the fluid collection conduit. This may make packaging the microfluidic mixer easier, in the sense that it may not be necessary to accommodate both the second reservoir and the second fluid outlet to it on the side of the mixing chamber where the mixed products are collected (for example, in the case of a substantially axial fluid collection conduit). The second reservoir may be located radially inward of the first reservoir. This may offer advantages in terms of reducing the length of the fluid outlet conduit and therefore the pressure drop, while still accommodating both the first and second reservoirs. In other embodiments, the second reservoir may be located on the opposite side of the mixing chamber from the first reservoir. This may make packaging the microfluidic mixer easier, in which the first and second fluid inlets are arranged to supply their respective reservoirs substantially axially from opposite sides.

[0050] In some embodiments, each fluid delivery conduit includes a radially extending portion that extends substantially radially outward from its fluid delivery port in the mixing chamber.

[0051] In some embodiments, the radially extending portions are formed between radially extending walls, each substantially tapered to its edge in the mixing chamber. Considering that the radially extending walls are substantially tapered to a sharp edge or point, there may be virtually no gap between adjacent fluid delivery ports. This may promote proximity between the first and second flows and thus facilitate diffusion-mediated mixing in the laminar flow regime.

[0052] In some embodiments, each fluid delivery conduit comprises a radially extending portion and an axially extending portion between it and the corresponding one of the first and second reservoirs.

[0053] In some embodiments, the fluid collection port is located on the end wall of the mixing chamber, or the fluid collection conduit passes through the end wall. Thus, the fluid collection conduit may transport the mixed product away from the mixing chamber in a substantially axial direction. To ensure proper recognition, the mixed product may be delivered by the fluid collection conduit to a storage unit for further processing or use.

[0054] In some embodiments, the fluid collection conduit passes through the side wall of the mixing chamber. Therefore, the fluid collection conduit may transport the mixed product away from the mixing chamber substantially radially. To ensure proper identification, the mixed product may be delivered by the fluid collection conduit to a storage unit for further processing or use.

[0055] When using a microfluidic mixer, the first and second fluids can be reagents, and the microfluidic mixer is used to mix them to facilitate a chemical reaction. Alternatively, the microfluidic mixer may be used to mix the first and second fluids (as chemical species or otherwise) to produce a mixture. In some cases, the first and second fluids may be biological materials and / or pharmaceuticals. The same microfluidic mixer may be used for any such purpose in different cases.

[0056] According to a fifth aspect of the present invention, a microfluidic mixer system is provided comprising a plurality of interconnected instances of the microfluidic mixer of the fourth aspect.

[0057] In some embodiments, multiple instances of a microfluidic mixer are interconnected in such a way that their fluid collection conduits are arranged to deliver the mixed product to a common outlet. The common outlet may be, for example, a common storage unit or an inlet to an apparatus or system for further processing or use. Multiple instances of the microfluidic mixer may therefore be considered to be arranged in parallel (e.g., connected).

[0058] In some embodiments, multiple instances of a microfluidic mixer and their interconnections to a common outlet are arranged such that substantially the same pressure drop is produced for the fluid flowing through each instance of the microfluidic mixer to the common outlet. Each instance of the microfluidic mixer may have substantially identical and / or substantially identical interconnection configurations to a common outlet. Multiple instances of the microfluidic mixer may be arranged around a common outlet, for example, having interconnections of substantially the same form and dimensions. The microfluidic mixers may be arranged, for example, at equal intervals and / or symmetrically around the common outlet (e.g., radially outside and / or thereof of a common radial plane).

[0059] In some embodiments, multiple instances of a microfluidic mixer are interconnected such that a first fluid collection conduit of the microfluidic mixer is arranged to deliver the mixing product to at least one second first fluid discharge conduit of the microfluidic mixer. This may be, for example, via a first reservoir and optionally a first fluid inlet of a second microfluidic mixer. In addition, this interconnection may be repeated further (for example, a third, optionally fourth, and optionally subsequent, in the case of an instance of a microfluidic mixer). Multiple instances of a microfluidic mixer may therefore be considered to be arranged in series (e.g., connected).

[0060] According to a sixth aspect of the present invention, a method for manufacturing a microfluidic mixer from a substrate block is provided, the method comprising forming a microfluidic mixer inside the substrate block using selective laser etching.

[0061] Selective laser etching may be performed by irradiating the inner portions of the substrate block that constitute voids according to the microfluidic mixer design. These portions may be irradiated around other non-void portions of the design. Subsequently, the irradiated material may be etched away (for example, using a substance that etches the irradiated material at a faster rate than the non-irradiated material). Irradiation may be performed with a femtosecond laser. Etching may be performed with potassium hydroxide.

[0062] In some embodiments, the substrate block comprises glass, sapphire, or another transparent material.

[0063] Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples, and alternative forms, and in particular their individual features, described in the preceding paragraphs, claims, and / or the following description and drawings, can be obtained individually or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or in any combination, provided that such features are not incompatible. The applicant reserves the right to modify the originally filed claims, including the right to modify the originally filed claims to rely on and / or incorporate any other claims, even if not initially asserted in such a manner, or to file any new claims accordingly.

[0064] One or more embodiments of the present invention are described here, for illustrative purposes only, with reference to the following accompanying drawings. [Brief explanation of the drawing]

[0065] [Figure 1] A perspective view of one embodiment of a microfluidic mixer according to one embodiment of the present invention is shown. [Figure 2] Figure 1 shows a partial perspective view of a microfluidic mixer, including a mixing chamber, according to one embodiment of the present invention. [Figure 3] Figure 1 shows an upper cross-sectional view of a portion of a microfluidic mixer, including a mixing chamber, according to one embodiment of the present invention. [Figure 4] Figure 1 shows a top cross-sectional view through a portion of a microfluidic mixer, which includes a mixing chamber with simulated fluid flow, according to one embodiment of the present invention. [Figure 5] A perspective view of one embodiment of a microfluidic mixer according to one embodiment of the present invention is shown. [Figure 6] A perspective view of a microfluidic mixer system according to one embodiment of the present invention is shown. [Figure 7] A perspective view of a microfluidic mixer system according to one embodiment of the present invention is shown. [Modes for carrying out the invention]

[0066] Referring first to Figures 1-3, the microfluidic mixer is generally shown as 1. The microfluidic mixer is formed by a series of voids etched into the substrate 3, so that the remaining substrate forms the walls and other structures of the microfluidic mixer 1. In the illustrated embodiment, the substrate is fused silica.

[0067] The microfluidic mixer 1 has a mixing chamber 5. The mixing chamber 5 is cylindrical with two end walls 7 and a side wall 9. One segment of the side wall 9 is a fluid delivery port portion 11. Radially outward from the mixing chamber 5 are a plurality of fluid delivery conduits 13. The fluid delivery conduits 13 are arranged at regular intervals and are provided around the entire fluid delivery port portion 11. Each fluid delivery conduit 13 has an axially extending portion 15 and a radially extending portion 17 between the axially extending portion 15 and the fluid delivery port portion 11. The fluid delivery conduits 13 are adjacent to each other, and each pair of radially extending portions 17 of the fluid delivery conduits 13 are separated by a thin, radially extending (common) wall 19. In the embodiments shown in Figures 1-3, 68 fluid delivery conduits 13 are provided. Nevertheless, in other embodiments, other numbers of fluid delivery conduits 13 may be used (e.g., from one to a limit defined by the manufacturing technique). The wall 19 tapers radially toward the edges 21 that extend axially in the fluid delivery port portion 11. These edges 21 define the respective fluid delivery ports 23 in the fluid delivery port portion 11. In this embodiment, the fluid delivery ports 23 are slot-shaped (i.e., axially extending slots). The width of each fluid delivery port 23 (i.e., the distance between the walls 19 in the fluid delivery ports 23) is approximately 10 micrometers. Considering the taper of the wall 19 relative to the fluid delivery port portion 11, there is virtually no gap between adjacent fluid delivery ports 23.

[0068] The fluid delivery conduit 13 is divided into approximately equal numbers of first fluid delivery conduits 25 and second fluid delivery conduits 27. These are arranged alternately in the circumferential direction around the mixing chamber 5 and are configured to deliver the first fluid and the second fluid, respectively.

[0069] The first fluid to be delivered is stored in a first reservoir 29. The first reservoir 29 is axially displaced relative to the mixing chamber 5 (in this case, above the mixing chamber 5). Each axially extending portion 15 of the instance of the first fluid delivery conduit 25 connects a corresponding instance of the radially extending portion 17 to the first reservoir 29, thus providing fluid communication between the first reservoir 29 and the mixing chamber 5. The first reservoir 29 itself is supplied with the first fluid from an external reservoir or source via a first fluid inlet 31 that extends axially. The first fluid is delivered to the first reservoir 29 under pressure by the action of a first pump (not shown).

[0070] The second fluid being delivered is stored in a second reservoir 33. The second reservoir 33 is axially displaced relative to the mixing chamber 5 (in this case, below the mixing chamber 5). Each axially extending portion 15 of the instance of the second fluid delivery conduit 27 connects the corresponding instance of the radially extending portion 17 to the second reservoir 33, thus providing fluid communication between the second reservoir 33 and the mixing chamber 5. The second reservoir 33 itself is supplied with the second fluid from an external reservoir or source via a second fluid inlet 35 that extends axially. The second fluid is delivered to the second reservoir 33 under pressure by the action of a second pump (not shown).

[0071] As can be correctly understood in accordance with the above description, in this embodiment, the first reservoir 29 and the second reservoir 33 are located on opposite sides of the mixing chamber 5 and thereby function to better accommodate the first and second fluids delivered in substantially opposite, substantially axial directions to the side corresponding to the associated reservoirs 29, 33. In addition, the axially extended portion 15 of the first fluid delivery conduit 25 protrudes in the opposite direction to the axially extended portion 15 of the second fluid delivery conduit 27.

[0072] At the center of the mixing chamber 5 are fluid collection ports 37, equidistant from each of the fluid discharge ports 23. The fluid collection ports 37 are part of a fluid collection conduit 39, which supplies the rest of the fluid. The fluid collection conduit 39 extends radially, passing through the side wall 9 of the mixing chamber 5 and beyond to reach a fluid storage section (not shown). The fluid collection conduit 39 (including the fluid collection ports 37) is sized to introduce a reduced / minimal pressure drop into the microfluidic mixer 1. It may define apertures and channels with a cross-sectional area greater than the combined cross-sectional area of ​​all the fluid discharge ports 23, for example.

[0073] The use of one embodiment of the microfluidic mixer 1 will be discussed below with further reference to Figure 4.

[0074] Under pressure from the first pump, the first fluid is delivered through the first fluid inlet 31 to the first reservoir 29 and into the first fluid delivery conduit 25. As the first fluid is pushed out from each fluid delivery port 23 of the first fluid delivery conduit 25, the first fluid is formed in each case into a laminar flow directed radially inward, each constituting an instance of the first flow 41. Each of these first flows 41 lies coplanar with the fluid delivery ports 23 and is directed toward a common convergence point 43 at the center of the mixing chamber 5.

[0075] Under pressure from the second pump, the second fluid is delivered through the second fluid inlet 35 to the second reservoir 33 and into the second fluid outlet conduit 27. As the second fluid is pushed out from each fluid outlet port 23 of the second fluid outlet conduit 27, the second fluid is formed in each case into a laminar flow directed radially inward, each constituting an instance of the second flow 45. Each of these second flows 45 is directed toward a common convergence point 43.

[0076] Adjacent instances of the first flow 41 and the second flow 45 are in close proximity and interact in a laminar flow regime, resulting in mixing of the first and second fluids through diffusion between adjacent instances of the first flow 31 and the second flow 45. Furthermore, as the first flow 31 and the second flow 45 move further radially inward toward a common convergence point 43, hydrodynamic convergence occurs, enhancing the mixing effect. In fact, in this embodiment, when the first flow 41 and the second flow 45 reach a common convergence point 43, they converge to such an extent that their width from end to end is approximately 100 nanometers.

[0077] At the common convergence point 43, the first flow 41 and the second flow 45, which are mixed there, produce a mixed product that enters the fluid collection port 37 and the fluid collection conduit 39. Considering the laminar flow regime, there is no significant turbulence or swirling; rather, the first flow 41 and the second flow 45 flow directly from their respective fluid outlet ports 23 to the common convergence point 43, into the fluid collection port 37, where they mix along the way to form the mixed product. The fluid collection conduit 39 transports the mixed product to the storage section.

[0078] Regarding the fabrication of the microfluidic mixer 1, this is done by selective laser etching inside the substrate 3. This facilitates the generation of the small scale and microstructure shown. Using selective laser etching, voids are created within the substrate 3, which correspond to the voided portions of the microfluidic mixer 1 design (e.g., the mixing chamber 5, the fluid delivery conduit 13, the fluid collection conduit 39, the first reservoir 29, the first fluid inlet 31, the second reservoir 33, and the second fluid inlet 35). The voided portions are etched around the non-voided portions of the microfluidic mixer 1 design (e.g., the walls 7 and 9 of the mixing chamber 5, the wall of the fluid delivery conduit 13 (including wall 19), the wall of the fluid collection conduit 39, the wall of the first reservoir 29, the wall of the first fluid inlet 31, the wall of the second reservoir 33, and the wall of the second fluid inlet 35). The voided portions are first irradiated around the non-voided portions of the design using a femtosecond laser. Next, potassium hydroxide is used to etch and remove the irradiated material.

[0079] Referring now to Figure 5, a microfluidic mixer 100 is provided that is somewhat reconfigured compared to microfluidic mixer 1. Here, we consider only the adjustments to microfluidic mixer 1, and all other aspects are the same as those considered above with respect to microfluidic mixer 1.

[0080] In the microfluidic mixer 100, the cylindrical mixing chamber 151 has a fluid collection port 153 in the center of the end wall 155a of the fluid mixing chamber 151. The fluid collection port 153 is part of a fluid collection conduit 155b that extends axially away from the mixing chamber 151 and leads to the rest of it. This arrangement allows the mixing chamber 151 to have an uninterrupted internal cavity. Specifically, even though there is again a common convergence point 156a at the center of the mixing chamber 151 where the fluid collection port 153 is located, the radially extending wall does not need to define the radially extending fluid collection conduit. This may help avoid the “edge effect” resulting from the interaction between the laminar flow and such wall, which could adversely affect mixing quality and / or pressure drop. Furthermore, this allows the fluid delivery conduits 156b and their associated fluid delivery ports 157 to form a substantially continuous and substantially complete ring around the fluid delivery port portion 159 around the side wall 161 of the mixing chamber 151. As a result, the fluid delivery port portion 159 and the fluid delivery conduits 156b (and in fact their fluid delivery ports 157) may be arranged rotationally symmetrically rather than as segments of the microfluidic mixer 1. This may result in additional fluid utilization / processing, improved mixing performance, and / or reduced pressure drop.

[0081] Additional adjustments are made to complement the alternative fluid collection conduit 155b. Both the first reservoir 163 and the second reservoir 165 are located on the same (in this case, upper) side of the mixing chamber 151 (i.e., displaced axially in the same direction), and the respective first and second fluids are supplied to the same side from the respective first fluid inlet 167 and second fluid inlet 169. This is the opposite side of the mixing chamber 151 from which the fluid collection port 153 is located. As a result, in this embodiment, the axially extending portions 171 of all fluid delivery conduits 173 extend in the same axial direction toward their respective corresponding first reservoir 163 and second reservoir 165.

[0082] In addition, to better accommodate the first reservoir 163 and the second reservoir 165 on the same side of the mixing chamber 151, the first chamber 163 and the second chamber 165 are displaced axially, and the second reservoir 165 has a smaller diameter than the first reservoir 163. This allows the first fluid outlet conduit 175 of the fluid outlet conduit 173 to have better access to the first reservoir 163 around the radial outer edge of the second reservoir 165. The radial portion 177 of the second fluid outlet conduit 179 of the fluid outlet conduit 173 is shortened somewhat to better allow the second fluid outlet conduit 179 to access the second reservoir 165. In addition, the first reservoir 163 has a substantially toroidal shape, thereby accommodating a second fluid inlet 169 that passes through its center to access the second reservoir 165.

[0083] Referring here to Figure 6, a microfluidic mixer system is roughly shown in 200. The microfluidic mixer system comprises multiple interconnected instances (10 instances in this case) of a microfluidic mixer 100. Each fluid collection conduit 155b of the microfluidic mixer is positioned to deliver the mixing product to a common outlet 181. In this case, the common outlet 181 is concentrated among the multiple instances of the microfluidic mixer 100. In this case, the microfluidic mixers 100 may be considered to be connected in parallel. By mixing the same fluid in each of the microfluidic mixers 100, the total volume of the resulting mixing product can be significantly higher without adjusting the characteristics (e.g., dimensions) of the microfluidic mixers.

[0084] Referring here to Figure 7, a microfluidic mixer system is roughly shown in 300. The microfluidic mixer system comprises multiple interconnected instances (in this case, two instances) of a microfluidic mixer 100. A fluid collection conduit 155b upstream 183 of the microfluidic mixer 100 is arranged to deliver its mixing product to a second fluid inlet 169 downstream 185 of the microfluidic mixer. A third fluid is supplied to a first fluid inlet 167 of the downstream 185 microfluidic mixer. In this case, the microfluidic mixers 100 may be considered connected in series, enabling continuous mixing operations.

[0085] All of the features disclosed herein (including any appended claims, abstract, and drawings), and / or all of the steps of any method or process disclosed so herein, may be combined in any combination except any combination in which at least some of such features and / or steps are mutually exclusive.

[0086] Each feature disclosed herein (including any attached claims, abstract, and drawings) may be replaced by an alternative feature serving the same, equivalent, or similar purpose, unless expressly specified otherwise. Thus, unless expressly specified otherwise, each disclosed feature is merely an example of a general set of equivalent or similar features.

[0087] The invention is not limited to the details of any of the embodiments described above. The invention extends to any novel one or any novel combination of features disclosed herein (including the appended claims, abstract, and drawings) or any novel one or any novel combination of any method or process step so as disclosed herein. The claims should not be construed as encompassing only the embodiments described above, but also any embodiments contained within the claims.

Claims

1. A microfluidic mixer (100) arranged to mix a first fluid and a second fluid, the microfluidic mixer (100) comprising a mixing chamber (151) and fluid delivery conduits (156b), each having a fluid delivery port (157) into the mixing chamber (151), The fluid delivery conduit (156b) comprises at least one first fluid delivery conduit (175) arranged to deliver the first fluid to the mixing chamber (151), and at least one second fluid delivery conduit (179) arranged to deliver the second fluid to the mixing chamber (151), The mixing chamber (151) has a fluid delivery port portion (159) having at least a substantially circular cross-section, and the fluid delivery conduit (156b) is arranged radially outward from the delivery port portion (159), and the fluid delivery port (157) is arranged such that it forms a substantially continuous and substantially complete ring around the fluid delivery port portion (159). Furthermore, the at least one first fluid delivery conduit (175) is arranged such that the first fluid delivered by each of the at least one first fluid delivery conduit (175) forms a first flow in the mixing chamber (151), and the at least one second fluid delivery conduit (179) is arranged such that the second fluid delivered by each of the at least one second fluid delivery conduit (179) forms a second flow in the mixing chamber (151), The fluid delivery conduit (156b) is arranged such that the first and second flows converge at a substantially common convergence point (156a) inside the mixing chamber (151). Microfluidic mixer (100).

2. The aforementioned substantially common focusing point (156a) is located substantially in the center of the mixing chamber (151), as described in claim 1, for the microfluidic mixer (100).

3. A microfluidic mixer (100) according to claim 1 or 2, comprising a fluid collection conduit (155b) having a fluid collection port (153), wherein the fluid collection port (153) is located at the substantially common convergence point (156a), and the fluid collection conduit (155b) is arranged to receive the product of mixing the first and second fluids in the mixing chamber (151).

4. The microfluidic mixer (100) according to claim 3, wherein the fluid collection port (153) is provided on the end wall (155a) of the mixing chamber (151), or the fluid collection conduit (153) passes through the end wall (155a).

5. Each fluid delivery conduit (156b) has a radially extending portion that extends substantially radially outward from its fluid delivery port (157) in the mixing chamber (151), and the radially extending portion is formed between radially extending walls in the mixing chamber (151) that are substantially tapered with respect to the edge, according to claim 3 or claim 4, the microfluidic mixer (100).

6. The microfluidic mixer (100) according to any one of claims 1 to 5, wherein at least a portion thereof is formed by the removal of material from inside the base material block.

7. The microfluidic mixer (100) according to claim 6, wherein the material removal is performed by selective laser etching.

8. A microfluidic mixer system (200, 300) comprising a plurality of interconnected instances of a microfluidic mixer (100) according to any one of claims 1 to 7.

9. The microfluidic mixer system (200) according to claim 8, wherein the plurality of instances of the microfluidic mixer (100) are interconnected such that their fluid collection conduits (155b) are arranged to deliver the mixed product to a common outlet (181).

10. The microfluidic mixer system (300) according to claim 8, wherein the plurality of instances of the microfluidic mixer (100) are interconnected such that the fluid collection conduit (155b) of the first (183) of the microfluidic mixer (100) is arranged to deliver the mixed product to the at least one first fluid delivery conduit of the second (185) of the microfluidic mixer.

11. A method for mixing a first fluid and a second fluid in a microfluidic manner, comprising delivering the first fluid in at least one first flow and the second fluid in at least one second flow from a position defining a substantially circular, substantially continuous and substantially complete ring toward a substantially common convergence point (156a).

12. A microfluidic mixer (1, 100) formed by the removal of material from inside a substrate block by selective laser etching.

13. The system is arranged to mix a first fluid and a second fluid, and comprises a mixing chamber (5, 151) and fluid delivery conduits (13, 156b), each having a fluid delivery port (23, 157) to the mixing chamber (5, 151), wherein the fluid delivery conduits (13, 156b) comprises at least one first fluid delivery conduit (25, 175) arranged to deliver the first fluid to the mixing chamber (5, 151) and at least one second fluid delivery conduit (27, 179) arranged to deliver the second fluid to the mixing chamber (5, 151), wherein the first fluid delivered by each of the first fluid delivery conduits (25, 175) contributes to the respective first flow (41) in the mixing chamber (5, 151). The microfluidic mixer (1,100) according to claim 12, wherein the at least one second fluid delivery conduit (27, 179) is arranged to form a first flow (41) adjacent to at least one of the second flows (45) or another of the first flows (41), and the fluid delivery conduit (13, 156b) is arranged so that the first (41) and second (45) flows converge to a substantially common convergence point (43, 156a) inside the mixing chamber (5, 151).

14. A microfluidic mixer system comprising a plurality of interconnected instances of the microfluidic mixer (1,100) according to claim 12 or claim 13.

15. A method for manufacturing a microfluidic mixer (1,100) from a substrate block, comprising forming the microfluidic mixer (1,100) inside the substrate block using selective laser etching.

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