Apparatus and method for mixing two liquids or pastes

Description

[0001] The invention relates to a device for mixing two liquids or pastes, comprising a first inlet, a second inlet, a first hollow cylinder, a second hollow cylinder, a mixing element and optionally at least one central outlet. The mixing element has a mixing plate with a first and a second side and at least two partial inlets through which the first side of the mixing plate is connected to the first hollow cylinder and at least two partial inlets through which the second side of the mixing plate is connected to the second hollow cylinder. Furthermore, the first side of the mixing plate has a first outlet and the second side of the mixing plate has a second outlet, wherein the first outlet extends at least partially through the first hollow cylinder and the second outlet extends at least partially through the second hollow cylinder.Furthermore, the invention comprises a method for mixing a first and a second liquid or paste with a device according to the invention.

[0002] Devices for mixing two liquids or pastes have a wide range of applications. In fluidics, for example, liquids are transported, manipulated, and analyzed. A key process in many of these applications is the mixing of different liquids, such as solutions and analytes. Various devices, such as deflection mixing heads, linear mixing heads, or gradient mixing heads for mixing liquids, are already known from the state of the art.

[0003] DE 10 2018 104 840 A1, for example, discloses a mixer with a fluid line with a non-circular flow cross-section. Packets of the fluids to be mixed are fed sequentially into this fluid line. The mixer is designed for mixing two phases supplied from a single inlet. Furthermore, the device is specifically constructed for use in liquid chromatography. If two liquids supplied via separate inlets are to be mixed, this mixing device is not very effective.

[0004] DE 103 56 308 discloses a fluidic mixer in which a fluidic flow is branched by a flow divider element and rejoined after the flow divider element. In one embodiment, several flow divider elements are arranged one behind the other, so that the fluidic flow is repeatedly divided and rejoined. This is intended to achieve a thorough mixing of several components in the fluidic flow. The fluidic mixer according to DE 103 56 308 has a multi-stage mixing process. In such a mixing process, the starting products travel a relatively long distance during the mixing process, which results in a large dead volume in the device.After initial contact, the two phases to be mixed undergo several mixing stages. This means that a reaction between both phases begins after the first mixing stage, but the mixing phase requires a longer period of time (while passing through the subsequent mixing stages) before leaving the mixer. Applications in which the starting materials react with each other, such as crosslinking (curing), cannot be mixed in this mixer because the residence time in the mixer is longer than the reaction time for crosslinking, and the mixed phase already crosslinks or cures in the mixer.

[0005] Gradient mixing heads are used, for example, in additive manufacturing processes such as 3D printing. Common gradient mixing heads are based on the principle that starting materials, so-called precursors, are rolled between stainless steel discs, so that after several stages, the starting materials are thoroughly mixed. The effective dead volume of the mixing head, i.e., the volume from the initial contact between the two starting materials to the outlet opening after mixing, is often very large. According to manufacturers of such mixing heads, the dead volume for microfluidic applications is in the range of 950 µl.

[0006] Additive manufacturing processes are increasingly being carried out as 3D bioprinting processes. Bioprinting uses natural or synthetic materials that imitate tissue properties as closely as possible and combine cells, growth factors, and other substances. Hydrogels, for example, act as a structural component of the bio-ink and simultaneously serve as an EMC imitation to provide cells with a familiar microenvironment. The gels and bioactive additives used in bioprinting processes, such as collagen, fibronectin, and cytokines, are sometimes very cost-intensive, which is why waste in bioprinting processes should be kept as low as possible to increase the cost-effectiveness of the process. Using state-of-the-art gradient mixing heads, a volume of approximately 1000 µl remains after each 3D printing process.1 ml of waste in the gradient mixing head, which is enormous compared to the volume of structures typically printed in bioprinting processes. For example, a gel the size of a microscope slide with a height of 500 µm contains 75x25x0.5 mm 3 of bioink, roughly the same amount of waste as was produced. The impact of the dead volume becomes even more drastic when different concentrations within a gel or corresponding gradients are to be printed. Here, the dead volume, and thus the waste, accumulates with every change in the mixing ratio, meaning that in such a printing process, many times the printed structure is generated as waste. This makes state-of-the-art gradient mixing heads extremely uneconomical.

[0007] Furthermore, a small dead volume is advantageous, as it also allows two starting materials to be mixed quickly in one mixer. In particular, this allows the mixer to be used for mixing two starting materials that undergo a reaction with each other, such as crosslinking. A suitable mixer should have a dead volume that allows the starting materials to be mixed in a time that is shorter than the crosslinking time of the starting materials.

[0008] Another problem concerns the multi-part design of the gradient mixing heads from the state of the art, which on the one hand causes leakage problems and on the other hand makes cleaning the gradient mixing head more difficult.

[0009] It is the object of the present invention to eliminate the disadvantages known from the prior art and to provide a device for mixing two liquids or pastes which is characterized by particularly high economic efficiency, is particularly reliable and can be easily cleaned.

[0010] EP 1 930 070 A1 discloses a device according to the preamble of claim 1.

[0011] For this purpose, the invention provides a device for mixing two liquids or pastes, comprising a first inlet, a second inlet, a first hollow cylinder, a second hollow cylinder, a mixing element and optionally at least one central outlet, wherein the mixing element comprises a mixing plate with a first and a second side; the mixing plate has a cavity and is substantially cylindrical; the mixing element has at least two partial inlets through which the first side of the mixing plate is connected to the first hollow cylinder; the mixing element has at least two partial inlets through which the second side of the mixing plate is connected to the second hollow cylinder; the first side of the mixing plate has a first outlet and the second side of the mixing plate has a second outlet; and the first outlet extends at least partially through the first hollow cylinder and the second outlet extends at least partially through the second hollow cylinder.

[0012] The present invention further encompasses methods for mixing a first and a second liquid or paste using a device according to the invention. The method according to the invention comprises the following steps: the first liquid is supplied via the first inlet and the first hollow cylinder; the liquid flow of the first liquid is divided by the at least two partial inlets into partial flows that impinge on the first side of the mixing plate; the second liquid is supplied via the second inlet and the second hollow cylinder; the liquid flow of the second liquid is divided by the at least two partial inlets into partial flows that impinge on the second side of the mixing plate; the partial flows of the first liquid flow and the partial flows of the second liquid flow meet in the mixing plate, mix, and form a liquid mixture; a first part of the liquid mixture is discharged from the mixing plate through the first outlet through the first hollow cylinder, and a second part of the liquid mixture is discharged from the mixing plate through the second outlet through the second hollow cylinder;Optionally, the first and second parts of the liquid mixture discharged from the mixing plate are combined and passed on through at least one central outlet. Detailed description

[0013] The device according to the invention is designed to mix two liquids or two pastes. Pastes are understood to be solid-liquid mixtures, i.e., suspensions with a high solids content. The use of pastes, for example, in 3D printing processes, is known to those skilled in the art. All features described below apply to the mixing of two liquids as well as to the mixing of two pastes, even if only liquids or pastes are referred to in certain circumstances.

[0014] The device according to the invention has a first inlet, a second inlet, a first hollow cylinder, a second hollow cylinder, a mixing element and optionally at least one central outlet.

[0015] A first liquid or paste is supplied to the device via the first inlet, while a second liquid or paste is supplied to the device according to the invention via the second inlet. According to the invention, the first inlet opens into the first hollow cylinder, and the second inlet opens into the second hollow cylinder.

[0016] The device according to the invention further comprises a mixing element comprising a mixing plate with a first and a second side. The mixing element further comprises at least two partial inlets through which the first side of the mixing plate is connected to the first hollow cylinder. Furthermore, the mixing plate comprises at least two partial inlets through which the second side of the mixing plate is connected to the second hollow cylinder.

[0017] According to the invention, the first side of the mixing plate is always connected to the first hollow cylinder with as many partial inlets as the second side of the mixing plate is connected to the second hollow cylinder with partial inlets.

[0018] In one embodiment of the present invention, the first side of the mixing plate is connected to the first hollow cylinder by 2 to 10, preferably by 4 to 8, particularly preferably by 6 partial inlets, and the second side of the mixing plate is connected to the second hollow cylinder by as many partial inlets as the first side of the mixing plate is connected to the first hollow cylinder by partial inlets.

[0019] Preferably, all partial inlets connected to the first hollow cylinder are mounted substantially at the edge of the first side of the mixing plate, and the partial inlets are arranged congruently with one another. Furthermore, all partial inlets connected to the second hollow cylinder are mounted substantially at the edge of the second side of the mixing plate, and the partial inlets are also arranged congruently with one another.

[0020] According to the present invention, the flow of the first liquid or paste is fed through the first hollow cylinder via the first inlet and then divided into at least two partial inlets, before impinging on the mixing plate. The same applies to the flow of the second liquid or paste. This is fed through the second hollow cylinder via the second inlet and then divided into at least two partial inlets, before impinging on the mixing plate.

[0021] Since the partial streams passing through the partial inlets are congruent with each other, the flow of liquid or paste is evenly divided due to the equivalent fluidic conditions. The more partial inlets used, the more interfaces are created between the first liquid or paste and the second liquid or paste, where diffusive mixing can occur. In a particularly preferred embodiment, the device according to the invention has 6 partial inlets connecting the first side of the mixing plate to the first hollow cylinder and 6 partial inlets connecting the second side of the mixing plate to the second hollow cylinder.

[0022] According to the invention, the at least two partial inlets connected to the first hollow cylinder and the at least two partial inlets connected to the second hollow cylinder are arranged offset from one another on the first and second sides of the mixing plate.

[0023] The offset of the at least two partial inlets connected to the first side of the mixing plate to the at least two partial inlets connected to the second side of the mixing plate is as follows: 360 ° a + b = V , wobei a... total number of partial inlets connected to the first side of the mixing plate; b... Total number of partial inlets connected to the second side of the mixing plate; V... Offset in °.

[0024] According to the invention, each partial inlet connecting the first hollow cylinder to the mixing plate is arranged offset at an angle V to at least one of the partial inlets connecting the second hollow cylinder to the mixing plate.

[0025] For example, if the first side of the mixing plate is connected to the first hollow cylinder by six partial inlets, and the second side of the mixing plate is connected to the second hollow cylinder by six partial inlets, the result is a=b=6 and thus a+b=12. The offset V is therefore calculated according to formula (1) as V=30°. The partial inlets on the first side of the mixing plate are therefore each offset by V=30° relative to the partial inlets on the second side of the mixing plate on the first side of the mixing plate.

[0026] The first liquid or paste and the second liquid or paste meet for the first time in the mixing plate. The mixing plate is essentially cylindrical. The mixing plate has a hollow space in which the partial flows of the first and second liquid or paste meet. The mixing of the first and second liquid or paste takes place in the mixing plate and the resulting material flow is then discharged bidirectionally from the mixing plate through a first and a second outlet. According to the invention, the first side of the mixing plate therefore has a first outlet and the second side of the mixing plate has a second outlet. According to the invention, the first outlet runs at least partially through the first hollow cylinder and the second outlet runs at least partially through the second hollow cylinder. For this purpose, the outlets are preferably tubular.

[0027] In a preferred embodiment, the first and second outlets are arranged substantially in the center of the first side of the mixing plate and the second side of the mixing plate, respectively.

[0028] Optionally, the device for mixing two liquids or pastes has at least one central outlet. The central outlet connects the first and second outlets and merges the material flow from the first and second outlets.

[0029] The device can be scaled to any size and thus advantageously adapted to the respective field of application. If the device is used in microfluidics, small volumes are preferably used; the aim here is primarily to achieve the smallest possible dead volume. In one embodiment of the present invention, the device advantageously has a dead volume of <900 µl, preferably <250 µl, particularly preferably <52 µl. The dead volume is thus far below that of devices known from the prior art for mixing two liquids or pastes in microfluidic applications. This makes it possible to save on starting materials by significantly reducing the waste generated during the mixing process. This increases the cost-effectiveness of the processes in which the device according to the invention for mixing two liquids or pastes is used.

[0030] If two starting products are mixed together which enter into a reaction, e.g. cross-linking, the reaction should preferably not take place in the mixing device. Starting materials whose reaction time with each other is shorter than the time required for mixing in the device according to the invention cannot therefore be mixed in a mixing device. Due to the small dead volume, the residence time in the device according to the invention for the starting products after the first encounter until the outlet of the mixture of substances is considerably shorter than in mixing devices from the prior art. As a result, the device according to the invention advantageously also extends the field of application when mixing starting products that enter into a reaction with each other.Due to the shorter residence time, starting products can be mixed together which, in a state-of-the-art mixer, would already enter into a reaction, e.g. cross-linking, within the mixer.

[0031] Scaling the dimensions of the device is possible according to the invention. The boundary conditions for scaling are determined by the viscosities of the phases to be mixed and by the resolution limits during production. In principle, when scaling the device, the number of partial inlets connecting the first side of the mixing plate to the first hollow cylinder and the number of partial inlets connecting the second side of the mixing plate to the second hollow cylinder can be kept constant (i) or adjusted to the size of the mixing plate (ii). In both cases, the diameter of the mixing plate represents the reference dimension. The individual elements of the device are identified as follows: Element of the device A Diameter of mixing plate B Thick mixing plate C Number of partial inlets through which the first side of the mixing plate is connected to the first hollow cylinder; number of partial inlets through which the second side of the mixing plate is connected to the second hollow cylinder D Diameter of the individual partial inlets E Outer diameter of the first hollow cylinder; outer diameter of the second hollow cylinder F Inner diameter of the first hollow cylinder; inner diameter of the second hollow cylinder G Diameter of first outlet; diameter of second outlet

[0032] According to the invention, the outer diameter and the inner diameter of the first and second hollow cylinders are the same. Furthermore, the diameter of the first outlet and the diameter of the second outlet are the same. i. When scaling the device while maintaining the number of partial inlets C=6, the following ratios result for the dimensioning of the individual elements of the device: B = A / 12 C = 6 D = A / 6 E = A / 3 F = A / 4 G = A / 6 ii. When scaling and adjusting the number of partial inlets, the dependencies differ from those described under i. (where A is given in mm): C = A / 1 mm D = 1 mm

[0033] According to the invention, the device is preferably designed as a single piece, which greatly simplifies cleaning of the device and avoids problems with insufficient sealing, as occur in devices known from the prior art. In a preferred embodiment, the device according to the invention is manufactured using an additive manufacturing process. Suitable additive manufacturing processes are listed in the VDI guideline VDI 3405:2014-12. The dimensions of the device according to the invention are scalable, i.e., depending on the resolution of the printing process, it can also be manufactured using any additive process such as PolyJet (PJ), Multi-Jet Fusion (MJF), Fused Deposition Modeling (FDM), Direct Laser Writing (DLW), LCD Writing (LCD), Selective Electron Beam Melting (SEBM), or Selective Laser Sintering (SLS). In a preferred embodiment, the device according to the invention is manufactured using stereolithography (SLA).

[0034] The device can be made of any material suitable for use in an additive manufacturing process. In one embodiment of the present invention, the device comprises an optically crosslinkable material from the group consisting of epoxies, acrylates, methacrylates, and urethanes. In one embodiment, the device comprises the epoxy Accura®<5530. In another embodiment of the present invention, the device comprises a non-optically crosslinkable material from the group consisting of thermoplastics and metal powders.

[0035] The invention further comprises a method for mixing a first and a second liquid or paste. All features that apply to the device according to the invention also apply to the method according to the invention, and vice versa.

[0036] The method according to the invention for mixing a first and a second liquid or paste with a device according to the invention is characterized in that the first liquid or paste is fed via the first inlet and the first hollow cylinder; the material flow of the first liquid or paste is divided by the at least two partial inlets into partial flows that meet the first side of the mixing plate; the second liquid or paste is fed via the second inlet and the second hollow cylinder; the material flow of the second liquid or paste is divided by the at least two partial inlets into partial flows that meet the second side of the mixing plate; the partial flows of the first material flow and the partial flows of the second material flow meet in the mixing plate, mix and form a material mixture; a first part of the material mixture is discharged from the mixing plate through the first outlet through the first hollow cylinder and a second part of the material mixture is discharged from the mixing plate through the second outlet through the second hollow cylinder;Optionally, the first and second parts of the mixture discharged from the mixing plate are combined and passed on through at least one central outlet.

[0037] According to the invention, in the method according to the invention, a first liquid or paste is fed via the first inlet and the first hollow cylinder, wherein the material flow of the first liquid or paste is divided by the at least two partial inlets into partial flows that impinge on the first side of the mixing plate. Correspondingly, the second liquid or paste is fed via the second inlet and the second hollow cylinder, and the material flow of the second liquid or paste is divided by the at least two partial inlets into partial flows that impinge on the second side of the mixing plate. The partial flows are congruent to one another, which is why, due to equivalent fluidic conditions, the material flow of the first liquid or paste and the material flow of the second liquid or paste are each evenly divided between the partial flows.The volume flow of the first liquid or paste at the first inlet and the volume flow of the second liquid or paste at the second inlet are preferably equal.

[0038] The partial streams of the first material stream and the partial streams of the second material stream meet in the mixing plate, mix by diffusion, and form a material mixture. A first portion of the material mixture is discharged from the mixing plate through the first outlet through the first hollow cylinder, and a second portion of the material mixture is discharged from the mixing plate through the second outlet through the second hollow cylinder.

[0039] Optionally, the first and second parts of the mixture discharged from the mixing plate are combined and passed through at least one central outlet. The central outlet may, for example, be equipped with a nozzle through which the mixture is further processed in a higher-level process.

[0040] The fact that the mixing principle can be scaled to any size and is limited only by manufacturing constraints opens up numerous fields of application for the device and method according to the invention. The miniaturization of the device makes it ideal not only for use in printing devices but also as a functional module in microfluidic on-chip applications. The device or method according to the invention can therefore be used in particular in a printing device for 3D printing, particularly extrusion-based printing processes, or as a functional module in microfluidic on-chip applications.

[0041] In the following, the present invention is explained in more detail with reference to 8 figures and 3 embodiments. Figure 1 shows an embodiment of the device according to the invention in perspective view; Figure 2 shows a front view of an embodiment of the device according to the invention; Figure 3 shows a side view of an embodiment of the device according to the invention; Figures 4(A) and (B) show two views of the embodiments; Figure 5 shows the offset between the partial inlets; Figure 6 shows a photometric measurement of liquid mixtures produced by a standard method and using a mixing device according to the invention; Figure 7 shows a gradient mixing head from the prior art.

[0042] Figure 1shows an embodiment of the device 100 according to the invention in a perspective view. The first liquid or paste is fed to the device via the first inlet 10 of the device 100 and guided through the first hollow cylinder 30 via the partial inlets 50, 51, 52 to the mixing plate 70. In this embodiment, the first hollow cylinder 30 is connected to the mixing plate 70 by six partial inlets 50-55. The second liquid or paste is fed via the second inlet 20 of the device 100 and guided through the second hollow cylinder 40 via the partial inlets 60-65 to the mixing plate 70. The second hollow cylinder 40 is connected to the mixing plate 70 by six partial inlets 60-65, just like the first hollow cylinder 30.The partial inlets 50, 51, 53, which connect the first hollow cylinder 30 to the mixing plate 70, are each arranged on the mixing plate 70 at an angle V=30° to the partial inlets 60-65, which connect the second hollow cylinder 40 to the mixing plate 70. This means that, as shown in the . Figure 1It can be seen, for example, that the partial inlet 51 is arranged offset by an angle of V=30° to the partial inlet 62. The partial inlet 50 is in turn arranged offset by 30° to the partial inlet 61. The described arrangement applies equally to all other partial inlets. In this way, each partial inlet 50, 51, 52, which connects the first hollow cylinder 30 to the mixing plate 70, is arranged offset by an angle V=30° to at least one of the partial inlets 60-65, which connects the second hollow cylinder 40 to the mixing plate 70. In the mixing plate 70, the partial streams of the first liquid or paste and the second liquid or paste meet and diffusive mixing takes place. The resulting material stream is discharged bidirectionally from the mixing plate 70 via the first outlet 80 and the second outlet 90.

[0043] The first outlet 80 extends partially through the first hollow cylinder 30, and the second outlet 90 extends partially through the second hollow cylinder 40. When the first liquid or paste is supplied via the first inlet 10, the supplied material stream flows through the first hollow cylinder 30 to the partial inlets 50, 51, 52, with the material stream flowing around the first outlet 80 in the first hollow cylinder 30. Accordingly, when the second liquid or paste is supplied via the second inlet 20, it flows through the second hollow cylinder 40 to the partial inlets 60-65, with the material stream flowing around the second outlet 90 in the second hollow cylinder 40.

[0044] In this embodiment, the first outlet 80 and the second outlet 90 are combined to form a central outlet 95. The central outlet 95 is an optional feature of the device; in other embodiments, the material flow resulting from mixing can also be discharged only via the first outlet 80 and the second outlet 90, without these outlets being combined.

[0045] Figure 2 shows a front view of the Figure 1 illustrated embodiment of the device 100. In the front view, in addition to the partial inlets 50, 51, 52, a further partial inlet 53 can be seen, which connects the first hollow cylinder 30 with the mixing plate 70. All other features are in connection with Figure 1 already described.

[0046] Figure 3 shows a side view of the Figure 11 shows the embodiment of the device 100 shown. The device 100 is shown with a view of the mixing plate 70, in which the partial inlets 60-65 can be seen, which connect the second hollow cylinder 40 to the mixing plate 70. The second inlet 20 can also be seen. The central outlet 95 is also shown in the side view. All other features of the device 100 are concealed by the mixing plate 70, the second inlet 20, and the second outlet 90.

[0047] Figure 4 (A)depicts an embodiment of the device 100 in a transparent view. The arrows indicate the course of the material flows. The addition of the first liquid or paste via the first inlet 10 is clearly visible. The first liquid or paste then flows around the first outlet 80 in the first hollow cylinder 30 and is divided into partial flows by the partial inlets 50-53. The partial inlets 50-53 open into the mixing plate 70. The second liquid or paste is correspondingly added via the second inlet 20, flows through the second hollow cylinder 40 and is also divided into partial flows by the partial inlets 60-62. In this embodiment, the first hollow cylinder 30 is connected to the mixing plate 70 by six partial inlets 50-55; similarly, the second hollow cylinder 40 is also connected to the mixing plate 70 by six partial inlets 60-62. In the view, some of the partial inlets are obscured by the visible partial inlets 50-53 and 60-62.The material flow resulting from mixing is discharged from the mixing plate 70 through the first outlet 80 and the second outlet 90. The illustration clearly shows that the first outlet 80 extends partially through the first hollow cylinder 30 and the second outlet 90 extends partially through the second hollow cylinder 40.

[0048] Figure 4 (B) represents the Figure 4 (A) illustrated embodiment in a transparent side view. In this view, the partial inlets 60-65 and 50-55 are clearly visible.

[0049] Figure 5 depicts a transparent side view of a device 100. The figure shows the partial inlets 50-55 and 60-65. The offset V between the partial inlet 65 and the partial inlet 53 is shown as an example. For the sake of clarity, the remaining partial inlets have been omitted.

[0050] Figure 6shows the results of a photometric measurement of liquid mixtures produced by a standard method and with a device 100 according to the invention.

[0051] Figure 7 represents a prior art gradient mixing head 200. Two starting products are fed via inlets 210, 220 and rolled between stainless steel discs 230, so that after several stages, the starting products are thoroughly mixed. The resulting mixture leaves the mixer through outlet opening 240. Disadvantages of these gradient mixing heads 200 have already been described above. Example 1 - Device

[0052] In one embodiment, the device had the following dimensions: Element of the device Value A Diameter of mixing plate 6 mm B Thick mixing plate 0.5 mm C Number of partial inlets through which the first side of the mixing plate is connected to the first hollow cylinder; number of partial inlets through which the second side of the mixing plate is connected to the second hollow cylinder 6 D Diameter of the individual partial inlets 1 mm E Outer diameter of the first hollow cylinder; outer diameter of the second hollow cylinder 2 mm F Inner diameter of the first hollow cylinder; inner diameter of the second hollow cylinder 1.5 mm G Diameter of first outlet; diameter of second outlet 1 mm

[0053] The first and second outlets 80, 90 were combined to form a central outlet 95. The length of the first outlet 80 and the second outlet 90 was designed such that the dead volume of the device was 51.6 µl. The residence time of liquids or pastes after initial contact in the mixing plate of the device designed in this way is sufficiently long to achieve diffuse mixing even with laminar flow, when a volume flow of 50 to 100 µl / min is applied to the central outlet 95. Example 2 - Functional test

[0054] In a functional test using the dye Rose Bengal, a standard series with distinct dye concentrations was prepared manually. Subsequently, the equivalent mixing ratios of dye and water were prepared using a device according to the invention and subsequently printed using a 3D printing device. In this embodiment, the device according to the invention was part of a 3D printing device in a 3D bioprinting process. The prepared mixtures were measured photometrically (at OD=548 nm). The results of these measurements are shown in Figure 6 As can be seen, the results of the standard series prepared manually and the concentration series generated using the device according to the invention are almost identical; the performance of the device according to the invention is excellent. The relative difference between the integrals of the linear regressions in the measurement interval is only 2.8%. Example3 - Volume flows

[0055] The diffusive mixing of a first liquid and a second liquid was tested using CFD simulation for a device with the dimensions described in Example 1. Only convective and diffusive processes were permitted as boundary conditions for heat transfer. Thermal radiation was not permitted. Water at a temperature of 1 °C was used as the first liquid, and water at a temperature of 91 °C was used as the second liquid. The volume flow at the first inlet 10 was always the same as the volume flow at the second inlet 20. Up to volume flows of < 2700 µl / min, almost complete diffusive mixing occurred in the mixing plate. Above this volume flow, incomplete mixing of the first liquid and the second liquid sometimes occurred, resulting in a concentration difference between the first and second outlets 80, 90.Due to this effect, very small inhomogeneities were formed at the central outlet 95, which, however, were less than 5% even at a volume flow 80 times higher than usual in normal operation. List of reference symbols

[0056] 10First inlet 20Second inlet 30First hollow cylinder 40Second hollow cylinder 50-55Partial inlets 60-65Partial inlets 70Mixing plate 80First outlet 90Second outlet 95Central outlet 100Device 200Gradient mixing head 210, 220Inlet 230Stainless steel disc 240Outlet opening

Claims

1. Device (100) for mixing two liquids or pastes, comprising a first inlet (10), a second inlet (20), a first hollow cylinder (30), a second hollow cylinder (40), a mixing element and optionally at least one central outlet (95), the mixing element having a mixing plate (70) with a first and a second face; the mixing plate (70) has a cavity and is substantially cylindrical; the mixing element has at least two partial inlets (50-55) via which the first face of the mixing plate (70) is connected to the first hollow cylinder (30); the mixing element has at least two partial inlets (60-65) via which the second face of the mixing plate (70) is connected to the second hollow cylinder (40); characterized in that the first face of the mixing plate has a first outlet (80) and the second face of the mixing plate has a second outlet (90); and the first outlet (80) extends at least partially through the first hollow cylinder (30) and the second outlet (90) extends at least partially through the second hollow cylinder (40).

2. Device (100) according to claim 1, characterized in that the first face of the mixing plate is connected to the first hollow cylinder (30) via 2 to 10, preferably via 4 to 8, particularly preferably via 6 partial inlets (50-55) and the second face of the mixing plate is connected to the second hollow cylinder (40) via as many partial inlets (60-65) as the first face of the mixing plate is connected to the first hollow cylinder (30) via partial inlets (50-55).

3. Device (100) according to either of the preceding claims, characterized in that all partial inlets (50-55) connected to the first hollow cylinder (30) are arranged substantially at the edge of the first face of the mixing plate (70) and the partial inlets (50-55) are congruent with one another; and in that all partial inlets (60-65) connected to the second hollow cylinder (40) are arranged substantially at the edge of the second face of the mixing plate (70) and the partial inlets (60-65) are congruent with one another.

4. Device (100) according to any of the preceding claims, characterized in that the first outlet (80) and the second outlet (90) are located substantially in the center of the first face of the mixing plate (70) and the second face of the mixing plate (70), respectively.

5. Device (100) according to any of the preceding claims, characterized in that the at least two partial inlets (50-55) connected to the first hollow cylinder (30) and the at least two partial inlets (60-65) connected to the second hollow cylinder (40) are mounted on the first and second face of the mixing plate (70) so as to be offset from one another by the angle V 360 ° a + b = V , where a... total number of partial inlets (50-55) connected to the first face of the mixing plate (70); b... total number of partial inlets (60-65) connected to the second face of the mixing plate (70); V... offset in °.

6. Device (100) according to any of the preceding claims, characterized in that the device (100) is formed in one piece.

7. Device (100) according to any of the preceding claims, characterized in that the device has a dead volume which is <900µl, preferably <250µl, particularly preferably <52µl.

8. Device (100) according to any of the preceding claims, characterized in that the device (100) is manufactured by an additive manufacturing process, in particular by stereolithography.

9. Method for mixing a first and a second liquid or paste with a device (100) according to any of claims 1 to 8, wherein • the first liquid is supplied via the first inlet (10) and the first hollow cylinder (30); • the liquid flow of the first liquid is divided by the at least two partial inlets (50-55) into partial flows which impinge on the first face of the mixing plate (70); • the second liquid is supplied via the second inlet (20) and the second hollow cylinder (40); • the liquid flow of the second liquid is divided by the at least two partial inlets (60-65) into partial flows which impinge on the second face of the mixing plate (70); • the partial flows of the first liquid flow and the partial flows of the second liquid flow meet in the mixing plate (70), mix and form a liquid mixture; • a first part of the liquid mixture is discharged from the mixing plate (70) via the first outlet (80) through the first hollow cylinder (30) and a second part of the liquid mixture is discharged from the mixing plate (70) via the second outlet (90) through the second hollow cylinder (40); • optionally, the first and second parts of the liquid mixture discharged from the mixing plate (70) are combined and passed on via at least one central outlet (95).