Micro-mixer based on standing wave vibration mode

Abstract

The invention belongs to the technical field of piezoelectric driving and microfluidics, and relates to a micro-mixer based on a standing wave vibration mode, the micro-mixer comprises a flow channel plate and a vibration assembly, the top of the vibration assembly is provided with a mixing flow channel, the mixing flow channel is used for injecting fluid, and the mixing flow channel comprises a first section, a second section, a third section, a fourth section and a fifth section which are communicated in sequence; the sections of the first section, the third section and the fifth section in the direction perpendicular to the center line are constant, the two opposite side contours of the second section are concave first arcs, and the two opposite side contours of the fourth section are convex second arcs; the first section of the mixing runner is connected with an inlet, and the fifth section is connected with an outlet; the vibration assembly comprises a piezoelectric ceramic piece arranged at the bottom of the flow channel plate, an excitation signal is input to the piezoelectric ceramic piece, the excitation signal excites the piezoelectric ceramic piece to vibrate, the piezoelectric ceramic piece drives the flow channel plate to vibrate so that fluid in the mixing flow channel can be mixed, the structure is simple, the manufacturing process is simple, energy consumption can be reduced, and implementation is easy.

Description

Technical Field

[0001] The invention belongs to the technical field of piezoelectric drive and microfluidics, and in particular relates to a micro mixer based on a standing wave vibration mode. Background Art

[0002] In recent years, micro-mixer technology is developing continuously and plays an important role in the fields of chemistry and biology, such as chemical analysis, reagent synthesis, biochemical reaction, etc. Because their size is millimeter or even micrometer, they can be used in various working occasions. The mixing efficiency of the micro-mixer is an important indicator for evaluating its performance, and will directly affect the mixing effect of the micro-mixer in practical applications.

[0003] The existing micromixer structures mainly include microchannels or microchambers, and the mixing forms are mainly divided into active and passive forms. Passive micromixers do not require external energy input, only fluid pumps and pressure drops to drive flow, and achieve mixing by changing the geometry or setting obstacles in the fluid flow path. Most active micromixers use external energy fields to affect mixing, such as electric fields, magnetic fields, thermal fields, etc.

[0004] However, the flow channel structure of passive micromixers is usually more complicated, such as fractal structure, adding baffles in straight channels, etc., which makes the micromixer more difficult to manufacture. The external energy field required by active micromixers often consumes more energy and is relatively difficult to implement. Summary of the invention

[0005] In view of this, the present invention provides a micro-mixer based on a standing wave vibration mode, which has a simple structure, a simple manufacturing process, can reduce energy consumption, and is easy to implement.

[0006] The technical solution of the present invention is: A micro mixer based on a standing wave vibration mode, comprising: A flow channel plate, the top of which is provided with a mixing flow channel, the mixing flow channel is used to inject fluid, the mixing flow channel comprises a first section, a second section, a third section, a fourth section and a fifth section which are connected in sequence, wherein the first section, the third section and the fifth section have a constant cross section along a direction perpendicular to the center line, the two opposite side profiles of the second section are both concave first arcs, and the two opposite side profiles of the fourth section are both convex second arcs; the first section of the mixing flow channel is connected to an inlet, and the fifth section is connected to an outlet; A vibration component, comprising a piezoelectric ceramic sheet, the piezoelectric ceramic sheet is arranged at the bottom of the flow channel plate, and the piezoelectric ceramic sheet is used to receive an excitation signal; An excitation signal is input to the piezoelectric ceramic sheet, the excitation signal excites the piezoelectric ceramic sheet to vibrate, and the piezoelectric ceramic sheet drives the flow channel plate to vibrate to mix the fluid in the mixing flow channel.

[0007] Preferably, the first arc and the second arc have the same arc length and curvature.

[0008] Preferably, the first arc shape or the second arc shape satisfies the following ellipse curve equation: , in, x is the horizontal coordinate value of the point on the curve in the rectangular coordinate system, y is the ordinate value of the point on the curve in the rectangular coordinate system, a is the length of the major semi-axis of the ellipse, b is the length of the minor semiaxis of the ellipse, a > b >0, and 1.5:1< a : b <2:1.

[0009] Preferably, the width of the first section, the third section and the fifth section of the mixing channel are all 1mm-5mm, 4mm<2 a <6mm,3mm<2 b <4mm.

[0010] Preferably, at least two drainage channels are provided on the flow channel plate, both of the two drainage channels are communicated with the first section of the mixing channel, and each drainage channel is correspondingly connected to an inlet.

[0011] Preferably, a cover plate is provided on the top of the flow channel plate, and a plurality of through holes are provided on the cover plate, one of which is connected to the outlet, and the other through holes are respectively connected to the corresponding inlets, and an injection needle is fixedly connected to the through hole, and the injection needle is connected to an injection hose.

[0012] Preferably, the vibration component further comprises a signal transmission plate, the signal transmission plate is fixed to the bottom of the flow channel plate, and the piezoelectric ceramic sheet is fixedly connected to the bottom of the signal transmission plate.

[0013] Preferably, the polarization direction of the piezoelectric ceramic sheet is arranged along the vertical direction.

[0014] Preferably, a base is provided at the bottom of the signal transmission plate, the base is fixedly connected to the signal transmission plate, a receiving groove is provided at the top of the base, the receiving groove is used to receive the piezoelectric ceramic sheet, and the bottom of the base is set as a plane.

[0015] Compared with the prior art, the micro mixer based on the standing wave vibration mode provided by the present invention has the following beneficial effects: By opening a mixing channel on the flow channel plate, the fluid to be mixed is transported from the inlet to the mixing channel, and a vibration component is set at the bottom of the flow channel plate. The piezoelectric ceramic piece in the vibration component is excited by the excitation signal to vibrate, thereby driving the flow channel plate to vibrate and mix the fluid in the mixing channel. In the manufacture of the micromixer, due to the relatively simple structure, the manufacturing process does not need to be very complicated, and mass production can be achieved in a short time. Compared with thermal field, magnetic field, electric field and other methods, the formation and excitation method of standing waves are easier to implement in improving the efficiency of the micromixer, which can improve the mixing efficiency of the simple structure micromixer. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0017] Figure 2 It is a structural diagram of the mixing channel of the present invention.

[0018] Figure 3 It is a cross-sectional view of the overall structure of the present invention.

[0019] Figure 4 It is a schematic diagram of the inlet and outlet positions of the present invention.

[0020] Figure 5 It is the first-order vibration mode diagram near the mixing channel in the micromixer of the present invention.

[0021] Figure 6 It is the third-order vibration mode diagram near the mixing channel in the micromixer of the present invention.

[0022] Figure 7 The maximum and minimum vibration modes of the first-order mode in the micromixer of the present invention correspond to the positions of the mixing flow channels.

[0023] Figure 8 The maximum and minimum vibration modes of the third-order mode in the micromixer of the present invention correspond to the positions of the mixing flow channels.

[0024] Description of reference numerals: 1. Injection hose; 2. Injection needle; 3. Cover plate; 4. Flow channel plate; 5. Signal transmission plate; 6. Piezoelectric ceramic sheet; 7. Base. DETAILED DESCRIPTION

[0025] It should be noted that, in the description of the present invention, the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0026] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0027] In addition, it should be noted that the connections involved in the present invention can be achieved by using conventional connection methods and do not involve any innovation.

[0028] The subject of the present invention is a micro mixer based on standing wave vibration mode. In recent years, micro mixer technology is developing continuously and plays an important role in the fields of chemistry and biology, such as chemical analysis, reagent synthesis, biochemical reaction, etc. Since their size is millimeter or even micrometer, they can be used in various working occasions. The mixing efficiency of the micro mixer is an important indicator for evaluating its performance, and will also directly affect the mixing effect of the micro mixer in practical applications.

[0029] The existing micromixer structures mainly include microchannels or microchambers, and the mixing forms are mainly divided into active and passive forms. Passive micromixers do not require external energy input, only fluid pumps and pressure drops to drive flow, and achieve mixing by changing the geometry or setting obstacles in the fluid flow path. Most active micromixers use external energy fields to affect mixing, such as electric fields, magnetic fields, thermal fields, etc.

[0030] However, the mixing channel structure of passive micromixers is usually more complicated, such as fractal structure, adding baffles in straight channels, etc., which makes the micromixer more difficult to manufacture. The external energy field required by active micromixers often consumes more energy and is relatively difficult to implement.

[0031] Based on the above reasons, the present invention provides a micro mixer based on standing wave vibration mode to solve the above mentioned technical problems. Figures 1 to 8 , the present invention is described in detail.

[0032] Example 1 The present embodiment provides a micro-mixer based on a standing wave vibration mode, as a type of active micro-mixer, including a flow channel plate 4 and a vibration component.

[0033] A mixing channel is provided at the top of the flow channel plate 4, and the mixing channel is used to inject fluid. The mixing channel includes a first section, a second section, a third section, a fourth section and a fifth section which are connected in sequence, wherein the first section, the third section and the fifth section have a constant cross section along a direction perpendicular to the center line, and the two opposite side profiles of the second section are both concave first arcs, and the two opposite side profiles of the fourth section are both convex second arcs; the first section of the mixing channel is connected with an inlet, and the fifth section is connected with an outlet; the vibration component includes a piezoelectric ceramic sheet 6, which is arranged at the bottom of the flow channel plate 4, and the piezoelectric ceramic sheet 6 is used to receive an excitation signal; an excitation signal is input to the piezoelectric ceramic sheet 6, and the excitation signal excites the piezoelectric ceramic sheet 6 to vibrate, and the piezoelectric ceramic sheet 6 drives the flow channel plate 4 to vibrate to mix the fluid in the mixing channel. The standing wave signal applied at the selected frequency and input voltage peak can excite the micro-mixer device to generate vibration, thereby disturbing the fluid in the mixing channel, further enhancing the fluid mixing, and improving the mixing efficiency.

[0034] Standing waves are a kind of inverse piezoelectric effect that drives the substrate to produce certain vibrations. Micromixers use the force between two different fluid molecules or the reaction between fluids to mix. Due to the addition of standing wave signals, the fluid can be disturbed, realizing a new type of active micromixer that can enhance the mixing effect. It can be adjusted and optimized according to different process requirements and fluid characteristics, and respond quickly to changes in external inputs. The microchannel size is easy to process and is relatively easy to implement. As a new type of active micromixer, it has become a hot topic for many scholars at home and abroad to continue research, and it also has great development potential and a very broad application prospect.

[0035] By opening a mixing channel on the flow channel plate, the fluid to be mixed is transported from the inlet to the mixing channel, and a vibration component is set at the bottom of the flow channel plate. The piezoelectric ceramic piece in the vibration component is excited by the excitation signal to generate vibration, thereby driving the flow channel plate to vibrate and mix the fluid in the mixing channel. In terms of the manufacture of the micro mixer, the structure of the present invention is relatively simple, and the manufacturing process does not need to be very complicated, and mass production can be achieved in a short time. Compared with thermal field, magnetic field, electric field and other methods, the formation and excitation method of standing waves are easier to implement in improving the efficiency of the micro mixer, and can improve the mixing efficiency of the simple structure micro mixer.

[0036] In this embodiment, the arc length and curvature of the first arc and the second arc are the same, the first arc or the second arc is a segment of an ellipse, and the major axis of the ellipse is parallel to the center line of the first segment of the mixing channel.

[0037] The first arc or the second arc satisfies the following ellipse curve equation: , in, xis the horizontal coordinate value of the point on the curve in the rectangular coordinate system, y is the ordinate value of the point on the curve in the rectangular coordinate system, a is the length of the major semi-axis of the ellipse, b is the length of the minor semiaxis of the ellipse, a > b >0, and 1.5:1< a : b <2:1.

[0038] The second and fourth sections of the mixing channel form an "expanding-ellipse structure", the second section is called the "expanding-ellipse" structure, and the fourth section is called the "shrinking-ellipse" structure. Different from the traditional serpentine and straight channel structures, this structure optimizes fluid dynamics and uses vibration to change the distribution of the liquid therein, effectively changing the flow direction of the fluid, and can generate more shear force under the action of vibration. Since the flow rate of the fluid is different in different directions, this asymmetric flow can promote laminar flow of the fluid, increase the contact area between different liquid phases, and form an asymmetric flow pattern of the fluid in the channel, thereby improving the mixing uniformity, reducing energy consumption, and improving the mixing efficiency within a certain period of time.

[0039] In this embodiment, the cross-sections of the first, third and fifth sections of the mixing channel are equal. The width of the first, third or fifth section should generally range from 1 mm to 5 mm. In this embodiment, 3 mm is selected to meet the size requirements of the micro-mixer in design and is also easy to process. The flow channel plate is a PMMA plate with a thickness of 1 mm. This size ratio can make the Reynolds number of the fluid only related to the injection speed. Usually, the ratio of the major axis to the minor axis should be between 1.5:1 and 2:1. According to the set width of the mixing channel, the major axis of the ellipse can be set to 4 mm to 6 mm, and the minor axis to 3 mm to 4 mm. This can ensure the stability of the flow of the fluid in the channel and achieve a better mixing effect, and also make the flow of the fluid in the channel not too compact. In this embodiment, the major axis of the ellipse is set to 2 a 6mm, the minor axis of the ellipse is 2 b is 4mm.

[0040] The mixing channel is set as a "scaled elliptical structure" to provide appropriate flow space for the fluid, so that the elliptical structure can achieve further mixing of the fluid without causing excessive energy loss. When the fluid flows through the elliptical channel, as the vibration is applied, the fluid flow may change along the direction and lateral direction of the flow, thereby accelerating the mixing. And the influence of vibration can be studied more specifically in a certain area.

[0041] Embodiments of the present invention Figure 3The figure is a cross-sectional view of the entire micro-mixer device after assembly, and the signal excitation condition. In the cross-sectional view, the blank part represents the mixing channel, and the arrow lines in the mixing channel represent the fluid in the mixing channel, which is affected by the vibration of the piezoelectric ceramic sheet 5, and has a certain influence on the flow direction of the fluid, thereby promoting the mixing of the fluid.

[0042] Figure 5 , Figure 6 This is the vibration mode diagram near the mixing channel in this embodiment. This measurement range corresponds to Figure 2 The derived size range is the rectangular area where the mixing channel c*d in the figure is located. The preferred size of c*d is 25mm×9mm. It is mainly the first-order and third-order vibration modes. These two standard modes are selected for ease of measurement and analysis. In the vertical direction, according to a certain period of vibration, two standard standing wave modes are formed at different frequencies.

[0043] Figure 7 , 8 In this embodiment, the maximum and minimum amplitude positions corresponding to the mixing flow channel under the first-order and third-order standing wave modes selected are shown. In the curve, the maximum amplitude is represented by Amax and the minimum amplitude is represented by Amin. The figure next to the curve shows the mixing flow channel position corresponding to the maximum amplitude position and the minimum amplitude position, further showing the first-order and third-order vibrations generated near the mixing flow channel.

[0044] The usage and working principle of this embodiment In this specific embodiment, the standing wave signal is abbreviated as Asin(ωt+ϕ), and the signal is input to the piezoelectric ceramic sheet 6. Since only one standing wave signal is used, the phase ϕ does not need to be considered in this example. A in this embodiment is set to 60V, that is, the peak value of the input voltage; ω is related to the frequency, and driven by the piezoelectric ceramic sheet 6, the fluid in the mixing channel can also vibrate.

[0045] The mixing channel of the embodiment of the present invention is set as a "scaled elliptical structure". In the scaled elliptical structure, the vibration mainly disturbs the two fluids to promote the mixing of the fluids. The vibration not only changes the flow path of the fluid, but also changes the flow direction of the fluid by causing local vortices in the scaled elliptical structure, thereby improving the mixing efficiency.

[0046] And under different vibration orders, efficient mixing effects can be achieved at the outlet. Setting these two shapes can also reduce the resistance of the fluid, thereby reducing energy loss, especially under the high-frequency vibration of the micromixer, frequently disturbing the fluid in the mixing channel, so as to avoid the phenomenon of fluid accumulation and residue. Especially at the microscale, it can better handle high-viscosity fluids or mixing that requires fine control. When the fluid remains inside the channel, due to the influence of vibration, a certain deviation will occur, because the fluid is constantly flowing, especially for high-viscosity fluids, the phenomenon of accumulation and residue can be well improved. Moreover, the elliptical structure design is not complicated, and the smoothness of the channel can better avoid the phenomenon of fluid accumulation and residue, thereby improving the mixing efficiency.

[0047] Example 2 On the basis of the above embodiment, in this embodiment, at least two drainage channels are provided on the flow channel plate 4, both of which are connected to the first section of the mixing flow channel, and each drainage channel is connected to an inlet correspondingly, such as Figure 2 As shown, the mixing channel and the drainage channel together form a T shape.

[0048] A cover plate 3 is provided on the top of the flow channel plate 4, and a plurality of through holes are provided on the cover plate 3, one of which is connected to the outlet, and the other through holes are connected to the corresponding inlets, and an injection needle 2 is fixedly connected to the through hole, and the injection needle 2 is connected to the injection hose 1. The injection hose 1 and the injection needle 2 are used to inject fluids, and the injection needle 2 is an injection steel needle. The injection hose 1 can mainly be a transparent hose made of rubber material, one side of which is used to connect the micro mixer, and the other side can be connected to a syringe filled with liquid, and the inner diameter size can be slightly smaller than the diameter of the syringe needle.

[0049] Due to the rubber property of the hose, the diameter of the steel needle can be slightly larger than the inner diameter of the hose, so that fluid can be injected into the micro mixer, and it also plays a certain fixing role. Corresponding to the three holes on the cover plate 3, its outer diameter is just the diameter of the hole.

[0050] In this embodiment, the vibration assembly further includes a signal transmission plate 5, which is fixed to the bottom of the flow channel plate 4, and a piezoelectric ceramic sheet 6 is fixed to the bottom of the signal transmission plate 5, and the signal transmission plate 5 is used to connect the flow channel plate 4 and the piezoelectric ceramic sheet 6. Since the piezoelectric ceramic sheet 6 generates vibration, the fluid is further mixed through the signal transmission plate 5.

[0051] The flow channel plate 4 and the cover plate 3 containing the scaled elliptical structure are attached to the center of the signal transmission plate 5 , and the same piezoelectric ceramic sheet 6 is attached to the other side of the signal transmission plate 5 .

[0052] The piezoelectric ceramic sheet 6 is bonded and fixed to the signal transmission board 5 by an adhesive formed by a 1:1 mixture of epoxy resin and polyamide resin; In this embodiment, the polarization direction of the piezoelectric ceramic piece 6 is arranged along the vertical direction and is excited by a simple harmonic sinusoidal signal.

[0053] The electrodes of the piezoelectric ceramic piece 6 are distributed on the same side of the outer surface, and two wires are welded to transmit the excitation signal to the piezoelectric ceramic piece 6, driving the entire device to achieve vertical vibration.

[0054] In this embodiment, a base 7 is provided at the bottom of the signal transmission plate 5, the base 7 is fixedly connected to the signal transmission plate 5, a receiving groove is provided at the top of the base 7, the receiving groove is used to receive the piezoelectric ceramic sheet 6, and the bottom of the base 7 is set as a plane.

[0055] The base 7 is used to fix the entire micro-mixer device and provide sufficient space for the wires connecting the piezoelectric ceramic plate 6. The bottom is flat, which also keeps the entire device horizontal during operation to prevent the influence of the downward flow of the fluid due to gravity.

[0056] How to use this embodiment A layer of acrylic glue is applied on the surface of the cover plate 3 and the flow channel plate 4 with the scaling elliptical structure in advance, and they are connected accordingly. Then, UV light curing glue is applied on the other side of the flow channel plate 4 with the scaling elliptical structure to connect with the signal transmission plate 5. The UV light is used to irradiate for a certain period of time to achieve the bonding effect and achieve the effect of sealing and fixing. The surface of the base 7 is also coated with UV light curing glue, which is distributed on both sides of the signal transmission plate 5.

[0057] The overall model diagram of the entire micro-mixer device after assembly is shown in Figure 4 Given in .

[0058] The above disclosure is only a preferred specific embodiment of the present invention, but the embodiments of the present invention are not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A micro mixer based on standing wave vibration mode, characterized in that: include: A flow channel plate (4) is provided with a mixing flow channel on the top thereof, the mixing flow channel being used to inject fluid, the mixing flow channel comprising a first section, a second section, a third section, a fourth section and a fifth section which are connected in sequence, wherein the cross-sections of the first section, the third section and the fifth section along a direction perpendicular to the center line are constant, the two opposite side profiles of the second section are both concave first arcs, and the two opposite side profiles of the fourth section are both convex second arcs; the first section of the mixing flow channel is connected to an inlet, and the fifth section is connected to an outlet; A vibration component, comprising a piezoelectric ceramic sheet (6), wherein the piezoelectric ceramic sheet (6) is arranged at the bottom of the flow channel plate (4), and the piezoelectric ceramic sheet (6) is used to receive an excitation signal; An excitation signal is input into the piezoelectric ceramic sheet (6), the excitation signal excites the piezoelectric ceramic sheet (6) to vibrate, and the piezoelectric ceramic sheet (6) drives the flow channel plate (4) to vibrate so as to mix the fluid in the mixing flow channel.

2. The micro-mixer based on the standing wave vibration mode according to claim 1, characterized in that: The first arc and the second arc have the same arc length and curvature.

3. The micro-mixer based on the standing wave vibration mode according to claim 2, characterized in that: The first arc or the second arc satisfies the curve equation of an ellipse: ， in, x is the horizontal coordinate value of the point on the curve in the rectangular coordinate system, y is the ordinate value of the point on the curve in the rectangular coordinate system, a is the length of the major semi-axis of the ellipse, b is the length of the minor semiaxis of the ellipse, a > b >0, and 1.5:1< a : b <2:

1.

4. The micro-mixer based on the standing wave vibration mode according to claim 3, characterized in that: The width of the first section, the third section and the fifth section of the mixing channel are all 1mm-5mm, 4mm<2 a <6mm,3mm<2 b <4mm.

5. The micro-mixer based on the standing wave vibration mode according to claim 1, characterized in that: The flow channel plate (4) is provided with at least two drainage channels, both of which are in communication with the first section of the mixing flow channel, and each drainage channel is correspondingly connected to an inlet.

6. The micro-mixer based on the standing wave vibration mode according to claim 5, characterized in that: A cover plate (3) is provided on the top of the flow channel plate (4), and a plurality of through holes are provided on the cover plate (3), one of the through holes is connected to the outlet, and the other through holes are respectively connected to corresponding inlets, and an injection needle (2) is fixedly connected to the through hole, and the injection needle (2) is connected to an injection hose (1).

7. The micro-mixer based on the standing wave vibration mode according to claim 1, characterized in that: The vibration component further comprises a signal transmission plate (5), wherein the signal transmission plate (5) is fixed to the bottom of the flow channel plate (4), and the piezoelectric ceramic sheet (6) is fixedly connected to the bottom of the signal transmission plate (5).

8. The micro-mixer based on the standing wave vibration mode according to claim 7, characterized in that: The polarization direction of the piezoelectric ceramic sheet (6) is arranged along the vertical direction.

9. The micro-mixer based on the standing wave vibration mode according to claim 7, characterized in that: A base (7) is provided at the bottom of the signal transmission plate (5), the base (7) being fixedly connected to the signal transmission plate (5), a receiving groove is provided at the top of the base (7), the receiving groove is used to receive the piezoelectric ceramic sheet (6), and the bottom of the base (7) is arranged to be a plane.

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