CN105148781B - A Cross Micromixer with Axisymmetric Logarithmic Helix - Google Patents

Abstract

The present invention discloses a kind of cross micro-mixer of axial symmetry log spiral, a cross runner, a contracted channel and several mixed cells for being sequentially connected and connecing are provided between cover plate and matrix, each mixed cell is constituted by the narrow straight channel, a log spiral runner that are connected and a log spiral baffle plate being placed in log spiral runner；Log spiral runner and log spiral baffle plate all on substantially symmetrical about its central axis, the concave surface of log spiral baffle plate face where log spiral flow channel entry point；There is gap between the edges at two ends of log spiral baffle plate and the inwall of log spiral runner；The present invention can make fluid by forming jet after narrow straight channel, and jet impulse log spiral baffle plate along log spiral baffle flows, convection current is formed with stream is carried out, increases the disturbance between fluid, so as to increase the contact area of fluid, mixed effect is significantly improved.

Description

A Cross Micromixer with Axisymmetric Logarithmic Helix

technical field

The invention relates to the technical field of liquid micro-mixing in biochips and micro-total analysis systems, in particular to a passive micro-mixer based on separation and recombination and wall attachment effects, which realizes rapid mixing of different liquids at a micro scale.

Background technique

The microfluidic system is an important part of the microelectromechanical system. The microfluidic system is an important branch of the microfluidic system, which can realize the separation, addition, mixing, reaction, monitoring and other functions of the traditional biochemical monitoring process on the chip. . As an important part of microfluidic systems, micromixers are widely used in bioanalysis, chemical synthesis, drug screening and clinical testing due to their efficient and rapid mixing performance. For the chemical reaction of two or more fluids, the problem of effective mixing between them must be solved. Since the size of the flow channel of the microfluidic chip is on the order of microns, the flow is usually in a laminar flow state, and it is difficult to mix the fluids fully. Therefore, it is very important to achieve rapid mixing of fluids at the microscale.

According to the principle of the mixing process, micro-mixers are generally divided into two types: weakened laminar flow type and enhanced laminar flow type. The weakened laminar flow type is divided into passive type and active micro-mixing type. The active type is to promote mixing by exerting external influence on the mixer, while the passive type is to take enhanced measures inside the fluid, that is, to control the mixing process by changing or arranging micro-channels of different shapes and structures, such as slotted channels, fluid stratification Flow (add obstacles in the flow channel), serpentine flow channel, induced chaotic convection, etc. Compared with the active micro-mixer, the passive micro-mixer does not need to add additional equipment, is easy to process, and is more convenient to use. In terms of strengthening fluid diffusion and mixing in passive micro-mixers, optimizing the channel structure and strengthening chaotic convection are currently recognized as the best options.

At present, the size of the microchannel in the microfluidic mixer is in the range of tens to hundreds of microns. The Reynolds number of the liquid flow in the microchannel is so small that there is no eddy current, and the mixing between liquids mainly depends on molecular diffusion motion. Compared with the macro situation, the mixing time is greatly prolonged and the mixing effect is poor. Therefore, special methods must be adopted to increase the contact area between liquids or enhance convection to improve mixing efficiency.

Contents of the invention

The purpose of the present invention is to provide a cross-shaped micro-mixer with a simple structure and an axisymmetric logarithmic helix that can improve mixing efficiency in order to overcome the deficiencies in the existing micro-mixers, which can realize biochip or micro-full analysis systems Rapid and uniform mixing between different liquids in the medium, strengthening the mixing effect and shortening the mixing time.

The technical scheme adopted by the present invention is: the present invention comprises a cover plate and a base body which are tightly bonded together, and a cross-shaped flow channel, a constriction flow channel and several mixing units which are sequentially connected are arranged between the cover plate and the base body, each Each mixing unit is composed of a narrow straight channel connected, a logarithmic helical flow channel and a logarithmic helical baffle placed in the logarithmic helical flow channel; several mixing units are connected in series and connected to the contraction flow Between the channel and the outlet of the channel; the outlet of the cross-shaped channel connects the inlet of the constricted channel, the outlet of the constricted channel connects the inlet of the narrow straight channel in the first mixing unit, and the outlet of the last logarithmic spiral channel connects the outlet of the channel and The outlet width is the same as that of the flow channel outlet, and the other logarithmic spiral flow channel outlets are all the same width as the narrow straight channel; The number helix baffles are all symmetrical about the central axis; the concave surface of the logarithm helix baffles is facing the inlet of the logarithm helix flow channel.

The contour line of the logarithmic helix flow channel is composed of two logarithmic helixes symmetrically distributed about the central axis, and the equation of the logarithmic helix is , the starting point of the logarithmic helix is located at the apex of the concave end of the logarithmic helix baffle, the wrap angle α is 135°, e is the base of the natural logarithmic function, and its value is 2.71828, is 20μm, k is 0.001, θ1 is 220°～(220°+α);

The contour line of the logarithmic helix baffle is composed of two logarithmic helixes symmetrically distributed about the central axis, and the logarithmic helix equation is , whose starting point is the center point of the inlet of the logarithmic helix flow channel, and the wrap angle β is 30°, is 15 μm, k is 0.001, and θ2 is 270° to (270°+β).

The present invention has the following advantages after adopting the above-mentioned technical scheme:

1. The present invention enables the fluid to form a jet after passing through a narrow straight channel, increasing the fluid velocity and increasing the Reynolds number of the fluid. The jet impacts the logarithmic helix baffle. Due to the special structure of the logarithmic helix baffle, the fluid flows along the logarithmic helix baffle and forms convection with the incoming flow, increasing the disturbance between fluids.

2. When the fluid flows through the logarithmic helix baffle, it will form a wall-attached flow on the convex surface of the logarithmic helix baffle, and the secondary flow phenomenon will appear, increasing the mixing degree of the fluid. The superposition and strengthening of the vortex system is realized through the simple channel structure, thereby increasing the contact area of the fluid and significantly improving the mixing effect.

3. The present invention equidistantly arranges symmetrically separated and recombined channels on the main channel of the cross-shaped micro-mixer, and the fluids are aggregated, separated, and vortexed, and circulated in sequence, which can contact and mix more effectively. The disturbance is increased by means of the geometric shape change of the micro-mixing flow channel and the fluid flow characteristics, that is, the degree of turbulence is increased in the two-dimensional plane, which greatly improves the mixing effect of the planar passive micro-mixer.

Description of drawings

Fig. 1 is a sectional view of the main structure of the present invention;

Fig. 2 is A-A sectional view among Fig. 1;

Fig. 3 is the enlarged schematic diagram of the geometric structure of the cross-shaped flow channel in Fig. 2;

Fig. 4 is the enlarged schematic view of the geometric structure of the mixing unit in Fig. 2;

Fig. 5 is a schematic diagram of the fluid flow principle of the present invention;

In the figure: 1. Main channel entrance; 2. Secondary channel entrance; 3. Cover plate; 4. Shrinking channel; 5. Narrow straight channel; 6. Logarithmic spiral flow channel; 7. Logarithmic spiral baffle ; 8. Runner outlet; 9. Substrate; 10. Cross-shaped runner.

detailed description

As shown in Figure 1 and Figure 2, the main structure of the present invention is divided into upper and lower parts, the upper part is the cover plate 3 of the micro-mixer, and the lower part is the mixing channel base 9 of the micro-mixer. The cover plate 3 and the base body 9 are tightly bonded together, and between the cover plate 3 and the base body 9, a cross-shaped flow channel 10, a flow channel outlet 8, a constricted flow channel 4, several narrow straight channels 5, and several Logarithmic spiral flow channel 6 and several logarithmic spiral baffles 7 . Wherein, a main channel inlet 1 and two auxiliary channel inlets 2 are arranged on the cross-shaped flow channel 10 , the centers of the two auxiliary flow channels are collinear, and the main flow channel and the two auxiliary flow channels are perpendicular to each other to form a cross-shaped flow channel.

The outlet of the main channel of the cross-shaped channel 10 is smoothly connected to the inlet of the constricted channel 4, the outlet of the constricted channel 4 is connected to the inlet of the first narrow straight channel 5, and the outlet of the first narrow straight channel 5 is connected to the first logarithmic spiral channel 6 inlets, the first logarithmic spiral flow channel 6 outlets are connected to the second narrow straight channel 5 inlets, and the second narrow straight channel 5 outlets are connected to the second logarithmic spiral flow channel 6 inlets, so continuously until The outlet of the last narrow straight channel 5 is connected to the inlet of the last logarithmic spiral channel 6 . The width from the inlet to the outlet of the last logarithmic spiral channel 6 gradually increases, and the width of the outlet of the last logarithmic spiral channel 6 is the same as that of the channel outlet 8. In addition, the remaining logarithmic spiral channel 6 The outlets are all identical with the width of the narrow straight channel 5 . The width of the constricted channel 4 gradually decreases from the inlet to the outlet, and the width of the outlet of the constricted channel 4 is equal to the width of the narrow straight channel 5 .

A logarithmic spiral baffle 7 is placed in each logarithmic spiral flow channel 6, the concave surface of the logarithmic spiral baffle 7 is facing the entrance of the logarithmic spiral flow channel 6, and the logarithmic spiral baffle The convex surface of 7 is facing the outlet of the logarithmic spiral flow channel 6 where it is located. There is a gap between the two end edges of the logarithmic spiral baffle plate 7 and the inner wall of the logarithmic spiral flow channel 6, and the gap allows fluid to pass through. A mixing unit is composed of a narrow straight channel 5, a logarithmic spiral flow channel 6, and a logarithmic spiral baffle 7, and the narrow straight channel 5 and the logarithmic spiral flow channel 6 are connected. Several mixing units are connected in series between the constricted channel 4 and the outlet 8 of the channel. Several mixing units connected in series are equidistantly arranged along the direction of the central axis. The concave surface of the logarithmic spiral baffle 7 is directly facing the inlet of the logarithmic spiral flow channel 6 , and the convex surface of the logarithmic spiral baffle 7 is directly facing the outlet of the logarithmic spiral flow channel 6 .

The centers of the main flow channel of the cross-shaped flow channel 10 , the narrow flow channel 4 , the narrow straight channel 5 , the logarithmic spiral flow channel 6 and the logarithmic spiral baffle plate 7 are all on a central axis. Both the logarithmic helical flow channel 6 and the logarithmic helical baffle 7 are symmetrical about the central axis, which is also the central axis of the cross-shaped micro-mixer of the present invention. Multiple mixing units are arranged equidistantly along the axial direction of the central axis, and the number of mixing units is n≥3.

As shown in FIG. 3 , the inlet width of the main channel of the cross-shaped channel 10 is D1, 200 μm<D1<400 μm, and D1 is always equal to twice the inlet width D2 of the auxiliary channel. The length L1 of the main channel inlet is 2.5 times of D1, L1=2.5×(D1), the length L3 of the secondary channel inlet is equal to L1, and the shortest distance L2 between the secondary channel and the contraction channel 4=2×(D1) .

As shown in Figure 4, the axial length of the narrow straight channel 5 is L4, L4=(D1)/2, and the width D3=(D1)/4 of the narrow straight channel 5.

The width of the inlet of the constricted runner 4 is D1, the maximum width of the logarithmic spiral runner 6 is D1, and the width of the outlet of the last logarithmic spiral runner 6 is the maximum width D1, which is the same as the width of the outlet 8 of the runner. The contour line size of the constricted flow channel 4 remains the same as the outer contour line size of the logarithmic helical line flow channel 6 . The contour line of the logarithmic spiral flow channel 6 is composed of two logarithmic spirals distributed symmetrically about the central axis, and the logarithmic spiral equation of the contour line is , the determined wrap angle α is 135°, and its starting point a is located at the apex of the concave end of the logarithmic helix baffle 7, where e is the base number of the natural logarithmic function, and its value is about 2.71828, is 20 μm, k is 0.001, and θ1 is 220° to (220°+α). The logarithmic spiral channel 6 is connected with the narrow straight channel 5 . The axial length of the channel outlet 8 is greater than 500 μm and less than 1000 μm, and the depth of the micro-mixer is equal to (D1)/2.

The vertical distance between the starting point a of the logarithmic spiral and the central axis is D1/3, and the axial distance L5 between the starting point a of the logarithmic spiral and the maximum width of the adjacent logarithmic spiral flow channel 6 is equal to the inlet of the main channel Length L1, namely L5= L1=2.5×(D1).

The contour line of the logarithmic helix baffle 7 is formed by two logarithmic helixes symmetrically distributed about the central axis, and the equation of the logarithmic helix is , the wrap angle β is 30°, where is 15μm, k is 0.001; θ2 is 270°～(270°+β); logarithmic helix The starting point b is the center point of the entrance of the logarithmic helical flow channel 6, the starting point b is located on the central axis, and the baffle thickness of the logarithmic helical baffle 7 is D4=(D1)/4. The main structural parameters and value ranges of each channel affect the mixing performance of the micromixer.

In the present invention, the main channel inlet 1, the secondary channel inlet 2 and the cross-shaped flow channel 10 are arranged on the left side of the micro-mixer, and the flow channel outlet 8 is arranged on the right side of the micro-mixer, so that the inlets of each flow channel are located on the left side of the micro-mixer. The left end of the flow channel and the outlet are at the right end of the flow channel. The width mentioned refers to the width in the front and rear directions, the length mentioned refers to the axial length in the left and right directions, and the depth mentioned refers to the depth in the up and down direction.

As shown in Figure 5, during the work of the present invention, the fluids of two or three different components enter the micro-mixer from a main flow channel inlet 1 and two secondary flow channel inlets 2 respectively, merge and merge in the cross flow channel 10 After a very small degree of mixing, they enter the main channel together. At this time, the mixing basically depends on molecular diffusion, and the degree of mixing is very weak. Then the fluid passes through the constricted flow channel 4, and the fluid contact of various components is more sufficient. After the fluid passes through the narrow straight channel 5, the three streams of fluid are squeezed and accelerated to form jets, and impact the logarithmic helical baffle 7. Due to the logarithmic The helical baffle 7 has a special structure, the fluid flows along the logarithmic helical baffle 7 to both ends, and part of the fluid impacts on the wall of the logarithmic helix flow channel, and between the logarithmic helix flow channel 6 and the logarithmic helix baffle 7 to form a symmetrical vortex, increasing fluid disturbance. When the fluid passes through the logarithmic helical baffle 7, it will form a wall-attached flow on the convex surface of the logarithmic helical baffle 7, and secondary flow phenomenon will appear, increasing the mixing degree of the fluid. After the fluid passes through more than three identical mixing units, the process of shrinkage, vortex formation, dispersion, and wall attachment to vortex formation is repeated, thereby increasing the contact area of the fluid and significantly improving the mixing effect. Finally, it flows out from the channel outlet 8 of the fluid micro-mixer to complete the mixing process.

An embodiment of the invention is provided below:

In this embodiment, CFD software is used to simulate the mixed flow of two different fluid ethanol C ₂ H ₆ O solutions and water in the present invention. The inlet width D1 of the main channel is 200 μm, and the inlet width D2 of the secondary channel is 100 μm. The length L1 of the main channel inlet and the length L3 of the secondary channel inlet are both 500 μm, the shortest distance L2 between the secondary channel 10 and the entrance of the constricted channel 4 is 400 μm, and the axial length L4 of the narrow straight channel 5 is 100 μm, width D3 is 50 μm, and the contour line of the logarithmic helix baffle 7 is two logarithmic helixes symmetrical about the central axis, and its equation The determined wrap angle β is 30°, and the starting point b is at the center point of the inlet of the logarithmic helical flow channel 6, where is 15 μm, k is 0.001; θ2 is 270°～(270°+β), and the thickness of the logarithmic helical baffle 7 is D4=50 μm. The contour line of the logarithmic spiral runner 6 is two sections of logarithmic spirals distributed symmetrically about the central line, and its equation , the determined wrap angle α is 135°, the starting point a is the vertex of the inner arc of the logarithmic helix baffle 7, where e is the base of the natural logarithmic function, and its value is about 2.71828, is 20 μm, k is 0.001, and θ1 is 220° to (220°+α). The axial length of the flow channel outlet 8 is 600 μm.

The mixed liquid is injected into the micro-mixer at a uniform speed from the inlets of the three flow channels under the pressure drive, and the ethanol solution is injected into the inlet flow channel 2. In order to ensure that the fluids of different components are injected into the flow channels in equal amounts, water of equal quality is injected from the flow channel inlet 1. At this time, the ethanol solution flows vertically and oppositely from both sides of the main channel. After passing through the 4 mixing units of the mixer, it flows out from the outlet 8 of the flow channel after being fully mixed.

Claims (5)

1. a kind of cross micro-mixer of axial symmetry log spiral, including closely sealed cover plate together（3）And matrix（9）, its It is characterized in：Cover plate（3）And matrix（9）Between be provided with the cross runner for being sequentially connected and connecing（10）, a contracted channel（4） With several mixed cells, each mixed cell is by a narrow straight channel being connected（5）, a log spiral runner （6）And it is placed on log spiral runner（6）In a log spiral baffle plate（7）Constitute；Several mixed cell strings Contracted channel is connected to after connecing（4）And runner exit（8）Between；Cross runner（10）Outlet connection contracted channel（4）Entrance, Contracted channel（4）Narrow straight channel in outlet first mixed cell of connection（5）Entrance, last log spiral runner （6）Outlet connecting passage outlet（8）And the exit width and runner exit（8）Width it is identical, remaining log spiral runner （6）Outlet with narrow straight channel（5）Width it is identical；Contracted channel（4）With the center of mixed cell in a central shaft On, log spiral runner（6）With log spiral baffle plate（7）All on substantially symmetrical about its central axis；Log spiral baffle plate（7）It is recessed Face faces the log spiral runner at place（6）Entrance, log spiral baffle plate（7）Edges at two ends and log spiral stream Road（6）Inwall between have gap；Log spiral runner（6）Contour line by two on the right of distribution substantially symmetrical about its central axis Number helix is constituted, and log spiral equation is, log spiral starting point is positioned at logarithmic spiral Line baffle plate（7）The apex of concave surface one end, wrap angle sigma is 135 °, and e is the truth of a matter of natural logrithm function, and its value is 2.71828,Be 20 μm, k be 0.001, θ 1 for 220 °~(220 ° of+α)；

Log spiral baffle plate（7）Contour line be that two two log spirals on distribution substantially symmetrical about its central axis are constituted, its Log spiral equation is, its starting point is the log spiral runner at place（6）Entrance center Point, cornerite β is 30 °,Be 15 μm, k be 0.001, θ 2 for 270 °~(270 ° of+β).

2. a kind of cross micro-mixer of axial symmetry log spiral according to claim 1, it is characterized in that：Cross runner （10）One sprue entrance of upper arrangement（1）With two secondary channels entrances（2）, two centers of secondary channels are conllinear, sprue and Two secondary channels are mutually perpendicular to, cross runner（10）Sprue center on center shaft, cross runner（10）Main flow Road outlet connection contracted channel（4）Import.

3. a kind of cross micro-mixer of axial symmetry log spiral according to claim 2, it is characterized in that：Cross runner （10）Sprue entrance width be D1,200 μm<D1<400 μm, D1 is equal to cross runner（10）Secondary channels import it is wide Spend the twice of D2；The length L1=2.5 of sprue import × (D1), the length L3 of secondary channels import is equal to L1, secondary channels and contraction Runner（4）Between beeline L2=2 × (D1)；Narrow straight channel（5）Axial length L 4=(D1)/2, width D 3= (D1)/4。

4. a kind of cross micro-mixer of axial symmetry log spiral according to claim 3, it is characterized in that：Log spiral Runner（6）The starting point of the log spiral of contour line is D1/3 apart from the vertical range of central shaft, apart from adjacent logarithmic spiral Line runner（6）Its maximum width axial distance L5=2.5 × (D1).

5. a kind of cross micro-mixer of axial symmetry log spiral according to claim 3, it is characterized in that：Contracted channel （4）Throat width, log spiral runner（6）Breadth Maximum and last log spiral runner（6）Exit width It is D1.