JP2006205080A - Micromixer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel micromixer capable of performing mixing and agitation independent of complexity and lamination of a flow passage pattern. <P>SOLUTION: A Y-shaped flow passage 3 is formed on a substrate 2 of a micro fluid element 1. The flow passage 3 has a pair of inflow openings 4, 4, for example, at the cover part of a glass or silicon substrate for injecting a solution to be mixed, and an outflow opening 5 for discharging the mixed solution. Microflow passages 6, 6 each starting from the inflow opening 4, 4 and reaching a joining point 7 are formed on the inside of the substrate 2, the injected solution is joined at the joining point 7 and mixed in a mixing passage 8, and the mixed solution is transferred to the outflow opening 5. A through hole 13 is formed above the mixing passage 5 in the vicinity downstream of the joining point 7 in the passage 3, the through hole 13 is disposed with a stirring element 14 with sharpened tip end and a vibrator, PZT11, for exciting the stirring element at a desired frequency. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel micromixer capable of mixing and stirring fluids using a microfluidic device having a microstructure represented by μ-TAS, Lab-on-A-chip, and microreactor. It is.

Microfluidic devices with fine structures, such as chemical synthesis / analysis, genome drug discovery support, and various disease diagnosis chips, are effective for reaction, separation, and purification using interfaces, and temperature control is easy. In addition, it is known to have a number of advantages that it is small in size, has a small amount of sample, and is capable of high-speed processing.
As one function of such a microfluidic device, there is a mixing technique using the characteristics of the fluid in the microchannel, and various micromixers have been proposed. For example,
JP 2004-113968 A

As an example of a simple micromixer, for example, as shown in FIG. 3, a substrate 2 of a microfluidic device 1 is provided with Y-shaped and T-shaped flow paths 3.
That is, a pair of inlets 4 and 4 and an outlet for discharging the mixed solution are injected into the flow path 3 of the microfluidic device 1 in order to inject a solution to be mixed into the lid portion of the glass or silicon substrate. 5 is provided.
Further, the micro flow paths 6 and 6 are drawn out from the respective inlets 4 and 4 inside the substrate 2, merged at the junction 7, mixed in the mixing channel 8, and guided to the outlet 5. ing.

  However, in such a microfluidic device 1, when the size of the microchannel 6 is several hundred μm or less, the fluid in the microchannel 6 is affected by the viscosity and the laminar flow becomes dominant. When the above solution is mixed, even if the Y-shaped flow path 3 as described above is produced, it is mixed only by diffusion at the interface where the two liquids are in contact, and the mixing efficiency is poor.

  On the other hand, in order to improve the mixing efficiency, in order to increase the area of the interface between the two liquids, each of the plurality of inlets is subdivided, and the merging structure is complicated and layered to mix the solutions. There are a method and a method using a pseudo turbulent flow generated by colliding with a channel wall. In the above-described method, it is necessary to optimize the channel structure according to the viscosity of the solution to be mixed and the diffusion coefficient of particles contained in the solution when designing the microchannel.

Furthermore, there is an ultrasonic micromixer 9 as shown in FIG.
ZhenYang, et al. Sensors and Actuators A 93 (2001) 266-272 In this ultrasonic micromixer 9, a diaphragm 10 is formed on the lower surface of the mixing channel 8 in the Y-shaped channel 3 shown in FIG. In addition, the piezoelectric element 11 such as PZT is in close contact with the lower surface of the diaphragm 10. A pulse voltage is applied to the piezoelectric element 11 to generate vibration, and the vibration is conducted to the solution in the mixing channel 8 through the diaphragm 10, thereby promoting the mixing of the sample liquid and the reagent liquid. .

However, since the above method is a mixing method that relies on particle diffusion, efficient mixing is not possible, and local mixing is difficult and affects other parts of the chip. It becomes difficult to combine functions (mixing + analysis) such as Lab-on-A-chip.
The present invention has been proposed in order to overcome the above-described problems, and provides a novel micromixer capable of mixing and stirring without relying on complication and lamination of flow path patterns. With the goal.

In order to solve the above-described problem, in the present invention, in claim 1, at least two or more inlets for injecting fluids to be mixed, and the fluids are mixed and stirred together from these inlets, In a microfluidic device equipped with a flow channel that communicates with the outlet that takes out the mixed and stirred liquid mixture, the stirrer is immersed directly in the fluid in the flow channel at an appropriate position in the flow channel after the merge. We propose a micromixer that is configured to vibrate and locally promote mixing and stirring of fluids.
Further, in the present invention, in claim 2, a through-hole communicating with the flow path is provided at an appropriate position of the flow path after the merging, and the stirrer is immersed in the flow path through the through-hole, This stirrer has a sharpened tip, and a micromixer including a vibrator that excites the stirrer at an arbitrary frequency is proposed.
Also, in the present invention, in claim 3, the stirrer is composed of an AFM tip made of silicon or silicon nitride having a sharpened tip of several hundred nm or less, and the tip side is installed so as to be immersed in the fluid in the flow path. Proposed micromixer.
Further, in the present invention, in claim 4, the stirrer is constituted by a fiber probe made of quartz or plastic having a sharpened tip of several hundred nm or less, and the tip side is installed so as to be immersed in the fluid in the channel. Propose a micromixer.
Also, in the present invention, the micromixer according to claim 5 is proposed, wherein the stirrer is made of a metal having a sharp tip, plastic, or other material, and the tip side is installed so as to be immersed in the fluid in the flow path. To do.
Further, in the present invention, the fluid according to claim 6, which is generated by the vibration behavior of the tip of the vibrator by exciting the vibrator to the stirrer whose tip is immersed in the fluid to give an arbitrary vibration frequency and vibration amplitude. We propose a micromixer designed to promote fluid mixing and agitation with the convection pattern.
Further, according to the present invention, in claim 7, by exciting the vibrator to the stirrer whose tip is immersed in the fluid, an arbitrary vibration amplitude is given at the resonance frequency of the vibrator, and the vibration behavior of the vibrator tip is determined. The present invention proposes a micromixer configured to promote mixing and agitation of fluids by the generated convection pattern of fluids.

Since a new solution mixing / stirring technique that does not depend on complication / stacking of the flow path pattern is established, the microfluidic device having a fine structure can be simplified and miniaturized.
Further, unlike a micromixer using ultrasonic vibration, a stirrer is directly immersed in a solution, and the stirrer is vibrated with a vibrator to stir, so that stirring in a very local region is possible.
In addition, since the resonance at the resonance frequency of the stirrer is used, even if the vibration amplitude of the vibrator for exciting the stirrer is about several nanometers, the vibration amplitude is amplified at the tip of the stirrer, and the propagation of ultrasonic vibration and stirring of the vibrator itself The influence of vibration at the child-fluid interface can be ignored.
In addition, since the tip of the stirrer is sharpened, the fluid resistance at the tip that is the center of stirring is reduced, and efficient stirring is possible.
Furthermore, in order to mount the micromixer according to the present invention, it is not necessary to form a special flow path, and mixing and stirring can be performed if a minute through hole exists in the lid portion at the upper part of the flow path.

  According to the first aspect, since the vibrator is immersed and stirred directly in the fluid, stirring in a local region is possible.

  According to the second aspect, the stirring bar tip is caused to vibrate at a primary or higher resonance frequency of the stirring bar by the vibrator, thereby generating a specific vibration at the tip of the stirring bar. The solution forms a unique convection pattern, which facilitates mixing and stirring.

  According to the third, fourth, and fifth aspects, the AFM tip, the fiber probe, the stirrer composed of a metal having a sharp tip, plastic, or other material is immersed in the fluid in the flow path to give vibration, Mixing and stirring are promoted.

According to the sixth and seventh aspects, the stirrer with the sharpened tip immersed in the fluid is made of the fluid using the vibration behavior of the tip of the vibrator generated by giving an arbitrary vibration frequency and vibration amplitude by the vibrator. A convection pattern can be obtained.
For this reason, mixing / stirring can be performed efficiently only by optimizing the shape of the tip of the stirrer or the frequency / amplitude of the piezoelectric element without designing the flow path of the microfluidic element for each mixed solution having different viscosities.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a micromixer according to the present invention will be described with reference to the accompanying drawings with an embodiment.

FIG. 1 schematically shows a micromixer 12 according to the present invention. In addition, here, the same reference numerals are given to the components that are substantially the same in the micromixer shown in the prior art.
In this case, the micromixer 12 is provided with a Y-shaped flow path 3 on the substrate 2 of the microfluidic device 1, and the flow path 3 injects a solution to be mixed into, for example, a lid portion of a glass or silicon substrate. Therefore, it has a pair of inflow ports 4 and 4 and an outflow port 5 for discharging the mixed solution.
In addition, microchannels 6 and 6 extending from the respective inlets 4 and 4 to the junction 7 are formed inside the substrate 2, and the injected solution is merged at the junction 7 to be mixed in the mixing channel 8. The mixed solution is brought to the outlet 5.
A through hole 13 is provided in the upper part of the mixing channel 5 in the vicinity of the junction 7 in the channel 3, and the through hole 13 has a stir bar 14 with a sharpened tip, PZT 11 which is a vibrator for exciting the stirring bar 14 at an arbitrary frequency is arranged.

  In other words, the operation principle of the micromixer 12 configured as described above will be described. For the sake of simplicity, as shown in FIG. 2, if the fluid in the microchannel 6 is represented as the microdroplet 15, the micromixer 12 is agitated. Mixing and stirring can be promoted by causing the fluid near the tip of the stirring bar 14 to generate a unique convection pattern or pseudo turbulent flow when the tip of the core 14 is immersed and the stirring bar 14 is vibrated with PZT 11. Based on.

Therefore, as shown in FIG. 2, the action of mixing / stirring of the micromixer 12 will be verified.
First, in order to track the fluid behavior, the tip 16 of the fiber probe produced by suspending 3 μm fluorescent particles as a tracer in the microdroplet 15 and sharpening the optical fiber as the stirrer 14 is placed in the microdroplet 15. Soak in.
Next, the fiber probe is vibrated by the PZT 11 to vibrate the fiber probe tip 16. At this time, the behavior of the fluid in the microdroplet 15 near the tip 16 of the fiber probe is observed with a fluorescence microscope 17.
The stirrer 14 is sharpened at the tip, but influences the fluid behavior in the liquid according to the shape of the tip of the stirrer 14, the vibration frequency by the vibrator PZT11, and the vibration amplitude. I know that.

  When the shape of the tip of the stirrer 14 remains a fine diameter and is not processed (no etching), and the taper angle of the tip is 60 °, 30 °, for example, and given a predetermined vibration frequency, Since the amplitude of the PZT 11 is very small, the amplitude of the fiber probe tip 16 is also small, no change in fluid behavior appears, and only ultrasonic vibration is applied to the fluid in the droplet, but the vibration frequency is 20 to 30 kHz. A steep resonance point was obtained.

  Next, when the PZT 11 was vibrated at the resonance frequency of the fiber probe and the vibration of the fiber probe tip 16 was amplified, a change appeared in the fluid behavior of the fiber probe tip 16.

Furthermore, when the vibration amplitude is changed by changing the voltage applied to the PZT 11 at the resonance frequency of the fiber probe, free vortices (left-right rotation) and a plurality of vortices can be obtained centering on the tip of the stirrer 14 according to each amplitude. I understood.
In this case, when the applied voltage is relatively small, a free vortex centered on the fiber probe tip 16 appears and shows a specific convection pattern.
When the voltage applied to the PZT 11 is increased, the convection pattern begins to change, the single vortex increases to two or four, and a symmetrical pseudo-turbulent flow around the fiber probe tip 16 is generated. Thus, it can be seen that efficient stirring of the fluid in the microdroplet becomes possible.

From the above, by satisfying the same fiber probe, the same PZT, and the same operating conditions (vibration frequency, vibration amplitude),
(1) A symmetrical convection pattern is obtained around the tip of the probe (stirrer 14).
(2) The fluid behavior changes at the resonance frequency.
(3) By changing the applied voltage, free vortices (left-right rotation) and a plurality of vortices can be obtained.
(4) The flow velocity is increased by reducing the tip curvature.
(5) The fluid behavior has reproducibility (arbitrary voltage / frequency).
(6) There is frequency dependence.
That was discovered.

It is typical explanatory drawing for demonstrating the structure of the micromixer concerning this invention. It is a schematic diagram provided in order to demonstrate the mixing and stirring action of the fluid of the micromixer shown in FIG. It is typical explanatory drawing which showed an example of the conventional micromixer. It is typical sectional drawing which showed another example of the conventional micromixer.

Explanation of symbols

1 Microfluidic device 2 Substrate 3 Channel 4 Inlet 5 Outlet 6 Microchannel 7 Junction point 8 Mixing channel 9 Ultrasonic micromixer 10 Diaphragm 11 PZT
12 Micromixer 13 Through-hole 14 Stirrer 15 Microdroplet 16 Tip 17 Fluorescence microscope

Claims (7)

At least two or more inlets for injecting fluids to be mixed, and a flow path communicating with the outlets for mixing and agitating the fluids from the inlets to mix and agitate the liquids to be mixed and agitated In the microfluidic device, the stirrer is directly immersed in the fluid in the flow path at the appropriate position of the flow path after merging, and the stirrer is vibrated to promote local mixing and stirring of the fluid. Features a micromixer. A through hole communicating with the flow path is provided at an appropriate position of the flow path after the merging, and the stirrer is immersed in the flow path through the through hole, and the stir bar has a sharpened tip. The micromixer according to claim 1, further comprising a vibrator that excites the stirring bar at an arbitrary frequency. 3. The micromixer according to claim 1, wherein the stirrer is constituted by an AFM chip and is disposed so that a tip side is immersed in a fluid in the flow path. The micromixer according to claim 1 or 2, wherein the stirrer is constituted by a fiber probe and is arranged so that a tip side is immersed in a fluid in the flow path. 3. The micromixer according to claim 1, wherein the stirrer is made of metal, plastic, or other material having a sharp tip, and is disposed so that the tip side is immersed in the fluid in the flow path. . Mixing and agitation of the fluid by the convection pattern of the fluid, which is caused by the vibration behavior of the agitator tip by giving an arbitrary vibration frequency and amplitude by exciting the vibrator to the agitator whose tip is immersed in the fluid The micromixer according to any one of claims 1 to 5, wherein the micromixer is configured to promote heat. By exciting the vibrator to the stirrer whose tip is immersed in the fluid, an arbitrary vibration amplitude is given at the resonance frequency of the vibrator, and the convection pattern of the fluid is generated by the vibration behavior of the stirrer tip. The micromixer according to claim 6, wherein mixing and stirring are promoted.

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