US20080169192A1

US20080169192A1 - AC electro-osmosis micro-fluidic device for pumping and mixing liquids and method for pumping and mixing liquids

Info

Publication number: US20080169192A1
Application number: US11/698,269
Authority: US
Inventors: Hyung-Jin Sung; Sang-Youl Yoon; Byoung-Jae Kim
Original assignee: Korea Advanced Institute of Science and Technology KAIST
Current assignee: Korea Advanced Institute of Science and Technology KAIST
Priority date: 2007-01-11
Filing date: 2007-01-23
Publication date: 2008-07-17
Also published as: JP2008170405A; KR20080066123A; JP4660492B2

Abstract

Disclosed herein is a device for mixing micro-fluids while pumping them or a device for pumping and simultaneously mixing the liquids and bio-molecules and a method for mixing and simultaneously pumping the liquids, and more particularly to a device for mixing and pumping micro-fluids having electrode pairs, in which each pair consists of two electrodes: an electrode pair having a first electrode and a second electrode with a greater width than the first electrode are disposed in parallel, provided on at least one internal face of a liquid channel and a method for mixing and pumping micro-fluids by applying an alternating current voltage to the electrode pair.

According to the present invention, an alternating current electro-osmosis occurs near an electrode pair comprising a relatively narrow electrode and a wide electrode to produce complicate flow characteristics so that liquids are effectively mixed and simultaneously pumped in the fields of a small medical device or a small fluid device, etc.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates, generally, to alternating current electro-osmosis micro-fluidic devices for mixing and pumping liquids and methods thereof, more particularly, to a device for mixing and pumping micro-fluids having electrode pairs, in which each pair consists of two electrodes: an electrode pair having a first electrode and a second electrode with a greater width than the first electrode are disposed in parallel, provided on at least one internal face of a liquid channel and a method for mixing and pumping micro-fluids by applying an alternating current voltage to the electrode pair.
2. Description of the Related Art
One of the important problems in a lab-on-a-chip field which is a small medical device for diagnosing and curing a disease is to mix and pump micro-fluids.
In general, an infinitesimal amount of reagents comprising these micro-fluids or these reagents mixed with bio-molecules such as DNA, RNA or erythrocyte should be moved to the next step to be diagnosed.
Lap-on-a-chips include a lot of fluid channels in order to mix and transfer micro-fluids and bio-molecules. However, as the fluid channel used in the lab-on-a-chip has a very small cross-section less than hundreds μm, it is not easy to mix or pump the fluids with a relatively large viscosity.
Accordingly, attempts to invent various methods to mix the fluids in the micro-fluid channels have been made.
The representative one of the conventional methods is to mix a fluid or fluids with bio-molecules in a channel by changing the shape of the channel disclosed by Strook et., al. (A. D. Strook, S. K. W. Dertinger, A. Ajdari I. Mezic, H. A. Stone, G. M. Whitesides, “Chaotic mixer for micro-channels”, Science, Vol. 295, pp. 647, 2002.)
In other words, it is a technology to make a herringbone-shaped groove at the bottom of the micro-fluid channel and mix the fluids.
However, these methods have a disadvantage to make complicated channels.
In the meantime, various methods for pumping a small amount of micro-fluids have been researched and the researches on a small pump have mainly been carried out. This is a method for pumping a liquid by applying a pressure on the fluid mainly using mechanical methods.
However, this method requires for an individual machine for applying a pressure to a fluid and causes a problem that the small fluidic device or the lab-on-a-chip becomes more complicated and is difficult to be miniaturized.
Another method for pumping a liquid is an electric method, using an electro-osmosis phenomenon.
The method using this electro-osmosis is classified into a method for applying a direct current and a method for applying an alternating current.
The method for pumping micro-fluids by the electro-osmosis applying a direct current requires a voltage of several kV to be applied. This high voltage makes it difficult to customize a small fluidic device and has fatal disadvantages in changing characteristics of object fluids and bio-molecules as well as affecting the stability of a machine.
On the contrary, according to the electro-osmosis method for applying an alternating current, micro-fluids are moved just by applying a voltage of several V (A. B. D. Brown, C. G. Smith and A. R. Rennie, “Pumping of water with ac electric fields applied to asymmetric pairs of microelectrodes,” Physical Review E, Vol. 63, 016305, 2002).
As described above, researches in the fields of mixing a small amount of micro-fluids and pumping the micro-fluids have been individually carried out. Accordingly, a fluid mixer and a pump exist separately in a lab-on-a-chip field including a small micro-fluidic device so far.

SUMMARY OF THE INVENTION

An object of the present invention is to provide with a device for mixing and pumping complicate micro-fluids, which is capable of pumping and simultaneously mixing a small amount of micro-fluids or mixing fluids with bio-molecules (DNA, RNA and erythrocyte, etc.).
In addition, another object of the present invention is to provide with a method for providing with a miniaturized and highly integrated device by integrating mixing and pumping liquids and a method for manufacturing such device conveniently.
In order to attain the above objects, the micro-fluidic device for pumping and mixig micro-fluids according to the present invention is provided with electrode pairs, in which each pair consists of two electrodes: an electrode pair having a first electrode and a second electrode with a greater width than the first electrode on at least one internal face of a liquid channel.
The liquid channel may have a tubular shape but can have any shape of cross-sections of the tube.
The liquid channel may be a micro-fluidic channel.
The liquid channel may be made of an insulating glass or a polymer compound.
The device for mixing and pumping micro-fluids according to the present invention may be a device including the liquid channel or a device comprising the liquid channel itself.
The electrode pairs may have a linear or a curved strip shape and at least one electrode pair has a bend or more.
The electrode pair according to the present invention is characterized by that a voltage is applied by an alternating current power source.
According to the present invention, the cross-section of the liquid channel is not confined to a rectangular shape, i.e., the shape can be a circle, triangle, pentagon and hexagon, etc., and the entire liquid channel may have either a linear or a curved shape.
The cross-section of the liquid channel is within hundreds μm.
According to the present invention, the components of the electrode may be a conducting metal, especially gold, silver, titanium, platinum, copper or their mixtures. The components of the electrode are not limited by the said metal and may be whichever is an electrically conducting material used in the electro-osmosis method in the level of those skilled in the present invention.
It is preferable that the widths of the electrodes be within tens μm and more preferable that the first electrode and the second electrode be from 1 to 90 μm, but the width of the first electrode is required to be a relatively small in comparison with that of the second electrode.
According to the present invention, at least one electrode pair is provided in a length direction or a width direction of the liquid channel.
In order to obtain the above objects, a method for mixing and pumping liquids according to the present invention comprises: providing with electrode pairs, in which each pair consists of two electrodes: an electrode pair having a first electrode and a second electrode with a greater width than the first electrode on at least one internal face of a liquid channel and mixing and pumping liquids by applying a voltage through an alternating current power source.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view seeing through the inside of a device for mixing and pumping liquids in accordance with an embodiment of the present invention;

FIG. 2 is a cross-sectional view of a device for mixing and pumping liquids in accordance with an embodiment of the present invention by the cross-section 1 of FIG. 1;

FIG. 3 is an upper face view schematizing the main flow direction of a fluid in a device for mixing and pumping liquids including at least two electrode pairs in accordance with an embodiment of the present invention;

FIG. 4 is an upper face view of an electrode pair for mixing and pumping liquids in accordance with an embodiment of the present invention;

FIG. 5 is an upper face view of a device for mixing and pumping liquids having at least two electrode pairs and of which the liquid channel is curved; and

FIGS. 6 and 7 are upper face views of the shapes and patterns of electrode pairs for mixing and pumping liquids with the electrode pair according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Reference now should be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components in the following description of the present invention.
In addition, detailed descriptions may be omitted if it is determined that the detailed descriptions of related well-known functions and constructions may make the gist of the invention unclear.
According to an embodiment of the present invention, asymmetric electrode pairs are provided in a liquid channel, especially on an internal face of a fluid channel in order to mix the micro-fluids in a herringbone or a diagonal shape. In other words, the electrodes are provided to have a bent shape while forming regular angles in the proceeding direction of a fluid channel in disposing the electrodes.
In FIG. 1, which is a cross-sectional view seeing through the inside of the device for mixing and pumping micro-fluids according to an embodiment of the present invention, a micro-fluid channel (100) with a plurality of electrode pairs (103) disposed on one face is suggested, each having a first electrode (101) and a second electrode (102).
At least one electrode pair may be disposed regularly or irregularly with a periodic instance, and may be disposed on at least one face inside the micro-fluid channel (100).
When disposing several electrode pairs, the electrode pairs may have been disposed in different types, and the distance between a first electrode and a second electrode in one electrode pair may differ from one electrode pair to another electrode pair.
FIG. 2 shows a cross-section according to the present invention viewed based on the cross-section 1 of FIG. 1.
Referring to FIG. 2, the upper and the lower portions are the upper and the lower part of a liquid channel made of an insulating material like glass, in which a fluid is flown.
According to an embodiment of the present invention, electrodes are provided at a lower portion of the micro-fluid channel, one electrode pair (203) having a first electrode (201) and a second electrode (202) disposed in parallel.
If the width of the first electrode (201) is W1 and the width of the second electrode (202) is W2, W1 is smaller than W2.
The first electrode (201) and the second electrode (202) are disposed in parallel but electrically isolated because of the predetermined interval (G1) therebetween.
In addition, when a plurality of electrode pairs are disposed, the electrode pairs have the predetermined interval (G2) therebetween so that electrode pairs can be electrically insulated each other.
Referring to FIG. 2, several electrode pairs are electrically connected by alternating current power source. In other words, the first electrodes of the several electrode pairs are connected with one terminal of the alternating current power source and the second electrodes are connected with the other terminal of the alternating current power source.
And then, when an alternating current power source is applied, the fluid on the electrode has a polarity electrically and the fluid moves by the reaction of an electric field. The direction of the force exerted on fluid is always the same, since the polarity of fluid over the electrode and the direction of the electric fields there change simultaneously in accordance with an alternating current source.
The voltage of the alternating current power is a unit of several volts, in other words, a comparatively low voltage is applied.
The portion where the fluid is supported is the one just on the electrode and the direction to be supported is shown in FIG. 3.
In other words, as shown in FIG. 3, the fluid moves in the direction from the first electrode (301) with a small width to the second electrode (302) with a large width, perpendicular to the length direction where the electrode is arranged.
According to the embodiment of the present invention shown in FIG. 3, the arranged shape of the electrode pair (303) has one bend in the interim as a linear strip, and the fluid is supported in an arrow direction and can be pumped and simultaneously mixed.
Accordingly, in order to integrate pumping and mixing micro-fluids, it is preferable to include at least one bend in the disposition structure of an electrode pair.
FIGS. 4 to 7 are upper face views of a device for mixing and pumping micro-fluids comprising electrode pairs.
FIG. 4 shows that just one electrode pair (403) is exploded, and the width of the first electrode (401) is relatively narrow in comparison with that of the second electrode (402) and the angle (α) made by the wall surface at one side of a liquid channel and the electrode pair may be different from the angle (β) made by the wall surface at the other side of the liquid channel and the electrode pair. The limiting condition for mixing and pumping the micro-fluids is that α≠0°, α≠90° and α≠180°, and β≠0°, β≠90° and β≠180°.
Furthermore, the distance (p1) from the wall surface on one side of a liquid channel to one bent point of the electrode pair may or may not be the same as the distance (p2) from the wall surface on the other side of the liquid channel to the same bent point of the electrode pair.
In case that more than one electrode pair is provided, an electrode pair of which the width (W1) differs from the width (W2) may be disposed, and the electrode pair of which the angle (α) differs from the angle (β) can be disposed. And the electrode pair of which p1 differs from p2 can be disposed.
In other words, at least one electrode pair having optional values, W1, W2, α, β, p1, p2 can be provided. The said optional values, W1, W2, α, β, p1, p2 of each electrode pairs can be different values.
The electrode pairs may be disposed regularly or irregularly.
The irregular disposition of the electrode pairs may be a source of a more complex and variable force in mixing and pumping the micro-fluids.
When W1 is set to be different from W2, a from P and p1 from p2 in each electrode pair, the capability of mixing the fluid can be remarkably improved.
The surface where the electrode pairs are disposed is shown in the upper face views of FIGS. 5 to 7 viewed from the upper side in a device for mixing and pumping micro-fluids comprising at least two electrode pairs, but is not necessarily limited to these shapes.
It is preferable that the entire shape of the micro-fluid channel be mainly in a straight line but the fluid channel with an internal surface having a curved line is possible as shown in FIG. 5.
In addition, as shown in FIG. 6, various shapes of electrode pairs (603) can exist in the directions of a width and a length of the liquid channel.
FIG. 7 shows that the electrode pair (703) is disposed in a linear and a diagonal shape, not a shape in which a part of the electrode pair (703) is bent.
In this shape, micro-fluids can be pumped and mixed, but the effect of pumping and mixing the microfluids may be low in comparison with a liquid channel having a shape with a bend provided on at least one electrode pair of a linear or a curved line strip or a shape with various dispositions of such electrode pairs, as described above.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
As described above, according to the present invention, a small amount of micro-fluids are pumped and simultaneously mixed and the number of the devices for pumping and mixing the fluids required for manufacturing a micro-fluidic system can be reduced, resulting in simplifying the entire system. Also, according to the present invention, the possibility causing malfunctions is decreased.
In addition, a lab-on-a-chip capable of carrying out simultaneously mixing and pumping is provided to have an effect on miniaturizing and highly integrating a device.
There is an advantage in that there are no difficulties to adopt this device in the existing electronic device or a system by using an electricity in both pumping and mixing a fluid.
Furthermore, according to the present invention, a driving voltage is low and safe by far in comparison with a micro-fluidic device of the other electro-osmosis method and it consumes extremely little power to be very useful economically.

Claims

1. A micro-fluidic device for pumping and mixing liquids provided with electrode pairs, in which each pair consists of two electrodes: an electrode pair having a first electrode and a second electrode with a greater width than the first electrode on at least one internal face of a liquid channel.

2. The device of claim 1, wherein the electrode pairs have a linear or a curved strip shape.

3. The device of claim 2, wherein at least one electrode pair has at least one bend in its shape.

4. The device of claim 1, wherein the electrode pairs are applied by a voltage through an alternating current power source.

5. The device of claim 1, wherein the cross-section of the liquid channel is one selected from the group consisting of substantially a circle, triangle, rectangle, pentagon and hexagon.

6. The device of claim 1, wherein the liquid channel has a linear or a curved shape.

7. The device of claim 1, wherein the electrodes are conducting metals.

8. The device of claim 1, wherein the widths of the first electrode and the second electrode are 1 to 90 μm.

9. The device of claim 1, wherein at least one electrode pair is provided in a length direction or a width direction of the liquid channel.

10. A method for mixing and pumping liquids, which comprises: providing with electrode pairs, in which each pair consists of two electrodes: a first electrode and a second electrode with a greater width than the first electrode on at least one internal face of a liquid channel, mixing and pumping liquids by applying a voltage through an alternating current power source.

11. The method of claim 10, wherein the electrode pair has a linear or a curved strip shape including at least one bend.

12. The method of claim 10, wherein the widths of the first electrode and the second electrode are 1 to 90 μm.

13. The method of claim 10, wherein at least one electrode pair is provided in a length direction or a width direction of the liquid channel.