KR100468854B1 - Micro structure available for controlling minute quantity of fluid flow - Google Patents

Abstract

A microstructure capable of controlling micro flow rates is disclosed. The disclosed microstructure includes an actuator for discharging fluid flowing from a fluid inlet through a nozzle at a predetermined frequency, and a fluid outlet formed at a diameter larger than the diameter of the nozzle in front of the nozzle, through which the fluid flows, and an inner space thereof. Is divided into a gaseous region located at the nozzle side and a liquid region located at the fluid outlet side where the fluid exists in the liquid phase, and a gaseous fluid in the gaseous region is provided on the outer periphery of the gaseous region. And vapor phase generating means for generating. The actuator is provided with a fluid chamber connected to a fluid inlet at a downstream side thereof and a nozzle connected at an upstream side thereof to fill the fluid, and a driving means provided at an outer circumference of the fluid chamber to provide a driving force for discharging the fluid through the nozzle. . According to this configuration, the size is small, easy to apply in the field of MEMS, precise control of the micro flow rate can be implemented to implement a micro pump or valve having a high energy efficiency.

Description

Micro structure available for controlling minute quantity of fluid flow

The present invention relates to a microstructure, and more particularly, to a microstructure that can be applied to a micro pump and a valve capable of controlling a micro flow rate.

Recent breakthroughs in micro-machining technology have enabled the development of multi-functional Micro Electro Mechanical Systems (MEMS). These MEMS devices have many advantages in terms of size, cost and reliability and are being developed for a wide range of applications.

In particular, in the fields of genetic engineering, medical diagnostics, and new drug development, researches are being conducted to miniaturize a fluid system required for a conventional chemical reaction and analysis device on a single chip, thereby serving as a basic component of the fluid system. Development of technologies related to microstructures such as micro pumps and valves capable of controlling micro flow rate in microliter units has been actively performed.

1A and 1B show a micropump with a shank valve as an example of a conventional microstructure.

Referring together to FIGS. 1A and 1B, a conventional micropump is driven by a piezoelectric body 12 attached to an upper thin film of a pumping chamber 10. A fluid inlet 14 and a fluid outlet 16 are connected to a lower portion of the pumping chamber 10, and a check valve 15 is connected to each of the fluid inlet 14 and the fluid outlet 16 and the pumping chamber 10. , 17). In the micropump having such a structure, when the volume of the pumping chamber 10 is increased by deforming the piezoelectric body 12 by the voltage applied to the piezoelectric body 12 as shown in FIG. 1A, the second check valve ( 17 is closed and the first check valve 15 is opened and the fluid is introduced into the pumping chamber 10 through the fluid inlet 14. Subsequently, when the volume of the pumping chamber 10 is reduced by deformation in the opposite direction of the piezoelectric body 12 as shown in FIG. 1B, the first check valve 15 is closed and the second check valve 17 is closed. While opening, the fluid is discharged by a predetermined amount through the fluid outlet 16.

However, in the conventional micropump having such a structure, check valves 15 and 17 for inducing the flow of fluid in one direction are used, and the check valves 15 and 17 are movable to be operated in a fine structure. Element. However, pumps and valves applied in the field of MEMS have to be very small in size, making it difficult to apply movable elements such as the check valves 15 and 17. There is a difficult disadvantage. In addition, the mass inertia of the check valves 15 and 17 makes it difficult to operate at high frequencies, and the loss of pressure head generated when the fluid passes through the check valves 15 and 17 is eliminated. There is a disadvantage in that the efficiency of the pump is large.

2 shows another example of a conventional micropump.

The micropump shown in FIG. 2 has a structure without a movable element inside the pump by having a pair of diffuser / nozzle elements 24 instead of a check valve. The two diffuser / nozzle elements 24 are connected to the lower part of the pumping chamber 20, and the piezoelectric body 22 is provided as a driving means in the upper thin film of the pumping chamber 20. The two diffuser / nozzle elements 24 each cause flow losses in different directions, so that net flow can be generated in one direction without the check valve. However, the micropump with this structure depends on the flow loss of the diffuser / nozzle element 24, and the difference in the flow loss decreases rapidly as the size of the system decreases, so the efficiency of the pump applied to MEMS is very small. There is a disadvantage to losing. On the other hand, in order to design a pump having a certain degree of efficiency, the size of the pump becomes large and it is difficult to apply to the field of MEMS.

Although not shown, another example of the microstructure is a micropump using an electrohydrodynamic (EHD) phenomenon. In such micropumps, there is a limitation that the working fluid must be polarized because the flow of fluid is induced by a strong electrostatic force. In addition, like the micropump shown in FIG. 2, since there is no check valve, it is difficult to have high efficiency.

The present invention has been created to solve the problems of the prior art as described above, and is particularly small in size to be applied to micro pumps and valves, etc., and precise control of the micro flow rate by adjusting the discharge frequency and the number of unit actuators It is an object to provide a microstructure that is possible and has a high energy efficiency.

1A and 1B show a micropump with a check valve as an example of a conventional microstructure.

2 is a view showing another example of a conventional micropump.

3 is a plan view showing a microstructure applied to a micropump as a first preferred embodiment of the present invention.

4A to 4L are diagrams illustrating a result of analyzing a process of ejecting droplets from the micropump shown in FIG. 3.

5 is a graph showing the pressure head of the micro pump according to the diameter of the nozzle and the reservoir shown in FIG.

6 is a schematic perspective view showing a micropump having a plurality of nozzles as a second preferred embodiment of the present invention.

7 is a plan view showing a microstructure applied to a microvalve as a third preferred embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100,200 ... micro pump 110 ... actuator

112,212.Fluid entrance 114.Fluid chamber

116,216 ... Nozzle 118 ... First Heater

120,220 Reservoir 122,222 Fluid outlet

124 ... Second Heater 300 ... Micro Valve

300a, 300b, 300c ... Unit structure 310a, 310b, 310c ... actuator

320a, 320b, 320c ... reservoir

The present invention to achieve the above technical problem,

An actuator for discharging the fluid introduced from the fluid inlet through a nozzle at a predetermined frequency;

It is formed in a diameter larger than the diameter of the nozzle in front of the nozzle, has a fluid outlet through which the fluid flows, the inner space is where the fluid is in the gaseous phase and the gaseous region located on the nozzle side and the fluid is in the liquid phase A reservoir divided into a liquid phase region located at a side of the fluid outlet; And

It is provided on the outer periphery of the gas phase region of the reservoir provides a micro-structure comprising; gas phase generating means for generating a gaseous fluid in the gas phase region.

The actuator is a fluid chamber connected to the fluid inlet on the downstream side and the nozzle is connected to the upstream side and the driving means is provided on the outer periphery of the fluid chamber to provide a driving force for discharging the fluid through the nozzle. It is preferable to provide.

Here, the drive means preferably has a first heater for generating bubbles by heating the fluid inside the fluid chamber.

In addition, the driving means may have a piezoelectric body that changes the volume of the fluid chamber by being deformed by an applied voltage.

On the other hand, the gas phase generating means preferably has a second heater for generating a gaseous fluid by heating and evaporating the fluid inside the gaseous region of the reservoir.

In addition, the gas phase generating means may have an electrode which generates a gaseous fluid by electrolyzing the fluid inside the gaseous region of the reservoir.

The microstructures can be applied to micropumps in fluid systems. In this case, a plurality of actuators may be arranged in parallel in one reservoir.

The microstructures can also be applied to fluid valves in fluid systems. In this case, a plurality of the microstructures may be connected in series.

The microstructures can also be applied to pressure regulators of fluid systems.

As described above, according to the microstructure according to the present invention, since the microstructure is very small, it is easy to apply to the field of MEMS, and by controlling the discharge frequency and the number of unit actuators, it is possible to precisely control the micro flow rate and thus have a high energy efficiency micro pump. I can implement the valve.

Hereinafter, preferred embodiments of the microstructure according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a plan view showing a microstructure applied to a micropump as a first preferred embodiment of the present invention.

Referring to FIG. 3, the micropump 100 according to the present invention includes an actuator 110 for discharging the fluid introduced from the fluid inlet 112 at a predetermined frequency through the nozzle 116, and the actuator 110. It is provided in front of the reservoir having a reservoir (Reservoir) (120) having a fluid outlet (122) outflow.

The actuator 110 has a cylindrical fluid chamber 114 having a predetermined diameter where the fluid is filled. On the downstream side and the upstream side of the fluid chamber 114, the fluid inlet 112 and the nozzle 116 having a diameter smaller than the diameter of the fluid chamber 114, respectively, are provided at positions facing each other. In addition, a first heater 118 is installed at an outer circumference of the fluid chamber 114 as a driving means for providing a driving force for discharging the fluid inside the fluid chamber 114 through the nozzle 116. The first heater 118 may be formed in an annular shape along the circumference of the fluid chamber 114, and a power source for applying a pulse current is connected to the first heater 118. When a pulse current is applied to the first heater 118, the fluid inside the fluid chamber 114 is heated to generate a bubble B, and the fluid inside the fluid chamber 114 is caused by the expansion force of the bubble B. FIG. Is discharged in the form of droplets D through the nozzle 116. This will be described in detail later.

On the other hand, as a driving means for discharging the fluid in the fluid chamber 114, instead of the thermal driving method using the first heater 118, other various driving means may be used. For example, a piezoelectric drive means for providing a piezoelectric body (not shown) on the outer circumference of the fluid chamber 114 to discharge the fluid by deformation of the piezoelectric body may be used. Specifically, when a voltage is applied to the piezoelectric body, the piezoelectric body is deformed to change the volume of the fluid chamber 114, and accordingly, the fluid inside the fluid chamber 114 may be discharged through the nozzle 116. In addition, a driving means using a constant power can also be used. This is because by installing a membrane (not shown) in the fluid chamber 120 and placing the electrode adjacent thereto, the fluid is changed by the volume change of the fluid chamber 114 due to the deformation of the membrane due to electrostatic force between the electrode and the membrane. It is a method of discharging.

The reservoir 120 is provided in front of the nozzle 116 of the actuator 110 and has a diameter larger than the diameter of the nozzle 116. Accordingly, as will be described later, a pressure difference occurs between the fluid inlet 112 and the fluid outlet 122. The reservoir 120 is divided into a vapor phase (V) phase in which the fluid is present in the gas phase and a liquid phase (L) phase in which the fluid is present in the liquid phase. The gas phase region V is located at the nozzle 116 side, and the liquid phase region L is positioned at the fluid outlet 122 side. On the outer circumference of the gas phase region V of the reservoir 120, a second heater 124 is provided as a gas phase generating means for generating a gaseous fluid in the gas phase region V. FIG. The second heater 124 may be formed in an annular shape along the circumference of the gas phase region V of the reservoir 120, and a power is connected to the second heater 124. Accordingly, when power is applied to the second heater 124, the fluid in the gas phase region V of the reservoir 120 is heated and evaporated to generate a gaseous fluid. Accordingly, capillary force is generated by the surface tension applied to the interface between the fluid inside the nozzle 116 and the gas phase region (V).

Meanwhile, other means may be used instead of the second heater 124 as the gas phase generating means. For example, by placing a positive electrode and a negative electrode (not shown) on the outer periphery of the gas phase region (V) of the reservoir 120, by applying a voltage thereto, the fluid inside the gas phase region (V) of the reservoir 120 is electrolyzed Can produce fluid.

In the micropump 100 having the structure as described above, the fluid droplet D discharged from the nozzle 116 of the actuator 110 is moved to the liquid phase region L through the gas phase region V. . The discharge of the droplets D is repeated at a predetermined frequency, so that a predetermined amount of fluid flows out through the fluid outlet 122.

Hereinafter, a process of discharging droplets in the micropump having the above-described structure will be described in detail with reference to FIGS. 4A to 4L.

4A to 4L are diagrams showing the results of numerical analysis of elapsed time by which droplets are discharged from the micropump shown in FIG. 3. In this numerical analysis, the diameter of the nozzle is 10 μm and the diameter of the reservoir is 100 μm. The pressure difference between the fluid inlet and the fluid outlet is 10 kPa, which is determined according to the diameter of the nozzle and the reservoir as described later.

In FIG. 4A, when a pulse current is applied to the first heater disposed around the fluid chamber, the fluid inside the fluid chamber is heated to generate bubbles. Subsequently, as shown in FIG. 4B, the bubble expands due to the heat energy supplied from the first heater, and accordingly the fluid flows from the nozzle toward the gas phase region formed in front of the nozzle by the second heater disposed on the outer circumference of the reservoir. It starts to be discharged. The discharge proceeds due to the expansion of the bubble until t = 2.0 kPa (FIG. 4C), and at t = 3.0 kPa, the fluid is discharged by the surface tension between the gaseous fluid present in the reservoir and the liquid fluid discharged. The portion is tapered (FIG. 4D). At t = 4.0 kV, the volume of the bubble becomes maximum (FIG. 4E), and from then on, the volume of the bubble decreases rapidly (FIG. 4F). As a result, the rear end of the fluid droplet that has already been discharged becomes thinner and thinner, and when the bubble completely disappears at t = 7.0 kPa, the fluid droplet is separated from the fluid chamber (FIG. 4G). The droplets gained momentum by the expansion force of the bubble continue to be inertial force even after being separated from the fluid chamber (FIG. 4H) and flow into the liquid phase region at the time point t = 15 ms (FIG. 4I). As shown in FIGS. 4J and 4K, as time passes, the sub-droplets along the main droplets are introduced into the liquid region, and thus the interface of the liquid region is shaken by the momentum of the introduced droplets. At the same time, the capillary force formed between the gas phase in the reservoir and the fluid in the nozzle causes the surface of the fluid to move to the top of the nozzle as in the initial state, and this force induces the inflow of fluid from the fluid inlet to the fluid chamber. As shown in FIG. 4L, at the time t = 30 ms, the refilling of the fluid into the fluid chamber is completed, and the imperfection of the front liquid region is also reduced to return to the initial state to proceed with the next cycle.

In the above numerical analysis, the diameter of the main droplets discharged through the nozzle is about 12 mu m, which corresponds to a volume of about 0.9 liter (pico liter). If the period at which the next cycle starts after the discharge of the droplets is set to about 50 Hz, the discharge frequency is 20 Hz. Therefore, when 0.9 pL of droplets per unit discharge are discharged at a frequency of 20 Hz, the flow rate per nozzle is 1.09 µL / min. As described above, according to the micropump according to the present invention, the volume of the droplets discharged through the fine nozzle is kept very small and constant in picolitre units.

5 is a graph showing the pressure head of the micro pump according to the diameter of the nozzle and the reservoir shown in FIG.

Referring to the graph of FIG. 5, it can be seen that the pressure head ΔP increases as the diameter R of the reservoir increases with respect to the diameter r of the nozzle, which can be expressed by Equation 1 below.

Where σ represents the surface tension of the fluid and θ represents the contact angle at the boundary between the liquid phase and the gaseous phase.

In the case of a general pump, the pressure head decreases as the flow rate increases, and the pressure head changes as the flow rate increases as the flow rate decreases. However, according to the micro-pump to which the microstructure according to the present invention is applied, As the pressure head is determined by the diameter of the nozzle and the reservoir, there is an advantage in that the pressure fluctuation is small depending on the flow rate.

In this principle, when there is no discharge of the droplet from the actuator, the microstructure according to the present invention can serve as a fluid valve to withstand the pressure of the fluid outlet higher than the fluid inlet. That is, when there is a gas phase region of the reservoir generated by the second heater, the fluid does not flow back from the fluid outlet toward the fluid inlet even if a reverse pressure of about 10 kPa is applied by the capillary force. On the other hand, when the power supply to the second heater is blocked to remove the gas phase region of the reservoir, the fluid flows back according to the pressure gradient present in the flow path.

In the above, the configuration and operation principle of the unit structure of the microstructure according to the present invention have been described, and various modified applications are possible according to the combination of the unit structures.

6 is a schematic perspective view showing a micropump having a plurality of nozzles as a second preferred embodiment of the present invention.

The micropump 200 shown in FIG. 6 has a plurality of nozzles 216 arranged in parallel with one reservoir 220. Each of the plurality of nozzles 216 is provided with, for example, a heater or a piezoelectric body as driving means for discharging the fluid chamber and the fluid as shown in FIG. 3. The reservoir 220 includes a gas phase region V and a liquid phase region L, and a heater or an electrode is disposed on the outer circumference of the gas phase region V as a gas phase generating means. That is, the embodiment shown in FIG. 6 is the same as the first embodiment described above, except that a plurality of actuators are arranged in parallel in one reservoir 220.

As described above, when the plurality of nozzles 216 are arranged in parallel, the unit time flow rate of the fluid flowing through the fluid inlet 212 and flowing out through the fluid outlet 222 is arranged to be greater than the flow rate discharged through the unit nozzle. The number of nozzles 216 is increased by the number of times. In addition, the pressure head that can be generated by the micro pump 200 also increases as R / r increases as in Equation 1 above.

As described above, according to the present invention, precise control of the flow rate is possible at the resolution of the picoliter by adjusting the discharge frequency and the quantity of the actuators based on a constant flow rate through the unit nozzle.

7 is a plan view showing a microstructure applied to a microvalve as a third preferred embodiment of the present invention.

As shown in FIG. 7, when a plurality of microstructures 300a, 300b, and 300c according to the present invention are connected in series, a pressure head of approximately 10 kPa is obtained in each unit structure 300a, 300b, and 300c, respectively. Therefore, the pressure head may be increased by the number of the unit structures 300a, 300b, and 300c connected in series. Each of the plurality of unit structures 300a, 300b, and 300c has a structure as shown in FIG. 3, that is, a reservoir 320a and 320b having actuators 310a, 310b, and 310c, a gas phase region, and a liquid phase region (L). , 320c). When such a structure is applied to the microvalve 300, the number of unit structures 300a, 300b, and 300c may be selected as necessary to form the microvalve 300 capable of operating under various pressures. That is, as described above, when the gas phase region V exists in each of the reservoirs 320a, 320b, and 320c, the flow of fluid is blocked, and when the gaseous region V of each of the reservoirs 320a, 320b, and 320c is removed, the flow path The fluid flows back according to the pressure gradient present at.

As described above, according to the present invention, since the pressure generated in the micropump and the microvalve can be adjusted, this structure serves as a pressure regulator or a check valve in the fluid system. can do.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

As described above, the microstructure according to the present invention can be configured in a smaller size than the prior art so that it can be applied to the MEMS structure, there is an advantage that has a high energy efficiency. In addition, since the volume of the droplets discharged per unit nozzle is very small and constant, there is an advantage in that the flow rate of the small amount can be efficiently controlled by controlling the number of nozzles and the discharge frequency. In addition, it can be used as a basic element of the fluid system because it has the same structure and can simultaneously perform the roles of the pump and the fluid valve, and can be applied to the pressure regulator or the check valve as it can maintain a constant pressure head regardless of the flow rate of the pump. Can be.

Claims (13)

An actuator for discharging the fluid introduced from the fluid inlet through a nozzle at a predetermined frequency; It is formed in a diameter larger than the diameter of the nozzle in front of the nozzle, has a fluid outlet through which the fluid flows, the inner space is where the fluid is in the gaseous phase and the gaseous region located on the nozzle side and the fluid is in the liquid phase A reservoir divided into a liquid phase region located at a side of the fluid outlet; And And meteorological generation means provided on an outer circumference of a gas phase region of the reservoir to generate a gaseous fluid in the gas phase region. The method of claim 1, The actuator is a fluid chamber connected to the fluid inlet on the downstream side and the nozzle is connected to the upstream side and the driving means is provided on the outer periphery of the fluid chamber to provide a driving force for discharging the fluid through the nozzle. A microstructure comprising: The method of claim 2, And the driving means has a first heater that generates bubbles by heating the fluid inside the fluid chamber. The method of claim 3, wherein The first heater is a microstructure, characterized in that formed in an annular wrap around the outer periphery of the fluid chamber. The method of claim 2, And said driving means has a piezoelectric body which changes the volume of said fluid chamber by being deformed by an applied voltage. The method of claim 1, And said gas phase generating means has a second heater for generating a gaseous fluid by heating and evaporating a fluid inside a gaseous region of said reservoir. The method of claim 6, And the second heater is formed in an annular shape surrounding the outer circumference of the gas phase region of the reservoir. The method of claim 1, And said gas phase generating means has an electrode which electrolyzes a fluid inside a gaseous region of said reservoir to produce a gaseous fluid. 9. A micropump in a fluid system, comprising the microstructure of any one of claims 1-8. The method of claim 9, And the actuators of the microstructures are arranged in parallel in a single reservoir. 9. A fluid valve of a fluid system, comprising the microstructure of any one of claims 1-8. The method of claim 11, And said microstructures are connected in series. 9. A pressure regulator of a fluid system, comprising the microstructure of any one of claims 1-8.