JP2008223684A - Micropump and liquid flow forming method using temperature difference marangoni effect - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micropump providing low resistance against a flow, requiring no movable section, and easily structured, by using a temperature difference Marangoni effect. <P>SOLUTION: This micropump for generating a liquid flow by using the temperature difference Marangoni effect has: a passage member 10 having at least one passage which has a liquid inlet 11 to which liquid 40 is fed and a liquid outlet 12 from which the liquid 40 is fed and in which the liquid fed from the liquid inlet is led to flow toward the liquid outlet; and temperature gradient forming means 20, 30 which are arranged to the passage member 10 and form, along the passage, a temperature gradient reduced flately from the side of the liquid inlet toward the side of the liquid outlet. The passage member 10 is so configured that a single free surface 40A continued along the passage leading from the liquid inlet to the liquid outlet is formed in a passage direction on the liquid 40 circulated into the passage member. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a micropump and a liquid flow generation method utilizing a temperature difference Marangoni effect.

  A micropump is known as a pump that generates a liquid flow by driving a small amount of fluid in one direction, and is intended for use in fields such as medical treatment and chemical analysis. Various systems such as an ultrasonic type, a rotary type, and a magnetic fluid type are known. Among them, a diaphragm type micropump is known as one suitable for practical use.

  Conventionally known micropumps such as diaphragm type micropumps use “volume force” to drive the liquid. Since the body force is “proportional to the volume of the driven fluid in the drive unit”, it is proportional to the dimension of the drive unit: L 3. For this reason, when the dimension of the drive part is large to some extent, the liquid can be driven effectively, but when the dimension of the drive part: L becomes small, the volume force as the drive force is rapidly reduced. Further, it is necessary to deform the diaphragm. However, if the size of the driving unit is very small, it is difficult to realize a diaphragm that can be deformed and driven.

In view of such circumstances, it is conceivable to use the “area force” that becomes dominant when the dimensions of the drive unit become smaller as the drive force, and a micropump that uses the temperature difference Marangoni effect as the surface force is proposed. (Non-Patent Documents 1 and 2).
The inventors previously conducted research on a novel micropump using the temperature difference Marangoni effect at a research meeting “Thermal Engineering Conference” held by the academic society “The Japan Society of Mechanical Engineers”. ) ”.

  Non-Patent Document 1 describes that a plurality of “ribs by thermoelectric elements” are immersed in the liquid so as to be orthogonal to the flow path from above the liquid flow path, and the free surface of the liquid is exposed between the ribs. A temperature gradient is formed between the ribs on the liquid surface, and a liquid flow is generated in the flow path due to the temperature difference Marangoni effect, but the ribs are arranged so as to be orthogonal to the liquid flow and immersed in the liquid. Therefore, it is considered that there is a problem that viscous frictional resistance is generated at the rib portion with respect to the generated liquid flow, and the liquid flow is suppressed.

  Non-Patent Document 2 describes that a liquid is passed through the flow path as a whole, two heat sources are provided along the flow path, and the free surface of the liquid (gas-liquid) is boiled by heating in the flow path of one heat source. The temperature gradient along the flow path is controlled by the other heat source, and a liquid flow is generated by utilizing the temperature difference Marangoni effect generated on the free surface. I need.

The Japan Society of Mechanical Engineers Thermal Engineering Conference Proceedings (2003, pages 439-440) Microactuators using Marangoni effect by thermoelectric elements Tech Dig IEEE Micro Electro Mech Syst Vol.15 PP109〜112 2002 (FABRICATION AND PERFORMANCE TESTINNG OF A STEADY THERMOCAPILLARY PUMP WITH NO MOVING PARTS) Proceedings of Thermal Engineering Conference (No.06-2 2006 PP167-168)

  The present invention has been made in view of the above-mentioned circumstances, and utilizes the temperature difference Marangoni effect, has little resistance to flow, does not require a movable part, realizes a micropump with a simple structure, and provides such a micropump. It is an object of the present invention to realize a method for generating a liquid flow using the method.

The micropump of the present invention is as follows.
1-1. A “micropump that generates a liquid flow using the temperature difference Marangoni effect”, and includes a flow path member and a temperature gradient forming unit.
The “flow path member” has a liquid inlet to which a liquid is supplied and a liquid outlet to send out the supplied liquid, and has a flow path in which the liquid supplied from the liquid inlet flows toward the liquid outlet. In addition, the channel member is disposed as “a part of the liquid channel” in the liquid channel through which the liquid flows. The liquid fills the entire liquid flow path, and is driven by the “temperature difference Marangoni effect” in the flow path member portion to generate a liquid flow in the entire liquid flow path.

“Temperature gradient forming means” is means for forming a “temperature gradient in which the temperature monotonously decreases from the liquid inlet side toward the liquid outlet side” along the flow path in the flow path member.
The flow path member is configured so that “a single free surface is formed in the flow path direction that is continuous along the flow path from the liquid inlet to the liquid outlet” with respect to the liquid flowing through the flow path member. Has been.
That is, the free surface is continuous along the flow path and is not interrupted. Moreover, it is single in the flow path direction. “The free surface is single in the flow path direction” means that when there is one flow path in the flow path member, a single free surface is continuously formed along the flow path. When there are two or more channels in the channel member, a “single and continuous free surface” is formed along each channel in each channel.

  “The free surface formed along the flow path, continuous along the flow path, and single in the flow path direction” preferably extends over the entire length of the flow path from the liquid inlet to the liquid outlet. What is necessary is just to form in most parts (for example, area | region of 80% or more of flow path length) of the flow path from a liquid inlet to a liquid outlet.

  As described above, in the micropump of the present invention, the “temperature gradient in which the temperature monotonously decreases from the liquid inlet side to the liquid outlet side” is formed by the temperature gradient forming means, and the liquid is simply set in the flow path member. Since one free surface is continuously formed along the flow path, a continuous temperature gradient can be formed on this free surface. Therefore, by effectively generating the temperature difference Marangoni effect on the free surface, A liquid flow can be generated. Further, since there is no “structure for preventing the liquid flow due to the temperature difference Marangoni effect” in the flow path member, there is no problem of liquid flow suppression. Further, since the liquid is driven by the temperature difference Marangoni effect, no movable part is required for driving the liquid.

  The temperature gradient forming means may form a “temperature gradient in which the temperature monotonously decreases from the liquid inlet side to the liquid outlet side” along the flow path in the flow path means, and there is one heat source for heating. But you can. Further, unlike the case of Non-Patent Document 2, it is not necessary to forcibly form a free surface (gas-liquid boundary surface) by heating, so that large heating energy is not required.

The channel member in the micro pump of 1-1 may be “having a structure in which one or more channels are penetrated from the liquid inlet side to the liquid outlet side” (1-2).
In the micropump of 1-2, the flow path member may be “one having two or more flow paths spaced from the liquid inlet side toward the liquid outlet side” (1-3).

  The flow path member in the 1-2 micropump can also be "one or more ribs projecting from the upper side of the flow path toward the bottom of the flow path are formed in parallel with the flow path direction" ( 1-4) In this case, “one or more ribs projecting from the channel upper side of the channel member toward the channel bottom may contact the channel bottom” (1-5) The tip of one or more ribs protruding from the upper side of the channel of the road member toward the bottom of the channel can be immersed in the liquid flowing in the channel (1-6). The tip of one or more ribs protruding from the upper side of the channel of the path member toward the bottom of the channel may be in contact with the liquid level of the liquid flowing in the channel (1-7).

  In the case of the above 1-6 and 1-7, since the bottom of the flow path formed in the flow path member is passing through, the flow path is single, but one or more ribs are in contact with the free surface Alternatively, by immersing in the liquid, the free surface is separated by the ribs to become two or more free surfaces. In this case as well, each separated free surface is “continuous along the flow path, Single in direction ".

  Any of the micro pumps of 1-2 to 1-7 described above can have a “flow channel member having an integral structure of a single material” (1-8).

  Further, any of the micro pumps of 1-2 to 1-7 described above can be "the flow path member is configured by combining the upper flow path member and the lower flow path member vertically" (1-9). In the case “the upper flow path member may have one or more ribs protruding from the upper side of the flow path toward the flow path bottom (1-10).

  The micro pump of 1-9 or 1-10 is “the temperature gradient forming means heats and cools the upper flow path member, and the upper flow path member is made of a material having higher thermal conductivity than the liquid to be circulated. Configuration ”(1-11). Note that the lower flow path member is preferably made of a material having lower thermal conductivity than the liquid to be circulated.

Any of the micropumps 1-1 to 1-11 can have at least a “heater in which the temperature gradient forming means overheats the liquid inlet side” (1-12).
Any of the micropumps 1-1 to 1-12 can have "the temperature gradient forming means has a cooling means for cooling the outlet side" (1-13). In this case, a “Peltier element” can be suitably used as the cooling means (1-14). Thus, when using a Peltier element as a cooling means, it has a heat conducting member that conducts heat generated on the heat radiation side of the Peltier element to the liquid inlet side, and uses the Peltier element and the heat conducting member as “at least part of the heater”. (1-15).

  The temperature gradient forming means can be used without any limitation as long as it can form a temperature gradient in which the temperature decreases monotonously from the liquid inlet side toward the liquid outlet side along the flow path of the flow path member. . When a heater that superheats the liquid inlet side is used as in 1-12 above, it is necessary to efficiently remove from the liquid the “heat transported by the liquid flow heated by the liquid inlet side” on the liquid outlet side. . “How much heat should be removed” depends on the size of the micropump and the amount of liquid flowing.

  If the amount of liquid flowing is small, “natural heat radiation or heat radiation by heat radiation fins” may be sufficient on the liquid outlet side of the flow path. However, in general, it is preferable to heat the liquid inlet side and actively cool the liquid outlet side with a cooling means such as a Peltier element.

  As the cooling means, in addition to the Peltier element, “one that performs cooling with a coolant or cooling air” may be used. The Peltier element has a cooling part on one side and a heat radiating part on the other side, so that two elements of cold and heat are generated in one element. When using a Peltier element, the Peltier element radiates heat as in 1-15 above. The heat generated on the side can be conducted to the liquid inlet side by the heat conducting member, and a heater can be constituted by this heat conducting member and the Peltier element, or can be used for heating the liquid inlet side in combination with other heaters.

  Moreover, the cross-sectional shape of the flow path in the flow path member can be various shapes including a rectangular shape. There is no particular limitation as long as the liquid to be distributed can generate the “temperature difference Marangoni effect necessary for driving”, and a wide variety of liquids such as silicone oil, clean water, alcohol liquid, oil, and chemical liquid are distributed. be able to.

Since the flow rate can be controlled by controlling the temperature gradient formed in the flow path member, the micropump of the present invention can be suitably used for “dividing and converging chemical reaction solution, DNA test solution, drug solution, etc.” it can. In addition, the micro pumps 1-1 to 1-15 can be used in parallel to generate a plurality of liquid flows having the same or different flow rates, and the plurality of micro pumps are connected in series in the flow direction. It is also possible to increase the driving force by arranging in the above.
The liquid flow generation method 1-16 is a method of generating a liquid flow using any one of the micropumps 1-1 to 1-15.

  As described above, according to the present invention, the temperature difference Marangoni effect is effectively used, the resistance to the flow is small, the movable part for applying the mechanical driving force is not required, and the structure is simple. A pump can be realized, and a method of generating a liquid flow using such a micro pump can be realized.

Hereinafter, embodiments will be described.
FIG. 1 is a diagram for explaining an embodiment of a micropump.
In FIG. 1A, reference numeral 10 denotes a flow path member, reference numeral 20 denotes a heater, reference numeral 30 denotes a cooling means, and reference numeral 40 denotes “liquid to be circulated”. The flow path member 10 has a liquid inlet 11 to which the liquid 40 is supplied and a liquid outlet 12 for sending out the liquid 40. The liquid inlet 11 and the liquid outlet 12 are connected to a liquid flow path 50.

  The liquid 40 is supplied from the liquid flow passage 50 to the liquid inlet 11, communicates with the liquid outlet 12 via the flow path 10 </ b> A of the flow path member 10, and further communicates with the liquid flow path 50. A free surface 40 </ b> A is formed in the liquid 40 in the flow path 10 </ b> A. As shown in the figure, the formed free surface 40A is “continuous along the flow path 10A from the liquid inlet 11 to the liquid outlet 12 and is single in the flow path direction”.

  In the state of FIG. 1A, the heater 20 generates heat to superheat the liquid inlet 11 side of the flow path member 20, and the cooling means 30 (in this embodiment, “Peltier element” is used). When the outlet side is cooled, a “temperature gradient in which the temperature decreases monotonously from the liquid inlet side toward the liquid outlet side” is forcibly formed. That is, in the embodiment of FIG. 1A, the heater 20 and the cooling means 30 constitute a “temperature gradient forming means”.

Before proceeding with the description, the state of the flow path in the flow path member 10 will be described.
As described above, the channel can be formed so that “one or more channels pass through” from the liquid inlet side to the liquid outlet side. The cross-sectional shape of each of the one or more flow paths may be various shapes such as a rectangular shape, a circular shape, an elliptical shape, and a polygonal shape.

Two typical examples of these are shown in FIGS. 1B and 1C.
In the flow path member 100 shown in FIG. 1B, a flat bottom plate 101 made of “material having low thermal conductivity such as glass or resin” is used as a lower flow path member, and the upper flow path member 102 extends from above the bottom plate 101. It is covered. The upper flow path member 102 is formed of a material having high thermal conductivity such as a metal or an alloy, and a plurality of ribs Lb1, LB2,... Are uniform on the lower surface in FIG. Projecting in a cross-sectional shape, a gap between adjacent ribs is a “groove having a rectangular cross section”.

  The free ends of the ribs LB1 and the like are in contact with the surface of the bottom plate 101. In this state, the bottom plate (lower flow path member) 101 and the upper flow path member 102 are integrated with each other by means such as adhesion, and as shown in the figure, the cross section is rectangular. The plurality of flow paths (four in the example in the figure) penetrate in a direction orthogonal to the drawing. Each flow path is separated from each other, and the liquid 40 continuously forms along the flow path within each flow path to form a single free surface 40A.

  In the flow path member 110 shown in FIG. 1C, a flat bottom plate 111 made of a material having low thermal conductivity such as glass or resin is used as a lower flow path member, and the upper flow path member 112 is covered from above the bottom plate 111. It has been. The upper flow path member 112 is formed of a material having high thermal conductivity such as a metal or an alloy, and a plurality of ribs Lb11, LB12... Are uniformly formed in a direction perpendicular to the drawing on the lower surface in FIG. It is provided with a “groove having a rectangular cross section” between adjacent ribs.

  Among these ribs, the ribs Lb10 and Lb20 at the left and right ends in FIG. 1C are higher than the other ribs. Accordingly, the covered upper flow path member 112 is in contact with the bottom plate 111 at the tip ends of the ribs Lb10 and Lb20, and is integrated with each other by means such as adhesion. Therefore, the “lower surface (upper surface of the bottom plate 111) passes through the bottom in common, and the upper portion is separated by the ribs Lb11, Lb12,... It penetrates with a uniform cross-sectional shape.

  In this flow path, the upper surface of the liquid 40 is in contact with the tips of the ribs Lb11, Lb12,. For this reason, the free surface 40A separated by the ribs Lb11, Lb12,.

  As a modification of the flow path member in FIG. 1 (c), the ribs Lb11, lb12,... You may do it. Alternatively, on the contrary, the heights of the ribs LB11, Lb12,... May be reduced so that the tips of the ribs Lb11 and the like face the free surface of the liquid 40. As the limit in this case, if the height of the ribs Lb11 and the like is set to 0, the cross-sectional shape of the flow path becomes a single horizontally long rectangular shape.

  Further, in FIGS. 1B and 1C, the lower flow path member and the upper flow path member are made of different materials, and these are combined into a flow path member. However, FIGS. It is also possible to adopt a configuration in which the flow paths having various cross-sectional shapes described in 1 are formed in a single material.

Needless to say, the flow path member 100 in FIG. 1B or the flow path member 110 in FIG. 1C can be used as the flow path member 10 in FIG.
In the example shown in FIGS. 1B and 1C, the number of channels is drawn as four in the example shown in FIGS. 1B and 1C, and this is an explanatory example. There is no particular limitation on the number of flow paths, and the number of flow paths can be set from 1 to several hundreds, or thousands or more, according to the specifications of a specific micropump. The size of the cross section of the flow path is also arbitrary as long as the condition that “the temperature difference Marangoni effect capable of driving the liquid effectively on the formed liquid free surface can be generated” is satisfied. Non-Patent Document 2 described above discloses “width: channel of 100 μm”.

  As described above, the “temperature difference Marangoni effect” as an area force becomes more dominant and effective as the action region becomes smaller. Considering this point, the flow path width is about several μm to several mm. Can be set as appropriate over a wide area.

Returning to FIG. 1A, the flow path member 10 is heated by the heater 20 and cooled by the cooling means 30, and the temperature of the flow path member 10 is monotonically from the liquid inlet side to the liquid outlet side. When a decreasing temperature gradient is formed, heat is transmitted to the liquid 40 from the portion heated to high temperature by heating through the ribs and the side wall of the flow path, and the liquid 40 also flows from the liquid inlet 11 side to the liquid outlet 12 side of the flow path. A temperature gradient that decreases toward the surface is generated, and a “surface temperature gradient along the flow path” also occurs on the free surface 40A.
As is well known, the surface tension of the liquid surface varies with the liquid surface temperature, and the higher the surface temperature, the smaller the surface tension.
In the flow path 10A of the flow path member 10, when the temperature of the free surface 40A of the liquid 40 decreases from the liquid inlet side to the liquid outlet side as described above, the surface tension on the free surface 40A is large on the liquid outlet side, It becomes smaller on the liquid inlet side. For this reason, the free surface 40A is pulled toward the “liquid outlet side having a larger surface tension”, and a surface flow is generated by this tensile force. The surface flow thus generated pulls the liquid portion below the surface due to the viscosity of the liquid 40, and eventually "a steady flow having a velocity gradient in the depth direction of the liquid 40" is generated.

  The above is a qualitative explanation of “liquid flow due to temperature difference Marangoni effect”. In FIG. 1A, since the liquid 40 flowing into the flow path 10A is preheated by the heater 20 in the flow passage 50, local backflow at the inlet is prevented.

  The inventors use the flow path member 100 shown in FIG. 1 (b) and the flow path member 110 shown in FIG. 1 (c) as the flow path member 10 of the micro pump as shown in FIG. 1 (a). And the properties of the liquid flow were investigated by simulation. This will be described below. In the following, the case where the flow path member 100 of FIG. 1B is used as the flow path member is referred to as “system 1”, and the case where the flow path member 110 of FIG. 1C is used is referred to as “system 2”.

  FIG. 2A is a simulation model of the flow path member 100 in the system 1, and the symbol LB is a model of the two adjacent ribs Lb1, Lb2 and the like in FIG. The lower end shown in the figure is in contact with the surface of the bottom plate. The bottom plate surface was a heat insulating surface. In addition, the distance h between the bottom plate surface and the free surface of the liquid 40 in the flow path was set to 1 mm.

FIG. 2B is a simulation model of the flow path member 110 in the system 2, and reference numeral LB1 is a model of the two adjacent ribs Lb1, Lb2, etc. in FIG. It is arranged at 1 mm, and the lower end is in contact with the liquid surface. The bottom plate surface was a heat insulating surface. In addition, the distance h between the bottom plate surface and the free surface of the liquid 40 in the flow path was set to 1 mm.
In the simulation, it was assumed that “the liquid does not slide against the rib surface / flow channel bottom”.

  As the “dominance equation” for the liquid, “continuity equation, Navier-Stokes equation, energy equation” was used. As the “liquid”, “2cSt silicone oil” was assumed, and as the ribs LB and LB1, “brass” was assumed, and these physical property values were used. In addition, the free surface of the liquid in the channel is in contact with air.

“Marangoni number: Ma” characterizing the temperature difference Marangoni effect is the surface tension temperature coefficient of the liquid (in the example being described, 2cSt silicone oil): γ, temperature conductivity: k, viscosity coefficient: μ, temperature gradient : DT / dx (x is the direction along the flow path and the flow direction is positive), and the typical length of the driven liquid is h (the distance between the bottom surface of the flow path and the free surface).
Ma = {γ / (μk)} | dT / dx | h ²
Defined by

That is, the Marangoni number: Ma increases as the temperature gradient and the surface tension temperature coefficient increase, and decreases as the viscosity coefficient and temperature conductivity increase.
Typical flow rate of liquid flow through the flow path of the simulation model: Q ₀
Q ₀ = {γ / μ} | dT / dx | h ³
Define in. That is, the representative flow rate is Marangoni number: Ma and Q ₀ = Ma · kh
Are in a relationship.

The actual flow rate is Q, and the ratio between this flow rate: Q and the representative flow rate: Q ₀ is called the specific flow rate: Q ′ (= Q / Q ₀ ).
FIG. 2C shows the relationship between the specific flow rate (vertical axis) and the Marangoni number (horizontal axis).
Reference numeral S1 indicates the system 1 and reference numeral S2 indicates the system 2.

  In the system 1, the specific flow rate is stable in a wide change region of Marangoni number, but the actual flow rate is less than 40% of the representative flow rate. On the other hand, in the system 2, the actual flow rate is 80% or more of the representative flow rate.

In FIG. 2C, when comparing the non-flow rate with respect to the same Marangoni number, the system 2 has a size almost twice as large as that of the system 1. As described above, the representative flow rate: Q ₀ is the product of the Marangoni number: Ma, the representative length: h, and the temperature conductivity: k. In the system 1 and the system 2, k and h are equal to each other. Therefore, when the Marangoni numbers are the same in the systems 1 and 2, the representative flow rates are the same in the system 1 and the system 2.

From this, in FIG. 2C, it is meant that the actual flow rate for the same Marangoni number is about twice as large as that of the system 1 in the system 2.
Comparing the system 1 and the system 2, the contact area between the liquid 40 and the rib is larger in the system 1 than in the system 2. Therefore, the viscous resistance at the contact surface between the rib and the liquid 40 is increased in the system 2. The inventors consider that the magnitude of the actual flow rate: Q is generated in the system 1 and the system 2 due to this.

FIG. 2D shows the relationship between the actual flow rate (vertical axis) and the temperature gradient (K / m).
Reference numeral S1 indicates the system 1 and reference numeral S2 indicates the system 2.

From this figure, it can be seen that in both systems 1 and 2, the actual flow rate: Q increases almost linearly as the temperature gradient increases.
That is, by controlling the temperature gradient formed in the flow path member, the flow rate flowing through the flow path can be controlled. This is mainly because the Marangoni number increases in proportion to the temperature gradient. In FIG. 2D, the fact that the inclination in the system 2 is larger than the inclination of the relationship of the system 1 corresponds to that the specific flow rate in the system 2 is larger than that in the system 1.

  Further, in the system 1, the liquid surface temperature distribution in the steady state and the state of streamlines on the free surface were examined. FIG. 3A shows three isotherms and eight streamlines. In FIG. 3A, the x direction is the flow path direction, and the Z direction is parallel to the free surface and perpendicular to the x direction.

Curves indicated by reference signs T1, T2, and T3 are isotherms, and the temperature decreases in the order of T1, T2, and T3. What is shown in the figure is a region at a substantially central part of the flow path, and as shown in the figure, the temperature is high at the central part in the Z direction, and the temperature is low at both end parts in the Z direction. Since the liquid is heated by the flow path member (rib) on the liquid inlet side of the flow path, the temperature rises at the rib portions (both ends in the Z direction) on the liquid inlet side. As it flows, the temperature gradually decreases in contact with the “low temperature portion” of the rib, so in the central region of the flow path, the temperature at the central portion in the Z direction is higher than that at both ends in the Z direction as shown in FIG. As a result, a “surface temperature distribution” that is high in temperature is generated.
In Fig.3 (a), the curve shown by code | symbol SL11-SL14, SL21-SL24 is a streamline, and these streamlines are orthogonal to an isotherm.
As can be seen from the state of the isotherm in FIG. 3A, the temperature gradient is generated in the z direction as well as the x direction. Therefore, as in the streamlines SL11, SL12, SL13, SL21, SL22, SL23, Z A surface flow toward both ends (rib positions) of the direction is generated, but at the same time, a surface flow toward the x direction (flow path direction) is also generated like the flow lines SL14 and SL24. In addition, each stream line has a component in the x direction. Therefore, a “surface flow in the x direction as a whole” occurs on the liquid free surface.

  In addition, when “the state of streamlines in a cross section perpendicular to the flow path direction” was examined in a state where the flow was stable, it was as shown in FIG. That is, the liquid flows so as to rotate with the position of the central portion (Z = 0.5) in the Z direction as a symmetry plane. This is a convection caused by a surface flow from the central portion in the Z direction toward both ends in the Z direction, such as the streamlines SL11, SL12, SL21, and SL22 in FIG.

  Therefore, it can be seen that the flow of the liquid in the flow path as a whole is "a spiral flow that is mirror-symmetrical to each other and flows in the flow path direction as a whole" as shown in FIG.

  As a result of the simulation, it was found that if the Marangoni number becomes too large, the steadiness of the flow is lost and the oscillating flow is generated. In other words, the flow velocity oscillates with a periodic period and amplitude in an arbitrary cross section perpendicular to the flow. The liquid flow in the micropump is preferably steady, and from this point of view, the oscillating flow impairs the stability of the micropump.

  The Marangoni number is related to the change from steady flow to oscillating flow, and this relationship is similar to “Reynolds number is related to change from laminar flow to turbulent flow”. Incidentally, the critical Marangoni number when changing from a steady flow (the aforementioned spiral flow) to an oscillating flow is between Ma = 2000 and 2500 in the system 1, and in the case of the system 2, Ma = 800 to 1000. It was confirmed to be in between. Therefore, such a critical Marangoni number is considered to give "the upper limit of the temperature gradient that can be stably operated depending on the liquid type to be circulated".

  Next, the system 2 model is actually manufactured as an apparatus under the “same conditions as in the simulation”, 2cST silicone oil is used as the liquid 40, and the velocity in the y direction (the depth direction of the liquid) in the flow path is as follows. The change of was measured. In addition, the part of the baseplate was comprised with the bakelite which is a heat insulating material.

  The temperature gradient in the x direction of the rib as the flow path member: −258.7 K / m, Marangoni number: Ma = 149.3, and SBX-17 was used as tracking particles for measuring the flow velocity.

  In a portion where the liquid flow is stable, the xy cross section was set to z = 0.5 mm (center in the width direction of the flow path), and the flow velocity in the x direction was obtained with respect to y.

The results are shown in FIG. The vertical axis is y, and the horizontal axis is the flow velocity in the x direction. Similar to the simulation, the flow velocity was 0 on the bottom plate surface where y = 0, and the flow velocity increased with increasing y to 0.0025 m / Sec (2.5 mm / Sec) at the free surface position. The curve is the calculated value by simulation, and the black circle is the measured value. It can be seen that the measurement results are in good agreement with the calculated values. From this figure, even if it is considered that the change in the flow velocity increases substantially linearly with y, no large error occurs. When calculated with such an approximation, the cross section of the liquid flow is 1 mm in width and 1 mm in depth, and the flow velocity is 0 to 2.5 mm / Sec in the y direction, so approximately 1.25 mm ³ per second per flow channel. Is obtained.

It is a figure for demonstrating one Embodiment of a micropump. It is a figure which shows the simulation model and simulation result of the micropump of FIG. It is a figure for demonstrating the flow obtained by simulation. It is a figure which shows the velocity distribution of the liquid flow in the flow path actually measured.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Flow path member 10A Flow path 11 Liquid inlet 12 Liquid outlet 20 Heater 30 Cooling means 40 Liquid 40A Free surface of liquid 40 100 Flow path member 110 Flow path member

Claims (16)

A micropump that generates a liquid flow using the temperature difference Marangoni effect,
A flow path member having a liquid inlet for supplying a liquid and a liquid outlet for delivering the liquid, and having one or more flow paths through which the liquid supplied from the liquid inlet flows toward the liquid outlet;
The flow path member has temperature gradient forming means for forming a temperature gradient in which the temperature monotonously decreases from the liquid inlet side toward the liquid outlet side along the flow path,
The flow path member is formed so that a single free surface is formed in the flow path direction continuous with the liquid flowing through the flow path member along the flow path from the liquid inlet to the liquid outlet. A micropump using the temperature difference Marangoni effect characterized by being configured. The micropump according to claim 1, wherein
A micropump using a temperature difference Marangoni effect, wherein the flow path member has a structure in which one or more flow paths are penetrated from the liquid inlet side to the liquid outlet side. The micropump according to claim 2, wherein
2. The micropump using the temperature difference Marangoni effect, wherein the flow path member has two or more flow paths separated from the liquid inlet side toward the liquid outlet side. The micropump according to claim 2, wherein
The flow path member is characterized in that one or more ribs protruding from the upper side of the flow path toward the flow path bottom are formed in parallel with the flow path direction. pump. The micropump according to claim 4, wherein
A micro pump using a temperature difference Marangoni effect, wherein one or more ribs projecting from a channel upper side of a channel member toward a channel bottom are in contact with the channel bottom. The micropump according to claim 4, wherein
A micro-device utilizing the temperature difference Marangoni effect, wherein the tip of one or more ribs protruding from the upper side of the flow channel toward the bottom of the flow channel is immersed in the liquid flowing in the flow channel pump. The micropump according to claim 4, wherein
Utilizing the temperature difference Marangoni effect, wherein the tip of one or more ribs protruding from the upper side of the channel member toward the bottom of the channel is in contact with the liquid level of the liquid flowing in the channel Micro pump. The micropump according to any one of claims 2 to 7,
A micropump using a temperature difference Marangoni effect, characterized in that the flow path member is an integral structure made of a single material. The micropump according to any one of claims 2 to 7,
A micropump using a temperature difference Marangoni effect, characterized in that the flow path member is configured by combining an upper flow path member and a lower flow path member vertically. The micropump according to claim 9, wherein
A micropump using a temperature difference Marangoni effect, wherein the upper flow path member has one or more ribs protruding from the upper side of the flow path toward the flow path bottom. The micropump according to claim 9 or 10,
The micropump using the temperature difference Marangoni effect, wherein the temperature gradient forming means heats and cools the upper flow path member, and the upper flow path member is made of a material having high thermal conductivity. The micropump according to any one of claims 1 to 11,
The micropump using the temperature difference Marangoni effect, characterized in that the temperature gradient forming means has at least a heater for heating the inlet side. The micropump according to any one of claims 1 to 12,
The micropump using the temperature difference Marangoni effect, characterized in that the temperature gradient forming means has a cooling means for cooling the outlet side. The micropump according to claim 13, wherein
A micropump using a temperature difference Marangoni effect characterized by using a Peltier element as a cooling means. The micropump according to claim 14, wherein
A micropump using a temperature difference Marangoni effect, comprising a heat conducting member for conducting heat generated on the heat radiation side of the Peltier element to the liquid inlet side, wherein the Peltier element and the heat conducting member are used as at least a part of a heater. .   The liquid flow production | generation method which produces | generates a liquid flow using the micropump of any one of Claims 1-15.

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