JP2010188265A - Droplet atomizing device - Google Patents

Abstract

An apparatus for atomizing generated droplets using a microfluidic chip is provided.
A droplet generation unit that generates a first droplet 1 from two kinds of liquids that do not mix with each other flowing in a microchannel of a microfluidic chip by a shearing force and an inner wall of a downstream portion of the channel A droplet splitting unit that generates a second droplet 1011 or 1012 by applying a voltage to at least the pair of drive electrodes 401 and 402 to split the droplet.
[Selection] Figure 1

Description

  The present invention relates to a droplet generation technique using a microfluidic chip.

  In recent years, a technique using a microfluidic chip has been proposed as a technique for generating microdroplets. A microfluidic chip is a device that has a minute flow channel with a width and depth of several tens to several hundreds of μm, and performs various liquid operations by supplying liquid to the flow channel. Two types of liquids that do not mix with each other are supplied into the microchannel, and either one of the liquids is sheared by the accompanying shearing force to generate droplets (Patent Documents 1 and 2). . The size of the generated droplet is approximately 0.5 to 2 times the channel width. Since the flow that shears the liquid is a stable laminar flow, the diameter distribution of the generated droplets is very small.

  On the other hand, electrowetting is known as a technique for manipulating a liquid. Electrowetting is a phenomenon in which an apparent contact angle of a liquid with respect to an electrode changes by applying a potential difference between the liquid on the electrode and the electrode (Non-Patent Document 1). A technique for generating droplets using this phenomenon has been reported (Patent Document 3, Non-Patent Document 2).

JP 2004-81924 JP JP 2004-98225 A Special Table 2006-500596

Frieder Mugele and Jean-Christophe Baret, “Electrowetting: from basics to applications”, J. Phys .: Condens. Matter, Vol.17 (2005), pp.R705-R774. Vijay Srinivasan, Vamsee K. Pamula and Richard B. Fair, “An integrated digital microfluidic lab-on-a-chip for clinical diagnostics on human physiological fluids”, Lab Chip, Vol. 4 (2004), pp. 310-315.

In the droplet generation technology using a microfluidic chip such as Patent Document 1 and Patent Document 2, there is a problem that there is a lower limit to the size of droplets that can be generated. In order to generate a small droplet, a small channel width corresponding to the droplet is required. The channel width d can be expressed by the following equation, where the channel pressure loss ΔP, the channel length l, μ is the liquid viscosity, and Q is the flow rate.
ΔP = 128μlQ / πd ⁴ (1)

The pressure loss ΔP of the flow path must be smaller than the pressure resistance of the microfluidic chip or the maximum pressure of the liquid feed pump. For example, when the maximum pressure loss ΔP of a syringe pump used for liquid feeding of a microfluidic chip is 0.5 Mpa, the liquid viscosity μ is 1 mPa · s and the channel length l is set as a condition for generating the smallest droplet. Assuming 200 μm and a flow rate Q of 1 × 10 ⁻¹¹ m ³ / s, the flow path width d is 11 μm. Therefore, in this case, a droplet smaller than 5.5 μm which is 0.5 times the channel width cannot be generated.

  On the other hand, the liquid suitable generation method using electrowetting described in Patent Document 3 and Non-Patent Document 2 is suitable for generating minute droplets because it can divide the droplets. There is a problem that the number of droplets generated is small. In this method, a droplet is injected from a liquid pool between two substrates with an interval of the order of 0.1 mm, and the electrodes are stretched by 0.5 mm in the horizontal direction with respect to the substrate by electrowetting. Generate droplets. That is, the droplets are charged by switching control of the electrode voltage, and are moved and split by electrostatic force. At this time, the ratio of the electrode pitch to the substrate interval needs to be smaller than about 0.2. The time required for the droplet to break up after the voltage is applied to the electrode is at least 30 mm / s, considering the resistance due to the viscosity of the droplet, etc. 17ms is required. Accordingly, the number of droplets generated per unit time is about 60 per second, and a sufficient amount cannot be supplied compared to the droplet generating method using the microfluidic chip.

  The present invention has been made in view of such circumstances, and produces finer droplets. In addition, the split droplet generation speed by electrowetting can be tracked to the order of several hundred Hz in synchronization with the generation speed of the droplet generated by the shearing force.

  In order to solve the above-described problem, the present invention moves a droplet generated by a shearing force in a microchannel of a microfluidic chip downstream using a flow field inside the channel, and downstream of the channel. In the flow field in Fig. 1, it is split perpendicularly to the channel wall surface by electrowetting.

  That is, the droplet atomization apparatus of the present invention includes a droplet generation unit that generates a first droplet by shearing force from two kinds of liquids that do not mix with each other flowing in a microchannel of the microfluidic chip, and the flow And a droplet splitting portion that generates a second droplet by applying a voltage to at least a pair of drive electrodes formed on the inner wall of the downstream portion of the path to split the droplet.

  Further, the droplet atomization apparatus of the present invention includes a droplet generation unit that generates a first droplet by shearing force from two kinds of liquids that do not mix with each other flowing in a microchannel of the microfluidic chip, and the flow It has a droplet splitting portion that generates a second droplet by changing the voltage of at least three electrodes formed on the inner wall of the downstream portion of the path by switching control to split the droplet.

According to the present invention, since the flow path width necessary for the liquid droplet splitting is approximately the same as that of the liquid droplet, it is possible to generate a finer liquid droplet without increasing the pressure loss of the flow path.
Further, the distribution of the droplet diameter after the division is almost equal to the distribution of the droplet diameter before the division.

  Furthermore, droplet breakup in the direction perpendicular to the wall surface due to electrowetting can follow up to the order of several hundred Hz. Therefore, it is possible to divide the droplets in synchronism with the generation rate of the droplets generated by the shearing force, and the number of droplets generated per unit time is about the same as the conventional one.

Basic configuration and operation principle of the present invention A method of splitting droplets by expanding the channel width A method of splitting droplets by continuously expanding the channel width Method of splitting a droplet in an oblique direction with respect to the flow path Method for controlling droplet contact angle after breakup Electrode arrangement in the flow path Method for controlling droplet contact angle after breakup Electrode arrangement in the flow path Adjustment method of droplet size after splitting Whole liquid atomization apparatus using the present invention

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be noted that this embodiment is merely an example for realizing the present invention, and does not limit the technical scope of the present invention. In each drawing, the same reference numerals are assigned to common components.

(Configuration of the entire device)
FIG. 10 is a schematic configuration diagram of the entire droplet atomization apparatus having the droplet generation unit and the droplet splitting unit of the present invention.

  The droplet atomization apparatus of the present invention includes a liquid 22 that is a raw material of a droplet and its medium 2, liquid feeding pumps 20 and 21 for feeding the liquid 22 and the medium 2, its control device 26, and the droplet 22. Pipes 18 and 19 for transporting the medium 2, a microfluidic chip 17 for generating and atomizing droplets, a power source 9 and its wiring 801 and 802 for controlling the microfluidic chip, and the generated droplets A pipe 24 for transportation and a collection container 25 for collecting the pipe 24 are provided.

  In addition, the microfluidic chip 17 splits the liquid droplets in the liquid droplet generation unit 304 that generates liquid droplets from the liquid 22 and the medium 2, the flow path 3 in which the generated liquid droplets and the medium flow, and the downstream part of the flow path 3. The liquid droplet splitting unit 305 is provided.

(Device operation)
In the droplet atomization apparatus having the above-described configuration, first, droplets are generated from the liquid 22 and the medium 2. The microfluidic chip 17 in which the flow path 3 is formed is connected to the liquid feeding pumps 20 and 21 by pipes 18 and 19. The pumps 20 and 21 send the liquid 22 which is the raw material of the droplets and the medium 2 respectively. From the liquid 22 and the medium 2 fed into the microfluidic chip 17, droplets are generated by the liquid shear force in the droplet generation unit 304 of the flow path 3.

  Next, the droplet is split by electrowetting in the droplet splitting portion 305 downstream thereof. The medium 2 containing the generated droplets is stored in the recovery container 25 through the pipe 24. The liquid feeding pumps 20 and 21 and the power source 9 are controlled by the control device 26 in synchronization with the flow speed and the voltage magnitude.

  In this way, the droplets generated by the shear force in the microchannel of the microfluidic chip are split perpendicularly to the channel wall surface by electrowetting in the flow field downstream of the channel. , Finer droplets can be generated. In addition, by performing shearing and splitting operations in a laminar flow in the same flow path, the split droplet generation rate by electrowetting can be reduced to the order of several hundreds of Hz synchronized with the generation rate of droplets generated by shearing force. It becomes possible to follow.

Hereinafter, the droplet splitting portion unique to the present invention using the electrowetting while having the above effect will be described in detail.
(Basic configuration and operating principle for droplet breakup)
The basic structure and operation principle of droplet breakup by electrowetting in the present invention will be described with reference to FIG. The liquid droplet 1 and the medium 2 around the liquid droplet are caused to flow inside the flow path 3 by a liquid feed pump connected to the outside of the flow path. The droplet 1 is in contact with the inner wall of the flow path 3. Drive electrodes 401 and 402 are formed on the surfaces of the two inner walls 701 and 702 facing each other in the flow path 3, and insulating films 501 and 502 having water repellency are further formed thereon. When the insulating films 501 and 502 do not have water repellency, they are covered with a water repellent film 6 not shown in FIG. The drive electrodes 401 and 402 are connected to the power source 9 by wirings 801 and 802, and the control circuit 26 switches the voltage according to time. The switching time can be appropriately adjusted according to the physical properties of the droplet and the medium. For example, when the droplet 1 is pure water, the medium 2 is silicone oil having a viscosity of about 1 mPa · s, and the flow path width (that is, the distance between the inner walls 701 and 702) is 11 μm, the switching switching time is 10 ms or more. Sufficient droplet breakup is possible.

When the voltage of the power source 9 is 0 volts, the contact angle of the droplet 1 with respect to the insulating films 501 and 502 is large (FIG. 1 (1)).
When the voltage of the power source 9 is V1 volts, the contact angle of the droplet 1 with respect to the insulating films 501 and 502 is reduced by electrowetting. At this time, the electric charge of the inside of the droplet 1 and the power source 9 moves to a position where the insulating films 501 and 502 are sandwiched. Accordingly, the droplet 1 is split into split droplets 101 and 102 (FIG. 1 (2)).

The charges that have moved to the surfaces of the insulating films 501 and 502 in the split droplets 101 and 102 gradually move to the power source 9 due to the leakage current of the insulating films 501 and 502. As a result, the contact angle of the split droplets 101 and 102 with respect to the insulating films 501 and 502 is increased and restored to the original size (FIG. 1 (3)).
The split droplets 1011 and 1012 whose contact angles are restored are caused to flow downstream by the flow field in the flow path (FIG. 1 (4)).

  In this way, by setting the flow path width necessary for the liquid droplet splitting to the same level as the liquid droplets, it is possible to generate smaller liquid droplets without increasing the pressure loss of the flow path.

  In addition, since the droplet diameter after splitting depends on the contact area with the wall surface of the droplet before splitting, the contact area with the wall surface of the droplet is always constant by supplying a stable laminar flow in the microchannel. It becomes. Thereby, the distribution of the droplet diameter after the division can be made substantially equal to the distribution before the division, and a uniform flow diameter can be obtained.

(Drop breakup by expansion channel)
In order to change the contact angle of the droplet 1, the droplet 1 needs to be in contact with both of the insulating films 501 and 502, so the width of the flow path 3 needs to be about the same as the diameter of the droplet 1. . In the case of FIG. 1, since the flow path width is small, depending on the properties of the droplets, the droplets may not break when a voltage is applied to the power source 9.

FIG. 2 shows a schematic configuration for enlarging the channel width of the droplet splitting portion of the present invention.
When the voltage of the power source 9 is 0 volts, the contact angle of the droplet 1 in the pre-expansion portion 301 of the flow path 3 with respect to the insulating films 501 and 502 is large (FIG. 2 (1)).
When the voltage of the power source 9 is V1 volts, the contact angle of the droplet 1 in the pre-enlargement portion 301 of the flow path 3 with respect to the insulating films 501 and 502 decreases (FIG. 2 (2)).

The droplet 103 having a reduced contact angle passes through the enlarged portion 302 of the flow channel 3 and moves to the post-enlarged portion 303 by the flow field in the flow channel. At this time, the droplet 103 does not separate from the insulating films 501 and 502 due to electrostatic force, and thus extends in a direction perpendicular to the flow path (FIG. 2 (3)).
By setting the voltage of the power source 9 to V2 volts, which is larger than V1 volts, the droplet 104 in the enlarged portion 303 of the flow path 3 is split into split droplets 101 and 102 (FIG. 2 (4)).

  Similar to FIG. 1 (3), the contact angle of the split droplets 101 and 102 is restored by the leakage current of the insulating films 501 and 502 (FIG. 2 (5)). Then, it moves downstream by the flow field in the flow path.

  In this way, even when the flow path entrance is narrow, about 0.5 to 1.0 times the droplet diameter, by adopting a configuration in which the flow path width at the time of droplet breakup is enlarged, the case of FIG. It is possible to break the droplet more reliably.

FIG. 3 shows a schematic configuration in which the flow path width of the droplet splitting portion of the present invention continuously increases.
When the voltage of the power supply 9 is 0 volts, the droplet 1 is in contact with the insulating films 501 and 502 (FIG. 3 (1)).
When the voltage of the power source 9 is V1 volts, the contact angle of the droplet 1 with respect to the insulating films 501 and 502 decreases (FIG. 3 (2)).

The droplet 103 having a reduced contact angle moves downstream by the flow field in the flow path. At this time, the droplet 103 does not separate from the insulating films 501 and 502 due to electrostatic force, and thus extends in a direction perpendicular to the flow path (FIG. 3 (3)).
When the width of the flow path 3 becomes larger than a certain value, the droplet 103 is split (FIG. 3 (4)).

  Similar to FIG. 1 (3), the contact angle of the split droplets 101 and 102 is restored by the leakage current of the insulating films 501 and 502 (FIG. 3 (5)). Then, it moves downstream by the flow field in the flow path.

  In this way, by adopting a configuration in which the flow path width continuously increases, it becomes possible to spontaneously break up the droplet in the flow field, and it is necessary to change the power supply voltage in two stages as shown in FIG. Disappears. In addition, since the channel width continuously increases, it is not necessary to limit the maximum droplet diameter that can be split, and droplets of various diameters can be handled.

(Drop breakup due to oblique arrangement of drive electrodes)
FIG. 4 shows a schematic configuration in which the drive electrode of the droplet splitting portion of the present invention is disposed at an oblique position where the electrode center lines do not coincide.
When the voltage of the power source 9 is 0 volts, the contact angle of the droplet 1 with respect to the insulating films 501 and 502 is large (FIG. 4 (1)).

  If the voltage of the power source 9 is set to V1 volts when the droplet 1 moves to a position in contact with both the drive electrodes 401 and 402, the contact angle of the droplet 1 with respect to the insulating films 501 and 502 is reduced by electrowetting. Accordingly, the droplet 1 is split into split droplets 101 and 102 (FIG. 4 (2)).

  As in FIG. 1, the contact angle of the split droplets 101 and 102 is restored by the leakage current of the insulating films 501 and 502 (FIG. 4 (3)). Then, it moves downstream by the flow field in the flow path.

  In this way, the drive electrodes 401 and 402 are arranged obliquely with respect to the droplet 1, and by dividing the droplet 1 in an oblique direction with respect to the flow channel 3, the flow path of the flow channel as shown in FIGS. There is no need to change the width, and no need to change the power supply voltage in two stages as shown in FIG. Further, even when the droplet diameter with respect to the flow path is relatively large, a distance is generated between the divided droplets, so that the droplets once divided are difficult to merge.

  Needless to say, if the electrode center lines do not coincide with each other, one drive electrode end facing diagonally has the same effect even if it overlaps the position of the other drive electrode end.

(Contact angle restoration control of the first split droplet)
In the case of FIG. 1, when the distance between the droplets 101 and 102 after the division is small or the voltage V1 is large, the electrostatic forces acting between the 101 and 102 may attract each other and merge. This is because the charge inside the droplet moves to the surface on the other droplet side after splitting.

The configuration and operation principle for controlling the contact angle restoration of the first split droplet according to the present invention will be described with reference to FIG.
In addition to the insulating films 501 and 502, ground electrodes 1201 and 1202 are connected to the droplet 1. The drive electrodes 401 and 402 are connected to the power sources 901 and 902 via the wirings 801 and 802 and the switches 1001 and 1002 or are grounded. The ground electrodes 1201 and 1202 are always grounded via the wirings 1101 and 1102 and do not need to be covered with an insulating film. The switches 1001 and 1002 are switched by the control circuit 26 according to time. The switching time can be appropriately adjusted according to the physical properties of the droplet and the medium.

First, the drive electrodes 401 and 402 are grounded via the switches 1001 and 1002 (FIG. 5 (1)).
A voltage is applied to the drive electrodes 401 and 402 by switching the switches 1001 and 1002 to the power sources 901 and 902 side. Then, the electric charge immediately moves from only the ground electrode 1201 to the droplet 1 that is in contact with both the drive electrode 401 covered with the insulating film 501 and the installation electrode 1201 that is not covered with the insulating film. Is charged. The same applies to the other drive electrode 402 and the ground electrode 1202. As a result, the droplet 1 is split into a droplet 101 and a droplet 102 (FIG. 5 (2)).

Only the switch 1001 is switched to the ground side. As a result, the charges inside the drive electrode 401 and the droplet 101 move. Then, the contact angle of the droplet 101 with respect to the insulating film 501 is restored (FIG. 5 (3)).
The droplet 101 is separated from the insulating film 501 by the restoration of the contact angle. As a result, the droplet 101 flows to the downstream side of the flow path 3 (FIG. 5 (4)).

Switch 1002 is switched to the ground side. As a result, the charges inside the drive electrode 402 and the droplet 102 move. Then, the contact angle of the droplet 102 with respect to the insulating film 502 is restored (FIG. 5 (5)).
Due to the restoration of the contact angle, the droplet 102 is separated from the inner wall of the flow path. As a result, the droplet 102 is caused to flow downstream of the flow path 3.

  In this manner, by controlling the switching of the contact angle restoration timing of the droplets 101 and 102 after splitting, it is possible to prevent the droplets that have been split once from being combined.

(Mode of first electrode arrangement)
6A to 6D are schematic views showing a plurality of arrangement examples of the drive electrodes 401 and 402 and the ground electrodes 1201 and 1202 on the inner surface of the flow path 3 for realizing the splitting method of FIG. 5 of the present invention. It is a block diagram. An insulating film is formed on the drive electrodes 401 and 402, but is omitted in the drawing. There is no insulating film on the ground electrodes 1201 and 1202. FIG. 6D shows a case where the ground electrodes 1201 and 1202 are formed as one electrode 12, which is excellent in terms of ease of manufacturing.

(Contact angle restoration control of the second split droplet)
The configuration and operation principle for controlling the contact angle restoration of the second split droplet of the present invention will be described with reference to FIG. The drive electrodes 4011 and 4021 are connected to the power sources 901 and 902 via the wirings 8011 and 8021 and the switches 1001 and 1002, or are grounded. The ground electrodes 4012 and 4022 are always grounded via the wirings 8012 and 8022. The switches 1001 and 1002 are switched by the control circuit 26 according to time. The switching time can be appropriately adjusted according to the physical properties of the droplet and the medium.

First, the drive electrodes 4011 and 4021 are grounded via the switches 1001 and 1002 (FIG. 7 (1)).
A voltage is applied to the drive electrodes 4011 and 4021 by switching the switches 1001 and 1002 to the power sources 901 and 902 side at positions where the droplet 1 is in contact with the drive electrodes 4011, 4012, 4021 and 4022. As a result, the droplet 1 is split into a droplet 101 and a droplet 102 (FIG. 7 (2)).

Only the switch 1001 is switched to the ground side. As a result, the charges inside the drive electrodes 4011 and 4012 and the droplet 101 move. Then, the contact angle of the droplet 101 with respect to the insulating film 501 is restored (FIG. 7 (3)).
Due to the restoration of the contact angle, the droplet 101 is separated from the inner wall of the flow path. As a result, the droplet 101 flows to the downstream side of the flow path 3 (FIG. 7 (4)).

Switch 1002 is switched to the ground side. As a result, the charges inside the drive electrodes 4021 and 4022 and the droplet 102 move. Then, the contact angle of the droplet 102 with respect to the insulating film 502 is restored (FIG. 7 (5)).
Due to the restoration of the contact angle, the droplet 102 is separated from the inner wall of the flow path. As a result, the droplet 102 is caused to flow downstream of the flow path 3.

  In this manner, by controlling the switching of the contact angle restoration timing of the droplets 101 and 102 after splitting, it is possible to prevent the droplets that have been split once from being combined.

(Second electrode arrangement mode)
8A to 8C are schematic configuration diagrams showing a plurality of arrangement examples of the drive electrodes 4011, 4012, 4021, and 4022 on the inner surface of the flow path 3 for realizing the splitting method of FIG. 7 of the present invention. It is. An insulating film is formed on the drive electrodes 4011, 4012, 4021, and 4022, but is omitted in the drawing. FIG. 8D shows the case where the electrode rows 411 and 412 are formed by forming a plurality of drive electrodes on one flow path wall. An insulating film is formed on the electrode rows 411 and 412, but is omitted in the drawing.

(Adjustment of droplet size after splitting)
The method for adjusting the droplet diameter after splitting according to the present invention will be described with reference to FIG. As shown in FIG. 5 or FIG. 7, when a voltage can be independently applied to the drive electrodes on each channel wall surface, it is possible to adjust the droplet diameter after splitting. FIG. 9 has the same configuration as FIG. 7, and wirings, switches, and power supplies are omitted in FIG. The switch is switched over time by the control circuit. The switching time can be appropriately adjusted according to the physical properties of the droplet and the medium.

First, the drive electrodes 4011 and 4021 are grounded and at 0 volts (FIG. 9 (1)).
A voltage of V1 volts is applied to the drive electrode 4011 and V2 volts is applied to the 4021 so that the droplet does not break. Since V2 is larger than V1, the contact angle with respect to the insulating film 502 is smaller than the contact angle with respect to the insulating film 501. As a result, the contact area of the droplet 1 with the insulating film 502 is larger than the contact area with the insulating film 501 (FIG. 9B).

  V3 volts is applied to the drive electrodes 4011 and 4021. Since V3 is larger than V2, the droplet breaks up. At this time, the volumes of the split droplets 101 and 102 differ depending on the contact area before splitting (FIG. 9 (3)).

Only the drive electrode 4011 is grounded. As a result, the contact angle of the droplet 101 with respect to the insulating film 501 is restored (FIG. 9 (4)).
Due to the restoration of the contact angle, the droplet 101 is separated from the inner wall of the flow path. As a result, the droplet 101 flows to the downstream side of the flow path 3 (FIG. 9 (5)).

The drive electrode 4021 is grounded. As a result, the contact angle of the droplet 102 with respect to the insulating film 502 is restored (FIG. 9 (6)).
Due to the restoration of the contact angle, the droplet 102 is separated from the inner wall of the flow path. As a result, the droplet 102 is caused to flow downstream of the flow path 3.

  In this way, it is possible to adjust the droplet diameter after splitting by independently applying a voltage to the drive electrodes on each channel wall surface by switching control.

(Summary)
According to the present invention, the droplet generated by the shearing force in the microchannel of the microfluidic chip is split vertically to the channel wall surface by electrowetting in the flow field downstream of the channel. As a result, finer droplets can be generated. In addition, by performing shearing and splitting operations in a laminar flow in the same flow path, the split droplet generation rate by electrowetting can be reduced to the order of several hundreds of Hz synchronized with the generation rate of droplets generated by shearing force. It becomes possible to follow.

  In addition, since the droplet diameter after splitting depends on the contact area with the wall surface of the droplet before splitting, the contact area with the wall surface of the droplet is always constant by supplying a stable laminar flow in the microchannel. It becomes. Thereby, the distribution of the droplet diameter after the division can be made substantially equal to the distribution before the division, and a uniform flow diameter can be obtained.

  Furthermore, droplet breakup in the direction perpendicular to the wall surface due to electrowetting can follow up to the order of several hundred Hz. Therefore, it is possible to divide the droplets in synchronization with the generation rate of the droplets generated by the shearing force, and the number of droplets generated per unit time is about the same as the conventional one.

(Other)
As mentioned above, although the example of this invention was demonstrated, this invention is not limited to the above-mentioned example, A various change is possible in the range of the invention described in the claim.
The droplet atomization apparatus of the present invention can be combined with the various droplet splitting portions described above.

The cross section of the flow path does not necessarily have to be a rectangle, and the present invention can be realized by a trapezoidal shape, a circular shape, or other shapes.
The voltage switching of the control circuit 26 may be performed by providing a dielectric constant monitor on the electrode, for example, in addition to the time switching.

DESCRIPTION OF SYMBOLS 1 ... Droplet 101 ... Droplet 102 after splitting ... Droplet 103 after splitting ... Droplet 104 after applying voltage ... Droplet 1011 after applying voltage ... After splitting Droplet 1012 with contact angle restored ... Droplet 2 with contact angle restored after splitting ... Medium 3 ... Channel 301 ... Channel expansion front 302 ... Channel expansion unit 303 ··· Channel expansion rear portion 304 ··· Droplet generating portion 305 ··· Droplet splitting portion 401 ··· Driving electrode 402 ··· Driving electrode 4011 ··· Driving electrode 4012 ··· Driving electrode 4021 ··· Drive electrode 4022 ... Drive electrode 411 ... Drive electrode row 412 ... Drive electrode row 501 ... Insulating film 502 ... Insulating film 6 ... Water-repellent film 701 ... Flow path wall 702 ..Channel wall 801... Wiring 802... Wiring 9. Power supply 1001 ... Switch 1002 ... Switch 1101 ... Wiring 1102 ... Wiring 1201 ... Ground electrode 1202 ... Ground electrode 17 ... Microfluidic chip 18 ... Pipe 19 ... Pipe 20 ... Liquid feed pump 21 ... Liquid feed pump 22 ... Droplet raw material 24 ... Pipe 25 ... Recovery container

Claims (12)

A droplet generator that generates a first droplet by shearing force from two types of liquids that do not mix with each other flowing in the microchannel of the microfluidic chip;
A droplet splitting portion that generates a second droplet by applying a voltage to at least a pair of drive electrodes formed on the inner wall of the downstream portion of the flow path to split the droplet;
A droplet atomization apparatus comprising:   2. The droplet atomization apparatus according to claim 1, wherein the droplet splitting portion has a flow path width of 0.5 times or more the particle size of the first droplet.   The droplet atomization apparatus according to claim 1, wherein the downstream portion of the flow path includes a flow path width expanding portion whose width increases in a laminar flow direction.   The downstream portion of the flow path further includes a first flow path portion having a width equal to or smaller than a particle diameter of the first droplet, and a second flow having a width wider than the flow diameter of the first droplet. The droplet atomization apparatus according to claim 3, further comprising a passage portion.   The droplet atomization apparatus according to any one of claims 1 to 4, wherein the drive electrode faces each other.   2. The droplet atomization apparatus according to claim 1, wherein the drive electrode is formed at a position where a center line of the drive electrode does not coincide with an inner wall facing the downstream portion of the flow path. A droplet generator that generates a first droplet by shearing force from two types of liquids that do not mix with each other flowing in the microchannel of the microfluidic chip;
A droplet splitting section for generating a second droplet by changing the voltage of at least three electrodes formed on the inner wall of the downstream portion of the flow path by switching control to split the droplet;
A droplet atomization apparatus comprising: The droplet splitting part is
A pair of drive electrodes facing the inner wall;
At least one of a pair of ground electrodes facing the inner wall, a pair of ground electrodes running in parallel on the same surface of the inner wall, and one ground electrode located on the inner wall surface different from the drive electrode;
The droplet atomization apparatus according to claim 7, wherein:   The droplet atomization apparatus according to claim 8, wherein the droplet splitting portion includes a ground electrode that is not covered with an insulating film.   9. The droplet atomizing device according to claim 8, wherein the droplet splitting portion has a drive electrode or a ground electrode covered with an insulating film.   9. The droplet atomization device according to claim 8, wherein the droplet splitting portion has two or more drive electrodes covered with an insulating film on the same surface of the inner wall.   The droplet splitting unit has at least one of a pair of electrodes facing each other, a pair of electrodes positioned on a vertical plane, and a pair of electrodes formed with a plurality of electrode rows on the same plane. 9. The droplet atomization apparatus according to claim 8, wherein a voltage is set for each of the electrodes independently.

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