JP6919238B2 - Droplet forming device and droplet forming method - Google Patents

Description

The present invention relates to a droplet forming apparatus and a droplet forming method.

In recent years, with the progress of stem cell technology, a technique of ejecting a plurality of cells from an inkjet head of a droplet forming apparatus to form an organization is known.

For example, a liquid holding means for holding a cell solution, a film-like member for discharging the cell solution as a droplet from a nozzle by vibration, and a droplet forming apparatus having an open portion to the atmosphere have been proposed (for example, Patent Document 1). reference).
Further, as a droplet forming device that controls the pressure acting on the liquid using air, the pressure acting on the ink in the head is maintained within an appropriate range by the pressure controlling means for controlling the pressure in the space in the tank. An inkjet image forming apparatus has been proposed (see, for example, Patent Document 2).

An object of the present invention is to provide a droplet forming apparatus having excellent ejection stability even when the amount of the particle suspension used is small and the amount of the liquid held by the liquid holding means fluctuates.

The liquid droplet forming apparatus of the present invention as a means for solving the above-mentioned problems includes a liquid holding means for holding a particle suspension, a liquid supplying means for supplying the particle suspension to the liquid holding means, and a nozzle. Is formed, and the droplet discharging means for discharging the particle suspension held by the liquid holding means as droplets from the nozzle by vibration is connected to or integrated with the liquid supplying means, and the inside of the liquid holding means It has a pressure control means for controlling the pressure of the above.

According to the present invention, it is possible to provide a droplet forming apparatus having excellent ejection stability even when the amount of the particle suspension used is small and the amount of the liquid held by the liquid holding means fluctuates.

FIG. 1 is a schematic view showing an example of the droplet forming apparatus of the first embodiment. FIG. 2 is a schematic diagram for explaining the direct supply of the cell suspension from the liquid supply means to the liquid holding means in the droplet forming apparatus of the first embodiment. FIG. 3 is a schematic view showing an example of a droplet forming apparatus according to a modified example of the first embodiment. FIG. 4 is a schematic view showing an example of the droplet forming apparatus of the second embodiment.

(Droplet forming device and droplet forming method)
In the droplet forming apparatus of the present invention, a liquid holding means for holding a particle suspension, a liquid supplying means for supplying the particle suspension to the liquid holding means, and a nozzle are formed and held by the liquid holding means. A droplet discharging means for discharging the particle suspension as droplets from the nozzle by vibration, a pressure controlling means for connecting or integrating with the liquid supplying means and controlling the pressure in the liquid holding means, and a pressure controlling means. It is preferable to have at least one of a liquid amount detecting means and a liquid amount calculating means, and further, if necessary, other means.

The droplet forming method of the present invention preferably forms droplets by the droplet forming apparatus of the present invention and includes at least one of a liquid amount detecting step and a liquid amount calculating step, and if necessary, other Including the process of.
The liquid amount detecting step and the liquid amount calculating step can be performed by the liquid amount detecting means and the liquid amount calculating means, and the other steps can be performed by the other means.
Hereinafter, the droplet forming method of the present invention will also be described through the description of the droplet forming apparatus of the present invention.

In the droplet forming apparatus and the droplet forming method of the present invention, in the conventional droplet forming apparatus that forms a particle suspension as droplets, the particles are suspended by the liquid holding means by the liquid supply and the droplet ejection. If the amount of the turbid liquid fluctuates even in a small amount of about 1 mm to 5 mm in depth, the pressure applied to the nozzle of the discharge head fluctuates by about 10 Pa to 50 Pa, and the size and speed of the discharged droplets change. , It is based on the finding that there is a problem that the discharge stability is lowered.
In this regard, it is possible to reduce the fluctuation of the liquid level of the retained particle suspension by increasing the cross-sectional area of the liquid holding means.
The droplet forming apparatus and the droplet forming method of the present invention are used because the conventional droplet forming apparatus and the inkjet image forming apparatus need to be provided with a liquid holding means having a large cross-sectional area, a tank independent of the head, and the like. It is based on the finding that there is a problem that it cannot be applied in the case of a small amount of particle suspension because the amount of liquid is large.

As a result of diligent studies to solve the above-mentioned problems, the present inventors have obtained the following findings. Specifically, when the amount of the particle suspension in the liquid holding means is large, the water head pressure applied to the nozzle is high, and when the amount of the particle suspension in the liquid holding means is small, the above. The water head pressure applied to the nozzle becomes low. Therefore, in the droplet forming apparatus, the pressure control means is based on the head pressure (hereinafter, also referred to as “design head pressure”) when a set amount of the particle suspension is held in the liquid holding means. The pressure in the liquid holding means is controlled according to the head pressure applied to the nozzle due to the particle suspension actually held in the liquid holding means, and the pressure applied to the nozzle is brought close to the design head pressure. As a result, the head pressure applied to the nozzle becomes almost constant regardless of the amount of liquid in the particle suspension in the liquid holding means, so that the fluctuation in the size and speed of the droplets discharged from the nozzle is reduced. This makes it possible to improve the discharge stability even when the amount of liquid held by the liquid holding means fluctuates.

<Liquid holding means>
The liquid holding means is a means for holding a particle suspension.
The shape, size, material, and structure of the liquid holding means are not particularly limited and may be appropriately selected depending on the intended purpose.
Examples of the material of the liquid holding means include metals such as stainless steel, nickel and aluminum, silicon, ceramics, and polymer materials.

<Liquid supply means>
The liquid supply means is a means for supplying the particle suspension to the liquid holding means.
The shape, size, material, and structure of the liquid supply means are not particularly limited and may be appropriately selected depending on the intended purpose.

The liquid supply means is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include micropipettes, syringes and tubes. In addition, the particle suspension may be supplied by the user. Further, the liquid supply means may be provided with a configuration for automatically supplying the particle suspension to the liquid holding means when, for example, the amount of the particle suspension in the liquid holding means becomes equal to or less than a specified amount. good. These may be used alone or in combination of two or more.

The liquid supply means may directly supply the particle suspension to the liquid holding means, or may supply the particle suspension via other means.
When the particle suspension is directly supplied from the liquid supply means to the liquid holding means, the route through which the particle suspension passes is short, so that the particle suspension is suspended even when the particle suspension is as small as about 10 μL, for example. The liquid can be supplied to the liquid holding means without waste. In particular, it is effective when the particle suspension is not available in large quantities, is expensive, and it is difficult to hold the particles in the liquid holding means for a long time.

<Drop ejection means>
The droplet ejection means is a means for ejecting the particle suspension held by the liquid holding means as droplets from the nozzle by vibrating after a nozzle is formed.

It is preferable that the nozzle is formed as a substantially circular through hole at substantially the center of the film-like member.

In the droplet forming apparatus of the present invention, the diameter of the nozzle is preferably 20 μm or more and 200 μm or less, and more preferably 60 μm or more and 150 μm or less.
The diameter of the nozzle is not particularly limited and may be appropriately selected depending on the intended purpose, but it is preferably twice or more the particle size in order to prevent the particles of the particle suspension from being clogged in the nozzle. .. When animal cells, particularly human cells, are used as the particles, the size of the cells is generally about 10 μm to 30 μm. Therefore, it is preferable that the diameter of the nozzle is 20 μm or more. Further, if the droplets become too large, it becomes difficult to form minute droplets, so the diameter of the nozzle is preferably 200 μm or less.

-Membrane-like member-
The droplet ejection means is preferably made of a film-like member.
The film-like member is a member in which a nozzle is formed and the liquid held by the liquid holding means is discharged as droplets from the nozzle by vibration due to its amplitude motion. The film-like member is vibrated by the vibrating member.
The film-like member is a member arranged at the lower end of the liquid holding means, and a nozzle which is a through hole is formed at substantially the center of the film-like member.
The particle suspension held by the liquid holding means is discharged as droplets from the nozzle by the vibration of the film-like member.

The planar shape, size, material, and structure of the film-like member are not particularly limited and may be appropriately selected depending on the intended purpose.
Examples of the planar shape of the film-like member include polygons such as a circle, an ellipse, a rectangle, a square, and a rhombus.

The material of the film-like member is not particularly limited and may be appropriately selected depending on the intended purpose. However, if the film-like member is too soft, the film-like member easily vibrates, and it is difficult to immediately suppress the vibration when the film-like member is not discharged. Therefore, it is preferable to use a material having a certain degree of hardness, and examples thereof include metals, ceramics, and polymer materials.
Further, as the material of the film-like member, it is preferable that the particle suspension has low adhesion to particles. In particular, when cells are used as the particles, the adhesion of cells to the membrane-like member is generally considered to depend on the contact angle of the film-like member with water, and the material of the membrane-like member is considered to be dependent on the contact angle with water. When the hydrophilicity is high, or when the material of the membranous member is highly hydrophobic, the adhesion of cells to the membranous member tends to be low.
Examples of the highly hydrophilic material include ceramics such as metals and metal oxides. Further, examples of the highly hydrophobic material include fluororesin and the like.
Specific examples of the material of the film-like member include stainless steel, nickel, aluminum, silicon dioxide, alumina, and zirconia.
Further, the surface of the film-like member may be coated to reduce the adhesion of cells to the film-like member. Specifically, the surface of the membrane-like member may be coated with a material such as a metal, a metal oxide, or a synthetic phospholipid polymer that imitates a cell membrane.
Examples of the synthetic phospholipid polymer imitating the cell membrane include 2-methacryloyloxyethyl phosphorylcholine (trade name: Lipidure, manufactured by NOF CORPORATION).

-Vibration member-
The droplet ejection means preferably vibrates the film-like member with a vibrating member to eject droplets from the nozzle.

The vibrating member is formed on the upper surface or the lower surface of the film-like member.
The shape, size, material, and structure of the vibrating member are not particularly limited and can be appropriately selected according to the purpose.
The shape of the vibrating member is not particularly limited and may be appropriately designed according to the shape of the film-like member. For example, when the planar shape of the film-like member is circular, it is flat around the nozzle. It is preferable to form a vibrating member having an annular shape (ring shape).

When a piezoelectric element is used as the vibrating member, for example, a structure may be provided in which electrodes for applying a voltage are provided on the upper surface and the lower surface of the piezoelectric material. In this case, by applying a voltage between the upper and lower electrodes of the piezoelectric element from the driving means, compressive stress is applied in the lateral direction of the film surface, and the film-like member can be vibrated in the vertical direction of the film surface.
The piezoelectric material is not particularly limited and may be appropriately selected depending on the intended purpose. For example, lead zirconate titanate (PZT), bismuth iron oxide, metal niobate, barium titanate, or these. Examples include materials with metals and different oxides added.

Further, as the vibrating member, for example, the film-like member may be vibrated by attaching a member having a linear expansion coefficient different from that of the film-like member to the film-like member and heating the member having a different linear expansion coefficient. ..
In this case, it is preferable that the heater is attached to the member having a different coefficient of linear expansion, and when the member having a different coefficient of linear expansion is energized, the heater is heated and the film-like member is vibrated.

<Pressure control means>
The pressure control means is a means for controlling the pressure in the liquid holding means by connecting or integrating with the liquid supply means.

When the liquid amount of the particle suspension in the liquid holding means is large, the water head pressure applied to the nozzle is high, and when the liquid amount of the particle suspension in the liquid holding means is small, the nozzle is used. The water head pressure applied to the suspension becomes low.
Therefore, in the droplet forming apparatus, based on the design head pressure, the pressure control means is inside the liquid holding means according to the water head pressure applied to the nozzle by the particle suspension actually held by the liquid holding means. Control the pressure of the nozzle to bring the pressure applied to the nozzle closer to the design head pressure. As a result, the head pressure applied to the nozzle becomes substantially constant regardless of the amount of the liquid in the particle suspension in the liquid holding means, so that the size and speed of the droplets discharged from the nozzle can be changed. It can be made smaller.

The pressure control means is not particularly limited as long as it is connected to or integrated with the liquid supply means and controls the pressure in the liquid holding means, and can be appropriately designed according to the purpose, for example. Examples include micropipettes, syringes, tubes and the like.
The pressure control method includes, for example, supplying or sucking a liquid into the liquid holding means, introducing pressurized air into the liquid holding means, or sucking air existing in the liquid holding means. Can be mentioned.

The liquid supply means and the pressure control means may be separate or integrated, but the point of effectively utilizing the space in the droplet forming apparatus and the particles in the liquid holding means. It is preferable that the suspension is integrated because it is not necessary to automatically supply the particle suspension to the liquid holding means when the liquid amount of the suspension becomes equal to or less than the specified amount.
The configuration in which the liquid supply means and the pressure control means are integrated includes, for example, a configuration in which the pressure control means has a function as a liquid supply means. Specifically, a configuration in which a micropipette, a syringe, a tube, or the like is used as a liquid supply means and a pressure control means can be mentioned.

The difference between the maximum value and the minimum value of the pressure in the liquid holding means is preferably 5 Pa or more and 200 Pa or less, and more preferably 10 Pa or more and 100 Pa or less, from the viewpoint of making the head pressure applied to the nozzle substantially constant.

<Liquid amount detecting means, liquid amount calculating means, liquid amount detecting method, and liquid amount calculating method>
The droplet forming apparatus of the present invention preferably further includes at least one of a liquid amount detecting means and a liquid amount calculating means.
The liquid amount detecting method and the liquid amount calculating method in the droplet forming method of the present invention can be performed by the liquid amount detecting means and the liquid amount calculating means of the droplet forming apparatus of the present invention.

The liquid amount detecting means is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include electrodes arranged in the depth direction of the inner wall surface of the liquid holding means. Since the particle suspension has high conductivity when it contains a salt, it is possible to detect the depth of the liquid amount of the particle suspension by examining the continuity between a plurality of electrodes, the resistance value, and the like. can.
Further, as the liquid amount detecting means, for example, the light emitted by the light emitting element is reflected by the liquid surface of the particle suspension, a position sensor is arranged at a position based on the principle of triangular measurement, and the light is placed on the position sensor. The distance from the position of the light incident on the position sensor to the liquid surface of the particle suspension may be calculated.

The liquid amount calculating means is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the received signal of the position sensor is subjected to the particle suspension based on a preset conversion formula or a look-up table. For example, it is converted into the amount of turbid liquid.
Further, as the liquid amount calculating means, the consumption amount of the particle suspension is calculated by the number of times the particle suspension held by the liquid holding means is discharged as droplets from the nozzle, and a preset conversion formula or look is used. Conversion to the liquid volume of the cell suspension based on the uptable can be mentioned.

Since the droplet forming apparatus of the present invention has at least one of the liquid amount detecting means and the liquid amount calculating means, the depth of the liquid amount of the particle suspension in the liquid holding means can be determined. By obtaining the water head pressure applied to the nozzle from the particle suspension, the pressure in the liquid holding means can be controlled and the pressure applied to the nozzle can be brought close to the design head pressure.

<Other means and other processes>
The droplet ejection device of the present invention may have other means, if necessary. The other means are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a light irradiation means, a light receiving means, a driving means, and a recording means.
The droplet forming method of the present invention may include other steps, if necessary. The other steps are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a light irradiation step, a light receiving step, a driving step, and a recording step.

<Particle suspension>
The droplet forming apparatus of the present invention includes a particle suspension. The particle suspension contains at least one particle and, if necessary, other components.
The particle suspension is not particularly limited and may be appropriately selected depending on the intended purpose, but a cell suspension containing cells is preferable.
The cell suspension is preferably in a state in which cells are dispersed.

-Cell suspension-
The cell suspension contains cells and a liquid and, if necessary, other components.
Examples of the cells include animal cells, and in particular, human-derived animal cells and the like. Further, as the liquid, a liquid having a high affinity for the cells is preferable, and examples thereof include water.
The cell suspension preferably further contains a salt in order to adjust the osmotic pressure between the liquid and the cells. Further, in order to adjust the pH of the cell suspension, it is preferable that the cell suspension further contains a pH adjusting agent.
As the cell suspension, one appropriately prepared may be used. As the prepared product, for example, the cells are suspended in a pH-adjusted Tris buffer aqueous solution, a phosphate buffered saline (PBS solution) in which a metal salt such as Ca, K, or Na is added in the same amount as the culture solution. Examples include the ones.

The cells are preferably those recovered from the medium after being cultured in the medium.
The medium for culturing the cells is not particularly limited as long as it is a normally used cell culture medium, and can be appropriately selected according to the purpose such as the type of cells to be used. For example, "Revised Cultured Cell Experiment Handbook". Examples thereof include the serum-free medium and the medium containing serum described on pages 61 and 62 of (Published by Yodosha Co., Ltd.).
Examples of the serum-free medium include BME medium, MEM medium, αMEM medium, DMEM medium, IMDM medium, RPMI medium, F10 medium, F12 medium and other ham media, MCDB104, MCDB107, MCDB131, MCDB151, MCDB170, MCDB202 and the like. MCDB medium, RITC80-7 medium, ES medium, DM-160 medium, Fisher medium, WE medium, RPMI1640 medium, and a mixture of two or more of these, various cell growth factors, cell adhesion factors, hormones, binding proteins, lipids. , An antibiotic, an amino acid, etc. are added.
Serum such as fetal bovine serum may be added to the serum-free medium.

As the medium, a commercially available product can be used, and examples of the commercially available product include serum-free medium (registered trademark: Gibco, manufactured by Thermo Fisher Scientific Co., Ltd.) and the like.
The medium preferably does not contain animal-derived components in consideration of the final clinical application of cell tissues.

Hereinafter, embodiments of the droplet forming apparatus of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to these embodiments.

<First Embodiment>
FIG. 1 is a schematic view showing an example of the droplet forming apparatus of the first embodiment.
The droplet forming apparatus 10 in FIG. 1 includes a liquid holding means 11, a lid 15, a micropipette 16 as a liquid supplying means and a pressure controlling means, a nozzle 121 as a droplet discharging means, and a film-like member 12. have. The liquid holding means 11 holds a cell suspension 300 containing cells 350 as a particle suspension.
The micropipette 16 can control the pressure in the liquid holding means 11.
The film-like member 12 is fixed to the lower end of the liquid holding means 11, and a nozzle 121, which is a through hole, is formed at substantially the center of the film-like member 12. The cell suspension 300 held by the liquid holding means 11 is discharged as droplets from the nozzle 121 by the vibration of the film-like member 12.

When the amount of liquid in the cell suspension 300 in the liquid holding means 11 is large, the water head pressure applied to the nozzle 121 becomes high, and when the amount of liquid in the cell suspension 300 in the liquid holding means 11 is small, the nozzle 121 The head pressure on the head is low.
In the droplet forming apparatus 10, the micropipette 16 as the liquid supply means and the pressure control means supplies the cell suspension 300 into the liquid holding means 11 based on the design head pressure, and also supplies the cell suspension 300 to the liquid holding means 11. The retained cell suspension 300 controls the pressure in the liquid holding means 11 according to the water head pressure applied to the nozzle 121, and brings the pressure applied to the nozzle 121 close to the design water head pressure. Therefore, regardless of the amount of the cell suspension 300 in the liquid holding means 11, the head pressure applied to the nozzle 121 becomes substantially constant, and the fluctuation in the size and speed of the droplets ejected from the nozzle 121 is reduced. can do.

A piezoelectric element 13 as a vibrating member is formed on the lower surface side of the film-like member 12. The shape of the piezoelectric element 13 can be designed according to the shape of the film-like member 12. For example, when the planar shape of the film-like member 12 is circular, the planar shape is annular (around the nozzle 121). A ring-shaped) piezoelectric element 13 can be formed.
The piezoelectric element 13 has a structure in which electrodes for applying a voltage are provided on the upper surface and the lower surface of the piezoelectric material, and by applying a voltage between the upper and lower electrodes of the piezoelectric element 13, compressive stress is applied in the lateral direction of the film surface. , The film-like member 12 can be vibrated in the vertical direction of the surface of the film.

The droplet forming device 10 arranges the electrodes 14 in the depth direction of the inner wall surface of the liquid holding means 11 as the liquid amount detecting means.
Since the cell suspension 300 is generally composed of an aqueous solution containing a salt, it has high conductivity, and the depth of the liquid amount of the cell suspension 300 can be determined by examining the continuity between the plurality of electrodes 14, the resistance value, and the like. Can be detected.

FIG. 2 is a schematic diagram for explaining the direct supply of the cell suspension from the liquid supply means to the liquid holding means in the droplet forming apparatus of the first embodiment.
In the droplet forming apparatus 10A in FIG. 2, the cell suspension 300 is directly supplied from the micropipette 16 as the liquid supplying means to the liquid holding means 11. In the case of such a configuration, since the route through which the cell suspension 300 passes is short, even if the cell suspension 300 is as small as about 10 μL, the cell suspension 300 can be used as the liquid holding means 11 without waste. Can be supplied. In particular, the cell suspension 300 is not available in large quantities, is expensive, and is effective when it is difficult to hold the cells 350 in the liquid holding means 11 for a long time.

<< Modified example of the first embodiment >>
FIG. 3 is a schematic view showing an example of a droplet forming apparatus according to a modified example of the first embodiment. In the first embodiment, the same components as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The droplet forming apparatus 10B shown in FIG. 3 is a pressure control means in which a micropipette 16, a valve 19B, a chamber 21, a valve 19A, and a pipe 20 are connected in this order. A pressure control means such as a syringe (not shown) is further connected in the direction opposite to the chamber 21 of the pipe 20.

When pressurizing the gas phase 111, the valve 19A is opened after the valve 19B is closed, and the pressurized air is introduced into the pipe 20. After that, the valve 19A is closed, the micropipette 16 is pushed into the lid 15 to bring it into close contact, and then the valve 19B is opened, so that pressurized air can be introduced into the gas phase 111. At this time, by making the volume of the chamber 21 sufficiently smaller than the volume of the gas phase 111, the pressure rise width of the gas phase 111 can be reduced, so that a high-precision pump and a pressure gauge are not used. It is possible to control a minute pressure of about 10 Pa to 50 Pa.
Further, since the pressure of the gas phase 111 can be increased stepwise by repeating the opening and closing a plurality of times, the head pressure applied to the nozzle can be controlled.

<Second embodiment>
FIG. 4 is a schematic view showing an example of the droplet forming apparatus of the second embodiment. In the first embodiment, the same components as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In the droplet forming apparatus 10C of FIG. 4, a light emitting element 17 and a position sensor 18 are arranged above the liquid holding means 11 as the liquid amount detecting means. Further, the lid 15 is made of a transparent material.

The light emitted by the light emitting element 17 is specularly reflected by the liquid level 300A, the liquid level 300B, etc. of the cell suspension 300, and is incident on the position sensor 18 arranged based on the principle of triangulation. Thereby, the distance from the position of the light incident on the position sensor 18 to the liquid surface of the cell suspension 300 can be calculated.
A conversion formula or a look-up table may be set in advance, and the received signal of the position sensor 18 may be converted into the liquid amount of the cell suspension 300 to use the liquid amount calculation means.

Aspects of the present invention are, for example, as follows.
<1> A liquid holding means for holding a particle suspension and
A liquid supply means for supplying the particle suspension to the liquid holding means, and
A droplet ejection means in which a nozzle is formed and the particle suspension held in the liquid holding means is vibrated to be ejected as droplets from the nozzle.
The droplet forming apparatus is characterized by having a pressure control means that is connected to or integrated with the liquid supply means and controls the pressure in the liquid holding means.
<2> The droplet forming apparatus according to <1>, wherein the droplet ejection means is made of a film-like member.
<3> The droplet forming apparatus according to <2>, further comprising a vibrating member that vibrates the film-like member.
<4> The droplet forming apparatus according to any one of <2> to <3>, wherein the material of the film-like member is at least one of metal, ceramics, and a polymer material.
<5> The droplet forming apparatus according to any one of <1> to <4>, further comprising at least one of a liquid amount detecting means and a liquid amount calculating means.
<6> The droplet forming apparatus according to any one of <1> to <5>, wherein the particles of the particle suspension are cells.
<7> The droplet forming apparatus according to <6>, wherein the medium for culturing the cells does not contain an animal-derived component.
<8> The droplet forming apparatus according to any one of <1> to <7>, wherein the liquid supply means and the pressure control means are integrated.
<9> The droplet forming apparatus according to any one of <1> to <8>, wherein the pressure control means has a valve and a chamber.
<10> The droplet forming apparatus according to any one of <1> to <9>, wherein the diameter of the nozzle is 20 μm or more and 200 μm or less.
<11> The droplet forming apparatus according to <10>, wherein the diameter of the nozzle is 60 μm or more and 200 μm or less.
<12> The droplet forming apparatus according to any one of <1> to <11>, wherein the difference between the maximum value and the minimum value at the pressure in the liquid holding means is 5 Pa or more and 200 Pa or less.
<13> The liquid supply means has a configuration in which the particle suspension is automatically supplied to the liquid holding means when the amount of the particle suspension in the liquid holding means is equal to or less than a specified amount. > To <12>.
<14> The droplet forming apparatus according to any one of <1> to <13>, wherein the particle suspension further contains a salt.
<15> The droplet forming apparatus according to any one of <1> to <14>, wherein the particle suspension further contains a pH adjuster.
<16> A droplet forming method characterized in that droplets are formed by the droplet forming apparatus according to any one of <1> to <15>.
<17> The droplet forming method according to <16>, which further comprises at least one of a liquid amount detecting step and a liquid amount calculating step.

According to the droplet forming apparatus according to any one of <1> to <15> and the droplet forming method according to any one of <16> to <17>, the conventional problems are solved and the present invention is solved. The object of the invention can be achieved.

10, 10A, 10B, 10C Droplet forming device 11 Liquid holding means 12 Membrane-like member 13 Piezoelectric element 14 Electrode 15 Lid 16 Micropipette 17 Luminescent element 18 Position sensor 19A, 19B Valve 20 Piping 21 Chamber 111 Gas phase 121 Nozzle 300 cells Suspension 300A, 300B Liquid level 320 Liquid 350 cells

Japanese Unexamined Patent Publication No. 2016-116489 Japanese Unexamined Patent Publication No. 2006-326855

Claims (8)

A liquid holding means for holding the particle suspension and
A liquid supply means for supplying the particle suspension to the liquid holding means, and
A droplet ejection means in which a nozzle is formed and the particle suspension held in the liquid holding means is vibrated to be ejected as droplets from the nozzle.
Connected to the liquid supply means, or integrated, have a, and pressure control means for controlling the pressure in the liquid holding means, said pressure control means, the liquid holding pressure exerted on the nozzle so as to be constant A droplet forming apparatus characterized by controlling the pressure in the means. The droplet forming apparatus according to claim 1, wherein the droplet discharging means is made of a film-like member. The droplet forming apparatus according to any one of claims 1 to 2, further comprising at least one of a liquid amount detecting means and a liquid amount calculating means. The droplet forming apparatus according to any one of claims 1 to 3, wherein the particles of the particle suspension are cells. The droplet forming apparatus according to any one of claims 1 to 4, wherein the liquid supply means and the pressure control means are integrated. The droplet forming apparatus according to any one of claims 1 to 5, wherein the pressure control means includes a valve and a chamber. The droplet forming apparatus according to any one of claims 1 to 6, wherein the difference between the maximum value and the minimum value in the pressure in the liquid holding means is 5 Pa or more and 200 Pa or less. A method for forming a droplet, which comprises forming a droplet by the droplet forming apparatus according to any one of claims 1 to 7.

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