Composite nozzle, liquid drop emitter, and fabricating method thereof

(19)

(11)

EP 1 291 084 A2

(12)	EUROPEAN PATENT APPLICATION

(43)	Date of publication:
	12.03.2003 Bulletin 2003/11

(21)	Application number: 02256167.4

(22)	Date of filing: 05.09.2002

(51)	International Patent Classification (IPC)⁷: B01L 3/02

(84)	Designated Contracting States:
	AT BE BG CH CY CZ DE DK EE ES FI FR GB GR IE IT LI LU MC NL PT SE SK TR
	Designated Extension States:
	AL LT LV MK RO SI

(30)

Priority:

05.09.2001 JP 2001268867

(71)	Applicant: NGK INSULATORS, LTD.
	Nagoya-City, Aichi Prefecture 467-8530 (JP)

(72)	Inventors:
	Okumura, H., Legal Affairs & Intell. Prop. Dpt Nagoya-shi, Aichi-ken 467-8530 (JP) Ohnishi, Takao, Legal Affairs & Intell. Prop. Dpt Nagoya-shi, Aichi-ken 467-8530 (JP) Mizuno, H., Legal Affairs & Intell. Prop. Dpt. Nagoya-shi, Aichi-ken 467-8530 (JP) Hirota, T., Legal Affairs & Intellectual Prop. Dpt Nagoya-shi, Aichi-ken 467-8530 (JP)

(74)	Representative: Paget, Hugh Charles Edward et al
	MEWBURN ELLIS York House 23 Kingsway London WC2B 6HP London WC2B 6HP (GB)

(54)	Composite nozzle, liquid drop emitter, and fabricating method thereof

(57) A composite nozzle is provided which includes a first nozzle and a second nozzle. The first nozzle is formed in an adhesive layer made having a Young's modulus Ea and defines an upstream portion of an outlet path of the composite nozzle. The second nozzle is formed in a nozzle base layer having a Young's modulus Es and defines a downstream portion of the outlet path of the composite nozzle. The nozzle base layer is attached through the adhesive layer to a flow path member leading to an inlet. A Young's modulus ratio of Es to Ea is selected within a range of 1.4 to 500, thereby facilitating absorption of vibrations of the nozzle base layer through the adhesive layer.

Description

BACKGROUND OF THE INVENTION

1 Technical Field of the Invention

[0001] The present invention relates generally to a composite nozzle which may be used to emit minute drops of liquid containing DNA fragments and deposit them on a substrate to produce a DNA chip, a liquid drop emitter equipped with such a composite nozzle, and fabricating methods thereof.

2 Background Art

[0002] Liquid drop emitters are known which are of a type including a flow path base in which a flow path is formed and a laminate of an adhesive film and a nozzle base layer. The adhesive film has formed therein flow paths each of which defines an upstream portion of an outlet path of one of nozzles. The nozzle base layer has formed therein flow paths each of which defines a downstream portion of the outlet path of one of the nozzles. The laminate is fabricated by forming the nozzles in the nozzle base layer and the adhesive film independently and laying the nozzle base layer on the adhesive film in alignment of the flow paths of the nozzle base layer with the flow paths of the adhesive film and bonding them together. The laminate is attached to the flow path base through the adhesive film. The liquid drop emitters also include micropumps implemented by piezoelectric/electrostrictive devices which compress liquid within compression chambers to emit drops of the liquid from the nozzles.

[0003] In recent years, rapid progress has been made in analyzing gene structure. Various kinds of gene structures as well as human gene structures have been found. Such gene analysis usually uses a DNA chip on which more than a few thousand types of DNA fragments are deposited and immobilized in an array of minute spots. The liquid drop emitter, however, has a drawback in that it is difficult to press the periphery of each of the nozzles mechanically when the nozzle base layer is bonded to the flow path base through the adhesive film, thus causing bubbles to be created between the adhesive film and the nozzle base layer, which may result in micro separation of the adhesive film from the flow path base.

[0004] Moreover, a difference in thermal expansion and contraction between the flow path base and the nozzle base layer causes residual stress to be produced which may result in a decrease in strength of a bond between the flow path base and the nozzle base layer and geometrical deformation and a change in location of the nozzles.

[0005] Further, the flow paths of the nozzle base layer are machined independently of those of the adhesive film, which may result in deformation of the flow paths of the adhesive film when attached to the flow path base, thus leading to a difficulty in ensuring geometric symmetry with respect to the center of the nozzles.

[0006] The above problems will result in difficulties in ensuring a desired velocity at which drops of liquid are enabled to be discharged straight from the nozzles and desired locations of the drops deposited on a substrate.

SUMMARY OF THE INVENTION

[0007] It is therefore a principal object of the invention to avoid the disadvantages of the prior art.

[0008] It is another object of the invention to provide a composite nozzle, a liquid drop emitter using such a composite nozzle, and fabricating methods thereof which are designed to ensure a desired velocity at which drops of liquid are enabled to be discharged straight and desired locations of the drops deposited on a substrate.

[0009] According to one aspect of the invention, there is provided a composite nozzle which may be employed in a liquid depositing system to deposit minute drops of liquid containing DNA fragments on a substrate in a dense array of dots to produce a DNA chip. The composite nozzle comprises a first nozzle and a second nozzle. The first nozzle is formed in an adhesive member made of an adhesive material having a Young's modulus Ea. The first nozzle defines an upstream portion of an outlet path of the composite nozzle. The second nozzle is formed in a nozzle base member made of a material having a Young's modulus Es and defines a downstream portion of the outlet path of the composite nozzle. The nozzle base member is attached through the adhesive member to a flow path member in fluid communication of the second nozzle through the first nozzle with a flow path formed in the flow path member leading to an inlet. A ratio of the Young's modulus Es to the Young's modulus Ea (i.e., Es / Ea) is defined within a range of 1.4 to 500.

[0010] Specifically, the Young's modulus Ea of the adhesive member is smaller than the Young's modulus Es of the nozzle base member, thus facilitating absorption or dampening of vibrations through the adhesive member which arise from application of pressure of a jet of liquid from the composite nozzle to the nozzle base member, thus resulting in stability of the meniscus of a drop of the liquid from the nozzle. Too small the Young's modulus Ea of the adhesive member will result in a lack of pressure required to emit the drop of liquid from the composite nozzle. This drawback is avoided by definition of the above ratio.

[0011] In the preferred mode of the invention, the adhesive member has good wetability with the flow path member in a melted condition of the adhesive material.

[0012] According to the second aspect of the invention, there is provided a composite nozzle which comprises a first nozzle and a second nozzle. The first nozzle is formed in an adhesive member made of an adhesive material and defines an upstream portion of an outlet path of the composite nozzle. The second nozzle is formed in a nozzle base member and defines a downstream portion of the outlet path of the composite nozzle. The nozzle base member is attached through the adhesive member to a flow path member in fluid communication of the second nozzle through the first nozzle with a flow path formed in the flow path member leading to an inlet. The first nozzle has an extension member extending from the first nozzle to the flow path of the flow path member along a periphery of an inner surface of the flow path.

[0013] The above structure serves to avoid formation of a step between the flow path member and the adhesive member in which bubbles may stay. This ensures the stability of emission of a drop of liquid from the composite nozzle and also avoids micro separation of the adhesive member from the flow path member caused by accumulation of the bubbles on an interface between the adhesive member and the flow path member. The provision of the extension member results in an increase in rigidity of the composite nozzle, which leads to a decrease in loss of pressure required to emission of a drop of the liquid from the composite nozzle at a desired flow rate.

[0014] In the preferred mode of the invention, the adhesive member has a given Young's modulus Ea. The nozzle base member has a given Young's modulus Es. A ratio of the Young's modulus Es to the Young's modulus Ea (i.e., Es / Ea) is within a range of 1.4 to 500.

[0015] The outlet path has an inner diameter decreasing at a constant rate from the extension member to the second nozzle, thereby forming a smooth inner wall of the outlet path, which minimizes a loss of pressure of flow of the liquid through the outlet path.

[0016] The adhesive member has good wetability with the flow path member in a melted condition of the adhesive material, thereby facilitating ease of formation of the extension member by melting the adhesive member.

[0017] A stopper may be formed in the downstream end of the flow path of the flow path member for arresting flow of the adhesive material of the adhesive member when melted into the flow path.

[0018] A slit may be formed in at least one of the adhesive member and the nozzle base member around the outlet path for absorbing thermal deformation of the one of the adhesive member and the nozzle base member when bonded to the flow path member.

[0019] The slit has a length extending perpendicular to a direction in which the at least one of the adhesive member and the nozzle base member is subjected to a greater thermal deformation.

[0020] A first slit and a second slit may alternatively be provided. The first slit is formed in at least one of the adhesive member and the nozzle base member around the outlet path and has a length extending substantially perpendicular to a first direction in which the at least one of the adhesive member and the nozzle base member is subjected to a greater thermal deformation. The second slit is formed in at least one of the adhesive member and the nozzle base member around the outlet path and has a length extending substantially perpendicular to a second direction in which the at least one of the adhesive member and the nozzle base member is subjected to a smaller thermal deformation. The first slit is longer than the second slit.

[0021] According to the third aspect of the invention, there is provided a liquid drop emitter which comprises: an emitter body, a nozzle base member, and an adhesive member. The emitter body includes a micropump provide with a liquid inlet path into which liquid enters, a compression chamber compressing the liquid inputted from the liquid inlet path, and a liquid outlet path into which the compressed liquid flows out of the compression chamber. The nozzle base member is made of a material having a given Young's modulus Es and defines an outlet of a nozzle from which a drop of the liquid is emitted. The adhesive member is made of an adhesive material having a given Young's modulus Ea and disposed between the emitter body and the nozzle base member to establish a joint therebetween in fluid communication of the outlet of the nozzle and the liquid outlet path of the emitter body. A ratio of the Young's modulus Es to the Young's modulus Ea (i.e., Es / Ea) is within a range of 1.4 to 500, thereby facilitating absorption or dampening of vibrations through the adhesive member which arise from application of pressure of a jet of liquid from the composite nozzle to the nozzle base member, which results in stability of the meniscus of a drop of the liquid from the nozzle.

[0022] According to the fourth aspect of the invention, there is provided a liquid drop emitter which comprises an emitter body, a nozzle base, an adhesive member, and an extension member. The emitter body includes a liquid inlet path into which liquid enters, a compression chamber compressing a micropump, the liquid inputted from the liquid inlet path, and a liquid outlet path into which the compressed liquid flows out of the compression chamber. The nozzle base member defines an outlet of a nozzle from which a drop of the liquid is emitted. The adhesive member is made of an adhesive material and disposed between the emitter body and the nozzle base member to establish a joint therebetween in fluid communication of the outlet of the nozzle with the liquid outlet path of the emitter body. The first nozzles has an extension member extends from the first nozzle to the flow path of the flow path member along a periphery of an inner surface of the flow path. The feature of this invention is that a total length of the adhesive member including the extension member and the nozzle base member in a direction of emission of a drop of liquid is greater than the sum of the thickness of the adhesive member and the thickness of the nozzle base member.

[0023] In the preferred mode of the invention, the adhesive member has a given Young's modulus Ea. The nozzle base member has a given Young's modulus Es. A ratio of the Young's modulus Es to the Young's modulus Ea (i.e., Es / Ea) is selected within a range of 1.4 to 500.

[0024] A flow path defined by an inner surface of the extension member and the inner surface of the outlet of the nozzle has an inner diameter decreasing at a constant rate from the extension member to the nozzle.

[0025] A slit may be formed in at least one of the adhesive member and the nozzle base member around a path of the outlet of the nozzle leading to the liquid outlet path of the emitter body for absorbing thermal deformation of the one of the adhesive member and the nozzle base member when bonded to the emitter body.

[0026] The slit may have a length extending perpendicular to a direction in which the at least one of the adhesive member and the nozzle base member is subjected to a greater thermal deformation.

[0027] A first slit and a second slit may alternatively be provided. The first slit is formed in at least one of the adhesive member and the nozzle base member around the path of the outlet of the nozzle leading to the liquid outlet path of the emitter body and has a length extending substantially perpendicular to a first direction in which the at least one of the adhesive member and the nozzle base member is subjected to a greater thermal deformation. The second slit is formed in at least one of the adhesive member and the nozzle base member around the path of the outlet of the nozzle and has a length extending substantially perpendicular to a second direction in which the at least one of the adhesive member and the nozzle base member is subjected to a smaller thermal deformation. The first slit is longer than the second slit.

[0028] According to the fifth aspect of the invention, there is provided a method of fabricating a composite nozzle which comprises the steps of: (a) forming a laminate of a nozzle base plate and an adhesive layer; (b) drilling a hole in the laminate to define a nozzle therein; and (c) attaching the laminate to a flow-path base in fluid communication of the nozzle with a flow path formed in the flow-path base.

[0029] In the preferred mode of the invention, drilling the hole in the laminate is accomplished by radiating a laser beam to the laminate from the adhesive layer, thereby allowing the hole to have an inner diameter decreasing from the adhesive layer to the nozzle base plate at a constant rate and also eliminating a misalignment of an outlet path of the nozzle between the adhesive layer and the nozzle base plate.

[0030] The adhesive layer has a given Young's modulus Ea The nozzle base plate has a given Young's modulus Es. A ratio of the Young's modulus Es to the Young's modulus Ea (i.e., Es / Ea) is within a range of 1.4 to 500.

[0031] The adhesive layer has good wetability with the flow-path base in a melted condition of the adhesive layer.

[0032] According to the sixth aspect of the invention, there is provided a method of fabricating a liquid drop emitter which comprises the steps of: (a) forming a laminate of a nozzle base plate and an adhesive layer; (b) drilling a hole in the laminate from the adhesive layer to define a nozzle therein; (c) preparing an emitter body including a liquid inlet path into which liquid enters, a compression chamber compressing the liquid inputted from the liquid inlet path through a micropump, and a liquid outlet path into which the compressed liquid flows out of the compression chamber; (d) attaching the laminate to the emitter body to establish a joint therebetween in fluid communication of the nozzle with the liquid outlet path of the emitter body.

[0033] In the preferred mode of the invention, drilling the hole in the laminate is accomplished by radiating a laser beam to the laminate from the adhesive layer, thereby allowing the hole to have an inner diameter decreasing from the adhesive layer to the nozzle base plate at a constant rate and also eliminating a misalignment of an outlet path of the nozzle between the adhesive layer and the nozzle base plate. This ensures a desired velocity at which a drop of liquid is enabled to be discharged straight from the nozzle and desired locations of the drop deposited on a substrate.

[0034] The adhesive layer has a given Young's modulus Ea The nozzle base plate has a given Young's modulus Es. A ratio of the Young's modulus Es to the Young's modulus Ea (i.e., Es / Ea) is within a range of 1.4 to 500. The adhesive layer has good wetability with an inner wall of the liquid outlet path in a melted condition of the adhesive layer.

BRIEF DESPCRIPTION OF THE DRAWINGS

[0035] The present invention will be understood more fully from the detailed description given hereinbelow and from the accompanying drawings of the preferred embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments but are for the purpose of explanation and understanding only.

[0036] In the drawings:

Fig. 1 is a perspective view which shows a liquid drop emitter according to the invention;

Fig. 2 is a vertical sectional view which shows an internal structure of the liquid drop emitter of Fig. 1;

Fig. 3 is a plan view which shows the liquid drop emitter of Fig. 1;

Fig. 4 is a bottom view which shows the liquid drop emitter of Fig. 1;

Fig. 5 is a partially sectional view which shows a composite nozzle;

Fig. 6 is a sectional view which shows one of fabricating processes of the liquid drop emitter of Fig. 1;

Fig. 7 is a sectional view which shows one of fabricating processes of the liquid drop emitter of Fig. 1 which drills a hole to define a nozzle;

Fig. 8 is a sectional view which shows one of fabricating processes of the liquid drop emitter of Fig. 1 which drills a hole to define a composite nozzle;

Fig. 9 is a sectional view which shows one of fabricating processes of the liquid drop emitter of Fig. 1 which attaches a laminate in which a composite nozzle is formed to a body of the emitter;

Figs. 10, 11, 12, 13, and 14 are sectional views which show another fabricating method of the liquid drop emitter of Fig. 1;

Fig. 15 is a partially bottom view which shows the first modification of structure of the liquid drop emitter of Fig. 1;

Fig. 16 is a vertical sectional view of Fig. 15;

Fig. 17 is a partially sectional view which shows the second modification of structure of the liquid drop emitter of Fig. 1;

Fig. 18 is a partially sectional view which shows the third modification of structure of the liquid drop emitter of Fig. 1; and

Fig. 19 is a partially sectional view which shows the fourth modification of structure of the liquid drop emitter of Fig. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Referring to the drawings, wherein like reference numbers refer to like parts in several views, particularly to Fig. 1, there is shown a liquid drop emitter 10 according to the first embodiment of the invention which is suited to emit drops of liquid containing DNA fragments and deposit them on a substrate in a dense array of dots. Note that each drawing is not to scale and should not be used to specify dimensions of parts of the liquid drop emitter 10, which will be defined in discussion below.

[0038] The liquid drop emitter 10 consists essentially of a flow-path base plate 11, an actuator assembly 12, a lamination 13, and a liquid inlet block 14. The flow-path base plate 11 has a plurality of flow paths formed therein. The actuator assembly 12 is installed on the flow-path base plate 11 and, as will be described later in detail, works to change volumes of compression chambers to emit minute drops of liquid. The lamination 13 is attached to the bottom of the flow-path base plate 11 and has formed therein composite nozzles 26 which define outlets from which drops of liquid are discharged. The liquid inlet block 14 is disposed on an upper rear surface of the flow-path base plate 11 (i.e., on the right side, as viewed in the drawing). The liquid drop emitter 10 also has a plurality of micropipettes 15 arrayed at a given interval in parallel in a Y-direction, as indicated in the drawing.

[0039] The flow-path base plate 11 is made of a laminate of a lower layer 16 to which the lamination 13 is attached, a middle layer 17, and an upper layer 18. The layers 16, 17, and 18 are formed by laying green sheets made of a ceramic material such as zirconia to overlap each other and sintering them.

[0040] The lower layer 16 has, as clearly shown in Figs. 1 and 2, a plurality of outlet holes 16A formed in a front end portion thereof (i.e., a right end portion as viewed in Figs. 1 and 2). The outlet holes 16A are arrayed at a given interval in the Y-direction and communicate with the composite nozzles 26 of the lamination 13, respectively.

[0041] The middle layer 17 has a plurality of flow holes 17A formed in a front end portion thereof in alignment with the outlet holes 16A of the lower layer 16. The flow holes 17A communicate with the outlet holes 16A, respectively, and are greater in diameter than them. The middle layer 17 also has a plurality of elongated holes 17B each formed on a rear side of one of the flow holes 17A in an X-direction, as indicated in Fig. 1. The elongated holes 17B define liquid sumps 19 between the upper and lower layers 18 and 16.

[0042] The upper layer 18 has a plurality of flow holes 18A formed in a front end portion thereof (i.e., an X-direction in Fig. 1) in alignment with the flow holes 17A of the middle layer 17. The flow holes 18A communicate with the flow holes 17A, respectively, and are greater in diameter than them. The upper layer 18 also has formed therein flow holes 18B and 18C. Each of the flow holes 18B communicates with a downstream end of one of the liquid sumps 19. Each of the flow holes 18C communicates with an upstream end of one of the liquid sumps 19.

[0043] The lower layer 16, the middle layer 17, and the upper layer 18 are, as described above, made of a ceramic material. For instance, stabilized zirconia, partially stabilized zirconia, alumina, magnesia, or silicon nitride may be used. Of these, the stabilized zirconia and partially stabilized zirconia are preferable in terms of mechanical strength and toughness.

[0044] The actuator assembly 12 is made up of a bottom plate 20, a cavity-forming plate 21, a diaphragm 22, and piezoelectric/electrostrictive devices 23. The bottom plate 20 is disposed on a front half of the upper surface of the upper layer 18 of the flow-path base plate 11. The diaphragm 22 covers the cavity-forming plate 21. The cavity-forming plate 21 is disposed on the bottom plate 20 and has formed therein elongated holes 21A which define cavities 27 between the bottom plate 20 and the diaphragm 22. The cavities 27 work as compression chamber for discharging drops of liquid from the composite nozzles 26. The piezoelectric/electrostrictive devices 23 are mounted on the upper surface of the diaphragm 22 and work as micropumps which press the diaphragm 22 to change the volume of the cavities 27.

[0045] The bottom plate 20 has formed therein flow holes 20A and 20B formed therein coaxially in alignment with the flow holes 18A and 18B of the upper layer 18 of the flow-path base plate 11. The flow holes 20A communicate with the flow holes 18A, respectively, and are greater in diameter than them. The flow holes 20B communicate with the flow holes 18B, respectively, and are smaller in diameter than them. The flow holes 20A and 20B communicate with each other through the cavities 27. The diaphragm 22 is made of a rectangular thin plate which covers the whole of the upper surface of the cavity-forming plate 21.
The bottom plate 20, the cavity-forming plate 21, and the diaphragm 22 are each made by sintering a ceramic green sheet.

[0046] Specifically, stabilized zirconia, partially stabilize zirconia, alumina, magnesia, or silicon nitride may be used. Of these, the stabilized zirconia and partially stabilized zirconia are suitable for the diaphragm 22 in terms of mechanical strength and toughness and most preferable because it is lower in reaction with a piezoelectric film or an electrode. In a case where the diaphragm 22 is made of stabilized zirconia or partially stabilized zirconia, it is advisable that an at least portion of the diaphragm on which the piezoelectric/electrostrictive devices 23 are mounted contain an additive of alumina or titanium.

[0047] Each of the piezoelectric/electrostrictive devices 15 is formed by a laminate of piezoelectric/electrostrictive layers each made of a ceramic material which may contain one or a mixture of lead zirconate, lead titanate, lead magnesium-niobate, lead manganese tantalate, lead nickel niobate, lead zinc niobate, lead manganese niobate, lead antimony stannate, lead manganese tungstate, lead cobalt niobate, and barium titanate. In this embodiment, a mixture of lead zirconate, lead titanate, and lead magnesium-niobate is used as a main component of the ceramic material because it is lower in reaction with firing of a piezoelectric film as well as having high electromechanical coupling factor and piezoelectric constant. The piezoelectric/electrostrictive devices 15 have a know structure, and details thereof such as electrode pads are omitted here.

[0048] The liquid inlet block 14 is, as described above, secured on a rear half of the upper surface of the flow-path base plate 11. The liquid inlet block 14 is of a substantially rectangular parallelopiped shape and spaced apart from the rear end of the actuator assembly 12. The liquid inlet block 14 has formed therein liquid inlets 14A each of which leads to one of the flow holes 18C of the upper layer 18 of the flow-path base plate 11. The liquid inlets 14A are arrayed at a regular interval in the Y-direction.

[0049] The lamination 13 is made up of a nozzle base layer 24 and an adhesive layer 25. The nozzle base layer 24 may be made of polyester (PET) film, stainless steel (SUS304), alumina, or partially stabilized zirconia (PSZ). The adhesive layer 25 may be made of epoxy bonding film (thermosetting) or polyethylene bonding film (thermoplastic). The lamination 13, as already described, has formed therein the composite nozzles 26 each of which communicates with one of the outlet holes 16A formed in the lower layer 16 of the flow-path base plate 11. The nozzle base layer 24 has formed therein smaller tapered holes 24A each of which defines a downstream portion of an outlet path defined in one of the composite nozzles 26. The adhesive layer 25 has formed therein larger tapered holes 25A each of which defines an upstream portion of the outlet path defined in one of the composite nozzles 26. An inner surface of each of the tapered holes 24A is flush with an inner surface of one of the tapered holes 25A to define a conical inner surface of each of the composite nozzles 26.

[0050] The liquid drop emitter 10 of this embodiment features a ratio of a Young's modulus Es of the nozzle base layer 24 to a Young's modulus Ea of the adhesive layer 25 (i.e., Es / Ea) which lies within a range of 1.4 to 500. Examples of Young's moduli and materials of the nozzle base layer 24, the adhesive layer 25, and the lower layer 16 of flow-path base plate 11 are listed below.

Parts Name	Material	Young's modulus (Gpa)
Nozzle base layer	Polyester (PET) film	4
	Stainless steel (SUS304)	197
	Alumina	360
	Partially stabilized zirconia (PSZ)	205
Adhesive layer	Epoxy bonding film (thermosetting)	1.2 - 2.9
	Polyethylene bonding film (thermoplastic)	0.4 - 1.3
Flow-path base plate	Partially stabilized zirconia (PSZ)	205

[0051] The above materials of the nozzle base layer 24 and the adhesive layer 25 are so selected as to have the Young's modulus ratio (Es / Ea) within a range of 1.4 to 500. This facilitates absorption or dampening of vibrations through the adhesive layer 25 which arise from application of pressure of a jet of liquid from each of the composite nozzles 26 to the nozzle base layer 24, thus resulting in stability of the meniscus. Too small the Young's modulus Ea of the adhesive layer 25 will result in a lack of pressure required to emit a drop of liquid from each of the composite nozzles 26.

[0052] Particularly, in a case where the liquid drop emitter 10 is used to emit drops of liquid containing DNA fragments and deposit them on a substrate in a dense array of dots to produce a DNA chip, it is advisable that the Young's modulus Es of the nozzle base layer 24 be 4Gpa to 197Gpa, and Young's modulus Ea of the adhesive layer 25 be 0.4Gpa to 2.9Gpa because the viscosity of the liquid containing DNA fragments is usually within a range of 3cp to 10cp. In this case, the Young's modulus ratio (Es / Ea) is preferably defined within a range of 1.4 to 200, and more preferably within a range of 1.4 to 10.

[0053] Each of the composite nozzles 26 is, as can be seen from Fig. 5, decreased in diameter at a constant rate in a Z-direction (i.e., the thickness-wise direction of the lamination 13) and has a smooth inner surface which extends through the nozzle base layer 24 and the adhesive layer 25 and is axi-symmetric:

[0054] The adhesive layer 25 has annular extensions 25B each of which forms an upstream end portion of the outlet path of one of the composite nozzles 26. Each of the annular extensions 25B is flush with the inner surface of one of the composite nozzles 26 formed in the nozzle base layer 24 and the adhesive layer 25 and extends to an inner surface of one of the outlet holes 16A of the bottom layer 16 without any clearance therebetween, thereby avoiding formation of a step between the bottom layer 16 and the adhesive layer 25 in which bubbles may stay. This ensures the stability of emission of a drop of liquid from each of the composite nozzles 26 and also avoids micro separation of the adhesive layer 25 from the bottom layer 16 caused by accumulation of bubbles on an interface between the adhesive layer 25 and the bottom layer 16. Each of the annular extensions 25B is bonded to the inner surface of one of the outlet holes 16A, thereby increasing the rigidity of the composite nozzles 26, which results in a decrease in loss of pressure produced by the piezoelectric/electrostrictive devices 23 required to emission of drops of liquid from the composite nozzles 26 at a desired flow rate.

[0055] An example of operation of the liquid drop emitter 10 to emit drops of liquid containing DNA fragments and deposit them on a substrate in a dense array of dots to produce a DNA chip will be described below.

[0056] First, a predetermined amount of buffer solution is put in each of the liquid inlets 14A of the liquid inlet block 14. Subsequently, liquid samples containing different DNA fragments are put in the liquid inlets 14A, respectively. Next, the piezoelectric/electrostrictive devices 23 of the actuator assembly 12 are energized to compress the volumes of the cavities 15 through the diaphragm 22 to pass the buffer solution through all the flow paths containing the micropipettes 15 in lamina flow and discharges it from the composite nozzles 26 completely, thereby filling all the flow paths with the liquid samples.

[0057] Afterwards, the piezoelectric/electrostrictive devices 23 of the actuator assembly 12 are actuated to emit drops of the liquid samples and deposit them on a substrate in a dense array of spots of a desired size. This operation is repeated to produce a required number of dense arrays of the spots on the substrate to fabricate the DNA chip.

[0058] As already described, a ratio of the Young's modulus Es of the nozzle base layer 24 to the Young's modulus Ea of the adhesive layer 25 (i.e., Es / Ea) is set within a range of 1.4 to 500, thereby enhancing the ability of the adhesive layer 25 to absorb or dampen vibrations arising from application of pressure of the liquid compressed by the piezoelectric/electrostrictive devices 23 to the heads of the composite nozzles 26 formed in the nozzle base layer 24, thus resulting in stability of the meniscus of the liquid passing the heads of the composite nozzles 26.

[0059] The adhesive layer 25 has, as described above, the annular extensions 25B each of which extends to the inner surface of one of the outlet holes 16A of the bottom layer 16, thereby resulting in an increase in total area of the adhesive layer 25 bonded to the lower layer 16 of the flow-path base plate 11 to increase the strength of a joint between the nozzle base layer 24 and the lower layer 16. This results in an increase in rigidity of the composite nozzles 26, thereby decreasing a loss of pressure produced by the piezoelectric/electrostrictive devices 23 required to emission of drops of liquid from the composite nozzles 26 at a desired flow rate.

[0060] Each of the annular extensions 25B is flush with the inner surface of one of the composite nozzles 26 formed in the nozzle base layer 24 and the adhesive layer 25 and extends to one of the outlet holes 16A of the bottom layer 16 without any clearance therebetween, thereby avoiding formation of a step between the bottom layer 16 and the adhesive layer 25 in which bubbles may stay. Each of the composite nozzles 26 is, as described above, decreased in diameter at a constant rate to the head thereof, thereby establishing emission of a drop of liquid along a longitudinal center line of the composite nozzle 26, thus improving the accuracy of locating each deposit on the DNA chip.

[0061] A fabrication method of the liquid drop emitter 10 will be described below with reference to Figs. 6 to 9.

[0062] First, the nozzle base layer 24 is, as shown in Fig. 6, attached to the adhesive layer 25 to produce the lamination 13. The adhesive layer 25 is made of a film which shows good wetability in a melted condition with the bottom layer 16 of the flow-path base plate 11.

[0063] Next, a laser beam of a preselected diameter is, as shown in Figs. 7 and 8, radiated in the form of a spot to the adhesive layer 25 to drill a tapered hole in the lamination 13, thereby forming each of the composite nozzles 26.

[0064] After formation of an array of the composite nozzles 26 in the lamination 13, the lamination 13 is attached to a body 10A of the liquid drop emitter 10 made up of the flow-path base plate 11, the actuator assembly 12, and the liquid inlet block 14. This attachment is achieved by heating the adhesive layer 26 to melt it and affixing the adhesive layer 26 to the bottom layer 6 of the flow-path base plate 11 in alignment of each of the composite nozzles 26 with one of the outlet holes 16A of the bottom layer 16. The melted adhesive layer 26 flows at the inner surfaces of the tapered holes thereof into the outlet holes 16A of the bottom layer 16, thereby forming the annular extensions 25B, as shown in Fig. 5. Subsequently, the adhesive layer 25 is solidified, thereby completing the liquid drop emitter 10, as shown in Figs. 1 and 2.

[0065] Each of the composite nozzles 26 is, as described above, machined by drilling a single hole in the lamination 13 through radiation of a laser beam, thus facilitating ease of formation of the composite nozzles 26 which is symmetric with respect to a direction of emission of a drop of liquid. The use of the laser beam ensures the smoothness of the inner surfaces of the composite nozzles 26, thereby resulting in stability of the meniscus of drops of liquid emitted from the composite nozzles 26, which improves the accuracy of locating the drops on a substrate.

[0066] Another fabrication method of the liquid drop emitter 10 will be described below with reference to Figs. 10 to 14. In the following discussion, the same reference numbers will be employed as indicating several ceramic parts and their performs before fired (i.e., green sheets) for convenience sake.

1 The ceramic base plate 30 of a given size, as shown in Fig. 10, is prepared as a base for screen printing and firing. The ceramic base plate 30 is made of oxide such as zirconia, aluimna, or magnesia.

2 Paste (not shown) containing dispersed carbon powder or theobromine powder is applied to the ceramic base plate 30 using, for example, a metal screen and dried to form a film. The film will disappear in a subsequent firing process and serve to facilitate ease of separation of the flow-path base plate 11 from the ceramic base plate 30.

3 The perform 16 of the bottom layer 16 is, as shown in Fig. 10, placed on the ceramic base plate 30. The perform 16 is prepared by drying a partially stabilized zirconia (PSZ) paste and forming the outlet holes 16A.

4 The perform 17 of the middle layer 17 is, as shown in Fig. 10, placed on the perform 16. The perform 17 is prepared by drying a partially stabilized zirconia (PSZ) paste and forming the flow holes 17A and the elongated holes 17B.

5 The perform 18 of the upper layer 18 is, as shown in Fig. 10, placed on the perform 17. The perform 18 is prepared by drying a partially stabilized zirconia (PSZ) paste and forming the flow holes 18A and 18B.

6 The perform 14 of the liquid inlet block 14 in which the liquid inlets 14A are formed is, as shown in Fig. 10, placed on the perform 18.

7 The structure made up of the performs 14 to 18 and the ceramic base plate 30 is heated at a velocity required to have organic matter of each layer and the film formed on the ceramic base plate 30 disappear completely and fired at a maximum of 1100°C to 1300°C, thereby causing the film to disappear from the ceramic base plate 30, which allows the ceramic base plate 30 to be separated, as shown in Fig. 11, from the flow-path base plate 11.

8 The nozzle base layer 24 is, as shown in Fig. 12, attached through the adhesive layer 25 to a lower surface of the bottom layer 16 of the flow-path base plate 11 on which the liquid inlet block 14 is mounted. The adhesive layer 25 is formed by a bonding film such as an epoxy bonding film (thermosetting) or a polyethylene bonding film (thermoplastic) which exhibits good wetability with the bottom layer 16 made of partially stabilized zirconia.

9 A laser beam L of a preselected diameter, as shown in Fig. 13, is radiated from above the upper surface of the flow-path base plate 11 in alignment with a longitudinal center line extending through the flow holes 18A and 17A and the outlet hole 16A to form a tapered hole through the adhesive layer 25 and the nozzle base layer 24, thereby forming each of the composite nozzles 26. The radiation of the laser beam L causes the adhesive layer 25 to be melted, so that it flows at the inner surfaces of the tapered holes thereof into the outlet holes 16A of the bottom layer 16, thereby forming the annular extensions 25B, as shown in Fig. 5. The total length t2 of the inner surface of each of the composite holes 26 will, thus, be greater than the total t1 of thickness ta of the adhesive layer 25 and thickness ts of the nozzle base layer 24.

10 Finally, the pre-prepared actuator assembly 12 is, as shown in Fig. 14, glued to the upper layer 18 of the flow-path base plate 11 in alignment of the flow holes 20A and 20B formed in the bottom plate 20 with the flow holes 18A and 18B of the upper layer 18, respectively.

[0067] The formation of the composite nozzles 26 is, as described above, accomplished after the nozzle base layer 24 is joined to the flow-path base plate 11 through the adhesive layer 25, thus resulting in improved accuracy of locations of the composite nozzles 26. The formation of each of the composite nozzles 26 is achieved by drilling a single hole using the laser beam L, thus ensuring symmetry of the inner surface of the composite nozzle 26 with respect a direction of emission of a drop of liquid. The use of the laser beam L ensures the smoothness of the inner surfaces of the composite nozzles 26, thereby resulting in stability of the meniscus of drops of liquid emitted from the composite nozzles 26, which improves the accuracy of locating the drops on a substrate. Further, the radiation of the laser beam L onto the adhesive layer 25 after attached to the bottom layer 16 of the flow-path base plate 11 causes a laser-melted portion of the adhesive layer 25 to flow into the inner surface of the outlet holes 16A of the bottom layer 16, thus resulting in an increase in length of the inner surface of the composite nozzles 26.

[0068] While, in the above embodiments, the composite nozzles 26 are formed by drilling a laminate of the nozzle base layer 24 and the adhesive layer 25, the nozzle base layer 24 may be drilled and then joined to the lower surface of the flow-path base plate 11 using an adhesive. A ratio of the Young's modulus Es of the nozzle base layer 24 to the Young's modulus Ea of the adhesive (i.e., Es / Ea) is preferably within a range of 1.4 to 500.

[0069] Figs. 15 and 16 show the first modification of the structure of the liquid drop emitter 10.

[0070] The laminate 13 of the nozzle base layer 24 and the adhesive layer 25 has a plurality of slits 31A and 31B formed all around each of the composite nozzles 26 in order to absorb thermal deformation of the nozzle base layer 24 and the adhesive layer 25. The slits 31A extend parallel to each other across the composite nozzle 26 in a direction b. The slits 31B extend parallel to each other across the composite nozzle 26 in a direction a perpendicular to the direction b. The slits 31A are longer than the slits 31B. This is suitable for a case where the nozzle base layer 24 and the adhesive layer 25 undergo a large-scale thermal deformation in the direction a.

[0071] Fig. 17 shows the second modification of the liquid drop emitter 10 which is different from the one shown in Figs. 15 and 16 only in that slits 32 are formed only in the nozzle base layer 24 in order to absorb thermal deformation of, especially the nozzle base layer 24.

[0072] Fig. 18 shows the third modification of the liquid drop emitter 10 which is different from the one shown in Figs. 15 and 16 only in that slits 33 are formed only in the adhesive layer 25 in order to absorb thermal deformation of, especially the adhesive layer 25.

[0073] The slits, as shown in Figs. 15 to 18, may either have the same length or different lengths.

[0074] While the present invention has been disclosed in terms of the preferred embodiments in order to facilitate better understanding thereof, it should be appreciated that the invention can be embodied in various ways without departing from the principle of the invention. Therefore, the invention should be understood to include all possible embodiments and modifications to the shown embodiments witch can be embodied without departing from the principles of the invention as set forth herein. For instance, the piezoelectric/electrostrictive devices 23 may be replaced with micropumps having another structure. The annular extensions 25B may be omitted. An annular groove 16B, as shown in Fig. 19, may be formed in a lower end of each of the outlet holes 16A which works as a stopper to arrest the flow of the melted portion of the adhesive layer 25 into the outlet hole 16A. Each of the flow-path base plate 11 and the actuator assembly 12 may be made of ceramic layers of a number different from that in the above embodiments.

Claims

1. A composite nozzle comprising:

a first nozzle formed in an adhesive member made of an adhesive material having a given Young's modulus Ea, said first nozzle defining an upstream portion of an outlet path of the composite nozzle;

a second nozzle, formed in a nozzle base member made of a material having a given Young's modulus Es, defining a downstream portion of the outlet path of the composite nozzle, the nozzle base member being attached through the adhesive member to a flow path member in fluid communication of said second nozzle through said first nozzle with a flow path formed in the flow path member leading to an inlet,

wherein a ratio of the Young's modulus Es to the Young's modulus Ea (i.e., Es / Ea) is within a range of 1.4 to 500.

2. A composite nozzle as set forth in claim 1, wherein the adhesive member has good wetability with the flow path member in a melted condition of the adhesive material.

3. A composite nozzle as set forth in claim 1, further comprising a slit formed in at least one of the adhesive member and the nozzle base member around the outlet path.

4. A composite nozzle as set forth in claim 3, wherein the slit has a length extending perpendicular to a direction in which the at least one of the adhesive member and the nozzle base member is subjected to a greater thermal deformation.

5. A composite nozzle as set forth in claim 3, further comprising a first slit and a second slit, said first slit being formed in at least one of the adhesive member and the nozzle base member around the outlet path and having a length extending substantially perpendicular to a first direction in which the at least one of the adhesive member and the nozzle base member is subjected to a greater thermal deformation, said second slit being formed in at least one of the adhesive member and the nozzle base member around the outlet path and having a length extending substantially perpendicular to a second direction in which the at least one of the adhesive member and the nozzle base member is subjected to a smaller thermal deformation, and wherein said first slit is longer than said second slit.

6. A composite nozzle comprising:

a first nozzle formed in an adhesive member made of an adhesive material, said first nozzle defining an upstream portion of an outlet path of the composite nozzle; and

a second nozzle, formed in a nozzle base member, defining a downstream portion of the outlet path of the composite nozzle, the nozzle base member being attached through the adhesive member to a flow path member in fluid communication of said second nozzle through said first nozzle with a flow path formed in the flow path member leading to an inlet,

wherein said first nozzle has an extension member extending from said first nozzle to the flow path of the flow path member along a periphery of an inner surface of the flow path.

7. A composite nozzle as set forth in claim 6, wherein the adhesive member has a given Young's modulus Ea, and the nozzle base member has a given Young's modulus Es, and wherein a ratio of the Young's modulus Es to the Young's modulus Ea (i.e., Es / Ea) is within a range of 1.4 to 500.

8. A composite nozzle as set forth in claim 6, wherein the outlet path has an inner diameter decreasing at a constant rate from said extension member to said second nozzle.

9. A composite nozzle as set forth in claim 6, wherein the adhesive member has good wetability with the flow path member in a melted condition of the adhesive material.

10. A composite nozzle as set forth in claim 6, further comprising a stopper formed in the downstream end of the flow path of the flow path member for arresting flow of the adhesive material of the adhesive member when melted into the flow path.

11. A liquid drop emitter comprising:

an emitter body including a micropump provided with a liquid inlet path into which liquid enters, a compression chamber compressing the liquid inputted from said liquid inlet path, and a liquid outlet path into which the compressed liquid flows out of said compression chamber;

a nozzle base member made of a material having a given Young's modulus Es, defining an outlet of a nozzle from which a drop of the liquid is emitted; and

an adhesive member made of an adhesive material having a given Young's modulus Ea, said adhesive member being disposed between said emitter body and said nozzle base member to establish a joint therebetween in fluid communication of the outlet of the nozzle and the liquid outlet path of said emitter body,

wherein a ratio of the Young's modulus Es to the Young's modulus Ea (i.e., Es / Ea) is within a range of 1.4 to 500.

12. A liquid drop emitter as set forth in claim 11, further comprising a slit formed in at least one of the adhesive member and the nozzle base member around a path of the outlet of the nozzle leading to the liquid outlet path of said emitter body.

13. A liquid drop emitter as set forth in claim 12, wherein the slit has a length extending perpendicular to a direction in which the at least one of the adhesive member and the nozzle base member is subjected to a greater thermal deformation.

14. A composite nozzle as set forth in claim 12, further comprising a first slit and a second slit, said first slit being formed in at least one of the adhesive member and the nozzle base member around a path of the outlet of the nozzle leading to the liquid outlet path of said emitter body and having a length extending substantially perpendicular to a first direction in which the at least one of the adhesive member and the nozzle base member is subjected to a greater thermal deformation, said second slit being formed in at least one of the adhesive member and the nozzle base member around the path of the outlet of the nozzle and having a length extending substantially perpendicular to a second direction in which the at least one of the adhesive member and the nozzle base member is subjected to a smaller thermal deformation, and wherein said first slit is longer than said second slit.

15. A liquid drop emitter comprising:

an emitter body including a micropump provided with a liquid inlet path into which liquid enters, a compression chamber compressing the liquid inputted from said liquid inlet path and a liquid outlet path into which the compressed liquid flows out of said compression chamber;

a nozzle base member defining an outlet of a nozzle from which a drop of the liquid is emitted;

an adhesive member made of an adhesive material, disposed between said emitter body and said nozzle base member to establish a joint therebetween in fluid communication of the outlet of the nozzle with the liquid outlet path of said emitter body; and

an extension member extending from said first nozzle to the flow path of the flow path member along a periphery of an inner surface of the flow path.

16. A liquid drop emitter as set forth in claim 15, wherein the adhesive member has a given Young's modulus Ea, and the nozzle base member has a given Young's modulus Es, and wherein a ratio of the Young's modulus Es to the Young's modulus Ea (i.e., Es / Ea) is within a range of 1.4 to 500.

17. A liquid drop emitter as set forth in claim 15, wherein a flow path defined by an inner surface of said extension member and the inner surface of the outlet of the nozzle has an inner diameter decreasing at a constant rate from said extension member to the nozzle.

18. A method of fabricating a composite nozzle comprising the steps of:

forming a laminate of a nozzle base plate and an adhesive layer; drilling a hole in said laminate to define a nozzle therein; and

attaching said laminate to a flow-path base in fluid communication of the nozzle with a flow path formed in the flow-path base.

19. A method as set forth in claim 18, wherein drilling the hole in said laminate is accomplished by radiating a laser beam to said laminate from the adhesive layer.

20. A method as set forth in claim 18, wherein the adhesive layer has a given Young's modulus Ea, and the nozzle base plate has a given Young's modulus Es, and wherein a ratio of the Young's modulus Es to the Young's modulus Ea (i.e., Es / Ea) is within a range of 1.4 to 500.

21. A method as set forth in claim 18, wherein the adhesive layer has good wetability with the flow-path base in a melted condition of the adhesive layer.

22. A method of fabricating a liquid drop emitter comprising the steps of:

forming a laminate of a nozzle base plate and an adhesive layer;

drilling a hole in said laminate from the adhesive layer to define a nozzle therein;

preparing an emitter body including a micropump provided with a liquid inlet path into which liquid enters, a compression chamber compressing the liquid inputted from said liquid inlet path , and a liquid outlet path into which the compressed liquid flows out of said compression chamber;

attaching said laminate to said emitter body to establish a joint therebetween in fluid communication of the nozzle with the liquid outlet path of said emitter body.

23. A method as set forth in claim 22, wherein drilling the hole in said laminate is accomplished by radiating a laser beam to said laminate from the adhesive layer.

24. A method as set forth in claim 22, wherein the adhesive layer has a given Young's modulus Ea, and the nozzle base plate has a given Young's modulus Es, and wherein a ratio of the Young's modulus Es to the Young's modulus Ea (i.e., Es / Ea) is within a range of 1.4 to 500.

25. A method as set forth in claim 22, wherein the adhesive layer has good wetability with an inner wall of the liquid outlet path in a melted condition of the adhesive layer.

Drawing