Micromachined fluidic coupler and method of making the same

Information

  • Patent Grant
  • 6672629
  • Patent Number
    6,672,629
  • Date Filed
    Thursday, July 18, 2002
    22 years ago
  • Date Issued
    Tuesday, January 6, 2004
    20 years ago
Abstract
A micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size, has a body which has a shape conforming the shape of the cavity into which the body must fit. A through hole is defined through the body. The through hole has a size conforming to the first size of the capillary. The capillary is disposable into the through hole so that the capillary is communicated to the orifice without the first and second sizes necessarily being the same. The cavity and the body have conforming slanting surfaces, and in particular the cavity and the body define truncated pyramidal shapes. The cavity and the body each have a truncated pyramidal shape. The pyramidal shape may be square, triangular, or conical. A method of fabricating the micromachined coupler is achieved either by micromaching or micromolding.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The invention relates to the field of fluidics and in particular to coupling devices used in microfluidic circuits.




2. Description of the Prior Art




Rapidly developing Micro Electro Mechanical Systems (MEMS) technology makes micro fluidic systems very attractive for many applications, such as micro heat exchangers, micro chromatographs, biochemical detectors, micro mass spectrometers, micro reactors, and micro fluid control systems (e.g., microchannels, micro valves, micro pumps, and micro flow meters). It is quite challenging to transfer fluids between a micro fluidic system and its macroscopic environment because of micron-scale dimensions. There is no effective and simple way to apply conventional fluidic couplers to microscale fluidic systems at this time. Currently, to achieve coupling, a tube with an inside diameter significantly larger than the size of the inlet or outlet is directly glued to the opening. The yield of this approach is usually very low due to tube misalignment and inlet or outlet blockage by excessive glue. In addition, the permissible number of couplings for a micro fluidic system is limited by the relatively large size of the tubing used, and may not be adequate for the system. Furthermore, such a coupling generally cannot withstand high pressures required in many applications.




In order to adapt to the rapidly growing demand for micro fluidic systems, a novel, low-cost, and highly reliable coupling technique is required. The micromachined fluidic couplers proposed and developed at the Caltech Micromachining Laboratory can fulfill this requirement.




BRIEF SUMMARY OF THE INVENTION




The invention comprises a micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size. The invention in particular comprises a substrate, and a cavity defined in the substrate defining the orifice. A body is provide which has a shape conforming the shape of the cavity. A through hole is defined through the body. The through hole has a size conforming to the first size of the capillary. The capillary is disposable into the through hole so that the capillary of the first size is coupled to the orifice of the second size without the first and second sizes necessarily being the same.




The cavity and the body have conforming slanting surfaces, and in particular the cavity and the body define truncated pyramidal shapes. The cavity and the body each have a truncated square pyramidal shape, a truncated triangular pyramidal shape, or a truncated conical shape.




The micromachined coupler may further comprise a tubing stopper defined in the through hole and/or a shoulder defined on a surface of the coupler for bonding to the substrate outside of the cavity.




Typically the size of the orifice is different than the size of the capillary.




The invention is also characterized as a method of fabricating a micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size comprising the steps of masking a substrate from which will a body of the micromachined coupler will be formed. The masking forms a pattern to define a pyramidal structure in the substrate. The masked substrate is anisotropically etched to form the pyramidal structure including a pit in the pyramidal structure. A surface of substrate opposite the pyramidal structure is then provided with a patterned mask. A prismatic hole is defined through the substrate and communicated with the pit to provide a through hole through the substrate.




The step of anisotropically etching the masked substrate to form the pyramidal structure forms a simple truncated structure or a truncated structure with a basal shoulder.




In one embodiment the step of defining a prismatic hole through the substrate does not completely remove the pit so that a tubing stop is formed by a remaining portion of the pit. The method further comprises the step of disposing a capillary into the prismatic hole in a sealed relationship therewith.




The step of anisotropically etching the masked substrate to form the pyramidal structure forms a square, triangular or conical truncated structure.




The invention is still further defined as a method of fabricating a micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size comprising the steps of defining a truncated pyramidal cavity in a micromachined mold. A material is disposed or deposited in the truncated pyramidal cavity to form a body of the coupler. A prismatic hole of a first size is defined through the body to define a through hole by deep reactive ion etching.




In another embodiment the method further comprises the step of defining by deep reactive ion etching a prismatic hole of a second size in the body aligned with the prismatic hole of the first size to define a tubing stop in the prismatic hole of the first size.




The invention now having been briefly summarized, turn to the following drawings wherein the invention may be better visualized and where like elements are reference by like numerals.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a diagrammatic perspective view of a microfluidic system coupled with capillaries by means of micromachined fluidic couplers.





FIG. 2

is a diagrammatic side cross-sectional view of a coupling of a capillary to the microfluidic system according to the invention as shown in the right side of the drawing and as shown in a conventional coupling without the benefit of the coupler of the invention in the left half of the drawing.





FIG. 3



a


is a plan top view of a single inlet or outlet pit shown in enlarged scale.





FIG. 3



b


is a cross-sectional view of the pit of

FIG. 3



a


as seen through lines


3





3


of

FIG. 3



a.







FIG. 4

is a three-quarter perspective, exploded view of the coupler of the invention shown in combination with the outlet/inlet of the fluidic system and capillary.





FIGS. 5



a


and


5




b


cross-sectional diagrammatic side views of the coupler of the invention fitted into inlets/outlets of different diameters or sizes.





FIGS. 6



a


and


6




a


′ are the side cross-sectional view and top plan view respectively of a first embodiment of the coupler.





FIGS. 6



b


and


6




b


′ are the side cross-sectional view and top plan view respectively of a second embodiment of the coupler.





FIGS. 6



c


and


6




c


′ are the side cross-sectional view and top plan view respectively of a third embodiment of the coupler.





FIG. 7

is a diagrammatic side cross-sectional view of still another embodiment of the coupler.





FIGS. 8



a


,


8




b


,


8




c


and


8




d


are cross-sectional side views of the invention illustrating the fabrication of the embodiment of

FIGS. 6



c


and


6




c′.







FIG. 9

is a side cross-sectional view of a coupler of the embodiment of

FIGS. 6



c


and


6




c


′ shown bonded to a substrate through a bonding layer.





FIGS. 10



a


,


10




b


,


10




c


and


10




d


illustrate the fabrication steps of molding a coupler.





FIG. 11

is a side cross-sectional view which shows the coupler of

FIG. 7

fitted to a microfluidic system with small straight inlets and outlets.





FIGS. 12



a


,


12




b


,


12




c


and


12




d


are side cross-sectional views which illustrate the fabrication of a coupler of FIG.


7


.











The invention and various ones of its embodiments now having been illustrated in the above drawings, turn to the following detailed description of the preferred embodiments.




DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




Micro fluidic couplers based on micromachining technology have been developed in the Caltech Micromachining Laboratory. By using the uniquely designed couplers, it is possible to easily align capillaries of different sizes to the inlet or outlet of a micro fluidic system. The couplers are strongly bonded directly to a fluidic system. For example, a thin layer of bonding material is applied between the mating surfaces. This coupling technique requires minimal preparation time and is low in complexity, yet provides a robust and high yield interconnect for micro fluidic systems. In addition, the fabrication cost for the couplers is inexpensive because of batch processing.




Micromachined fluidic couplers


10


are used to connect fluidic capillaries


12


to a microfluidic system


14


with inlets


16


and outlets


18


, hidden from view by couplers


10


in the depiction of

FIG. 1

, but explicitly shown in

FIG. 2

, that may differ from the capillaries


12


in both shape and size. By using such couplers


10


, a fluidic interconnection with multiple channels is built for the microfluidic system


14


as shown in the diagrammatic perspective view FIG.


1


.




In general, it is impractical to connect a fluidic capillary


12


directly to the inlet


16


or outlet


18


due to their different shapes and sizes. An intermediate object, i.e. a micromachined coupler


10


, must be introduced to achieve such a coupling. The coupler


10


is designed in such a way that a capillary


12


can be tightly placed into the size-matched hole


20


in the center of the coupler


10


and the coupler


10


can be conformably fitted into the size-matched inlet


16


or outlet


18


defined in substrate


22


as shown in the right half of FIG.


2


.




For example, the inlets


16


and outlets


18


in a fluidic system


14


built on a silicon chip or substrate


22


are the pits


26


usually etched into (100) silicon with an anisotropic wet etch (i.e. KOH, TMAH and EDP) through square openings


24


in the etching mask


28


as shown in

FIGS. 3



a


and


3




b


. Such a pit


26


has the pyramidal shape bonded by four (111) planes as shown in

FIGS. 3



a


and


3




b


, and there is yet no effective way to connect a capillary directly to such an inlet


16


or outlet


18


. However, a coupler


10


with the truncated pyramidal shape bonded by four (111) side walls can now be applied to make such a connection as shown in FIG.


4


. With the similar pyramidal shape formed by an anisotropic wet etching, the coupler


10


can be conformably fitted into the inlet


16


or outlet


18


. A capillary


12


can be placed tightly in the size-matched hole


20


etched in the center of the coupler


10


using deep reactive ion etching (DRIE). Later capillary


12


and coupler


10


can be firmly bonded together by various bonding techniques, such as gluing, polymer film bonding, indium solder bonding, or Au eutectic bonding.




Also, as shown in

FIGS. 5



a


and


5




b


, a single coupler


10


can be used for an inlet


16


or outlet


18


with various diameters by a variable fitting depth inherent in the design of coupler


10


.




Another embodiment of the invention is realized in a truncated pyramidal coupler


10


as shown in

FIGS. 6



a


,


6




b


and


6




c


and

FIGS. 6



a


′,


6




b


′ and


6




c


′.

FIGS. 6



a


and


6




a


′ as mentioned before show the simplest design in which a single through hole


20


on the axis of symmetry of the truncated pyramidal shape is provided. The embodiment of

FIGS. 6



b


and


6




b


′ have the same outside shape as coupler


10


of

FIG. 6



a


and


6




a


′, but has a tubing stopper


30


inside hole


20


defined as lower circumferential lip in which a hole


32


is defined which has a smaller diameter than hole


20


through the body of coupler


10


.

FIGS. 6



c


and


6




c


′ depict a third embodiment which has a shoulder


34


, which can be bonded to the chip substrate


22


of the micro fluidic system


14


to secure the coupling thereto.




The micromachined fluidic couplers


10


can be made for inlets


16


and outlets


18


with many other shapes. As shown in

FIG. 7

, an alignment post


36


made in the same shape as the inlet


16


or outlet


18


can be fitted into the opening


38


, and the adjacent, large flat bonding area


40


can be bonded to the chip substrate


22


of the micro fluidic system


14


. As discussed before, the capillary tubing


12


can be put into the center hole


20


and then bonded to the coupler


10


. A stopper


30


is illustrated in

FIG. 7

, but may be eliminated if desired.




With micromachined couplers


10


, the coupling process becomes less complicated. First, by using the uniquely designed micromachined couplers


10


, small capillaries


12


are easily aligned with the inlets


16


and outlets


18


of a micro fluidic system


14


. Second, by coating a thin layer of bonding material on the surfaces of coupler


10


, micromachined coupler


10


can readily be bonded to a fluidic system


14


. Third, by applying existing bonding techniques such as gluing, polymer film bonding, indium solder bonding, or Au eutectic bonding, a strong coupling can be formed between capillaries


12


and the micro fluidic system


14


. Therefore, this coupling process can provide robust, high-yield fluidic interconnection with minimal preparation time and complexity.




The micromachined fluidic couplers


10


can be made from different materials (i.e. silicon, metal, and even polymers) that are employed in microfabrication processes By using a batch micromachining process, a large quantity of couplers


10


can be fabricated in a single manufacturing run. Truncated couplers


10


of

FIGS. 6



a


,


6




b


and


6




c


are designed for the inlet/outlet pits


26


formed by silicon anisotropic wet etching. Post couplers


10


of

FIG. 7

are designed for the inlet/outlet pits


26


with any other shapes such as circular pits, rectangular pits, or even triangular pits. Alignment post


36


is manufactured to have a conforming shape to that of the circular pits, rectangular pits, or even triangular pit.




Consider now the method of manufacture of a silicon truncated pyramidal coupler


10


as shown in

FIGS. 6



c


and


6




c


′. A similar manufacturing process can be used to fabricate the other described embodiments. Silicon truncated pyramidal coupler


10


is fabricated by standard silicon anisotropic wet etching and deep reactive ion etching (DRIE). The process flow is shown in

FIGS. 8



a


,


8




b


,


8




c


and


8




d


. Starting with a <100> silicon prime wafer


22


, a patterned layer of mask material


28


is grown for the following silicon anisotropic wet etch and DRIE. By using a silicon anisotropic wet etch a pyramidal island


42


with a small pit


44


in the center is created on the front side of the wafer


22


. By DRE on the backside


48


of the wafer


22


, a circular pit


20


is etched all the way through to meet the pit


44


on the front side to define hole


32


and stopper


30


. Masking layer


28


is removed. A layer of bonding material is coated before or after the DRE step of

FIG. 8



c


. A capillary tube


12


, coated with a thin layer of bonding material, is placed in the size-matched hole


20


and bonded to the coupler


10


.




By using the truncated pyramidal silicon couplers


10


, robust, high-yield fluidic interconnection can be easily established. The coupling can be self-aligned by fitting the truncated pyramidal couplers into the shape-matched inlet/outlet pits


26


created by anisotropic etching as shown in FIG.


9


. With a thin layer


50


of bonding material coated on the surfaces, existing bonding techniques (such as gluing, indium solder bonding, or Si—Au eutectic bonding) can be used to bond the couplers


10


to a fluidic system


14


. Strong coupling can be achieved, which allows for high pressures. In addition, the self-aligning feature leads to a high-yield coupling.




The truncated pyramidal coupler


10


can also be molded with other materials such plastic, indium solder, and electroplated metals. First, the mold is fabricated on a silicon wafer


52


by an anisotropic wet etch . Then the body


54


truncated pyramidal-shape coupler


10


is molded or electroplated in the silicon mold


52


. Later, the center pit


20


is made by electrode discharge machining (EDM), laser drilling or mechanical drilling. After releasing from the silicon mold


52


, a layer


56


of bonding material is coated on the surface of the coupler


10


. Finally, a capillary tube


12


, coated with a thin layer of glue, is placed in the size-matched hole


20


to bond to the coupler


10


.




Post couplers


10


of

FIG. 7

are designed for a microfluidic system


14


with small straight inlets and outlets shown in FIG.


11


. By inserting the alignment post


36


into an inlet


16


or outlet


18


of matching size, the coupler


10


and tubing


12


are automatically aligned to the inlet/outlet


16


/


18


. With the strong bond formed by the bonding material and large bonding surface, the coupling can withstand very high pressures.




Post coupler


10


is fabricated on a silicon wafer


22


by etching three times via DRIE. The process flow is shown in

FIGS. 12



a


, . Starting from a flat wafer


22


in

FIG. 12



a


, a 200 to 300 μm deep pit


60


is etched on the front side


58


, and then an 50 to 100 μm high alignment post


36


is masked and formed on the front side by etching down the unmasked area


62


as shown in

FIG. 12



b


. The post


36


is designed such that its size closely matches that of the inlets/outlets


16


/


18


. On the backside


64


, a pit


66


is etched down all the way to meet pit


60


through front side


58


as shown in

FIG. 12



c


. The size of the pit


66


on the backside


64


is chosen to closely match the size of the tubing


12


. After coating with a bonding layer, a tube


12


is inserted into the pit


66


through the backside


64


and then bonded to the coupler


10


as shown in

FIG. 12



d.






Many alterations and modifications may be made by those having ordinary skill in the art without departing from the spirit and scope of the invention. Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not be taken as limiting the invention as defined by the following claims. For example, notwithstanding the fact that the elements of a claim are set forth below in a certain combination, it must be expressly understood that the invention includes other combinations of fewer, more or different elements, which are disclosed in above even when not initially claimed in such combinations.




The words used in this specification to describe the invention and its various embodiments are to be understood not only in the sense of their commonly defined meanings, but to include by special definition in this specification structure, material or acts beyond the scope of the commonly defined meanings. Thus if an element can be understood in the context of this specification as including more than one meaning, then its use in a claim must be understood as being generic to all possible meanings supported by the specification and by the word itself.




The definitions of the words or elements of the following claims are, therefore, defined in this specification to include not only the combination of elements which are literally set forth, but all equivalent structure, material or acts for performing substantially the same function in substantially the same way to obtain substantially the same result. In this sense it is therefore contemplated that an equivalent substitution of two or more elements may be made for any one of the elements in the claims below or that a single element may be substituted for two or more elements in a claim.




Insubstantial changes from the claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalently within the scope of the claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements.




The claims are thus to be understood to include what is specifically illustrated and described above, what is conceptionally equivalent, what can be obviously substituted and also what essentially incorporates the essential idea of the invention.



Claims
  • 1. A micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size comprising:a substrate; a cavity defined in said substrate defining said orifice; a body having a shape conforming said shape of said cavity; and a through hole defined through said body having a size conforming to said first size of said capillary, said capillary being disposable into said through hole so that said capillary of said first size is coupled to said orifice of said second size without said first and second sizes being the same.
  • 2. The micromachined coupler of claim 1 wherein said cavity and said body have conforming slanting surfaces.
  • 3. The micromachined coupler of claim 1 wherein said cavity and said body define truncated pyramidal shapes.
  • 4. The micromachined coupler of claim 3 wherein said cavity and said body define truncated square pyramidal shapes.
  • 5. The micromachined coupler of claim 3 wherein said cavity and said body define truncated triangular pyramidal shapes.
  • 6. The micromachined coupler of claim 1 wherein said cavity and said body define truncated conical shapes.
  • 7. The micromachined coupler of claim 1 further comprising a tubing stopper defined in said through hole.
  • 8. The micromachined coupler of claim 1 wherein said size of said orifice is different than said size of said capillary.
  • 9. A method of fabricating a micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size comprising:masking a substrate from which a body of said micromachined coupler will be formed said masking forming a pattern to define a pyramidal structure in said substrate; anisotropically etching said masked substrate to form said pyramidal structure including a pit in said pyramidal structure; masking a surface of substrate opposing said pyramidal structure; and defining a prismatic hole through said substrate and communicating with said pit to provide a through hole through said substrate. where anisotropically etching said masked substrate to form said pyramidal structure forms a simple truncated structure.
  • 10. A method of fabricating a micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size comprising:masking a substrate from which a body of said micromachined coupler will be formed, said masking forming a pattern to define a pyramidal structure in said substrate; anisotropically etching said masked substrate to form said pyramidal structure including a pit in said pyramidal structure; masking a surface of substrate opposing said pyramidal structure; defining a prismatic hole through said substrate and communicating with said pit to provide a through hole through said substrate; and disposing a capillary into said prismatic hole in a sealed relationship therewith.
  • 11. A method of fabricating a micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size comprising:masking a substrate from which a body of said micromachined coupler will be formed, said masking forming a pattern to define a pyramidal structure in said substrate; anisotropically etching said masked substrate to form said pyramidal structure including a pit in said pyramidal structure; masking a surface of substrate opposing said pyramidal structure; and defining a prismatic hole through said substrate and communicating with said pit to provide a through hole through said substrate, where anisotropically etching said masked substrate to form said pyramidal structure forms a square truncated structure.
  • 12. A method of fabricating a micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size comprising:masking a substrate from which a body of said micromachined coupler will be formed, said masking forming a pattern to define a pyramidal structure in said substrate; anisotropically etching said masked substrate to form said pyramidal structure including a pit in said pyramidal structure; masking a surface of substrate opposing said pyramidal structure; and defining a prismatic hole through said substrate and communicating with said pit to provide a through hole through said substrate, where anisotropically etching said masked substrate to form said pyramidal structure forms a triangular truncated structure.
  • 13. A method of fabricating a micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size comprising:masking a substrate from which a body of said micromachined coupler will be formed, said masking forming a pattern to define a pyramidal structure in said substrate; anisotropically etching said masked substrate to form said pyramidal structure including a pit in said pyramidal structure; masking a surface of substrate opposing said pyramidal structure; and defining a prismatic hole through said substrate and communicating with said pit to provide a through hole through said substrate, where anisotropically etching said masked substrate to form said pyramidal structure forms a conical truncated structure.
  • 14. A micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size comprising:a substrate; a cavity defined in said substrate defining said orifice; a micromachined body having a shape conforming said shape of said cavity; and a micromachined through hole defined through said body having a size conforming to said first size of said capillary, said capillary being disposed into said through hole so that said capillary of said first size is coupled to said orifice of said second size wherein said first and second sizes are not the same.
RELATED APPLICATIONS

The present application is a Divisional of Ser. No. 09/516,487 filed on Mar. 1, 2000 now U.S. Pat. No. 6,428,053 and related to U.S. Provisional Patent Application Ser. No. 60/124,244 filed on Mar. 12, 1999.

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5667255 Kato Sep 1997 A
5890745 Kovacs Apr 1999 A
6056331 Benett et al. May 2000 A
6186556 Masuyama et al. Feb 2001 B1
6240790 Swedberg et al. Jun 2001 B1
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6428053 Tai et al. Aug 2002 B1
Provisional Applications (1)
Number Date Country
60/124244 Mar 1999 US