U.S. patent application number 10/020693 was filed with the patent office on 2002-05-09 for chemico-mechanical microvalve and devices comprising the same.
Invention is credited to Robotti, Karla M., Swedberg, Sally A., Yin, Hongfeng.
Application Number | 20020054835 10/020693 |
Document ID | / |
Family ID | 26783553 |
Filed Date | 2002-05-09 |
United States Patent
Application |
20020054835 |
Kind Code |
A1 |
Robotti, Karla M. ; et
al. |
May 9, 2002 |
Chemico-mechanical microvalve and devices comprising the same
Abstract
Micro-fluid devices and methods for their use are provided. The
subject devices are characterized by the presence of at least one
micro-valve comprising a phase reversible material, e.g. a
reversible gel, that reversibly changes its physical state in
response to an applied stimulus, e.g. a thermoreversible gel. In
using the subject device, fluid flow along a flow path of the
device is modulated by applying an appropriate stimulus, e.g.
changing the temperature, to the microvalve. The subject devices
find use in a variety of applications, including micro-analytical
applications.
Inventors: |
Robotti, Karla M.; (Mt.
View, CA) ; Swedberg, Sally A.; (Palo Alto, CA)
; Yin, Hongfeng; (San Jose, CA) |
Correspondence
Address: |
AGILENT TECHNOLOGIES, INC.
Legal Department, DL429
Intellectual Property Administration
P.O. Box 7599
Loveland
CO
80537-0599
US
|
Family ID: |
26783553 |
Appl. No.: |
10/020693 |
Filed: |
December 14, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10020693 |
Dec 14, 2001 |
|
|
|
09294867 |
Apr 20, 1999 |
|
|
|
60091093 |
Jun 29, 1998 |
|
|
|
Current U.S.
Class: |
422/400 ;
436/180 |
Current CPC
Class: |
B01J 2219/00891
20130101; Y10T 137/2082 20150401; B01L 2400/0677 20130101; F16K
99/0036 20130101; B01J 19/0093 20130101; Y10T 436/2575 20150115;
F16K 2099/0074 20130101; F16K 2099/0076 20130101; F16K 2099/0084
20130101; F16K 99/0044 20130101; B01L 2300/087 20130101; B01J
2219/00907 20130101; B01J 2219/00909 20130101; B81B 3/0035
20130101; B01L 3/502738 20130101; F16K 99/0001 20130101; F16K
99/0017 20130101; F16K 99/0025 20130101; B01L 2300/0816 20130101;
F16K 2099/0078 20130101 |
Class at
Publication: |
422/103 ;
422/100; 422/102; 436/180 |
International
Class: |
G01N 001/00 |
Claims
What is claimed is:
1. A micro-fluidic device having a fluid flow path and at least one
micro-valve comprising a phase reversible material.
2. The micro-fluidic device according to claim 1, wherein said
device comprises two intersecting flow paths, wherein one of said
flow paths is substantially filled with said phase reversible
material and said micro-valve is positioned at the intersection of
said intersecting flow paths.
3. The micro-fluidic device according to claim 1, wherein said
micro-valve comprises said phase reversible material stably
associated with a high surface area component.
4. The micro-fluidic device according to claim 3, wherein said high
surface area component is stably associated with at least one wall
of said fluid flow path.
5. The micro-fluidic device according to claim 3, wherein said high
surface area component is maintained in said flow path by a
retaining means.
6. The micro-fluidic device according to claim 1, wherein said
phase reversible material is a phase reversible polymer.
7. The micro-fluidic device according to claim 1, wherein said
micro-valve modulates the rate of the fluid flow along said flow
path.
8. The micro-fluidic device according to claim 1, wherein said
phase reversible material is thermo-reversible.
9. A micro-fluidic device comprising a micro-valve and two
intersecting flow paths, wherein one of said intersecting flow
paths is substantially filled with a phase reversible material and
said micro-valve is positioned at the intersection of said
intersecting flow paths.
10. The micro-fluidic device according to claim 9, wherein said
micro-fluidic device comprises at least one micro-compartment.
11. The micro-fluidic device according to claim 10, wherein said
micro-compartment is a micro-channel.
12. The micro-fluidic device according to claim 9, wherein said
phase reversible material is a phase reversible polymer.
13. The micro-fluidic device according to claim 12, wherein said
phase reversible polymer is an N-isopropylacrylamide copolymer.
14. The micro-fluidic device according to claim 12, wherein said
phase reversible polymer is a polyalkylene oxide.
15. The micro-fluidic device according to claim 9, wherein said
micro-valve modulates the rate of the fluid flow along said flow
path.
16. The micro-fluidic device according to claim 9, wherein said
phase reversible material is thermo-reversible.
17. A micro-fluidic device comprising a fluid flow path and at
least one micro-valve, wherein said micro-valve comprises a phase
reversible material stably associated with a high surface area
component, and wherein said high surface area component is stably
associated with at least one surface of said flow path.
18. The micro-fluidic device according to claim 17, wherein said
high surface area component comprises an array of posts bonded to
said at least one surface of said flow path.
19. The micro-fluidic device according to claim 17, wherein said
micro-fluidic device comprises at least one micro-compartment.
20. The micro-fluidic device according to claim 19, wherein said
micro-compartment is a micro-channel.
21. The micro-fluidic device according to claim 17, wherein said
phase reversible material is a phase reversible polymer.
22. The micro-fluidic device according to claim 21, wherein said
phase reversible polymer is an N-isopropylacrylamide copolymer.
23. The micro-fluidic device according to claim 21, wherein said
phase reversible polymer is a polyalkylene oxide.
24. The micro-fluidic device according to claim 17, wherein said
micro-valve modulates the rate of the fluid flow along said flow
path.
25. The micro-fluidic device according to claim 17, wherein said
phase reversible material is thermo-reversible.
26. A micro-fluidic device comprising a fluid flow path and at
least one micro-valve, wherein said micro-valve comprises a phase
reversible material stably associated with a high surface area
component maintained in said flow path by a retaining means.
27. The micro-fluidic device according to claim 26, wherein said
retaining means comprises fluid permeable barriers positioned in
said flow path on opposite sides of said high surface area
component.
28. The micro-fluidic device according to claim 26, wherein said
retaining means comprises constrictions in said flow path present
on either side of said high surface area component.
29. The micro-fluidic device according to claim 26, wherein said
high surface area component is selected from the group consisting
of: a plurality of solid phase particles; a membrane; and a mesh
structure.
30. The micro-fluidic device according to claim 26, wherein said
micro-fluidic device comprises at least one micro-compartment.
31. The micro-fluidic device according to claim 30, wherein said
micro-compartment is a micro-channel.
32. The micro-fluidic device according to claim 26, wherein said
phase reversible material is a phase reversible polymer.
33. The micro-fluidic device according to claim 32, wherein said
phase reversible polymer is an N-isopropylacrylamide copolymer.
34. The micro-fluidic device according to claim 32, wherein said
phase reversible polymer is a polyalkylene oxide.
35. The micro-fluidic device according to claim 26, wherein said
micro-valve modulates the rate of the fluid flow along said flow
path.
36. The micro-fluidic device according to claim 26, wherein said
phase reversible material is thermo-reversible.
37. A method of modulating fluid flow along a flow path of a
micro-fluidic device, said method comprising: modulating the
physical state of a micro-valve positioned in said flow path,
wherein said micro-valve comprises a phase reversible material.
38. The method according to claim 37, wherein said phase reversible
material is a phase reversible polymer.
39. The method according to claim 38, wherein said phase reversible
polymer is a thermoreversible polymer.
40. The method according to claim 37, wherein said modulating
comprises changing the temperature of said thermoreversible
polymer.
41. The method according to claim 37, wherein said modulating
occurs by actuation of a phase reversing means.
42. The method according to claim 41, wherein said phase reversing
means is completely external to said device.
43. The method according to claim 41, wherein at least one
component of said phase reversing means is internal to said
device.
44. A kit for use in a fluid flow process, said kit comprising: a
micro-fluidic device according to claim 1.
45. The kit according to claim 44, wherein said kit further
comprises a phase reversing means.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Pursuant to 35 U.S.C. .sctn. 119 (e), this application
claims priority to the filing date of the U.S. Provisional Patent
Application Serial No. 60/091,093 filed Jun. 29, 1998, the
disclosure of which is herein incorporated by reference.
INTRODUCTION
[0002] 1. Technical Field
[0003] The field of this invention is micro-fluidic devices.
[0004] 2. Background of the Invention
[0005] Many important chemical processes are carried out in fluid
environments, where such processes include chemical syntheses,
fluid sample analyses, fluid component separations, and the like.
In many situations, it is desirable to work with small volumes of
fluid, e.g. from femtoliter to .mu.l quantities of fluid. Such
situations include sample analysis in which small volumes of
initial sample are analyzed; chemical synthesis, in which small
quantities of chemical are desired and/or expensive reagents are
employed, and the like. As such, there has been much interest in
the development of micro-fluidic devices in which fluid is
manipulated through one or more micro-channels present in the
device.
[0006] A variety of different micro-fluidic devices have been
developed in recent years. Such devices hold the promise of
providing significant advantages over conventional macro-scale
fluid manipulation devices. Such advantages include: ease of use,
such that minimally trained technicians can operate the device;
portability, such that fluid analyses can be conducted in the field
as opposed to in the lab; reduced sample size requirements;
reduction in solvent waste generation; and the like.
[0007] Despite the potential advantages provided by such devices,
there are still significant technical obstacles that must be
overcome if such devices are ever to realize their full potential.
One such obstacle is the control of fluid flow, particularly
between various regions or compartments in the device, i.e. control
of fluid flow at the micro/micro interface level.
[0008] A number of purely mechanical approaches have been proposed
in order to control the micro/micro interface in such devices.
Purely mechanical means, e.g. valves, that have been proposed to
control fluid flow in micro-fluidic devices include: flexible
membranes, needle valves and the like. However, there are
significant drawbacks associated with each of these proposals,
which drawbacks include: inability to control the valve, lack of
sufficiently strong materials, lack of ability to sufficiently seal
the valve, etc.
[0009] As such, there is continued interest in the identification
of a valve means for controlling fluid flow within a micro-fluidic
device.
[0010] Relevant Literature
[0011] Micro-fluidic devices are described in U.S. Pat. Nos.:
5,770,029; 5,755,942; 5,746,901; 5,681,751; 5,658,413; 5,653,939;
5,653,859; 5,645,702; 5,605,662; 5,571,410; 5,543,838; 5,480,614,
the disclosures of which are herein incorporated by reference.
[0012] Reversible gel compositions are described in U.S. Pat. Nos.:
5,720,717; 5,672,656; 5,631,337; 5,569,364; 5,670,480; 5,658,981;
5,470,445; 5,432,245; 5,298,260; 5,162,582; 4,439,966, the
disclosures of which are herein incorporated by reference.
SUMMARY OF THE INVENTION
[0013] Micro-fluidic devices and methods for their use are
provided. The subject devices are characterized by having at least
one micro-valve that modulates fluid flow through the device. The
micro-valve comprises a phase reversible material, e.g. gel, that
is capable of reversibly changing its physical state in response to
an applied stimulus. In using the subject devices, fluid flow is
controlled by applying the appropriate stimulus to the micro-valve.
The subject devices find use in a variety of different
applications, particularly micro-fluidic analytical
applications.
BRIEF DESCRIPTION OF THE FIGURES
[0014] FIG. 1 provides a representation of a micro-fluidic device
according to the subject invention.
[0015] FIG. 2 provides a representation of a variation of the
device shown in FIG. 1.
[0016] FIG. 3 provides a representation of a micro-valve according
to one embodiment of the subject invention.
[0017] FIG. 4 provides a representation of yet another
micro-fluidic device embodiment of the subject invention.
[0018] FIG. 5 provides a representation of a variation on the
device shown in FIG. 4.
[0019] FIG. 6 provides a graph of the flow profile achieved through
a micro-valve according to the subject invention.
[0020] FIG. 7 provides a graph of the flow profile achieved through
a second micro-valve according to the subject invention.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
[0021] Micro-fluidic devices and methods for their use are
provided. Fluid flow through the micro-fluidic devices is modulated
by at least one micro-valve comprising a phase reversible material,
e.g. gel, that is capable of reversibly changing physical states in
response to an applied stimulus. The subject devices find use in a
variety of applications, particularly in micro-analytical
applications of fluid samples.
[0022] Before the subject invention is described further, it is to
be understood that the invention is not limited to the particular
embodiments of the invention described below, as variations of the
particular embodiments may be made and still fall within the scope
of the appended claims. It is also to be understood that the
terminology employed is for the purpose of describing particular
embodiments, and is not intended to be limiting. Instead, the scope
of the present invention will be established by the appended
claims.
[0023] In this specification and the appended claims, the singular
forms "a," "an," and "the" include plural reference unless the
context clearly dictates otherwise. Unless defined otherwise, all
technical and scientific terms used herein have the same meaning as
commonly understood to one of ordinary skill in the art to which
this invention belongs.
[0024] The subject invention provides a novel chemico-mechanical
means for modulating fluid flow through a micro-fluidic device,
i.e. a chemico-mechanical micro-valve. The micro-valves of the
subject invention find use in a variety of different micro-fluidic
devices. As used herein, the term "micro-fluidic" device refers to
any device in which micro-volumes of fluid are manipulated along a
fluid flow path during any given use or operation, e.g. sample
preparation, sample separation, chemical synthesis, etc., where
"micro-volume" means from about 10 femtoliters to 500 .mu.l,
usually from about 100 femtoliters to about 200 .mu.l. The
micro-fluidic devices contain at least one fluid flow path through
which fluid flows through the device, where a plurality of flow
paths that may or may not be intersecting and may be positioned in
any convenient configuration may be present in the device, as
described in greater detail infra. Generally, the micro-fluidic
devices in which the subject valves find use will have at least one
micro-compartment positioned at some point in the fluid flow path,
where the term "micro-compartment" means any type of structure in
which micro-volumes of fluid may be contained, and includes
micro-chambers, micro-channels, micro-conduits and the like.
Depending on the nature of the micro-compartment, the
micro-compartment may be the entire fluid flow path through the
device, e.g. where the fluid flow path is a micro-channel, as
described infra, or occupy only a portion of the fluid flow path of
the device. The term micro-chamber, as used herein, means any
structure or compartment having a volume ranging from about 1 .mu.l
to 500 .mu.l, having cross-sectional areas ranging from about 0.05
cm.sup.2 with a chamber depth of 200 .mu.m to 5 cm.sup.2 with a
chamber depth of 1 mm; usually from about 10 .mu.l to 500 .mu.l,
having a cross-sectional area ranging from about 0.5 cm.sup.2 with
a chamber depth of 200 .mu.m to about 5 cm.sup.2 with a chamber
depth of 1 mm; and more usually from about 20 .mu.l to 200 .mu.l
having a cross-sectional area ranging from about 1 cm.sup.2 with a
chamber depth of 200 .mu.m to about 4 cm.sup.2 with a chamber depth
of 500 .mu.m. The micro-compartment structure may have any
convenient configuration, including square, circular, rectangular,
octagonal, irregular etc. Micro-channels or micro-conduits are
micro-compartments that are dimensioned such that fluid is capable
of flowing through the micro-channel by capillary flow, i.e. the
micro-channel is of capillary dimensions. By capillary dimensions
is meant a structure or container in which any cross-sectional
dimension from one side to another, e.g. diameter, widest point
between two walls of a channel, etc., does not exceed about 250
.mu.m. Generally, any cross-sectional dimension of the
micro-channel will range from about 10 to 250 .mu.m, usually from
about 50 to 200 .mu.m.
[0025] The micro-channel(s) of the device may have a linear
configuration, a curved configuration, or any other configuration,
e.g. spiral, angular, etc., depending on the intended use of the
device. In addition, there may be more than one micro-channel in
the device, where the micro-channels may: (a) intersect at various
points to form complicated flow paths or patterns through the
device, e.g. Y-shaped intersections, T-shaped intersections,
crosses; and (b) be separated by one or more micro-chambers, etc,
depending on the intended use of the device.
[0026] In many embodiments, the micro-channel(s) of the device, as
well as any other components, e.g. entry ports, etc., will be
present in an essentially planar-shaped substrate, e.g. a
card-shaped substrate, disk-shaped substrate, etc. The substrate
may be fabricated from a variety of different materials, including
polymeric substrates, such as polyimides, polycarbonates,
polyesters, polyamides, polyethers, polyolefins, and mixtures
thereof, as well as silicon or silicon dioxide based materials,
such as quartz, fused silica, glass (borosilicates) etc, ceramics
and composites thereof.
[0027] A variety of different micro-fluidic devices have been
developed in which the subject micro-valve may find use, where such
devices include those described in U.S. Pat. Nos. 5,770,029;
5,755,942; 5,746,901; 5,681,751; 5,662,787; 5.661,028; 5,658,413;
5,653,939; 5,653,859; 5,645,702; 5,632,876; 5,605,662; 5.599,432;
5,585,069; 5.571,410; 5,543,838; 5,540,826; 5,480,614; 5,458,761
the disclosures of which are herein incorporated by reference. Of
particular interest in many embodiments are the .mu.-TAS devices
described in U.S. Pat. Nos. 5,658,413: 5,571,410 and 5,500,071, the
disclosures of which are herein incorporated by reference.
[0028] The micro-fluidic devices of the subject invention are
characterized by having at least one micro-valve that modulates the
flow of fluid along at least one fluid flow path in the device. As
the micro-valve modulates the flow fluid through one or more of the
fluid flow paths in the device (if the device comprises more than
one fluid flow path), the micro-valve also modulates fluid flow
through micro-compartments present in the device. By "modulates" is
meant that the micro-valve is capable of at least restricting or
enhancing fluid flow along the flow path, where the micro-valve may
be: (a) a proportional micro-valve, in that it can restrict fluid
flow in response to an appropriate stimulus but not completely
inhibit fluid flow; or (b) an on/off micro-valve, in that it can
completely inhibit fluid flow (i.e. close) in response to an
appropriate stimulus.
[0029] The micro-valve of the subject devices is characterized by
comprising a phase reversible material which modulates fluid flow
along a flow path in the device. By phase reversible material is
meant a material that changes its physical state, e.g. going from a
soluble state to a solid state, in response to an applied stimulus.
The phase reversible material is a material that is capable of
going from a first stage that is substantially permeable to fluid,
i.e. allows free flow of fluid, to a second stage that is
substantially impermeable to fluid, i.e. substantially inhibits
fluid flow. Any phase reversible material may be employed, so long
as the material changes in phase in response to an applied stimulus
in a manner sufficient to modulate its fluid permeability, i.e. the
ability of fluid to flow through the material.
[0030] As such, the phase reversible material is a material that
responds to an applied stimulus with a phase change. The material
may be responsive to a number of distinct stimuli, where stimuli of
interest include: temperature, pH, electrical current, light,
magnetic field, etc. Specific materials of interest are
polymers.
[0031] In many embodiments, the phase reversible material is a
reversible gel, where by reversible gel is meant a gel composition
that is capable of changing its physical state, e.g. from soluble
to semi-solid gel state, in response to a particular stimulus, e.g.
termpertature, pH, chemical agent, electrical current, light, etc.
Such gel compositions known in the art as "smart" gels
"intelligent" gels, hydrogels, etc. The subject micro-valves of
this embodiment in which the phase reversible material is a gel
composition may comprise any suitable phase reversible gel, as long
as the gel is capable of changing its physical state in response to
an applied stimulus.
[0032] Of particular interest in many embodiments of the subject
invention are reversible gels that change their physical state,
e.g. change their fluid permeability by going from a first state to
a second state, such as soluble to semi-solid, in response to a
change in temperature, i.e. thermoreversible or temperature
sensitive gels. The thermoreversible or temperature sensitive gels
that find use in the microvalves of the subject invention are those
gels that are capable of changing their physical state, e.g. gels
that go from a soluble state to a semi-solid state, over a narrow
temperature range, e.g. the lower critical solution temperature
(LCST). In the thermoreversible gels finding use as a phase
reversible material in the micro-valves of the subject invention,
both gels which go from a solid to a soluble form as well as gels
that go from a soluble to a solid form as the temperature increases
find use, where in many embodiments, those thermnoreversible gels
which go from a soluble form to a solid form as the temperature
increases of are particular interest.
[0033] A variety of thermoreversible or temperature sensitive gels
have been identified and are suitable for use in the micro-valves
of the subject invention. Thermoreversible polymeric gels of
interest include those comprising polymers such as: partially
saponified polyvinyl acetates, polyvinyl methyl ether, methyl
cellulose, polyalkylene oxides, polyvinyl methyloxazolidinone, and
polymacrylamides, and the like, where polyacrylamides and
polyalkylene oxide based polymers are of particular interest.
[0034] Specific polyacrylamides of interest include:
poly-N-ethylacrylamide; poly-N-n-propyl(meth)acrylamides;
poly-N-isopropyl(meth)acrylamides;
poly-N-cyclopropyl(meth)acrylamides; poly-N,N-diethylacrylamide;
poly-N-methyl-N-ethylacrylamide;
poly-N-methyl-N-n-propylacrylamide;
poly-N-methyl-N-isopropylacrylamide; poly-N-acryloylpiperidine;
poly-N-acryloylpyrrolidine;
poly-N-tetrahydrofurfuryl(meth)acrylamide;
poly-N-methoxypropyl(meth)acry- lamide;
poly-N-ethoxypropyl(meth)acrylamide; poly-N-isopropoxypropyl(metho-
)acrylamide; poly-N-ethoxyethyl(meth)acrylamide;
poly-N-(2,2-dimethoxyethy- l )-N-methylacrylamide;
poly-N-1-methyl-2methoxyethyl(meth)acrylamide;
poly-N-1-methoxymethylpropyl(meth)acrylamide;
poly-N-(1,3-dioxolan-2-yl)-- N-methylacrylamide; and
poly-N-8-acryloul-1,4-dioxa-8-azaspiro [4,5]decane,
N-(2methoxyethyl)-N-isopropylacrylamide; and the like. Of
particular interest in this class of the thermoreversible polymeric
compositions are those made up of N-isopropylacrylamide graft
copolymers, where polymers of interest include graft copolymers of
hydrophobic polymers, e.g. butyl methacrylate; and hydrophilic
polymers, e.g. N,N-dimethylacrylamide. See also Takei et al.,
Bioconjugate Chem. (1993) 4:341-346, which discloses polymers of
interest.
[0035] Also of particular interest are gels comprising polyalkylene
oxides, particularly block copolymers of two or more different
polyalkylene oxides, more particularly block copolymers of both
hydrophobic and hydrophilic polyalkylene oxides. In many
embodiments, block copolymers of polyethylene oxide and
polypropylene oxide are preferred, particularly triblock copolymers
thereof. Such copolymers are known in the art and sold under the
tradenames PLURONIC.RTM. and POLOXAMER.RTM.. Specific polyalkylene
triblock copolymers of interest include: F-68, F-88; F-98; F-108,
F-127 and the like, all available from BASF corporation.
[0036] In a first embodiment of the subject invention, the
micro-valve is made solely of the phase reversible material. In
this embodiment, the phase reversible material may be positioned at
one or more distinct locations along the fluid flow path, or along
substantially the entire fluid flow path. Where the
phase-reversible material occupies substantially the entire fluid
flow path, during use its phase is generally switched from a fluid
permeable to a fluid impermeable state at one or more distinct
locations along the fluid flow path, but not along the entire fluid
flow path.
[0037] In a preferred structure of the this first embodiment, the
micro-fluidic device contains at least two intersecting flow paths,
one of which is substantially filled by the phase reversible
material. In other words, the device includes at least a main flow
path and at least one intersecting second flow path, where
substantially all of the secondary flow path is occupied by the
phase reversible material. By "substantially all" is meant that at
least 40%, usually at least 50% and more usually at least 60% of
the entire of the fluid flow path of the device is occupied by the
phase reversible materia. In certain embodiments as much as 70%,
sometimes as much as 80% of the volume of the fluid flow path is
occupied by the phase reversible material. In certain embodiments,
up to 100% of the fluid flow path of the device is occupied by the
phase reversible material.
[0038] The micro-valve that modulates fluid flow along the main
flow path is positioned in the intersection of the main flow path
and second flow path. The intersection of these flow paths may be
minimal, as is found where the main and secondary flows are
intersecting straight lines, e.g. as in a cross-shaped intersection
(See e.g. FIG. 4), or elongated, as is found in those devices where
at least a portion of the secondary flow path is congruent with the
main flow path, e.g. where the two halves of the second flow path
are not positioned on immediately opposite sides of the main flow
path but intersect the main flow path at some distance from each
other. See e.g. FIG. 5. In this preferred embodiment, the
micro-valve may be the entire length of the intersection of the two
flow paths or just a portion thereof.
[0039] In these embodiments where the micro-valve consists
essentially of the phase reversible material, the phase reversible
material will be stably associated with the region of the device in
which fluid flow modulation is desired. Stable association may be
achieved in a number of ways, including bonding, and the like. In
many embodiments, the phase reversible material may be bonded
directly to the region of interest of the micro-fluidic device,
where the nature of the bond may be covalent or non-covalent. For
example, where the phase reversible material is a polymeric gel,
the polymeric constituents of the phase reversible material may be
bonded directly to the micro-compartment wall of the device in the
region in which valve fluid control is desired, where the nature of
the bond may be covalent or non-covalent, but will usually be
covalent. The length of the micro-compartment occupied by the
micro-valve in this second embodiment, i.e. the length of the
micro-compartment to which the phase reversible material is stably
associated, e.g. to which the polymeric components of the gel have
been bound and in which the physical state of the gel is
controllable, will vary depending upon the desired characteristics
of the micro-valve, i.e. strength, rate of fluid flow modulation,
etc., but will generally be at least about 50 .mu.m, usually at
least about 100 .mu.m and more usually at least about 500 .mu.m
long, and may be as long as 1 cm or longer, but will generally not
exceed about 10 cm, and usually will not exceed about 5 cm. In the
region of the micro-compartment occupied by the micro-valve, the
phase reversible material will generally be stably associated, e.g.
bonded, to all surfaces of the compartment in a manner that
provides substantially no void, space through which fluid may
freely flow, e.g. the polymeric constituents of a phase reversible
gel will be bonded to all of the surfaces of the micro-compartment,
e.g. the top, bottom, left side and right side of a micro-channel
having a cross-sectional square shape.
[0040] In a second embodiment of the subject invention, the phase
reversible material is present in combination with one or more
additional mechanical elements, such as a high surface area
mechanical means, i.e. the micro-valve is a composite of a phase
reversible material and a mechanical element, e.g. a reversible gel
in combination with one or more high surface area components, e.g.
rods, pins, etc, such as the structures described in U.S. Pat. No.
5,427,663, the disclosure of which is herein incorporated by
reference. This embodiment is further characterized by having the
high surface area stably associated with one or more walls of the
flow path, as described in greater detail infra. The substantial
surface area structures may be fabricated from a variety of
materials, including quartz, fused silica, polymeric materials,
e.g. polyimides, etc. The substantial surface area structures of
this embodiment (and therefore the phase reversible material
associated therewith) are stably associated with the surface of the
micro-compartment in which they are located. Stable association of
the structures in the compartment is achieved in a number of ways,
such as bonding of the structures to the micro-compartment surface.
For example, the micro-valve of the subject invention may comprise
a phase reversible material, (e.g. reversible gel) in combination
with a plurality of polymeric rods covalently attached to one or
more sides of the fluid flow path, e.g. micro-channel, where such a
rod configuration is described in Austin et al., Electrophoresis
(1996) 17:1075-1079. In such embodiments, the phase reversible
material, e.g. the polymeric constituents of the reversible gel,
will be attached to the high surface area component, e.g. rod or
pin, either non-covalently or covalently, but usually
covalently.
[0041] In yet another embodiment of the subject devices, the
micro-valve comprises a phase reversible material in combination
with one more high surface area components, where the phase
reversible material/high surface area composite structure is not
attached to one or more of the walls of the fluid flow path.
Instead, the otherwise mobile or detached composite structure is
retained at one or more locations along the fluid flow path with a
retaining means, e.g. a mechanical restriction means. Examples of
such means include: physical constrictions provided by appropriate
configuration of the walls of the flow path, e.g.
micro-compartment, in the region in which the phase reversible
material is located; stably positioned frits, filters or other
solid permeable structures positioned on either side of the phase
reversible material in the fluid flow path of the device; and the
like. The frits or analogous structural retention means keep the
phase reversible material from shifting location in the flow path
of the device. The mobile or detached high surface area component
of the composite structure in this embodiment may vary widely.
Suitable high surface area components of this embodiment include:
beads or particles, membranes, mesh structures, and the like.
[0042] The micro-valves present in the subject devices are actuated
by an actuation means, e.g. a switch, that is external to the
device, where the actuation means actuates a phase reversing means
that may be entirely external to the device or at least partially
internal to the device. As such, the subject device may or may not
further comprise one or more internal components of a means for
reversing the phase of the phase reversible material in the
micro-valve.
[0043] The phase changing means which influences the state of a
micro-valve in any given device will necessarily depend on the
nature of the phase reversible material in the micro-valve, and
will be a means capable of applying the requisite stimulus to the
material to achieve the desired phase change. Thus, the phase
changing means may be a means capable of applying thermal energy,
light, electrical current, chemical agents, hydrogen ions, etc., to
the phase reversible material. For example, where the micro-valve
comprises a thermosensitive gel, the phase changing means will be a
means for changing the temperature of the gel in a manner
sufficient to change to the phase of the gel from one state to
another, e.g. soluble state to semi-solid or solid state. In other
words, the phase changing means will be a means capable of taking
the gel above and/or below the phase critical temperature or lower
critical solution temperature of the gel. An example of such a
temperature changing means is a resistance heater. Another example
of a suitable temperature changing means is a Peltier device.
[0044] As mentioned above, the phase changing means may be
completely external to the device, i.e. the phase changing means
may be entirely peripheral to the device, or one or more components
of, but generally not all of, the phase changing means may be
internal to the device. For example, where the phase changing means
is an external heating element on which the subject device is
placed during operation, the entire phase changing means is
external or peripheral to the device. Alternatively, where the
phase changing means includes a resistor element integrated into
the device which interacts with external circuitry to provide the
requisite electrical current to the internal resistor, a portion or
component of the phase changing means is internal to the
device.
[0045] The devices of the subject invention may be fabricated using
any convenient methodology. Fabrication of micro-fluidic devices is
known by those of skill in the art and described in a plurality of
patent and journal references, including: U.S. Pat. Nos. 5,770,029;
5,755,942; 5,746,901; 5,681,751; 5,662,787; 5,661,028; 5,658,413;
5,653,939; 5,653,859; 5,645,702; 5,632,876; 5,605,662; 5,599,432;
5,585,069; 5,571,410; 5,543,838; 5,500,071; 5,540,826; 5,480,614;
5,458,761 the disclosures of which are herein incorporated by
reference. Fabrication of micro-fluidic devices necessarily varies
depending on the nature of the device to be fabricated, the
materials from which the device is prepared, etc., but may involve
one or more of micro-machining, fabrication processes, e.g. laser
ablation, photolithography, molding, embossing, and the like.
[0046] The preparation of reversible gels, such as thermoreversible
gels, which are employed in the subject invention is well known to
those of skill in the art and reported in a number of patent and
journal references, including: U.S. Pat. Nos. 5,720,717; 5,672,656;
5,631,337; 5,569,364; 5,670,480; 5,658,981; 5.470,445; 5,432,245;
5,298,260; 5,162,582; 4,439,966; the disclosures of which are
herein incorporated by reference.
[0047] Depending on the nature of the micro-valve, the micro-valve
can be placed in the device by a variety of different
methodologies. For example, where the micro-valve consists
essentially of a reversible gel at the intersection of a secondary
and main flow paths, the gel material can be flowed through the
secondary flow path which intersects the main flow path at the
location in which the micro-valve is desired, where the
intersection of the flow paths becomes filled with the reversible
gel material and therefore becomes the micro-valve. Where the
micro-valve comprises a reversible gel in combination with a high
surface area component, e.g. a plurality of rods or pins, the
polymeric constituents of the gel may be synthesized directly on
the rods or pins, or synthesized separately in solution and then
attached to the rods or pins. The high surface area component may
be positioned in the micro-compartment prior to placement of the
gel, or the composite gel/structure element may be positioned in
the micro-compartment following fabrication. The above are merely
representative of different protocols that may be used to fabricate
the subject devices.
[0048] In certain embodiments of the invention, the micro-valve
will be fabricated such that it is non-reversible, i.e. it
irreversibly opens or closes. Such valves will comprise a material,
such as a gel, that is irreversibly capable of changing its
physical state in response to an applied stimulus.
[0049] The subject devices will now be further described in terms
of the figures. FIG. 1 depicts a micro-fluidic device according to
the subject invention. Microfluidic device 10 comprising a single
micro-compartment in the form of a micro-channel 14, having a fluid
entry port 12, a fluid exit port 11 and a detecting region 16.
Device 10 also has a micro-valve 18 comprising a phase reversible
material, e.g. phase reversible gel. The micro-valve region of the
flow channel of the device is directly over the resister 15 of
heating element 13 (alternatively, the resistor and heating element
could be replaced by a Peltier device or other means for raising
the temperature of the local region of the flow path). The phase
reversible material may be positioned solely in region 18 or in
other areas of the micro-channel, including along substantially the
entire length of the micro-channel, but will only change physical
states, and thus act as a micro-valve, in region 18 that is
directly above heating element 15. As mentioned above, type of
valve consisting solely or primarily of a phase reversible
material, e.g. gel, may be engineered to be a pure on/off valve, in
which the fluid flow through the region of the microvalve can be
completely inhibited by the valve, or a proportional valve, in
which the flow of fluid through the valve can be selectively
restricted as desired, without complete inhibition of fluid flow
through the valve, i.e. a valve that can be manipulated to allow
faster or slower fluid flow, as desired. In either case, the
micro-valve modulates fluid flow along the flow path. For the
proportional valve, the phase reversible material from which the
micro-valve is made will be one to which a stimulus ramp may be
applied, i.e. a stimulus that changes (e.g. increases or decreases)
in magnitude over a give period of time. For example, a
thermoreversible material may be employed that responds to a
thermal ramp in a manner such that the properties of the material
gradually change along the thermal ramp, e.g. the pores in the gel
matrix gradually decrease in size along the thermal ramp.
[0050] FIG. 2 provides a representation of a variation on the
device shown in FIG. 1. In FIG. 2, the device shown in FIG. 1
further comprises micro-chambers 17 positioned along the flow path
and separated by micro-valves 18. On either side of micro-chambers
17 are ports 19. As such, fluid flow into and out of the
micro-chambers may be controlled through the plurality of
micro-valves in the device.
[0051] Instead of having a micro-valve that consists essentially of
the reversible gel, the valve may further comprise one or more
additional mechanical elements of high surface area, as described
above. FIG. 3 shows a representative valve of this embodiment of
the invention. In FIG. 3, an enlarged view of the element 18 of
FIG. 1 is provided. In FIG. 3, micro-channel 16 comprises
micro-valve 18 positioned directly above heating element 15.
Micro-valve 18 comprises a plurality or array of pins 22 arising
from the floor of the micro-channel. The inter-post spacing of the
array may vary between about 0.01 .mu.m and 50 .mu.m, but in many
embodiments the distance between any two given posts in the array
does not exceed about 1.75 .mu.m, and usually does not exceed about
1.5 .mu.m, and more usually does not exceed about 1.25 .mu.m, where
in many embodiments this distance is about 1.0 .mu.m. Directly
attached to the rod or pin surface are the polymeric constituents
24 of the gel matrix of the micro-valve. The polymeric constituents
are able to interact with each other such that under a first
condition (at a first temperature) they are free moving with
respect to each other, e.g. soluble, such that fluid is able to
flow freely through the array, but in a second condition that are
closely associated with each other, such the fluid flows less
freely and/or not at all, through the array. Thus, this embodiment
of the subject invention can be used to produce both on/off and
proportional micro-valves along a given micro-channel, as with the
first embodiment.
[0052] Yet another embodiment of the subject invention is depicted
in FIG. 4. In FIG. 4, device 30 comprise two intersecting
micro-channels, 32 & 34, having entry ports 31 & 33 and
exit ports 35 & 37. Micro-valves 36, 38, 39 and 40 positioned
along the micro-channels are used to control sample introduction
into the flow channels. FIG. 5 provides a representation of a
variation of the device shown in FIG. 4.
[0053] The subject devices can be used in a variety of different
fluid flow processes, (i.e. applications in which fluid flow is
manipulated (fluid flow manipulation applications)) including
sample preparation, separation, and chemical synthesis
applications. Representative applications in which the subject
devices find use are described in U.S. Pat. Nos. 5,770,029;
5,755,942; 5,746,901; 5,681,751; 5,658,413; 5,653,939; 5,653,859;
5,645,702; 5,605,662; 5,571,410; 5,543,838; 5,480,614; the
disclosures of which are herein incorporated by reference. In using
the subject devices, fluid flow through the micro-channel(s) of the
device will be modulated by selectively manipulating the
micro-valve(s) present in the device, e.g. by locally raising the
temperature of the gel in the micro-valve, etc. Typically, the
subject devices will be used in conjunction with one or more
additional devices, such as a detector device, a sample
introduction device, etc., where such devices and their use are
known to those of skill in the art.
[0054] Also provided are kits comprising the subject micro-fluidic
devices. The subject kits comprise at least one micro-fluidic
device according to the subject invention. The kits may further
include a phase reversing means or components thereof, e.g. a
heating means. The kits of the subject invention will also
typically include instructions for using the subject device,
including instructions for operating the micro-valve(s) present in
the device, where these instructions may be present on one or more
of the packaging, labeling or a package insert. In addition, the
kits may comprise one or more additional elements that find use in
the particular application for which the device has been
fabricated, such as: elements used in electrophoretic or
chromatographic applications, such as a separation medium, labels
for use in separation buffer mediums, and other reagents for
practicing electrochromatographic protocols; etc.
[0055] The following examples are offered by way of illustration
and not by way of limitation.
EXPERIMENTAL
[0056] I. Synthesis and Testing of Micro-Valve.
[0057] A1. Synthesis of a Temperature-Sensitive Polymer.
[0058] Isopropylacrylamide (IPAAm, 5.6 g, 50 mmol) in 20 ml of DMF
was combined with 75 .mu.l (0.5 mmol) of butyl methacrylate (BMA)
and 10-20 .mu.l (0.05 mmol) of ethylene glycol dimethacrylate. This
solution was passed through a column of"inhibitor-remover" packing
(Aldrich #31.133-2) then degassed for 15 minutes with a stream of
helium gas. The degassed solution was treated with 2,2'-dimethyl
azobisisobutyrate and heated under argon at 80.degree. C. for 24
hr. Solvent was evaporated, leaving the temperature-sensitive
polymer.
[0059] A2. Synthesis of Gel Micro-Valve on Glass Substrate.
[0060] A glass substrate was silated with 3-aminopropyl silane to
generate free amino groups on the surface of the substrate. This
surface was covered with a solution of 50 mg of sulfo-HSAB
(N-hydroxysulfosuccinimidy- l-4-azido benzoate) dissolved in 5 ml
of phosphate buffer (pH 8.5). The substrate was allowed to sit in
the dark for 3 hr, then rinsed with water and air-dried.
[0061] Approximately 1 g of the temperature-sensitive polymer was
dissolved in 10 ml of water. This solution was placed over the
azido-activated glass substrate and exposed to UV light at 265 nm
for ca. 30 min from a distance of 3-6 cm. The glass substrate was
then rinsed with water and air-dried.
[0062] A3. Synthesis of Gel Micro-Valve on Polyimide Substrate.
[0063] The synthesis of a thermosensitive gel matrix covalently
attached to a polyimide substrate proceeds as follows. The surface
of the polyimide substrate is treated with a strong base, e.g. KOH
or NaOH in the presence of HOAc, in order to open up the imide and
produce free carboxy functionalities. Activated esters are then
produced in conventional ways and can be reacted with amines such
as H.sub.2NCH.sub.2CH.sub.2NH.sub.2 or H.sub.2NCH.sub.2CH.sub.2OH.
The products are then treated with methacryloyl isocyanate to
produce an intermediate that can then be treated with IPAAm and BMA
in the presence of AIBN/DMF to produce a thermosensitive polymer
grafted onto the polyimide support surface.
[0064] Alternatively, a product with a free amino group can be
treated in the dark with N-hydroxysulfosuccinimidyl-4-azido
benzoate in phosphate buffer (pH 8.5) for 3 hrs. The substrate is
rinsed with water and air-dried. An aqueous solution of a
temperature-sensitive polymer is placed over the azido-activated
polyimide substrate and exposed to UV light at 265 nm for ca. 30
minutes. The substrate is then rinsed with water and air-dried.
[0065] A4. Synthesis of Micro-Valve on Nylon Substrate.
[0066] Nylon mesh filters (Spectrum #148130) with 5 .mu.m opening
were treated with a solution of 3.72 g of calcium chloride and 3.72
g of water in 20 ml methanol for 20 min at 50.degree. C. The filter
was then placed into 20 ml of 3.6 M HCl for 40 min at 45.degree. C.
Finally, the substrate was left in water for 20 hr.
[0067] This nylon substrate was covered with a solution of 50 mg of
sulfo-HSAB dissolved in 5 ml of phosphate buffer (pH 8.5). The
substrate was left in the dark at room temperature overnight, then
rinsed with water and air-dried.
[0068] Approximately 1 g of the temperature-sensitive polymer was
dissolved in 10 ml of water. This solution was placed over the
azido-activated nylon substrate and exposed to UV light at 265 nm
for ca. 30 min from a distance of 3-6 cm. The nylon substrate was
then rinsed with water and air-dried.
[0069] B. Flow Profile Through the Micro-Valve.
[0070] Two different polymer-modified nylon substrates (valve #1
and valve #2) were prepared as described in A4. The
polymer-modified nylon substrate or valve was placed into a high
pressure semi-prep filter assembly (Upchurch Scientific #A330)
fitted with 2 capillary lines (in and out). The assembly was fitted
into a drilled hole within an aluminum block. The block was
controlled by a Peltier device and heat sink. The device allowed
warming and cooling of the block and the filter assembly to within
1.degree. C. accuracy. Fluids flowed through the nylon substrate
(valve) and filter assembly via gravity feed. Examples of the type
of fluids tested were: water, typical biological buffers, e.g., 100
mM phosphate or borate, or aqueous solutions containing up to 40%
miscible organics, e.g., methanol or acetonitrile. The flow
(volume/sec) was measured as a function of temperature. FIG. 6
shows the results from Valve #1 while FIG. 7 shows the results from
Valve #2, where the results were obtained using de-ionized water as
the fluid.
[0071] It is evident from the above results and discussion that the
subject micro-valves provide for significant improvements over
previously employed devices for controlling fluid flow through
micro-fluidic devices. The subject micro-valves provide for a
relatively simple and readily producible means for controlling the
flow of fluid through micro-fluidic devices.
[0072] All publications and patent applications cited in this
specification are herein incorporated by reference as if each
individual publication or patent application were specifically and
individually indicated to be incorporated by reference. The
citation of any publication is for its disclosure prior to the
filing date and should not be construed as an admission that the
present invention is not entitled to antedate such publication by
virtue of prior invention.
[0073] Although the foregoing invention has been described in some
detail by way of illustration and example for purposes of clarity
of understanding, it is readily apparent to those of ordinary skill
in the art in light of the teachings of this invention that certain
changes and modifications may be made thereto without departing
from the scope of the appended claims.
* * * * *