U.S. patent application number 11/461163 was filed with the patent office on 2006-11-16 for methods and devices for high throughput fluid delivery.
This patent application is currently assigned to Caliper Life Sciences, Inc.. Invention is credited to Andrea W. Chow, Robert S. Dubrow, Anne R. Kopf-Sill, J. Wallace Parce.
Application Number | 20060258019 11/461163 |
Document ID | / |
Family ID | 22834118 |
Filed Date | 2006-11-16 |
United States Patent
Application |
20060258019 |
Kind Code |
A1 |
Chow; Andrea W. ; et
al. |
November 16, 2006 |
Methods and Devices for High Throughput Fluid Delivery
Abstract
Methods and devices for delivering fluids into microfluidic
device body structures are described. The methods and devices
include the use of fluid manifolds that are integrated or
interchangeable with device body structures. Methods of fabricating
manifolds are also provided.
Inventors: |
Chow; Andrea W.; (Los Altos,
CA) ; Kopf-Sill; Anne R.; (Portola Valley, CA)
; Parce; J. Wallace; (Palo Alto, CA) ; Dubrow;
Robert S.; (San Carlos, CA) |
Correspondence
Address: |
CALIPER LIFE SCIENCES, INC.
605 FAIRCHILD DRIVE
MOUNTAIN VIEW
CA
94043-2234
US
|
Assignee: |
Caliper Life Sciences, Inc.
Mountain View
CA
94043
|
Family ID: |
22834118 |
Appl. No.: |
11/461163 |
Filed: |
July 31, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09922224 |
Aug 2, 2001 |
|
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11461163 |
Jul 31, 2006 |
|
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60222884 |
Aug 3, 2000 |
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Current U.S.
Class: |
436/180 |
Current CPC
Class: |
Y10T 137/2496 20150401;
B01L 2300/0861 20130101; Y10T 436/11 20150115; B01L 2400/043
20130101; B01L 3/502723 20130101; B01L 3/50273 20130101; B01L
2200/027 20130101; B01L 3/502707 20130101; B01D 61/18 20130101;
B01L 3/502715 20130101; B01L 2400/0406 20130101; Y10T 436/2575
20150115; B01L 2400/0457 20130101; Y10T 137/2516 20150401; Y10T
137/2499 20150401; B01L 2300/0867 20130101; B01L 3/5025 20130101;
B01L 2400/0415 20130101; Y10T 137/2514 20150401; Y10T 137/2501
20150401 |
Class at
Publication: |
436/180 |
International
Class: |
B01L 3/00 20060101
B01L003/00 |
Claims
1. A method of distributing at least one fluid to one or more of a
plurality of ports disposed in a body structure of a microfluidic
device, the method comprising: loading the at least one fluid into
at least a first aperture in a manifold of the microfluidic device,
which microfluidic device comprises the manifold and the body
structure, wherein the manifold further comprises at least one
manifold channel network disposed therein, wherein the first
aperture is in fluid communication with one or more manifold
channels in the at least one manifold channel network, wherein the
first aperture or at least one manifold channel is in fluid
communication with the one or more of the plurality of ports, and
wherein at least one microchannel network is in fluid communication
with the plurality of ports; and, flowing the at least one fluid
using at least one fluid direction component from the first
aperture through the at least one manifold channel network such
that the at least one fluid is distributed to the one or more of
the plurality of ports disposed in the body structure of the
microfluidic device.
2. The method of claim 1, further comprising flowing the at least
one fluid in the at least one microchannel network or the manifold
channel network using one or more fluid direction component
comprising one or more of: a fluid pressure force modulator, an
electrokinetic force modulator, a capillary force modulator, a
gravity force modulator, a magnetic force modulator, a
dielectrophoretic force modulator, or a fluid wicking element.
3. The method of claim 1, further comprising flowing the at least
one fluid in the manifold channel network using a first gravity
force modulator and in the at least one microchannel network using
one or more of: a fluid pressure force modulator, an electrokinetic
force modulator, a capillary force modulator, a second gravity
force modulator, a magnetic force modulator, a dielectrophoretic
force modulator, or a fluid wicking element.
4. The method of claim 1, further comprising providing at least a
second aperture or manifold channel in the manifold, wherein the
second aperture or manifold channel is in fluid communication with
the first aperture, with the at least one or another manifold
channel network, or with the one or more of the plurality of ports,
for venting air from the microfluidic device during the loading or
the flowing steps.
5. The method of claim 1, further comprising providing at least a
second aperture or manifold channel in the manifold, wherein the
second aperture or manifold channel is in fluid communication with
the one or more of the plurality of ports, wherein the second
aperture or manifold channel comprise at least one bulk viscosity
enhancer and at least one electrolyte disposed therein for
delivering at least one electrical field to the one or more of the
plurality of ports during operation of the device.
6. The method of claim 1, further comprising interchanging two or
more body structures such that each body structure is sequentially
mated to the manifold and flowing the at least one fluid from the
manifold to the plurality of ports disposed in each interchanged
body structure.
7. The method of claim 6, wherein at least one step is
automated.
8. The method of claim 1, wherein at least one portion of the at
least one microchannel network comprises a plurality of parallel
microchannels, the method further comprising flowing the at least
one fluid from the first aperture into the plurality of parallel
microchannels or into one or more ports in fluid communication with
the plurality of parallel microchannels.
9. The method of claim 8, wherein the plurality of parallel
microchannels comprise at least about 6, 12, 24, 48, 96, or more
parallel microchannels.
10. The method of claim 8, further comprising assaying the at least
one fluid for one or more detectable properties in each of the
plurality of parallel microchannels simultaneously.
11. The method of claim 10, further comprising detecting the one or
more detectable properties in at least one common detection region
of the plurality of parallel microchannels using at least one
detector in or proximal to the plurality of parallel microchannels
in the at least one common detection region.
12. The method of claim 11, further comprising detecting the at
least one detectable signal in each of the plurality of parallel
microchannels simultaneously in the at least one common detection
region.
13. The method of claim 1, wherein the loading step further
comprises loading the at least one fluid into the first aperture of
each of two or more manifolds of the microfluidic device.
14. The method of claim 13, further comprising mating the body
structure sequentially to each of the two or more manifolds and
flowing the least one fluid from each of the two or more manifolds
to the plurality of ports disposed in the body structure of the
microfluidic device.
15. The method of claim 13, further comprising interchanging the
two or more manifolds such that each manifold is sequentially mated
to the body structure and flowing the at least one fluid from each
interchanged manifold to the plurality of ports disposed in the
body structure of the microfluidic device.
16. The method of claims 15, wherein at least one step is
automated.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a divisional of U.S. patent
application Ser. No. 09/922,224 filed Aug. 2, 2001, which claims
the benefit of and priority to U.S. Provisional Patent Application
No. 60/222,884, filed on Aug. 3, 2000, the contents of which are
herein incorporated by reference.
COPYRIGHT NOTIFICATION
[0002] Pursuant to 37 C.F.R. .sctn. 1.71(e), Applicants note that a
portion of this disclosure contains material that is subject to
copyright protection. The copyright owner has no objection to the
facsimile reproduction by anyone of the patent document or patent
disclosure, as it appears in the Patent and Trademark Office patent
file or records, but otherwise reserves all copyright rights
whatsoever.
BACKGROUND OF THE INVENTION
[0003] Modern pharmaceutical discovery often involves assaying or
screening immense collections of test compounds for their effects
on specific target molecules. Combinatorial chemistry and
associated technologies for generating molecular diversity have
significantly increased the number of test compounds available for
such screening. In addition, genomic research has uncovered vast
numbers of new target molecules against which the efficacy of these
test compounds may be screened. However, the search for lead
compounds in the development of these new pharmacological agents is
often impeded by the lack of sufficient throughput of many assays.
Sources which limit throughput include the time and labor
requirements associated with preparing each screen.
[0004] Microfluidic systems are one set of tools that have greatly
augmented drug discovery processes. For example, certain
multiplexed device formats that include many parallel reaction
channels within a single chip are generally well suited to perform
high numbers of simultaneous analyses. These assays typically
involve introducing assay components, such as reagents and buffers,
into the reaction channels via access ports also disposed in chip
surfaces, but which directly interface with the external
environment. As more complex channel networks have been
incorporated into these microfluidic devices, these access ports
have been drawn in closer proximity to one another. As a result,
fluid introduction into these devices, whether accomplished
manually using, e.g., a pipettor, or automatically using, e.g., a
robotic fluid handling device, is often a laborious process that
consumes significant amounts of time.
[0005] As a consequence, improved devices and methods of fluid
delivery would be desirable. The present invention is directed to
these and other features by providing high-throughput fluid
manifolds and to methods of using the same. The invention also
relates to methods of manufacturing manifold systems. These and
many other attributes will be apparent upon complete review of the
following disclosure.
SUMMARY OF THE INVENTION
[0006] The present invention generally relates to microfluidic
device manifold systems and to methods of delivering reagents to
microfluidic device components using the manifold systems. The
invention additionally provides methods of fabricating manifolds
for microfluidic devices. One advantage of the invention includes
decreasing assay preparation time since reagents are typically
loaded only one time for distribution to selected ports rather than
multiple times to each of those ports individually. This may also
help to conserve reagents which are often limited in supply. The
invention additionally simplifies instrument design and provides
for more reliable results by reducing the number of pressure/vacuum
and/or the number of electrode interfaces with a particular
device.
[0007] In particular, the present invention provides a microfluidic
device that includes a body structure having a microchannel network
and a plurality of ports disposed in the body structure. At least
one port is in fluid communication with a microchannel in the
microchannel network. The device also includes a manifold having a
manifold channel network and an aperture disposed in the manifold.
The aperture is in fluid communication with a manifold channel in
the manifold channel network. Additionally, the manifold is mated
with the body structure such that the aperture or one or more
manifold channels in the manifold channel network is in fluid
communication with one or more of the plurality of ports. The
microchannel network disposed in the body structure typically
extends in a substantially planar dimension, while the manifold
channel network disposed in the manifold includes channels
extending both horizontally and vertically within the manifold.
Optionally, the microchannel network and the manifold channel
network extend in at least horizontal and vertical planes.
[0008] In preferred embodiments, the aperture is in fluid
communication with two or more manifold channels in which at least
two of the two or more manifold channels also fluidly communicate
with a different port. The devices of the present invention also
typically include an additional aperture or manifold channel in
fluid communication with the aperture, with the at least one or
another manifold channel network, or with the port, for venting air
when the devices are loaded with reagents or filled with another
fluidic material. The manifolds of the invention also optionally
include a first alignment structure for aligning the body structure
on the first surface of the manifold.
[0009] The invention also includes a controller/detector apparatus
(e.g., an automated apparatus) configured to receive the
microfluidic device. The controller/detector apparatus generally
includes an optical and/or an electrochemical detection system and
a material transport system. The detection system and the transport
system are operably interfaced with the microfluidic device.
[0010] In one embodiment, the devices include two or more
manifolds, in which each of the two or more manifolds
interchangeably mates with the body structure for distributing a
fluid to one or more of the plurality of ports in the body
structure. In another embodiment, the invention provides two or
more body structures, in which each of the two or more body
structures interchangeably mates with the manifold for distributing
a fluid to one or more of the plurality of ports in the body
structure. These embodiments also typically include an automated
controller/detector apparatus, similar to the apparatus mentioned
above, but which additionally includes a body structure or manifold
interchange system.
[0011] In certain embodiments of the present invention, the body
structure and the manifold are integrated. For example, each of the
body structure and the manifold generally separately include a
first surface. The plurality of ports is optionally disposed in the
first surface of the body structure. Additionally, the aperture or
the one or more manifold channels in the manifold channel network
are optionally disposed in the first surface of the manifold. Upon
integration, the first surface of the manifold is typically mated
to the first surface of the body structure such that the aperture
or the one or more manifold channels in the manifold channel
network are in fluid communication with the plurality of ports
disposed in the body structure. The first surface of the body
structure and the first surface of the manifold are typically
planar. When the manifold and body structure are integrated, the
first surface of the manifold is typically mated to the first
surface of the body structure using, e.g., adhesion, heat
lamination, bonding, welding, clamping, or the like.
[0012] In preferred embodiments, the manifold optionally includes
two or more layers. The two or more layers, which are typically
fabricated from at least one polymeric, glass, or ceramic material,
are optionally bonded, adhered, welded, or clamped together.
Optionally, at least two of the two or more layers are fabricated
from different polymeric, glass, or ceramic materials. Also, the
two or more layers are alternatively approximately the same
thickness, or at least two of the two or more layers are different
thicknesses. As used herein, "thickness" refers to the depth or
height, as opposed to the length or width, e.g., of a manifold or a
layer of a manifold. Furthermore, the manifold optionally includes
at least about 3, or at least about 5, or at least about 10 layers
in which the manifold channel network and the aperture are
disposed.
[0013] The microfluidic devices of the present invention also
include other alternative embodiments. These include delivering
electrical fields to the ports and microchannels of a device body
structure by disposing a bulk viscosity enhancer and an electrolyte
in the aperture and/or manifold channel network of a manifold that
is mated with the body structure.
[0014] Electrical fields are also optionally delivered to a body
structure using various conductive coatings. For example, each of
the plurality of ports generally includes a rim disposed
circumferentially around each port in the first surface of the body
structure and an internal surface, in which a portion of the rim
and the internal surface of at least one of the plurality of ports
includes a conductive coating. The manifold also typically includes
a second surface opposite the first surface, in which the aperture
is disposed in the second surface and in fluid communication with a
manifold channel in the manifold channel network. The second
surface of the manifold is typically planar. The aperture also
typically includes a rim disposed circumferentially around the
aperture in the second surface and an internal surface, in which a
portion of the rim and the internal surface of the aperture include
a conductive coating.
[0015] Additionally, a semi-permeable membrane portion is
optionally disposed between a portion of the first surface of the
manifold and the first surface of the body structure when the first
surface of the manifold and the first surface of the body structure
are mated. The semi-permeable membrane portion is disposed between
the aperture or the one or more manifold channels in the manifold
channel network and the plurality of ports disposed in the body
structure, e.g., to sieve particle aggregates.
[0016] Other embodiments include the use of rings, e.g., to prevent
adhesives from contacting reagents flowed from manifold channels
and/or apertures into the ports of a body structure. This option
typically includes disposing a ring between the manifold and the
body structure and circumferentially around the aperture when the
aperture is aligned with at least one of the plurality of ports in
the body structure. Furthermore, a gasket is optionally disposed
between a portion of the first surface of the manifold and the
first surface of the body structure.
[0017] The present invention also relates to methods of
distributing a fluid to a plurality of ports disposed in a body
structure of a microfluidic device. The methods include loading the
fluid into a first aperture in a manifold of the microfluidic
device. The microfluidic device includes the manifold and the body
structure. Additionally, the manifold also includes a manifold
channel network disposed therein, in which the first aperture is in
fluid communication with one or more manifold channels in the
manifold channel network. Furthermore, the first aperture or
manifold channel is in fluid communication with the plurality of
ports. A microchannel network is also in fluid communication with
the plurality of ports. The methods further include flowing the
fluid using a fluid direction component from the first aperture
through the manifold channel network such that the fluid is
distributed to the plurality of ports disposed in the body
structure of the microfluidic device. The methods also optionally
include interchangeably mating manifolds and body structures.
[0018] In certain embodiments, a portion of the microchannel
network includes a plurality of parallel microchannels and the
methods additionally include flowing the fluid from the first
aperture into the plurality of parallel microchannels or into one
or more ports in fluid communication with the plurality of parallel
microchannels. For example, the plurality of parallel microchannels
optionally include at least about 6, 12, 24, 48, 96, or more
parallel microchannels. The methods also include assaying the fluid
for detectable properties in each of the plurality of parallel
microchannels simultaneously. Optionally, the methods include
detecting the detectable properties in a common detection region of
the plurality of parallel microchannels using a detector in or
proximal to the plurality of parallel microchannels in the common
detection region. The methods also optionally include detecting the
detectable signal in each of the plurality of parallel
microchannels simultaneously in the common detection region.
[0019] The present invention also includes methods of fabricating a
manifold for a microfluidic device. The methods include forming one
or more layers using a fabrication process to include an aperture
disposed in the one or more layers. The aperture is in fluid
communication with one or more manifold channel networks disposed
in at least one of the one or more layers, in which the manifold is
structurally configured to mate with a body structure of the
microfluidic device. The methods include optionally bonding,
adhering, welding, or clamping the two or more layers together such
that the aperture is in fluid communication with the one or more
manifold channel networks disposed in at least one of the two or
more layers.
BRIEF DESCRIPTION OF THE FIGURES
[0020] FIGS. 1 A and B illustrate an embodiment of an unassembled
and an assembled body structure of a microfluidic device.
[0021] FIG. 2 illustrates the unassembled components of a
three-layered manifold for delivering fluid to seven different
ports in a body structure.
[0022] FIG. 3 illustrates the unassembled components of a
two-layered manifold that includes venting apertures for venting
air from the device during fluid delivery to a body structure.
[0023] FIGS. 4A-D illustrate one embodiment of the assembled two
layered manifold shown in FIG. 3 from various viewpoints.
[0024] FIG. 5 illustrates a cross-section through a mated manifold
and body structure.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The present invention generally relates to fluid manifold
systems and to improved methods of fluid delivery. In particular,
the present invention is directed to manifold devices and to
methods of utilizing those devices to deliver reagents or other
fluid components to microfluidic device components. The invention
also provides methods for fabricating manifolds for microfluidic
devices.
[0026] In general, manifolds typically include three dimensional
fluid distribution systems, such as apertures and/or manifold
channel networks that interface external reagent reservoirs, wells,
or ports disposed in surfaces of microfluidic device body
structures. Body structures generally include at least one
microchannel network that intersects with at least one port.
Microchannel networks typically extend in a substantially planar
dimension, which imposes certain topological constraints on fluid
delivery. The manifolds of the present invention remove these
constraints such that a single reagent well or aperture in the
manifold fluidly communicates with, e.g., a large number of
parallel microchannels disposed within a microfluidic chip. This
decreases assay preparation time because reagents are only loaded
once instead of multiple times, thus leading to higher throughput
and to less reagent consumption.
[0027] Manifolds and body structures are optionally integrated or
interchangeable. As used herein, an "integrated manifold" refers to
a single manifold that is bonded, adhered, welded, clamped, or
otherwise integrated with a single microfluidic device body
structure. That is, integrated manifolds are not interchangeable
with other device body structures. In contrast, an "interchangeable
manifold" refers to a single manifold that is optionally mated or
otherwise operably interfaced with more than one microfluidic
device body structure (e.g., in series), e.g., to deliver fluids to
each body structure.
[0028] In either format, this layer of interfacing a microfluidic
device body structure with the external environment facilitates the
scalability of multiplexed microfluidic devices or chips having a
large number of parallel microchannels without increasing
proportionately the number of ports accessed by the outside world.
The planar microfluidic device body structures or chips of the
present invention have at least one, but typically a plurality of
access ports which fluidly communicate with one or more microscale
channel networks, conduits, and/or chambers fabricated within each
microfluidic device body structure. Access ports are generally
positioned in a top surface of a body structure or chip, e.g., when
the device is oriented for typical operational usage, and are
optionally used to introduce various fluids (e.g., reagents,
buffers, etc.), electrical fields, fluid transport components, or
the like. These planar microfluidic device body structures also
optionally include one or more capillary elements extending from,
e.g., a bottom surface (opposite the top surface) of the structures
and which fluidly communicate with the microchannels and/or other
cavities disposed within the devices. Capillary elements are also
typically used to introduce fluid components into the devices.
[0029] Other advantages of the invention include that the device
interface with equipment hardware, e.g., vacuum and/or pressure
sources, electrodes, or the like, is unchanged regardless of the
number of parallel microchannels incorporated into a single body
structure. As a result, as mentioned above, these devices are
easily scalable. In addition, the pattern of ports disposed in the
surface of a particular microfluidic device body structure does not
need to exactly mirror the pattern of apertures or manifold channel
termini that emerges from a given manifold structure. In turn, the
same pattern of body structure ports is optionally cost effectively
mass-produced for use with any manifold system. To further decrease
manufacturing costs, manifold channels are optionally fabricated
with dimensions that are larger than those at the microscale.
Furthermore, manifolds provide well or aperture locations that are
adequately spaced to avoid optical detection interference.
[0030] The following provides details regarding various aspects of
the methods and devices of manifold-based fluid delivery. It also
provides details pertaining to the methods of fabricating fluid
manifold systems.
Fluid Delivery Devices
[0031] The present invention generally relates to microfluidic
device manifold systems that include microfluidic body structures
and manifolds. In particular, the present invention provides a
microfluidic device that includes a body structure having a
microchannel network and a plurality of ports disposed in the body
structure. At least one port is in fluid communication with a
microchannel in the microchannel network. Materials and fabrication
methods used to produce microfluidic body structures as well as
other related features are described further below.
[0032] FIG. 1A illustrates one embodiment of a body structure of a
microfluidic device, prior to assembly, which incorporates a
planar, layered structure. As shown, unassembled body structure 100
includes upper layer 102 and lower layer 104. Upper layer 102
includes plurality of ports 106 fabricated through the layer. Upper
surface 108 of lower layer 104 is fabricated to include grooves
and/or wells 110. Lower surface 114 of upper layer 102 is then
mated (e.g., thermally bonded, ultrasonically welded, etc.) to
upper surface 108 of lower layer 104 such that grooves and/or wells
110 define channels (e.g., microchannels), conduits, and/or
chambers, within the interior of the aggregate body structure,
which fluidly communicate with plurality of ports 106. FIG. 1B
illustrates assembled body structure 112.
[0033] As indicated, the microfluidic devices of the invention also
include manifolds for delivering fluids to the device body
structures. A manifold generally includes at least one, but
typically more than one manifold channel network and at least one
aperture disposed in the manifold. Manifold channels in the at
least one manifold channel network disposed in the manifold
typically include a cross-sectional dimension of at least about 5
.mu.m, 10 .mu.m, 50 .mu.m, 100 .mu.m, 250 .mu.m, 500 .mu.m, 1,000
.mu.m, 5,000 .mu.m, or more. The aperture is typically in fluid
communication with at least one manifold channel in a manifold
channel network. Apertures also generally include a depth of at
least about 1 mm, 5 mm, 10 mm, 100 mm, or more and have a volume of
at least about 1 .mu.l, 10 .mu.l, 100 .mu.l, 1,000 .mu.l, or
more.
[0034] A manifold is typically mated with a body structure such
that the aperture or one or more manifold channels in the manifold
channel network is in fluid communication with one or more of the
plurality of ports disposed in the body structure. In certain
embodiments, manifolds are integrated with body structures (e.g.,
adhered (e.g., using glue, tape, pressure sensitive adhesive,
ultraviolet-curable adhesive, etc.), heat laminated, welded,
bonded, clamped, or the like). In other embodiments, more than one
manifold is optionally used to deliver fluids to a particular body
structure, or multiple body structures are optionally interfaced
with a particular manifold for fluid delivery to each individual
body structure. Alternatively, multiple manifolds are interchanged
with multiple body structures in accordance with the particular
application (e.g., high-throughput screening of large numbers of
test compounds, etc.). These latter embodiments generally involve
an automated manifold/body structure interchange system. All of
these methods of mating manifolds with body structures are
discussed in greater detail below. See, e.g., Published PCT
Application No. WO 99/43432.
[0035] In preferred embodiments, an aperture is in fluid
communication with two or more manifold channels in which at least
two of the two or more manifold channels also fluidly communicate
with a different port. Optionally, each of the two or more manifold
channels also fluidly communicates with a different port. As a
result, manifolds are optionally designed for delivering fluids to
any combination of ports on a particular body structure. For
example, a manifold is optionally designed to deliver fluid to as
few as one to as many as all 16 ports, or any combination of ports
therebetween, included in the body structure embodiment illustrated
in FIGS. 1A and 1B (i.e., on a 16 port device). Manifolds are
optionally designed for use with essentially any body structure
embodiment that includes one or more ports, reservoirs, wells,
and/or comparable access components. Furthermore, although any
number of apertures are optionally included in the manifolds of the
present invention, one significant advantage of these manifold
systems is that as few as one aperture is optionally included for
delivering fluids to any number/combination of ports included in a
particular body structure.
[0036] Prior to assembly, the manifolds of the present invention
optionally include two or more layers. The two or more layers,
which are typically fabricated from at least one polymeric, glass,
or ceramic material, are optionally bonded, adhered, welded,
bonded, or clamped together. Optionally, at least two of the two or
more layers are fabricated from different polymeric, glass, or
ceramic materials. Furthermore, the two or more layers are
alternatively approximately the same thickness, or at least two of
the two or more layers are different thicknesses. For example, at
least one of the two or more layers of the manifold optionally
includes a thickness of at least about 1 .mu.m, 10 .mu.m, 100
.mu.m, 1 mm, 5 mm, 1 cm, or more. Manifolds optionally include at
least about 3, or at least about 5, or at least about 10 layers in
which manifold channel networks and apertures are disposed.
Additionally, the manifold (e.g., when constructed as a single
layer) or the two or more layers of the manifold (e.g., in
multi-layered manifolds) are optionally fabricated using a process
selected from, e.g., injection molding, cast molding, compression
molding, extrusion, embossing, etching, or the like.
[0037] The manifold fluid distribution system components (e.g., the
series of fluidly communicating manifold channels, apertures,
and/or manifold cavities) optionally include various dimensions. As
mentioned above, for example, manifold channels optionally include
a cross-sectional dimension of at least about 5 .mu.m, 10 .mu.m, 50
.mu.m, 100 .mu.m, 250 .mu.m, 500 .mu.m, 1,000 .mu.m, 5,000 .mu.m,
or more. At manifold channel cross-sectional dimensions of less
than, e.g., about 50 .mu.m, the manifold channels function as
additional microfluidic components, because at these dimensions
manifold channels have the same hydrodynamic and electrical
resistance characteristics as the channels or other cavities
disposed in device body structures. However, manifold components
are optionally designed to provide negligible hydrodynamic and
electrical resistances such that only the dimensions of the
microchannels disposed within the body structures control the
microfluidic function. These design considerations typically
utilize manifold channel dimensions that are at least 50 .mu.m or
at least 100 .mu.m in at least one cross-sectional dimension, or
more preferably at least an order of magnitude larger than analysis
microchannels disposed in the body structures. These dimensions are
adequately large to use standard polymer processing technologies,
such as some of those mentioned above (e.g., injection molding,
compression molding, extrusion, embossing, etc.) to fabricate the
multi-layer manifold structure for fluid distribution of reagents
and buffers. These polymer-processing technologies are typically
technically less difficult and more cost effective than techniques
used to form smaller scale channels or other cavities.
[0038] A multi-layered manifold fluid distribution system is
illustrated in FIG. 2, which depicts the unassembled components of
three layered manifold 200 for delivering fluid to seven different
ports in body structure 202. As shown, top manifold layer 204
includes two apertures 206, one of which will fluidly communicate
with middle layer manifold channel network 208 in middle manifold
layer 210, while the other will fluidly communicate with aperture
212 in middle manifold layer 210. The manifold channels of middle
layer manifold channel network 208 also fluidly communicate with
three apertures 214 in middle manifold layer 210, which will
fluidly communicate with three apertures 216 in bottom manifold
layer 218. Three apertures 216 will also fluidly communicate with
three ports 220 of body structure 202. Aperture 212 in middle
manifold layer 210 will fluidly communicate with bottom layer
manifold channel network 222. The manifold channels of bottom layer
manifold channel also fluidly communicate with four apertures 224
in bottom manifold layer 218, which will fluidly communicate with
four ports 226 in body structure 202. As a result, after manifold
200 is assembled, fluids are optionally loaded into one or both of
two apertures 206 for distribution to either ports 220 and/or ports
226 in body structure 202. As mentioned, the fluid manifolds of the
present invention dramatically decrease assay preparation times,
because reagents or other fluids are typically loaded only one time
rather than multiple times for distribution to selected ports on a
particular body structure.
[0039] The devices of the present invention also typically include
an additional aperture (e.g., paired apertures, etc.) or manifold
channel in fluid communication with the aperture, with the at least
one or another manifold channel network, or with the port, for
venting air when the devices are loaded with reagents and
facilitate quick replacement of reagents.
[0040] One embodiment of this is illustrated in FIG. 3, which
schematically depicts the unassembled components of two layered
manifold 300, which includes venting apertures 302. As shown, top
manifold layer 304 includes aperture 306 and five venting apertures
302. Aperture 306 will fluidly communicate with bottom layer
manifold channel network 308, which is disposed in, e.g., a surface
of bottom manifold layer 310. The manifold channels of bottom layer
manifold channel network 308 also fluidly communicate with five
apertures 312 in bottom manifold layer 310, which will fluidly
communicate with five ports 314 disposed in body structure 316.
Five venting apertures 302 disposed through top manifold layer 304
will fluidly communicate with five apertures 312 such that in the
assembled manifold when fluid is flowed into aperture 306 and
through bottom layer manifold channel network 308 to five apertures
312 air is vented out of manifold 300 through five venting
apertures 302.
[0041] FIG. 4 illustrates one embodiment of the assembled manifold
shown unassembled in FIG. 3 from the top (FIG. 4A), bottom (FIG.
4B), top perspective (FIG. 4C), and bottom perspective views (FIG.
4D). As shown, manifold 400 is planar in shape having upper planar
surface 402 and lower planar surface 404. Also included are
apertures 406 disposed in lower planar surface 404 which fluidly
communicate with a manifold channel network (not shown) contained
within manifold 400 and with venting apertures 408 disposed in
upper planar surface 402. As mentioned with respect to FIG. 3,
apertures 406 are positioned within lower planar surface 404 so as
to align with selected ports/reservoirs in the body structure of a
microfluidic device when that body structure is mated to lower
planar surface 404 of manifold 400.
[0042] The devices of present invention also include many other
embodiments, which are optionally used alone or in combination with
one another. For example, although not shown, rings are optionally
disposed between and surrounding the aligned apertures and ports
to, e.g., prevent adhesive (e.g., ultraviolet-curable adhesive,
etc.) from getting into the ports and in turn from contacting assay
components in the ports. Semi-permeable membranes (not shown) are
also optionally disposed between aligned apertures and ports for
use in controlling material compositions within the devices, such
as by sieving aggregations of materials (e.g., clumps of cells,
particles, reagents, etc.) and delivering material into the
devices. Conductive coatings are also optionally used, e.g., to
minimize cross-contamination among devices when electrical fields
are delivered into devices. All of these features are described in
greater detail in, e.g., U.S. patent application Ser. No.
09/544,711 to Dubrow et al. entitled "Microfluidic Devices and
Systems Incorporating Cover Layers," which was filed Apr. 6, 2000
and which is incorporated by reference herein in its entirety for
all purposes.
[0043] In other embodiments, aperture 412, the manifold channel
network (not shown), and apertures 416 also include a bulk
viscosity enhancer and an electrolyte (e.g., a salt, a buffering
ionic species, etc.) disposed therein for delivering electrical
fields to device body structures. (FIG. 4). A "bulk viscosity
enhancer," as used herein, includes molecules capable of increasing
the bulk viscosity of a solution. Suitable bulk viscosity enhancers
include aqueous-based solutions of single polymers, polymer
mixtures, copolymers, block copolymers, polymer micellar systems,
interpenetration polymer networks, or the like. The diffusive
mobility of the electrolyte is substantially unaffected by the
increase in bulk hydrodynamic resistance within the microscale
cavity, e.g., due to the small size of the electrolyte relative to
the hydrodynamic radius of the bulk viscosity enhancer. As a
result, low electrical resistance is induced in the microfluidic
device. The use of bulk viscosity enhancers and electrolytes in
delivering electrical fields is described in greater detail in,
e.g., Provisional U.S. Patent Application No. 60/203,498 by Chow et
al., entitled "Microfluidic Devices and Methods to Regulate
Hydrodynamic and Electrical Resistance Utilizing Bulk Viscosity
Enhancers," filed May 11, 2000, which is incorporated by reference
herein in its entirety for all purposes.
[0044] As also shown in FIG. 4, annular ridge 410 is optionally
provided on upper planar surface 402 of manifold 400, surrounding
aperture 412. This ridge provides a barrier between neighboring
reservoirs (when present) and also functions to increase the
effective volume of each reservoir in the device. The walls of
aperture 412 and a rim disposed in annular ridge 410 also
optionally include a conductive coating, e.g., for delivering an
electrical field into the device.
[0045] FIG. 4 also illustrates that lower planar surface 404 of
manifold 400, typically has fabricated thereon, a series of raised
ridges 414, which function as alignment structures to ensure the
body structure of the microfluidic device (such as the body
structure shown in FIG. 3), is properly aligned with manifold 400
during, e.g., bonding or interchange processes. Although
illustrated as ridges, it will be understood that a number of
different alignment structures are optionally provided upon lower
planar surface 404 for aligning the body structure of the device
with manifold 400. For example, a recessed region, which is
configured to fit the body structure is optionally used, whereby
placement of the body structure into the recessed region positions
the body structure to be appropriately aligned with apertures 406
in manifold 400. Alternatively, alignment pins are provided
extending from the lower surface, against which the body structure
is optionally positioned, when appropriately aligned with manifold
400.
[0046] Also optionally included on lower planar surface 404 of
manifold 400 are small high spots 414. These high spots, or bumps,
maintain the body structure in a position slightly set off of lower
planar surface 404 when the body structure is mated with manifold
400. The small set off resulting from high spots 414 allows a
bonding adhesive material to wick into the space between the body
structure and manifold 400 in embodiments where the body structure
and manifold are integrated.
[0047] As shown, manifold 400 includes side-walls 418, which extend
from lower planar surface 404, effectively creating a hollow-backed
structure. (FIG. 4). This hollow-backed structure permits the
mounting or mating of a body structure of a microfluidic device to
lower planar surface 404 of manifold 400 without altering the
overall profile of manifold 400, e.g., permitting the combined
device-manifold to be laid flat upon a surface or stacked with
other like devices, as well as providing benefits in manufacturing,
e.g., curing/hardening of molded parts, etc.
[0048] In addition to providing alignment structures for mounting a
body structure to manifold 400, as shown, manifold 400 also
optionally includes additional alignment structures 420 and 422.
(FIG. 4). These alignment structures permit the appropriate
alignment of the overall device into an appropriate base unit, such
as a controller/detector instrument (not shown). In particular,
alignment holes 420 provided disposed at least partially through
manifold 400 are complementary to alignment pins that are typically
provided on a controller/detector instrument (not shown). By
matching the pins of the controller/detector instrument (described
further below) with alignment holes 420 on the overall device, one
is assured of proper alignment of the device with the appropriate
elements of the instrument, e.g., electrodes, optical detectors,
thermal blocks, etc. In addition to alignment holes 420, manifold
400 also optionally includes beveled corner 422, which further
ensures proper alignment of the device in the controller/detector
instrument. Again, a number of different types of alignment
structures are optionally used to accomplish this same purpose,
including irregular edges (e.g., beveled, tabbed, etc.), alignment
pins, non-uniform shapes, or the like.
[0049] As shown, manifold 400 also includes optional convenience
features. For example, textured regions 424 are provided on
side-walls 418, to provide gripping surfaces, e.g., for manual
handling of manifold 400 or an integrated device. Also provided is
registry port 426 disposed through manifold 400. Different numbers,
sizes and/or shapes of registry ports are optionally provided in
the cover layer to register the type of microfluidic device that
has been inserted in a controller/detector instrument. This ensures
that the proper interface is used and/or the proper control program
is being run.
[0050] In general, the controller/detector apparatus, which is
optionally an automated apparatus, is typically configured to
receive the microfluidic device. The controller/detector apparatus
generally includes an optical and/or an electrochemical detection
system and a material transport system. Additionally, the detection
system and the transport system are operably interfaced with the
microfluidic device. Controller/detector instrumentation is
described in greater detail below.
[0051] As mentioned, in certain embodiments of the present
invention the body structure and the manifold are integrated. For
example, each of the body structure and the manifold generally
separately include a first surface. The plurality of ports is
optionally disposed in the first surface of the body structure.
Additionally, the aperture or the one or more manifold channels in
the manifold channel network are optionally disposed in the first
surface of the manifold. Upon integration, the first surface of the
manifold is typically mated to the first surface of the body
structure such that the aperture or the one or more manifold
channels in the manifold channel network are in fluid communication
with the plurality of ports disposed in the body structure. The
first surface of the body structure and the first surface of the
manifold are typically planar. When the manifold and body structure
are integrated, the first surface of the manifold is typically
mated to the first surface of the body structure using, e.g.,
adhesion, heat lamination, welding, clamping, or the like.
[0052] A cross-section through an integrated manifold and body
structure is depicted in FIG. 5. As shown, manifold 500 includes
aperture 502 in fluid communication with manifold channel network
504, which in turn fluidly communicates with ports 506 disposed in
integrated body structure 508. Ports 506 also fluidly communicate
with microchannels 510 disposed within body structure 508.
[0053] In addition to the manifolds of the present invention, a
separate cover layer component is also optionally included which
interfaces with the surface of a manifold opposite the
manifold/body structure interface. The optional cover layer
component provides the capability to further increase the volume
capacity of the manifold apertures. In particular, the cover layer
typically includes one or more apertures which align with manifold
apertures when the cover layer is mated with the manifold to
increase the total depth of the manifold apertures. These and other
cover layer embodiments which are optionally adapted to the devices
of the present invention are described in greater detail in, e.g.,
Provisional U.S. Patent Application No. 60/203,498 by Chow et al.,
entitled "Microfluidic Devices and Methods to Regulate Hydrodynamic
and Electrical Resistance Utilizing Bulk Viscosity Enhancers,"
filed May 11, 2000, which is incorporated by reference herein in
its entirety for all purposes.
Methods of Fluid Delivery
[0054] The present invention also relates to methods of
distributing a fluid to a plurality of ports disposed in a body
structure of a microfluidic device. As mentioned, one significant
advantage of the present invention is that manifolds are optionally
designed such that a reagent or other fluid is loaded into an
aperture one time for distribution to multiple ports, instead of
delivering the fluid to each of the multiple ports by, e.g.,
pipetting into each individually. This feature of the invention
increases the throughput of a given application, e.g., screening
numerous test compounds when each assay utilizes the same reagents
and/or buffers.
[0055] The methods typically include loading the fluid into a first
aperture in a manifold of the microfluidic device. The microfluidic
device includes the manifold and the body structure. Additionally,
the manifold also includes a manifold channel network disposed
therein, in which the first aperture is in fluid communication with
one or more manifold channels in the manifold channel network.
Furthermore, the first aperture or manifold channel is in fluid
communication with the plurality of ports. Also, a microchannel
network is in fluid communication with the plurality of ports. The
methods also include flowing the fluid using a fluid direction
component from the first aperture through the manifold channel
network such that the fluid is distributed to the plurality of
ports disposed in the body structure of the microfluidic device. In
preferred embodiments, the methods of the invention include
providing a second aperture or manifold channel in the manifold, in
which the second aperture or manifold channel is in fluid
communication with the first aperture, with the at least one or
another manifold channel network, or with the plurality of ports,
for venting air from the microfluidic device during the loading or
the flowing steps.
[0056] In one embodiment, the methods include providing a second
aperture or manifold channel in the manifold, in which the second
aperture or manifold channel is in fluid communication with the
plurality of ports, in which the second aperture or manifold
channel include a bulk viscosity enhancer and an electrolyte
disposed therein for delivering an electrical field to the
plurality of ports during operation of the device. The use of bulk
viscosity enhancers and electrolytes is discussed further
above.
[0057] The methods also optionally include interchanging two or
more body structures such that each body structure is sequentially
mated to the manifold and flowing the fluid from the manifold to
the plurality of ports disposed in each interchanged body
structure. Optionally, at least one step in these methods is
automated. A further option includes rotating either the particular
body structure or the particular manifold relative to one another
sequentially after individual fluid delivery steps for additional
delivery combinations using the manifold pattern.
[0058] In certain preferred embodiments, a portion of the
microchannel network includes a plurality of parallel microchannels
(e.g., planar chips with multiplexed channel networks) and the
methods additionally include flowing the fluid from the first
aperture into the plurality of parallel microchannels or into one
or more ports in fluid communication with the plurality of parallel
microchannels. For example, the plurality of parallel microchannels
optionally include at least about 6, 12, 24, 48, 96, or more
parallel microchannels. The methods also include assaying the fluid
for detectable properties in each of the plurality of parallel
microchannels simultaneously. Optionally, the methods include
detecting the detectable properties in a common detection region of
the plurality of parallel microchannels using a detector in or
proximal to the plurality of parallel microchannels in the common
detection region. The methods also optionally include detecting the
detectable signal in each of the plurality of parallel
microchannels simultaneously in the common detection region. For
additional discussion of parallel screening techniques, see, e.g.,
U.S. Pat. No. 6,046,056 to Parce, et al., entitled "High Throughput
Screening Assay Systems in Microscale Fluidic Devices," which
issued Apr. 4, 2000 and which is incorporated by reference herein
in its entirety for all purposes.
[0059] In other embodiments of the methods, the loading step
includes loading the fluid into the first aperture of each of two
or more manifolds of the microfluidic device. Thereafter, the
methods typically include interchanging the two or more manifolds
such that each manifold is sequentially mated to the body structure
and flowing the at least one fluid from each interchanged manifold
to the plurality of ports disposed in the body structure of the
microfluidic device. Optionally, at least one step in these methods
is automated. The methods of the invention also optionally include
mating the body structure sequentially to each of the two or more
manifolds and flowing the least one fluid from each of the two or
more manifolds to the plurality of ports disposed in the body
structure of the microfluidic device.
[0060] The methods of the invention optionally include flowing a
fluid in the manifold channel or microchannel networks using
various fluid direction components that optionally include, e.g., a
fluid pressure force modulator, an electrokinetic force modulator,
a capillary force modulator, a gravity force modulator, a magnetic
force modulator, a dielectrophoretic force modulator, a fluid
wicking element, or the like. In preferred embodiments, fluid is
flowed in the manifold channel network using a first gravity force
modulator and in the at least one microchannel network using
alternative fluid direction components that also optionally include
a fluid pressure force modulator, an electrokinetic force
modulator, a capillary force modulator, a second gravity force
modulator, a magnetic force modulator, a dielectrophoretic force
modulator, a fluid wicking element, or the like. The first and
second gravity force modulators are optionally the same. Techniques
of flowing fluids in the devices of the present invention are
discussed further below.
[0061] In one embodiment, reagents are optionally first loaded
directly into a device body structure followed by other fluidic
materials (e.g., buffers or the like) which are delivered to the
body structure through a manifold. This method helps to conserve
reagents, which are often available only in limited amounts.
Integrated Systems
[0062] The manifolds of the present invention, whether fully
integrated or interchangeable with one or more body structures, are
optionally included as components of integrated systems to further
enhance throughput. In one embodiment, for example, the devices
include two or more manifolds, in which each of the two or more
manifolds interchangeably mates with the body structure for
distributing a fluid to one or more of the plurality of ports in
the body structure. This embodiment typically also includes a
controller/detector apparatus (e.g., an automated apparatus)
configured to interchangeably receive the body structure or each of
the two or more manifolds. This controller/detector apparatus
typically includes an optical and/or an electrochemical detection
system, a material transport system, and a body structure or
manifold interchange system. The detection system, the transport
system, and the body structure or manifold interchange system are
generally operably interfaced with the microfluidic device.
[0063] In another embodiment, the invention provides two or more
body structures, in which each of the two or more body structures
interchangeably mates with the manifold for distributing a fluid to
one or more of the plurality of ports in the body structure. This
embodiment also generally includes a controller/detector apparatus
(e.g., an automated apparatus) configured to interchangeably
receive the two or more body structures or the manifold. The
controller/detector apparatus also typically includes an optical
and/or an electrochemical detection system, a material transport
system, and a body structure or manifold interchange system. The
detection system, the transport system, and the body structure or
manifold interchange system are typically operably interfaced with
the microfluidic device.
[0064] Instrumentation
[0065] The systems described herein generally include integrated
fluid manifolds and/or interchangeable manifolds and body
structures, as described above, in conjunction with additional
instrumentation for dispensing fluids into manifolds, for
orienting, mating, and/or interchanging the devices disclosed
herein, for controlling electric fields, fluid transport, flow rate
and direction within the devices, detection instrumentation for
detecting or sensing results of the operations performed by the
system, processors, e.g., computers, for instructing the
controlling instrumentation in accordance with preprogrammed
instructions, receiving data from the detection instrumentation,
and for analyzing, storing and interpreting the data, and providing
the data and interpretations in a readily accessible reporting
format.
[0066] Controllers
[0067] A variety of controlling instrumentation is optionally
utilized in conjunction with the microfluidic devices described
above, for manipulating the manifolding systems of the invention,
for controlling the delivery, transport, and direction of fluids
and/or materials within the devices of the present invention, e.g.,
by pressure-based or electrokinetic control, or the like.
[0068] As described herein, in many cases, transport,
concentration, and direction (e.g., reagents or other fluids) are
controlled in whole or in part, using pressure based flow systems
that incorporate external or internal pressure sources to drive
fluid flow. Internal sources include microfabricated pumps, e.g.,
diaphragm pumps, thermal pumps, and the like that have been
described in the art. See, e.g., U.S. Pat. Nos. 5,271,724,
5,277,556, and 5,375,979 and Published PCT Application Nos. WO
94/05414 and WO 97/02357. As also noted, the systems described
herein also optionally utilize electrokinetic material direction
and transport systems. In certain embodiments, gravity-based flow
is used to induce fluid movement through the channels, apertures,
or other chambers of manifolds, while other sources of fluid
direction including pressure, electrokinetic, or other sources are
used for fluid direction within device body structures.
[0069] Typically, the controller systems are appropriately
configured to receive or interface with a microfluidic device or
system element (e.g., an automated manifold/body structure
interchange system), such as one or more manifolds and/or one or
more body structures, as described herein. For example, the
controller, interchanger and/or detector, optionally includes a
stage upon which the integrated manifold or interchangeable
components thereof are mounted to facilitate appropriate
interfacing between the controller and/or detector and the device
components. Typically, the stage includes an appropriate
mounting/alignment structural element, such as a nesting well,
alignment pins and/or holes, asymmetric edge structures (to
facilitate proper device alignment), and the like. Many such
configurations are described in the references cited herein.
[0070] The controlling instrumentation discussed above is also used
to provide for electrokinetic injection or withdrawal of material
downstream of the region of interest to control an upstream flow
rate. The same instrumentation and techniques described above are
also utilized to inject a fluid into a downstream port to function
as a flow control element.
[0071] Detector
[0072] The devices herein optionally include optical,
electrochemical, and/or other signal detectors which detect, e.g.,
concentration, fluorescence, phosphorescence, radioactivity, pH,
charge, absorbance, refractive index, luminescence, temperature,
magnetism, mass, or the like. The detector(s) optionally monitors
one or a plurality of signals from upstream and/or downstream of an
assay mixing point in which, e.g., a ligand and an enzyme are
mixed. For example, the detector optionally monitors a plurality of
optical signals that correspond in position to "real time" assay
results.
[0073] Example detectors or sensors include photomultiplier tubes,
CCD arrays, optical sensors, temperature sensors, pressure sensors,
pH sensors, conductivity sensors, mass sensors, scanning detectors,
or the like. Cells or other components that emit a detectable
signal are optionally flowed past the detector, or, alternatively,
the detector moves relative to the array to determine the position
of an assay component (or, the detector optionally simultaneously
monitors a number of spatial positions corresponding to channel
regions, e.g., as in a CCD array). Each of these types of sensors
is optionally readily incorporated into the microfluidic systems
described herein. In these systems, such detectors are placed
either within or adjacent to the microfluidic device or one or more
channels, chambers or conduits of the device, such that the
detector is within sensory communication with the device, channel,
or chamber. The phrase "within sensory communication" of a
particular region or element, as used herein, generally refers to
the placement of the detector in a position such that the detector
is capable of detecting the property of the microfluidic device, a
portion of the microfluidic device, or the contents of a portion of
the microfluidic device, for which that detector was intended. The
detector optionally includes or is operably linked to a computer,
e.g., which has software for converting detector signal information
into assay result information (e.g., kinetic data of modulator
activity), or the like. A microfluidic system optionally employs
multiple different detection systems for monitoring the output of
the system. Detection systems of the present invention are used to
detect and monitor the materials in a particular channel region (or
other reaction detection region).
[0074] The detector optionally exists as a separate unit, but is
preferably integrated with the controller system, into a single
instrument. Integration of these functions into a single unit
facilitates connection of these instruments with the computer
(described below), by permitting the use of few or a single
communication port(s) for transmitting information between the
controller, the detector and the computer.
[0075] Computer
[0076] As noted above, either or both of the controller system
and/or the detection system is/are optionally coupled to an
appropriately programmed processor or computer which functions to
instruct the operation of these instruments in accordance with
preprogrammed or user input instructions (e.g., interchanging
manifolds and/or body structures, delivering selected amounts of
fluidic reagents, etc.), receive data and information from these
instruments, and interpret, manipulate and report this information
to the user. As such, the computer is typically appropriately
coupled to one or both of these instruments (e.g., including an
analog to digital or digital to analog converter as needed).
[0077] The computer typically includes appropriate software for
receiving user instructions, either in the form of user input into
a set parameter fields, e.g., in a GUI, or in the form of
preprogrammed instructions, e.g., preprogrammed for a variety of
different specific operations. The software then converts these
instructions to appropriate language for instructing the operation
of the fluid direction, transport controller, and manifold/body
structure interchange controller to carry out the desired
operation, such as interfacing a manifold with a particular
manifold channel pattern with a selected body structure or loading
fluids into a manifold aperture. The computer then receives the
data from the one or more sensors/detectors included within the
system, and interprets the data, either provides it in a user
understood format, or uses that data to initiate further controller
instructions, in accordance with the programming, e.g., such as in
monitoring and control of flow rates, temperatures, applied
voltages, and the like.
[0078] In the present invention, the computer typically includes
software for the monitoring of materials, such as reagent
concentrations in the channels. Additionally, the software is
optionally used to control pressure or electrokinetic modulated
injection or withdrawal of material.
Manifold Fabrication
[0079] The present invention also includes methods of fabricating a
manifold for a microfluidic device. In general, the methods include
forming one or more layers using a fabrication process to include
an aperture disposed in the one or more layers. Upon assembly, the
aperture is in fluid communication with one or more manifold
channel networks disposed in at least one of the one or more
layers, in which the manifold is structurally configured to mate
with a body structure of the microfluidic device. The methods
include optionally bonding, adhering, welding, or clamping the two
or more layers together such that the aperture is in fluid
communication with the one or more manifold channel networks
disposed in at least one of the two or more layers. The methods
typically include forming the manifold to comprise one or more
substantially planar layers. See, e.g., FIGS. 2 and 3, and the
discussion related thereto. Additionally, the methods include
forming the one or more layers using a fabrication process selected
from, e.g., injection molding, cast molding, compression molding,
extrusion, embossing, etching, or the like.
[0080] Individual manifold layers of the microfluidic devices
described herein are generally fabricated from any of a number of
different materials using various methods. For example, the
materials and methods described below with respect to the
manufacture of the microfluidic elements of body structures are
also optionally employed in the manufacture of the manifold
devices. As indicated above, while any these methods are effective,
in preferred aspects, more conventional manufacturing techniques
are used to produce manifolds. In particular, because manifolds
generally do not need to be manufactured to the tolerances of the
microfluidic elements of the devices of the invention, they are
optionally manufactured using less precise or less time consuming
techniques and/or from lower cost materials.
[0081] For example, in a layered microfluidic device fabricated
from two glass layers, fabrication of the ports or reservoirs in
one layer, e.g., by drilling or air abrasion techniques, typically
takes a substantial amount of time. Further, the amount of time
required for such fabrication increases in a non-linear, e.g.,
exponential, fashion with increasing substrate thickness.
Conversely, reduction of substrate thickness reduces the amount of
time required to fabricate the reservoirs, in an exponential
fashion. Because a portion of the volume of the reservoirs in the
final microfluidic device is optionally supplied by, e.g., the
manifold element or an additional cover layer, the substrate layers
used to fabricate the body structure of the microfluidic device are
typically substantially thinner. Specifically, less of the total
desired volume of the reservoir is a function of substrate
thickness. As a result, fabrication time and cost associated with
the manufacturing of reservoirs in the body structure are
substantially reduced.
[0082] Typically, the manifold includes one or more injection
molded polymeric or plastic parts (e.g., layers), fabricated from
any of a number of different manufacturable plastics. For example,
a manifold layer is typically fabricated from any of the polymeric
materials described below for fabricating the body structure of the
microfluidic device, e.g., polymethylmethacrylate (PMMA),
polycarbonate, polytetrafluoroethylene (TEFLON.TM.),
polyvinylchloride (PVC), polydimethylsiloxane (PDMS), polysulfone,
polystyrene, polymethylpentene, polypropylene, polyethylene,
polyvinylidine fluoride, acrylonitrile-butadiene-styrene copolymer
(ABS), and the like. In alternate aspects, manifold layers are
optionally fabricated from non-polymeric materials, e.g.,
silica-based substrates, such as glass, quartz, silicon, as well as
ceramics or metals.
[0083] Assembly of individual layers to form a functional manifold
and/or attachment of the assembled manifold to the body structure
of the device when the two are integrated is also typically
accomplished by well known methods, including adhesive bonding,
ultrasonic welding, solvent welding, thermal bonding, and the like.
In preferred aspects, the manifold is attached to the body
structure of the device using an adhesive material, and more
preferably, ultraviolet-curable adhesives are used to join the
manifold structure with the body structure. Such adhesives are
generally commercially available, e.g., from 3M Corporation. In
particularly preferred aspects, the selected adhesive is
electrically insulating, e.g., nonconductive, non-soluble and/or
non-leaching in application buffers, low fluorescing, and the
like.
[0084] As mentioned, in one embodiment, the microfluidic device
includes a plurality of rings disposed around the reservoirs or
ports in the microfluidic body structure underlying the integrated
manifold. The rings are optionally molded around the apertures on
the first surface of the manifold and integral with the manifold.
Alternatively, the rings are molded around the ports disposed in
the first surface of the body structure and integral with the body
structure. As an additional alternative, the rings are separate
from the manifold and the body structure. Upon attachment of the
manifold to the body structure, a ring becomes disposed between
each aperture and/or at least one manifold channel terminus aligned
with each port.
[0085] The rings act to prevent adhesive, e.g., ultraviolet-curable
adhesive (mentioned above), from getting into the ports and in turn
from contacting any assay components that are in the ports. As
such, rings are optionally shaped as circular rings or as any other
functionally equivalent forms, e.g., rectangular or polygonal
rings. In the context of rings, the terms "thick" and/or
"thickness" refer to the distance from an inner edge to an outer
edge of a ring. A ring has a single thickness, as in the case of
circular rings, or multiple thicknesses when other ring shapes are
selected. However, each ring typically has a thickness in the range
of from about 1 .mu.M to about 1,000 .mu.M. For example, the rings
are optionally in the range of from about 50 .mu.M to about 750
.mu.M thick, e.g., about 500 .mu.M thick. Larger rings typically
result in the creation of voids around the ports/apertures.
Narrower rings, e.g., in the range of from about 100 .mu.M to about
500 .mu.M are generally preferred.
[0086] The rings are optionally fabricated from many different
materials. For example, if they are integral with the manifold or
the body structure, they are made from the same material, and in
the same step, as either of those two respective components. As
discussed above, these optionally include a wide variety of
polymeric and non-polymeric materials. If the rings are separate
from the manifold and the body structure, they are also optionally
fabricated from any of the polymeric or non-polymeric materials
discussed above as well as others, including polymethylmethacrylate
(PMMA), polycarbonate, polytetrafluoroethylene (TEFLON.TM.),
polyvinylchloride (PVC), polydimethylsiloxane (PDMS), polysulfone,
polystyrene, polymethylpentene, polypropylene, polyethylene,
polyvinylidine fluoride, acrylonitrile-butadiene-styrene copolymer
(ABS), glass, quartz, silicon, gallium arsenide, silicon oxide,
ceramics, metals, latex, silicone, or the like.
[0087] In alternate aspects, the body structure is attached to the
manifold via a clamping mechanism. In such aspects, an optional
flexible gasket, e.g., latex, silicone, etc., is placed between the
upper surface of the body structure and the lower surface of the
manifold. The flexible gaskets also optionally include the rings,
discussed above, as integral components therein. The body structure
is then compressively clamped against the manifold forming a
sealed, joined structure. Suitable clamping mechanisms may be
separate from the body structure/manifold assembly, i.e., screw
clamps, clip-style clamps, e.g., that clamp the edges of the body
structure and manifold, and the like. Alternatively, integrated
clamping mechanisms are provided as a portion of the manifold, into
which the body structure is snapped. The use of rings and gaskets
is described in greater detail in, e.g., U.S. patent application
Ser. No. 09/544,711 to Dubrow et al. entitled "Microfluidic Devices
and Systems Incorporating Cover Layers," which was filed Apr. 6,
2000 and which is incorporated by reference herein in its entirety
for all purposes.
Manifolds and Microfluidic Device Body Structures
[0088] The microfluidic device body structures of the present
invention, as indicated, generally include various microscale
components, such as microchannels or other conduits. While manifold
apertures and channels are optionally manufactured at the
microscale, to achieve some of the cost benefits discussed above,
manifolds are typically fabricated with apertures and/or channels
having dimensions (e.g., channel widths and/or heights) typically
about an order of magnitude or more larger than body structure
microchannels.
[0089] As used herein, the terms "microscale," "microfabricated" or
"microfluidic" generally refer to one or more fluid passages,
chambers or conduits which have at least one internal
cross-sectional dimension, e.g., depth, width, length, diameter,
etc., that is less than 500 .mu.m, and typically between about 0.1
.mu.m and about 500 .mu.m. In the devices of the present invention,
the microscale channels or chambers preferably have at least one
cross-sectional dimension between about 0.1 .mu.m and 200 .mu.m,
more preferably between about 0.1 .mu.m and 100 .mu.m, and often
between about 0.1 .mu.m and 20 .mu.m. Accordingly, the microfluidic
devices or systems prepared in accordance with the present
invention typically include at least one microscale channel,
usually at least two intersecting microscale channels, and often,
three or more intersecting channels disposed within a single body
structure. Channel intersections may exist in a number of formats,
including cross intersections, "T" intersections, or any number of
other structures whereby at least two channels are in fluid
communication.
[0090] A variety of microscale systems are optionally adapted for
use in the present invention, e.g., by incorporating integrated
manifolds, interchangeable manifolds and/or body structures,
manifolds/body structures exchange systems, or the like. These
systems are described in numerous publications by the inventors and
their coworkers, including certain issued U.S. patents, such as
U.S. Pat. Nos. 5,699,157 (J. Wallace Parce) issued Dec. 16, 1997,
5,779,868 (J. Wallace Parce et al.) issued Jul. 14, 1998, 5,800,690
(Calvin Y. H. Chow et al.) issued Sep. 01, 1998, 5,842,787 (Anne R.
Kopf-Sill et al.) issued Dec. 01, 1998, 5,852,495 (J. Wallace
Parce) issued Dec. 22, 1998, 5,869,004 (J. Wallace Parce et al.)
issued Feb. 09, 1999, 5,876,675 (Colin B. Kennedy) issued Mar. 02,
1999, 5,880,071 (J. Wallace Parce et al.) issued Mar. 09 1999,
5,882,465 (Richard J. McReynolds) issued Mar. 16, 1999, 5,885,470
(J. Wallace Parce et al.) issued Mar. 23, 1999, 5,942,443 (J.
Wallace Parce et al.) issued Aug. 24, 1999, 5,948,227 (Robert S.
Dubrow) issued Sep. 07, 1999, 5,955,028 (Calvin Y.H. Chow) issued
Sep. 21, 1999, 5,957,579 (Anne R. Kopf-Sill et al.) issued Sep. 28,
1999, 5,958,203 (J. Wallace Parce et al.) issued Sep. 28, 1999,
5,958,694 (Theo T. Nikiforov) issued Sep. 28, 1999, 5,959,291
(Morten J. Jensen) issued Sep. 28, 1999, 5,964,995 (Theo T.
Nikiforov et al.) issued Oct. 12, 1999, 5,965,001 (Calvin Y. H.
Chow et al.) issued Oct. 12, 1999, 5,965,410 (Calvin Y. H. Chow et
al.) issued Oct. 12, 1999, 5,972,187 (J. Wallace Parce et al.)
issued Oct. 26, 1999, 5,976,336 (Robert S. Dubrow et al.) issued
Nov. 2, 1999, 5,989,402 (Calvin Y. H. Chow et al.) issued Nov. 23,
1999, 6,001,231 (Anne R. Kopf-Sill) issued Dec. 14, 1999, 6,011,252
(Morten J. Jensen) issued Jan. 4, 2000, 6,012,902 (J. Wallace
Parce) issued Jan. 11, 2000, 6,042,709 (J. Wallace Parce et al.)
issued Mar. 28, 2000, 6,042,710 (Robert S. Dubrow) issued Mar. 28,
2000, 6,046,056 (J. Wallace Parce et al.) issued Apr. 4, 2000,
6,048,498 (Colin B. Kennedy) issued Apr. 11, 2000, 6,068,752
(Robert S. Dubrow et al.) issued May 30, 2000, 6,071,478 (Calvin Y.
H. Chow) issued Jun. 6, 2000, 6,074,725 (Colin B. Kennedy) issued
Jun. 13, 2000, 6,080,295 (J. Wallace Parce et al.) issued Jun. 27,
2000, 6,086,740 (Colin B. Kennedy) issued Jul. 11, 2000, 6,086,825
(Steven A. Sundberg et al.) issued Jul. 11, 2000, 6,090,251 (Steven
A. Sundberg et al.) issued Jul. 18, 2000, 6,100,541 (Robert Nagle
et al.) issued Aug. 8, 2000, 6,107,044 (Theo T. Nikiforov) issued
Aug. 22, 2000, 6,123,798 (Khushroo Gandhi et al.) issued Sep. 26,
2000, 6,129,826 (Theo T. Nikiforov et al.) issued Oct. 10, 2000,
6,132,685 (Joseph E. Kersco et al.) issued Oct. 17, 2000, 6,148,508
(Jeffrey A. Wolk) issued Nov. 21, 2000, 6,149,787 (Andrea W. Chow
et al.) issued Nov. 21, 2000 6,149,870 (J. Wallace Parce et al.)
issued Nov. 21, 2000, 6,150,119 (Anne R. Kopf-Sill et al.) issued
Nov. 21, 2000, 6,150,180 (J. Wallace Parce et al.) issued Nov. 21,
2000, 6,153,073 (Robert S. Dubrow et al.) issued Nov. 28, 2000,
6,156,181 (J. Wallace Parce et al.) issued Dec. 5, 2000, 6,167,910
(Calvin Y. H. Chow) issued Jan. 2, 2001, 6,171,067 (J. Wallace
Parce) issued Jan. 9, 2001 6,171,850 (Robert Nagle et al.) issued
Jan. 9, 2001, 6,172,353 (Morten J. Jensen) issued Jan. 9, 2001,
6,174,675 (Calvin Y. H. Chow et al.) issued Jan. 16, 2001,
6,182,733 (Richard J. McReynolds) issued Feb. 6, 2001, 6,186,660
(Anne R. Kopf-Sill et al.) issued Feb. 13, 2001, 6,221,226 (Anne R.
Kopf-Sill) issued Apr. 24, 2001, 6,233,048 (J. Wallace Parce)
issued May 15, 2001, 6,235,175 (Robert S. Dubrow et al.) issued May
22, 2001, 6,235,471 (Michael Knapp et al.) issued May 22, 2001,
6,238,538 (J. Wallace Parce et al.) issued May 29, 2001, and
6,251,343 (Robert S. Dubrow et al.) issued Jun. 26, 2001.
[0091] Systems adapted for use with the devices of the present
invention are also described in, e.g., various published PCT
applications, including WO 98/00231, WO 98/00705, WO 98/00707, WO
98/02728, WO 98/05424, WO 98/22811, WO 98/45481, WO 98/45929, WO
98/46438, and WO 98/49548, WO 98/55852, WO 98/56505, WO 98/56956,
WO 99/00649, WO 99/10735, WO 99/12016, WO 99/16162, WO 99/19056, WO
99/19516, WO 99/29497, WO 99/31495, WO 99/34205, WO 99/43432, WO
99/44217, WO 99/56954, WO 99/64836, WO 99/64840, WO 99/64848, WO
99/67639, WO 00/07026, WO 00/09753, WO 00/10015, WO 00/21666, WO
00/22424, WO 00/26657, WO 00/42212, WO 00/43766, WO 00/45172, WO
00/46594, WO 00/50172, WO 00/50642, WO 00/58719, WO 00/60108, WO
00/70080, WO 00/70353, WO 00/72016, WO 00/73799, WO 00/78454, WO
01/02850, WO 01/14865, WO 01/17797, and WO 01/27253.
[0092] In preferred aspects, the body structure of the microfluidic
devices incorporates a planar or "chip" structure. The devices
described herein typically comprise an aggregation of two or more
separate layers which when appropriately mated or joined together,
form the body structure of the microfluidic device of the
invention, e.g., containing the channels and/or chambers described
herein. Typically, the microfluidic devices described herein will
comprise a top portion, a bottom portion, and an interior portion,
wherein the interior portion substantially defines the channels and
chambers of the device. See, e.g., FIG. 1.
[0093] A variety of substrate materials are optionally employed as
the bottom portion. Typically, because the devices are
microfabricated, substrate materials will be selected based upon
their compatibility with known microfabrication techniques, e.g.,
photolithography, wet chemical etching, laser ablation, reactive
ion etching (RIE), air abrasion techniques, injection molding, LIGA
methods, metal electroforming, embossing, and other techniques.
Suitable substrate materials are also generally selected for their
compatibility with the full range of conditions to which the
microfluidic devices may be exposed, including extremes of pH,
temperature, salt concentration, and application of electric
fields. Accordingly, in some preferred aspects, the substrate
material may include materials normally associated with the
semiconductor industry in which such microfabrication techniques
are regularly employed, including, e.g., silica based substrates,
such as glass, quartz, silicon or polysilicon, as well as other
substrate materials, such as gallium arsenide and the like. In the
case of semiconductive materials, it will often be desirable to
provide an insulating coating or layer, e.g., silicon oxide, over
the substrate material, and particularly in those applications
where electric fields are to be applied to the device or its
contents. In preferred aspects, the substrates used to fabricate
the body structure are silica-based, and more preferably glass or
quartz, due to their inertness to the conditions described above,
as well as the ease with which they are microfabricated. When
manifold components are fabricated from these materials and/or
using these techniques, many of these considerations are equally
applicable.
[0094] In alternate preferred aspects, especially with respect to
manifold component layers (discussed above), the substrate
materials comprise polymeric materials, e.g., plastics, such as
polymethylmethacrylate (PMMA), polycarbonate,
polytetrafluoroethylene (TEFLON.TM.), polyvinylchloride (PVC),
polydimethylsiloxane (PDMS), polysulfone, polystyrene,
polymethylpentene, polypropylene, polyethylene, polyvinylidine
fluoride, acrylonitrile-butadiene-styrene copolymer (ABS), and the
like. Such polymeric substrates are readily manufactured using
available microfabrication techniques, as described above, or from
microfabricated masters, using well known molding techniques, such
as injection molding, embossing or stamping, or by polymerizing the
polymeric precursor material within the mold (see U.S. Pat. No.
5,512,131). Again, such polymeric substrate materials are preferred
for their ease of manufacture, low cost and disposability, as well
as their general inertness to most extreme reaction conditions.
Again, these polymeric materials may include treated surfaces,
e.g., derivatized or coated surfaces, to enhance their utility in
the microfluidic system, e.g., provide enhanced fluid direction,
e.g., as described in U.S. Pat. No. 5,885,470, and which is
incorporated herein by reference in its entirety for all
purposes.
[0095] In the embodiment shown in FIG. 1, upper layer 102 of body
structure 100, includes plurality of ports 106 disposed through it.
As indicated, these ports are positioned to communicate with
specific points of the channels or grooves 110, e.g., the termini,
in the aggregate body structure when the upper and lower layers are
mated. Ports 106 function to provide fluid access to the channels
of the device, e.g., interfacing with manifold channel termini
and/or apertures, and in certain aspects, electrical access to the
channels within the body structure (e.g., when bulk viscosity
enhancers and electrolytes are disposed within manifold structures
for the delivery of electrical fields to selected ports, etc.). As
discussed further above, rings are optionally molded around (i.e.,
surround) one or more of the plurality of ports on the upper
surface of the upper layer of the body structure. Additionally, at
least a portion of the ports also optionally includes a conductive
coating so that electrical communication is optionally achieved in
the device without placing electrodes directly into, e.g., the
ports. The use of conductive coatings is also described further
above.
[0096] In many embodiments, the microfluidic devices include an
optical detection window disposed across one or more channels
and/or chambers of the device. Optical detection windows are
typically transparent such that they are capable of transmitting an
optical signal from the channel/chamber over which they are
disposed. Optical detection windows may merely be a region of a
transparent layer of the body structure, e.g., where the layer is
glass or quartz, or a transparent polymer material, e.g., PMMA,
polycarbonate, etc. Alternatively, where opaque substrates are used
in manufacturing the devices, transparent detection windows
fabricated from the above materials may be separately manufactured
into the device.
[0097] Microfluidic devices may be used in a variety of
applications, including, e.g., the performance of high throughput
screening assays in drug discovery, immunoassays, diagnostics,
genetic analysis, and the like. As such, the devices described
herein, will often include multiple sample introduction ports or
reservoirs, for the parallel or serial introduction and analysis of
multiple samples, e.g., using the manifolds described herein. These
devices are also optionally coupled to a sample introduction port,
e.g., a pipettor, which serially introduces multiple samples into
the device for analysis. Examples of such sample introduction
systems and other high throughput configurations are described in,
e.g., U.S. Pat. Nos. 6,046,056 and 5,880,071, each of which is
hereby incorporated by reference in its entirety for all purposes.
As discussed above, the invention also includes methods and devices
that utilize membranes for sieving aggregations of material (e.g.,
clumps of cells, reagents, or other particles) and otherwise
delivering reagents or other materials into the ports of the
devices.
Flow of Reagents in Manifolds and Microscale Systems
[0098] The microfluidic devices of the invention optionally include
flowing a fluid in the manifold channels, apertures, microchannel
networks, or other device cavities using various fluid direction
components that optionally include, e.g., a fluid pressure force
modulator, an electrokinetic force modulator, a capillary force
modulator, a gravity force modulator, a magnetic force modulator, a
dielectrophoretic force modulator, a fluid wicking element, or the
like. The fluid direction components used to induce fluid movement
in manifolds and underlying microfluidic device body structures are
optionally the same or different. These as well as other fluid
movement techniques that are optionally adapted to the devices
disclosed herein are described in greater detail in the references
cited and incorporated herein.
[0099] In preferred embodiments, fluid is flowed in the manifold
channel network using a first gravity force modulator and in the at
least one microchannel network using alternative fluid direction
components that also optionally include a fluid pressure force
modulator, an electrokinetic force modulator, a capillary force
modulator, a second gravity force modulator, a magnetic force
modulator, a dielectrophoretic force modulator, a fluid wicking
element, or the like. The first and second gravity force modulator
are optionally the same. As mentioned, one advantage of the
invention is that the interface of certain equipment hardware, such
as the various fluid direction components, with existing devices
does not need to be modified to accommodate the use of
manifolds.
[0100] The application of a pressure differential along a channel
(e.g., a manifold channel, a microchannel, or the like) is carried
out by a number of means. For example, in a simple passive aspect,
reagents are loaded into a manifold aperture at a sufficient volume
or depth, such that the reagent sample creates a hydrostatic
pressure differential along the length of, e.g., an intersecting
manifold channel such that flow is induced through the manifold
channel to, e.g., one or more ports disposed in the surface of an
underlying body structure. Typically, the aperture volume is quite
large in comparison to the volume or flow through rate of the
intersecting channel, e.g., 100 .mu.l or larger volume apertures
vs. 10000 .mu.m.sup.2 channel cross-section. As such, over the time
course of the assay, the flow rate of the reagents will remain
substantially constant, as the volume of within the aperture, and
thus, the hydrostatic pressure changes very slowly. Applied
pressure is then optionally readily varied to yield different
reagent flow rates through the manifold channels in the manifold
and, e.g., the microchannels within the body structure. In
screening applications, varying the flow rate of the reagents is
optionally used to vary the incubation time of the reagents. In
particular, by slowing the flow rate along the channel, one can
effectively lengthen the amount of time between introduction of
reagents and detection of a particular effect. Alternatively,
analysis channel lengths (in the body structure), manifold channel
lengths, detection points, or reagent introduction points are
varied in the device fabrication to vary incubation times.
[0101] In many applications, it may be desirable to provide
relatively precise control of the flow rate of reagents, e.g., to
precisely control incubation or separation times, etc. As such, in
many preferred aspects, flow systems that are more active than
hydrostatic pressure driven systems are employed. For example,
reagents are optionally flowed by applying a pressure differential
across the length of a manifold channel and/or an analysis channel
in a body structure. For example, a pressure source (positive or
negative) is optionally applied at a manifold aperture to force the
reagents through the manifold channel and into an underlying body
structure. The pressure source is optionally pneumatic, e.g., a
pressurized gas, or a positive displacement mechanism, i.e., a
plunger fitted into an aperture, for forcing the reagents through
the device cavities. Alternatively, a vacuum source is applied to a
manifold aperture at one end of a channel network to draw reagents
from another aperture in fluid communication with an opposite end
of the network. Pressure or vacuum sources are optionally supplied
external to the device or system, e.g., external vacuum or pressure
pumps sealably fitted to the inlet or outlet of a manifold channel
or an a microchannel (e.g., for interchangeable manifold devices),
or they may be internal to the device, e.g., microfabricated pumps
integrated into the device and operably linked to a manifold
channel or a microchannel. Examples of microfabricated pumps have
been widely described in the art. See, e.g., published
International Application No. WO 97/02357.
[0102] In alternate aspects, other flow systems are employed in
transporting reagents through device channels. One example of such
alternate methods employs electrokinetic forces to transport the
reagents. Electrokinetic transport systems typically utilize
electric fields applied along the length of channels (e.g.,
manifold channels, microchannels, or the like) that have a surface
potential or charge associated therewith. When fluid is introduced
into the channel, the charged groups on the inner surface of the
particular channel ionize, creating locally concentrated levels of
ions near the fluid/surface interface. Under an electric field,
this charged sheath migrates toward the cathode or anode (depending
upon whether the sheath comprises positive or negative ions) and
pulls the encompassed fluid along with it, resulting in bulk fluid
flow. This flow of fluid is generally termed electroosmotic flow.
Where the fluid includes reagents, the reagents are also pulled
along. A more detailed description of controlled electrokinetic
material transport systems in microfluidic systems is described in
published International Patent Application No. WO 96/04547, which
is incorporated herein by reference.
[0103] Hydrostatic, wicking and capillary forces are also
optionally used to provide for fluid flow. See, e.g., "Method and
Apparatus for Continuous Liquid Flow in Microscale Channels Using
Pressure Injection, Wicking and Electrokinetic Injection," by
Alajoki et al., U.S. Ser. No. 09/245,627, filed Feb. 5, 1999. In
these methods, an adsorbent material or branched capillary
structure is placed in fluidic contact with a region where pressure
is applied, thereby causing fluid to move towards the adsorbent
material or branched capillary structure.
[0104] While the foregoing invention has been described in some
detail for purposes of clarity and understanding, it will be clear
to one skilled in the art from a reading of this disclosure that
various changes in form and detail can be made without departing
from the true scope of the invention. For example, all the
techniques and apparatus described above may be used in various
combinations. All publications, patents, patent applications, or
other documents cited in this application are incorporated by
reference in their entirety for all purposes to the same extent as
if each individual publication, patent, patent application, or
other document were individually indicated to be incorporated by
reference for all purposes.
* * * * *