U.S. patent application number 09/841145 was filed with the patent office on 2002-10-24 for microfluidic valve with partially restrained element.
Invention is credited to Karp, Christoph D., Maresch, Laird, O'Connor, Stephen D., Pezzuto, Marci.
Application Number | 20020155010 09/841145 |
Document ID | / |
Family ID | 25284140 |
Filed Date | 2002-10-24 |
United States Patent
Application |
20020155010 |
Kind Code |
A1 |
Karp, Christoph D. ; et
al. |
October 24, 2002 |
Microfluidic valve with partially restrained element
Abstract
The invention provides microfluidic devices having valves
disposed therein. The valves can be configured as one-way valves.
The invention also provides microfluidic pumps using two or more
microfluidic valves. The valves can be configured to rest in an
open or closed position. The valves also can be single use valves
or can be multiple use valves. The valves may be further responsive
to actuators, including electromechanical and magnetic
actuators.
Inventors: |
Karp, Christoph D.;
(Pasadena, CA) ; Pezzuto, Marci; (Altadena,
CA) ; Maresch, Laird; (Pasadena, CA) ;
O'Connor, Stephen D.; (Pasadena, CA) |
Correspondence
Address: |
Vincent K. Gustafson
Patent Counsel
Nanostream, Inc.
2275 East Foothill Blvd.
Pasadena
CA
91107
US
|
Family ID: |
25284140 |
Appl. No.: |
09/841145 |
Filed: |
April 24, 2001 |
Current U.S.
Class: |
417/413.2 |
Current CPC
Class: |
F16K 99/0057 20130101;
F04B 43/043 20130101; F16K 2099/008 20130101; B01L 2400/0481
20130101; F16K 99/0001 20130101; F16K 99/003 20130101; B01L
2300/0681 20130101; B01L 2300/0816 20130101; B01L 2400/0638
20130101; F16K 2099/0084 20130101; B01L 3/502738 20130101; F16K
99/0007 20130101; B01L 2400/0622 20130101; B01L 2300/0874 20130101;
B01L 2300/0887 20130101; F16K 2099/0094 20130101; B01L 2400/084
20130101 |
Class at
Publication: |
417/413.2 |
International
Class: |
F04B 017/00 |
Claims
What is claimed is:
1. A microfluidic valve device comprising: a first microfluidic
channel disposed in a first layer, the first microfluidic channel
having an upper surface; a second microfluidic channel in a second
layer, wherein the second microfluidic channel has at least one
dimension smaller than that of the first channel, the second layer
having a sealing surface; and a flap layer disposed between the
first microfluidic channel and the second microfluidic channel, the
flap layer having a movable flap formed therein, wherein the flap
has a closed position sealed against the sealing surface and can
open into the first microfluidic channel.
2. The microfluidic device of claim 1, wherein said layers are
integral.
3. The microfluidic device of claim 1, wherein said layers are
stencil layers.
4. The microfluidic device of claim 3, wherein said stencil layers
are polymeric layers.
5. The microfluidic device of claim 3, wherein said stencil layers
are adhesive tapes.
6. The microfluidic device of claim 1, wherein the movable flap can
contact a second surface of the first layer, wherein such contact
restricts fluid flow within the first channel.
7. The microfluidic device of claim 1, further comprising a fourth
layer adjacent to the flap layer.
8. The microfluidic device of claim 7, wherein the fourth layer is
substantially rigid.
9. The microfluidic device of claim 7, wherein the fourth layer has
an aperture disposed therein, wherein the flap can seal against the
fourth layer adjacent to the aperture.
10. The microfluidic device of claim 1, wherein the flap has a
width that is narrower than the first channel.
11. The microfluidic device of claim 1, wherein the flap is
flexible.
12. The microfluidic device of claim 1, wherein the flap is
substantially rigid.
13. The microfluidic device of claim 12, wherein the flap has a
hinge region.
14. The microfluidic device of claim 13, wherein the hinge region
comprises an area with the flap layer with reduced thickness
relative to the movable portion of the flap region.
15. The microfluidic device of claim 13, wherein the hinge region
is formed from a flexible material.
16. The microfluidic device of claim 1, wherein the flap has an
upper flap surface and a lower flap surface and is adhesively
coated on either said upper or said lower flap surface.
17. The microfluidic device of claim 16, wherein the flap is
adhesively coated on both the upper flap surface and the lower flap
surface.
18. A microfluidic pump comprising: a first microfluidic valve of
claim 1; a second microfluidic valve of claim 1; wherein the first
and the second microfluidic valves are in fluid communication with
a pumping chamber having an adjustable volume.
19. The microfluidic pump of claim 18, wherein the pumping chamber
comprises a cylinder and movable piston assembly.
20. The microfluidic pump of claim 18, further comprising a
deformable membrane forming one surface of the pumping chamber.
21. The microfluidic pump of claim 20, further comprising an
actuator for deforming the deformable membrane.
22. The microfluidic pump of claim 21, wherein the actuator is
electromechanical.
23. The microfluidic pump of claim 22, wherein the
electromechanical actuator is a piezoelectric or titanium nickel
material.
24. The microfluidic pump of claim 20, further comprising a
pressurizable chamber having at least one side formed by the
deformable membrane.
25. The microfluidic pump of claim 24, further comprising a
pressure regulating pump capable of altering pressure within the
pressurizable chamber.
26. The microfluidic device of claim 1, wherein the flap layer
includes a material with magnetic susceptibility, the device
further comprising a magnetic actuator.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to microfluidic devices having
valves therein. The invention also relates to microfluidic
pumps.
BACKGROUND
[0002] Microfluidic devices are becoming more important in a
variety of fields, from biochemical analysis to medical diagnostics
and to fields as diverse as environmental monitoring to chemical
synthesis. There has been a growing interest in the manufacture and
use of microfluidic systems for the acquisition of chemical and
biological information. In particular, microfluidic systems allow
complicated biochemical reactions to be carried out using very
small volumes of liquid. These miniaturized systems increase the
response time of the reactions, minimize sample volume, and lower
reagent cost.
[0003] Traditionally, these microfluidic systems have been
constructed in a planar fashion using silicon fabrication
techniques. Representative systems are described, for example, in
some early work by Manz et al. (Trends in Anal. Chem. (1990) 10(5):
144-149; Advances in Chromatography (1993) 33: 1-66). These
publications describe microfluidic devices constructed using
photolithography to define channels on silicon or glass substrates
and etching techniques to remove material from the substrate to
form the channels. A cover plate is bonded to the top of this
device to provide closure.
[0004] More recently, a number of methods have been developed that
allow microfluidic devices to be constructed from plastic, silicone
or other polymeric materials. In one such method, a negative mold
is first constructed, and plastic or silicone is then poured into
or over the mold. The mold can be constructed using a silicon wafer
(see, e.g., Duffy et al., Analytical Chemistry (1998) 70:
4974-4984; McCormick et al., Analytical Chemistry (1997) 69:
2626-2630), or by building a traditional injection molding cavity
for plastic devices. Some molding facilities have developed
techniques to construct extremely small molds. Components
constructed using a LIGA technique have been developed (see, e.g.,
Schomburg et al., Journal of Micromechanical Microengineering
(1994) 4: 186-191). Other approaches combine LIGA and a
hotembossing technique. Imprinting methods in
polymethylmethacrylate (PMMA) have also been demonstrated (see,
Martynova et al., Analytical Chemistry (1997) 69: 4783-4789).
However, these techniques do not lend themselves to rapid
prototyping and manufacturing flexibility. Additionally, these
techniques are limited to planar structures. Moreover, the tool-up
costs for both of these techniques are quite high and can be
cost-prohibitive.
[0005] Generally, construction of microfluidic devices having
integral pumps and valves is problematic using the traditional
techniques of microfluidic device construction. Rigid silicon
fabrication, for example, does not lend itself to construction of
flexible parts. Often devices containing integrated valves and
pumps are complex and difficult to manufacture. Such devices also
can require several different manufacturing techniques to create
the valve or pump structures. In spite of the limitations in the
current state of the art, there is a clear need in the field of
microfluidic devices for improved valves and pumps.
SUMMARY OF THE INVENTION
[0006] This invention relates to the microfluidic devices that
contain valves for controlling fluid flow. In one aspect of the
present invention, certain sections of microfluidic channels are
partially restrained, that is, not connected at all points. Since
certain sections are not completely held in place, the material in
this area is flexible and can form a microfluidic flap. These flaps
can be used to control the flow of fluid. In certain embodiments,
these flaps can be used as one-way flow controllers. In other
embodiments, these flaps can be used to pump fluids. In still
further embodiments, these flaps can be used to direct fluid among
different levels of a three-dimensional device.
[0007] The invention provides a microfluidic valve device having a
first microfluidic channel disposed in a first layer. The
microfluidic device has a second microfluidic channel in a second
layer with at least one dimension smaller than that of the first
channel. The device has a (third) flap layer disposed between the
first microfluidic channel and the second microfluidic channel, the
third layer having a movable flap formed therein. The flap has a
closed position sealed against a sealing surface formed by the
second layer and can open into the first microfluidic channel. The
flap can have at least one dimension, typically width, that is
smaller than that of the channel into which it is deflected.
[0008] The flap can be formed from a material that is flexible or
substantially rigid. When the flap is substantially rigid, the flap
can have a hinge region. The hinge region can be a portion of the
material that has a reduced thickness relative to the movable
portion of the flap. In another embodiment, the hinge region is
constructed from a different material from the movable portion of
the flap.
[0009] The layers of the device can be integral in the device or
can be assembled from individual stencil layers. The stencil layers
can be any suitable material including polymeric materials. The
stencil layers can be, for example, adhesive tapes.
[0010] The device can be constructed such that the movable flap can
contact one or more surfaces of the first channel, and restrict
fluid flow therein. The microfluidic device also can have a sealing
layer adjacent to the flap layer with holes or apertures disposed
therein to allow fluid communication through the flap region. The
sealing layer can be a substantially rigid material. The sealing
layer also can contain an aperture disposed adjacent to the movable
flap.
[0011] The movable flap can be flexible, substantially rigid, or a
combination of flexible and rigid portions. When the movable flap
is substantially rigid, it can have a hinge region. A hinge region
can be formed from a flexible material. Either the top or bottom or
both surfaces of the movable flap can be adhesively coated.
[0012] The invention also provides microfluidic pumps that have two
or more microfluidic valves of the invention arranged in fluid
communication with a pumping chamber having an adjustable volume.
The pumping chamber can be, for example, a cylinder with a movable
piston for changing the volume. The pumping chamber also can have a
deformable membrane forming one surface of the pumping chamber. The
deformable membrane can be deformed to change the volume of the
pumping chamber. Deformation can be achieved with a mechanical
actuator including, for example, an electromechanical actuator.
Electromechanical actuators include, for example, piezoelectric
materials. The pumping device also can have a pressurizable chamber
that has at least one side formed by the deformable membrane. The
pressure in the pressurizable chamber can be adjusted, for example,
using a pump. Such a pressure change can cause the membrane to be
deformed and thereby operate the pump.
[0013] Definitions
[0014] The term "channel" as used herein is to be interpreted in a
broad sense. Thus, it is not intended to be restricted to elongated
configurations where the transverse or longitudinal dimension
greatly exceeds the diameter or cross-sectional dimension. Rather,
such terms are meant to comprise cavities or tunnels of any desired
shape or configuration through which liquids may be directed. Such
a fluid cavity may, for example, comprise a flow-through cell where
fluid is to be continually passed or, alternatively, a chamber for
holding a specified, discrete amount of fluid for a specified
period of time. "Channels" may be filled or may contain internal
structures comprising valves or equivalent components.
[0015] The term "microfluidic" as used herein is to be understood,
without any restriction thereto, to refer to structures or devices
through which fluid(s) are capable of being passed or directed,
wherein one or more of the dimensions is less than 500 microns.
[0016] The term "microfluidic flap" as used herein is to be
understood, without any restriction thereto, to refer to a portion
of a surface forming a wall of a microfluidic channel that is not
connected at all points to other portions of the structure forming
the channel. A microfluidic flap can have the property that it may
move within said channel when certain physical characteristics of
the channel change, such as pressure, temperature, flow rate of
fluid, type of fluid, etc.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1A shows an exploded view of a microfluidic device
having a microfluidic valve disposed therein. FIG. 1B shows a top
view of the same device assembled. FIG. 1C shows a side view of the
device during operation. The dark arrow shows the direction of
fluid flow. FIG. 1D shows the same side view of the device during
operation with the flow reversed. Again, dark arrows indicate the
direction of fluid flow within the device.
[0018] FIG. 2A shows an exploded view of a microfluidic device
capable of being used to pump fluid. FIG. 2B shows a top view of
the device of FIG. 2A. FIGS. 2C and 2D show cross-sectional views
of the same device in operation. FIG. 2C shows the device with a
negative pressure applied to chamber 111, while FIG. 2D shows the
device with a positive pressure applied to chamber 111.
[0019] FIGS. 3A and 3B show cross-sectional views of a microfluidic
device having a microfluidic diversion valve therein where the flap
portion is usually in the down position. In FIG. 3A, the device is
show in operation with fluid flowing according to the single arrows
through channels 189 and 192. In FIG. 3B, fluid is flowing in the
reverse direction through channels 191 and 189 as indicated by the
single arrows. In both cases, fluid flows through filter region
190.
[0020] FIGS. 3C and 3D show cross-sectional views of a microfluidic
device having a microfluidic diversion valve therein where the
microflap portion is usually in the up position. In FIG. 3C, the
device is show in operation with fluid flowing according to the
single arrows through channels 192 and 189. In FIG. 3D, fluid is
flowing in the reverse direction through channels 191 and 189 as
indicated by the single arrows. In both cases, fluid flows through
filter region 190.
[0021] FIG. 4A shows a top view of a microfluidic device having a
flap valve therein. FIG. 4B shows the same device with the flap
deformed towards channel 220 while FIG. 4C shows the same device
with the flap in the closed position.
[0022] FIG. 5A shows a side view of a microfluidic device having a
flap valve therein, the device subject to no external forces. FIG.
5B shows a side view of the device of FIG. 5A, subject to
application of an external force that deforms the flap valve
upward. FIG. 5C shows a side view of the same flap valve, subject
to application of an external force that deforms the flap valve
downward.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The invention provides microfluidic devices having fluid
control valves disposed therein. In one embodiment, the valve is a
one-way valve or a check valve. The microfluidic valve includes a
first channel formed within a first layer of a microfluidic device
and a second channel formed within a second layer of the
microfluidic device substantially coplanar with the first channel.
A layer disposed between the first and second layers forms a flap
structure. The first channel is smaller than the second channel in
at least one dimension within the plane of the channels such that a
seating surface is formed. A third layer disposed between the first
and second layers has a flap that is movable within the device but
remains attached to the third layer. In a preferred embodiment, the
flap and the third layer are formed from the same material, with
material removed from the third layer to form the flap.
[0024] The flap is movable, such that in a closed position it seals
with the seating surface. As used herein, the term "seals" refers
to contact of a flap against a seating surface. Sealing of a flap
includes both the formation of a fluid-tight junction and junction
that allow restricted fluid flow through the device. Mobility of
the flap can be achieved by any suitable modification of the flap
material or dimensions, including, for example, altering the
material of the flap, the dimensions of the flap (e.g., thickness),
the degree of connection of the flap to the third layer and
combinations thereof. For example, the flap can be formed from a
substantially rigid material, with a hinge region to allow
movement. A hinge region can be formed in a rigid material by
reducing its thickness at the desired hinge region. The flap also
can be formed from a pliable material. A material is suitably
pliable if, at the desired operating pressures of the device, the
material will bend or deform. The degree of pliability will depend
on the nature of the material used and on the thickness of the
material used. A flap can have any shape such that the flap can
deform within the device towards the second channel. In certain
embodiments, the flap will seal against the first channel within
normal operating pressures of the device. In other embodiments, the
flap will seal against the second channel within normal operating
pressure of the device. In one embodiment, a flap has one side
separated from the membrane from which it is formed. In another
embodiment, the flap is formed by cutting three sides of a
rectangle into the membrane material to form a flap with a
substantially rectangular shape.
[0025] The stencil layer or membrane in which the flap resides, the
flap layer, can be made of any suitable material. A suitable
material can be chosen by one of skill in the art, depending on the
type of construction used to make the microfluidic device. For
repeated usage, it is preferred that the material chosen has a
degree of elasticity allowing it to rebound into the seated
position. For example, the material can be a metal foil, paper or
polymer or combinations or laminates thereof. When the device is to
be constructed from layered stencil layers, and the flap is
integral with the flap layer, the flap and flap layer are
preferably fabricated from a polymeric material. Suitable polymeric
materials include, for example, polytetrafluorethylenes,
polystyrenes, polypropylene, polyethylene, polyimides,
polyacrylates, rubbers and silicones. In certain embodiments, one
or both sides of the flap region may be covered or coated with a
material to enhance adhesion to the upper or lower channel surface.
The adhesion materials can be permanent or reversible. In a
preferred embodiment, adhesive materials are coated onto the
surface that is to make up the flap portion prior to the
construction of the device.
[0026] Microfluidic coupling devices have stencil layers and
substrate layers that define channels therein. Such devices can be
constructed from discrete layers of material or can be fabricated
as an integral unit. When a coupling device is constructed as an
integral unit, layers refer only to positions within a device
rather than to individual components. A microfluidic device can be
constructed with stencil layers, using techniques described, for
example, in co-pending U.S. patent application Ser. No. 09/453,029,
incorporated herein by reference in its entirety. When the device
is to be constructed by assembling stencil layers with adhesive
separating the layers or using self-adhesive tape materials, the
material forming the sealing surface and the side of the flap
region interacting with the sealing surface are both preferably
non-adhesive. Alternatively, the area of the flap interacting with
the sealing surface and/or the seating surface can be adhesively
coated, and the adhesive strength can be chosen to prevent
permanently closing the valve. Any suitable adhesive can be used to
assemble a device from stencil layers.
[0027] The material chosen for use as a valve is preferably
substantially impermeable to the fluid to be used in the device. A
device can, however, use a material that is permeable to a fluid.
In one embodiment, the flap layer is formed from a material that is
impermeable to the fluid for which the device is designed, but may
be permeable to a gaseous fluid, such as air.
[0028] In a preferred embodiment, the flap region may be used to
seal a hole or via that goes from one level of the device to
another. In certain embodiments, the flap portion may be more
effective at blocking fluid flow if it covers a hole or via rather
than a channel portion.
[0029] The height of the outlet channel also can be varied to
change the operation of the flap. A large flap relative to the
height of the outlet channel will allow the flap to seal against
the lower surface of the channel into which the flap is deflected.
For example, referring to FIG. 1D, membrane 22 having flap 30
disposed therein opens into channel 26 in layer 23. The thickness
of layer 23 (the height of channel 26) and the length of the flap
30 can be varied such that the deflected flap may or may not come
in contact with the lower surface of layer 24.
[0030] Referring to FIG. 1, a microfluidic device is constructed
from five stencil layers 20-24 that have channels 25, 26, vias 27,
and inlet/outlet ports 28, 29. Additionally, one section 30 of
layer 22 is cut so that the region is still attached to the stencil
layer but can move freely. The resulting flap 31 is only partially
restrained from moving. The completed device is shown in FIG. 1B
and the region where the flap 31 is in contact with the upper
sealing surface of layer 21 is shown. A cross section of region 31
is blown up in FIGS. 1C and D. Two possible uses are shown. In FIG.
1C, fluid is injected at the entry port 29. The fluid passes
through channel 26 until it reaches the flap valve region 31. Here,
the flap region 30 is pushed down against the sealing surface of
stencil layer 21. Thus, the flap region 30 prevents fluid flow from
channel 26 into channel 25. In operation, the fluid may never reach
the region at flap 30, since the fluid will compress the air within
channel 26 and build up pressure which may prevent the fluid from
flowing at all. In operation in the reverse direction, when fluid
is injected at port 28, it passes through the vias 27 and through
channel 25. When the fluid now encounters the flap portion 30, the
flap is free to be displaced upwards since the area above it is
open channel 26. The fluid passes through this region, into channel
26 and can exit through port 29.
[0031] Also provided is a microfluidic pump having a first inlet
channel, a first microfluidic one-way valve, with a first flap
opening into a chamber in fluid communication with the first inlet
channel, and an outlet channel in fluid communication with the
chamber through the second microfluidic check valve. The second
one-way valve has a second flap opening into the second channel.
The volume of the pumping chamber can be altered. In one
embodiment, the pumping chamber is a cylinder with a piston
assembly. In another embodiment, the pumping chamber has a
deformable membrane forming one side of the chamber. Deformation of
the deformable membrane can result in movement of the deformable
membrane. The deformable membrane can be moved by mechanical force.
For example, the membrane can be deformed using a mechanical
actuator. In one embodiment, the mechanical actuator is a piston.
In another embodiment, the mechanical actuator is an
electromechanical material, for example, a piezoelectric device of
a Ti--Ni device. In another embodiment, the material can be a
magnetic material and a magnetic field can be fluctuated to force
the membrane up and down. In another embodiment, the material can
be driven up and down using a camshaft that is asymmetrical. In
another embodiment, force to deform the membrane is supplied by
having an additional chamber opposite the pumping chamber, the
pressure of which can be varied, for example, by a pressure pump or
a vacuum pump. In another embodiment, the temperature of the
chamber 111 can be cycled up and down to force movement of the
membrane.
[0032] Referring to FIG. 2A, a microfluidic pumping system was
constructed from nine stencil layers 100-108 that had channels
109-111, through regions 112, inlet outlet holes 113,114 and a
pressure entrance 115 removed. Additionally, two flap regions
116,117 we partially cut in stencil layer 103. The assembled device
is shown in FIG. 2B. The cross section of pumping area 118 is shown
in FIGS. 2C and D. In use, the pumped worked as follows. Fluid was
injected at port 114 and filled both channels 109 and 110 and
chamber 119. An external pressure/vacuum source was hooked up to
the inlet port 115. When the external source applied a slight
vacuum to channel 111, the stencil layer 106 flexes up towards the
channel 111. This creates a slight negative pressure in chamber 119
directly below the stencil 106. In order to adjust for this, flap
117 is lifted up towards the negative pressure and fluid flows into
chamber 119. Flap 116 does not open since it is blocked by the
lower surface of stencil layer 104 above. Once the chamber
equilibrates (or prior to equilibration), the pressure on the
external source at 115 was reversed. Referring to FIG. 3D, the
positive pressure within channel 111 causes the stencil layer 106
to push down into the chamber, increasing the pressure. In order to
adjust to the new pressure, flap 116 opens towards channel 110 and
pushes fluid into outlet channel 110. When the pressure at the
inlet 115 oscillates up and down, a net fluid flow from channel 109
to 110 occurs. This pumping mechanism can be used to push fluid
throughout additional channels within the microfluidic structure,
or to push fluid off board. The pumping speed and amount can be
altered in a number of ways. The size of the pressure change at the
input 115 as well as the period of the oscillation can have an
effect. The geometry and size of the channels themselves can also
alter the pumping parameters. For example, the size of the flaps
will determine the amount of fluid transferred per stroke.
Alternatively, the size of the chamber just below the stencil layer
106 can also be altered to change the parameters. Likewise, the
material used to construct deformable membrane 106 will determine
the change in volume of pumping chamber 119, as will the
composition of the fluid itself.
[0033] Fluid control valves of the invention also can be used to
direct fluid flow among layers of a microfluidic device. These
valves can be incorporated into a system in such as way that a
particular microfluidic device can perform a variety of functions
depending on how the chip is used. Additionally, channels within a
particular device can be used more than once for different
functions when using these valves.
[0034] Microfluidic devices of the invention also can have filter
materials embedded within the channels. A filter is any material
that partially blocks or selectively alters fluid flow within a
channel. A filter is typically a porous material. The material also
can have surface chemical properties that alter its interaction
with various fluids to be used in the device.
[0035] Two similar configurations of the present invention that
perform in two distinct manners are shown in FIGS. 3A-D. These
figures are of the cross-section of a portion of a complete device
having valve structures. In this particular embodiment, the devices
contain filter material for performing ultra-filtration of
biological or chemical molecules. Referring to FIG. 3A, a device is
shown with an input channel 189 for loading a biological sample.
Fluid injected into channel 189 from the left will encounter filter
material 187. When fluid is injected, it goes across the filter
area at 190 and into the region above. In this application, the
filter is chosen so the biological targets within the sample of
choice will become stuck at the lower surface of the filter 187 at
region 190. In certain embodiments, the filter can be chosen so
that large nucleic acid targets will be blocked at the entrance of
the filter and other non-specific biomass will proceed. The stencil
layer 182 in this device is composed of a flexible material so that
the flap valve 188 rests on the lower stencil surface 184 in the
normal position. Additionally, semi-permanent adhesive material is
used on the lower surface of the flap portion 193 and/or the upper
surface of the lower stencil 184. In the normal position, channel
191 is blocked and the fluid is diverted into the upper channel
192. Once the sample is fully injected and the filter material
washed, extraction fluid is injected into channel 191. Referring to
FIG. 3B, the pressure from the fluid being injected at 191 pushed
the moveable flap 188 up into a closed position against stencil
layer 181. The fluid passes down through the filter and pushes the
nucleic acid off the filter and into the solution. The sample then
passes down 189 to an exit port or another portion of the device
for further analysis.
[0036] Another device configuration is shown in FIG. 3C. In this
example, the stencil layer 182 is composed of a material such that
flap region 188 is normally in the closed position as shown in FIG.
3D. In use, the sample is loaded through 192 and passes through the
filter region. The nucleic acid material in this example is stuck
on the top surface of the filter area 190. Once the wash buffer has
been passed across the filter, elution buffer can be added in the
reverse direction (see FIG. 3D) and be directed to the exit channel
191. Other configurations are possible, as are other types of
sample materials and filters.
[0037] Another embodiment of the present invention is shown in
FIGS. 4A-C. In this embodiment, a separate control channel is used
to alter the fluid being pumped. Referring to FIG. 4A, a
microfluidic device is shown from the top view with a flow channel
221 and control channel 220. Also shown are a via 227 formed in the
sealing layer 224 and a flap region 226 that form the valve
adjacent to central layer 223. Cross sectional views of the valve
region are shown in FIGS. 4B and 4C. In use, if no pressure is
applied to control channel 220, fluid flows through channel 221,
reaches the valve region and the pressure of the flow opens the
flap valve 226 that covers the via 227. A portion of the fluid then
passes into the upper channel 220 as well as the flow channel 221.
In an alternative use, pressure is applied to the control channel
220 during use. If the pressure in control channel 220 is higher
than the pressure in flow channel 221, the flap 226 completely
covers the via 227 and all of the fluid flows down channel 221. The
pressure in channel 220 can be adjusted as desired to produce a
pseudo flow regulator in 221. If the flap is partially open, then
only a smaller portion of fluid will flow up into 220. In a similar
manner, channel 220 could be used as the flow channel and channel
221 as the control channel. In this embodiment, all of the fluid
would remain in channel 220 and the movement of the flap region 226
would act as a flow constrictor.
[0038] A further embodiment of the present invention is shown in
FIGS. 5A-C. In this embodiment, the flap 88 is composed in whole or
in part of a material with magnetic susceptibility, such as a
ferromagnetic, paramagnetic, or diamagnetic material. The device
further includes an magnetic actuator (not shown), preferably
external to the device, for deforming and therefore controlling the
position of the flap 88. Referring to FIG. 5A, a microfluidic
device is shown from a side view with a no magnetic field is
applied to the device, and the flap 88 is shown from side view with
an first channel 85 and second and third channels 86, 87 defined
between outer layers 80, 84. Inner boundary layers 81, 83 assist
with directing the flow when the flap 88 is deflected from a
substantially linear position aligned with central layer 82, such
as shown in FIG. 5B. In FIG. 5B, an external magnetic force is
applied to the flap 88 in the direction of the dark arrow (upward)
using a magnetic actuator (not shown). This upward force causes the
flap 88 to deflect, either just a small amount or sufficiently to
contact the outer layer 84. In the situation where fluid is flowing
from channel 85 and being split into both channels 86, 87, a small
deflection in the valve may alter the flow characteristics of the
liquid in the channels 86, 87. If sufficient force is applied, the
flap 88 may deflect sufficiently to divert all the flow into
channel 86. FIG. 5C is substantially the same as FIG. 5B, but the
direction of the magnetic force, represented by the dark arrow, is
reversed (downward). In this manner, a microfluidic device
responsive to the application of magnetic force may be constructed
to control the flow of liquid.
[0039] The particular devices and construction methods illustrated
and described herein are provided by way of example only, and are
not intended to limit the scope of the invention. The scope of the
invention should be restricted only in accordance with the appended
claims and their equivalents.
* * * * *