U.S. patent application number 10/115320 was filed with the patent office on 2002-10-31 for microfluidic sedimentation.
Invention is credited to Battrell, C. Frederick, Hayenga, Jon W., Klein, Gerald L., Morris, Christopher J., Saltsman, Patrick, Weigl, Bernhard H..
Application Number | 20020160518 10/115320 |
Document ID | / |
Family ID | 23076003 |
Filed Date | 2002-10-31 |
United States Patent
Application |
20020160518 |
Kind Code |
A1 |
Hayenga, Jon W. ; et
al. |
October 31, 2002 |
Microfluidic sedimentation
Abstract
A device for promoting sedimentation within microfluidic
channels which uses gravity to separate particles from fluid.
Particles such as blood cells or beads are separated from a carrier
fluid using gravity combined with various devices such as membranes
and sonic energy in different embodiments.
Inventors: |
Hayenga, Jon W.; (Redmond,
WA) ; Battrell, C. Frederick; (Redmond, WA) ;
Weigl, Bernhard H.; (Seattle, WA) ; Morris,
Christopher J.; (Redmond, WA) ; Saltsman,
Patrick; (Seattle, WA) ; Klein, Gerald L.;
(Edmonds, WA) |
Correspondence
Address: |
JERROLD J. LITZINGER
SENTRON MEDICAL, INC.
4445 LAKE FOREST DR.
SUITE 600
CINCINNATI
OH
45242
US
|
Family ID: |
23076003 |
Appl. No.: |
10/115320 |
Filed: |
April 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60281114 |
Apr 3, 2001 |
|
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|
Current U.S.
Class: |
436/70 ; 422/400;
422/68.1; 436/177; 436/180 |
Current CPC
Class: |
B01L 2300/0829 20130101;
B01L 2200/0668 20130101; B01L 2400/084 20130101; F16K 99/0001
20130101; B01L 3/502707 20130101; B01D 21/283 20130101; B01L
2200/027 20130101; B01L 2400/0457 20130101; B01L 2300/0861
20130101; G01N 15/05 20130101; B01L 3/502753 20130101; G01N 15/0255
20130101; B01L 2200/0636 20130101; G01N 2015/1411 20130101; B01L
2200/028 20130101; B01L 2200/0647 20130101; F16K 99/0015 20130101;
F16K 2099/008 20130101; F16K 99/0025 20130101; Y10T 436/25375
20150115; B01D 21/0012 20130101; G01N 2035/00247 20130101; B01L
2400/0436 20130101; A61M 2206/11 20130101; G01N 2015/0288 20130101;
B01L 2300/0874 20130101; B01L 3/502776 20130101; B01L 2400/0406
20130101; F16K 99/0059 20130101; G01N 2001/4061 20130101; G01N
2015/1413 20130101; Y10T 436/2575 20150115; B01L 3/502746 20130101;
B01L 2300/0883 20130101; B01L 3/50273 20130101; B01L 2400/0487
20130101; G01N 2001/4016 20130101; B01L 3/5027 20130101; G01N
2015/1486 20130101; F16K 2099/0084 20130101; G01N 15/1456 20130101;
G01N 2001/4094 20130101; F16K 7/17 20130101; G01N 2015/144
20130101; B01L 3/502738 20130101; A61M 1/14 20130101; B01L 3/502761
20130101 |
Class at
Publication: |
436/70 ; 436/177;
436/180; 422/68.1; 422/100; 422/101 |
International
Class: |
G01N 033/86; G01N
001/18 |
Claims
What is claimed is:
1. A microfluidic device comprising: a microfluidic structure
having an inlet and a sedimentation region; a fluid containing
particles having a density different from that of said fluid; and
means for moving said fluid through said inlet into said
sedimentation region such that a concentration gradient of said
particle is established across the vertical dimension of said
sedimentation region.
2. A microfluidic device, comprising: a microfluidic channel having
a depth and a width, and an inlet and a first and a second outlet,
with first outlet placed higher than said second outlet with
respect to the vertical axis of said microfluidic channel; and a
fluid containing particles that have a different density from the
fluid flowing through said channel such that said particles exit
said channel preferentially through said first or said second
outlet.
3. A microfluidic device, comprising: a first channel and a second
channel; means for preventing solid material from moving from said
first channel to said second channel, said means being located
between said first channel and said second channel to form a
collection of solid particles located in said first channel; and
means for moving a fluid through said first and said second channel
such that said fluid interacts with said particles located in said
first channel.
4. The device of claim 3, where said fluid comprises first and
second components, one of which having a higher affinity to said
solid material than the other.
5. The device of claim 4, further comprising a means for detecting
said first and second components located downstream from said means
for preventing solid material from moving from said first channel
to said second channel.
6. The device of claim 4, also having a means for collecting said
first and second components located downstream from said means for
preventing solid material from moving from said first channel to
said second channel.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit from U.S. Provisional Patent
Application Serial No. 60/281,114, filed Apr. 3, 2001, which
application is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to microfluidic devices for
performing analytic testing, and, in particular, to devices for
rapidly increasing sedimentation within microfluidic channels.
[0004] 2. Description of the Related Art
[0005] Microfluidic devices have recently become popular for
performing analytic testing. Using tools developed by the
semiconductor industry to miniaturize electronics, it has become
possible to fabricate intricate fluid systems which can be
inexpensively means produced. Systems have been developed to
perform a variety of analytical techniques for the acquisition of
information for the medical field.
[0006] Microfluidic devices may be constructed in a multi-layer
laminated structure where each layer has channels and structures
fabricated from a laminate material to form microscale voids or
channels where fluids flow. A microscale channel is generally
defined as a fluid passage which has at least one internal
cross-sectional dimension that is less than 500 .mu.m and typically
between about 0.1 .mu.m and about 500 .mu.m. The control and
pumping of fluids through these channels is affected by either
external pressurized fluid forced into the laminate, or by
structures located within the laminate.
[0007] U.S. Pat. No. 5,716,852 teaches a method for analyzing the
presence and concentration of small particles in a flow cell using
diffusion principles. This patent, the disclosure of which is
incorporated herein by reference, discloses a channel cell system
for detecting the presence of analyte particles in a sample stream
using a laminar flow channel having at least two inlet means which
provide an indicator stream and a sample stream, where the laminar
flow channel has a depth sufficiently small to allow laminar flow
of the streams and length sufficient to allow diffusion of
particles of the analyte into the indicator stream to form a
detection area, and having an outlet out of the channel to form a
single mixed stream. This device, which is known at a T-Sensor, may
contain an external detecting means for detecting changes in the
indicator stream. This detecting means may be provided by any means
known in the art, including optical means such as optical
spectroscopy, or absorption spectroscopy of fluorescence.
[0008] U.S. Pat. No. 5,932,100, which patent is also incorporated
herein by reference, teaches another method for analyzing particles
within microfluidic channels using diffusion principles. A mixture
of particles suspended in a sample stream enters an extraction
channel from one upper arm of a structure, which comprises
microchannels in the shape of an "H". An extraction stream (a
dilution stream) enters from the lower arm on the same side of the
extraction channel and due to the size of the microfluidic
extraction channel, the flow is laminar and the streams do not mix.
The sample stream exits as a by-product stream at the upper arm at
the end of the extraction channel, while the extraction stream
exits as a product stream at the lower arm. While the streams are
in parallel laminar flow is in the extraction channel, particles
having a greater diffusion coefficient (smaller particles such as
albumin, sugars, and small ions) have time to diffuse into the
extraction stream, while the larger particles (blood cells) remain
in the sample stream. Particles in the exiting extraction stream
(now called the product stream) may be analyzed without
interference from the larger particles. This microfluidic
structure, commonly known as an "H-Filter," can be used for
extracting desired particles from a sample stream containing those
particles.
[0009] It is often desirable to remove particles from a liquid for
analysis purposes. One method of performing this procedure is to
use a centrifuge. Centrifugation is a process by which particles in
suspension in a fluid are separated by spinning the fluid, usually
in a test tube, such that centrifugal force throws the particles to
the periphery of the rotated vessel. Sedimentation is also an
important method to separate particles by density. In many cases,
the difference in the rate of sedimentation of particles to be
separated is very small, as is the rate of separation itself.
Frequently, small particles such as blood cells sediment at a rate
of only a few micrometers per second. This problem is usually
solved by increasing the apparent gravitational force that drives
the sedimentation by using a centrifuge.
[0010] In microfluidic structures, sedimentation structures can be
used to achieve sedimentation without the use of centrifuges. The
rate of sedimentation of a few micrometers/second provides a
sufficient speed in channels that have dimensions in the order of
hundreds of micrometers. For example, blood cells will settle in a
channel of 100 micrometer depth in about 100 seconds at standard
gravity.
SUMMARY OF THE INVENTION
[0011] It is therefore an object of the present invention to
provide a device which will allow sedimentation in microfluidic
channels.
[0012] It is a further object of the present invention to provide a
device using microfluidic channels to separate blood cells from
plasma.
[0013] It is still a further object of the present invention to
provide a microfluidic sedimentation device which is simple and
easy to use.
[0014] These and other objects of the present invention will be
more readily apparent in the description and drawings which
follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a side view of a sedimentation device according to
the present invention;
[0016] FIG. 2 is a side view of an alternative embodiment of the
device of FIG. 1;
[0017] FIG. 3 is another embodiment of a sedimentation device
according to the present invention;
[0018] FIG. 4 is a side view of a microfluidic channel having a
second channel passing beneath for use in the present
invention;
[0019] FIG. 5 is a bottom view of the device of FIG. 4;
[0020] FIG. 6 is another embodiment for carrying out the present
invention;
[0021] FIGS. 7A-I show several different embodiments of a device
for capturing beads for use in the present invention; and
[0022] FIG. 8 is a plan view of an analysis card according to the
principles of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] FIG. 1 shows a microfluidic device used for promoting
sedimentation. Referring now to FIG. 1, a microfluidic channel 10
is filled with whole blood. An audio speaker 12 is positioned below
channel 10. Speaker 10 is then activated, subjecting channel 10 to
sonic energy, vibrating blood cells 14 within the whole blood
sample. This vibration is sufficient to exceed the minimum shear
stress in the fluid surrounding cells 14, allowing motion of cells
14 in response to gravity. After sufficient time for sedimentation,
a pusher fluid is used to flush the plasma from above and around
settled cells 14 by passing it through channel 10 in the direction
of arrows A. This technique is insensitive to channel geometry
except for a requirement that the height of channel 10 be small
enough that sedimentation occurs rapidly. Although this device is
shown as a sedimentation device for blood cells, it could also be
used to isolate beads within a channel to be used for analysis
purposes.
[0024] An alternative structure for the device of FIG. 1 is shown
in FIG. 2. In this embodiment, channel 10 is saturated at an angle
above the horizontal plane. Whole blood is loaded into channel 10
and speaker 12 activated to subject the sample to sonic energy.
Blood cells 14 settle along the bottom of channel 10, and as
channel 10 is angled, cells 14 tend to move along the bottom
surface of channel 10 in the direction of arrows B. As a pusher
fluid is injected into channel 10, plasma from the blood sample
travels in the direction of arrows C, which is in the opposite
direction of the movement of cells 14. The speed of sedimentation
can be varied by varying the angle of inclination of channel
10.
[0025] Another embodiment which can be used for promoting
sedimentation is shown in FIG. 3. A sample fluid containing
particles 28 which are denser than the sample fluid is inputted
into a microfluidic channel 30. Channel 30 contains a recessed well
section 32 on the bottom surface of channel 30. As particles 28
flow along within channel 30, they drop down into section 32 of
channel 30, as they are denser than the fluid. As a result, a
particle-free sample passes out of channel 30 as shown at arrow
D.
[0026] Another embodiment of the principles of this invention is
shown in FIGS. 4 and 5. Referring now to FIG. 4, a main
microfluidic channel 40 is shown having a circuitous or S-shaped
channel 42 coupled to the bottom surface and is open to channel 40
in periodic locations along channel 40 as can be clearly seen in
FIG. 5. In addition, a filter or membrane 44 is situated on the
bottom surface of channel 40. A diluted fluid containing particles
46 flows into channel 40 at 48. Particles 46 tend to move slightly
away from the walls of channel 40 to avoid the shear gradient that
is present in that area. Membrane 44, which is fluid permeable,
excludes particles 46 from entering into channel 42; however, when
channel 42 is held at a lower absolute pressure than main channel
40, a small portion of the fluid will flow through membrane 44 into
channel 42 at each intersection. This clear fluid flowing within
channel 42 may be collected at the end of channel 42, while the
particle 46 suspension within channel 40 becomes more concentrated
as it moves through main channel 40. This structure may be used for
the extraction of undiluted plasma from whole blood.
[0027] Another structure which may be used to separate plasma from
whole blood is shown in FIG. 6. Referring now to FIG. 6, a
microfluidic channel 60 is shown. The inner walls 62 of channel 60
contain a chemical that initiates aggregation of blood cells into
dense formations called rouleaux. A sample of whole blood flows
into channel 60 at 64, and blood cells 66 react with the chemical
on walls 62 and begin to aggregate. After a sufficient amount of
time has passed, a pusher fluid enters channel 60 at 64, and flows
through aggregated cells 66 to flush the plasma from between the
rouleaux and out of channel 60 at 68.
[0028] FIGS. 7A-I represent different embodiments in which beads
may be trapped within a microfluidic channel to assist in analyzing
a particular fluid. Referring now to FIG. 7A, there is shown a
microfluidic channel 80 through which a plurality of beads 82 are
transmitted. Beads 82 are preferably functionalized with antibodies
such that the beads will fluoresce upon contact with a specific
substance. A membrane or filter 84 is located within channel 80
such that beads will not pass through channel 80, but a fluid can
flow across beads 82 for analysis purposes and flow out through
opening 84. Other means for capturing beads 82 are also shown in
the figures; channel 80 may have a narrow section 90 which will
restrict passage of beads 82 (FIG. 7B); beads 82 may be denser that
the fluid flowing in channel such that they will settle on the
bottom surface 92 of channel 80 due to gravity (FIG. 7C); beads 80
may have magnetic properties such that their travel within channel
80 is stopped using a magnet 94 located outside channel 80 (FIG.
7D); channel 80 may have an inlet 96 in which beads 82 are inserted
into a wide section 98 of channel 80 whereas beads 82 cannot pass
into channel 80 from section 98 (FIG. 7E); beads 82 may be less
dense than the fluid flowing in channel 80 such that they would
settle into a section 100 on the upper surface of channel 80 and
remain in section 100 (FIG. 7F); channel 80 may have a section 102
which is above the level of channel 80 wherein beads 82 which are
less dense than the fluid in channel 80 such that they will be
trapped in section 102 (FIG. 7G); channel 80 may have a recessed
section 104 wherein beads 82 which are more dense than the fluid
will settle in section 104 (FIG. 7H); and channel 80 may have a
downwardly depending section 106 such that beads 82 which are more
dense than the fluid remain in section 106 (FIG. 7I). In all of
these embodiments, beads 82 will react of a specific substance
within the fluid such that they will fluoresce to indicate a
particular concentration of that substance.
[0029] FIG. 8 shows a laminate analysis card 120 which also
embodies the principles of the present invention. Card 120 has a
first input 122 into which a solution of beads that are
functionalized with antibodies is injected, a second input 124 into
which a sample such as whole blood is injected, and a third input
126 into which a wash solution is injected. Input 122 is coupled
through a channel 128 to a junction 130, input 124 is coupled to
junction 130 through a channel 132, and input 126 is coupled to
junction 130 through a channel 134.
[0030] Junction 130 is connected to a channel 140 having a series
of recessed well-like structures 141 similar to well 32 shown in
FIG. 3. The output of channel 140 is coupled to a reservoir 142
through a channel 144.
[0031] The operation of analysis card 120 is as follows: a bead
solution is injected into input 122, a whole blood sample into
inlet 124, and a wash solution into inlet 126. Bead solution is
first pumped into channel 140 through a valve 150, and the beads in
the solution settle into well structures 141. Then the blood sample
is pumped into channel 140 through a valve 152, where the blood
analytes interact with the antibodies on the beads in wells 141.
Finally, the wash solution is pumped through a valve 154 through
channel 140 to wash the blood away. The beads in wells 141 will
change color or fluoresce to indicate the presence or concentration
of the desired substance in the blood.
[0032] While the present invention has been shown and described in
terms of a preferred embodiment thereof, it will be understood that
this invention is not limited to this particular embodiment and
that changes and medications may be made without departing from the
true spirit and scope of the invention as defined in the appended
claims.
* * * * *