U.S. patent application number 10/114864 was filed with the patent office on 2002-10-17 for surface tension reduction channel.
Invention is credited to Weigl, Bernhard H..
Application Number | 20020150502 10/114864 |
Document ID | / |
Family ID | 23076003 |
Filed Date | 2002-10-17 |
United States Patent
Application |
20020150502 |
Kind Code |
A1 |
Weigl, Bernhard H. |
October 17, 2002 |
Surface tension reduction channel
Abstract
A structure for use with a microfluidic channel to reduce the
effects of surface tension and capillary forces. A macroscale
reservoir is connected to a microscale channel by a microscale
section extending from the reservoir, which fills with fluid and
flows smoothly into the microscale channel.
Inventors: |
Weigl, Bernhard H.;
(Seattle, WA) |
Correspondence
Address: |
JERROLD J. LITZINGER
SENTRON MEDICAL, INC.
4445 LAKE FOREST DR.
SUITE 600
CINCINNATI
OH
45242
US
|
Family ID: |
23076003 |
Appl. No.: |
10/114864 |
Filed: |
April 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60281114 |
Apr 3, 2001 |
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Current U.S.
Class: |
422/400 ;
422/68.1 |
Current CPC
Class: |
B01L 3/50273 20130101;
F16K 2099/008 20130101; F16K 99/0059 20130101; F16K 2099/0084
20130101; A61M 2206/11 20130101; B01L 3/502753 20130101; B01L
2400/0406 20130101; G01N 2015/0288 20130101; A61M 1/14 20130101;
B01L 3/5027 20130101; G01N 2015/1486 20130101; B01L 3/502776
20130101; B01L 2200/0647 20130101; G01N 2001/4061 20130101; F16K
7/17 20130101; B01L 2400/0487 20130101; B01L 2200/027 20130101;
F16K 99/0001 20130101; B01L 2300/0874 20130101; B01L 3/502761
20130101; G01N 2015/1413 20130101; B01L 3/502707 20130101; F16K
99/0025 20130101; B01L 2400/084 20130101; Y10T 436/2575 20150115;
B01L 3/502738 20130101; B01D 21/0012 20130101; B01L 2200/028
20130101; B01L 2400/0436 20130101; G01N 15/1456 20130101; G01N
2001/4094 20130101; G01N 2035/00247 20130101; B01L 2200/0668
20130101; B01L 2300/0829 20130101; B01L 2300/0883 20130101; B01L
2400/0457 20130101; G01N 15/05 20130101; G01N 15/0255 20130101;
B01L 3/502746 20130101; G01N 2001/4016 20130101; B01L 2300/0861
20130101; F16K 99/0015 20130101; B01D 21/283 20130101; Y10T
436/25375 20150115; B01L 2200/0636 20130101; G01N 2015/1411
20130101; G01N 2015/144 20130101 |
Class at
Publication: |
422/58 ; 422/55;
422/68.1 |
International
Class: |
G01N 021/05 |
Claims
What is claimed is:
1. A microfluidic device, comprising: a first fluid vessel having
only macrofluidic dimensions; a second fluid vessel having at least
one microfluidic dimension; a microfluidic channel having first and
second ends, said first end attached to at least one portion of at
least one side of said first fluid vessel and said second end
attached to at least one portion of at least one side of said
second fluid vessel such that said attachment to said first vessel
is larger in at least one dimension than said attachment to said
vessel.
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 a device for
reducing the effect of surface tension on fluids flowing in
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 fluid 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] Surface effects describe the character of a surface on a
micro scale. Materials often have unbound electrons, exposed polar
molecules, or other molecular level features that generate a
surface charge or reactivity characteristic. Due to scaling, these
surface effects or surface forces are substantially more pronounced
in microstructures than they are in traditionally sized devices.
This is particularly true in microscale fluid handling systems
where the dynamics of fluid movement are governed by external
pressures and by attractions between liquids and the materials they
are flowing through.
[0010] This invention deals with the passive control of fluids
within a microfluidic circuit. The passive control is generated by
using the natural forces that exist on a microscale, specifically
capillarity, which is caused by the attraction or repulsion of a
fluid toward certain materials.
SUMMARY OF THE INVENTION
[0011] It is therefore an object of the present invention to
provide a device for reducing the effect of surface tension on
fluids flowing within a microfluidic channel.
[0012] It is a further object of the present invention to provide a
microfluidic structure in which fluids flow from a macrochannel
into a microchannel to insure smooth flow within the microfluidic
structure.
[0013] These and other objects of the present invention will be
more readily apparent from the description and drawings that
follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a plan view of a microfluidic structure including
an H-Filter using the principles of the present invention; and
[0015] FIG. 2 is a fragmentary, cross-sectional side view of the
microfluidic structure shown in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] FIG. 1 shows a microfluidic analysis card 10 which contains
an H-Filter 12, which structure is described in detail in U.S. Pat.
No. 5,932,100, incorporating the present invention. H-Filter 12
includes a first reservoir 14 and a second reservoir 16. An outlet
channel 18 of reservoir 14 and an outlet channel 20 of reservoir 16
are both connected to a flow channel 24 at a first end 26. A second
end 28 of flow channel 24 is coupled to an exit channel 30, which
is connected to a reservoir 32 and also to an exit channel 34,
which is coupled to a reservoir 36. Reservoir 36 is also coupled to
a bellows 38 via a channel 40. It should be understood that
H-Filter 12 will also operate using gravity as a driving force.
[0017] Reservoir 14 contains a vent hole 42 and an inlet port 44,
while reservoir 16 contains an inlet port 46. Reservoir 14 also
contains a narrowed lower section 50, which extends across the
lower length of reservoir 14, while reservoir 16 also contains a
similarly narrowed lower section 52 across the lower length of
reservoir 16.
[0018] Operation of H-Filter 12 is as follows: a sample fluid is
placed into inlet port 46 of reservoir 16 while an extractor
solution is placed into port 44 of reservoir 14. The fluids form a
stream and flow through channels 20, 18 respectively to end 26 of
channel 24. The fluids form a stream and flow laminarly within
channel 24 while particles from the sample fluid diffuse across the
laminar junction into the extractor fluid. As the stream reaches
end 28 of channel 24, the extractor fluid containing particles flow
through channel 30 into reservoir 32, while the sample fluid flows
through channel 34 into reservoir 36.
[0019] Narrowed section 50 of reservoir 14 fills with sample fluid
when the sample is loaded into inlet port 44. Since the structure
of reservoir 14 is not microscale, and outlet channel 18 is of a
microscale dimension, the effect of surface tension would generally
prevent the fluid from flowing smoothly from reservoir 14 to
channel 18. However, as can be clearly seen in FIGS. 1 and 2, the
narrow lower section 50, which runs the entire length of reservoir
14, is of essentially the same microdimensions of channel 18; thus,
fluid moves smoothly and consistently from reservoir 14 into
channel 18 and through the rest of the H-Filter structure. This is
also true for fluids flowing from reservoir 16 into channel 20, as
the narrow lower section 52 of reservoir 16 fills with fluid and
flows smoothly into channel 20 with little or no surface tension
effect.
[0020] 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 modifications may be made without departing from
the true spirit and scope of the invention as defined in the
appended claims.
* * * * *