U.S. patent application number 16/169738 was filed with the patent office on 2019-02-28 for microfluidic device, system and method.
This patent application is currently assigned to Quidel Cardiovascular Inc.. The applicant listed for this patent is Quidel Cardiovascular Inc.. Invention is credited to William Patrick COFFEY, Paul Michael CRIVELLI, Austin Matthew DERFUS, Tuan Hoang DO, Remus Anders Brix HAUPT, Emily PARKER, Gregory RENEFF, Armando Raul TOVAR.
Application Number | 20190064158 16/169738 |
Document ID | / |
Family ID | 49328068 |
Filed Date | 2019-02-28 |
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United States Patent
Application |
20190064158 |
Kind Code |
A1 |
COFFEY; William Patrick ; et
al. |
February 28, 2019 |
MICROFLUIDIC DEVICE, SYSTEM AND METHOD
Abstract
A combination of capillary forces and gas pressure is used to
control the movement of liquid samples within a microfluidic
device. A liquid sample introduced to a proximal portion of a
capillary channel of a microfluidic device moves by capillary
action partway along the capillary channel. As the liquid sample
moves, a pressure of a gas acting upon a distal gas-liquid
interface of the liquid sample increases by an amount sufficient to
stop further movement of the liquid sample. To initiate further
movement of the liquid sample, a pump connected to a distal portion
of the capillary channel decreases the pressure of the gas acting
upon the distal gas-liquid interface of the liquid sample by an
amount sufficient to permit the liquid sample to move by capillary
action further along the capillary channel of the microfluidic
device.
Inventors: |
COFFEY; William Patrick;
(Encinitas, CA) ; CRIVELLI; Paul Michael; (San
Diego, CA) ; DERFUS; Austin Matthew; (Carlsbad,
CA) ; DO; Tuan Hoang; (San Diego, CA) ; HAUPT;
Remus Anders Brix; (Encinitas, CA) ; PARKER;
Emily; (Encinitas, CA) ; RENEFF; Gregory; (San
Diego, CA) ; TOVAR; Armando Raul; (San Diego,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Quidel Cardiovascular Inc. |
San Diego |
CA |
US |
|
|
Assignee: |
Quidel Cardiovascular Inc.
|
Family ID: |
49328068 |
Appl. No.: |
16/169738 |
Filed: |
October 24, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14391643 |
Oct 9, 2014 |
10145842 |
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PCT/US2013/035505 |
Apr 5, 2013 |
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16169738 |
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61622987 |
Apr 11, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01L 2400/0406 20130101;
B01L 2400/0487 20130101; B01L 2300/0883 20130101; B01L 2400/0688
20130101; B01L 2300/0816 20130101; B01L 2300/0681 20130101; G01N
33/54306 20130101; G01N 33/54366 20130101; B01L 2300/0874 20130101;
B01L 2200/0621 20130101 |
International
Class: |
G01N 33/543 20060101
G01N033/543 |
Claims
1. A micro fluidic system, comprising: (a) a capillary flow channel
comprising a proximal opening and a distal opening; (b) a dry
reagent and a detection zone disposed within the capillary flow
channel, the detection zone being disposed distal to the dry
reagent; (c) a pump in fluidic communication with the distal
opening of the capillary flow channel; (d) a liquid sample disposed
within a proximal portion of the capillary flow channel, the liquid
sample comprising a gas-liquid interface disposed within the
capillary flow channel proximal to the reagent; and (e) a gas
disposed within the capillary flow channel distal to the gas-liquid
interface of the liquid sample, the gas exerting a pressure on the
gas-liquid interface of the liquid sample, the pressure being
sufficient to prevent the liquid sample from advancing along the
capillary flow channel toward the reagent.
2. The micro fluidic system of claim 1 further comprising a
controller configured to operate the pump to decrease the gas
pressure in the capillary flow channel by an amount sufficient to
cause the liquid sample to advance along the capillary flow channel
until at least the gas-liquid interface of the liquid sample
contacts the reagent.
3. The microfluidic system of claim 2 wherein the controller is
configured to operate the pump to decrease the gas pressure in the
capillary flow channel by an amount sufficient to cause the liquid
sample to advance along the capillary flow channel until all of the
reagent has been contacted by at least some of the liquid
sample.
4. A method for determining the presence of a target in a liquid
sample, the method comprising: (a) receiving a sample of blood
obtained from a patient; (b) introducing the at least a portion of
the blood sample to a filter of a microfluidic device, a distal
portion of the filter being in fluidic contact with a proximal
portion of a capillary flow channel disposed within the
microfluidic device, the filter configured to separate red blood
cells from a liquid portion of the blood sample; (c) allowing at
least a portion of the liquid portion of the blood sample to
advance toward a distal portion of the capillary flow channel until
a gas pressure acting upon a distal gas-liquid interface of the
liquid portion of sample stops the liquid portion from advancing
further; (d) subsequently, decreasing the gas pressure acting upon
the distal gas-liquid interface to permit the liquid portion of
sample to advance a further distance along the capillary flow
channel; and (e) subsequently, determining the presence of the
target in the liquid portion of sample within the capillary flow
channel.
5. A method for determining the presence of a target in a liquid
sample, the method comprising: (a) positioning a microfluidic
device in an operable relation with a reader for the microfluidic
device, the microfluidic device comprising a capillary flow channel
comprising a proximal opening and a distal opening; (b) positioning
a pump in fluidic relation to the distal portion of the capillary
flow channel; (c) introducing a liquid sample to the proximal
portion of the capillary flow channel, the liquid sample advancing
by capillary flow along only a portion of the capillary flow
channel until a gas pressure acting upon a distal gas-liquid
interface of the liquid sample prevents the liquid sample from
advancing further along the capillary flow channel; (d) actuating a
pump to decrease the pressure of gas acting upon the distal
gas-liquid interface of the liquid sample so that the liquid sample
advances a further distance along the capillary flow channel; and
(e) determining the presence of the target in the liquid sample
within the capillary flow channel
6. The method of claim 5, further comprising disconnecting the pump
from fluidic relation to the distal portion of the capillary flow
channel prior to determining the presence of the target in the
liquid sample.
7. The method of claim 5 wherein the step of actuating the pump
comprises first actuating the pump a first rate to cause the liquid
sample to advance at a first rate along the capillary flow channel
and then actuating the pump at a second higher rate to cause the
liquid sample to advance at a second higher rate along the
capillary flow channel.
8. A microfluidic device, comprising: (a) a filter, the filter
having an upper surface, a lower surface and a perimeter; (b) a
substrate having a surface, the lower surface of the filter and the
surface of the substrate defining a spatially-dependent capillarity
therebetween, the capillarity decreasing from a central portion of
the lower surface of the filter toward the perimeter along at least
two opposed directions.
9. The microfluidic device of claim 8, wherein the surface of the
substrate is convex.
10. The microfluidic device of claim 8 wherein a gap between the
lower surface of the filter and the surface of the substrate
increases from a central portion of the lower surface of the filter
toward the perimeter along at least two opposed directions.
11. A microfluidic device, comprising: (a) a first substrate having
a first surface defining: (i) a recess having a first depth; (ii) a
groove, a proximal portion of the groove disposed adjacent to the
recess, the proximal portion of the groove having a second depth
less than the first depth; and (iii) a filter contact surface
having a third depth less than the first depth. (b) a second
substrate having a second surface opposed to the first surface of
the first substrate; (c) a capillary channel defined by the groove
and the second surface of the second substrate, the capillary
channel having a proximal opening at the proximal portion of the
groove; and (d) a filter disposed between the first surface of the
first substrate and the second surface of the second substrate,
wherein the filter has a first surface and a first portion of the
first surface of the filter contacts the filter contact surface and
a second portion of the first surface of the filter and a portion
of the recess define a cavity therebetween, the cavity being in
fluidic communication with the proximal opening of the capillary
channel.
12. The microfluidic device of claim 11, wherein the filter contact
surface comprises a ridge extending proximally from the proximal
portion of the groove.
13. The microfluidic device of claim 11, wherein the ridge extends
substantially parallel to a major axis of a proximal portion of the
capillary channel.
14. The microfluidic device of claim 11, wherein the cavity
comprises a first portion offset from a first side of the ridge and
a second portion offset from a second, opposite side of the
ridge.
15. The microfluidic device of claim 11, wherein a proximal edge of
the filter and the proximal portion of the capillary channel define
a gap therebetween.
Description
FIELD OF THE INVENTION
[0001] The subject matter described herein relates to
microfluidics, and more particularly to a microfluidic device,
system and method for control of fluid flow.
BACKGROUND INFORMATION
[0002] Microfluidics relates to the manipulation of small volumes
of one or more fluids, e.g., gases and/or liquids. The total volume
of fluid may be, e.g., about 250 microliters or less, e.g., about
125 microliters or less, about 75 microliters or less, about 50
microliters or less, or about 25 microliters or less.
[0003] The use of microfluidics to determine the presence of at
least one target in a liquid sample is known. For example, U.S.
Pat. No. 7,824,611, which is incorporated herein by reference in
its entirety, discloses immunological assay devices, assay systems
and device components having at least two opposing surfaces
disposed a capillary distance apart, at least one of which is
capable of immobilizing at least one target ligand or a conjugate
in an amount related to the presence or amount of target ligand in
the sample from a fluid sample in a zone for controlled fluid
movement to, through or away the zone. The U.S. Pat. No. 7,824,611
patent further discloses the use of reagents, such as receptors and
conjugates, and biosensors, such as electrochemical, optical,
electro-optical, or acoustic mechanical devices, to determine the
presence of one or more targets.
SUMMARY OF THE INVENTION
[0004] In one embodiment, the present invention relates to a method
for manipulating a liquid sample within a microfluidic device. The
method includes moving the liquid sample by capillary action along
a capillary channel of the microfluidic device and then increasing
a pressure of a gas acting upon a distal gas-liquid interface of
the liquid sample by an amount sufficient to stop the movement of
the liquid sample along the capillary channel. The pressure of the
gas acting upon the distal gas-liquid interface of the liquid
sample is decreased by an amount sufficient to permit the liquid
sample to move by capillary action further along the capillary
channel of the microfluidic device. The steps of moving the liquid
sample by capillary action, increasing the pressure, and then
decreasing the pressure may be repeated one or more times. In
embodiments, the liquid sample contacts a dried reagent disposed
within the capillary channel during the step of moving the liquid
sample.
[0005] In a subsequent step of moving the sample, the liquid sample
may contact a detection zone disposed within the microfluidic
device. The method may further include determining the presence of
one or more targets in a liquid sample.
[0006] The method may employ, for example, immunology (such as
through the use of antibodies) and/or electrochemistry to determine
the presence of the one or more targets. The method includes:
introducing the liquid sample to a proximal portion of a capillary
flow channel; advancing the liquid sample at a first flow rate
toward a distal portion of the capillary flow channel until at
least a distal gas-liquid interface of the liquid sample contacts a
conjugate disposed in dry form within the capillary flow channel,
the conjugate comprising a binding agent having an affinity for the
target; subsequently, by increasing a gas pressure differential
between a proximal gas-liquid interface of the liquid sample and
the distal gas-liquid interface of the liquid sample, advancing the
liquid sample at a second flow rate toward the distal portion of
the capillary flow channel until at least the distal gas-liquid
interface contacts a detection zone within the capillary flow
channel, the detection zone comprising a second binding agent
having an affinity for a complex comprising the conjugate and the
target, the second flow rate being slower than the first flow rate;
and subsequently, by increasing the gas pressure differential
between the proximal and distal gas-liquid interfaces of the liquid
sample, advancing the liquid sample a third flow rate toward the
distal portion of the capillary flow channel until at least a
majority of conjugate is (a) bound to the second binding agent
and/or been advanced beyond the detection zone toward the distal
end of the capillary flow channel
[0007] In any of the foregoing embodiments, the capillary flow
channel may be disposed within a microfluidic device.
[0008] The method of any of the foregoing embodiments may, further
comprise, after the step of introducing the liquid sample,
advancing the liquid sample by capillary flow along the capillary
flow channel until the gas pressure acting upon the distal
gas-liquid interface stops the liquid sample from advancing further
along the capillary flow channel
[0009] In any of the methods of any of the foregoing embodiments
the liquid sample may be stopped prior to contacting the
conjugate.
[0010] In any of the methods of any of the foregoing embodiments
the liquid sample may be stopped after contacting the
conjugate.
[0011] In any of the methods of any of the foregoing embodiments
the method may further comprise providing a fluidic connection
between a pump and a distal portion of the capillary flow channel
The step of providing a fluidic connection may be performed prior
to the step of introducing the liquid sample. In any of the methods
of any of the foregoing embodiments, the method may comprise
terminating the fluidic connection between the pump and the distal
portion of the capillary flow channel and then detecting conjugate
present in the detection zone. The step of detecting the conjugate
may comprise placing the microfluidic device in operable
association with an optical reader for the microfluidic device. The
step of detecting the conjugate may comprise using a biosensor to
detect the conjugate. The biosensor may be an electrochemical,
optical, electro-optical, or acoustic mechanical detector.
[0012] The step of providing the fluidic connection may comprise
automatically positioning a proximal opening of the pump with
respect to a distal opening of the capillary flow channel.
[0013] In any of the methods of any of the foregoing embodiments
the steps of "increasing a gas pressure differential" may be
performed by increasing a volume of gas in communication with the
distal gas-liquid interface of the liquid sample.
[0014] In any of the methods of any of the foregoing embodiments
the steps of "increasing a gas pressure differential" may be
performed by actuating the pump. In any of the methods of any of
the foregoing embodiments actuating the pump may increase a volume
of gas in communication with the distal gas-liquid interface of the
liquid sample. The pump may be a syringe pump.
[0015] In any of the methods of any of the foregoing embodiments,
the liquid sample may experience a capillary force within the
capillary flow channel and the magnitude of a force applied to the
liquid sample by the "gas pressure differential" may be less than
about 15 times the magnitude of the capillary force, e.g., less
than about 10 times the magnitude of the capillary force, e.g.,
less than about 5 times the magnitude of the capillary force.
[0016] In any of the methods of any of the foregoing embodiments
the method may further include the step of detecting conjugate
bound to the detection zone. The step of detecting may be performed
while a volume of the detection zone is filled with liquid sample.
In any of the methods of any of the foregoing embodiments the
detection zone may have a volume and the step of detecting may be
performed after removing a majority of the liquid sample from the
detection zone. The step of detecting may be performed while a
majority of the volume of the detection zone is occupied by a gas.
The step of detecting may be performed without first introducing a
liquid other than the liquid sample into the detection zone. The
step of detecting the conjugate may comprise using a biosensor to
detect the conjugate. The biosensor may be an electrochemical,
optical, electro-optical, or acoustic mechanical detector.
[0017] In any of the methods of any of the foregoing embodiments
the liquid sample may comprise a biological sample obtained from a
mammal. For example, biological sample may comprise blood or urine.
The liquid sample may comprise a reagent. The liquid sample may be
formed by combining the reagent and the biological sample. The step
of combining may be performed prior to introducing the biological
sample to the capillary flow channel.
[0018] In any of the methods of any of the foregoing embodiments
the liquid sample may be a filtered liquid sample formed by passing
a liquid sample through a filter. The filter may be any of the
filters described herein. The filter may comprise pores and a size
of the pores may decrease proceeding from a proximal face of the
filter toward a distal face of the filter. In any of the methods of
any of the foregoing embodiments the filtered liquid sample may
comprise plasma and the step of passing the liquid sample through
the filter may comprise filtering red blood cells from the liquid
sample. In any of the methods of any of the foregoing embodiments
the biological sample may be blood obtained from a finger of a
human being. In any of the methods of any of the foregoing
embodiments the liquid sample may be prepared from a total volume
of blood of about 75 microliters or less, 50 microliters or less,
30 microliters or less, 20 microliters or less, such as about 15
microliters or less, such as about 10 microliters or less.
[0019] In any of the methods of any of the foregoing embodiments
the total volume of the liquid sample may be about 75 microliters
or less, 50 microliters or less, 30 microliters or less, 20
microliters or less, such as about 15 microliters or less, such as
about 10 microliters or less.
[0020] In any of the methods of any of the foregoing embodiments,
prior to the step of introducing the liquid sample, a distal
opening of the capillary flow channel may be open to the
atmosphere, and the method may further comprise closing the distal
opening of the capillary flow channel off from the atmosphere. The
step of closing off may be performed prior to introducing the
liquid sample. The step of closing off may be automatically after
or concurrently with a step of positioning the capillary flow
channel in operable relation with a reader configured to operate
the capillary flow channel to determine the presence of the at
least one target in the liquid sample. The step of closing off may
be performed by fluidically connecting the distal opening of the
capillary flow channel and a pump, e.g., by forming a gas tight
seal between the distal opening of the capillary flow channel and a
pump. The pump may be a syringe pump.
[0021] In another embodiment, the present invention relates to a
microfluidic system, comprising a capillary flow channel comprising
a proximal opening and a distal opening; a dry reagent and a
detection zone disposed within the capillary flow channel, the
detection zone being disposed distal to the dry reagent; a pump in
fluidic communication with the distal opening of the capillary flow
channel; a liquid sample disposed within a proximal portion of the
capillary flow channel, the liquid sample comprising a gas-liquid
interface disposed within the capillary flow channel proximal to
the reagent; and a gas disposed within the capillary flow channel
distal to the gas-liquid interface of the liquid sample, the gas
exerting a pressure on the gas-liquid interface of the liquid
sample, the pressure being sufficient to prevent the liquid sample
from advancing along the capillary flow channel toward the
reagent.
[0022] In any microfluidic system of any of the foregoing
embodiments, the microfluidic system may further comprise a
controller configured to operate the pump to decrease the gas
pressure in the capillary flow channel by an amount sufficient to
cause the liquid sample to advance along the capillary flow channel
until at least the gas-liquid interface of the liquid sample
contacts the reagent. The controller may be configured to operate
the pump to decrease the gas pressure in the capillary flow channel
by an amount sufficient to cause the liquid sample to advance along
the capillary flow channel until all of the reagent has been
contacted by at least some of the liquid sample. In any
microfluidic system of any of the foregoing embodiments the liquid
sample may experience a capillary force within the capillary flow
channel. In any microfluidic system of any of the foregoing
embodiments the magnitude of the pressure may be sufficient to
prevent the liquid sample from advancing along the capillary flow
channel toward the reagent is substantially equal to the magnitude
of the capillary force experienced by the liquid sample. The
controller may be configured to operate the pump to increase a
volume of gas in fluidic communication with the gas disposed within
the capillary flow channel by an amount sufficient to allow the
liquid sample to advance a desired distance along the capillary
flow channel.
[0023] In any microfluidic system of any of the foregoing
embodiments the system may comprise a reader configured to receive
the capillary flow channel and determine the presence of one or
more targets in the liquid sample. The reader may be configured to
automatically position the pump in fluidic communication with the
distal opening of the capillary flow channel The reader may be
configured to automatically move the pump away from the distal
opening of the capillary flow channel prior to determining the
presence of the one or more targets in the liquid sample. The
reader may be configured to position an optical excitation source
and an optical detector in optical communication with the detection
zone after moving the pump away from the distal opening of the
capillary flow channel The reader may employ a biosensor to detect
the target. The biosensor may be an electrochemical, optical,
electro-optical, or acoustic mechanical detector.
[0024] In any microfluidic system of any of the foregoing
embodiments the reagent may comprise a conjugate comprising a
detectable label and a binder for a target. The detection zone may
comprise a binder for the target or a complex of the conjugate and
the target.
[0025] In any microfluidic system of any of the foregoing
embodiments the system may comprise a microfluidic device and the
capillary flow channel may be disposed within the microfluidic
device.
[0026] In any microfluidic system of any of the foregoing
embodiments the capillary flow channel may be configured to receive
a total volume of liquid sample of less than about 75 microliters
or less, 50 microliters or less, 30 microliters or less, 20
microliters or less, such as about 15 microliters or less, such as
about 10 microliters or less.
[0027] In any microfluidic system of any of the foregoing
embodiments the system may further comprise a filter in fluidic
communication with a proximal portion of the capillary flow
channel, the filter being configured to filter red blood cells from
a sample comprising blood and the liquid sample comprises blood
from which the red blood cells have been removed. The filter may be
any of the filters disclosed herein.
[0028] Another embodiment of the present invention relates to a
method for determining the presence of at least one target in a
liquid sample. The method may comprise receiving a sample of blood
obtained from a patient; introducing the at least a portion of the
blood sample to a filter of a microfluidic device, a distal portion
of the filter being in fluidic contact with a proximal portion of a
capillary flow channel disposed within the microfluidic device, the
filter configured to separate red blood cells from a liquid portion
of the blood sample; allowing at least a portion of the liquid
portion of the blood sample to advance toward a distal portion of
the capillary flow channel until a gas pressure acting upon a
distal gas-liquid interface of the liquid portion of sample stops
the liquid portion from advancing further; subsequently, decreasing
the gas pressure acting upon the distal gas-liquid interface to
permit the liquid portion of sample to advance a further distance
along the capillary flow channel; and subsequently, determining the
presence of the target in the liquid portion of sample within the
capillary flow channel. The filter may be any of the filters
disclosed herein.
[0029] The method for determining the presence of a target in a
liquid sample may comprise positioning a microfluidic device in an
operable relation with a reader for the microfluidic device, the
microfluidic device comprising a capillary flow channel comprising
a proximal opening and a distal opening; positioning a pump in
fluidic relation to the distal portion of the capillary flow
channel; introducing a liquid sample to the proximal portion of the
capillary flow channel, the liquid sample advancing by capillary
flow along only a portion of the capillary flow channel until a gas
pressure acting upon a distal gas-liquid interface of the liquid
sample prevents the liquid sample from advancing further along the
capillary flow channel; actuating a pump to decrease the pressure
of gas acting upon the distal gas-liquid interface of the liquid
sample so that the liquid sample advances a further distance along
the capillary flow channel; and determining the presence of the
target in the liquid sample within the capillary flow channel
[0030] In any of the foregoing methods for determining the presence
of a target in a liquid sample the method may further comprise
disconnecting the pump from fluidic relation to the distal portion
of the capillary flow channel prior to determining the presence of
the target in the liquid sample.
[0031] In any of the foregoing methods for determining the presence
of a target in a liquid sample the step of actuating the pump may
comprise first actuating the pump a first rate to cause the liquid
sample to advance at a first rate along the capillary flow channel
and then actuating the pump at a second higher rate to cause the
liquid sample to advance at a second higher rate along the
capillary flow channel.
[0032] In any of the foregoing methods for determining the presence
of a target in a liquid sample the step of determining may be
employed using a biosensor. The biosensor may be an
electrochemical, optical, electro-optical, or acoustic mechanical
detector.
[0033] In another embodiment, the present invention relates to a
filter, the filter having an upper surface, a lower surface and a
perimeter; and a substrate having a surface, the lower surface of
the filter and the surface of the substrate defining a
spatially-dependent capillarity therebetween, the capillarity
decreasing from a central portion of the lower surface of the
filter toward the perimeter along at least two opposed
directions.
[0034] At least a portion of the surface of the substrate may be
convex and/or tapered.
[0035] In any of the foregoing filters, a gap between the lower
surface of the filter and the surface of the substrate may increase
from a central portion of the lower surface of the filter toward
the perimeter along at least two opposed directions. In each of the
opposed directions, the gap may increase from about 10 microns,
e.g., about 15 microns, about 20 microns. In each of the opposed
directions, the gap may increase to about 50 microns, to about 75
microns, to 100 microns, to about 200 microns, to about 300
microns, to about 500 microns. In each of the opposed directions,
the gap may increase over a lateral distance of at least about 750
microns, at least about 1500 microns, at least about 2000 microns.
In each of the opposed directions, the gap may increase over a
distance of about 5000 microns or less, about 3000 microns or less,
about 2500 microns or less.
[0036] In any of the foregoing filters, a portion of the surface of
the substrate may contact a central portion of the lower surface of
the filter.
[0037] In any of the foregoing filters, the filter may have a
length and a width, and the portion of the surface of the substrate
may contact the central portion of the lower surface of the filter
along substantially all of the length of the filter. The length of
the filter may be at least about 1.25 times, e.g., at least about
1.5 times, at least about 2.0 times as great as the width of the
filter. The length of the filter may be about the same as the width
of the filter. The length of the filter may be at least about 2 mm,
e.g., at least about 3 mm, e.g., at least about 5 mm, e.g., at
least about 7.5 mm, e.g., at least about 10 mm. The length of the
filter may be about 15 mm or less, e.g., about 10 mm or less. The
width of the filter may be at least about 2 mm, e.g., at least
about 2 mm, e.g., at least about 3 mm, e.g., at least about 5 mm,
e.g., at least about 7.5 mm, e.g., at least about 10 mm. The width
of the filter may be about 15 mm or less, e.g., about 10 mm or
less, about 7.5 mm or less, about 5 mm or less.
[0038] In any of the foregoing filters in which a portion of the
surface of the substrate contacts the lower surface of the filter,
the surface of the substrate may contact the lower surface of the
filter along less than about half of the width of the filter, e.g.,
less than about one quarter the width of the filter, e.g., less
than about 1/8 of the width of the filter. In any of the foregoing
filters in which a portion of the surface of the substrate contacts
the lower surface of the filter, the surface of the substrate may
contact the lower surface of the filter along at least about half
of the length of the filter, e.g., at least about 3/4 of the length
of the filter, e.g., at least about 4/5 of the length of the
filter, at least about 9/10 of the length of the filter, e.g.,
substantially all of a length of the filter. The portion of the
substrate that contacts the lower surface of the filter may contact
the filter along a length of the filter of at least about 1 mm, at
least about 2 mm, at least about 5 mm, at least about 7.5 mm, at
least about 10 mm. The portion of the substrate that contacts the
lower surface of the filter may contact the filter along a width of
the filter of at least about 100 microns, at least about 200
microns, at least about 300 microns, at least about 500 microns.
The portion of the substrate that contacts the lower surface of the
filter may contact the filter along a width of the filter of about
1000 microns or less, about 750 microns or less, about 500 microns
or less.
[0039] In any of the foregoing filters, a portion of the surface of
the substrate may contact the central portion of the lower surface
of the filter along a first dimension of the filter and along a
second dimension of the filter and wherein the distance contacted
along the first dimension of the filter may be at least about 5
times greater, at least about 7.5 times greater, at least about 10
times greater, than along the second dimension of the filter, and
wherein the first and second dimensions may be perpendicular.
[0040] Any of the foregoing filters may further comprise a
capillary flow channel having an opening in fluidic communication
with a space between the lower surface of the filter and the
surface of the substrate.
[0041] Any of the foregoing filters may further comprise a vent in
fluidic communication with a space between the lower surface of the
filter and the surface of the substrate. The opening of the
capillary channel and the vent may be spaced apart by substantially
all of a length or width of the filter.
[0042] Any of the foregoing filters may comprise pores and a size
of the pores may decrease proceeding from the upper surface of the
filter toward the lower surface of the filter.
[0043] Any of the foregoing filters may be configured to separate
red blood cells from a sample of blood and to permit passage of
liquid components of the sample of blood.
[0044] In any of the foregoing filters, the lower surface of the
filter may be convex or tapered along at least one dimension. The
lower surface of the filter may be convex or tapered along a
dimension perpendicular to a dimension of the filter along which
the lower surface of the filter contacts the surface of the
substrate.
[0045] In any of the foregoing filters, a portion of the surface of
the substrate may contact the central portion of the lower surface
of the filter along a first dimension of the filter and along a
second dimension of the filter and wherein the distance contacted
along the first dimension of the filter may be at least about 5
times, e.g., at least about 7.5 times, e.g., at least about 10
times, greater than along the second dimension of the filter, and
wherein the first and second dimensions may be perpendicular and
further wherein the lower surface of the filter may be convex or
tapered along the second dimension of the filter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] FIG. 1 is a perspective top view of a microfluidic
device.
[0047] FIG. 2 is a close-up view of the microfluidic device of FIG.
1 from the perspective of FIG. 1.
[0048] FIG. 3 is a further close-up view of the microfluidic device
of FIG. 1 from the perspective of FIGS. 1 and 2.
[0049] FIG. 4a is a close-up perspective cross-sectional view
through a sample introduction zone of the microfluidic device of
FIG. 1 taken along the cross section shown in FIG. 7.
[0050] FIG. 4b is a further close-up perspective cross-sectional
view through a sample introduction zone of the microfluidic device
of FIG. 1 taken along the cross section shown in FIG. 7 from the
perspective of FIG. 4a.
[0051] FIG. 5 is a cross-sectional view through the sample
introduction zone of the microfluidic device of FIG. 1 taken along
the cross section shown in FIG. 7.
[0052] FIG. 6a is a close-up perspective cross-sectional view
through a sample introduction zone of the microfluidic device of
FIG. 1 taken along the cross section shown in FIG. 7
[0053] FIG. 6b is a further close-up perspective cross-sectional
view through a sample introduction zone of the microfluidic device
of FIG. 1 taken along the cross section shown in FIG. 7 from the
perspective of FIG. 6a.
[0054] FIG. 7 is identical with FIG. 1 except for showing the
cross-sections of FIGS. 4a, 4b, 5, 6a, and 6b.
[0055] FIG. 8 is a perspective top view of the microfluidic device
of FIG. 1 with a sample filter removed.
[0056] FIG. 9 is a close-up view of the microfluidic device of FIG.
1 with the sample filter removed as in FIG. 8.
[0057] FIG. 10 is a further close-up view of the microfluidic
device of FIG. 1 with the sample filter removed as in FIG. 8.
[0058] FIG. 11 is a perspective top view of the microfluidic device
of FIG. 1 with the sample filter removed and with an upper
substrate removed.
[0059] FIG. 12 is a close up view of the micro fluidic device of
FIG. 1 with the sample filter and upper substrate removed as in
FIG. 11.
[0060] FIG. 13 is a perspective view of an underside of the upper
substrate of the micro fluidic device of FIG. 1.
[0061] FIG. 14 is a close-up view of the underside of the upper
substrate shown in FIG. 13.
[0062] FIG. 15 is a top view of the microfluidic device of FIG. 1
in a first state following the introduction of a liquid sample but
with the top substrate having been removed as in FIG. 5 and further
showing a pump and pressure sensor.
[0063] FIG. 16 shows the microfluidic device of FIG. 15 in a second
state following the introduction of a liquid sample.
[0064] FIG. 17 shows the microfluidic device of FIG. 15 in a third
state following the introduction of a liquid sample.
[0065] FIG. 18 shows the microfluidic device of FIG. 15 in a fourth
state following the introduction of a liquid sample.
DETAILED DESCRIPTION OF THE INVENTION
[0066] With reference to FIGS. 1-7, a microfluidic device 20 is
configured to receive a liquid sample for the determination of one
or more targets present in the liquid sample. Microfluidic device
20 is formed of a lower substrate 21 and an upper substrate 23
defining therebetween a capillary flow channel 25 having a proximal
opening 27 and a vent 29 disposed adjacent a distal portion 30 of
capillary channel 25. A reagent 41 and detection zone 43 are
disposed within capillary flow channel 25. Microfluidic device 20
further includes a sample introduction port 31 through upper
substrate 23. A liquid sample is introduced to microfluidic device
via introduction port 31.
[0067] Filter 33 has an upper surface 35 and a lower surface 37
disposed between lower and upper substrates 21 and 23. Filter 35 is
typically configured to receive a liquid sample, e.g., blood or
urine, comprising particulates, e.g., cells, such as red or white
blood cells, by application to upper surface 35 and to prepare a
filtered liquid with a reduced number such particulates, e.g.,
essentially free of such particulates, through lower surface
37.
[0068] In embodiments, filter 35 includes pores (not shown) having
a size that decreases proceeding from upper surface 35 toward lower
surface 37. The size variation of the pores is typically configured
so that the particulates in a liquid sample applied to surface 35
pass into an interior of filter 33 but do not pass through second
surface 37 of filter 33. In embodiments, filter 33 permits liquid
sample passing from upper surface 35 to lower surface 37 to move
laterally within filter 35, e.g., along a path p2 (FIGS. 4a and 4b)
and/or a path pi (FIGS. 6a and 6b). Such lateral movement permits
liquid sample applied to filter 33 at upper surface 35 within port
31 to exit lower surface 37 of filter 33 at locations laterally
spaced apart from port 31.
[0069] The filter may also be used to deliver one or more reagents
to the liquid sample such as one or more buffers, one or more
anti-coagulants, one or more salts, one or more stabilizers, one or
more protein blockers protein, or combination of one or more such
reagents. Additional or alternative reagents include reagents that
reduce hemolysis of red blood cells in blood samples and reagents
that improve the wetability of the filter with respect to aqueous
samples.
[0070] Filter 33 has a length 11 and a width w1 (FIG. 2) sufficient
to provide an area to accommodate a desired amount of sample
applied to upper surface 35 thereof. For example, length 11 may be
at least about 2.5 mm, at least about 5 mm, at least about 7.5 mm
Length 11 may be about 25 mm or less, about 20 mm or less, about 15
mm or less, about 10 mm or less. Width w1 may be at least about 2.5
mm, at least about 3.5 mm, at least about 5 mm. Width w1 may be
about 17.5 mm or less, about 12.5 mm or less, about 10 mm or less,
about 7.5 mm or less.
[0071] Filter 33 is typically secured with respect to upper
substrate 23. For example, a perimeter portion 39 of upper surface
35 of filter 33 may be attached, e.g., by heat staking, laser
welding, or via an adhesive, to a lower surface 41 of upper
substrate 23. In the embodiment of FIGS. 1-3, filter 33 is not
attached to lower substrate 21, although such attachment may be
used. Also with reference to FIGS. 13 and 14, a portion of filter
33, e.g., an upper portion of upper surface 35 disposed interior to
perimeter 39, is accommodated within a recess 43 of a lower surface
45 of upper substrate 23. Recess 43 includes a plurality of
projections 47 that project outwards from lower surface 45 of
substrate 23 for a distance d1. Projections 47 contact upper
surface 35 of filter 33 forming a cavity 51 having a height about
the same as, e.g., the same as, distance d1. Typically, distance d1
is sufficient to permit a gas and/or liquid sample to flow between
upper surface 35 of filter 33 and lower surface 45 of substrate 23.
In embodiments, d1 may be at least about 5 microns, at least about
10 microns, at least about 15, microns, or at least about 25
microns. In embodiments, d1 is about 1000 microns or less, about
250 microns or less, about 175 microns or less, about 125 microns
or less, or about 100 microns or less.
[0072] Recess 43 also includes a plurality of vents 49 that permit
gas to pass between recess 43 and the ambient atmosphere (e.g., the
atmosphere generally surrounding the microfluidic device) without
passing through port 31. In use, liquid sample applied to filter 33
through port 31 travels laterally across surface 35 of filter 33 in
gap 51 between surface 35 and surface 43 of upper substrate 23
while gas displaced by the advancing liquid escapes recess 43 via
vents 49. Thus, sample applied to port 31 will contact an area of
upper surface 35 of filter 33 that is larger than an area of port
31. This permits a more efficient use of filter 33 than if liquid
applied to port 31 contacted an area of upper surface 35 limited to
the area of port 31. In embodiments, a ratio of an area of upper
surface 35 of filter 33 to an area of port 31 is at least about
1.5, at least about 2, or at least about 2.5. In embodiments, the
ratio of the area of upper surface 35 of filter 33 to the area of
port 31 is about 10 or less, about 7.5 or less, or about 5 or less.
Typically, liquid sample applied to filter 33 through port 31 will
contact at least about 50%, at least about 75%, at least about
80%>, at least about 90%>, or more of the area of upper
surface 35 of filter 33.
[0073] With reference to FIGS. 4a, 4b, 5, 6a, 6b, and 10, an upper
surface 53 of lower substrate 21 defines a filter contact surface
55 comprising a ridge 57 and a distal portion 59. A lower surface
37 of filter 33 contacts lower substrate 21 only at filter contact
surface 55 (although in some embodiments, lower surface 37 may
contact lower substrate 21 at locations other than filter contact
surface 55).
[0074] Filter contact surface 55 contacts lower surface 37 of
filter 33 only at locations of lower surface 37 that are disposed
inwardly from perimeter 39 of filter. A distance between perimeter
39 and the nearest contact point of contact surface 55 may be at
least about 250 microns, at least about 375 microns, at least about
500 microns, at least about 750 microns, or at least about 1 mm
[0075] Ridge 57 extends proximally from a proximal floor 61 of
proximal opening 27 of capillary channel 25 to distal portion 59 of
filter contact surface 55 (FIG. 10). In embodiments, ridge 57 of
filter contact surface 55 contacts lower surface 37 of filter 33 at
one or more locations spaced apart along at least about 50%, at
least about 70%, at least about 80%), at least about 90%>, at
least about 95%>, e.g., substantially all of length 11 of filter
33. For example, ridge 57 of filter contact surface 55 may contact
lower surface 37 of filter 33 continuously (i.e., without gaps)
along at least about 50%>, at least about 70%>, at least
about 80%), at least about 90%>, at least about 95%>, e.g.,
substantially all of length 11 of filter 33. In embodiments, a
length 12 of ridge 57 of filter contact surface 55 is at least
about 5 mm, at least about 7.5 mm, at least about 10 mm. Length 12
may be about 25 mm or less, about 20 mm or less, or about 15 mm or
less.
[0076] In embodiments, ridge 57 of filter contact surface 55
contacts lower surface 37 of filter 33 at one or more locations
spaced apart along about 50% or less, about 30% or less, about 25%o
or less, about 20%> or less, about 15% or less, or about 10%>
or less of width w1 of filter 33. In embodiments, ridge 57 of
filter contact surface 55 has a width w2 (FIG. 12) of at least
about 100 microns, at least about 200 microns, at least about 300
microns, at least about 500 microns. Width w2 of filter contact
surface 55 may be about 1000 microns or less, about 750 microns or
less, about 650 microns or less, or about 500 microns or less. In
embodiments, length 12 of ridge 57 is at least about 5 times
greater, at least about 7.5 times greater, at least about 10 times
greater, at least about 15 times greater than width w2 of ridge 57
where length 12 and width w2 are taken along perpendicular
dimensions of ridge 57.
[0077] A maximum length 13 of distal portion 59 of filter contact
surface 55 is typically less than length 12 of ridge 57 of filter
contact surface 55 (FIG. 12). For example, a ratio of 13 and 13 may
be about 0.5 or less, about 0.35 or less, about 0.25 or less, about
0.2 or less, or about 17.5 or less. A minimum length 14 of distal
portion 59 of filter contact surface 55 is typically less than
length 13 (FIG. 12). For example, a ratio of length 14 and 13 may
be about 0.95 or less, about 0.9 or less, about 0.8 or less.
[0078] Ridge 57 of filter contact surface 55 defines first and
second opposed walls 63a, 63b and distal portion 59 of filter
contact surface 55 defines first and second distal walls 65a, 65b.
Proximal portion 61 of capillary channel 25 defines first and
second proximal walls 67a, 67b. Upper surface 53 of lower substrate
21 defines first and second sloping floor portions 69a, 69b and
first, second and third hydrophobic floor portions 71a, 71b, 71c.
First and second sloping floor portions 69a, 69b and first and
second hydrophobic floor portions 71a, 71b are respectively
separated by first and second junctions 73a, 73b. A third
hydrophobic floor portion 71c is disposed distal to a distal wall
81 extending downward from filter contact surface 59.
[0079] As seen, for example, in FIGS. 10 and 12, peripheral
portions of first, second, and third hydrophobic floor portions
71a, 71b, 71c abut peripheral walls 79a, 79b, 79c, 79e that extend
upward to define a perimeter of a recess 81 in upper surface 53 of
lower substrate 23. Capillary contact surface 55 and first and
second proximal floor portions 69a, 69b constitute a projection
extending above first, second, and third hydrophobic floor portions
71a, 71b, 71c within recess 81.
[0080] Taken together, first and second opposed walls 63a, 63b,
first and second distal walls 65a, 65b, first and second proximal
walls 67a, 67b, first and second junctions 73a, 73b, first and
second sloping floor portions 69a, 690b, and portions of lower
surface 37 above first and second sloping floor portions 69a, 690b,
and portions of lower surface 37 below first and second sloping
floor portions 69a, 690b define respective sample cavities 75a,
75b. With reference to FIGS. 4b, 6a and 12, sample cavities 75a,
75b are spaced apart from, e.g., disposed below, a level of floor
61 of capillary channel 25 along an axis a2 oriented normal to
lower substrate 21. In embodiments, at least about 50%, at least
about 75%, at least about 85%, at least about 95%, essentially all
of a volume of cavities 75a, 75b is disposed below floor 61 of the
proximal portion of capillary channel 25 along axis a2. In
embodiments, at least about 50%o, at least about 75%, at least
about 85%, at least about 95%, or essentially all of an active area
of lower surface 37 of filter 33 is disposed at or below floor 61
of the proximal portion of capillary channel 25 along axis a2. In
embodiments, at least about 50%, at least about 75%o, at least
about 85%, at least about 95%, essentially all of a volume of
cavities 75a, 75b is disposed at or at a greater distance along
axis a2 from an upper surface of upper substrate 23 than floor 61
of the proximal portion of capillary channel 25. In embodiments, at
least about 50%), at least about 75%, at least about 85%, at least
about 95%, or essentially all of an active area of lower surface 37
of filter 33 is disposed at or at a greater distance along axis a2
from an upper surface of upper substrate 23 than floor 61 of the
proximal portion of capillary channel 25. An active area of filter
33 is the area through which filtered liquid emerges during
use.
[0081] Taken together, first, second, and third hydrophobic floor
portions 71a, 71b, 71c, portions of lower surface 37 of filter 33
above and first, second, and third hydrophobic floor portions 71a,
71b, 71c peripheral walls 79a, 79b, 79c, 79e define a peripheral
cavity 85 in gaseous communication with sample cavities 75a, 75b. A
vent 83 permits gas to pass between on the one hand active cavities
75a, 75b and peripheral cavity 85 and, on the other hand, the
ambient atmosphere (e.g., the atmosphere generally surrounding the
microfluidic device) without passing through filter 33. Vent 83 is
disposed distal of active cavities 75a, 75b.
[0082] A height d2 of first and second opposed walls 63a, 63b is
typically at least about 10 microns, at least about 20 microns, at
least about 30 microns, at least about 50 microns, at least about
75 microns, at least about 100 microns, or at least about 150
microns. Height d2 may be about 175 microns or less, about 125
microns or less, about 100 microns or less, about 75 microns or
less, or about 50 microns or less. Typically, height d2 of first
and second opposed walls 63a, 63b is about the same as, e.g., the
same, as the height of first and second proximal walls 67a, 67b
immediately adjacent ridge 57 and proximal portion 61 of capillary
channel 25. In embodiments, height d2 is zero so that first and
second sloping floor portions 69a, 69b slope downwards from ridge
57 of filter contact surface 55.
[0083] Because first and second sloping floor portions 69a, 69b
slope away from lower surface 37 of filter 33 proceeding laterally
away from ridge 57, the height of first and second proximal walls
67a, 67b increases from a minimum immediately adjacent ridge 57 and
proximal portion 61 of capillary channel 25 to a maximum height d3
at lateral portions 77a, 77b of first and second proximal walls
67a, 67b. Height d3 of lateral portions 77a, 77b of first and
second proximal walls 67a, 67b is typically at least about 30
microns, at least about 50 microns, at least about 75 microns, at
least about 100 microns, at least about 150 microns, at least about
200 microns, or at least about 250 microns. Height d3 may be about
500 microns or less, about 350 microns or less, about 300 microns
or less, about 275 microns or less, or about 225 microns or less.
First and second sloping floor portions 69a, 69b have a convex
shape in at least one dimension, e.g., are cylindrically convex
about an axis extending between first and second proximal walls
67a, 67b and first and second distal walls 65a, 65b. In
embodiments, first and second sloping floor portions 69a, 69b are
planar or arcuate.
[0084] A height of first and second distal walls 65a, 65b, i.e.,
the distance between distal portion 59 of filter contact surface 55
and first and second sloping floor portions 69a, 69b, is typically
about the same as the height of first and second proximal walls
67a, 67b, which, as discussed above, increases from a minimum
immediately adjacent ridge 57 and proximal portion 61 of capillary
channel 25 to a maximum height d3 at lateral portions 77a, 77b of
first and second proximal walls 67a, 67b.
[0085] A height d4 of a gap between first and second junctions 73a,
73b of upper surface 53 of lower substrate 21 and lower surface 37
of filter 33 (FIG. 5) is typically at least as large as, e.g.,
larger than, height d3 at lateral portions 77a, 77b of first and
second proximal walls 67a, 67b. Height d4 is typically at least
about 30 microns, at least about 50 microns, at least about 75
microns, at least about 100 microns, at least about 150 microns, at
least about 200 microns, or at least about 250 microns. Height d4
may be about 600 microns or less, about 400 microns or less, about
350 microns or less, about 300 microns or less, or about 275
microns or less. A height d5 between first and second hydrophobic
floor portions 71a, 71b of upper surface 53 of lower substrate 21
and lower surface 37 of filter 33 (FIG. 6a) may be about the same
as, e.g., the same as, height d4. Height d5 is typically constant
(but may also vary) proceeding laterally from first and second
junctions 73a, 73b of upper surface 53 of lower substrate 21 toward
first and second lateral walls 79a, 79b (FIGS. 6a, 6b, and 12).
[0086] A lateral distance d6 (FIG. 12) between first and second
opposed walls 63a, 63b and first and second junctions 73a, 73b is
typically at least about 1 mm, at least about 1.25 mm, at least
about 1.5 mm, at least about 1.75 mm, or at least about 2 mm.
Lateral distance d6 may be about 10 mm or less, about 7.5 mm or
less, about 5 mm or less, about 3 mm or less, or about 2.5 mm or
less. A distance d7 (FIG. 12) between distal wall 79c and a distal
wall 81 is typically about the same as, e.g., the same, as distance
d6.
[0087] With reference to, for example, FIGS. 11 and 12, peripheral
walls 79a, 79b, 79c, 79e define a periphery of a recess 86 in a
surface 53 of lower substrate 21. First, second, and third
hydrophobic floor portions 71a, 71b, 71c and first and second
sloping floor portions 69a, 69b define a floor of recess 86. First,
second, and third hydrophobic floor portions 71a, 71b, 71c and
first and second sloping floor portions 69a, 69b are spaced apart
from, e.g., below, portions of upper surface 53 of lower substrate
21 adjacent to recess 86 along an axis a2 normal to upper surface
53 and/or along an axis al normal to lower surface 45 of upper
substrate 23 (FIG. 13) when upper substrate is secured with respect
to lower substrate 21. In embodiments, at least about 50%, at least
about 75%>, at least about 90%>, at least about 95%>, or
essentially all of the area of first, second, and third hydrophobic
floor portions 71a, 71b, 71c and first and second sloping floor
portions 69a, 69b are spaced apart from, e.g., below, portions of
upper surface 53 of lower substrate 21 adjacent to recess 86.
[0088] Upper surface 53 of lower substrate 21 further defines a
groove 87 extending from a proximal portion 93 (same as proximal
floor 61), a reagent portion 95, a ramp portion 97, a detection
portion 99, and a distal portion 101. First, second, and third
hydrophobic floor portions 71a, 71b, 71c and first and second
sloping floor portions 69a, 69b are spaced apart from, e.g., below,
groove 87. In embodiments, at least about 50%>, at least about
75%>, at least about 90%>, at least about 95%>, or
essentially all of the area of first, second, and third hydrophobic
floor portions 71a, 71b, 71c and first and second sloping floor
portions 69a, 69b are spaced apart from, e.g., below, at least a
portion of groove 87, e.g., at least 50%>, at least about 75%o,
at least about 90%>, essentially all of groove 87. In
embodiments, at least about 50%), at least about 75%>, at least
about 90%>, at least about 95%>, or essentially all of the
area of first, second, and third hydrophobic floor portions 71a,
71b, 71c and first and second sloping floor portions 69a, 69b are
spaced apart from, e.g., below, at least a portion of groove 87
disposed proximal to detection zone 43, e.g., at least 50%, at
least about 75%, at least about 90%), essentially all of groove 87
disposed proximal to detection zone 43.
[0089] Channel 25 has a width of about 900 microns between reagent
portion 95 and distal portion 101. In embodiments, the width of
channel 25 is at least about 500 microns, at least about 750
microns, at least about 850 microns. The width of channel 25 may be
about 2500 microns or less, about 2100 microns or less, or about
1750 microns or less.
[0090] Detection zone 43 of microfluidic device 20 typically
includes a one or more capture zones. A capture zones is comprised
of reagents, such as receptors, or devices, such as electrodes
which bind or react with one or more components from the liquid
sample and/or reagents combined with the liquid sample. Such
binding or reaction is related to the presence or amount of target
ligand in the sample. One or more detection zones 43 can be placed
in the capillary channel 25 to measure the presence or amount of
one or more target ligands. Reagent portion 95 of microfluidic
device 20 includes one or more reagents that facilitate detection
of one or more targets in a liquid sample. Exemplary reagents and
techniques for depositing such reagents in reagent portion 95 are
described in U.S. Pat. No. 7,824,611, which is incorporated herein
by reference.
[0091] For example, as described in U.S. Pat. No. 7,824,611,
texture on a device surface can facilitate drying of reagents on
the surface during preparation of the device, as well as uniform
placement of dried reagents on the surface as follows. A liquid
reagent-containing fluid is placed in contact with the textured
surface, and small reagent fluid menisci form adjacent each texture
structure. Absent the presence of texture, the fluid would tend to
form larger menisci at corners of the entire chamber, which when
dried would produce a nonuniform layer of dried reagent. When
texture structures are designed into the device, the presence of
numerous small menisci leads to a more uniform layer of reagent
that is dried throughout the chamber.
[0092] In embodiments, reagents, includes receptors which bind or
react with one or more components from the liquid sample and/or
reagents combined with the liquid sample. The reagents, such as
receptors, may be immobilized on the surface of the device through
covalent bonds or through adsorption. One embodiment is to
immobilize receptor coated latex particles, for example of
diameters ranging from about 0.1 .mu.l to 5 .mu..eta.. In addition,
particles termed "nanoparticles" can also be coated with receptor
and the resulting nanoparticles can be immobilized to the device
through adsorption or covalent bonds. Nanoparticles are generally
composed of silica, zirconia, alumina, titania, ceria, metal sols,
and polystyrene and the like and the particle sizes range from
about 1 nm to 100 nm. The benefit of using nanoparticles is that
the surface area of the protein coating the nanoparticle as a
function of the solids content is dramatically enhanced relative to
larger latex particles. In one embodiment, the receptors bind to
the surface through electrostatic, hydrogen bonding and/or
hydrophobic interactions. Electrostatic, hydrogen bonding and
hydrophobic interactions are discussed, for example, in
Biochemistry 20, 3096 (1981) and Biochemistry 29, 7133 (1990). For
example, the surface can be treated with a plasma to generate
carboxylic acid groups on the surface. The receptor coated latex
particles are preferably applied in a low salt solution, for
example, 1-20 mM, and at a pH which is below the isoelectric point
of the receptor. Thus, the negative character of the carboxylic
acid groups and the positive charge character of the receptor latex
will result in enhanced electrostatic stabilization of the latex on
the surface. Hydrogen bonding and hydrophobic interactions would
also presumably contribute to the stabilization and binding of the
receptor latex to the surface. Magnetic fields may also be used to
immobilize particles which are attracted by the magnetic field.
[0093] As discussed above, textured surfaces can serve to provide
additional surface area which allows for a higher density of assay
reagents to be immobilized thereon. Furthermore, a textured
surface, or other surface modifications, can be provided to affect
the flow characteristics of a fluid on or within the surface. For
example, as disclosed herein a surface can be provided with
hydrophobic regions to diminish the extent of fluid flow in the
hydrophobic region, textures can be used that provide for a more
uniform distribution of dried reagents on the surface, textures can
be provided to modify the configuration of the meniscus at the
fluid flow front, or textures can be used that provide the
capillary driving force for movement of fluid within the
surface.
[0094] Reagents include signal producing reagents. Such reagent
include for example, a receptor specific for a target ligand
adsorbed to a colloidal metal, such as a gold or selenium sol.
Other reagents include ligand analogue-ligand complement conjugates
to each target ligand and receptors adsorbed to latex particles
with diameters of, for example, 0.1 .mu..eta. to 5 .mu..eta. to
each target ligand, in appropriate amounts, for example, as taught
by U.S. Pat. Nos. 5,028,535 and 5,089,391. The ligand complement on
the conjugate can be any chemical or biochemical which does not
bind to the receptors for the target ligands. Additional reagents
include detergents for a washing step.
[0095] As used herein a target ligand refers to the binding partner
to one or more receptors. Synonyms for target ligand are analyte,
ligand or target analyte.
[0096] As used herein in a ligand refers to the binding partner to
one or more ligand receptor(s). A synonym for ligand is analyte.
For example, a ligand can comprise an antigen, a nucleotide
sequence, lectin or avidin.
[0097] As used herein a ligand analogue refers to a chemical
derivative of the target ligand which may be attached either
covalently or noncovalently to other species, for example, to the
signal development element. Ligand analogue and target ligand may
be the same and both generally are capable of binding to the ligand
receptor. Synonyms for ligand analogue are analyte analogue or
target analyte analogue.
[0098] As used herein a ligand analogue conjugate refers to a
conjugate of a ligand analogue and a signal development element. A
ligand analogue conjugate can be referred to as a labeled ligand
analogue.
[0099] As used herein a receptor refers to a chemical or
biochemical species capable of reacting with or binding to target
ligand, typically an antibody, a binding fragment, a complementary
nucleotide sequence, carbohydrate, biotin or a chelate, but which
may be a ligand if the assay is designed to detect a target ligand
which is a receptor. Receptors may also include enzymes or chemical
reagents that specifically react with the target ligand. A receptor
can be referred to as a reagent or a binding member. A receptor
which is neither a labeled receptor nor an immobilized receptor can
be referred to as an ancillary receptor or an ancillary binding
member. For example, a receptor can comprise an antibody.
[0100] As used herein a ligand receptor conjugate refers to a
conjugate of a ligand receptor and a signal development element;
synonyms for this term include binding member conjugate, reagent
conjugate, labeled reagent or labeled binding member.
[0101] As used herein a ligand complement refers to a specialized
ligand used in labeling ligand analogue conjugates, receptors,
ligand analogue constructs or signal development elements.
[0102] As used herein a ligand complement receptor refers to a
receptor for ligand complement and a ligand analogue-ligand
complement conjugate refers to a conjugate including a ligand
analogue and a ligand complement.
[0103] Ramp portion 97 of microfluidic device has a length along
capillary channel 25 of 3 mm and a pitch of 14 microns per mm
proceeding distally along capillary channel 25. The positive pitch
decreases a height of capillary channel 25 from 75 microns prior to
ramp portion 97 to 33 microns distal to ramp portion 97. In
embodiments, a ramp portion may have a length of at least about 0.5
mm, at least about 1 mm, at least about 1.5 mm A ramp portion may
have a length of about 5 mm or less, about 4 mm or less, about 3.5
mm or less, about 3 mm or less, about 2 mm or less, about 1.5 mm or
less. In embodiments, a pitch of the ramp portion may be at least
about 10 microns per mm, at least about 12 microns per mm, at least
about 14 microns per mm at least about 17.5 microns per mm The
pitch of the ramp portion may be about 30 microns per mm or less,
about 25 microns per mm or less, about 20 microns per mm or less.
In embodiments, the ramp portion is about 1 mm long with a pitch of
22 microns per mm proceeding distally along capillary channel 25
and decreases the height of the channel from about 55 microns
proximal of the ramp portion to about 33 microns distal to the ramp
portion.
[0104] In use, microfluidic device 20 is typically first removed
from a sealed packaging material in which the device has been
transported and/or stored. The packaging material is typically
formed of a material that is resistant to an exchange of gas from
an interior of the packaging material to the ambient gas
surrounding the packaging material. After removal from the
packaging, the microfluidic device is inserted into a reader (not
shown) configured to operate microfluidic device 20 to detect one
or more targets in a liquid sample, e.g., a blood or urine
sample.
[0105] In embodiments, the liquid sample is a blood sample, e.g., a
blood sample obtained from a finger of a human being. The liquid
sample may have a total volume of about 75 microliters or less, 50
microliters or less, 30 microliters or less, 20 microliters or
less, such as about 15 microliters or less, such as about 10
microliters or less. The liquid sample may be combined with
reagent, e.g., a liquid and/or a dry reagent, prior to introducing
the liquid sample to the microfluidic device.
[0106] With reference to FIGS. 15-19, the reader includes a syringe
pump 101 that makes a fluidic connection, e.g., a gas-tight seal,
with respect to distal vent 29 of capillary channel 25 of
microfluidic device 20.
[0107] Liquid sample is then applied to upper surface 35 of filter
33 via port 31. Filtered liquid (e.g., liquid that emerges from
lower surface 37 of filter 33 after being applied to upper surface
35 within port 31) passes into first and second cavity portions
sample cavities 75a, 75b. A high capillarity experienced by
filtered liquid at first and second where lower surface 37 of
filter contacts first and second opposed walls 63a, 63b draws
liquid out of filter 33 and into sample cavities 75a, 75b, e.g.,
generally along path p2 and a path p3. First and second hydrophobic
floor portions 71a, 71b, 71c prevent filtered liquid from passing
beyond first and second junctions 73a, 73b and into peripheral
cavity 85.
[0108] Filtered liquid moves within sample cavities 75a, 75b by
capillary action to proximal opening 27 of capillary channel 25 and
moves by capillary action at least a portion of the way into
capillary channel 25. With the pump in fluidic connection with
distal vent 29 of capillary channel 25, a volume of gas acting upon
a distal gas-liquid interface 107 of the filtered liquid is
confined within a volume determined by the volume of capillary
channel 25 distal to interface 107 and a dead volume of the pump.
As distal gas-liquid interface 107 moves distally along channel 25,
the volume of the confined gas decreases and the pressure of the
confined gas acting upon the distal gas-liquid interface 107
increases by an amount corresponding to decreased volume. The total
volume of gas confined distal to opening 27 of capillary channel 25
is about 25 microliters. By total volume of gas it is meant a
volume including the volume of gas in channel 25 and the volume of
gas within pump 101 in communication with channel 25. In
embodiments, the total volume of gas is about 50 microliters or
less, about 35 microliters or less, about 30 microliters or less,
or about 25 microliters or less. The total volume of gas may be at
least about 10 microliters, at least about 15 microliters, at least
about 20 microliters. The volume of channel 25 is typically at
least about 7.5 microliters, at least about 10 microliters, or at
least about 12.5 microliters. The volume of channel 25 may be about
25 microliters or less, about 20 microliters or less, about 17.5
microliters or less, or about 15 microliters or less.
[0109] Before distal gas liquid interface 107 of the filtered
liquid contacts reagent portion 41 of capillary channel 25 the gas
pressure acting on distal gas liquid interface 107 increases such
that the capillary force experienced by the filtered liquid is
insufficient to move the filtered liquid further along the
capillary channel (FIG. 15).
[0110] The pressure of the gas acting upon the distal gas liquid
interface of the filtered liquid is determined using a pressure
sensor 103 in communication with the volume of gas enclosed distal
to distal gas-liquid interface 107. Pressure sensor 103 may be
configured to determine an absolute pressure of the enclosed gas,
e.g., a pressure with respect to a pressure of ambient gas, e.g., a
pressure of gas acting upon outer surfaces of microfluidic device
20.
[0111] The reader actuates syringe pump 101 to increase a volume of
the enclosed gas by an amount sufficient to decrease the gas
pressure acting on distal gas-liquid interface 107. Capillary
action draws the filtered liquid further along capillary channel
107 until distal gas liquid interface 107 contacts and then passes
beyond reagent portion 41. A gas pressure acting on distal gas
liquid interface 107 increases such that the capillary force
experienced by the filtered liquid is insufficient to move the
filtered liquid further along the capillary channel (FIG. 16).
[0112] After a period of time sufficient to permit the filtered
liquid and reagent to react and/or combine with a reagent in
reagent portion 41, the reader actuates syringe pump 101 to
increase the volume of the enclosed gas by an amount sufficient to
decrease the gas pressure acting on distal gas-liquid interface
107. Capillary action draws the filtered liquid further along
capillary channel 107 until distal gas liquid interface 107
contacts and then passes beyond detection zone 42. A gas pressure
acting on distal gas liquid interface 107 increases such that the
capillary force experienced by the filtered liquid is insufficient
to move the filtered liquid further along the capillary channel
(FIG. 17).
[0113] Reagent and target (if any) combine and/or react with
detection zone 43, e.g., by binding a detectable label to a binding
agent present in detection zone 43. After a period of time
sufficient to permit the filtered liquid and reagent to react
and/or combine with detection zone 43, the reader actuates syringe
pump 101 to increase the volume of the enclosed gas by an amount
sufficient to decrease the gas pressure acting on distal gas-liquid
interface 107. Capillary action draws the filtered liquid further
along capillary channel 107 until substantially all reagent from
reagent zone 43 that has not bound to detection zone 43 has moved
distal of detection zone 43 along capillary channel 25 (FIG. 18).
The pump may be actuated to cause the filtered liquid to move at a
higher speed along capillary channel 25 than for the actuation that
causes the filtered liquid to contact reagent portion 41 and/or for
the actuation that causes the filtered liquid to contact detection
zone 43.
[0114] The reader is actuated to determine the presence and/or
amount of one or more targets. The reader may include a biosensor
to determine the presence and/or amount of the one or more targets.
The biosensor may be an electrochemical, optical, electro-optical,
or acoustic mechanical detector. For example, the reader may
include a light source and light detector to determine the presence
and/or amount of detectable label bound in detection zone 43. The
reader may be configured to disconnect gasket 105 of pump 101 prior
to the step of detecting.
[0115] In use, the total volume of filtered liquid that is drawn
into capillary channel 25 is less than a total volume of the
capillary channel so that filtered liquid does not exit vent 29 of
micro fluidic device 20.
[0116] A distal portion of capillary channel 25 includes a distal
stop 111 having a capillary break 113. Liquid reaching capillary
break 113 experiences a reduced capillary force reducing a tendency
of the liquid from advancing further along capillary channel 25. A
depth of distal stop 111 is 300 microns. The depth of distal stop
111 is typically at least about 200 microns, at least about 250
microns, or at least about 275 microns. The depth of distal stop
111 may be about 1000 microns or less, about 750 microns or less,
or about 500 microns or less. A width of channel 25 within distal
stop 111 is about 1 mm Typically, the width of channel 25 within
distal stop 111 is at least about 500 microns, or at least about
750 microns. The width of channel 25 within distal stop 111 may be
about 2500 microns or less, about 1500 microns or less or about
1250 microns or less.
[0117] Hydrophobic surfaces of microfluidic device 20, e.g., first,
second, and third hydrophobic floor portions 71a, 71b, 71c, may be
made hydrophobic using hydrophobic compounds, such as aliphatic
and/or aromatic compounds and various inks and polymers and the
like. The compounds are generally dissolved in organic solvents or
mixtures of aqueous and organic solvents. U.S. Pat. No. 7,824,611
(incorporated by reference herein) discloses suitable techniques
(such as ink jet printing, spraying, silk screening, drawing,
embossing and the like) that permit the application of hydrophobic
zones on or within surfaces.
[0118] For example, U.S. Pat. No. 7,824,611 discloses several
techniques which may be utilized to make a surface hydrophobic. For
surfaces made hydrophilic, hydrophobic zones can be created by
application of organic solvents that destroy the plasma treatment
or denature the proteins, to recreate a native hydrophobic plastic
surface or to create a hydrophobic surface by the denatured
proteins, or by local heating of the surface using focused laser
beams to destroy the hydrophilic nature of the surface.
Alternatively, one can mask hydrophobic areas before creating a
hydrophilic area by any of the foregoing methods. The areas can be
masked by objects such as a template or can be masked by materials
that are applied to the surface and then are subsequently
removed.
[0119] In one embodiment a hydrophobic surface may be created by
beginning with a hydrophobic surface, such as are found on native
plastics and elastomers (polyethylene, polypropylene, polystyrene,
polyacrylates, silicon elastomers and the like). In an embodiment,
hydrophobic particles, may be deposited upon a surface. Such
particles include latex particles, for example polystyrene latexes
with diameters of between about 0.01 .mu..eta. and 10 .mu..eta. or
hydrophobic polymers, such as polypropylene, polyethylene,
polyesters and the like. In another embodiment, a hydrophobic
surface may be created by application of a hydrophobic chemical,
such as an ink or a long chain fatty acid, or a hydrophobic decal
to the desired zone. The hydrophobic chemical or decal is generally
not soluble or is poorly soluble in the reaction mixture. In yet
another preferred embodiment, the hydrophobic surface may be formed
by changing a hydrophilic surface to a hydrophobic surface. For
example, hydrophobic surfaces made hydrophilic by plasma treatment
can be converted back to a hydrophobic surface by the application
of solvents, ultraviolet light or heat and the like. These
treatments can act to change the molecular structure of the
hydrophilic, plasma modified surface back to a hydrophobic
form.
[0120] As discussed above, hydrophobic compounds, such as aliphatic
and/or aromatic compounds and various inks and polymers and the
like can be used for the creation of hydrophobic zones in
accordance with the invention. The compounds are generally
dissolved in organic solvents or mixtures of aqueous and organic
solvents. One skilled in the art will recognize that a variety of
techniques known in the art (such as ink jet printing, spraying,
silk screening, drawing, embossing and the like) are techniques
that permit the application of hydrophobic zones on or within
surfaces.
[0121] Components of microfluidic device 20 (e.g., lower and upper
substrates 21,23) can be prepared from copolymers, blends,
laminates, metallized foils, metallized films or metals.
Alternatively, microfluidic device components can be prepared from
copolymers, blends, laminates, metallized foils, metallized films
or metals deposited one of the following materials: polyolefms,
polyesters, styrene containing polymers, polycarbonate, acrylic
polymers, chlorine containing polymers, acetal homopolymers and
copolymers, cellulosics and their esters, cellulose nitrate,
fluorine containing polymers, polyamides, polyimides,
polymethylmethacrylates, sulfur containing polymers, polyurethanes,
silicon containing polymers, glass, and ceramic materials. Lower
and upper substrates 21,23 may be secured with respect to one
another the various recesses and grooves sealed and the capillary
cavities and channels formed by a number of techniques, including
but not limited to, gluing, welding by ultrasound, riveting and the
like.
[0122] While a number of exemplary aspects and embodiments have
been discussed above, those of skill in the art will recognize
certain modifications, permutations, additions and sub-combinations
thereof. It is therefore intended that the following appended
claims and claims hereafter introduced are interpreted to include
all such modifications, permutations, additions and
sub-combinations as are within their true spirit and scope.
* * * * *