U.S. patent application number 10/521093 was filed with the patent office on 2005-11-17 for flow device.
Invention is credited to Neyer, David W., Paul, Philip H., Rehm, Jason E..
Application Number | 20050252772 10/521093 |
Document ID | / |
Family ID | 30115152 |
Filed Date | 2005-11-17 |
United States Patent
Application |
20050252772 |
Kind Code |
A1 |
Paul, Philip H. ; et
al. |
November 17, 2005 |
Flow device
Abstract
Liquid flow devices, particularly microfluidic devices,
containing solid porous materials. Flow in the devices can be
pressure-driven flow and/or electroosmotic flow. The porous
materials are preferably pre-shaped, for example divided from a
sheet of porous material, so that they can be assembled with
liquid-impermeable barrier materials around them. The devices can
for example be prepared by lamination. A wide variety of devices,
including mixing devices, is disclosed. A mixing device is
illustrated in FIG. 23.
Inventors: |
Paul, Philip H.; (Livermore,
CA) ; Neyer, David W.; (Castro Valley, CA) ;
Rehm, Jason E.; (Alameda, CA) |
Correspondence
Address: |
SHELDON & MAK, INC
225 SOUTH LAKE AVENUE
9TH FLOOR
PASADENA
CA
91101
US
|
Family ID: |
30115152 |
Appl. No.: |
10/521093 |
Filed: |
January 12, 2005 |
PCT Filed: |
July 16, 2003 |
PCT NO: |
PCT/US03/22306 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10521093 |
Jan 12, 2005 |
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10198223 |
Jul 17, 2002 |
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Current U.S.
Class: |
204/450 ;
204/600 |
Current CPC
Class: |
G01N 30/461 20130101;
B01L 2300/0681 20130101; B01L 3/502753 20130101; F04B 19/006
20130101; G01N 2030/347 20130101; B01L 2300/0645 20130101; G01N
2030/027 20130101; G01N 30/6065 20130101; Y10T 156/1046 20150115;
G01N 27/44791 20130101; B01F 5/0682 20130101; G01N 2030/326
20130101; F16K 99/0001 20130101; G01N 2030/528 20130101; G01N
2030/525 20130101; B01L 2300/0877 20130101; F04B 43/043 20130101;
B01D 61/18 20130101; B01L 2300/0887 20130101; G01N 30/6095
20130101; G01N 2030/285 20130101; B01L 3/5023 20130101; B01L
2400/0418 20130101; B01L 2300/0654 20130101; B01F 13/0076 20130101;
B01L 3/502707 20130101; F16K 99/0049 20130101; B01F 5/0692
20130101; F16K 99/0025 20130101; B01F 15/0201 20130101; F04B 43/06
20130101; B01F 15/0232 20130101 |
Class at
Publication: |
204/450 ;
204/600 |
International
Class: |
G01N 027/27 |
Claims
1. A novel flow device comprising a conduit which comprises (1) a
barrier member, and (2) a porous flow member (PFM) which (i)
comprises a solid porous material, and (ii) is enclosed by the
barrier member so that the PFM comprises a flowthrough section
through which there can be electroosmotic and/or pressure-driven
flow of a liquid; the device having at least one of the following
characteristics (A) the barrier member comprises a plurality of
laminar barrier layers which have been laminated together around
the PFM; (B) the PFM is a pre-shaped PFM, or, if the device
comprises more than one said conduit, the PFM in at least one of
said conduits, e.g. the PFM in each of said conduits, is a
pre-shaped PFM; (C) the PFM is laminar and lies in a first plane,
and the device comprises a conduit which (i) is in fluidic
communication with the PFM, and (ii) lies in the first plane or in
a plane substantially parallel to the first plane; (D) the PFM is
laminar and lies in a first plane, and the device comprises an
electrode which (i) when the device is filled with an ionic liquid,
is in electrical communication with the PFM, and (ii) lies in the
first plane or in a plane substantially parallel to the first
plane; (E) the device comprises at least four laminar layers, at
least two of the laminar layers comprising a laminar PFM; (F) the
device comprises (1) a first said conduit comprising a first
barrier member and a first PFM which comprises a first flowthrough
section and a first transfer section, the first flowthrough section
being enclosed by the first barrier member so that fluid can flow
the first flowthrough section and into the first transfer section,
(2) a second said conduit comprising a second barrier member and a
second PFM which comprises a second flowthrough section and a
second transfer section, the second flowthrough section being
enclosed by the second barrier member so that fluid can flow
through the first flowthrough section and into the second transfer
section; the first and second transfer sections (a) having
overlapping surfaces which (i) contact each other directly, or (ii)
are adjacent to each other and are separated from each other by a
gap which optionally is filled by a porous material, and (b) being
enclosed by a third barrier member so that liquids flowing into the
first and second transfer sections are mixed together; (G) the
device comprises (1) a first said conduit in which the flowthrough
section of the PFM is a first laminar PFM which lies in a first
plane, (2) a second said conduit in which the flowthrough section
of the PFM is a second laminar PFM which lies in a second plane
parallel to first plane and which overlaps the flowthrough section
of the first conduit; (H1) the PFM comprises (a) a first layer
which is composed of a first porous material, (b) a second layer
which is in contact with the first layer along an interface and
which is composed of second porous material, the first porous
material having a first pore size and second porous material having
a second pore size which is larger than the first pore size, or the
pore geometry of the first porous material at the interface being
such that particles above a certain pore size will not pass through
the interface, and the device further comprises (3) a fluidic inlet
which communicates with the second layer but not with the first
layer, (4) a first fluidic exit which communicates with the first
layer but not with the second layer, and (5) a second fluidic exit
which communicates with second layer but not with the first layer;
(H2) the PFM is composed of a porous material having an asymmetric
pore size distribution such that the pore size increases, regularly
or irregularly, across the thickness of the PFM, whereby the PFM
has a first surface composed of relatively small pores and a second
surface composed of relatively large pores, and the device further
comprises (3) a fluidic inlet which communicates with the PFM, (4)
a first fluidic exit which communicates with the first surface but
not with the second surface, and (5) a second fluidic exit which
communicates with second surface but not with the first surface;
(I) the device comprises (1) a first said conduit in which the PFM
comprises a first solid porous material having a first zeta
potential, the first conduit having a first inner end and first
outer end, (2) a second said conduit in which the PFM comprises a
second solid porous material having a second zeta potential which
is substantially different from the first zeta potential, the
second conduit having a second inner end and a second outer end,
(3) an inner fluidic junction which communicates with the first and
second inner ends, (4) a first outer fluidic junction which
communicates with the first outer end, and (5) a second outer
fluidic junction which communicates with the second outer end; (J)
the device comprises (1) a first said conduit in which the
flowthrough section of the PFM terminates at a first
cross-sectional end surface; (2) a second said conduit in which the
flowthrough section of the PFM terminates at a second
cross-sectional end surface which contacts the first surface at a
butt junction; and (3) an auxiliary porous member which contacts
the sides of the first and second PFMs and bridges the butt
junction; (K) the PFM has a cross-section having a thickness of
less than 4000 microns; (L) the PFM has a cross-section having an
equivalent diameter of less than 4000 microns; and (M) the conduit
is rigid.
2. A device according to claim 1 which has characteristic (A) and
wherein the barrier layers have been laminated together with the
aid of heat and pressure.
3. A device according to claim 1 which has characteristic (B) and
which has at least one of the following characteristics (B1) the
PFM was divided from a sheet of porous material and has a
rectangular cross-section; (B2) the PFM was treated, before being
contacted by any of the barrier member, to change the electrical or
chemical properties of at least some of its surfaces; (B3) the PFM
includes at least one transfer section which extends from the
flowthrough section by a distance of up to 4 mm; (B4) the PFM has a
constant thickness and a varying width; and (B5) the PFM is a strip
in the form of a smooth or angular spiral or zigzag.
4. A device according to claim 1 wherein the PFM comprises a
liquid-impermeable tube filled with the solid porous material.
5. A device according to claim 1, which has characteristic (F) and
which has at least one of the following characteristics (F1) at
least one of the first and second PFMs comprises a flowthrough
section having a width w.sub.1 and a transfer section which
comprises (i) a flared section in which the width increases to
w.sub.3, w.sub.3 being from 2 to 4 times w.sub.1, and which has a
length from 0.3 to 0.7 times w.sub.3, and (ii) a pre-mixing section
which is adjacent to the flared section and which has the width
w.sub.3; (F2) the device includes a mixing member which (i) is
composed of a porous material, and (ii) comprises an intermediate
section which lies between and contacts the first and second
transfer sections, and a continuation section which extends from
the first and second transfer sections; (F3) at least one of the
PFMs is divided into two parts, each part having a flowthrough
section and a transfer section, and the transfer sections of the
first and second PFMs are interleaved with each other; (F4) the
area A between the overlapping transfer sections has an equivalent
diameter d.sub.transfer such that each of the ratios
d.sub.transfer/t.sub.1 and d.sub.transfer/t.sub.2 is at least 5;
(F5) liquid flows in the first transfer section along a first flow
axis and liquid flows in the second transfer section along a second
flow axis, and the liquid flow in the second transfer section has a
component which is parallel to the first flow axis and is at least
50% of the flow.
6. A device according to claim 1 which has characteristic (G) and
which has at least one of the following characteristics (G1) the
first and second laminar PFMs overlap each other in an overlap
area, and one of the barrier members is an intermediate barrier
member which lies between the first and second PFMs, and which,
over at least 70% of the overlap area, prevents liquid from flowing
between the first PFM and second PFM. (G2) the device comprises a
junction which is in fluidic communication with the first and
second PFMs; (G3) the device comprises at least 3 laminar PFMs
which lie in parallel but different planes.
7. A device according to claim 1, which has characteristic (I) and
which has at least one of the following characteristics (I1) the
first and second zeta potentials have an opposite sign; (I2) the
first and second zeta potentials differ by at least 10 mV; and (I3)
the device includes (i) a first chamber communicating with the
inner fluidic junction and having a wall which comprises a flexible
diaphragm, and (ii) a second chamber having a wall which comprises
the flexible diaphragm.
8. A device according to claim 1 which has characteristic (J) and
in which the auxiliary member is composed of the porous material
having a pore size greater than the pore size of either of the
PFMs.
9. A method of causing electroosmotic flow which comprises applying
an electrical potential to an ionic liquid in a flow device as
claimed in claim 1.
10. A method of causing liquid flow which comprises applying
pressure to a liquid in a flow device as claimed in claim 1.
11. A method of preparing a conduit which comprises (1) a barrier
member, and (2) a porous flow member (PFM) which (i) comprises a
solid porous material, and (ii) is enclosed by the barrier member
so that the PFM comprises a flowthrough section through which there
can be electroosmotic and/or pressure-driven flow of a liquid; the
method comprising placing the flowthrough section of the PFM
between a plurality of barrier layers, and laminating the barrier
layers together to form the barrier member.
12. A method according to claim 11 wherein the lamination is
carried out with the aid of heat and pressure.
13. A method according to claim 11 wherein at least one of a fluid
conduit and an electrode is placed between the barrier layers
before the barrier layers are laminated together.
14. A method of preparing a conduit which comprises (1) a barrier
member, and (2) a porous flow member (PFM) which (i) comprises a
solid porous material, and (ii) is enclosed by the barrier member
so that the PFM comprises a flowthrough section through which there
can be electroosmotic and/or pressure-driven flow of a liquid; the
method comprising placing the flowthrough section of the PFM in a
mold, placing a hardenable liquid composition in the mold around
the PFM, and hardening the composition to encapsulate the
flowthrough section.
Description
RELATED APPLICATION DATA
[0001] This application is a continuation-in-part of our
application Ser. No. 10/198,223, filed Jul. 17, 2002 (Docket No.
14138), the entire disclosure of which is incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] This invention relates to flow devices.
BACKGROUND OF THE INVENTION
[0003] Many systems make use of flow devices, including micro-flow
devices, which include a conduit through which there is
electroosmotic and/or pressure-driven flow of a liquid. Such
systems include, for example, chromatography systems, including
high-performance liquid chromatography (HPLC) systems,
electrokinetic (also known as electroosmotic) pumping systems,
chemical processing systems, and electrophoric separation systems.
Reference may be made for example to U.S. Pat. Nos. 6,074,725,
6,156,273, 6,176,962 and 6,287,440, and International Publication
Nos. WO 99/16162 and WO 02/101474, the entire disclosures of which
are incorporated herein by reference for all purposes.
[0004] It is often desirable, for example in order to increase the
surface-to-volume ratio of the conduit and/or to provide different
surface chemistry, to fill the conduit with a fluid-permeable
packing material. In the known methods, the packing material is
placed in the conduit (i) in the form of loose particles or (ii) as
a liquid polymeric composition which is cured in the conduit. These
methods suffer from various disadvantages, for example the need to
prevent the packing materials from falling out of the channel
and/or falling into adjacent channels or other components;
shrinkage of the polymeric compositions when they cure; and the
difficulty of changing the surface chemistry of a packing material
after it has been placed in the channel.
SUMMARY OF THE INVENTION
[0005] We have discovered, in accordance with the present
invention, a wide variety of novel flow devices which make use of
solid porous materials as liquid flow media. The invention is
particularly useful when pre-shaped porous materials are used to
provide conduits in flow devices, but the invention is not limited
to pre-shaped porous materials. The term "pre-shaped" is used to
denote a member having a shape before it is enclosed by the barrier
member, as distinct from a member which is shaped within the
conduit. The porous materials are often laminar, but can be of any
shape. The term "laminar" is used in this specification to include,
but is not limited to, planar. Thus, a laminar member can for
example be a planar member of constant thickness, a planar member
of regularly or irregularly varying thickness, a curved member of
constant thickness, or a curved member of regularly or irregularly
varying thickness. The periphery of a laminar member can be of any
shape, and a laminar member can comprise one or more windows of any
shape, i.e. areas within the periphery in which there is no
material.
[0006] In a first aspect, this invention provides a novel flow
device comprising a conduit which comprises
[0007] (1) a barrier member, and
[0008] (2) a porous flow member (PFM) which
[0009] (i) comprises a solid porous material, and
[0010] (ii) is enclosed by the barrier member so that the PFM
comprises a flowthrough section through which there can be
electroosmotic and/or pressure-driven flow of a liquid;
[0011] the device having at least one of the following
characteristics
[0012] (A) the barrier member comprises a plurality of laminar
barrier layers which have been laminated together around the
PFM;
[0013] (B) the PFM is a pre-shaped PFM, or, if the device comprises
more than one said conduit, the PFM in at least one of said
conduits, e.g. the PFM in each of said conduits, is a pre-shaped
PFM;
[0014] (C) the PFM is laminar and lies in a first plane, and the
device comprises a conduit which (i) is in fluidic communication
with the PFM, and (ii) lies in the first plane or in a plane
substantially parallel to the first plane;
[0015] (D) the PFM is laminar and lies in a first plane, and the
device comprises an electrode which (i) when the device is filled
with an ionic liquid, is in electrical communication with the PFM,
and (ii) lies in the first plane or in a plane substantially
parallel to the first plane;
[0016] (E) the device comprises at least four laminar layers, at
least two of the laminar layers comprising a laminar PFM;
[0017] (F) the device comprises
[0018] (1) a first said conduit comprising a first barrier member
and a first PFM which comprises a first flowthrough section and a
first transfer section, the first flowthrough section being
enclosed by the first barrier member so that fluid can flow the
first flowthrough section and into the first transfer section,
[0019] (2) a second said conduit comprising a second barrier member
and a second PFM which comprises a second flowthrough section and a
second transfer section, the second flowthrough section being
enclosed by the second barrier member so that fluid can flow
through the first flowthrough section and into the second transfer
section;
[0020] the first and second transfer sections
[0021] (a) having overlapping surfaces which
[0022] (i) contact each other directly, or
[0023] (ii) are adjacent to each other and are separated from each
other by a gap which optionally is filled by a porous material,
and
[0024] (b) being enclosed by a third barrier member so that liquids
flowing into the first and second transfer sections are mixed
together;
[0025] (G) the device comprises
[0026] (1) a first said conduit in which the flowthrough section of
the PFM is a first laminar PFM which lies in a first plane,
[0027] (2) a second said conduit in which the flowthrough section
of the PFM is a second laminar PFM which lies in a second plane
parallel to first plane and which overlaps the flowthrough section
of the first conduit;
[0028] (H1) the PFM comprises
[0029] (a) a first layer which is composed of a first porous
material,
[0030] (b) a second layer which is in contact with the first layer
along an interface and which is composed of second porous
material,
[0031] the first porous material having a first pore size and
second porous material having a second pore size which is larger
than the first pore size, or the pore geometry of the first porous
material at the interface being such that particles above a certain
pore size will not pass through the interface, and the device
further comprises
[0032] (3) a fluidic inlet which communicates with the second layer
but not with the first layer,
[0033] (4) a first fluidic exit which communicates with the first
layer but not with the second layer, and
[0034] (5) a second fluidic exit which communicates with second
layer but not with the first layer;
[0035] (H2) the PFM is composed of a porous material having an
asymmetric pore size distribution such that the pore size
increases, regularly or irregularly, across the thickness of the
PFM, whereby the PFM has a first surface composed of relatively
small pores and a second surface composed of relatively large
pores, and the device further comprises
[0036] (3) a fluidic inlet which communicates with the PFM,
[0037] (4) a first fluidic exit which communicates with the first
surface but not with the second surface, and
[0038] (5) a second fluidic exit which communicates with second
surface but not with the first surface;
[0039] (I) the device comprises
[0040] (1) a first said conduit in which the PFM comprises a first
solid porous material having a first zeta potential, the first
conduit having a first inner end and first outer end,
[0041] (2) a second said conduit in which the PFM comprises a
second solid porous material having a second zeta potential which
is substantially different from the first zeta potential, the
second conduit having a second inner end and a second outer
end,
[0042] (3) an inner fluidic junction which communicates with the
first and second inner ends,
[0043] (4) a first outer fluidic junction which communicates with
the first outer end, and
[0044] (5) a second outer fluidic junction which communicates with
the second outer end;
[0045] (J) the device comprises
[0046] (1) a first said conduit in which the flowthrough section of
the PFM terminates at a first cross-sectional end surface;
[0047] (2) a second said conduit in which the flowthrough section
of the PFM terminates at a second cross-sectional end surface which
contacts the first surface at a butt junction; and
[0048] (3) an auxiliary porous member which contacts the sides of
the first and second PFMs and bridges the buff junction;
[0049] (K) the PFM has a cross-section having a thickness of less
than 4000 microns, for example less than 600 microns e.g. 20 to 600
microns, preferably 50 to 250 microns;
[0050] (L) the PFM has a cross-section having an equivalent
diameter of less than 4000 microns, for example less than 1500
microns;
[0051] (M) the conduit is rigid.
[0052] In a second aspect, this invention provides a method of
causing pressure-driven and/or electroosmotic flow through a device
according to the first aspect of the invention, the method
comprising
[0053] (1) applying an electrical potential to an ionic liquid in a
flow device according to the first aspect of the invention;
and/or
[0054] (2) exerting pressure on a liquid to cause it to flow
through the PFM of a flow device according to the first aspect of
the invention.
[0055] In method (1), the electrical potential can cause the ionic
liquid to flow through the PFM and/or through another component of
the device. Thus, in one embodiment of the invention, the PFM is
part of a bridge which serves as an electrical connection and there
is little or no electroosmotic flow of ionic liquid through the
PFM. The pressure in the device depends upon the way in which the
device is being used, and the device should be such that it will
operate safely at that pressure. For example, the device may be
such that it will operate at pressures up to about 15 psi (1
kg/cm.sup.2) or up to about 500 psi (35 kg/cm.sup.2).
[0056] In a third aspect, this invention provides a method of
preparing a flow device comprising a conduit, preferably a novel
conduit according to the first aspect of the invention, which
comprises
[0057] (1) a barrier member, and
[0058] (2) a porous flow member (PFM) which
[0059] (i) comprises a solid porous material, and
[0060] (ii) is enclosed by the barrier member so that the PFM
comprises a flowthrough section through which there can be
electroosmotic and/or pressure-driven flow of a liquid;
[0061] the method comprising
[0062] (A) laminating the flowthrough section of the PFM between a
plurality of barrier layers which are thus laminated together to
form the barrier member; or
[0063] (B) placing the flowthrough section of the PFM in a mold,
placing a hardenable liquid composition in the mold around the PFM,
and hardening the composition to encapsulate the flowthrough
section.
BRIEF DESCRIPTION OF THE DRAWINGS
[0064] The Figures in the accompanying drawings, which are
diagrammatic and not to scale, illustrate the invention. In the
Figures, a component appearing in more than one Figure is
identified by the same reference numeral in each Figure.
[0065] FIG. 1 is a plan view cross-section through a first device
of the invention,
[0066] FIGS. 2 and 3 are end view and side view cross-sections
taken on lines II-II and III-III of FIG. 1,
[0067] FIGS. 4-10 are partial cross-sections of other devices of
the invention;
[0068] FIGS. 11, 14 and 15 are plan views of PFMs for use in the
invention;
[0069] FIG. 12 is a cross-section on line XII-XII of FIGS. 11, 14
and 15;
[0070] FIG. 13 is a cross-section on line XIII-XIII of FIGS. 11 and
14;
[0071] FIG. 16 is a cross-section on line XVI-XVI of FIG. 15;
[0072] FIGS. 17-22 are cross-sections of other devices of the
invention,
[0073] FIG. 23 is a partial plan view cross-section through a
mixing device of the invention,
[0074] FIGS. 24 and 25 are end view and partial side view
cross-sections taken on lines XXIV-XXIV and XXV-XXV of FIG. 23,
[0075] FIG. 26 is a partial cross-section of another mixing device
of the invention;
[0076] FIG. 27 is a flow diagram of a two-stage mixing device of
the invention;
[0077] FIG. 28 is a partial plan view cross-section of a butt joint
between two PFMs; and
[0078] FIG. 29 is a partial side view cross-section on line
XXIX-XXIX of FIG. 28.
DETAILED DESCRIPTION OF THE INVENTION
[0079] In the Summary of the Invention above and in the Detailed
Description of the Invention, the Examples, and the claims below,
and in the accompanying drawings, reference is made to particular
features of the invention. It is to be understood that the
disclosure of the invention in this specification includes all
appropriate combinations of such particular features. For example,
where a particular feature is disclosed in the context of a
particular aspect or embodiment of the invention, or a particular
Figure, or a particular claim, that feature can also be used, to
the extent appropriate, in combination with and/or in the context
of other particular aspects and embodiments of the invention, and
in the invention generally.
[0080] The term "comprises", and grammatical equivalents thereof,
are used herein to mean that other components, ingredients, steps
etc. are optionally present in addition to the component(s),
ingredient(s), step(s) specifically listed after the term
"comprises". The term "at least" followed by a number is used
herein to denote the start of a range beginning with that number
(which may be a range having an upper limit or no upper limit,
depending on the variable being defined). For example "at least 1"
means 1 or more than 1, and "at least 80%" means 80% or more than
80%. The term "at most" followed by a number is used herein to
denote the end of a range ending with that number (which may be a
range having 1 or 0 as its lower limit, or a range having no lower
limit, depending upon the variable being defined). For example, "at
most 4" means 4 or less than 4, and "at most 40%" means 40% or less
than 40%. When, in this specification, a range is given as "(a
first number) to (a second number)" or "(a first number)-(a second
number)", this means a range whose lower limit is the first number
and whose upper limit is the second number. Where reference is made
herein to "first" and "second" components, e.g. first and second
conduits, this is generally done for identification purposes;
unless the context requires otherwise, the first and second
components can be the same or different.
[0081] PFM Shapes
[0082] The PFM can be straight, or regularly or irregularly curved,
the curve being a smooth curve and/or a succession of straight
sections at an angle to each other, in two or three dimensions.
When the PFM is obtained by division of a sheet of porous material,
it is easy to prepare PFMs of different shapes, for example
straight strips of constant or varying width, (e.g. with flared end
sections), strips which are part of a circle, strips which bend
through an angle of at least 360.degree., for example so that the
fluid path includes two or more sections which are substantially
parallel to each other and are substantially the same distance
(measured directly, not along the liquid flow path to) from the
inlet, e.g. strips in the form of a smooth or angular spiral or
zigzag, so that a long conduit becomes more compact. When the sheet
of porous material is flexible, a strip divided from it can be bent
so that it is no longer flat. The cross-section of the PFM (i.e. a
section at right angles to the local axis of the PFM) can be of any
shape. When the PFM is obtained by division of a sheet of porous
material, the cross-section will generally be rectangular
(including square), but may be more complex if the sheet is not of
constant thickness. One or both end sections of the PFM can have a
cross-section different from the intermediate portion of the PFM.
The end sections can be the same or different. The porous material
can extend out from the barrier member, for example by a distance
of 1 to 3 mm, be flush with the end of the barrier member, or
terminate within the barrier member.
[0083] PFM Materials
[0084] The PFM can comprise any solid porous material that will
provide a conduit having desired physical and electrical
properties. The PFM can consist of the porous material, or can also
include one or more auxiliary components having substantially no
effect on the fluid flow through the porous material. For example,
an auxiliary component can surround, or be surrounded by, or form a
layer adjacent to, the porous material, and can provide desired
strengthening, electrical or protective properties. Thus, in one
embodiment of the invention, the PFM is a tube of circular,
rectangular (including square) or other cross-section, e.g. a
conventional capillary tube, into which the porous material has
been placed. In this embodiment, because the tube is surrounded and
supported by the barrier material, there is no need to use the
specialized fittings currently needed to support the ends of such
tubes. In addition, the tube can be such that, if it was used
without the barrier material, it would be too delicate, for example
would not be sufficiently strong to withstand the internal pressure
in the tube.
[0085] The PFM can comprise a single layer of porous material or
two or more layers of porous material. When there are two or more
layers, the layers can be the same or different, and can be
arranged so that the liquid flows through them simultaneously or
sequentially, and/or, if the layers are different, so that
different components of the liquid follow different paths. The
layers can be in contact with each other or separated from each
other by an auxiliary member which may be permeable or impermeable
to the liquid or permeable to one or more components of the liquid
and impermeable to one or more other components of the liquid.
[0086] Many porous materials are readily available as
self-supporting sheets of uniform thickness, preferably 20-600
microns, particularly 50-250 microns, e.g. about 100 microns. PFMs
can be divided, e.g. by machining, die-cutting or kiss-cutting,
from such sheets. Available materials include, for example, porous
sheets which are based on polymers (but which may also contain
other ingredients, for example fillers), or inorganic materials,
for example silica, alumina and other ceramics.
[0087] Factors to be considered in the choice of porous material
include surface chemistry, surface charge, pore size, pore
topology, and formation factor, in conjunction with the system in
which the conduit is to be employed. Porous materials suitable for
use in this invention include materials in which the average pore
size is less than 10 micron or less than 1 micron, for example
materials in which all the pores have a size less than 10 or less
than 1 micron.
[0088] When the pore geometry of the sheet is isotropic, a PFM can
be divided from the sheet without regard to the intended direction
of liquid flow. When the pore geometry is anisotropic, a PFM
divided from the sheet must be used in a conduit such that at least
a component of the liquid flow is in the direction of the pores. In
some ultra-filtration membranes, the pore size distribution is
highly asymmetric in the direction normal to the membrane. A PFM
divided from such a membrane can be used in a separation device as
described in paragraph (H2) of The first aspect of the invention.
Depending on the type of device, it may be preferable to use a
material having a low surface charge density, preferably less than
10.sup.13, for example about 10.sup.12, charges/cm.sup.2, or a
material having a high surface charge density, preferably greater
than 10.sup.14, for example greater than 5.times.10.sup.14,
charges/cm.sup.2. For example, hydrophilic polyvinylidene fluoride
(PVDF), polyether sulfone and polyvinyl alcohol, are suitable for
bridges; polyamides, nitrocellulose, and sulfonated
polytetrafluoroethylene (PTFE) membranes are suitable in
ion-exchange elements; and modified PVDF, modified polyamides,
modified polyetherether ketones, silica, and alumina are suitable
for electrokinetic pumps. Hydrophobic materials, e.g. polypropylene
and other polyolefins, and PTFE, are suitable for vents.
[0089] In some cases, available porous sheet materials are
immediately usable in the present invention. In other cases, better
results can be obtained by further treatment of the available
materials, either in sheet form or as PFMs which have been divided
from them. One useful treatment is to derivativize the material to
modify its surface, e.g. to enhance or add surface charge or to
change its chemistry. Such treatments are well-known to those
skilled in the art, but are very difficult to apply to packing
materials that are already in place in a conduit. Reference may be
made, for example, to Macromolecules 31, 1277-1284 (1998), Jimbo et
al, J. Membrane Sci 179, 1-27 (2000), Takata et al and J. Membrane
Sci 139, 101-107 (2000), Belfer et al.
[0090] The preferred values of zeta potential and average pore size
differ from one type and device to another. The Table below (in
which the Debye length is denoted by the abbreviation X) gives
further information.
1 non-electroosmotic EOF device bridge element device Zeta Higher
values are Preferably dependent on the zeta Lower values are
potential generally preferred, e.g. >20 mV potential of the EOF
elements in generally preferred, or >50 mV. series with the
bridge element, e.g. <10 mV or <5 mV. for example <20 mV
or <10 mV. Average preferably >10 .lambda. or >20
.lambda.. Preferably dependent on the Preferably pore The preferred
upper limit pore size of the EOF elements in dependent on the size
depends on the required series with the bridge element, desired
pressure stall pressure; smaller pore e.g. <100 nm or <50 nm.
drop at a particular sizes are preferred for flowrate, e.g. from
higher stall pressures, e.g. 200 nm to 10 <500 nm or <150 nm.
micrometers.
[0091] PFM Dimensions
[0092] The terms length (L), width (w) and thickness (t) are used
to denote the dimensions of the flowthrough section of the PFM
(which may be the whole of the PFM), i.e. the part of the PFM which
is enclosed by the barrier member. Thus, if end sections of the PFM
extend beyond the barrier member into a junction or reservoir,
those end sections are not considered in determining L, w and t.
For PFMs whose cross-section at right angles to the axis of fluid
flow is a rectangle, w and t denote the dimensions of the longer
and shorter sides of the rectangle, respectively. In many cases,
PFMs having a rectangular cross-section are preferred. For PFMs
having non-rectangular cross-sections, w and t refer to the longer
and shorter sides of the rectangle of minimal area which can be
drawn around the non-rectangular cross-sections. For PFMs whose
cross-section varies, w and t refer to the effective average value,
taking into account the lengths of the PFM having particular values
of w and t. Thus, for a PFM of constant thickness and varying
width, the effective average value of w is the inverse of the
average of the inverse of w along the length of the PFM.
[0093] When the PFM is composed of a single layer of porous
material, its thickness, (or average thickness, if the thickness
varies) may be for example 20 to 600 microns, preferably 50 to 250
microns, e.g. 75 to 150 microns. When the PFM is composed of a
number of components, each component preferably has such a
thickness. Thus, a PFM comprising two or more layers of porous
material stacked on top of each other may have a thickness of, for
example, 200 to 2000 microns. The term equivalent diameter, d, is
used in defining the cross-section of the PFM (or the average value
of the equivalent diameter if the cross-section varies). d is the
diameter of a circle having the same area as the cross-section of
the PFM. Thus, for rectangular cross-sections d={square root}4
wt/.pi..
[0094] In many embodiments of the invention, L is substantially
greater than either of w and t. L is for example at least 3 times
or at least 5 times, e.g. 3 to 100 times or 5 to 30 times the
equivalent diameter, d. In many embodiments of the invention,
especially those in which the PFM has a rectangular cross-section,
w and t are such that the value of the ratio w/t is at least 3, at
least 10 or at least 20, for example 3 to 200, 5 to 100, or 8 to
75. The width w may be for example 0.2-2 mm.
[0095] Barrier Members
[0096] The conduits of the invention are constructed so that, in
use, a liquid follows a desired flow path through the flowthrough
section of the PFM. Thus, each PFM must be enclosed along its
boundaries, but not at its inlet(s) and outlet(s), by a barrier
member which is not permeable to the liquid. The barrier member can
be monolithic or composed of two or more barrier components or
layers secured together. A preferred method of providing the
barrier comprises laminating a PFM, generally a laminar PFM,
between barrier components, generally laminar, barrier components.
One or more of the barrier components can be pre-shaped in two or
three dimensions to conform to the PFM, making allowance when
necessary for deformation of the barrier components during the
lamination. For example, windows and/or channels can be formed in
the barrier components. The barrier components can be such that
they can be secured to each other and to the PFM by lamination
using heat and pressure. Suitable polymeric films, with bonding
temperatures from 80 to 350.degree. C. are well-known.
Alternatively or additionally, lamination can be affected with the
aid of adhesives. In another embodiment, the barrier member is
provided by a liquid barrier composition which is placed around the
PFM and then solidified. Examples of such compositions include
potting compositions which cure at room temperature or with the aid
of heat or ultraviolet, ultrasonic or other radiation, and which
may contain fillers, e.g. reinforcing fibers, e.g. compositions
based on epoxies, polyphenylene oxides, acrylic resins and
silicones. In another embodiment, the barrier member is prepared by
wrapping a flexible barrier film or tape around the PFM, and
optionally treating, e.g. heating, the wrapping. Alternatively or
additionally, mechanical means can be used to secure the barrier
member around the PFM.
[0097] The barrier components and the way in which they are secured
around the PFM should be such that the PFM is not penetrated by the
barrier material or otherwise physically or chemically damaged. If
need be, a protective layer can be placed between the PFM and the
barrier component(s).
[0098] The conduits of the invention preferably have physical
properties such that they can be conveniently handled and used,
including the ability to withstand the fluid pressure within the
conduit, which can vary widely between different types of system.
Such physical properties may be provided by the barrier member
alone. Alternatively or additionally, the device can include one or
more support members, e.g. of metal or glass, to provide desired
physical properties. Generally the conduits of the invention are
rigid, i.e. do not bend or flex in use. However, the conduit can be
flexible.
[0099] Additional Components
[0100] The devices of the invention can include a wide variety of
additional components, for example junctions and capillaries
through which, in use, liquids enter or leave an inlet, outlet or
an intermediate point of the PFM; reservoirs for liquids;
electrodes; electrode leads; pumps, and optical and/or electrical
components for monitoring the system. Such additional components
can be incorporated into the device at the same time as the barrier
member is placed around the PFM, for example by placing them
between layers which are secured together as part of a lamination
process. Alternatively, or additionally, they can be added after
the barrier member has been placed around the PFM, for example by
creating vias in the barrier member(s) and/or support member(s),
inserting the additional component and sealing the via around the
additional component. The fluidic junctions in the devices of the
invention preferably have a low dead volume.
[0101] Devices and Systems
[0102] The conduits of the invention can form a part of, or be used
in association with, a wide variety of flow devices, including, for
example, devices for chromatographic separation, devices for
chemical processing, analytical devices, pumps, injectors, flow
controllers, separation elements, bridges, reactors, mixers, and
detection elements, including the devices disclosed in copending
commonly assigned U.S. patent application Ser. Nos. 10/137,215,
10/155,474, 10/273,723 and 10/322,083, and International Patent
Applications PCT/US 02/19121 (published as International
Publication Number WO 02/101474) and PCT/US 03/13315, the
disclosures of which are incorporated herein by reference.
[0103] Multilayer Devices
[0104] Many devices of the invention contain two or more, for
example, at least 3 or at least 4, e.g. 3-6, laminar PFMs, each PFM
forming part of a layer in a multilayer device. Each PFM-containing
layer can contain one or more PFMs. The PFMs in different layers
can be placed so that the major surfaces of adjacent PFMs
completely overlap, partially overlap, or do not overlap. Adjacent
PFM-containing layers can be separated from each other by a barrier
layer, or can contact each other directly. When adjacent
PFM-containing layers contact each other directly, and the PFMs
overlap, the PFMs will contact each other. The liquid flows in the
PFMs can be in the same direction or in different directions,
including opposite directions. Different PFMs can be in fluid
communication with each other through direct contact and/or because
both communicate with the same fluidic junction. A multilayer
device can contain two or more fluid systems which operate
independently of each other, or fluid systems whose operation is
dependent on the behavior of each other.
[0105] The mixing devices, the multilayer devices with two or more
overlapping PFMs, and the filtration devices described below are
particular examples of the multilayer devices of the invention.
[0106] Mixing Devices
[0107] One embodiment of the invention is a mixing device having
characteristic (F) set out in the first aspect of the invention.
Such mixing devices optionally can have one or more of the
following characteristics:--
[0108] (F1) at least one, and preferably each, of the first and
second PFMs comprises a flowthrough section having a width w.sub.1,
and a transfer section which comprises
[0109] (i) a flared section in which the width increases to
w.sub.3, the increase preferably being symmetrical about the flow
axis, and w.sub.3 preferably being from 2 to 4 times w.sub.1, and
the length of the flared section preferably being from 0.3 to 0.7
times w.sub.3, and
[0110] (ii) a pre-mixing section which is adjacent to the flared
section and which has the width w.sub.3, and which preferably has a
length from 0.8 times to 2 times the length of the flared
section;
[0111] however, in some cases, adequate mixing can be obtained with
little or no flared section, the pre-mixing section then having a
width of, for example, 1 to 1.5 times we;
[0112] (F2) the device includes a mixing member which
[0113] (i) is composed of a porous material having a pore size
greater than the pore size of either of the PFMs, preferably a pore
size which is at least 2 times, particularly at least 5 times, for
example 5 to 20 times, the pore size of the PFM having the larger
pore size; and
[0114] (ii) comprises an intermediate section which lies between
and contacts the first and second transfer sections, and a
continuation section which extends from the first and second
transfer sections; the intermediate section and the continuation
section preferably have the same width as the transfer sections;
the length of the intermediate section is preferably 0.1 to 0.8
times the length of the pre-mixing section; the length of the
continuation section is preferably selected to provide the desired
degree of mixing; and the end of the continuation section
preferably has a reduced width suitable for making a conventional
connection to the next fluidic stage of the device;
[0115] (F3) at least one of the PFMs is divided into two parts,
each part having a flowthrough section and a transfer section, and
the transfer sections of the first and second PFMs are interleaved
with each other;
[0116] (F4) the area A between the overlapping transfer sections
has an equivalent diameter d.sub.transfer such that each of the
ratios d.sub.transfer/t.sub.1 and d.sub.transfer/t.sub.2 is at
least 5, preferably at least 10, more preferably at least 20, for
example 10 to 200 or 20 to 100;
[0117] (F5) liquid flows in the first transfer section along a
first flow axis and liquid flows in the second transfer section
along a second flow axis, and the liquid flow in the second
transfer section has a component parallel to the first flow axis,
the component preferably being at least 50%, particularly at least
80%, of the flow.
[0118] The mixing device can be used for example, to mix two
aqueous liquids, two organic liquids, or an aqueous liquid and an
organic liquid. The liquids can be of different viscosities, may
contain dissolved chemicals, including biochemicals, and may be
dispersions of particulate materials or emulsions. The liquids can
be miscible or immiscible, for example in order to produce an
emulsion or as part of a chemical extraction, or can undergo a
chemical reaction together. The solid porous material of the PFMs
should be selected so that they are not damaged by, and do not
damage, the liquids being mixed or the products of the mixing. The
liquid flow can be one or both of pressure-driven flow and
electroosmotic flow. The flowrates through the PFMs can be the same
or different and can be constant or can vary.
[0119] Preferably, the PFMs and the dimensions of the device are
selected so that the pressure drop over at least one, and
preferably all, of the flowthrough sections is greater than, for
example at least 2 times, preferably 5 to 15 times, for example
about 10 times, the pressure drop between the mixing stage and the
outlet
[0120] The mixing device can be used to mix three or more liquids
simultaneously, by using a corresponding number of conduits having
overlapping transfer sections. The mixing device can contain two or
more mixing stages, for example a first mixing stage in which two
different liquids are mixed, and a second mixing stage in which the
product of the first mixing stage is mixed with a third liquid. In
this way, for example, successive stages of a chemical synthesis
can be carried out in the different mixing stages.
[0121] FIGS. 23 to 27 depict mixing devices of the invention.
[0122] Multilayer Devices
[0123] One embodiment of the invention is a multilayer device
having the characteristic (G) as set out in the first aspect of the
invention. Such a multilayer device optionally can have one or more
of the following characteristics:--
[0124] (G1) the first and second laminar PFMs overlap each other in
an overlap area, and one of the barrier members is an intermediate
barrier member which lies between the first and second PFMs, and
which, over a substantial proportion, for example at least 70%,
e.g. 90-100%, of the overlap area, prevents liquid from flowing
between the first PFM and second PFM.
[0125] (G2) the device comprises a junction which is in fluidic
communication with the first and second PFMs, the junction
optionally comprising a porous material;
[0126] (G3) the device comprises at least 3, for example 3 to 6,
laminar PFMs which lie in parallel but different planes.
[0127] Filtration Devices
[0128] One embodiment of the invention is a filtration device
having characteristic (G1) or (G2) as set out in the first aspect
of the invention. When a liquid containing relatively small
molecules or particles of one type and relatively large molecules
or particles of another type is passed through a layered PFM as
defined in (G1) or a PFM having an asymmetric pore size
distribution as defined in (G2), some of the smaller molecules or
particles migrate to one surface of the PFM, and a product
containing only the smaller molecules or particles can be recovered
from that surface, while a product containing the larger particles
and a smaller proportion of the smaller molecules can be recovered
from the opposite surface. A liquid can be passed through the
device to assist in recovery of the smaller molecules or particles.
FIGS. 17 and 18 depict such devices.
[0129] Devices with Two PFMs Having Different Zeta Potentials
[0130] One embodiment of the invention is a device containing two
PFMs having different zeta potentials, in particular a device
having characteristic (I) as set out in the first aspect of the
invention. Such devices can optionally have one or more of the
following characteristics
[0131] (I1) the first and second zeta potentials have an opposite
sign;
[0132] (I2) the first and second zeta potentials differ by at least
20, preferably at least 50, e.g. 50-100, mV, and
[0133] (I3) the device includes
[0134] (i) a first chamber communicating with the inner fluidic
junction and having a wall which comprises a flexible diaphragm,
and
[0135] (ii) a second chamber having a wall which comprises the
flexible diaphragm.
[0136] When such a device is filled with a suitable ionic liquid
and electrical current flows between the electrodes, the direction
of liquid flow depends upon the zeta potentials. If the zeta
potentials are of opposite sign, the liquid flow in each of the
PFMs is towards the central junction when the current flows in one
direction, and away from the central junction when the current
flows in the opposite direction. If the zeta potentials are of the
same sign, the liquid flow in each of the PFMs is in the same
direction, with the direction depending on the direction of the
current. The rate of flow in each PFM depends on a variety of
factors, including the sign and size of the zeta potentials. There
is, therefore, a net flow of liquid to or from the central
junction. In this device, the electrodes can be in ambient pressure
reservoirs from which gaseous by-products can easily be vented.
When the device has feature (13) above, it can be used to pump a
liquid in the second chamber. The liquid in the second chamber need
not be a liquid which will support proper electroosmotic flow; for
example it can be a liquid containing polyvalent ions, a liquid
having very high conductivity, or a liquid containing a substance
which is damaged by electrical current.
[0137] Butt Junctions Between PFMs
[0138] When two PFMs are butted together at a fluidic junction, the
area of contact between them is limited to the smaller of the two
PFM cross-sections (or a somewhat larger, but still small, area if
the ends of the PFMs are shaped to fit each other]. Consequently,
there may be substantial resistance to the movement of liquid out
of an outlet of the junction. In addition, there is a danger that,
during preparation of the device, the junction between the PFM will
be partially blocked by liquid barrier material. In one embodiment
of the invention, these problems are ameliorated through the use of
at least one auxiliary porous member which contacts the sides of
the PFMs and bridges the butt joint between them. The auxiliary
porous member is preferably made of a porous material having a pore
size greater than the pore size of either of the PFMs; preferably a
pore size which is at least 2 times, particularly at least 5 times,
for example 5 to 20 times, the pore size of the PFM having the
larger pore size.
[0139] Preparation of the Devices
[0140] The devices of the invention can be prepared by either of,
or a combination of, the methods included in the definition above
of the third aspect of the invention Before the barrier is placed
around the PFM, a wide variety of additional components, e.g.
capillary tubes, electrodes, electrode leads, optical and/or
electrical monitoring components, preformed junctions and preformed
reservoirs, can be assembled in contact with and/or separated from,
the PFM, and thus incorporated into the device, at the same time as
the barrier is placed around the flowthrough section of the PFM. In
many cases, lamination of a plurality of barrier layers is the
preferred method. The additional components can be placed between
two barrier layers and/or between a barrier layer and a PFM.
Especially when the device comprises two or more PFMs, the device
can be prepared in two or more successive steps, the steps being
the same or different.
[0141] Wetting Procedures
[0142] When the devices of the invention are in use, they are
filled with a liquid. When the flow of liquid is solely
pressure-driven, any appropriate liquid can be used. When the flow
is at least partly electroosmotic flow, the liquid must be an ionic
liquid. It is, therefore, desirable to design the devices so that
they can be easily wetted without trapping air pockets. The device
can be filled with a liquid after it has been made (and after
sterilization, if needed). In some cases parts of the device can be
wetted while the device is being made. After it has been wetted, a
device can be sealed and stored until it is needed. Methods of
wetting flow devices are well-known to those skilled in the
art.
[0143] The Drawings
[0144] FIGS. 1-3 show a device which can be used as part of an
electrokinetc pumping system or as part of a combined
electroosmotic and pressure-driven flow system. In FIGS. 1-3, PFM
102 is composed of a solid porous material and comprises a
flowthrough section having a length L, a width w and a thickness t,
and terminal transfer sections which extend into junctions 114a and
114b. Porous members 118a and 118b provide bridges between junction
114a and a reservoir 115a, and between junction 114b and a
reservoir 115b, respectively. Porous members 118a and 118b can be
conventional conduits, or conduits of the invention. Insulating
barrier layers 106a, 106b and 106c and support members 120a and
120b encapsulate the porous members 102, 118a and 118b, and define
the junctions 114a and 114b and the reservoirs 115a and 115b.
Electrodes 312a and 312b pass into the reservoirs 115a and 115b
respectively. Capillaries 112a and 112b pass through sealed vias in
support member 120b into junctions 114a and 114b respectively. In
use, the electrodes are connected to a power source, an ionic
liquid is placed throughout the device, and an ionic liquid flows
through the capillary 112a, the PFM 102 and the capillary 112b. The
liquid in the reservoirs serves to carry current and little or none
of it flows through PFM 102.
[0145] In FIG. 4, capillary 112a and electrode 312a are placed
between PFM 102 and barrier layer 106c, and are covered by
nonporous member 306 to ensure proper fluidic and electrical
connection to PFM 102. In FIGS. 5 and 6, barrier layers 106a, 106b
and 106c are shaped so that PFM 102 extends into a well 416 to
which there is access through via 116 in support member 120b. In
FIG. 7, PFM 102 and the barrier layers 106a, 106b and 106c are
shaped so that the via 116 communicates directly with the PFM 102.
In FIG. 8, transducer 406 is secured below support member 120a by
barrier layer 106d, and forms a lower well 417 which communicates
with the well 416 through a via 117 in support member 120a. In FIG.
9, the end of the PFM 102 is placed in a reservoir 115 containing
liquid 121. As shown in FIG. 9, the end of the PFM 102 is flush
with the ends of the barrier and support members. In alternative
embodiments, the PFM 102 can extend beyond, or be terminated short
of, the ends of the barrier and support members. In FIG. 10,
optical fibers or electrodes 803a and 803b are placed opposite each
other so that fluid flowing through the device passes between them
and can be examined by passing light or electrical current between
them.
[0146] FIGS. 11-13 show a simple PFM for use in the invention.
FIGS. 12, 13 and 14 show a PFM having flared ends. FIGS. 12, 15 and
16 show a PFM which is shaped so that three sections of the PFM lie
in the same plane and overlap each other transversely.
[0147] FIGS. 17 and 18 show devices which can be used to achieve
partial separation of molecules or particles of different sizes. A
liquid containing relatively small molecules or particles of one
type and relatively large molecules or particles of another type
enters inlet junction 114a through capillary 112a. The junction
114a communicates with a PFM comprising a first layer 102a having a
relatively large pore size such that both types of molecule or
particle will pass through it. In contact with first layer 102a,
but not communicating with junction 114a is a second layer 102b
having a smaller pore size such that only the small molecules or
particles passing through the layer 102a will migrate through the
interface into layer 102b. A product containing only the smaller
molecules or particles is recovered from outlet junction 114b
through capillary 112b, and a product containing all the large
molecules or particles and a reduced proportion of the small
molecules or particles is recovered from outlet junction 114c
through capillary 112c. In FIG. 18, a liquid is introduced through
capillary 112d and junction 114d to layer 102b, and assists in the
removal of the smaller molecules or particles.
[0148] FIG. 19 shows a device in which PFMs having different zeta
potentials are used to convey a liquid from each end of the device
towards the center, or vice versa. PFM 102a has a first zeta
potential and communicates at one end with junction 114a and at the
other end with junction 114c. PFM 102b has a second zeta potential
and communicates at one end with junction 114b and at the other end
with junction 114c. The first and second zeta potentials differ
substantially, and may be of the same or different signs. Reservoir
115a containing electrode 312a communicates with junction 114a.
Reservoir 115b containing electrode 312b communicates with junction
114b. Capillary 112 communicates with junction 114c. The device
operates as previously described.
[0149] FIG. 20 is the same as FIG. 19, except that closed chambers
208 and 209, separated by flexible diaphragm 201, are on top of the
central junction 114c. The liquid pumped into or out of chambers
208 changes the shape of the diaphragm 201, and thus pumps liquid
in chamber 209. Chamber 209 is fitted with a septum or valve 204
for the introduction of liquid into the chamber, and an outlet 212
fitted with filter 203.
[0150] FIG. 21 shows a device having four PFMs, 102a, 102b, 102c
and 102d, and barrier layers 106a-h arranged so that liquid
introduced through capillary 112a flows consecutively through
junction 114a, PFM 102a, junction 114b, PFM 102b, junction 114c,
PFM 102c, junction 114d, PFM 102d, and junction 114a, and then
exits through capillary 112b.
[0151] FIG. 22 shows a device having four PFMs, 102a, 102b, 102c
and 102d stacked one on top of each other, and barrier layers
106a-h arranged so that liquid introduced through capillary 112a
flows consecutively through junction 114a, through the PFMs at
right angles to the planes thereof, and junction 114b, and then
exits through capillary 112b.
[0152] FIGS. 23-25 show a mixing device comprising two PFMs (102a,
102b). Each PFM is of constant thickness (t.sub.1, t.sub.2) and has
a flowthrough section of constant width (w.sub.1, w.sub.2) and a
transfer section. The transfer section is made up of a flared
section in which the width increases to w.sub.3 over a length
L.sub.1 and a pre-mixing section of constant width w.sub.3 and
length L.sub.2. Sandwiched between the ends of the two pre-mixing
sections is a mixing member 118 having a width w.sub.3 which is
maintained for a length L.sub.3 sufficient to achieve a desired
degree of mixing.
[0153] FIG. 26 shows part of a mixing device which comprises two
PFMs 102a, 102b. PFM 102a is divided into two overlapping parts
(102a1, 102a2), each having a flowthrough section and a transfer
section which may be as shown in FIGS. 23-25. PFM 102b is placed
between the overlapping parts (102a1, 102a2). Liquids flowing
through the two PFMs are delivered to an open mixing chamber and
discharged.
[0154] FIG. 27 is a flow diagram showing how liquids flowing
through two PFMs 102a, 102b can be mixed with each other, and the
product of mixing in turn mixed with liquid flowing through PFM
102c.
[0155] FIGS. 28 and 29 show a butt joint between two PFMs 102a,
102b. An auxiliary porous member 118 bridges one side of the butt
joint.
[0156] The following Examples illustrate the invention.
EXAMPLES 1-3
[0157] Three devices as illustrated in FIG. 19 were constructed
using first and second PFMs having the characteristics shown in the
Table below, the dimensions of L, w and t being in mm. In each
Example, the effective pore size of the first PFM was 240 nm and
the effective pore size of the second PFM was 300 nm.
2 First PFM Second PFM Example # L w t Zeta L w t Zeta 1 10 5 0.1
+50 10 2.1 0.12 -30 2 10 5 0.1 +50 5 8 0.2 +2 3 10 2.3 0.1 -35 8.75
2.3 0.09 +27
EXAMPLE 4
[0158] A mixing device as shown in FIGS. 23-25 was prepared. The
dimensions of the device, as identified in FIGS. 23-25 and given in
mm, are shown in the table below. Each of the PFMs was a
hydrophilic PVDF membrane having effective pore size of about 800
nm. The mixing member was a hydrophilic PVDF membrane having an
effective pore size of about 6000 nm and a thickness of 0.1 mm.
3 W.sub.1 W.sub.2 W.sub.3 L.sub.1 L.sub.2 L.sub.3 t.sub.1 t.sub.2 2
2 6 4 6 10 0.1 0.1
* * * * *