U.S. patent application number 11/112186 was filed with the patent office on 2005-09-01 for filter device to capture a desired amount of material and methods of use.
Invention is credited to Ferguson, Gary W..
Application Number | 20050189286 11/112186 |
Document ID | / |
Family ID | 32041940 |
Filed Date | 2005-09-01 |
United States Patent
Application |
20050189286 |
Kind Code |
A1 |
Ferguson, Gary W. |
September 1, 2005 |
Filter device to capture a desired amount of material and methods
of use
Abstract
The present invention is a filter device with methods to capture
a desired amount of material suspended in a liquid or gas. These
filter capture methods may be used for the purification or
enrichment of various sample constituents or captured material may
be observed or analyzed. The filter device employs a deformable
filter to provide a simple reliable device to capture a desired
amount of material, with minimal electronic intervention.
Inventors: |
Ferguson, Gary W.; (Burnaby,
CA) |
Correspondence
Address: |
TREXLER, BUSHNELL, GIANGIORGI,
BLACKSTONE & MARR, LTD.
105 WEST ADAMS STREET
SUITE 3600
CHICAGO
IL
60603
US
|
Family ID: |
32041940 |
Appl. No.: |
11/112186 |
Filed: |
April 22, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11112186 |
Apr 22, 2005 |
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10263129 |
Oct 2, 2002 |
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6884341 |
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Current U.S.
Class: |
210/406 ;
210/416.1; 210/446; 55/467 |
Current CPC
Class: |
Y10T 436/25375 20150115;
G01N 1/2813 20130101; G01N 1/4077 20130101; G01N 2001/2826
20130101; G01N 1/405 20130101; G01N 15/0618 20130101; Y10T 137/8122
20150401 |
Class at
Publication: |
210/406 ;
210/416.1; 210/446; 055/467 |
International
Class: |
B01D 035/26 |
Claims
I claim:
1. An apparatus for capturing a desired quantity of material from a
sample suspension on a filter, comprising: a body member defining a
chamber and having opposed ends, an outlet port in one of said
ends, and an inlet port; said inlet port and said outlet port
defining a single pathway for sample suspension to flow though said
apparatus; a substantially planar filter mounted within said
chamber between said inlet port and said outlet port and completely
across said single pathway, so that sample suspension flowing
through said apparatus must flow from said inlet port through said
filter and to said outlet port; said filter being deformable toward
said outlet end at a predetermined pressure change across said
filter and having a first porous portion and a second porous
portion concentrically arranged centrally of said first portion,
said predetermined pressure change selected so that when a desired
quantity of material has been captured by said first portion, said
substantially planar filter deforms against said outlet end such
that all flow of sample suspension through said apparatus must flow
through said more restrictive second portion; and means for
providing a pressure to cause said sample suspension to flow
through said apparatus.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/263,129, filed on Oct. 2, 2002, and published as United
States Published Patent Application No. 2004/0065622 A1, and claims
priority from that application.
BACKGROUND OF INVENTION
[0002] In industry and biology it is often advantageous to capture
particulate material suspended in a liquid or gas, on a filter for
purification, enrichment, observation or subsequent analysis. The
quantity and characteristics of particulate material is important
in manufacturing, for example, processes that utilize powders,
pigments, fuels or lubricants. Particle evaluations are also used
to assess contaminants in water or air such as pollen, asbestos and
soot. Particulate material is sometimes used indirectly to assess
proteins or chemicals, for example, beads coated with monoclonal
antibody may be interacted with blood. Then these beads may be
captured on a filter and assessed for bound protein.
[0003] As used herein, "sample suspension" means particulate
material suspended in a liquid or gas. "Material" as used herein
means biological cells, organisms, bacteria, viruses, or components
of these, as well as organic and inorganic particulates or any
other matter which may be captured or isolated on a filter. This
captured material may be subsequently used to provide diagnostic
and/or analytical information or be re-suspended or otherwise used.
For example, captured material may be analyzed chemically or may be
placed on a receiving surface, such as a microscope slide for
analysis.
[0004] Although there are a number of established methods to
deposit mono-layers of material on a receiving surface for
observation or analysis, controlling the amount of material
collected on a filter is more difficult to achieve. Typically,
electronic control and intervention is required to monitor and
control the collection of material on a filter apparatus and/or
other laboratory methods (employing particle counters and dilution
techniques) are used to adjust the concentration of the material in
suspension. Unfortunately, these methods require additional
apparatus and electronics, and are relatively complex or expensive
in terms of supplies, and time. Therefore, a simple, reliable
method of capturing a desired amount of material on a filter would
be advantageous.
[0005] The present invention is a filter device that provides a
means to collect a desired amount of material. To accomplish this,
a pressure sensor is used substantially to monitor the flow rate
through the filter. In addition, the pressure sensor may be
combined with a valve that provides control over sample flow, and
thus the collection of material. In one embodiment of the present
invention, a pressure sensor and valve are integrated to form a
pressure-sensitive check valve. In other embodiments the membrane
filter or filter assembly themselves deform, acting as a pressure
sensor and flow control mechanism.
SUMMARY
[0006] It would be beneficial to provide a simple filter apparatus
to capture a desired amount of material on a filter that does not
rely on relatively complex electronics and sensors. In addition, it
would be advantageous to provide a filter capture method that can
be automated to prepare a plurality of samples, simultaneously.
Accordingly, as will be further described, the present invention
provides a novel apparatus incorporating a pressure transducer and
means to substantially halt or otherwise adjust sample flow,
providing a simple, reliable device to capture a desired amount of
material without complex electronics. In addition, the present
invention is easily automated to allow material from a plurality of
samples to be captured on a membrane filter, simultaneously.
[0007] As previously discussed herein, a variety of pressure
sensors are available with appropriate characteristics for
exploitation within the present invention. For some applications
material captured on a filter is intended for contract-transfer to
a receiving surface, such as a microscope slide. Accordingly, for
some applications when a relatively large filter is required, or
the suspending fluids are viscous, for example, a filter support
structure may be desirable.
[0008] The present invention provides a filter apparatus using
means to measure or sense the flow rate of a gas or liquid through
a filter. In some embodiments pressure is sensed, however, the flow
rate of a fluid or gas could also be sensed. In some embodiments,
the present invention terminates or otherwise adjusts sample flow
when a predetermined amount of material has been captured on a
filter for example by venting the pressure differential responsible
for sample flow, or closing the flow pathway, for example with a
valve. In other embodiments of the present invention material
collection on a filter is substantially reduced by restricting
access to the filter, for example, by changing its position or
deforming its shape.
[0009] Filter types include fibrous and mesh membranes, porous and
capillary porous membranes, and fabric and gel lattices, for
example. Such filters are commonly made from paper, nylon, glass
fibers, nitrocellulose, polypropylene, chemical gels etc. In some
cases filters are further treated to enhance certain properties
such as capture capacity, flexibility, selectivity or adherence by
coating them or incorporating other compounds such as PTFE or
protein binding compounds. Accordingly, filters can be formed in
various shapes such as planar, conical, pyramidal, hemispherical,
or spherical, or filters may have their shape imposed by a carrier
or other support structure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The organization and manner of the structure and operation
of the preferred embodiments of the invention, together with
further objects and advantages thereof, may best be understood by
reference to the following description, taken in connection with
the accompanying drawings, wherein like reference numerals identify
like elements in which:
[0011] FIG. 1a (Prior art) Method to collect and monitor the
concentration of material captured on a membrane filter.
[0012] FIG. 1b (Prior art) Membrane filter device used in
conjunction with FIG. 1.
[0013] FIG. 2a shows an embodiment of the present invention
capturing a desired amount of material.
[0014] FIG. 2b shows another embodiment of the present invention
capturing a desired amount of particulate material from a fluid
suspension.
[0015] FIG. 2c shows the embodiment of FIG. 2b used to capture a
desired amount of material suspended in a gas.
[0016] FIG. 3a shows a membrane filter apparatus with
pressure-sensitive check valve.
[0017] FIG. 3b shows another configuration of membrane filter
apparatus.
[0018] FIG. 3c shows an embodiment of the present invention,
incorporating a pressure-sensitive check valve in the form of
spring tabs arranged around the periphery of a filter
apparatus.
[0019] FIG. 4 shows an embodiment of the present invention utilized
to process a plurality of samples.
[0020] FIG. 5a shows a syringe filter assembly of an embodiment of
the present invention where a deformable filter provides flow rate
monitoring (pressure detection) and flow rate control.
[0021] FIG. 5b shows a desired amount of material collected on the
syringe filter associated with FIG. 5a.
[0022] FIG. 6a show yet another embodiment of a filter assembly to
monitor and control or otherwise adjust flow rate through a
filter.
[0023] FIG. 6b further describes the filter assembly associated
with FIG. 6a.
[0024] FIG. 6c shows an embodiment of a filter assembly at rest
(under normal operating conditions).
[0025] FIG. 6d shows the filter assembly embodiment of FIG. 6c in
an activated state having responded to pressure changes indicative
of collecting a desired amount of material.
DETAILED DESCRIPTION OF THE DRAWINGS AND PREFERRED EMBODIMENTS
[0026] While the invention may be susceptible to embodiment in
different forms, there is shown in the drawings, and herein will be
described in detail, specific embodiments with the understanding
that the present disclosure is to be considered an exemplification
of the principles of the invention, and is not intended to limit
the invention to that as illustrated and described herein.
[0027] FIG. 1a (prior art) illustrates a system 10 to collect a
desired quantity of cells onto the underside of a screen-type
filter 12. As diagrammed, a pressure sensor 26 is in communication
with both sides of a membrane filter 12. Accordingly, one side of
the membrane 12 in the collection vessel 18 is shown at ambient
pressure with pressure sensor 26 provided on the opposite side of
the membrane. Pressure unit 30 typically responds to electrical
control signals from a control unit, which can be
microprocessor-controlled, to apply selected fluid conditions to
the interior of the collection vessel.
[0028] FIG. 1b (Prior art) further illustrates the collection
vessel 18 with screen-type filter 12 as used in this apparatus, and
as described in U.S. Pat. No. 6,010,909 and again in U.S. Pat. No.
6,225,125. In this manner, a desired quantity of material may be
captured.
[0029] FIG. 2a shows an embodiment of the present invention with
filter apparatus 205 comprised of filter 215 deposed between a top
body member 210 and a bottom body member 220. In this instance,
open container 235 contains sample suspension 230 (e.g. particulate
material suspended in a liquid), which is introduced via pickup
tube 245. This pickup tube, as required or desired, may comprise
part of the bottom body member 220 or pickup tube 245 may be a
separate member attached to body member 220. The object of the
device, which will now be further described, is to provide a means
to monitor or otherwise sense the flow rate of this sample
suspension 230 and to provide a means to alter, adjust, halt or
otherwise influence that flow rate when indicated by a sensor 250,
which is in communication (mechanically or electro-mechanically)
with the means to control flow. Sample suspension 230 is drawn by
application of pressure from vacuum source 200 therefore providing
a means to cause sample suspension 230 to flow as further indicated
by flow directional arrow 240, which as diagrammed, is in the inlet
port 221 of the pickup tube 245, into the bottom body member 220,
through the filter 215, which is this instance is a membrane
filter, through a flow control element 212 (in this instance a
valve) and then out through the outlet port 211. (In this
embodiment, as well as in subsequently-described and illustrated
embodiments, vacuum is used to cause the sample suspension to flow.
Other means can be used for this purpose in this and subsequent
embodiments, such as gravity or mechanical means such as a pump.)
Accordingly, as sample suspension 230 flows in this manner,
particulate material in the sample suspension 230 begins to be
captured by membrane filter 215. Pressure sensor or pressure
transducer 250, in this instance contained substantially within the
top body member 210, communicates with the upper surface of
membrane filter 215. This communication is further indicated by
communication arrow 270. Pressure sensor 250 is also in
communication with flow control element 212 so as to provide a
means to adjust or otherwise control flow when certain pressures
are sensed. This communication between pressure sensor 250 and flow
control element 212 is further indicated by communication arrow
260. Accordingly, a pressure differential is established across the
membrane filter 215, thereby providing a means for the pressure
sensor 250 to monitor the flow rate of the sample suspension. As
sample continues to flow, and as described in association with the
description of prior art in FIGS. 1 and 2, particulate material
that is smaller than the pore size of the membrane filter 215
passes through the membrane (to waste or to another vessel--not
shown) while material larger than the pore size of the membrane
filter 215 is captured. Since filter pores provide the actual
pathway through a filter, material captured by the membrane filter
215 typically blocks pores, which in turn restricts flow. When the
flow rate drops to a certain level, pressure sensor 250 responds
(at a predetermined pressure based on the application, filter
characteristic, amount of desired material etc. as previously
described herein and in the prior art cited), pressure sensor 250
activates and in turn activates flow control element 212. The flow
control element 212 may halt the flow of sample suspension 230 and
hence stop further capture of material on the membrane filter 215,
which has now captured the desired amount of material. While such a
valve (flow control element 212) could be implemented in various
positions of within the filter assembly 205, generally
communication with pressure sensor 250 is simpler and provides more
options when these two functions are relatively closely related.
Further examples of this will be provided in the descriptions
accompanying FIGS. 2b and 2c. Activation of the flow control
element 212 may be mechanical, electromechanical or may be
accomplished via further integration of the pressure sensor and
valve (as will be further discussed). Similarly, these elements may
be physically separate or may be functionally integrated. For
applications, such as monolayer deposition, that may require access
to the filter for touch or other material transfer method, the top
body member 210 and bottom body member of filter apparatus 205 are
preferably made separable, by employing threads or a press-fit
assembly, for example.
[0030] FIG. 2b shows another embodiment of the present invention
with sample suspension 230 being drawn through filter 215 by
application of vacuum 200. In this instance filter 215 is sealed to
the bottom of upper body member 210, thereby providing access to
material captured by membrane filter 215. As diagrammed the sensor
250 is integrated with flow control element 213, which in this
instance provides flow control using a valve to vent the pressure
source 200 through vent port 214 or flow control valve 213, rather
than adjusting the sample flow pathway, as described in association
with FIG. 2a. As required, or desired, the vent may substantially
release the vacuum supplied by source 200 to halt flow, or the drop
in vacuum provided by this venting may be sensed and the vacuum
source, shut off.
[0031] FIG. 2c shows application of the device and configuration of
the present invention described in association with FIG. 2b where
sample suspension 221 consists of particulate matter, for example,
soot, suspended in a gas, for example air.
[0032] FIG. 3a shows an embodiment of the present invention 300
comprised of a hollow main body 310 and a pressure-sensitive check
valve 320 extending into the main body 310 so as to communicate
with one side of a membrane filter 330, which is attached to the
underside of the main body 310. As desired, for use in fluids, a
protrusion 335 may be provided on the bottom of the main body 310
or may be fashioned appropriately to stop the membrane filter 330
from contacting the bottom of a sample vessel (not shown) and
disrupting flow during use. A vacuum source 360 is provided for
sample aspiration. Initially, the vent portion 340 of the
pressure-sensitive check valve 320 is closed and typically, the
membrane filter 330 is fresh (free of sample material). To begin
collection, vacuum is used to draw sample suspension (not shown)
through the membrane filter 330 causing material to collect on the
underside of the membrane filter 330. Accordingly, as material
collects, the pores become occluded and the rate of flow of sample
suspension decreases. The pressure-sensitive check value 320
monitors flow rate through the membrane filter 320 and when the
flow rate falls to a desired level, thus indicating that a desired
amount of material has been collected, the pressure-sensitive check
valve 320 triggers (at a predetermined pressure) and sample flow
(and material collection) is halted. Descriptions of filter
collection systems that utilize electronics to accomplish a
comparable task may be found in U.S. Pat. No. 6,010,909 and U.S.
Pat. No. 6,225,125. A portion of this prior art is presented in
FIGS. 1 and 2 herein. Although various filters may be employed in
such a configuration, for preparing cytological samples, the
membrane filter 330 typically has relatively uniformly-distributed
pores of a uniform size, intended to capture material larger than
the pore size, while passing particulate material that is small.
Approximately half a dozen companies provide a filter apparatus
that is adapted to a syringe (syringe filters).
[0033] For one embodiment of the present invention, the sensor
portion of the pressure-sensitive check valve 320 has been adjusted
to trigger at a desired, predetermined pressure which is
established to indicate capture of a desired quantity of material
on the bottom surface of the membrane filter 330. As diagrammed,
when the pressure-sensitive check valve 320 triggers (indicating
that a desired amount of material has been captured), a pathway is
opened which vents off the vacuum, thereby stopping the aspiration
of sample. While it is one object of the present invention to
minimize or eliminate electronics that communicate with the
pressure transducer or control systems, a battery-powered pressure
transducer and/or valve assembly is consistent with this objective.
As desired, the pressure-sensitive check valve 320 could be
implemented in a variety of other ways so as to monitor and control
sample flow, for example upon triggering it could close a fluid
pathway. For biological applications, or when other dangers are
present, it may be preferable to vent the vacuum as described,
which serves to limit the potential for aerosols.
[0034] To simultaneously prepare several samples, vacuum could be
provided by a stepper-driven syringe, with one syringe for each
sample. For higher levels of automation a vacuum pump and vacuum
isolators may be preferred. Accordingly, material capture by the
present invention may be transferred by contacting an appropriate
receiving surface. For some applications, such as machine vision
examination of cytological samples, monolayer deposition may be
made to the underside of a cover-glass or other relatively thin,
uniform material, such as transparent tape, thereby providing
material at approximately the same distance from the top surface to
facilitate focus. To provide additional rigidity, the thin
receiving surface may be placed or affixed to a second surface as
desired, or required.
[0035] FIG. 3b shows an alternative configuration of present filter
device 300, this time having upper body portion 315 and lower body
portion 316. A membrane filter 330 is shown to be sealed with the
formed body by o-rings 325. The upper and lower body portions 315
and 316 are designed so as to join and seal with the o-rings 325,
establishing conditions for sample flow to be substantially through
the membrane filter 330. For some applications, once a desired
quantity of material is captured on the filter, it may be useful to
re-suspend this material by back-flushing the filter. Once material
is re-suspended, for example, another filter device may be used to
isolate a sub-component of the material collected. Alternatively,
if access to the filter surface is desired, the upper body 315 and
the lower body 316 should be made separable using a press-fit,
threads or other convenient form of assembly.
[0036] A pressure-sensitive check valve 320 is shown in
communication with the upper body portion 315 of the filter 335.
Again, flow through the membrane filter 330 decreases with time due
to progressive obstruction of the pores by material as it collects.
The pressure-sensitive check valve 320 senses flow rate therefore,
providing a measure of the amount of material captured by the
membrane filter 330.
[0037] FIG. 3c shows an embodiment of the present invention having
a membrane filter 330 (not shown) attached on the lower surface of
the device body 310. As described in association with FIG. 3a, a
standoff 335 may be provided. In this embodiment the
pressure-sensitive check valve 370 is integrated and implemented
around the periphery of the apparatus with plastic spring tabs that
operate as poppet valves. These are further diagrammed in expanded
view. Plastic spring tab 376 has contact area 374, tension sealed
into vent hole 372 in the wall of the device body 310. Although a
single poppet valve of this type could function as a
pressure-sensitive check valve for the intended use, such
functionality has been implemented using a plurality of plastic
poppet valves 370 distributed around the periphery of filter device
300. As described in association with FIGS. 3a and 3b, applied
vacuum 360 initiates the flow of sample suspension (not shown)
through the membrane filter 330. And as material is captured on the
underside of membrane filter 330, the pressure-sensitive poppet
valves 370 are in communication with the upper side of the membrane
filter 330, so positioned so as to monitor the flow rate of
material through the membrane filter 330. The poppet valve(s) are
set to trigger at a predetermined pressure to indicate when a
desired quantity of material has been collected on the membrane
filter 330.
[0038] As discussed, the pressure-sensitive check valve 370 may be
implemented with one or more contact tabs. Compound valves of this
type may be adjusted to trigger or otherwise activate at a
predetermined pressure. Similarly, the characteristics of the valve
portion may also be made adjustable, for example, when used as a
vent or fluid pathway the diameter of the valve could be adjusted.
For some applications or reasons of manufacture, size, operating
range, reliability, sensitivity, trigger rate, etc. it may be
desirable to distribute a plurality of these plastic spring tabs
around the periphery of the device, as shown. Such tab(s) may be
affixed as separate units, be fabricated as a ring of units
designed for insertion into the device body or it may be preferable
to establish these pressure-sensitive check valve components as
part of a molding process. Again, the application, costs and other
factors may influence implementation.
[0039] FIG. 4 shows a configuration of filter devices of the
present invention for processing a plurality of samples. A vacuum
manifold 400 distributes vacuum which is further isolated via
vacuum chambers 410. Material in suspension 430 begins to be
aspirated into filter device(s) 420. Accordingly, by selecting
appropriate components, a plurality of similar or different samples
may be processed simultaneously. Alternatively, each station may be
established to capture the same amount of material, or different
amounts of material as desired, or required.
[0040] FIG. 5a shows a filter device 500 of the present invention
with a membrane filter 530 interposed between upper body 510 and
lower body 520. Sample suspension (not shown) enters through inlet
port 525, passes through the membrane filter 530 and exits via
outlet port 515. In this instance, the membrane filter 530 is
selected with sufficient deformability so as to generally conform
to the interior surface 535 of the upper device body 510 when a
desired amount of material (indicated by the reduced flow rate
through the membrane filter 530) has been captured. Accordingly,
flow is subsequently restricted to a smaller area of the membrane
filter 530, for example a single central fluid pathway, as
diagrammed.
[0041] FIG. 5b shows such a filter 530, as described in association
with FIG. 5a, having captured a desired amount of material in
region 540 and providing reduced flow through a more restricted
area of the filter 545. As desired, sample flow may continue or be
allowed to continue, for example, until area 545 occludes so as to
slow or substantially reduce or stop sample flow, as such
continuation has no subsequent effect as the desired amount of
material has been captured in area 540 of the filter. The device
may continue to draw sample as desired without substantially
affecting the desired amount of material collected in region 540.
As desired the upper body 315 and lower body 316 may be made
separable to provide filter access.
[0042] FIG. 6a shows a filter device 600 of the present invention
with a membrane filter assembly 650 interposed between upper body
610 and lower body 620. Sample suspension (not shown) enters
through inlet port 625, passes through the membrane filter assembly
650 and exits via outlet port 615. The membrane filter assembly 650
is comprised of a filter 660 and surrounding non-porous support
structure 655. In this instance, the membrane filter assembly 650
acts as a pressure transducer, responding to a reduction in flow
rate through the filter 660 as particulate material collects on the
underside of the filter 660. As described in association with FIGS.
5a and 5b, deformation of the filter, or in this instance the
membrane filter assembly 650, provides the means to alter flow in
response to the pressure differential across the membrane filter
assembly 650.
[0043] FIG. 6b shows the membrane filter assembly 650 having a
filter area 660 supported by a surrounding non-porous support
structure 655. The support structure 655 has striations 665
allowing it to deform in a triggered motion when a predetermined
pressure is sensed. As described, material collecting on the
underside of the filter 660 begins to occlude the filter 660,
contributing to a reduction in flow rate through the filter 660 and
a pressure change across the membrane filter assembly 650. When a
desired amount of material has been collected the support structure
triggers so as to conform to the inner surface as described in
association with FIG. 5a or the support structure may contact a
valve as described in association with FIGS. 3a, b and c so as to
substantially stop sample flow and therefore halt material
collection.
[0044] FIG. 6c shows a membrane filter assembly 670 having a filter
area 680 in surrounding non-porous support structure 675. The
support structure 675 has striations 685. The membrane assembly is
diagrammed in a first state which is substantially maintained until
the pressure differential across the membrane filter assembly 670
reaches a predetermined trigger point at which time the structure
toggles or deforms to a second state.
[0045] FIG. 6d shows the membrane filter assembly 670 as discussed
in association with FIG. 6c in a triggered or deformed state. As
desired or required, the membrane filter assembly 670 may itself
provide a means to alter flow when the state toggles, indicating
collection of a desired amount of material on the filter 680.
Alternatively, the state change may contact a valve, a switch or
value interfaced to a switch so that flow through the membrane may
be adjusted, or halted.
[0046] While preferred embodiments of the present invention are
shown and described, it is envisioned that those skilled in the art
may devise various modifications of the present invention without
departing from the spirit and scope of the appended claims.
* * * * *