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BACKGROUND & BRIEF SUMMARY OF THE INVENTION
Prior Art
The closest prior art of which applicant is aware is as follows:
U.S. Pat. No. 3,607,083; Thiers; Sept. 21, 1971
U.S. Pat. No. 4,233,029; Nov. 11, 1980
U.S. Pat. No. 4,254,083; Columbus; Mar. 3, 1981
U.S. Pat. No. 4,264,560; Natelson; Apr. 28, 1981
U.S. Pat. No. 4,271,119; Columbus; June 2, 1981
U.S. Pat. No. 4,310,399; Columbus; Jan. 12, 1982
U.S. Pat. No. 4,399,102; Karlberg; Aug. 16, 1983
U.S. Pat. No. 4,426,451; Columbus; Jan. 17, 1984
Although the above patents involve fluid flow systems which may utilize
capillary flow principles, the basic concept of shifting a control
fluid/principal fluid interface for the purpose of influencing or
controlling principal fluid flow is not present therein.
Technical Field of Invention
The invention is concerned with principal fluid flow control within a
capillary system, in which the flow control is effected by change in the
kind of fluid/fluid interface between the principal fluid and a control
fluid. The principal fluid and the control fluids have different surface
energy levels so as to be capable of providing a fluid/fluid interface
therebetween. The change in the kind of fluid/fluid interface, to effect
flow control of the principal fluid, is effected by reversing the
potential energy states of the principal and control fluids at the
locations where the fluid/fluid interfaces are formed, the potential
energy states being determined by the surface energy level of the
principal fluid or control fluid each in combination with the surface
energy level of the material with which it is contact at the location of
the interface in question.
More particularly, it relates to fluid flow control systems and is
concerned primarily with controlling capillary flow of one fluid
(hereinafter the principal fluid) through the intermediary of pressure
exerted on a second fluid (hereinafter the control fluid), the principal
and control fluids having different surface energy levels and being
capable of forming fluid/fluid interfaces therebetween, and wherein the
principal fluid normally flows through capillary surface means with which
it in combination presents a different potential energy state than does
the control fluid in combination with that same surface. Likewise, the
control fluid normally is in contact with capillary surface means with
which it incombination presents a different potential energy state than
does the principal fluid in combination with such surface.
The flow control of this invention is effected by shifting or moving one or
more fluid/fluid interfaces from one location, junction or border in which
the interface or interfaces are confined within capillary surface means
associated with the control fluid to another location or locations in
which the fluid/fluid interface or interfaces intrude into or are confined
to be within the capillary surface means associated with the principal
fluid.
The location or locations of an interface or interfaces, as the case may
be, is effected by pressure control of the control fluid, specifically by
variation of pressure operating upon the control fluid in such sense as to
compel a change of location of the interfaces. At some lower pressure
acting on the control fluid, the interface or interfaces will be located
at a position which permits full flow of the principal fluid and at some
higher pressure on the control fluid, the interface or interfaces will be
located to intrude into or to block the capillary means containing the
principal fluid thereby respectively to impede or to block the flow of
principal fluid.
Prior to the intrusion of the control fluid into the capillary means
containing the principal fluid, a fluid/fluid interface will be present at
a location within the capillary means for the control fluid which does not
materially impede the flow of the principal fluid. It is the intrusion of
the control fluid into the capillary means containing the principal fluid
which causes a change in location or locations of one or more fluid/fluid
interfaces so that it or they are shifted to be within the confines of the
capillary means containing the principal fluid thereby to impede or to
block the flow of the principal fluid.
It is a particular feature of this invention that the difference in
pressure which must be exerted on the control fluid to effect the
aforesaid shift in locations of the interfaces is relatively wide and is
not of critical nature. The control fluid may for example have a very low
pressure (e.g., atmospheric) acting on it when an interface is in
non-impeding location or locations. Although the pressure acting on the
control fluid when an interface is in impeding or blocking location or
locations must be increased to be greater than the pressure acting on the
principle fluid, its value may vary over a wide range or "bandwidth" as
used herein. Therefore, it is not difficult to select a value of pressure
which will effect the requisite shift of interface location.
More particularly, where an impeding or blocking fluid/fluid interface is
formed, the principal fluid operating in conjunction with the surface of
the flow passage with which it is in contact at one side of the interface
represents a different potential energy state than does the control fluid
operating in conjunction with the surface area of the flow passage with
which it is in contact on the other side of the interface. This factor is
important to the bandwidth characteristic referenced above.
According to another aspect of this invention, where the fluid/fluid
interfaces are formed, the aforesaid capillary surfaces with which the two
fluids are in contact are themselves of different surface energy levels.
For example, for a principal fluid having a higher surface energy level
than the control fluid and operating in combination with a capillary
surface means whose surface energy level is also high, such combination of
principal fluid and high surface energy level capillary means presents a
lower potential energy state than does the combination of the control
fluid and such high surface energy level capillary surface means, whereas
the opposite is the case when the principal fluid and the control fluid
are in contact with the lower surface energy level capillary surface means
within which the control fluid normally operates. Thus, it will be
appreciated that such an arrangement is conducive to the bandwidth feature
noted above. That is to say, for example, an interface which is concave
into the low surface energy capillary means will occur when the interface
is in non-impeding or non-blocking location and a concave interface into
the high surface energy capillary means will occur when the interface is
in impeding or blocking location.
More specifically, the invention is concerned with the capability of
controllably establishing one or more pressure stabilized fluid/fluid
interfaces between the principal fluid and the control fluid at at least
two or more locations within the flow passage means in order to achieve a
desired control function. To this end, the invention contemplates the
provision of at least two fluid/fluid interface locations within the flow
passage for the principal fluid, which locations are defined between
different surface energy level portions of the flow passage, each such
location or junction defining a border between these different surface
energy level portions which allows a control fluid to be introduced into
the capillary flow passage means so as to form a principal fluid/control
fluid interface stabilized by and at such border, the control fluid
serving either to restrict the flow of the principal fluid or to block
flow of the principal fluid. In the former instance, the arrangement
operates as a flow rate restrictor and in the second instance, as a
control valve which, itself, permits other and different devices to be
constructed.
The invention contemplates that the interface may be stabilized at the
location or junction between a capillary passage and another capillary
passage of substantially the same diameter, the materials defining the two
surfaces being of different surface energy levels and defining the border;
that the interface may be stabilized at the location or junction between a
capillary passage and a passage of substantially larger diameter, in which
case the smaller capillary passage itself defines the location, junction
or border which stabilizes the interface; and that the interface may be
stabilized at the junction between two surfaces of different energy
levels, which two surfaces are those defining two capillary passages which
may be of disparate diameters.
According to the present invention, plural locations, borders or junctions
as described above may be used at spaced positions within the flow passage
for the principal fluid initially to trap or isolate a predetermined or
known volume of the principal fluid and thereafter to release this
isolated volume of principal fluid for further controlled flow thereof.
This technique may be employed, for example, to meter or to pump or
displace known quantities of the principal fluid.
In a particular embodiment of the invention, a device relates to capillary
flow control and in particular to controlling such flow with respect to
extermely small volumes of a principal fluid. By extremely small volumes
of principal fluid, as used herein, is meant volumes which may be as small
as in the order of one picoliter.
Although not necessarily restricted thereto, the embodiments of the present
invention as are disclosed hereinafter are principally concerned with a
liquid/gas system in which either the liquid or the gas may operate as the
principal fluid while the other operates as the control fluid.
According to the present invention, a representative liquid/gas system
comprises a capillary flow passage means whose capillary surface is formed
by a high surface energy level material such as glass whereas the low
surface energy surface area is formed by material such as Teflon and
wherein the high surface energy level fluid is water and the low surface
energy level fluid is air. In this system, either the water or the air may
be the principal fluid.
Systems of the present invention may employ porous membranes which function
as the capillary flow passage means, in which case the junction is located
at one end of the capillary passage means which are defined by the
membrane.
The applications of the present invention are many and varied and although
a few examples of particular applications are specified hereinafter, the
invention is by no means limited thereto.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
FIG. 1 is a diagrammatic view of a fluid flow system employing the
principles of this invention;
FIG. 2 is an enlarged section of the capillary flow control unit of FIG. 1;
FIGS. 3, 3A, 4, 4A, 5 and 5A are enlarged views of single capillary
passages of FIG. 2 illustrating the locations and details of the
fluid/fluid interfaces during flow and non-flow conditions;
FIG. 6 is an enlarged section illustrating one form of a valve in accord
with this invention;
FIG. 7 is an enlarged view illustrating one form of capillary junction
illustrative of the invention;
FIG. 8 is an enlarged view illustrating another form of capillary junction;
FIG. 9 is an enlarged view of a preferred type of configuration for a
valve;
FIG. 10 is identical to FIG. 9 but showing the valve in open condition;
FIG. 11 is a view illustrating another form which the valve may take;
FIG. 12 is an enlarged perspective view illustrating a valve construction
suitable for a microsystem;
FIG. 13 is an enlarged section illustrating a metering device in accord
with the invention;
FIG. 14 illustrates the device in FIG. 13 during transfer of the metered
fluid;
FIGS. 15 and 16 are directed to another embodiment of a metering system;
FIG. 17 is a diagrammatic view illustrating the principles of a microsystem
according to this invention;
FIG. 18 is a diagrammatic view of another microsystem according to this
invention; and
FIG. 19 is a section illustrating a dynamic flow restrictor in accord with
this invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 illustrates an embodiment of the present invention utilizing the
flow control principles specified herein. This system is intended for
macro flow control, that is, it is intended to operate to control
relatively large flows as opposed to micro flow control where, for
example, the flow may be restricted to be within a very small capillary
system as might be embodied in a microscope slide for individual cell
manipulation.
As illustrated, the system shown includes the valve mechanism indicated
generally by the reference character 10 and shown in more detail in FIG. 2
in association with a variable pressure pump 12 which pumps water under
pressure in the discharge line 14, the pick-up being through the inlet
conduit extending to the water reservoir indicated generally by the
reference character 18. Thus, in this case, water is the principal fluid
and its flow is controlled by the valve 10 by air acting as the control
fluid so that at the discharge flow passage conduit 20, there is a flow or
no flow condition dependent upon the condition of the valve 10 which will
be described with greater particularity hereinbelow. The system also
includes a variable pressure air compressor 22 discharging through a
manually controlled valve 24 to the air line 26 connected with the valve
10. The manually controlled valve 24 is positionable so that either the
pressure provided by the compressor 22 is present in the line 26 or the
line 26 is vented to atmosphere as indicated by the vent passage 28. The
gauge G measures the pressure in the line 26 when the air compressor 22 is
connected thereto through the valve 24.
The valve 10 shown in FIG. 2 is constructed in accord with the principles
of this invention. To this end, the three polymethylmethacrylate plates
30, 31 and 32 are constructed and arranged so that when layered together
as shown in FIG. 2, the three porous membranes 33, 34 and 35 are held in
position as shown. The membrane 33 is provided with a chamber 36 above it
and a chamber 37 below it. Similarly, the membrane 34 is provided with a
chamber 38 above it and a chamber 39 below it and, lastly, the membrane 35
is likewise provided with a chamber 40 above it and a chamber 41 below it.
The three chambers 36, 38 and 40 are in communication respectively with
the lines 14, 20 and 26 and it will be seen that the three chamber 37, 39
and 42 are in communication with the common chamber 43 substantially as is
shown.
As will be appreciated, the system shown in FIG. 2 is a water/air system.
FIGS. 3 and 3A are somewhat idealized illustrations depicting a single one
of the capillary passages through the porous membrane 33. Likewise, FIGS.
4 and 4A are idealized and illustrate a single one of the capillary
passages through the porous membrane 34 and, lastly, FIGS. 5 and 5A show
idealized representations of a single one of the capillary passages
through the porous membrane 35.
FIGS. 3, 4 and 5 illustrate the conditions at the capillaries of the
several membranes 33, 34 and 35 when the valve 10 is in the shut-off
condition. The porous membranes 33 and 34 are made of Nylon and are
wettable by the principal fluid, in this instance, water. The membrane 35,
however is made of Teflon and is non-wettable by the principal fluid
water. Thus, when the line 26 is pressurized, at the pressure P2, the air
will initially flow through the porous membrane 35 from the chamber 40 to
the chamber 52 and thence to the chamber 43 to displace water therefrom
which is forced to pass through the two membranes 33 and 34 until the
conditions of FIGS. 3 and 4 are obtained. As shown in FIG. 3, the water
pressure P1 supplied by the pump 12 over the line 14 and filling the
chamber 36 is opposed at one end of the capillary passage CT1 so that the
air in the chamber 37 below the membrane 33 forms a meniscus at the lower
end of the capillary passage CP1 as is illustrated in FIG. 3 and which
meniscus defines the water/air interface IF1 as illustrated. It can be
shown that if the pressure P2 slightly exceeds the pressure P1, the
interface IF1 is stabilized and will be located at the lower end of the
capillary passage CP1 as is illustrated in FIG. 3 and correspondingly, the
flow of water through the line 14, through the membrane 33 and into the
chamber 43 and thence upwardly through the membrane 34 to the line 20 will
be terminated. At the same time, as is illustrated in FIG. 4, the water
pressure head P operating in opposition to the air pressure P2 in the
chamber 39 will form a further water/air interface IF2 as is illustrated,
thus preventing escape of air from the chamber 43 and 39 through the
porous membrane 34. In this condition of the valve, the capillary passage
CP3 through the membrane 35 will pass the air under the pressure P2
substantially as is shown, it being appreciated that the porous membrane
35 is made of Teflon which is non-wettable by the principal fluid water.
When the manual valve 24 is vented to atmosphere and the line 26 therefore
is at atmospheric pressure, the conditions of FIGS. 3A, 4A and 5A prevail
and flow of the principal fluid will pass from the inlet line 14, through
the valve 10 and out the discharge line 20. As shown in FIGS. 3A and 4A,
water will flow first from the chamber 36 and through the capillary
passage CP1 into the chamber 37 and thence into the chamber 43 and into
the chamber 39 where it will pass through the capillary passage CP2 and
thence into the chamber 38 and out the outlet line 20. At the same time,
backflow of water from the chamber 42 to the chamber 40 and the vented air
line 26 is prevented by virtue of the Teflon membrane 35 as is illustrated
in FIG. 5A, the capillary passage CP3, as is illustrated in FIG. 5A,
allowing the atmospheric pressure in the chamber 40 to oppose the water
pressure P1 in the chamber 42 to form a water meniscus within the
capillary passage CP3 which defines the interface IF3 substantially as is
shown.
The Table below illustrates data gathered in operation of the system of
FIG. 1. The pump 12 is an FMI Lab Pump, serial no. 4p918, rated at a
maximum flow of 3 ML/MIN at 60 PSI and was obtained from Fluid Metering,
Inc., Oyster Bay, N.Y. The compressor 22 is of standard design capable of
providing air pressure at various ratings from 0 to 80 PSI. In the Table
below, the settings of the water pump produce the flow rates as indicated.
TABLE 1
______________________________________
Water Pump
System Control Gas
Setting (0-9)
Pressure (PSI)
Observation of
______________________________________
2 Vented to ATM Water Flow of 0.8
ML/MIN
2 20-80 Flow Stopped
4 Vented to ATM Water Flow of 1.4
ML/MIN
4 30-80 Flow Stopped
6 Vented to ATM Water Flow of 2
ML/MIN
6 40-80 Flow Stopped
8 Vented to ATM Water Flow of 2.5
ML/MIN
8 55-80 Flow Stopped
______________________________________
The above table illustrates the bandwidth feature of this invention. In
each case of controlled flow, the pressure required to terminate flow
could be varied over a wide range without causing the blocking flow
interfaces to lose stability. The upper value of 80 psi in each case was
dictated by the maximum pressure acquired by the air compressor, but even
at a flow rate near the maximum, a pressure range of 25 psi was still
available for control.
FIGS. 1-5A illustrate the basic principles of the present invention wherein
fluid flow control is obtained by controlling capillary flow of the
principal fluid through the intermediary of the control fluid, the
principal and control fluids having different surface energy levels and
being capable of forming a fluid/fluid interface therebetween. In the
embodiment shown in FIGS. 1-5A, not only does the water have a higher
surface energy level than does the air, but the water operating in
conjunction with the Nylon membrane 33 and 34 which are wettable by the
water cooperate in combination therewith to provide a lower potential
energy state for that combination than for the combination of the Nylon
with air. Similarly, for the Teflon membrane 35, its potential energy
state in combination with air is lower than that of the water in
combination with the Teflon. Thus, the stable menisci and corresponding
fluid/fluid interfaces IF1, IF2 and IF3 are defined, substantially as is
described and shown.
A modified form of the control valve shown in FIG. 2 is illustrated in FIG.
6 which, as is the case with the FIG. 2 system is adapted to handle
relatively large flow rates of the principal fluids. In this case, the
three lines 14, 20 and 26 form a Tee with the materials of the tubes 14
and 20 being formed of glass and being provided with porous glass windows
50 and 51 which correspond respectively with the membranes 33 and 34 by
providing a plurality of capillary passages CP1 and a plurality of
capillary passages CP2, as is shown. The conduit 26 is formed of Teflon
material 52 and is provided with a Teflon window indicated generally by
the reference character 53 which corresponds to the Teflon membrane 35 to
provide the plurality of capillary passages CP3. As is the case with FIG.
2, the FIG. 6 construction shows a fluid control system in which water is
the principal fluid and air is the control fluid and shut-off is obtained
as depicted in FIG. 6.
FIGS. 1-6 illustrate one kind of junction which is capable of defining a
border at which a fluid/fluid interface is stabilized. This is further
illustrated in FIG. 7 wherein the capillary tube 60 is joined with the
capillary tube 61. Both of these capillary tubes are shown as formed of
high energy material such as glass and the fluid 1 or principal fluid is
water whereas the fluid 2 or control fluid may be air or another gas,
i.e., it is a fluid whose surface energy level is different from (lower
than) the surface energy level of water. The junction at which the
interface IF4 is stabilized is defined at the mouth of the capillary
passage means defined by the capillary 60 because of the abrupt opening
thereof into the much larger passage defined by the capillary 61. The
capillary passage defined by the tube 60 is of 10 microns and the inside
diameter of the tube 61 is of 20 microns in the particular situation
shown. The capillary surfaces are more wettable by the water than by the
gas and for this reason little or no principal fluid pressure is required
to displace the control fluid from the larger capillary 61. However,
control fluid 2 pressure is required to displace the principal fluid 1
from either capillary, this fluid 2 pressure being inversely related to
the capillary radius. For the two fluid system such as water and air in
the capillaries as described above made of glass, the transition pressure
at the junction of the two capillaries is about 6.0 PSI. That is to say,
the control fluid pressure must exceed the principal fluid pressure by
about 6.0 PSI in order to form the stabilized fluid/fluid interface IF4
illustrated. If the materials of the two capillaries 60 and 61 are such as
to be non-wettable by the principal fluid, i.e., made of low surface
energy material such as Teflon, similar transition pressures as expressed
above obtain but with opposite polarity because the fluids 1 and 2
exchange surface energy properties. Stated otherwise, the interface IF4
would be convcave into the confines of the capillary 61 but would still be
stabilized at the junction defined at the mouth of the capillary 60. The
reason for the reversal of direction of the interface is that the
potential energy state for the combination of the high surface energy
level fluid (water) and the now low surface energy level capillary surface
(Teflon) provides a higher potential energy state than does the low
surface energy level fluid (air) in combination with the low surface
energy level Teflon, rather than the reverse for the case when the glass
is present.
It will be appreciated that the junction illustrated in FIG. 7 is akin to
the plurality of junctions achieved in FIGS. 1-6 at each of the capillary
passages illustrated. That is to say, the junction is such as to define a
border at the downstream end of the principal flow path defined by the
capillary means with which it is associated whereat the interface is
formed and stabilized.
A further type of junction is shown in FIG. 8 wherein the glass capillary
tube 70 abuts and adjoins the Teflon capillary tube 71, the capillary
passages being of substantially the same internal diameter as is shown. In
this case, the junction is defined between two materials of different
surface energy levels to provide a border at which the interface IF5 is
formed and stabilized. In the case of FIG. 8, the presence of the
capillary 71 providing a capillary surface of lower surface energy, even
though it is of the same diameter as the capillary 70, operates to produce
the same effect as the abrupt change in diameter in FIG. 7. The high
surface energy level fluid (water) operates in combination with the high
surface energy level capillary surface (glass) to provide a lower
potential energy state than the potential energy state of the low surface
energy level fluid (air) in combination with the high surface energy level
capillary surface afforded by the glass at the capillary junction.
Therefore, the interface IF5 is concave into the capillary 70, as shown
and the border defined at the junction is, as is also the case in FIG. 7,
sharply and well defined.
FIGS. 9 and 10 show a control valve construction which is functionally
equivalent to those shown in FIGS. 1-6, although, the principal fluid flow
rate in this case is extremely small because all of the passages
illustrated in FIGS. 9 and 10 are of capillary size. As shown in FIG. 9,
there are two capillary glass tubes indicated by the reference characters
90 and 91 and joining them is a Teflon capillary tube 92 having a Tee
capillary stem 93 joined thereto substantially as is shown. There are
three possible locations for stabilized interfaces in this configuration,
two which are indicated at IF6 and IF7 in FIG. 9 and the other of which is
at IF8 as in FIG. 10. The flow blocking condition is shown in FIG. 9
wherein the control fluid pressure stabilizes the two interfaces IF6 and
IF7 at the locations defined at the borders provided at the capillary
junctions formed where the disparate surface energy level materials 90, 92
and 91, 92 join. The flow condition is illustrated in FIG. 10 where the
control fluid pressure is vented so that the interface IF8 is now located
or formed at the border defined at the junction between the Tee stem 93
and the main body portion 92. It should be noted that this junction at
which the interface IF8 is located in FIG. 10 is akin to the type of
junction illustrated in FIG. 7.
FIG. 11 is substantially identical to FIGS. 9 and 10 but, in this case, the
Teflon capillary 92' is of larger internal diameter to provide a junction
situation at which the interfaces IF9 and IF10 are located which is more
in conformity with the description according to FIG. 7. The border defined
at the junction provided at the mouth of the Tee stem 93 and whereat an
interface is located in the flow condition of the valve is identical to
the situation for the interface IF8 in FIG. 10. The advantage of this
construction is that the control gas pressure has a wider "bandwidth" as
was previously described, i.e., its pressure is not required to be so
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