U.S. patent application number 13/465927 was filed with the patent office on 2012-11-08 for ganging electrokinetic pumps.
Invention is credited to Kenneth R. Hencken, Robert B. Lewis, Tuan Quoc Mai, Kenneth Kei-ho Nip, Doris Sun-Chia Shieh.
Application Number | 20120282112 13/465927 |
Document ID | / |
Family ID | 47090350 |
Filed Date | 2012-11-08 |
United States Patent
Application |
20120282112 |
Kind Code |
A1 |
Nip; Kenneth Kei-ho ; et
al. |
November 8, 2012 |
GANGING ELECTROKINETIC PUMPS
Abstract
An electrokinetic system includes a first electrokinetic pump, a
second electrokinetic pump, a reservoir having delivery fluid
therein, and a controller. The first electrokinetic pump is
configured to provide a first range of flow rates. The second
electrokinetic pump is configured to provide a second range of flow
rates. The second range includes flow rates that are greater than
the flow rates of the first range. The reservoir is fluidically
attached to the first electrokinetic pump and the second
electrokinetic pump. The controller is configured to apply voltage
to one of the first or second electrokinetic pumps and then apply
voltage to the other of the first or second electrokinetic pumps so
as to vary the flow rate range of delivery fluid pump from the
reservoir.
Inventors: |
Nip; Kenneth Kei-ho;
(Redwood City, CA) ; Hencken; Kenneth R.;
(Pleasanton, CA) ; Shieh; Doris Sun-Chia; (Santa
Clara, CA) ; Lewis; Robert B.; (Pleasanton, CA)
; Mai; Tuan Quoc; (San Ramon, CA) |
Family ID: |
47090350 |
Appl. No.: |
13/465927 |
Filed: |
May 7, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61482949 |
May 5, 2011 |
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Current U.S.
Class: |
417/48 |
Current CPC
Class: |
F04B 17/00 20130101;
F04B 43/043 20130101; F04B 23/06 20130101 |
Class at
Publication: |
417/48 |
International
Class: |
F04B 17/03 20060101
F04B017/03 |
Claims
1. An electrokinetic pump system, comprising: a reservoir
configured to have a delivery fluid therein; a first electrokinetic
pump assembly fluidically connected to the reservoir and configured
to pump the delivery fluid from the reservoir at a first range of
flow rates; a second electrokinetic pump assembly fluidically
connected to the reservoir and configured to pump the delivery
fluid from the reservoir at a second range of flow rates, the
second range including flow rates that are greater than the flow
rates of the first range; and a controller configured to apply
voltage to one of the first or second electrokinetic pump
assemblies and then apply voltage to the other of the first or
second electrokinetic pump assemblies so as to vary the flow rate
of delivery fluid pumped by the electrokinetic pump system.
2. The electrokinetic pump system of claim 1, wherein a total flow
rate range of the system is between approximately 0.0001 ml/hr and
1,200 ml/hr.
3. The electrokinetic pump system of claim 2, wherein the total
flow rate range of the system is between approximately 0.0001 ml/hr
and 1,000 ml/hr.
4. The electrokinetic pump system of claim 3, wherein the total
flow rate range of the system is between approximately 0.01 ml/hr
and 30 ml/hr.
5. The electrokinetic system of claim 1, further comprising a third
electrokinetic pump assembly fluidically connected to the reservoir
and configured to provide a third range of flow rates, the third
range of flow rates including flow rates that are greater than the
flow rates of the second range, wherein the controller is
configured to apply voltage to one of the first or second or third
electrokinetic pump assemblies and then apply voltage to the
another of the first or second electrokinetic pump assemblies so as
to vary the flow rate of delivery fluid pumped by the
electrokinetic pump system.
6. The electrokinetic system of claim 1, wherein the flow rate
range of the first electrokinetic pump assembly is between
approximately 0.01 and 5 ml/hr and the flow rate range of the
second electrokinetic pump assembly is between approximately 0.1
ml/hr and 15 ml/hr.
7. The electrokinetic system of claim 1, wherein the first and
second pump assemblies are electrically connected in parallel.
8. The electrokinetic system of claim 1, wherein the first
electrokinetic pump assembly includes a first pressure sensor
configured to detect a flow rate of delivery fluid pumped with the
first electrokinetic pump assembly, and wherein the second
electrokinetic pump assembly includes a second pressure sensor
configured to detect a flow rate of delivery fluid pumped with the
second electrokinetic pump assembly.
9. The electrokinetic system of claim 1, wherein the first
electrokinetic pump assembly includes a first check valve to
control the flow rate of delivery fluid pumped from the first
electrokinetic pump assembly, and wherein the second electrokinetic
pump assembly includes a second check valve configured to control
the flow rate of delivery fluid pumped from the second
electrokinetic pump assembly.
10. The electrokinetic system of claim 1, wherein the controller is
further configured to apply voltage to both of the first and second
electrokinetic pump assemblies simultaneously to increase the flow
rate of delivery fluid pumped by the electrokinetic pump
system.
11. A method of pumping fluid in an electrokinetic pump system,
comprising: applying voltage with a controller to a first
electrokinetic pump assembly to pump delivery fluid from a
reservoir at a first flow rate; and applying voltage with the
controller to a second electrokinetic pump assembly to pump
delivery fluid from the reservoir at a second flow rate, the second
flow rate different than the first flow rate.
12. The method of claim 11, wherein a total flow rate range of the
electrokinetic pump system is between approximately 0.0001 ml/hr
and 1,200 ml/hr.
13. The method of claim 12, wherein the total flow rate range of
the electrokinetic pump system is between approximately 0.0001
ml/hr and 1,000 ml/hr.
14. The method of claim 13, wherein the total flow rate range of
the electrokinetic pump system is between approximately 0.01 ml/hr
to 30 ml/hr.
15. The method of claim 11, further comprising applying voltage
with the controller to a third electrokinetic pump assembly to pump
delivery fluid from the reservoir at a third flow rate, the third
flow rate different than the first and second flow rates.
16. The method of claim 11, wherein a flow rate range of the first
electrokinetic pump assembly is between approximately 0.01 ml/hr
and 5 ml/hr, and wherein a flow rate range of the second
electrokinetic pump assembly is between approximately 0.1 ml/hr and
15 ml/hr.
17. The method of claim 11, wherein the first and second
electrokinetic pump assemblies are electrically connected in
parallel.
18. The method of claim 11, further comprising measuring the flow
rate of delivery fluid pumped by the first electrokinetic pump
assembly with a first pressure sensor and measuring the flow rate
of delivery fluid pumped by the second electrokinetic pump assembly
with a second pressure sensor.
19. The method of claim 11, further comprising controlling the flow
of delivery fluid pumped by the first electrokinetic pump assembly
with a first check valve and controlling the flow of delivery fluid
pumped by the second electrokinetic pump assembly with a second
check valve.
20. The method of claim 11, wherein the voltage is applied with the
controller to the first and second electrokinetic pump assemblies
simultaneously to increase the flow rate of delivery fluid pumped
by the electrokinetic pump system.
21. An electrokinetic pump system comprising: a reservoir
configured to have a delivery fluid therein; a first electrokinetic
pump assembly fluidically connected to the reservoir and configured
to pump the delivery fluid from the reservoir; a second
electrokinetic pump assembly fluidically connected to the reservoir
and configured to pump the delivery fluid from the reservoir; and a
controller configured to apply voltage in a first cycle to the
first electrokinetic pump assembly and to apply voltage in a second
cycle to a second electrokinetic pump assembly, the controller
configured to stagger the start-time of the first and second cycles
so as to provide substantially continuous flow of the delivery
fluid from the electrokinetic pump system.
22. The electrokinetic pump system of claim 21, further comprising
a third electrokinetic pump and a fourth electrokinetic pump,
wherein the reservoir is fluidically attached to the third and
fourth electrokinetic pumps, and wherein the controller is
configured to apply voltage in a third cycle to the third
electrokinetic pump and to apply voltage in a fourth cycle to the
fourth electrokinetic pump, the controller configured to stagger
the start-times of the first, second, third, and fourth cycles so
as to provide substantially continuous flow of the delivery fluid
pumped from the electrokinetic pump system.
23. The electrokinetic pump system of claim 22, wherein the
controller is configured to synchronize the cycles such that the
first cycle includes an intake or outtake stroke only when the
second cycle includes a zero-voltage phase, the second cycle
includes an intake or an outtake stroke only when the first cycle
includes a zero-voltage phase, the third cycle includes an intake
or an outtake stroke only when the fourth cycle includes a
zero-voltage phase, the fourth cycle includes an intake or an
outtake stroke only when the third cycle includes a zero-voltage
phase.
24. The electrokinetic pump system of claim 23, wherein the
controller is further configured to synchronize the cycles such
that the first cycle includes an intake stroke when the third cycle
includes an outtake stroke, and the third cycle includes an intake
stroke when the first cycle includes an outtake stroke.
25. The electrokinetic pump system of claim 21, wherein the
controller is configured to synchronize the cycles such that the
first cycle includes an intake stroke while the second cycle
includes an intake stroke.
26. The electrokinetic pump system of claim 25, wherein the third
cycle includes an intake stroke while the second cycle includes an
intake stroke.
27. The electrokinetic pump system of claim 26, wherein the fourth
cycle includes an intake stroke while the third cycle includes an
intake stroke.
28. The electrokinetic pump system of claim 21, wherein the first
electrokinetic pump assembly includes a first electrokinetic engine
and two electrokinetic pumps, and wherein the second electrokinetic
pump assembly includes a second electrokinetic engine and two
additional electrokinetic pumps, the first and second engines being
reciprocating engines.
29. The electrokinetic pump system of claim 1, wherein the
controller is configured such that an instantaneous flow rate of
the delivery fluid pumped from the electrokinetic pump system never
drops to zero during pumping of the delivery fluid.
30. The electrokinetic pump system of claim 21, wherein the
controller is configured such that an instantaneous flow rate
delivery fluid pumped from the electrokinetic pump system varies by
less than 20% from a target flow rate.
31. The electrokinetic pump system of claim 30, wherein the
controller is configured such that the instantaneous flow rate
varies by less than 10%.
32. The electrokinetic pump system of claim 31, wherein the
controller is configured such that the instantaneous flow rate
varies by less than 5%.
33. A method of pumping fluid with an electrokinetic pump system,
comprising: applying voltage in a first cycle to a first
electrokinetic pump assembly to pump delivery fluid from a
reservoir with the first electrokinetic pump assembly; applying
voltage in a second cycle to a second electrokinetic pump assembly
to pump delivery fluid from the reservoir with the second
electrokinetic pump assembly; wherein the start-time of the second
cycle is delayed relative to the start-time of the first cycle so
as to provide substantially continuous flow of the delivery fluid
from the electrokinetic pump system.
34. The method of claim 33, further comprising applying voltage in
a third cycle to a third electrokinetic pump assembly to pump
delivery fluid from the reservoir with the third electrokinetic
pump assembly and applying voltage in a fourth cycle to a fourth
electrokinetic pump assembly to pump delivery fluid from the
reservoir with the fourth electrokinetic pump assembly, wherein the
start-times of third and fourth cycles are delayed relative to the
start-time of the first and second cycle so as to provide
substantially continuous flow of the delivery fluid from the
electrokinetic pump system.
35. The method of claim 34, further comprising synchronizing the
cycles such that the first cycle includes an intake or outtake
stroke only when the second cycle includes a zero-voltage phase,
the second cycle includes an intake or an outtake stroke only when
the first cycle includes a zero-voltage phase, the third cycle
includes an intake or an outtake stroke only when the fourth cycle
includes a zero-voltage phase, the fourth cycle includes an intake
or an outtake stroke only when the third cycle includes a
zero-voltage phase.
36. The method of claim 35, further comprising synchronizing the
cycles such that the first cycle includes an intake stroke when the
third cycle includes an outtake stroke, and the third cycle
includes an intake stroke when the first cycle includes an outtake
stroke.
37. The method of claim 34, further comprising synchronizing the
cycles such that the first cycle includes an intake stroke while
the second cycle includes an intake stroke.
38. The method of claim 37, further comprising synchronizing the
cycles such that the third cycle includes an intake stroke while
the second cycle includes an intake stroke.
39. The method of claim 38, wherein the fourth cycle includes an
intake stroke while the third cycle includes an intake stroke.
40. The method of claim 33, wherein, when applying the voltage in
the first cycle and the second cycle, an instantaneous flow rate of
delivery fluid from the electrokinetic pump system never drops to
zero.
41. The method of claim 33, wherein applying the voltage in the
first cycle and the second cycle causes variations in an
instantaneous flow rate of the delivery fluid from the
electrokinetic pump system of less than 20% from a target flow
rate.
42. The method of claim 41, wherein the instantaneous flow rate
varies by less than 10%.
43. The method of claim 42, wherein the instantaneous flow rate
varies by less than 5%.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 61/482,949, filed May 5, 2011, and titled "GANGING
ELECTROKINETIC PUMPS," which is herein incorporated by reference in
its entirety.
INCORPORATION BY REFERENCE
[0002] All publications and patent applications mentioned in this
specification are herein incorporated by reference to the same
extent as if each individual publication or patent application was
specifically and individually indicated to be incorporated by
reference.
FIELD
[0003] This application relates generally to methods for delivery a
volume of fluid with a pump system. More specifically, the
disclosure relates to a pump system including a plurality of
electrokinetic pumps ganged together.
BACKGROUND
[0004] Electrokinetic ("EK") or electro-osmotic manipulations of
fluids represent the state-of-the art in controlled, high
precision, small volume fluid transport and handling.
Electro-osmosis involves the application of an electric potential
to an electrolyte, in contact with a dielectric surface, to produce
a net flow of the electrolyte.
[0005] EK pumps have widespread and wide ranging applications, such
as for chemical analysis, drug delivery, and analyte sampling.
However, there are several design challenges associated with using
EK pumps, such as obtaining a high flow rate, a large range of flow
rates from a single EK pump system, and achieving continuous
flow.
[0006] Accordingly, the present disclosure is directed to a pump
system having a plurality of EK pumps ganged together to achieve a
high flow rates, a large range of flow rates, and/or substantially
continuous flow.
SUMMARY OF THE DISCLOSURE
[0007] In general, in one aspect, an electrokinetic system includes
a first electrokinetic pump, a second electrokinetic pump, a
reservoir having delivery fluid therein, and a controller. The
first electrokinetic pump is configured to provide a first range of
flow rates. The second electrokinetic pump is configured to provide
a second range of flow rates. The second range includes flow rates
that are greater than the flow rates of the first range. The
reservoir is fluidically attached to the first electrokinetic pump
and the second electrokinetic pump. The controller is configured to
apply voltage to one of the first or second electrokinetic pumps
and then apply voltage to the other of the first or second
electrokinetic pumps so as to vary the flow rate range of delivery
fluid pump from the reservoir.
[0008] In general, in one aspect, a method of pumping fluid
includes applying voltage with a controller to a first
electrokinetic pump to pump delivery fluid from a reservoir at a
first flow rate; and applying voltage with the controller to a
second electrokinetic pump to pump delivery fluid from the
reservoir at a second flow rate, the second flow rate different
than the first flow rate.
[0009] These and other embodiments can include one or more of the
following features. The flow rate range of the electrokinetic
system can be from approximately 0.0001 mL/hr to 1,200 mL/hr, such
as 0.0001 mL/hr to 1,000 mL/hr, for example 0.01 mL/hr to 30 mL/hr.
The system can further include a third electrokinetic pump
configured to provide a third range of flow rates. The third range
can include flow rates that are greater than the flow rates of the
second range. The reservoir can be fluidically connected to the
third electrokinetic pump, and wherein the controller is configured
to apply voltage to one of the first or second or third
electrokinetic pumps and then apply voltage to the another of the
first or second electrokinetic pumps so as to vary the flow rate
range of delivery fluid pumped from the reservoir. The flow range
of the first electrokinetic pump can be approximately 0.01-5 mL/hr,
and the flow rate of second electrokinetic pump can be
approximately 0.1-15 mL/hr. The first and second pumps can be
electrically connected in parallel. The first electrokinetic pump
can include a first pressure sensor, and the second electrokinetic
pump can include a second pressure sensor. The first electrokinetic
pump can include a first check valve, and the second electrokinetic
pump can include a second check valve. The controller can be
configured to apply voltage to both of the first and second
electrokinetic pumps simultaneously to increase the flow rate of
delivery fluid pumped from the reservoir.
[0010] In general, in one aspect, an electrokinetic system includes
a first electrokinetic pump and a second electrokinetic pump, a
reservoir having delivery fluid therein, and a controller. The
reservoir is fluidically attached to the first electrokinetic pump
and the second electrokinetic pump. The controller is configured to
apply voltage in a first cycle to the first electrokinetic pump and
to apply voltage in a second cycle to a second electrokinetic pump.
The controller is further configured to stagger the start-time of
the first and second cycles so as to provide substantially
continuous flow of the delivery fluid from the reservoir.
[0011] In general, in one aspect, a method of pumping includes
applying voltage in a first cycle to a first electrokinetic pump
and applying voltage in a second cycle to a second pump. The first
and second electrokintic pumps are fluidically connected to a
reservoir having a delivery fluid therein. The start-time of the
second cycle is delayed relative to the start-time of the first
cycle so as to provide substantially continuous flow of the
delivery fluid from the reservoir.
[0012] These and other embodiments can include one or more of the
following features. The system can further include a third
electrokinetic pump and a fourth electrokinetic pump. The reservoir
can be fluidically attached to the third and fourth electrokinetic
pumps. The controller can be configured to apply voltage in a third
cycle to the third electrokinetic pump and to apply voltage in a
fourth cycle to the fourth electrokinetic pump. The controller can
be configured to stagger the start-times of the first, second,
third, and fourth cycles so as to provide substantially continuous
flow of the delivery fluid from the reservoir. The controller can
be configured to synchronize the cycles such that the first cycle
includes an intake or outtake stroke only when the second cycle
includes a zero-voltage phase, the second cycle includes an intake
or an outtake stroke only when the first cycle includes a
zero-voltage phase, the third cycle includes an intake or an
outtake stroke only when the fourth cycle includes a zero-voltage
phase, the fourth cycle includes an intake or an outtake stroke
only when the third cycle includes a zero-voltage phase. The
controller can be further configured to synchronize the cycles such
that the first cycle includes an intake stroke when the third cycle
includes an outtake stroke, and the third cycle includes an intake
stroke when the first cycle includes an outtake stroke. The
controller can be configured to synchronize the cycles such that
the first cycle includes an intake stroke while the second cycle
includes an intake stroke. The third cycle can include an intake
stroke while the second cycle includes an intake stroke. The fourth
cycle can include an intake stroke while the third cycle includes
an intake stroke. The first electrokinetic pump can be connected to
a first electrokinetic engine, and the first electrokinetic engine
can be further connected to a third electrokinetic pump. The second
electrokinetic pump can be connected to a second electrokinetic
engine, and the second electrokinetic engine can be further
connected to a fourth electrokinetic pump. The first and second
engines can be reciprocating engines. The instantaneous flow rate
can never drop to zero during the delivery of fluid. The
instantaneous flow rate of the system can vary by less than 20%
from a target flow rate, such as less than 10%, for example less
than 5%.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The novel features of the invention are set forth with
particularity in the claims that follow. A better understanding of
the features and advantages of the present invention will be
obtained by reference to the following detailed description that
sets forth illustrative embodiments, in which the principles of the
invention are utilized, and the accompanying drawings of which:
[0014] FIG. 1 is a cross-sectional diagram of an EK pump
assembly.
[0015] FIG. 2A shows an exemplary graph of voltage vs. time for an
EK pump assembly. FIG. 2B shows the corresponding flow rate profile
vs. time.
[0016] FIG. 3 shows a schematic of a ganged EK pump system having a
plurality of EK pump assemblies connected together.
[0017] FIG. 4 shows a schematic a ganged EK pump system having two
EK pump assemblies connected hydrodynamically and electrically in
parallel.
[0018] FIG. 5A shows an exemplary graph of voltage vs. time for the
ganged EK pump system of FIG. 4. FIG. 5B shows the corresponding
flow rate profile vs. time.
[0019] FIG. 6 shows a schematic of a ganged EK pump system having
two EK pump assemblies connected hydrodynamically in parallel and
controlled by a single controller.
[0020] FIG. 7A shows an exemplary graph of voltage vs. time for the
ganged EK pump system as shown in FIG. 6. FIG. 7B shows the
corresponding flow rate profile vs. time.
[0021] FIG. 8 shows a schematic of a ganged EK pump system having
two EK pump assemblies connected hydrodynamically in parallel and
having distributed control.
[0022] FIG. 9A shows an exemplary graph of voltage vs. time for a
ganged EK pump system having four EK pump assemblies connected as
shown in FIG. 8 with no overlap in application of voltage. FIG. 9B
shows the corresponding flow rate profile vs. time.
[0023] FIG. 10A shows an exemplary graph of voltage vs. time for a
ganged EK pump system having four EK pump assemblies connected as
shown in FIG. 8 with overlap in application of voltage. FIG. 10B
shows the corresponding flow rate profile vs. time.
[0024] FIG. 11 shows a schematic of a ganged EK pump system having
two reciprocating EK engines configured to run four electrokinetic
pumps that are connected together hydrodynamically in parallel.
[0025] FIG. 12A shows an exemplary graph of voltage vs. time for
the ganged EK pump system of FIG. 11 with no overlap in application
of voltage. FIG. 12B shows the corresponding flow rate profile vs.
time.
DETAILED DESCRIPTION
[0026] Certain specific details are set forth in the following
description and figures to provide an understanding of various
embodiments of the invention. Certain well-known details,
associated electronics and devices are not set forth in the
following disclosure to avoid unnecessarily obscuring the various
embodiments of the invention. Further, those of ordinary skill in
the relevant art will understand that they can practice other
embodiments of the invention without one or more of the details
described below. Finally, while various processes are described
with reference to steps and sequences in the following disclosure,
the description is for providing a clear implementation of
particular embodiments of the invention, and the steps and
sequences of steps should not be taken as required to practice this
invention.
[0027] Referring to FIG. 1, an electrokinetic ("EK") pump assembly
100 includes an EK pump 101 connected to an EK engine 103. The EK
engine 103 includes a first chamber 102 and a second chamber 104
separated by a porous dielectric material 106, which provides a
fluidic path between the first chamber 102 and the second chamber
104. Capacitive electrodes 108a and 108b are disposed within the
first and second chambers 102, 104, respectively, and are situated
adjacent to or near each side of the porous dielectric material
106. The EK engine 103 includes a movable member 110 in the first
chamber 102, opposite the electrode 108a. The moveable member 110
can be, for example, a flexible impermeable diaphragm. A pump fluid
(or "engine fluid"), such as an electrolyte, can fill the EK
engine, such as be present in the first and/or second chambers 102
and 104, including the space between the porous dielectric material
106 and the capacitive electrodes 108a and 108b. The capacitive
electrodes 108a and 108b are in communication with an external
voltage source, such as through lead wires or other conductive
media.
[0028] The EK pump 101 includes a delivery chamber 122 and a
movable member 113 having a first edge 112 contacting the delivery
chamber 122 and a second edge 111 contacting the second chamber
104. In some embodiments, the first and second edges 112, 111 are
flexible diaphragms having a mechanical piston therebetween. In
other embodiments, the first and second edges 112, 111 are flexible
diaphragms having a gel material therebetween. Gel couplings are
described further in U.S. Provisional Patent Application No.
61/482,889, filed May 5, 2011, and titled "GEL COUPLING FOR
ELECTROKINETIC DELIVERY SYSTEMS," and U.S. patent application Ser.
No. ______, filed herewith, and titled "GEL COUPLING FOR
ELECTROKINETIC DELIVERY SYSTEMS," the contents of both of which are
incorporated herein by reference. In other embodiments, the first
and second edges 112, 111 are edges of a single flexible member or
diaphragm.
[0029] The delivery chamber 122 can include a delivery fluid, such
as a drug or medication, e.g., insulin or pain management
medications, or a cleansing fluid, such as a wound cleansing fluid,
supplied to the delivery chamber 122 from a fluid reservoir 141. An
inlet check valve 142 between the fluid reservoir 141 and delivery
chamber 122 can control the supply of delivery fluid to the
delivery chamber 122, while an outlet check valve 144 can control
the delivery of delivery fluid from the delivery chamber 122, such
as to a patient. A first pressure sensor 152 and a second pressure
sensor 154 can monitor the flow of fluid from the system. Further,
a flow restrictor 160 can be present in the pump 101 to produce a
pressure differential between sensors 152, 154 so as to provide a
mechanism for measuring the flow of the fluid. Mechanisms for
monitoring fluid flow are described further in U.S. Provisional
Patent Application No. 61/482,960, filed May 5, 2011, and titled
"SYSTEM AND METHOD OF DIFFERENTIAL PRESSURE CONTROL OF A
RCIPROCATING ELECTROKINETIC PUMP," and U.S. patent application Ser.
No. ______, filed herewith, and titled "SYSTEM AND METHOD OF
DIFFERENTIAL PRESSURE CONTROL OF A RCIPROCATING ELECTROKINETIC
PUMP."
[0030] In use, the electrokinetic assembly 100 works by producing
electrokinetic or electroostmostic flow. A voltage, such as a
positive voltage, is applied to the electrodes 108a, 108b, which
causes the engine fluid to move from the second chamber 104 to the
first chamber 102. The engine fluid may flow through or around the
electrodes 108a and 108b when moving between the chambers 104, 102.
The flow of fluid causes the movable member 110 to be pushed out of
the chamber 102 and the movable member 113 to be pulled into
chamber 104. As a result of the movement of the movable member 113,
delivery fluid is pulled from the reservoir 141 into the delivery
chamber 122. The movement of delivery fluid from the reservoir into
the delivery chamber 122 is called the "intake stroke" of the pump
cycle. When the opposite voltage is applied, such as a negative
voltage, fluid moves from the first chamber 102 to the second
chamber 104. The movement of engine fluid between chambers causes
the movable member 110 to be pulled into the first chamber 102 and
the movable member 113 to expand to compensate for the additional
volume of engine fluid in the second chamber 104. As a result,
delivery fluid in the chamber 122 is pushed out of the chamber 122
and delivered, such as to a patient, through the outlet check valve
144. The delivery of fluid is called the "outtake stroke" of the
pump cycle. Although the exemplary assemblies and systems described
below are configured such that a positive voltage corresponds to
the intake stroke and a negative voltage corresponds to an outtake
stroke, it is to be understood that the opposite configuration is
also possible--i.e., that a negative voltage corresponds to an
intake stroke and a positive voltage corresponds to an outtake
stroke. A controller can be used to control the voltage applied to
the electrodes 108a, 108b.
[0031] Referring to FIGS. 1 and 2A, a controller can be configured
to apply voltage to the EK assembly 100 in a pump cycle 261. Each
pump cycle 261 includes an intake stroke 263, a dwell phase 265, an
outtake stroke 267, and a wait phase 269. During the intake stroke
263, the controller applies a positive voltage to pull delivery
fluid from the fluid reservoir 141 into the pump 101. Likewise,
during the outtake stroke 267, a negative voltage is applied to
push delivery fluid out of the pump 101, e.g., to a patient. During
the dwell phase 265 and the wait phase 269, a zero voltage is
applied. The zero voltage phases are important to allow for the
delivery fluid to finish traveling through the pump 101 after the
voltage has stopped being applied and to control the overall flow
rate of the delivery fluid from the pump 101, i.e. to allow fluids
in the various chambers to settle and to allow the check valves to
fully close to prevent fluid back-flow into the pumping chamber. In
some embodiments, the controller can have a programmed delay 271
prior to the start-time 273 of the cycle of cycles 261. Referring
to FIGS. 2A and 2B, each pump cycle 261 will result in the delivery
of a single bolus 275 of fluid.
[0032] The electrokinetic pump assembly 100 can be configured to
stop pumping in a particular direction, i.e. with negative or
positive current, prior to the occurrence of a Faradaic process in
the liquid. Accordingly, the electrodes will advantageously not
generate gas or significantly alter the pH of the pump fluid. The
set-up and use of various EK pump assemblies are further described
in U.S. Pat. Nos. 7,235,164 and 7,517,440, the contents of which
are incorporated herein by reference.
[0033] Referring to FIG. 3, two or more EK pump assemblies 300a,
300b, 300c, 300d can be ganged, i.e., connected together, in a
single electrokinetic pump system 399 to deliver fluid from a
single reservoir 341. The pump assemblies 300a, 300b, 300c, 300d
can have their output lines connected at a fitting 383, such as a
T-fitting or trio of Y-fittings, so as to provide a single output
305. A controller 391 can be configured to control the cycles all
of the pump systems 300a, 300b, 300c, 300d such that the desired
flow profile is obtained from the EK pump system 399.
[0034] Referring to FIG. 4, two or more EK pump assemblies 400a
(having EK engine 403a and EK pump 401a), 400b (having EK engine
403b and EK pump 401b) can be connected together in parallel both
electrically and hydrodynamically to form a single EK pump system
499. A single controller 491 can be connected to both EK engines
403a, 403b to control delivery of fluid from a single reservoir
441. Because the sensors are connected in parallel, a single set of
pressure sensors 452, 454 and a single set of check valves 442, 444
can be used for the entire EK pump system 499.
[0035] In use, referring to FIGS. 4 and 5A, when the controller 491
applies a positive voltage, both pump assemblies 400a, 400b will
produce an intake stroke 563a, 563b, and when the controller 491
applies a negative voltage, both pump assemblies 400a, 400b will
produce an outtake stroke 567a, 567b. The EK pump system 499 will
experience a single dwell time 565 and a single wait time 569. As
shown in FIG. 5B, the individual boluses 575a, 575b associated with
each pump assembly 400a, 400b, respectfully, will occur at the same
time, thereby producing a single large bolus 575 of fluid for the
EK pump system 499.
[0036] Advantageously, by ganging pump assemblies in parallel as
described with reference to FIGS. 4 and 5, the flow rate of the EK
pump system can be increased without hindering manufacturability or
efficiency. Because the flow rate of a single EK assembly is
directly proportional to the area of the EK pump element, one
mechanism for increasing the flow rate is to increase the size of
the EK pump element. However, doing so can cause manufacturing
difficulties, such as producing a large porous dielectric material
and requiring production of a variety of sizes of EK engines.
Another mechanism for increasing the flow rate is to increase the
applied voltage. However, doing so can be inefficient because,
while the voltage is directly proportional to the flow rate,
increasing the voltage also increases the required current draw.
That is, because power is equal to voltages times the current,
increasing the voltage will increase the amount of power required
by a higher percentage than the flow rate is increased. For
example, if an engine produces a particular flow rate by drawing 30
mA of current at 3 volts (requiring a power of 90 mW), the flow
rate can be increased seven times by increasing the voltage to 21
volts. Correspondingly, the engine's current draw will increase
from 30 mA to 210 mA proportionally, and the required power will
increase to 4,410 mW. This method of increase flow rate is
inefficient because the pump system's power consumption has been
increased 49 times, while the flow rate has only been increased
seven times. Ganging EK assemblies together to increase the flow
rate avoids both of these problems while still allowing for an
increased flow rate. Moreover, ganging EK assemblies together in
parallel can advantageously provide a safety check; if one pump
assembly fails, the other pump assemblies can be used to
compensate.
[0037] Referring to FIG. 6, two or more EK pump assemblies 600a
(having EK engine 603a and EK pump 601a), 600b (having EK engine
603b and EK pump 601b) can be connected together in parallel
hydrodynamically but remain electrically independent to form EK
pump system 699. Each EK system 600a, 600b can include a separate
intake valve 642a, 642b, outtake valve 644a, 644b, first pressure
sensor 652a, 652b, and second pressure sensor 654a, 654b,
respectively. A single controller 691 can be connected to both EK
engines 603a, 603b to control delivery of fluid with the EK pump
system 699 from a single reservoir 641. The controller 691 can be
connected to a multiplexer or mechanical relay 693 to select which
pump to communicate with at a given time.
[0038] EK assembly 600a can have a different range of flow rates
than EK assembly 600b. For example, EK assembly 600b can be
configured to run at greater flow rates than EK assembly 600a.
Although FIG. 6 shows only two EK assemblies 600a, 600b connected
together, there can be more than two EK assemblies in a ganged EK
pump system. For example, a third EK system could be connected to
the first and second pumps and configured to run at a range of flow
rates different than the first or second ranges, such as a range
having rates that are higher than the first and second EK systems.
In some embodiments, at least one of the EK systems is configured
to pump fluid at approximately 0.01 to 5 mL/hr and at least one of
the EK systems is configured to pump fluid at approximately 0.1 to
15 mL/hr. In another embodiment, at least one of the EK systems is
configured to pump fluid at approximately 0.01 to 5 mL/hr and at
least on of the EK systems is configure to pump fluid at
approximately 1 to 300 mL/hr. In another embodiment, at least one
of the EK systems is configured to pump fluid at approximately 0.1
to 15 mL/hr and at least one of the EK systems is configured to
pump fluid at approximately 1 to 300 mL/hr.
[0039] In use, referring to FIGS. 6 and 7A, the controller 691 can
first apply a positive voltage to pump assembly 600a to produce an
intake stroke 763a and then a negative voltage to produce an
outtake stroke 767a. Subsequently, the controller 691 can switch
and apply a positive voltage to pump assembly 600b to produce an
intake stroke 763b and then a negative voltage to produce an
outtake stroke 767b. Optionally, the controller 691 can then switch
back to running EK pump system 600a. As shown in FIG. 7B, the bolus
775b produced by the second EK pump assembly 600b, designed to have
a higher flow rate than the first EK pump assembly 600a, will be
larger than the bolus 775a produced by the fist EK pump assembly
600a.
[0040] Advantageously, by ganging together pumps of different flow
rate ranges in the configuration shown in FIG. 6, a system having a
wide range of flow rates can be achieved. For example, the system
can be configured to have a range of flow rates from 0.0001 mL/hr
to 1200 mL/hr, such as 0.0001 mL/hr to 1,000 mL/hr, for example
0.01 mL/hr to 30 mL/hr. Having a wide range of flow rates can be
advantageous during various medical procedures, such as IV infusion
or insulin delivery. For example, during insulin delivery, basal
flow rates need to be very low, such as 0.1 ml/hr, while bolus
rates need to be very fast, such as 30 ml/hr.
[0041] Moreover, in some embodiments, the controller 691 can run
both EK assemblies 600a, 600b at the same time, thereby increasing
the total flow rate range achievable by the EK pump system 699. By
ganging EK assemblies of different sizes together in a single EK
pump system and running the pumps simultaneously, the accuracy of
the system can be increased relative to using a single EK assembly
having a large flow rate. That is, each EK pump system has an
optimal delivery volume where the EK engine is most efficient. For
example, a large delivery pump that has only a small percentage
error can still cause significant errors if being used to deliver
small volumes. Moreover, often the corresponding system components,
such as the sensors and check valves, can be dialed with a
resolution that matches the optimal volume to achieve better
accuracy. Further, timing errors caused by slow responsiveness of
larger components can be minimized by controlling smaller pumps to
move small amounts of liquid rather than using a large pump to
deliver small volumes of liquid. Accordingly, a ganged pumped
system having pumps of different volumes can advantageously provide
a more robust response range based upon the optimal ranges of the
pumps used.
[0042] Referring to FIG. 8, two or more EK pump assemblies 800a
(having EK engine 803a and EK pump 801a), 800b (having EK engine
803b and EK pump 801b) can be connected together hydrodynamically
in parallel with distributed control to form an EK pump system 899.
Thus, each EK assembly 800a, 800b can include a separate intake
valve 842a, 842b, outtake valve 844a, 844b, first pressure sensor
852a, 852b, and second pressure sensor 854a, 854b, respectively. A
single master controller 891 can be used for the EK pump system
899. The master controller 891 can be connected to a first slave
controller 895a for controlling delivery of fluid from the
reservoir 841 with the first EK assembly 800a and to a second slave
controller 895b for controlling delivery of fluid from the
reservoir 841 with the second EK assembly 800b.
[0043] The slave controllers 895a, 895b can, for example, perform
feedback measurements, control loop calculations, and current
controls. The master controller 891, in contrast, can be configured
to align the pump cycles of each of the assemblies 800a, 800b to
achieve the desired flow profile for the EK pump system 899.
Communication between the master controller 891 and slave
controllers 895a, 895b can include which slave is controlling
delivery at a particular time, what volume of fluid is delivered,
and any errors in delivery.
[0044] In use, referring to FIGS. 8, 9A, and 10A (four connected EK
systems are shown in the graphs of FIGS. 9A and 10A), the
controller 891 can be configured to synchronize the pump cycles of
each of the EK assemblies 800 to achieve substantially continuous
flow for the EK pump system 899.
[0045] In one embodiment, shown in FIG. 9A, the controller 891 can
be configured to stagger the start-times 973a, 973b, 973c, 973d
such that there is no overlap between any of the intake strokes
963a, 963b, 963c, 963d and so that there is no overlap between the
outtake strokes 967a, 967b, 967c, 967d. Thus, for example, the
cycle for the first pump assembly can start at time zero, the cycle
for the second pump assembly can start after a delay 971b, which
corresponds to the length of time of the intake stroke 963a, the
cycle for the third pump assembly can start after a delay 971c,
which corresponds to the length of time required for the intake
strokes 963a and 963b, and the cycle for the fourth pump assembly
can start after a delay 971d, which corresponds to the length of
time required for the intake strokes 963a, 963b, 963c. Accordingly,
as shown in FIG. 9B, there will be a series of boluses 975a, 975b,
975c, 975d strung closely together so as to achieve substantially
continuous flow of fluid, i.e. the instantaneous flow rate measured
at the distal end of the pump system proximate to where the pump
system is connected to the patient never drops to zero.
[0046] In another embodiment, shown in FIG. 10A, the controller 891
can be configured to stagger the start-times 1073a, 1073b, 1073c,
1073d such that there is overlap between at least some of the
intake strokes 1063a, 1063b, 1063c, 1063d and so that there is
overlap between at least some of the outtake strokes 1067a, 1067b,
1067c, 1067d. Thus, for example, as shown in FIG. 10A, the cycle
for the first pump assembly can start at time zero, the cycle for
the second pump assembly can start after a delay 1071b, which is
shorter than the length of time of the intake stroke 1063a, the
cycle for the third pump assembly can start after a delay 1071c,
which has a length of time shorter than the length of delay 1071b
plus the intake stroke 1063b, and the cycle for the fourth pump
assembly can start after a delay 1071d, which has a length of time
shorter than the length of delay 1071c plus the length of the
intake stroke 1063c. Accordingly, as shown in FIG. 10B, at least
some of the boluses 1075a, 1075b, 1075c, 1075d will overlap to
achieve substantially continuous flow.
[0047] In some embodiments, the controller 891 can run two or more
cycles concurrently so as to increase flow.
[0048] Advantageously, the system set-up of FIGS. 8, 9, and 10 can
provide substantially continuous flow of fluid from the fluid
reservoir. Substantially continuous flow can advantageously help
minimize the peak concentration level of delivery fluid, such as a
medication, given to a patient compared to a standard bolus or
injection. Minimizing peak concentration level can reduce the risk
of toxic effects associated with peak concentrations. Such a system
can be particularly advantageous for medications having a high
toxicity.
[0049] Further, by including overlapping boluses as described above
with respect to FIGS. 10A and 10B, the variation in the
instantaneous flow rate can advantageously be decreased. For
example, the instantaneous flow rate measured at the distal end of
the pump will never drop to zero and can be maintained within 20%
of the target flow rate, such as within 10% of the target flow
rate, for example within 5% of the target flow rate.
[0050] Referring to FIG. 11, two or more EK pump assemblies 1100a,
1100b can be connected together in EK pump system 1199. The system
1199 can have the same features as the system of FIG. 8 except that
each EK pump assembly 1100a, 1100b can include reciprocating
engines 1103a, 1103b. Accordingly, engine 1103a can power two pumps
1101a, 1101c, and engine 1103b can power two pumps 1101b, 1101d.
Further, each pump can have its own set of pressure sensors and
inlet/outlet valves.
[0051] Referring to FIGS. 11 and 12A, EK engine 1103a can produce
an intake stroke 1263a and an outtake stroke 1267c at the same
time. Further, EK engine 1103b can produce an intake stroke 1263b
and an outtake stroke 1267d at the same time. Accordingly, only one
delay 1271b is needed to synchronize the EK pump assemblies 1100a,
1100b, resulting in boluses 1275a, 1275b, 1275c, 1275d that produce
substantially continuous flow. Advantageously, reciprocating pumps
can be cheaper and easier to assemble, are more compact, and can
increase the efficiency of the system relative to single
engine--single pump systems. Moreover, although FIG. 12A shows only
non-overlapping intake and outtake strokes, the controller 1191 can
be configured to overlap the intake/outtake strokes so as to
achieve more continuous flow for the EK pump system 1199.
[0052] As for additional details pertinent to the present
invention, materials and manufacturing techniques may be employed
as within the level of those with skill in the relevant art. The
same may hold true with respect to method-based aspects of the
invention in terms of additional acts commonly or logically
employed. Also, it is contemplated that any optional feature of the
inventive variations described may be set forth and claimed
independently, or in combination with any one or more of the
features described herein. Likewise, reference to a singular item,
includes the possibility that there are plural of the same items
present. More specifically, as used herein and in the appended
claims, the singular forms "a," "and," "said," and "the" include
plural referents unless the context clearly dictates otherwise. It
is further noted that the claims may be drafted to exclude any
optional element. As such, this statement is intended to serve as
antecedent basis for use of such exclusive terminology as "solely,"
"only" and the like in connection with the recitation of claim
elements, or use of a "negative" limitation. Unless defined
otherwise herein, all technical and scientific terms used herein
have the same meaning as commonly understood by one of ordinary
skill in the art to which this invention belongs. The breadth of
the present invention is not to be limited by the subject
specification, but rather only by the plain meaning of the claim
terms employed.
* * * * *