U.S. patent application number 11/614364 was filed with the patent office on 2008-06-26 for infusion pump with a capacitive displacement position sensor.
This patent application is currently assigned to LifeScan, Inc.. Invention is credited to Sebastian Bohm.
Application Number | 20080152507 11/614364 |
Document ID | / |
Family ID | 39543055 |
Filed Date | 2008-06-26 |
United States Patent
Application |
20080152507 |
Kind Code |
A1 |
Bohm; Sebastian |
June 26, 2008 |
INFUSION PUMP WITH A CAPACITIVE DISPLACEMENT POSITION SENSOR
Abstract
Various methods and devices are provided for an electrokinetic
infusion pump. In one embodiment of the invention, the infusion
pump includes an infusion pump module, which can be configured to
dispense an insulin containing infusion liquid, and an
electrokinetic engine. The infusion pump module includes a
capacitive displacement position sensor configured for sensing a
dispensing state of the infusion pump module. The infusion pump
module can include an infusion module housing and the
electrokinetic engine can include a moveable partition. The
capacitive displacement sensor includes a first capacitive plate
disposed on the moveable partition and a second capacitive plate
disposed on the infusion module housing. The capacitive
displacement sensor is configured for measuring capacitance between
the first capacitive plate and the second capacitive plate and can
send a feedback signal to a closed loop controller that is
indicative of the capacitance between the first and second
capacitive plates.
Inventors: |
Bohm; Sebastian; (Los Gatos,
CA) |
Correspondence
Address: |
NUTTER MCCLENNEN & FISH LLP
WORLD TRADE CENTER WEST, 155 SEAPORT BOULEVARD
BOSTON
MA
02210-2604
US
|
Assignee: |
LifeScan, Inc.
Milpitas
CA
|
Family ID: |
39543055 |
Appl. No.: |
11/614364 |
Filed: |
December 21, 2006 |
Current U.S.
Class: |
417/44.1 ;
417/437; 604/67 |
Current CPC
Class: |
A61M 5/14526 20130101;
A61M 2205/3317 20130101; F04B 17/00 20130101; A61M 2205/3389
20130101; A61M 5/14244 20130101; A61M 5/172 20130101; A61M 5/14566
20130101; A61M 2005/14513 20130101; F04B 9/107 20130101; F04B
2201/0201 20130101 |
Class at
Publication: |
417/44.1 ;
417/437; 604/67 |
International
Class: |
F04B 49/06 20060101
F04B049/06 |
Claims
1. An electrokinetic infusion pump comprising: an infusion pump
module; and an electrokinetic engine, wherein the infusion pump
module includes a capacitive displacement position sensor
configured for sensing a dispensing state of the infusion pump
module.
2. The electrokinetic infusion pump of claim 1, wherein: the
infusion pump module includes an infusion module housing; the
electrokinetic engine includes a moveable partition; and the
capacitive displacement sensor includes a first capacitive plate
disposed on the moveable partition and a second capacitive plate
disposed on the infusion module housing.
3. The electrokinetic infusion pump of claim 2, wherein the first
capacitive plate and the second capacitive plate each have a width
of approximately 10 mm and a length of approximately 20 mm.
4. The electrokinetic infusion pump of claim 3, wherein a gap
between the first capacitive plate and the second capacitive plate
has a dimension in the range of approximately 10-1000
micrometer.
5. The electrokinetic infusion pump of claim 2, wherein the
capacitive displacement sensor is configured for measuring
capacitance between the first capacitive plate and the second
capacitive plate.
6. The electrokinetic infusion pump of claim 1, wherein the
electrokinetic engine includes a moveable partition and the
infusion pump includes an infusion housing, and wherein the
capacitive displacement sensor is a dual capacitive displacement
sensor that includes: a first capacitive plate and a second
capacitive plate disposed on the moveable partition; and a third
capacitive plate and a fourth capacitive plate disposed on the
infusion housing; wherein the first capacitive plate, the second
capacitive plate, the third capacitive plate and the fourth
capacitive plate are in operative electrical contact and wherein an
overlap between the second and fourth capacitive plate is constant
and an overlap between the first capacitive plate and the third
capacitive plate is dependent on a position of the moveable
partition.
7. The electrokinetic infusion pump of claim 1, wherein the
capacitive displacement sensor is configured to send a feedback
signal to a closed loop controller, the feedback signal indicative
of the capacitance between the first and second capacitive
plates.
8. The electrokinetic infusion pump of claim 1, wherein the
infusion pump is configured to dispense an insulin containing
infusion liquid.
9. An infusion pump system, comprising: an infusion pump that
includes: a capacitive displacement position sensor; and a closed
loop controller, wherein the infusion pump and closed loop
controller are in operative communication and configured such that
the closed loop controller can determine and control a dispensing
state of the infusion pump based on a feedback signal received from
the capacitive displacement position sensor.
10. The system of claim 9, wherein the infusion pump is an
electrokinetic pump.
11. The system of claim 10, wherein the electrokinetic infusion
pump further includes an infusion pump module; and an
electrokinetic engine, and wherein the capacitive displacement
sensor is configured for sensing a dispensing state of the infusion
pump module.
12. The system of claim 11, wherein: the infusion pump module
includes an infusion module housing; the electrokinetic engine
includes a moveable partition; and the capacitive displacement
sensor includes a first capacitive plate disposed on the moveable
partition and a second capacitive plate disposed on the infusion
module housing.
13. The system of claim 12, wherein the capacitive displacement
sensor is configured for sensing a dispensing state by measuring
capacitance between the first capacitive plate and the second
capacitive plate.
14. The system of claim 13, wherein the first capacitive plate and
the second capacitive plate each have a width of approximately 10
mm and a length of approximately 20 mm.
15. The system of claim 14, wherein a gap between the first
capacitive plate and the second capacitive plate has a dimension in
the range of approximately 10-1000 micrometer.
16. The system of claim 11, wherein the electrokinetic engine
includes a moveable partition and wherein the capacitive
displacement sensor is a dual capacitive displacement sensor that
includes: a first capacitive plate; a second capacitive plate; a
third capacitive plate; and a fourth capacitive plate, and wherein
the first capacitive plate, the second capacitive plate, the third
capacitive plate and the fourth capacitive plate are in operative
electrical contact and wherein an overlap between the second and
fourth capacitive plate is constant and an overlap between the
first capacitive plate and the third capacitive plate is dependent
on a position of the moveable partition.
17. The system of claim 11, wherein the electrokinetic engine
includes an electrokinetic supply reservoir that is at least
partially collapsible.
18. The system of claim 9, wherein the capacitive displacement
sensor is configured to send the feedback signal to the closed loop
controller.
19. The system of claim 9, wherein the infusion pump is configured
to dispense an insulin-containing infusion liquid.
20. A method for the closed loop control of an infusion pump,
comprising: sensing a dispensing state of an infusion pump with a
capacitive displacement position sensor; signaling the sensed
dispensing state of the infusion pump to a closed loop controller
via a feedback signal; determining, with the closed loop
controller, the dispensing state of the infusion pump based
feedback signal; and controlling the dispensing state of the
infusion pump with the closed loop controller by sending command
signals from the closed loop controller to an engine driving the
infusion pump.
Description
FIELD OF THE INVENTION
[0001] The present invention relates, in general, to a medical
devices and systems and, in particular, to infusion pumps, infusion
pump systems and associated methods.
BACKGROUND
[0002] Electrokinetic (EK) pumps provide for liquid displacement by
applying an electric potential across a porous dielectric media
that is filled with an ion-containing electrokinetic solution.
Properties of the porous dielectric media and ion-containing
solution (e.g., permittivity of the ion-containing solution and
zeta potential of the solid-liquid interface between the porous
dielectric media and the ion-containing solution) are predetermined
such that an electrical double-layer is formed at the solid-liquid
interface. Thereafter, ions of the electrokinetic solution within
the electrical double-layer migrate in response to the electric
potential, transporting the bulk electrokinetic solution with them
via viscous interaction. The resulting electrokinetic flow (also
known as electroosmotic flow) of the bulk electrokinetic solution
is employed to displace (i.e., "pump") a liquid. Further details
regarding electrokinetic pumps, including materials, designs, and
methods of manufacturing are included in U.S. patent application
Ser. No. 10/322,083 (United States Published Application No.
2004/0074784) filed on Dec. 17, 2002, which is hereby incorporated
in full by reference.
SUMMARY
[0003] The present invention provides various methods and devices
for an electrokinetic infusion pump. In one embodiment, the
electrokinetic infusion pump includes an infusion pump module,
which can be configured to dispense a medicament or another
treatment agent (e.g., an insulin containing infusion liquid), and
an electrokinetic engine. The infusion pump module includes a
capacitive displacement position sensor configured for sensing a
dispensing state of the infusion pump module. The infusion pump
module can include an infusion module housing and the
electrokinetic engine can include a moveable partition. The
capacitive displacement sensor includes a first capacitive element,
such as a capacitive plate, disposed on the moveable partition and
a second element, such as a capacitive plate, disposed on the
infusion module housing. The capacitive displacement sensor is
configured for measuring capacitance between the first capacitive
element and the second capacitive element and can send a feedback
signal to a closed loop controller that is indicative of the
capacitance between the first and second capacitive plates. In one
exemplary embodiment, the first capacitive plate and the second
capacitive plate each have a width of approximately 10 mm and a
length of approximately 20 mm. A gap between the first capacitive
plate and the second capacitive plate can have a dimension in the
range of approximately 10-1000 micrometers.
[0004] In another embodiment, the electrokinetic engine includes a
moveable partition and the infusion pump includes an infusion
housing, and the capacitive displacement sensor is a dual
capacitive displacement sensor. The dual capacitive displacement
sensor includes a first capacitive plate and a second capacitive
plate disposed on the moveable partition and a third capacitive
plate and a fourth capacitive plate disposed on the infusion
housing. The first, second, third, and fourth capacitive plates are
in operative electrical contact. An overlap between the second and
fourth capacitive plate is constant and an overlap between the
first capacitive plate and the third capacitive plate is dependent
on a position of the moveable partition.
[0005] In another exemplary embodiment, an infusion pump system is
provided that includes an infusion pump, for example, an
electrokinetic pump, having a capacitive displacement position
sensor and a closed loop controller. The infusion pump and closed
loop controller are in operative communication and configured such
that the closed loop controller can determine and control a
dispensing state of the infusion pump based on a feedback signal
received from the capacitive displacement position sensor. The
infusion pump further includes an infusion pump module and an
electrokinetic engine. The capacitive displacement sensor is
configured for sensing a dispensing state of the infusion pump
module. The infusion pump can be configured to dispense, for
example, an insulin-containing infusion liquid.
[0006] The infusion pump module can include an infusion module
housing and the electrokinetic engine can include a moveable
partition. The electrokinetic engine can also include an
electrokinetic supply reservoir that is at least partially
collapsible. The capacitive displacement sensor can include a first
capacitive plate disposed on the moveable partition and a second
capacitive plate disposed on the infusion module housing, and the
capacitive displacement sensor can be configured for sensing a
dispensing state by measuring capacitance between the first
capacitive plate and the second capacitive plate. In one
embodiment, the first capacitive plate and the second capacitive
plate each have a width of approximately 10 mm and a length of
approximately 20 mm, and a gap between the first capacitive plate
and the second capacitive plate has a dimension in the range of
approximately 10-1000 micrometer.
[0007] In one embodiment, the electrokinetic engine includes a
moveable partition and the capacitive displacement sensor is a dual
capacitive displacement sensor that includes first, second, third,
and fourth capacitive plates. The first, second, third, and fourth
capacitive plates are in operative electrical contact and an
overlap between the second and fourth capacitive plate is constant
and an overlap between the first capacitive plate and the third
capacitive plate is dependent on a position of the moveable
partition.
[0008] Methods for the closed loop control of an infusion pump are
also provided, and in one embodiment the method can include sensing
a dispensing state of an infusion pump, for example, an
electrokinetic infusion pump, with a capacitive displacement
position sensor and signaling the sensed dispensing state of the
infusion pump to a closed loop controller via a feedback signal.
The closed loop controller determines the dispensing state of the
infusion pump based feedback signal and controls the dispensing
state of the infusion pump by sending command signals from the
closed loop controller to an engine driving the infusion pump.
These steps can be repeated to maintain control of the
electrokinetic infusion pump.
[0009] Sensing the dispensing state can include sensing a position
of a moveable partition of the electrokinetic infusion pump by the
capacitive displacement sensor. Sensing the dispensing state can
also include sensing the position of the moveable partition due to
a change in overlap between capacitive plates of the capacitive
displacement sensor. The dispensing state can be an infusion liquid
displacement rate or an infusion liquid volume. The step of
controlling the dispensing state can include controlling the
dispensing state of an insulin containing infusion liquid. The
capacitive displacement position sensor can be a dual capacitive
displacement sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention will be more fully understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0011] FIG. 1 is an exploded schematic illustration of an
electrokinetic infusion pump system with closed loop control
according to an exemplary embodiment of the present invention in a
first dispense state;
[0012] FIG. 2 is an exploded schematic illustration of the
electrokinetic infusion pump system shown in FIG. 1 in a second
dispense state;
[0013] FIG. 3 is a perspective illustration of an electrokinetic
infusion pump system according to another exemplary embodiment of
the present invention being manually manipulated;
[0014] FIG. 4 is a cross-sectional depiction of an electrokinetic
infusion pump system according to a further exemplary embodiment of
the present invention in a first dispense state;
[0015] FIG. 5 is a cross-sectional depiction of the electrokinetic
infusion pump system shown in FIG. 4 in a second dispense
state;
[0016] FIG. 6 is a perspective depiction of a portion of the
electrokinetic infusion pump of the EK infusion pump system shown
in FIG. 4;
[0017] FIG. 7 is a perspective depiction of a portion of the
electrokinetic infusion pump of the EK infusion pump system shown
in FIG. 5;
[0018] FIG. 8 is a perspective depiction of a portion of an
electrokinetic infusion pump with capacitive displacement position
sensors according to another exemplary embodiment of the present
invention in a first dispense state;
[0019] FIG. 9 is a perspective depiction of the portion of an
electrokinetic infusion pump shown in FIG. 8 in a second dispense
state;
[0020] FIG. 10 is a schematic drawing depicting a capacitive plate
configuration of the electrokinetic infusion pump shown in FIG.
8;
[0021] FIG. 11 is a schematic drawing depicting a capacitive plate
configuration of the electrokinetic infusion pump shown in FIG.
9;
[0022] FIG. 12 is an electrical circuit schematic depicting the
analog electric circuit formed by the capacitive displacement
position sensor shown in FIGS. 8-11; and
[0023] FIG. 13 is a flow diagram illustrating a method for the
closed loop control of an electrokinetic infusion pump according to
an exemplary embodiment of the present invention.
DETAILED DESCRIPTION
[0024] Certain exemplary embodiments will now be described to
provide an overall understanding of the principles of the
structure, function, manufacture, and use of the devices and
methods disclosed herein. One or more examples of these embodiments
are illustrated in the accompanying drawings. Those skilled in the
art will understand that the devices and methods specifically
described herein and illustrated in the accompanying drawings are
non-limiting exemplary embodiments and that the scope of the
present invention is defined solely by the claims. The features
illustrated or described in connection with one exemplary
embodiment may be combined with the features of other embodiments.
Such modifications and variations are intended to be included
within the scope of the present invention.
[0025] Various exemplary methods and devices are provided for
controlling the dispensing state of an infusion pump system. In
particular, the methods and devices provide a capacitive
displacement position sensor coupled with an infusion pump to
control the dispensing of an infusion liquid from the infusion
pump.
[0026] FIGS. 1-2 are exploded schematic illustrations of an
electrokinetic (EK) infusion pump system 100 with closed loop
control according to an exemplary embodiment of the present
invention. FIG. 1. illustrates the EK infusion pump system 100 in a
first dispense state, while FIG. 2 depicts the EK infusion pump
system 100 in a second dispense state.
[0027] Referring to FIGS. 1 and 2, the EK infusion pump system 100
includes an electrokinetic (EK) infusion pump 102 and a closed loop
controller 104. The EK infusion pump 102 can include a capacitive
displacement position sensor (not shown in FIGS. 1 and 2). As is
described in further detail below, the EK infusion pump 102 and the
closed loop controller 104 are in operative communication such that
the closed loop controller 104 can determine and control the
dispensing state of the EK infusion pump 102 based on one or more
feedback signals FB from the capacitive displacement position
sensor. The EK infusion pump 102 and the closed loop controller 104
can be configured in a variety of ways. For example, the infusion
pump 102 and the closed loop controller 104 can be entirely
separate units, partially integrated (for example, predetermined
components of the EK infusion pump 102 can be integrated within the
closed loop controller 104), or a single integrated unit.
[0028] The EK infusion pump systems according to embodiments of the
present invention, including the EK infusion pump system 100, can
be employed to deliver a variety of medically useful infusion
liquids such as, for example, insulin for diabetes; morphine and
other analgesics for pain; barbiturates and ketamine for
anesthesia; anti-infective and antiviral therapies for Acquired
Immune Deficiency Syndrome (AIDS); antibiotic therapies for
preventing infection; bone marrow for immunodeficiency disorders,
blood-borne malignancies, and solid tumors; chemotherapy for
cancer; dobutamine for congestive heart failure; monoclonal
antibodies and vaccines for cancer, brain natriuretic peptide for
congestive heart failure, and vascular endothelial growth factor
for preeclampsia. The delivery of such infusion liquids can be
accomplished via any suitable route including subcutaneously,
intravenously or intraspinally.
[0029] The EK infusion pump 102 can also include an electrokinetic
(EK) engine 106 and an infusion module 108. The EK engine 106 can
include an electrokinetic (EK) supply reservoir 110, an
electrokinetic (EK) porous media 112, an electrokinetic (EK)
solution receiving chamber 114, a first electrode 116, a second
electrode 118, and an electrokinetic (EK) solution 120 (depicted as
upwardly pointing chevrons).
[0030] The pore size of the porous media 112 can be, for example,
in the range of 100 nm to 200 nm. A person skilled in the art will
appreciate that the porous media 112 can have any number of pores
with any pore size that allows the appropriate amount of
electrokinetic solution 120 to flow through it. Moreover, the
porous media 112 can be formed of any suitable material including,
by way of non-limiting example, Durapore Z PVDF membrane material
available from Millipore, Inc. USA. EK solution 120 can be any
suitable EK solution including, but not limited to, 10 mM TRIS/HCl
at a neutral pH.
[0031] The infusion module 108 can include the EK solution
receiving chamber 114 (which is also considered part of the EK
engine 106), an infusion module housing 122, a movable partition
124, an infusion reservoir 126, an infusion reservoir outlet 128,
and an infusion liquid 130 (depicted as dotted shading). Although
the capacitive displacement position sensor of the infusion module
108 is not depicted in FIGS. 1 and 2, the feedback signal FB
between the capacitive displacement position sensor and the closed
loop controller 104 is shown.
[0032] The closed loop controller 104 can include a voltage source
132 and is configured to receive the feedback signal FB from the
capacitive displacement sensor and to be in electrical
communication with the first and second electrodes 116 and 118. The
EK engine 106, the infusion module 108, and the closed loop
controller 104 can be integrated into a single assembly, into
multiple assemblies, or can be separate units.
[0033] During operation of the EK infusion pump system 100, the EK
engine 106 provides the driving force for displacing (pumping) the
infusion liquid 130 from the infusion module 108. To do so, a
voltage difference is established across the EK porous media 112 by
the application of an electrical potential between the first
electrode 116 and the second electrode 118. This electrical
potential results in an electrokinetic pumping of the EK solution
120 from the EK supply reservoir 110, through the EK porous media
112, and into the EK solution receiving chamber 114.
[0034] As the electrokinetic solution receiving chamber 114
receives the EK solution 120, the moveable partition 124 is forced
to move in the direction of arrows .mu.l, shown in FIGS. 1-2. Such
movement is evident by a comparison of the first dispense state
shown in FIG. 1 to the second dispense state shown in FIG. 2. As
the moveable partition 124 moves in the direction of .mu.l, the
infusion liquid 130 is displaced (i.e., "pumped") out of the
infusion reservoir 126 and through the infusion reservoir outlet
128 in the direction of arrow .mu.l. The EK engine 106 can continue
to displace the EK solution 120 until the moveable partition 124
reaches a predetermined point near the infusion reservoir outlet
128, for example, a point just proximal of the infusion reservoir
outlet 128, thereby displacing a predetermined amount (e.g.,
essentially all) of the infusion liquid 130 from the infusion
reservoir 126.
[0035] It is evident from the description above and a comparison of
FIGS. 1 and 2, that the second dispensing state represented by FIG.
2 is achieved by electrokinetically displacing (i.e., pumping or
dispelling) a portion of the infusion liquid 130 that is present
within the infusion reservoir 126 in the first dispensing state
represented by FIG. 1.
[0036] The rate of displacement of the infusion liquid 130 from the
infusion reservoir 126 is directly proportional to the rate at
which the EK solution 120 is pumped from the EK supply reservoir
110 into the EK solution receiving chamber 114. The proportionality
between the rate of displacement of the infusion liquid 130 (such
as an insulin containing infusion liquid) and the rate at which the
EK solution 120 is pumped can be, for example, in the range of 1:1
to 4:1. Furthermore, the rate at which the EK solution 120 is
pumped from the EK supply reservoir 110 is a function of the
voltage and current applied by the first electrode 116 and the
second electrode 118 and various electro-physical properties of the
EK porous media 112 and the EK solution 120 (such as, for example,
zeta potential, permittivity of the EK solution and viscosity of
the EK solution).
[0037] The features disclosed herein are applicable to a variety of
electrokinetic infusion pump systems, including, for example, the
electrokinetic infusion pumps and electrokinetic infusion pump
systems of the type disclosed in U.S. patent application Ser. No.
11/532,587, filed Sep. 18, 2006, entitled "Electrokinetic Infusion
Pump System," which is incorporated herein in its entirety. In
addition, features disclosed herein can be used in combination with
electrokinetic infusion pump systems of the type disclosed in U.S.
patent application Ser. No. 11/532,587, as well as with features of
electrokinetic infusion pumps as disclosed in U.S. patent
application Ser. No. 11/532,691, filed Sep. 18, 2006, entitled
"Malfunction Detection With Derivative Calculation," and U.S.
patent application Ser. No. 11/614,211, filed Dec. 21, 2006,
entitled "Malfunction Detection In Infusion Pumps," both of which
are likewise incorporated herein in their entirety.
[0038] Further details regarding EK engines, including materials,
designs, operation and methods of manufacturing, are included in
U.S. patent application Ser. No. 10/322,083 (United States
Published Application No. 2004/0074784) filed on Dec. 17, 2002,
which has been incorporated by reference. Although a particular EK
engine is depicted in a simplified manner in FIGS. 1 and 2, any
suitable EK engine can be employed in embodiments of the present
invention including, but not limited to, the EK engines described
in the aforementioned U.S. patent application Ser. No. 10/322,083
and EK engines that substitute a media with a microchannel(s) for
the aforementioned porous media.
[0039] The capacitive displacement position sensor of EK infusion
pump 102 is configured to sense (determine) the position of the
moveable partition 124. Based on the sensed position of the
moveable partition 124 (as communicated by feedback signal FB), the
closed loop controller 104 can determine the dispensing state
(e.g., the displacement position of the moveable partition 124 at
any given time and/or as a function of time, the rate of
displacement of the infusion liquid 130 from infusion reservoir
126, the rate at which the EK solution 120 is pumped from the EK
supply reservoir 110 to the EK solution receiving chamber 114, and
the volume of dispensed EK solution).
[0040] Based on such a determination of dispensing state, the
closed loop controller 104 controls (i.e., can command and manage)
the dispensing state by, for example, (i) adjusting the voltage
and/or current applied between the first electrode 116 and the
second electrode 118 or (ii) maintaining the voltage between the
first electrode 116 and the second electrode 118 constant while
adjusting the duration during which power is applied between the
first electrode 116 and the second electrode 118. For example, by
adjusting the voltage and/or current applied across the first
electrode 116 and the second electrode 118, the rate at which the
EK solution 120 is displaced from the EK supply reservoir 110 to
the EK solution receiving chamber 114 and, therefore, the rate at
which the infusion liquid 130 is displaced through the infusion
reservoir outlet 128, can be accurately and beneficially
controlled.
[0041] The closed loop control of EK infusion pumps described above
beneficially compensates for variations that may cause inconsistent
displacement (i.e., dispensing) of the infusion liquid 130
including, but not limited to, variations in temperature,
downstream resistance, and mechanical friction.
[0042] The EK supply reservoir 110 can have a variety of
configurations. In one embodiment, the EK supply reservoir 110 can
be partially or wholly collapsible. For example, the EK supply
reservoir 110 can be configured as a collapsible sack. Such
collapsibility provides for the volume of the EK supply reservoir
110 to decrease as the EK solution 120 is displaced therefrom. Such
a collapsible EK supply reservoir 110 can also assist in the
prevention of undesirable bubble formation within the EK supply
reservoir 110.
[0043] The infusion module housing 122 can also be configured in a
variety of additional ways, and can be, for example, at least
partially rigid to facilitate the movement of the moveable
partition 124 and the reception of the EK solution 120 pumped from
the EK supply reservoir 110.
[0044] The moveable partition 124 can be configured to prevent
migration of the EK solution 120 into the infusion liquid 130,
while minimizing resistance to its own movement (displacement) as
the EK solution receiving chamber 114 receives the EK solution 120
pumped from the EK supply reservoir 110. The moveable partition 124
can, for example, include elastomeric seals that provide intimate,
yet movable, contact between the moveable partition 124 and the
infusion module housing 122. The moveable partition 124 can have a
variety of configurations, such as, for example, a piston-like
configuration, or the moveable partition 124 can be configured as a
moveable membrane and/or bellows.
[0045] FIG. 3 is a perspective illustration of an electrokinetic
(EK) infusion pump system 200 according to another exemplary
embodiment of the present invention being manipulated by a user's
hands (H). The EK infusion pump system 200 can include an
electrokinetic (EK) infusion pump 202 and a closed loop controller
204.
[0046] The EK infusion pump 202 and the closed loop controller 204
can be handheld, and/or mounted to a user by way of clips,
adhesives or non-adhesive removable fasteners. For example, the EK
infusion pump system 200 can be configured to be worn on a user's
belt, thereby providing an ambulatory EK infusion pump system. In
addition, the closed loop controller 204 can be directly or
wirelessly connected to a remote controller or other auxiliary
equipment (not shown in FIG. 3) that provide analyte monitoring
capabilities and/or additional data processing capabilities.
[0047] The EK infusion pump 202 and the closed loop controller 204
can include components that are essentially equivalent to those
described above with respect to the EK infusion pump 102 and the
closed loop controller 104. In addition, the closed loop controller
204 can include a variety of features, including a display 240,
input keys 242a and 242b, and an insertion port 244.
[0048] The display 240 can be configured, for example, to display a
variety of information, including infusion rates, error messages
and logbook information. During use of the EK infusion pump system
200, and subsequent to the EK infusion pump 202 having been filled
with infusion liquid, the EK infusion pump 202 can be inserted into
the insertion port 244. Upon such insertion, operative electrical
communication is established between the closed loop controller 204
and the EK infusion pump 202. Such electrical communication
includes the ability for the closed loop controller 204 to receive
a feedback signal FB from a capacitive displacement position sensor
of the EK infusion pump 202 and operative electrical contact with
first and second electrodes of the EK infusion pump 202.
[0049] One skilled in the art will recognize that an infusion set
(not shown but typically including, for example, a connector,
tubing, needle and/or cannula and an adhesive patch) can be
connected to the infusion reservoir outlet of the EK infusion pump
202 and, thereafter, primed. As may be suitable for a particular
infusion set, such attachment and priming can occur before or after
EK infusion pump 202 is inserted into insertion port 244. After
determining the position of a movable partition of EK infusion pump
202, voltage and current are applied across the EK porous media of
EK infusion pump 202, thereby dispensing (pumping) infusion
liquid.
[0050] FIG. 4 is a cross-sectional depiction of an electrokinetic
(EK) infusion pump system 300 according to a further exemplary
embodiment of the present invention in a first dispense state,
while FIG. 5 depicts the EK infusion pump system 300 in second
dispense state. FIG. 6 is a further perspective depiction of a
portion of the EK infusion pump system 300 in the first dispense
state of FIG. 4, while FIG. 7 is in the second dispense state of
FIG. 5. As will be evident from the discussion below, the focus of
FIGS. 6 and 7 is the capacitive displacement position sensor of the
EK infusion pump system 300. Therefore, FIGS. 6 and 7 are further
simplified versions of FIGS. 4 and 5 that serve to highlight the
capacitive displacement position sensor.
[0051] Referring to FIGS. 4-7, the EK infusion pump system 300
includes an electrokinetic (EK) infusion pump 302 and a closed loop
controller 304. As will be clear to one skilled in the art from the
following description, the EK infusion pump 302 includes an
integrated electrokinetic (EK) engine and infusion module
(collectively element 306) and a capacitive displacement position
sensor 307.
[0052] The integrated EK engine and infusion module 306 includes an
electrokinetic (EK) supply reservoir 310, an electrokinetic (EK)
porous media 312, an electrokinetic (EK) solution receiving chamber
314, a first electrode 316, a second electrode 318, and an
electrokinetic (EK) solution 320 (depicted as upwardly pointing
chevrons). The integrated EK engine and infusion module 306 also
includes an infusion module housing 322, a movable partition 324,
an infusion reservoir 326, an infusion reservoir outlet 328, and an
infusion liquid 330 (depicted as dotted shading).
[0053] The moveable partition 324 can have a variety of
configurations, but in the illustrated embodiment can include a
first infusion seal 348, a spacer 349, and a second infusion seal
350. The spacer 349 is positioned between the first and second
infusion seals 348, 350, with the first infusion seal positioned
proximal of the spacer 349 and the second infusion seal 350
positioned distal of the spacer 349. The spacer 349 of the moveable
partition 324 is at a position B in the first dispense state a
shown in FIG. 4, and is at a position C in the second dispense
state as shown in FIG. 5. The distance between position B and
position C is labeled D in FIG. 5.
[0054] In an exemplary embodiment, the capacitive displacement
position sensor 307 includes a first capacitive element 352, such
as a capacitive plate, a second capacitive element 354, such as a
capacitive plate, a first electrical contact 356, a second
electrical contact 358, and a capacitance measurement module
360.
[0055] The first capacitive plate 352 is mounted on the movable
partition 324, and moves parallel to the longitudinal axis of the
infusion module housing 322 along with the movable partition 324.
The second capacitive plate 354 remains stationary and is mounted
on the infusion module housing 322 such that there is a gap G (also
referred to as a separation) between the first capacitive plate 352
and the second capacitive plate 354. The gap G can be filled with
any suitable material including, for example, air, a wall of the
infusion module housing 322 (which is formed of plastic or other
suitable electrically insulating material), other suitable
electrically insulating material, and combinations thereof.
[0056] The first electrical contact 356 provides electrical contact
between the first capacitive plate 352 and the capacitance
measurement module 360, while second electrical contact 358
provides electrical contact between second capacitive plate 354 and
capacitance measurement module 360. In the first dispense state
depicted in FIGS. 4 and 6, the moveable partition 324 is in a first
position, and the first capacitive plate 352 partially overlaps the
second capacitive plate 354. The capacitance measurement module 360
is configured to provide a feedback signal FB to the closed loop
controller 304 which is indicative of the capacitance between the
first and second capacitive plates 352, 354. As the moveable
partition 324 and the first capacitive plate 354 move and the
capacitance between the first and second capacitive plates 352, 354
changes, the closed loop controller 304 uses the feedback signal FB
to control the dispense state, as will be described in more detail
below.
[0057] As the capacitance between two capacitive plates is
proportional to their overlapping area divided by the distance
between the plates, a measured capacitance between the first
capacitive plate 352 and the second capacitive plate 354 can be
readily correlated to the extent of their overlap. Since the first
capacitive plate 352 is attached to the moveable partition 324, the
extent of overlap and/or any change in overlap can be employed to
determine the position (i.e., displacement position) of the
moveable partition 324. For example, in FIGS. 5 and 7, the moveable
partition 324 has moved relative to its position in FIGS. 4 and 6,
and the overlap between the first capacitive plate 352 and the
second capacitive plate 354 has increased. This increase in overlap
will result in an increase in the capacitance that is measured by
the capacitance measurement module 360.
[0058] The position of the movable partition 324 can then be
readily derived from the change in capacitance between the two
capacitive plates 352, 354 since the measured capacitance C is
proportional to A/G where A is the area of plate overlap and G is
the gap dimension. In this regard, the first and second capacitive
plates 352, 354 have typical dimensions, for example, of 10 mm
(width) by 20 mm (length). The area of overlap between the first
and second capacitive plates 352, 354 can vary depending on the
placement of the first and second capacitive plates 352, 354 on the
moveable partition 324 and the infusion module housing 322. For
example, the largest overlap between the first and second
capacitive plates 352, 354 can be a substantially complete overlap
of the first and second capacitive plates 352, 354, and the
smallest overlap between the first and second capacitive plates
352, 354 has typical dimensions, for example, of 10 mm (in width)
by 5 mm (in length). In addition, the gap dimension G can have a
range between 10 and 1000 micrometers, and, for example, it can be
0.5 mm.
[0059] In the embodiments shown in FIGS. 4-7, both the first and
second capacitive plates 352, 354 are in direct electrical
connection with the capacitance measurement module 360. However,
providing a direct electrical connection to the first capacitive
plate 352 can raise the cost and complexity of manufacturing. FIG.
8 is a perspective depiction of a portion of an electrokinetic (EK)
infusion pump 400 according to another embodiment of the present
invention in a first dispense state. As is explained in more detail
below, the EK infusion pump 400 employs a dual capacitive coupling
configuration to address the issue of manufacturing cost and
complexity. FIG. 9 is a perspective depiction of the portion of the
EK infusion pump 400 in a second dispense state. FIGS. 8 and 9 are
simplified in a similar manner to the simplified depictions of
FIGS. 6 and 7.
[0060] FIG. 10 is a schematic drawing depicting a capacitive plate
configuration 500 of the first dispense state of FIG. 8, while FIG.
11 is a schematic drawing depicting a capacitive plate
configuration 600 of the second dispense state of FIG. 9.
[0061] Referring to FIGS. 8-11, the EK infusion pump 400 includes
an integrated electrokinetic (EK) engine and infusion module 406,
and a dual capacitive displacement sensor 407. The integrated EK
engine and infusion module 406 includes an infusion module housing
422 and a moveable partition 424.
[0062] The dual capacitive displacement sensor 407 includes a first
capacitive plate 482, a second capacitive plate 484 (configured as
an extension of first capacitive plate 482), a third capacitive
plate 486, a fourth capacitive plate 488, a first electrical
contact 490, and a second electrical contact 492.
[0063] The first and second capacitive plates 482, 484 are mounted
on the movable partition 424, and move parallel to the longitudinal
axis of the infusion module housing 422 together with the movable
partition 424 (for example, in the direction of arrow A6 as shown
in FIG. 11). The third and fourth capacitive plates 486, 488 are
mounted on the infusion module housing 422 such that there is a gap
between the first capacitive plate 482 and the third capacitive
plate 486, as well as a gap between the second capacitive plate 484
and the fourth capacitive plate 488. The gaps can be filled with
any suitable material including, for example, air, a wall of the
infusion module housing 422 (which is formed of plastic or other
suitable electrically insulating material), other suitable
electrically insulating material, and combinations thereof.
[0064] The first electrical contact 490 provides electrical contact
between the fourth capacitive plate 488 and the capacitance
measurement module 460, while the second electrical contact 492
provides electrical contact between the third capacitive plate 486
and the capacitance measurement module 460.
[0065] The extent of overlap between the first capacitive plate 482
and the third capacitive plate 486 is variable as the moveable
partition 424 moves, as evidenced by a comparison of FIGS. 8 and 9
or FIGS. 10 and 11. However, the extent of overlap between the
second capacitive plate 484 and the fourth capacitive plate 488 is
constant as moveable partition 424 moves, as evidenced by a
comparison of FIGS. 8 and 9 or FIGS. 10 and 11. The position of the
movable partition 424 can then be derived from a change in
capacitance as measured by the capacitance measurement module 460.
The position of the moveable partition 424 can be readily derived
since the total measured capacitance is the result of two
capacitances in series, of which one is constant and one is
variable with moveable partition position. In other words,
1/C.sub.tot is equal to the sum of 1/C.sub.c and 1/C.sub.v (where
C.sub.tot is the measured total capacitance, C.sub.c is the
constant capacitance between the second and fourth capacitive
plates 484, 488 and C.sub.v is the variable capacitance between
first and third capacitive plates 482, 486).
[0066] FIG. 12 is an electrical circuit schematic depicting an
electric circuit 700 that is essentially equivalent to the circuit
formed by the capacitive plates depicted in FIGS. 8-11. As depicted
in FIG. 12, the circuit includes one variable capacitor that
includes the first and third capacitive plates (i.e., capacitive
plates 482 and 486) and one fixed capacitor that includes the
second and third capacitive plates (i.e., capacitive plates 484 and
488).
[0067] FIG. 13 is a flow diagram illustrating a method 800 for the
closed loop control of an electrokinetic (EK) infusion pump
according to an exemplary embodiment of the present invention. The
method 800 includes, at step 810, sensing a dispensing state of an
EK infusion pump with a capacitive displacement position sensor.
The capacitive displacement position sensor and the EK infusion
pump can be any such sensor and EK infusion pump as described
herein with respect to embodiments of the present invention.
[0068] Subsequently, the sensed dispensing state of the EK infusion
pump is signaled to a closed loop controller via a feedback signal,
as set forth in step 820. The closed loop controller then
determines the dispensing state of the electrokinetic infusion pump
based on the feedback signal, as set forth in step 830.
[0069] Subsequently, at step 840, the dispensing state of the EK
infusion pump (e.g., infusion liquid displacement rate) is
controlled by the closed loop controller by the sending command
signals from the closed loop controller to an electrokinetic engine
of the EK infusion pump. The command signal can be, for example,
based on a comparison of the determined dispensing state and a
predetermined desired dispensing state and be a command signal that
adjusts for any differences between the determined dispensing state
and the predetermined desired dispensing state.
[0070] The method 800 can be practiced using EK infusion pump
systems according to the present invention including the
embodiments of FIGS. 1-12. Moreover, steps 810 through 840 can be
repeated as necessary to establish and maintain accurate control of
the EK infusion pump dispensing state.
[0071] EK infusion pumps and EK infusion pump systems according to
embodiments of the present invention are economical to manufacture
since the capacitive plates of their capacitive displacement
position sensors can be formed using conventional economical
techniques such as laser ablation of thin metal layers, screen
printing and offset printing. Moreover, since the plates can be
manufactured economically, the capacitive displacement position
sensors described herein can be included as a component within a
disposable EK infusion pump.
[0072] In addition, capacitance can be measured using techniques
with beneficially low power consumption, thus enabling EK infusion
pumps and EK infusion systems with extended lifetimes. For example,
capacitance-to-digital converter device AD7745 (commercially
available from Analog Devices Inc., U.S.A.) can directly measure
capacitance and convert the measured capacitance to a digital
signal at an indicated power consumption of approximately 1 mW.
[0073] It should be understood that various alternatives to the
embodiments of the invention described herein may be employed in
practicing the invention. It is intended that the following claims
define the scope of the invention and that methods within the scope
of these claims and their equivalents be covered thereby
[0074] One skilled in the art will appreciate further features and
advantages of the invention based on the above-described
embodiments. Accordingly, the invention is not to be limited by
what has been particularly shown and described, except as indicated
by the appended claims. All publications and references cited
herein are expressly incorporated herein by reference in their
entirety.
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