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Infusion pump with a capacitive displacement position sensor

Infusion pump with a capacitive displacement position sensor description/claims

The present invention relates, in general, to a medical devices and systems and, in particular, to infusion pumps, infusion pump systems and associated methods.

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.

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.

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.

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.

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.

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.

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.

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.

The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

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;

FIG. 2 is an exploded schematic illustration of the electrokinetic infusion pump system shown in FIG. 1 in a second dispense state;

FIG. 3 is a perspective illustration of an electrokinetic infusion pump system according to another exemplary embodiment of the present invention being manually manipulated;

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;

FIG. 5 is a cross-sectional depiction of the electrokinetic infusion pump system shown in FIG. 4 in a second dispense state;

FIG. 6 is a perspective depiction of a portion of the electrokinetic infusion pump of the EK infusion pump system shown in FIG. 4;

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