Device and Method Employing Shape Memory Alloy
First Claim
1. A medical device for pumping a fluid, comprising:
- an inner tubular member coaxially aligned within an outer cylindrical shell, the inner tubular member defining a cavity and configured for axial movement relative to the outer shell;
a shape memory alloy wire having a shorter remembered shape associated with the inner tubular member to impart axial movement thereto;
a digital timing circuit for activating the shape memory alloy wire including a capacitor for providing electrical energy to the shape memory alloy wire to thermally transform the wire to the shorter remembered shape;
a biasing member biasing the inner tubular member away from the outer cylindrical shell increasing a size of the cavity;
a reservoir containing a fluid and being in fluid communication with the cavity; and
wherein as the shape memory alloy wire shortens and imparts axial movement to the inner tubular member, the size of the cavity is reduced thereby forcing fluid out of the cavity via an outlet, and as the biasing member restores the size of the cavity causing a vacuum therein, fluid is pulled from the reservoir into the cavity via an inlet.
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Abstract
A system for the metering and delivery of small discrete volumes of liquid is comprised of a small or minimal number of inexpensive components. One such component is a movable member, such as a miniature precision reciprocating displacement pump head, which is driven by an actuator that comprises a shape memory alloy material. The operating mechanism of the system is of little or minimal complexity. The system facilitates the precise metering and delivery of the small discrete volumes of liquid. Potential applications for the system include subcutaneous, long-term, automated drug delivery, for example, the delivery of insulin to a person with diabetes. In such an application, the small, simple and inexpensive nature of the invention would allow for its use as both a portable and a disposable system.
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Citations
33 Claims
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1. A medical device for pumping a fluid, comprising:
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an inner tubular member coaxially aligned within an outer cylindrical shell, the inner tubular member defining a cavity and configured for axial movement relative to the outer shell; a shape memory alloy wire having a shorter remembered shape associated with the inner tubular member to impart axial movement thereto; a digital timing circuit for activating the shape memory alloy wire including a capacitor for providing electrical energy to the shape memory alloy wire to thermally transform the wire to the shorter remembered shape; a biasing member biasing the inner tubular member away from the outer cylindrical shell increasing a size of the cavity; a reservoir containing a fluid and being in fluid communication with the cavity; and wherein as the shape memory alloy wire shortens and imparts axial movement to the inner tubular member, the size of the cavity is reduced thereby forcing fluid out of the cavity via an outlet, and as the biasing member restores the size of the cavity causing a vacuum therein, fluid is pulled from the reservoir into the cavity via an inlet. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A medical device for pumping a fluid, comprising:
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an actuator being disposed adjacent a chamber, the chamber having a resilient tubing, the actuator being in contact with the resilient tubing; a shape memory alloy wire attached to the actuator to impart movement to the actuator; a digital timing circuit for activating the shape memory alloy wire including a capacitor for providing electrical energy to the shape memory alloy wire; and a reservoir containing a fluid and being in fluid communication with the chamber so that as the shape memory wire imparts movement to the actuator, the resilient tubing reacts to the movement of the actuator to expand and thereby pull a predetermined volume of fluid from the reservoir into the chamber. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
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28. A medical device for pumping a fluid, comprising:
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an inner tubular member coaxially aligned within an outer cylindrical shell, the inner tubular member defining a cavity and configured for axial movement relative to the outer shell; a shape memory alloy wire associated with the inner tubular member to impart axial movement thereto; a digital timing circuit for activating the shape memory alloy wire including a capacitor for providing electrical energy to the shape memory alloy wire; a biasing spring connected to the inner tubular member and the outer cylindrical shell; and a reservoir containing a fluid and being in fluid communication with the cavity so that as the shape memory wire imparts axial movement to the inner tubular member, the size of the cavity is increased thereby causing a vacuum which pulls fluid from the reservoir into the cavity, and a restoring force from the biasing spring reduces the size of the cavity pushing the fluid out via an outlet. - View Dependent Claims (29, 30, 31, 32, 33)
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Specification