SMA Wire Pump Control for Temperature-Compensated Dosing
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Solution Overview
Problem
Existing portable and wearable fluid delivery devices for therapeutics, such as infusion pumps, face challenges including high malfunction rates, size, weight, and cost issues, as well as skin application and re-location difficulties, while also requiring precise control for effective drug delivery.
Innovation Solution
A wearable infusion pump assembly utilizing shape-memory alloy wires for controlled fluid delivery, which includes a temperature-compensated actuation system to adjust pumping time based on the wire's temperature, ensuring accurate volume measurement and delivery through a combination of sensors and controllers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If shape-memory alloy wires are used for pump actuation, then device size and weight are reduced, but actuation precision deteriorates due to temperature sensitivity
Solution Approach 1:
The patent implements a feedback control system that monitors the actual pump output volume and compares it to the target volume. The controller adjusts the actuation parameters of the shape-memory alloy wire based on this feedback to compensate for temperature-induced variations, thereby maintaining precise actuation control despite the inherent temperature sensitivity of the SMA material.
Solution Approach 2:
The patent dynamically changes the actuation parameters (such as pulse width, amplitude, or duration of electrical stimulation) of the shape-memory alloy wire based on detected temperature conditions and pump output measurements. By adjusting these parameters in real-time, the system compensates for temperature effects and maintains precise control over pump actuation.
2Reliability
If temperature compensation is implemented, then actuation reliability is improved, but device complexity increases
Solution Approach 1:
The patent integrates multiple functions into the existing controller unit. The same controller that manages pump actuation also performs temperature monitoring, pump output measurement, and compensation calculations. By making the controller multi-functional, the system achieves temperature compensation and improved reliability without adding separate dedicated hardware components for each function.
Solution Approach 2:
The patent combines the temperature sensing, volume measurement, and actuation control functions into a single integrated control system. The controller simultaneously processes data from temperature sensors and pump output measurements, then coordinates the actuation of shape-memory alloy wires. This merging of functions reduces the number of separate components and simplifies the overall system architecture.
3Measurement precision
If precise volume measurement is implemented, then dosing accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent employs a self-measuring approach where the pump system itself generates the measurement signal through its operation. The volume measurement is derived from monitoring the electrical characteristics (such as current or voltage) during the actuation of shape-memory alloy wires, which are inherently related to the mechanical displacement and fluid delivery. This eliminates the need for separate, expensive precision measurement instruments.
Solution Approach 2:
The patent replaces traditional mechanical volume measurement mechanisms (such as displacement sensors or flow meters) with an electrical measurement approach. By monitoring electrical parameters during SMA wire actuation, the system infers volume delivery with high precision. This substitution of electrical sensing for mechanical sensing reduces manufacturing complexity and cost while maintaining or improving measurement accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enhances the reliability and precision of fluid delivery by dynamically adjusting actuation times based on temperature, reducing malfunctions and improving user convenience through accurate dosing and reduced device size and weight.
Implementation Method 1
a pump plunger (106) and at least one shape-memory alloy wire (112) operably connected to the pump plunger (106), wherein the shape-memory alloy wire (112), when actuated, actuates the pump plunger (106)
Implementation Method 2
a temperature sensor for determining the temperature of the shape-memory alloy wire, wherein the controller determines the ontime based on the predictive temperature of the shape-memory alloy wire before actuation
Data Source
AI summary
A method for controlling a device using a shape-memory alloy wire is disclosed. The method includes determining an ontime for the shape-memory alloy wire based on a target volume to be pumped by a pump plunger, determining the temperature of the shape-memory alloy wire and adjusting the ontime based on the temperature of the shape-memory alloy wire.