SMA Valve Drive Unit for Precise Infusion Pump Switching
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Solution Overview
Problem
Ambulatory infusion pumps face challenges with precision and cost-effectiveness due to complex designs and high manufacturing costs, particularly in the dosing units, which require precise metering of small drug volumes and have a shorter lifetime than other components.
Innovation Solution
A compact and cost-efficient valve drive unit utilizing Shape Memory Alloy (SMA) wires as actuators, which transform length variations into rotational movements to control valve switching, allowing for precise and reliable drug administration without the need for complex mechanical kinematics, and enabling modular design for easy replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a micro membrane pump or micro piston dosing unit is used to achieve precise metering of small volumes, then dosing precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The dosing unit is divided into separate functional modules: a disposable dosing cartridge containing the micro piston and dosing cylinder, and a reusable drive unit containing the motor and control electronics. This segmentation allows the complex precise metering mechanism to be manufactured once in the reusable unit while keeping the disposable unit simple and cost-effective.
Solution Approach 2:
The dosing cartridge with micro piston and dosing cylinder is designed as a disposable component with limited lifetime, while the expensive drive unit with motor and control electronics is reused. This allows the complex precision components to be manufactured once to high standards, while the disposable portion can be manufactured simply and cheaply at scale.
2Device complexity
If a common actuator is used for both piston movement and valve switching, then device complexity is reduced, but reliability decreases due to critical design issues
Solution Approach 1:
The actuation system is segmented into two independent actuators: a motor-driven spindle mechanism for reliable piston movement and dosing, and a separate valve driver with cam mechanism for reliable valve switching. This segmentation eliminates the critical design issues of using a single actuator for multiple functions while maintaining overall system simplicity through modular architecture.
Solution Approach 2:
A cam mechanism is introduced as an intermediary between the valve driver rotation and the valve actuation. This cam mechanism provides reliable valve switching through its geometric design, decoupling the valve switching function from the piston drive mechanism while maintaining simplicity through the passive mechanical interaction.
3Reliability
If separate drives with separate dedicated actuators are used for valve switching and piston movement, then reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The drive system is segmented into two independent actuation mechanisms: a motor-driven spindle for piston movement and a valve driver with cam for valve switching. Each segment is optimized for its specific function, improving reliability while the modular disposable/reusable segmentation keeps overall complexity manageable.
Solution Approach 2:
The valve driver uses a rotating cam mechanism that dynamically converts rotational motion into the required valve actuation motion. This dynamic mechanical linkage provides reliable valve control through its geometric design, eliminating the need for complex electronic control while maintaining independence from the piston drive system.
4Measurement precision
If complex mechanical kinematics are used to achieve precise metering, then dosing precision is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The precise metering function is segmented into the disposable dosing cartridge containing the micro piston and dosing cylinder, separate from the reusable drive unit. This allows the precision components to be manufactured once to high standards in a controlled environment, while the disposable unit can be manufactured simply and cheaply at scale using simpler processes.
Solution Approach 2:
The dosing cartridge with precise metering components is designed as a disposable item with limited lifetime. This enables the use of high-precision manufacturing processes for the critical metering components without concern for long-term cost, while the disposable nature allows for simple, cost-effective manufacturing at scale. The reusable drive unit amortizes the high manufacturing cost over many disposable cartridges.
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 SMA-based valve drive unit provides a robust, cost-effective solution for ambulatory infusion pumps, ensuring precise drug administration and simplifying the coupling process, while reducing manufacturing complexity and costs, and extending the lifetime of the dosing unit.
Implementation Method 1
A valve drive unit (1) includes a first Shape Memory Alloy (SMA) wire (10a) and a second SMA wire (10b) which can be alternatively activated
Data Source
AI summary
Disclosed is a valve drive unit that has first and second SMA wires that can be alternatively activated. The valve drive unit further includes a pivoting member pivotably arranged around a pivoting member axis, the pivoting member including a valve driver arranged at a distance from the pivoting member axis. The first and second SMA wires are coupled to the pivoting member such that an activation of the first SMA wire causes the pivoting member to pivot into a first direction and an activation of the second SMA wire causes the pivoting member to pivot into a second direction, the second direction being opposite to the first direction. The valve driver is configured to releasably engage a valve driver coupler of a valve unit, such that, in the engaged state, a pivoting of the pivoting member is transmitted to the valve driver coupler via the valve driver.