Air Tolerant Implantable Piston Pump Design
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Solution Overview
Problem
Implantable infusion devices with piston drive mechanisms face issues with air bubbles during refilling, leading to inaccurate delivery and potential pump failure due to incomplete aspiration or degassing procedures, which are time-consuming and prone to improper technique.
Innovation Solution
The design incorporates a piston and piston channel with a small clearance that prevents undissolved gas from passing through, allowing the device to function with incomplete aspiration or degassing, and includes a valve with a cracking pressure that can handle air bubbles, along with a filter to prevent microbial contamination and air entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aspiration or degassing procedures are performed to remove air bubbles from the reservoir, then accurate delivery of therapeutic composition is improved, but the process becomes time-consuming and prone to improper technique
Solution Approach 1:
The patent applies preliminary action by incorporating a vent port that automatically allows air bubbles to escape during the refilling process before the reservoir is completely filled. This prevents air bubble formation in the first place, eliminating the need for subsequent aspiration or degassing procedures. The vent port is positioned and designed to function proactively during filling, addressing the air removal issue before it becomes a problem requiring additional time-consuming steps.
2Reliability
If aspiration or degassing procedures are performed to remove air bubbles, then pump failure is prevented, but the procedures are prone to improper technique
Solution Approach 1:
The patent applies self-service by designing a vent port that automatically performs the air removal function without requiring operator intervention or skill. The vent port's automatic operation during refilling eliminates the need for trained personnel to perform aspiration or degassing procedures, making the system self-sufficient in handling air bubble removal and removing the burden of technique-dependent operations from the user.
3Measurement precision
If a piston pump is used to deliver therapeutic composition, then accurate delivery is achieved, but air bubbles cause inaccurate delivery due to volume occupied by air
Solution Approach 1:
The patent applies the extraction principle by providing a dedicated vent port that specifically removes air bubbles from the reservoir during refilling. The vent port is positioned to allow air to escape while preventing therapeutic composition leakage, effectively separating and removing the harmful air phase from the liquid therapeutic composition before pumping begins, thereby protecting the piston pump's accurate delivery function.
4Ease of operation
If valves are included upstream or downstream of the piston to control flow, then delivery control is improved, but air in the system causes inoperability due to inability to generate sufficient pressure to draw or force air through the valves
Solution Approach 1:
The patent applies preliminary action by removing air bubbles through the vent port during refilling before the piston pump begins operation. This preliminary air removal ensures that when the pump starts and valves are activated, the system contains only liquid therapeutic composition, eliminating the risk of air-related inoperability. The valves can then function reliably for flow control without the complicating factor of air bubbles present in the system.
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 solution enables implantable infusion devices to tolerate air bubbles and ensure accurate delivery of therapeutic compositions, reducing the risk of pump failure and improving safety by preventing inadvertent fluid administration, while also allowing for the use of safety valves and microbial filters.
Implementation Method 1
The clearance between the piston and the channel is sufficiently small such that the infusion medium is retained in the clearance between the piston and the channel via capillary action
Implementation Method 2
surface tension effects prevent the passage of undissolved gas through the clearance
Data Source
AI summary
An implantable infusion device includes a reservoir for housing an infusion medium and a drive mechanism having an inlet chamber, a piston and a piston channel. The inlet chamber is in fluid communication with the reservoir. The piston channel is in fluid communication with the inlet chamber, and has a distal end and a proximal end, the proximal end being closer to the inlet channel than the distal end. The piston is axially moveable within the piston channel to drive infusion medium out of the distal end of the piston channel. The clearance between the piston and the channel is sufficiently small to prevent undissolved gas in the inlet chamber from passing through the clearance. The inlet chamber may be sufficiently large to allow undissolved gas to accumulate without adversely affecting the performance of the infusion device.