Offset Slit Septum for Low-Drag Catheter Sealing
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Solution Overview
Problem
Existing septa in catheter and introducer needle assemblies experience high frictional forces during needle extraction, making it difficult and uncomfortable to remove the needle, especially with one hand, due to interference fits that create drag forces resisting needle withdrawal.
Innovation Solution
A septum with an offset slit configuration that applies primarily indirect radial compression forces, transitioning to a collapsed state under high pressure to maintain sealing while reducing drag forces during needle extraction, featuring a tube and plug portion that increases compressive force on the slit for enhanced sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an interference fit is used between the catheter assembly and introducer needle assembly to create radial compression forces on the introducer needle, then sealing functionality is improved, but frictional forces increase making needle extraction difficult
Solution Approach 1:
The septum is divided into distinct functional zones: a compression zone with radial compression forces for sealing, and a low-friction zone with PTFE coating for easy needle extraction. This segmentation allows different regions of the septum to perform different functions - the compression zone maintains the seal while the low-friction zone reduces extraction resistance
Solution Approach 2:
Different regions of the septum are given different surface properties: the region in contact with the catheter assembly has high friction for sealing, while the region contact with the introducer needle has low friction (PTFE coating) for easy extraction. This local differentiation of surface qualities resolves the contradiction between maintaining seal integrity and enabling smooth needle removal
2Reliability
If radial compression forces are applied to the introducer needle to prevent fluid outflow, then sealing effectiveness is improved, but drag forces resisting needle extraction increase
Solution Approach 1:
The septum structure separates the sealing function from the extraction function. The compression zone applies radial forces for sealing effectiveness, while the PTFE-coated zone minimizes drag forces during extraction. This segmentation allows the system to achieve both high sealing effectiveness and low extraction resistance simultaneously
Solution Approach 2:
PTFE coating acts as an intermediary layer between the introducer needle and the septum. This intermediary material provides a low-friction interface that reduces drag forces during needle extraction while allowing the compression zone to maintain effective sealing forces
3Reliability
If frictional forces are increased to maintain seal closure after needle withdrawal, then sealing reliability is improved, but needle removal becomes painful and uncomfortable
Solution Approach 1:
The septum applies local quality differentiation by providing high friction only where needed for seal closure (catheter-septum interface) while providing low friction at the needle-septum interface through PTFE coating. This localized friction management ensures reliable seal closure without transmitting harmful frictional forces to the needle extraction process, thereby eliminating pain and discomfort
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 septum provides a low-drag, high-pressure sealing capability, facilitating easy needle withdrawal with reduced friction and maintaining an effective seal against high pressures within the catheter assembly.
Implementation Method 1
the septum can be further configured to transition to a collapsed state, generally after the introducer needle is removed, when a relatively high pressure is applied to the distal face of the septum
Implementation Method 2
The compression forces operating on the introducer needle can also function to close the septum and maintain the septum closed after the introducer needle is removed. The interference fit closing the septum after needle withdrawal can introduce frictional forces at the needle-septum interface
Data Source
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AI summary
A septum is disclosed that can be utilized in a catheter assembly to selectively seal an opening in the catheter assembly. The septum has a tube portion and a plug portion. The plug portion has a slit extending through it. The septum can transition from a non-collapsed state to a collapsed state. When the septum is in a non-collapsed state, the plug portion is offset from the tube portion such that some of the length of the slit extends outward from the distal end of the tube portion. When the septum transitions to the collapsed state, the plug portion is moved inward into the internal cavity such that some of the length of the slit may or may not extend outward from the distal end of the tube portion.