Composite Cannula Wall Structure for Bending Resistance and Transparency
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Solution Overview
Problem
Cannulas used in minimally-invasive surgery face challenges in maintaining stability and resistance to bending forces, particularly in thoracic regions and muscular body walls, while also requiring transparency and small outer dimensions to minimize trauma.
Innovation Solution
A cannula design featuring a strengthened portion made of reinforced plastic with glass or carbon fibers and a transparent portion made of clear plastic, joined by welding or overmolding, with varying wall thickness to enhance stiffness and maintain transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the cannula outer lateral dimensions are minimized to reduce trauma, then the port size is reduced, but the cannula strength and resistance to bending forces deteriorate
Solution Approach 1:
The cannula is constructed as a composite structure combining a transparent plastic material (providing transparency and basic structural integrity) with a strengthening material (providing enhanced bending resistance). This allows the cannula to maintain small outer dimensions while achieving the required strength properties through material composition rather than dimensional increase.
2Strength
If the cannula wall thickness is increased to improve strength, then the resistance to bending forces improves, but the transparency and visualization capability deteriorate
Solution Approach 1:
The cannula wall is constructed as a composite of transparent plastic and strengthening material, allowing adequate wall thickness for bending resistance while maintaining transparency. The transparent plastic component ensures light transmission is preserved despite the increased wall thickness required for structural strength.
Solution Approach 2:
The strengthening material is strategically positioned in specific regions of the cannula wall where bending forces are most likely to occur, rather than uniformly thickening the entire wall. This localized reinforcement provides the necessary strength while minimizing impact on overall transparency and allowing thinner walls in other regions.
3Ease of manufacture
If the cannula is made of inexpensive disposable plastic, then the cost is reduced, but the strength and stability deteriorate
Solution Approach 1:
The cannula combines inexpensive transparent plastic with cost-effective strengthening materials (such as metal alloys or reinforced polymers) to achieve enhanced stability and resistance to bending forces while maintaining disposable characteristics. The composite structure provides superior mechanical properties compared to standard plastic alone.
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 design provides enhanced resistance to bending forces and maintains transparency, allowing for better visualization and reduced trauma to the body wall, while keeping the cannula's outer dimensions minimal.
Implementation Method 1
a strengthened portion made of reinforced plastic with glass or carbon fibers
Implementation Method 2
joined by welding or overmolding
Implementation Method 3
joined by welding or overmolding
Data Source
AI summary
A cannula may include a bowl portion comprising a first opening and a second opening, and an insertion tube extending from the bowl portion. The insertion tube defines a passage extending from the second opening and terminating in a distal end opening. The passage is configured to receive an instrument to be advanced through the cannula. The insertion tube has a transparent portion extending proximally from the distal end opening, and a strengthened portion extending proximally from the transparent portion.