Composite Nitinol-Steel Basket Legs for Stone Retrieval
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Solution Overview
Problem
Conventional medical retrieval devices face challenges in achieving a balance between basket flexibility and strength due to being made from single materials, which limits their mechanical characteristics and effectiveness in capturing and removing stones from within the body.
Innovation Solution
The medical retrieval device employs a composite structure with a nitinol inner core and a stainless steel outer layer, featuring varying cross-sections and voids to enhance flexibility and strength, allowing for a balanced mechanical behavior and improved stone retrieval capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If basket legs are made of steel, then strength is improved, but flexibility deteriorates
Solution Approach 1:
The basket legs are constructed using composite materials, specifically combining steel and nitinol. The steel provides the necessary structural strength while the nitinol component contributes flexibility and shape memory properties. This composite construction allows the basket to maintain both high strength and adaptability, resolving the contradiction between these two mechanical properties.
Solution Approach 2:
Different sections of the basket legs have different material compositions optimized for their specific functional requirements. The proximal portions may have different steel-to-nitinol ratios compared to distal portions, allowing each section to have the local mechanical properties needed for its specific role in the basket's operation.
2Adaptability or versatility
If basket legs are made of nitinol, then flexibility is improved, but strength deteriorates
Solution Approach 1:
The composite construction combines nitinol's superior flexibility and shape memory characteristics with steel's high strength. By integrating these two materials in a composite structure, the basket legs achieve both the flexibility needed for navigation through constricted areas and the strength required for effective stone capture and retrieval.
3Ease of manufacture
If single material is used, then manufacturing simplicity is improved, but mechanical performance deteriorates
Solution Approach 1:
While the composite construction adds manufacturing complexity compared to single-material baskets, it significantly improves mechanical performance by combining the complementary properties of steel and nitinol. The manufacturing process is managed through established techniques for joining dissimilar metals, achieving reliable composite structures that outperform single-material alternatives.
Solution Approach 2:
The invention optimizes various parameters including the ratio of steel to nitinol, the distribution of materials along the leg length, and the geometric configuration of the composite structure. These parameter optimizations balance the competing requirements of manufacturing feasibility and mechanical performance.
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 composite structure enables the device to effectively capture and remove stones by providing the necessary flexibility and strength, reducing trauma to surrounding tissue and improving the ability to retrieve stones in constricted areas.
Implementation Method 1
at least one of the legs including a wire having an inner core at least partially surrounded by an outer layer. The inner core is comprised of a first material and the outer layer is comprised of a second material that is more rigid than the first material. The first material is nitinol
Implementation Method 2
The inner core is comprised of a first material... The first material is nitinol... exhibiting less strength
Implementation Method 3
The outer layer is comprised of a second material that is more rigid than the first material. The second material is stainless steel
Data Source
AI summary
A medical retrieval device of an embodiment of the present disclosure includes a proximal handle, a sheath, and a retrieval assembly. The sheath extends from the handle and includes a lumen and a distal end opposite the handle. The retrieval assembly is moveable relative to the sheath to achieve a collapsed position of the retrieval assembly within the lumen and an expanded position of the retrieval assembly when extended outside the lumen. The retrieval assembly includes a plurality of legs. At least one of the legs includes a wire having an inner core at least partially surrounded by an outer layer.