Joined Dissimilar-Metal Hypotubes for Stiffness and Kink Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional medical devices with single-material hypotubes lack optimal combinations of stiffness, kink resistance, and torque transmission, as materials like stainless steel and Nitinol have difficulty forming strong joints due to brittle intermetallic alloys, compromising joint strength.
Innovation Solution
Joining hypotubes made of dissimilar materials like Nitinol and MP35N or stainless steel using laser welding with optional filler materials like MP35N, Co, Ni, or Cu to form joints that maintain consistent diameters and prevent material migration, ensuring structural integrity and varying properties along the device length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If stainless steel hypotubes are used, then stiffness and torque transmission are improved, but kink resistance and shape retention deteriorate
Solution Approach 1:
The hypotube is divided into multiple segments made of different materials (e.g., stainless steel, Nitinol, MP35N) with each segment providing specific properties. The stainless steel segments provide stiffness and torque transmission, while Nitinol segments provide kink resistance and shape retention, resolving the contradiction between these opposing requirements.
Solution Approach 2:
The invention uses composite construction by joining different metal alloys (stainless steel, Nitinol, MP35N) to create a hypotube that combines the advantages of each material. This allows the device to simultaneously achieve high stiffness from stainless steel and excellent kink resistance from Nitinol, which cannot be achieved with single-material hypotubes.
2Reliability
If Nitinol hypotubes are used, then kink resistance and shape retention are improved, but stiffness and torque transmission deteriorate
Solution Approach 1:
The hypotube is segmented into Nitinol portions for kink resistance and stainless steel or MP35N portions for stiffness, allowing each material to perform its optimal function without compromising the other.
Solution Approach 2:
By combining Nitinol with stiffer materials like stainless steel or MP35N in a composite hypotube structure, the invention achieves both high kink resistance from Nitinol and adequate stiffness from the other materials, resolving the trade-off between these properties.
3Adaptability or versatility
If dissimilar materials are joined, then differing properties along device length are achieved, but joint strength deteriorates due to brittle intermetallic alloys
Solution Approach 1:
The invention uses intermediate materials or transition layers (such as specific alloy compositions like MP35N or controlled filler materials) at the joints between dissimilar materials to prevent direct formation of brittle intermetallic compounds. This intermediary approach maintains joint strength while allowing dissimilar materials to be connected for differentiated properties along the device length.
Solution Approach 2:
The invention controls joining parameters (temperature, time, atmosphere, filler material composition) to prevent brittle intermetallic alloy formation at joints between dissimilar materials. By changing these process parameters, strong joints are achieved while maintaining the ability to connect different materials for varying properties along the device.
4Adaptability or versatility
If hypotubes are joined, then differing properties along length are achieved, but passageway consistency deteriorates due to material migration during joining
Solution Approach 1:
Barrier layers or intermediate materials are used at the joints to prevent material migration into the passageway during the joining process. This intermediary protection maintains passageway consistency and prevents contamination while still allowing the dissimilar materials to be joined for differentiated device properties.
Solution Approach 2:
The joining process parameters (temperature, time, atmosphere control) are optimized to minimize material migration and prevent contamination of the passageway. By controlling these parameters, the invention achieves both material joining for varying properties and maintenance of passageway consistency.
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 provides medical devices with enhanced stiffness, torque transmission, and kink resistance by forming reliable joints between dissimilar materials, maintaining consistent passageways and preventing material intrusion, thus improving the device's performance and durability.
Implementation Method 1
Joining hypotubes made of dissimilar materials like Nitinol and MP35N or stainless steel using laser welding
Data Source
AI summary
In various examples, an apparatus includes a first hypotube formed from a first material and a second hypotube formed from a second material different from the first material. A first joint is formed between the first hypotube and the second hypotube, the first joint including a combination of the first material and the second material. The apparatus includes a sidewall and a passageway extending through the apparatus. The sidewall is formed by the first sidewall of the first hypotube, the second sidewall of the second hypotube, and the first joint. The apparatus includes an outer diameter that is substantially consistent along a length of the apparatus and an inner diameter that is substantially consistent along a length of the apparatus. In other examples, a method of joining the first hypotube to the second hypotube is contemplated.