Nested Coil Guidewire for Stiffness and Flexibility Trade-off
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Solution Overview
Problem
Medical guidewires face challenges in achieving high safety, flexibility, and rotation followability, especially when used in delicate areas like the brain, where they need to maintain stiffness for guiding microcatheters while preventing vessel damage and restoring shaped angles.
Innovation Solution
A guidewire design featuring a core shaft surrounded by an inner and outer coil structure, with a coil joint connecting only the outer and inner coils, providing flexibility and rotation followability while maintaining stiffness through a radiopaque and radiolucent material configuration, and a hollow stranded inner coil for improved torque transmissibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the diameter of the core shaft is increased to enhance stiffness for guiding microcatheters, then the stiffness is improved, but the flexibility is lost and the restorability of the distal shape deteriorates
Solution Approach 1:
The guidewire is divided into multiple functional segments: a core shaft for stiffness, an inner coil for flexibility and rotation followability, and an outer coil for additional flexibility. This segmentation allows each component to contribute its specific properties, resolving the contradiction between overall stiffness and distal flexibility.
Solution Approach 2:
The inner coil is nested within the outer coil, which in turn surrounds the core shaft. This nested structure allows the stiffer core shaft to provide guiding strength while the surrounding coils provide flexibility and rotation followability, enabling the guidewire to maintain both stiffness and flexibility simultaneously.
2Strength
If the diameter of the core shaft is increased to enhance stiffness, then the stiffness is improved, but the distal shape formed by shaping becomes difficult to retain and restorability deteriorates
Solution Approach 1:
The guidewire structure separates the stiffness function (core shaft) from the shape retention function (coils). The coils with their elastic properties can retain the shaped distal configuration while the core shaft provides the necessary stiffness for microcatheter guidance.
Solution Approach 2:
The inner and outer coils act as flexible shells surrounding the core shaft. These coil structures can elastically deform to form and retain shaped configurations while maintaining the overall structural integrity provided by the core shaft, thus improving shape retention without sacrificing stiffness.
3Reliability
If a double coil structure is provided to improve flexibility and rotation followability, then safety is improved, but the device complexity increases
Solution Approach 1:
The inner coil and outer coil are joined together at specific locations (front ends to the tip and rear ends to the core shaft), merging their functions into a unified structure. This combination allows both coils to work together to provide flexibility and rotation followability while reducing the overall complexity compared to completely independent coil systems.
Solution Approach 2:
The nested configuration of the inner coil within the outer coil allows for a compact structure that provides enhanced flexibility and rotation followability without proportionally increasing the overall device complexity. The nested design efficiently uses space and reduces the number of separate components needed.
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 guidewire achieves enhanced safety and flexibility, maintaining the shaped angle and preventing vessel damage with improved rotation followability and pushability, ensuring effective guidance of microcatheters without abrupt stiffness changes.
Implementation Method 1
an inner coil that is formed by winding at least one strand, and surrounds a distal side portion of the core shaft; an outer coil that is formed by winding at least one strand, and surrounds the inner coil and the distal side portion of the core shaft
Data Source
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AI summary
Guidewire having high safety and improved flexibility and rotation followability. This guidewire has an inner coil (50) that surrounds a distal side (30) portion of a core shaft (14), and an outer coil (60) that surrounds the inner coil and the distal side portion of the core shaft. A front end of the outer coil and a front end of the inner coil are joined to a tip of the core shaft by a tip plug (15). Further, the guidewire has a coil joint that joins only the outer coil and the inner coil to each other. With this configuration, the flexibility of the inner coil is maintained. Moreover, rotation of a proximal side of the guidewire is transmitted to the inner coil not only from the core shaft but also from the outer coil. This leads to improvement in rotation followability.