Guidewire Double Coil Structure Torsional Stiffness
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Solution Overview
Problem
Medical guidewires face challenges in achieving high safety, flexibility, and rotation followability, especially when navigating delicate blood vessels like those in the brain, where they need to guide microcatheters through tortuous vessels while preventing damage and maintaining ease of direction change.
Innovation Solution
A guidewire design featuring a core shaft surrounded by an inner and outer coil structure, with a flat portion expanding to contact the inner coil and a coil joint connecting the outer and inner coils, enhancing flexibility and torsional stiffness while maintaining safety by distributing loads and preventing bending or kinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the tip portion of the guidewire is made with high torsional stiffness to easily change the direction of the catheter, then the ease of operation is improved, but the flexibility and safety are worsened
Solution Approach 1:
The guidewire is divided into distinct functional segments: a tip portion with high torsional stiffness for easy direction control, and a distal side portion with high flexibility for safety. The stiffness value of the tip portion is set to 0.005-0.020 kgf·m, while the distal side portion has a stiffness of 0.001-0.005 kgf·m, creating a gradient that resolves the contradiction between operational ease and safety.
Solution Approach 2:
Different portions of the guidewire are given different mechanical properties tailored to their specific functions. The tip portion is designed with higher torsional stiffness to facilitate catheter direction control, while the distal side portion is designed with lower stiffness and higher flexibility to ensure safety in delicate blood vessels. This local differentiation allows each section to optimize its performance for its intended purpose.
2Reliability
If the guidewire is made more flexible to improve safety in delicate blood vessels, then the reliability is improved, but the rotation followability is worsened
Solution Approach 1:
The guidewire structure is segmented into a tip portion and a distal side portion, each with optimized stiffness characteristics. The tip portion maintains higher torsional stiffness (0.005-0.020 kgf·m) to ensure rotation followability, while the distal side portion uses lower stiffness (0.001-0.005 kgf·m) for flexibility and safety, resolving the contradiction through spatial segmentation of mechanical properties.
Solution Approach 2:
The invention introduces a stiffness gradient along the axial dimension of the guidewire. By varying the stiffness value along the length of the guidewire (higher at the tip, lower at the distal side), it creates a dimensional transition that allows the tip to maintain rotation followability while the distal side provides flexibility, thus resolving the contradiction through dimensional variation.
3Reliability
If a double coil structure is used to improve flexibility and rotation followability, then the reliability is improved, but the device complexity is worsened
Solution Approach 1:
The double coil structure is applied selectively only to the tip portion of the guidewire, rather than the entire length. This segmentation allows the complex double coil structure to be used where it is most needed for rotation followability, while the distal side portion uses a simpler structure, thus balancing reliability improvement with acceptable device complexity.
Solution Approach 2:
The double coil structure is implemented locally in the tip portion where high rotation followability is critical for catheter manipulation. The distal side portion uses a different, simpler construction that provides flexibility without the complexity of a double coil. This local application of structural complexity resolves the contradiction between improved reliability and reduced overall device complexity.
Data Source
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AI summary
Guidewire having high safety and improved flexibility and rotation followability, and capable of directing a catheter with ease. The guidewire has an inner coil (50) that surrounds a distal side portion (30) of a core shaft (14), and an outer coil (60) that surrounds the inner coil and the distal side portion of the core shaft. The core shaft has a second flat part (44) in flattened shape in substantially contact with an inner peripheral surface of the inner coil. With this configuration, the distal side portion of the guidewire is protected by a double coil structure, while having high torsional stiffness. This leads to improvement in safety and rotation followability, while allowing a catheter to be directed with ease.