Superelastic Tine Cross-Section Design for Fatigue Resistance
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Solution Overview
Problem
Current tissue-penetrating fixation components for implantable medical devices face challenges in strain relief during flexing, particularly during initial implantation and chronic implantation within a beating heart, where cyclic loading can lead to fatigue and potential failure.
Innovation Solution
The design incorporates tine portions with a hook segment having a round cross-section and a distal segment with a flattened cross-section, pre-set to extend along specific angles, and integrally formed from superelastic materials like Nitinol, providing enhanced strain relief and fatigue resistance through stress distribution and elastic deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If tine portions are made rigid for strong fixation, then fixation strength is improved, but resistance to cyclic loading and fatigue resistance deteriorate
Solution Approach 1:
The patent changes the physical parameters of the tine portions by using superelastic materials (Nitinol) with specific elastic properties, transforming the rigid structure into a flexible one that can undergo large deformations while maintaining strength, thereby resolving the contradiction between fixation strength and fatigue resistance
Solution Approach 2:
The patent employs composite construction by integrating multiple tine portions with different geometric configurations (hook-shaped, J-shaped, arrow-shaped) made from superelastic materials into a unified fixation component, combining the advantages of flexibility and strength to simultaneously achieve strong fixation and high fatigue resistance
2Reliability
If tine portions are made flexible to resist cyclic loading, then fatigue resistance is improved, but fixation strength deteriorates
Solution Approach 1:
The patent optimizes the elastic parameters of the superelastic material and the geometric parameters of the tine portions (cross-sectional dimensions, curvature radii, lengths) to achieve a balance where the tines are flexible enough to resist cyclic loading yet maintain sufficient fixation strength through their elastic recovery force
3Reliability
If stress concentration is reduced through design modifications, then fatigue resistance is improved, but fixation effectiveness may deteriorate
Solution Approach 1:
The patent applies local quality by giving different cross-sectional shapes to different parts of the tine portions (e.g., rounded cross-sections at stress concentration points, flattened or irregular cross-sections in other areas), optimizing both fatigue resistance at critical locations and overall fixation effectiveness
Solution Approach 2:
The patent uses curved and rounded geometric features (rounded cross-sections, arc-shaped hooks, J-shaped configurations) to eliminate sharp corners and stress concentration points, thereby improving fatigue resistance while maintaining fixation effectiveness through the curved geometry's elastic properties
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
This configuration enhances the fixation and durability of implantable medical devices by reducing stress concentration and improving cyclic loading resistance, ensuring stable performance over hundreds of millions of heartbeats.
Implementation Method 1
Each tine portion 230 is preferably formed from a superelastic material, such as Nitinol (a metal alloy of nickel and titanium)
Implementation Method 2
the hook segment is pre-set to extend along a curvature that encloses an angle of between 135 degrees and 270 degrees, from a proximal end thereof to a distal end thereof, and which is elastically deformable from the pre-set curvature to an open position
Data Source
AI summary
A tine portion for an implantable medical device includes a hook segment and a distal segment terminated by a tissue-piercing tip, wherein the distal segment extends from the hook segment to the tip. The hook segment, which is elastically deformable from a pre-set curvature, has one of: a round cross-section and an elliptical cross-section, while the distal segment has a flattened, or approximately rectangular cross-section. One or a pair of the tine portions may be integrally formed, with a base portion, from a superelastic wire, wherein the base portion is configured to fixedly attach to the device, for example, being captured between insulative members of a fixation subassembly.