Oblong Shocking Electrodes for Implantable Devices
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Solution Overview
Problem
Conventional implantable medical device (IMD) shocking electrodes with cylindrical cross-sections are challenging to convert into oblong shapes, which could reduce shocking impedance, as they tend to revert to their original shape due to residual tension and are difficult to manufacture consistently.
Innovation Solution
The use of a coiled conductor with an oblong cross-sectional shape, formed by helically wrapping a multi-filar ribbon wire, micro-coil, or micro-cable, with structural strands to maintain the shape, and an overmold material to retain the oblong shape, along with methods like heat treatment or laser ablation to remove the overmold material after forming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a cylindrical shocking electrode is flattened to an oblong shape to increase surface area and reduce impedance, then the shocking impedance decreases and energy demand is reduced, but the electrode tends to revert to its cylindrical shape due to residual tension and is difficult to manufacture consistently
Solution Approach 1:
The conductor is formed with an oblong cross-sectional shape during the winding process itself, rather than attempting to flatten a cylindrical electrode afterward. The mandrel is designed with an oblong cross-section that matches the desired final electrode shape, establishing the correct geometry from the beginning of manufacturing.
Solution Approach 2:
A mandrel with an oblong cross-sectional shape is used as an intermediary tool during the winding process. This mandrel temporarily supports the conductor in the desired oblong configuration and allows the winding to be performed with consistent tension, ensuring shape consistency without requiring post-forming operations.
2Area of stationary object
If a non-cylindrical mandrel is used to form oblong shocking electrodes, then the electrode surface area increases, but the tension in the conductor fluctuates and variable tension causes undesirable inherent stress and torsion
Solution Approach 1:
The mandrel is designed with an oblong cross-section that has different dimensions in different directions, allowing the conductor to be wound with appropriate tension distribution. The larger dimension of the oblong mandrel provides a stable baseline for winding while the smaller dimension helps maintain uniform tension, preventing fluctuations that would cause stress and torsion.
3Ease of manufacture
If conventional cylindrical shocking electrodes are used, then the manufacturing process is simple, but the surface area is insufficient resulting in higher impedance and greater energy demand
Solution Approach 1:
The shocking electrode is designed with an oblong (asymmetric) cross-sectional shape rather than a symmetric cylindrical shape. This asymmetric geometry provides a larger surface area in contact with patient tissue, reducing the impedance and allowing the same defibrillation function to be achieved with lower energy demand.
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 approach allows for the reliable and consistent production of oblong shocking electrodes with reduced impedance, enabling lower energy demands for defibrillation therapy and smaller IMD components.
Implementation Method 1
heat treatment or laser ablation to remove the overmold material after forming
Implementation Method 2
heat treatment or laser ablation to remove the overmold material after forming
Data Source
AI summary
Shocking electrodes for implantable medical devices may include a coiled conductor that has an oblong cross-sectional shape and is configured to deliver high-voltage shocks for defibrillation therapy. The coiled conductor includes an electrically conductive element that is helically wrapped and defines the oblong cross-sectional shape. The electrically conductive element is one of (i) a multi-filar ribbon wire that includes multiple strands disposed side-by-side along a length of the multi-filar ribbon wire, (ii) a micro-coil that includes a coiled strand, or (iii) a micro-cable that includes multiple interwoven strands along a length of the micro-cable.