Low Impedance Wire Configurations for Medical Devices
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Solution Overview
Problem
Medical device wires face challenges with high resistance leading to power loss and short device lifespan due to material limitations, such as silver's low tensile strength and susceptibility to oxidation, and existing solutions like MP35N require high annealing temperatures causing brittleness and manufacturing complexities.
Innovation Solution
A wire configuration using a low-resistance core surrounded by a biocompatible beta titanium alloy with an elastic modulus of 30 GPa to 90 GPa, allowing for a low-resistance path and enhanced durability, manufactured through a cold drawing and annealing process that prevents core melting and maintains ductility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If silver is used as the wire core material, then electrical resistance is reduced, but tensile strength is insufficient and oxidation susceptibility increases
Solution Approach 1:
The patent employs a composite wire structure with a silver core surrounded by a beta titanium alloy layer. The silver core provides low electrical resistance to minimize power loss, while the beta titanium alloy layer contributes high tensile strength and oxidation resistance. This composite configuration allows the wire to simultaneously achieve low power loss and high mechanical strength that neither material could provide alone.
2Strength
If MP35N wire is used, then tensile strength is improved, but manufacturing complexity increases due to processing difficulties
Solution Approach 1:
The patent changes the material parameters by selecting beta titanium alloy with specific elastic modulus (30-90 GPa) and compositional ranges (containing Ti, Mo, Nb, Ta, Zr, Cr, Fe, and Sn). These parameter selections enable the wire to achieve the required tensile strength while being more amenable to standard manufacturing processes like cold drawing and annealing, thereby reducing manufacturing complexity compared to MP35N.
3Volume of moving object
If wire diameter is reduced to minimize device size, then electrical resistance increases leading to greater power loss
Solution Approach 1:
The composite structure with silver core and beta titanium alloy layer allows the wire to maintain a small diameter while achieving low resistance. The silver core, being an excellent conductor, ensures low electrical resistance even in reduced cross-sections, while the beta titanium alloy provides the necessary mechanical strength to maintain structural integrity at small dimensions, thus minimizing both device size and power loss.
4Strength
If high strength materials are used to withstand repeated bending, then ductility and strain tolerance decrease
Solution Approach 1:
The patent selects beta titanium alloy with elastic modulus specifically in the 30-90 GPa range, which is lower than conventional high-strength wires. This parameter change enables the outer layer to be more ductile and flexible, allowing it to withstand repeated bending and strain while maintaining structural integrity. The combination with the silver core preserves overall tensile strength while improving flexibility and strain tolerance.
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 a durable, low-resistance wire with improved signal transmission and extended device lifespan by minimizing power loss and withstanding repeated bending without brittleness, while simplifying the manufacturing process.
Implementation Method 1
At this temperature, the alloy undergoes a phase transformation from the alpha & beta phase to full beta phase
Implementation Method 2
the wire is annealed by heating it to at least the beta transit temperature of the selected beta titanium alloy
Data Source
AI summary
Techniques are disclosed related to wires that may be used within a medical device. According to one example, a wire may include a core formed of a material having a resistivity of less than 25 micro-ohm-cm and a layer of a biocompatible beta titanium alloy surrounding the core. As one example, the beta titanium alloy has an elastic modulus ranging from 30 GigaPascals (GPa) to 90 GPa and comprises at least two elements from a group consisting of titanium, molybdenum, niobium, tantalum, zirconium, chromium, iron and tin. In one embodiment, the core may be formed of silver, tantalum, a tantalum alloy, niobium, a niobium alloy, platinum, a platinum alloy, palladium, or a palladium alloy. In some examples, one or more wires may be incorporated into a coil or a cable and one or more such coils or cables may be carried by a medical device such as a medical electrical lead.