Multi-Cable Inductor Assembly for Medical Implants
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Solution Overview
Problem
Conventional antenna coils for transcutaneously powered medical implants, such as cochlear implants, have high manufacturing costs, low tensile strength, and suboptimal electrical performance due to the use of thin multi-wire biocompatible metal cables, resulting in high resistance and low Q factor values.
Innovation Solution
A multi-cable inductor assembly with a specific conductor spacing to diameter ratio, utilizing Litz wires with a silver alloy core and nickel alloy tube, arranged in a hexagonal formation to reduce skin and proximity effects, enhancing tensile strength and electrical efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If thin multi-wire biocompatible metal cables are used in conventional antenna coils, then the implant can be made thin and biocompatible, but the tensile strength becomes low and manufacturing becomes complicated
Solution Approach 1:
The patent uses composite conductor construction combining copper wire (for electrical conductivity) with stainless steel braiding (for tensile strength). This composite approach allows the antenna to achieve both thin profile and high mechanical strength, resolving the contradiction between implant thickness and tensile strength.
Solution Approach 2:
The conductor assembly serves multiple functions simultaneously: the copper provides electrical conductivity for inductive coupling, while the stainless steel braiding provides mechanical strength and structural support. This multi-functionality eliminates the need for separate structural support elements, keeping the implant thin.
2Length of moving object
If thin multi-wire biocompatible metal cables are used in conventional antenna coils, then the implant can be made thin, but the resistance becomes high and Q factor becomes low
Solution Approach 1:
The copper conductor core provides superior electrical conductivity compared to biocompatible alloys like platinum or titanium. By using copper specifically for its electrical properties while relying on the stainless steel braiding for mechanical properties, the antenna achieves low resistance and high Q factor while maintaining thin profile.
Solution Approach 2:
Different materials are assigned to different functional requirements within the conductor: copper for electrical conductivity (local electrical property optimization) and stainless steel for mechanical strength (local mechanical property optimization). This local quality differentiation resolves the contradiction between thin profile and energy efficiency.
3Reliability
If conventional multi-wire biocompatible metal cables are used, then biocompatibility is achieved, but manufacturing cost becomes high
Solution Approach 1:
The conductor uses copper and stainless steel, which are more cost-effective than conventional biocompatible antenna materials like platinum, titanium, or nitinol. The stainless steel outer braid provides adequate biocompatibility while the copper core provides conductivity, creating a cost-effective composite solution.
Solution Approach 2:
The patent employs more economical materials (copper and stainless steel) compared to expensive biocompatible alloys. While copper is not inherently biocompatible, the stainless steel braiding provides the biocompatible interface with tissue, allowing the use of cheaper materials overall without compromising biocompatibility.
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 achieves a significantly higher Q factor, indicating lower energy loss and improved efficiency, with Q values up to 65% higher than conventional antennas, while maintaining flexibility and biocompatibility.
Implementation Method 1
an inductor assembly that includes a plurality of metallic conductors which are positioned relative to one another such that there is a predetermined relationship between the conductor spacing and the conductor diameter
Implementation Method 2
Inductive links are commonly used to transmit power and data to implanted medical devices
Data Source
Figure 1~4
Figure 5~8
AI summary
An antenna having an inductor assembly including at least two conductors, which each define a conductor diameter Dc, and an electrically non-conductive carrier defining at least two lumens in which the at least two conductors are respectively located. The carrier maintains a conductor spacing S between the at least two conductors, and the inductor assembly defines at least one turn. The conductor spacing S and conductor diameter Dc together define a S/Dc ratio that ranges from about 0.5 to about 1.2.