Ferromagnetic Coil Coupling Lens for Implant Wireless Charging
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Solution Overview
Problem
Current wireless charging systems for medical implants suffer from inefficient energy transfer and significant self-heating issues due to suboptimal magnetic coupling, leading to increased charging time and risk of tissue damage.
Innovation Solution
A coil arrangement featuring a planar ring-shaped winding with a ferromagnetic coil coupling lens that shapes the magnetic field to enhance coupling efficiency and minimize self-heating, using multiple lens surfaces to redirect magnetic field lines and increase the coupling factor between external and internal coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large coil diameter is used to achieve optimal magnetic coupling, then the coupling factor is improved, but the implant size becomes too large for most implants
Solution Approach 1:
A ferromagnetic material is introduced as an intermediary between the coils to concentrate and guide magnetic flux, enabling optimal coupling with smaller coil diameters. The ferromagnetic material acts as a flux concentrator that bridges the gap between transmitter and receiver coils, allowing high coupling factors without requiring large coil areas.
Solution Approach 2:
The magnetic permeability parameter is changed by introducing ferromagnetic material with high relative permeability (μr) between the coils. This parameter change concentrates magnetic flux and enhances coupling efficiency, allowing smaller coil dimensions while maintaining or improving the coupling factor compared to air-core configurations.
2Productivity
If high charging power is used to reduce charging time, then productivity is improved, but self-heating of adjacent tissues increases
Solution Approach 1:
The ferromagnetic material, which could potentially cause heating, is instead used to concentrate and direct magnetic flux efficiently through the desired path. By guiding flux through high-permeability material rather than through surrounding tissues, the system converts potential harmful heating into beneficial flux concentration, enabling high power transfer with reduced tissue heating.
Solution Approach 2:
The ferromagnetic material serves as a thermal and magnetic intermediary that channels energy through controlled paths. It mediates between the coils and surrounding tissues, directing magnetic flux away from sensitive areas and reducing eddy current losses in adjacent tissues, thereby enabling faster charging with minimal self-heating.
3Ease of operation
If the external charging device is made compact and portable, then ease of operation is improved, but energy transfer efficiency decreases
Solution Approach 1:
The introduction of ferromagnetic material changes the magnetic circuit parameters, increasing mutual inductance and coupling coefficient between coils. This parameter enhancement allows compact coil designs to achieve energy transfer efficiencies comparable to or exceeding larger traditional systems, enabling portable charger design without sacrificing efficiency.
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 solution optimizes power transfer efficiency, reduces self-heating, and allows for a more compact and portable charging device, decreasing the risk of tissue damage and improving patient comfort by minimizing the necessary magnetic field strength and power loss.
Implementation Method 1
A coil coupling lens of magnetic conductive material (e.g., ferromagnetic material such as soft iron) has multiple lens surfaces and is adapted to shape the magnetic field component to increase the coupling factor
Implementation Method 2
minimize self-heating of adjacent tissues due to the magnetic field component
Implementation Method 3
The coils are magnetically coupled by the inductive link with a power transfer an alternating magnetic field produced by the external coil, where some fraction k (coupling factor) of that field penetrates the skin to the implant coil which induces a voltage that drives current for the implant electronics
Data Source
AI summary
A coil arrangement is described for an implantable medical system. A coil winding has a planar ring shape winding that encloses a coil interior area. The coil winding is adapted for placement parallel to a corresponding partner coil for communication of an implant link signal having an associated magnetic field component characterized by a coupling factor k representing fractional amount of magnetic field coupling between the coils. A coil coupling lens of magnetic conductive material has multiple lens surfaces and is adapted to shape the magnetic field component to increase the coupling factor and minimize self-heating of adjacent tissues due to the magnetic field component. The lens surfaces include: i. an inner lens surface lying substantially parallel to the plane of the ring shape winding and having an inner lens surface perimeter enclosed within the coil interior area, ii. an outer lens surface lying substantially parallel to the inner lens surface and having an outer lens surface perimeter greater than the inner lens surface perimeter, and iii. at least one lens connecting surface connecting the inner lens surface perimeter and the outer lens surface perimeter.