Cochlear Implant Magnet Assembly with Damping Liquid for MRI Alignment
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Solution Overview
Problem
Conventional cochlear implants with MRI-compatible magnet assemblies face issues such as demagnetization and dislocation due to misalignment with MRI magnetic fields, and hermetically sealed damping liquids boil during welding, affecting the weld quality.
Innovation Solution
A method of assembling a magnet assembly involving positioning elongate diametrically magnetized magnets within a case, introducing damping liquid through a port, and sealing it with a plug after welding, ensuring the liquid is not adjacent to the weld area, and using a damping liquid dispenser to prevent boiling during welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If damping liquid is introduced into the case before welding the case members, then the case can be hermetically sealed, but the damping liquid boils during welding and adversely affects weld quality
Solution Approach 1:
The case members are welded together first to form a sealed chamber, and then the damping liquid is introduced through a port after welding. This reverses the conventional sequence, ensuring the liquid is not present during welding and thus cannot boil or affect weld quality, while still achieving hermetic sealing of the final assembly
Solution Approach 2:
The assembly process is divided into distinct stages: first welding the case members together to form the housing structure, then separately introducing the damping liquid through a port. This segmentation allows each operation to be optimized independently, avoiding the conflict between having liquid present during welding versus achieving hermetic sealing
2Ease of manufacture
If conventional disk-shaped magnets with axial magnetization are used, then the magnet assembly is simple to manufacture, but the magnets are not compatible with MRI systems and must be surgically removed and replaced
Solution Approach 1:
The magnet geometry is changed from conventional disk-shaped with axial magnetization to elongate diametrically magnetized magnets where the length is greater than the diameter. The magnetization direction is changed from axial to diametric, which fundamentally alters the magnetic field characteristics to be compatible with MRI systems while maintaining manufacturability through standard magnetization techniques
3Reliability
If diametrically magnetized disk-shaped magnets are used, then MRI compatibility is improved, but the magnets may still be demagnetized or dislodged when the MRI magnetic field is misaligned by at least 30° or more from the N-S direction
Solution Approach 1:
The magnet assembly is made rotatable relative to the cochlear implant housing, allowing the magnets to dynamically adjust their orientation in response to the MRI magnetic field direction. This dynamic adjustment ensures the magnets remain properly aligned regardless of the MRI field angle, eliminating torque and demagnetization risks that occur with fixed orientations when misaligned by 30° or more
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 ensures the magnets remain aligned with MRI fields, reduces torque, and maintains weld integrity by preventing boiling, thus enhancing the reliability and safety of cochlear implants.
Implementation Method 1
a damping liquid, e.g., a biocompatible oil, inside the magnet assembly case that acts as a physical dampening medium between the moving internal components
Implementation Method 2
The magnets can align with three-dimensional (3D) MRI magnetic fields, regardless of field direction, which results in very low amounts of torque on the magnets
Implementation Method 3
The case is hermetically sealed by welding (e.g., laser welding) the case cover to the case base around the perimeter of the case
Data Source
AI summary
Magnet assemblies including a case, a plurality of elongate diametrically magnetized magnets within the case, and damping liquid within the case, and methods of assembling such magnet assemblies.