Ceramic IMD Enclosure With Current-Canceling Metallization
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Solution Overview
Problem
Implantable medical devices (IMDs) with rechargeable power sources face challenges in suppressing induced currents and heat generation during high-frequency magnetic charging, which can damage patient tissue, especially when deeply implanted.
Innovation Solution
The use of a ceramic enclosure with a specific metallization geometry that cancels out induced currents by forming opposing currents within the conductive attachment mechanism, allowing efficient magnetic charging without tissue damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional titanium enclosures are used during high-frequency magnetic charging, then device hermetic sealing is achieved, but eddy currents are generated causing device heating and potential tissue damage
Solution Approach 1:
The patent changes the material parameter from conventional titanium to ceramic material for the enclosure. This material substitution fundamentally alters the electromagnetic properties, eliminating eddy current generation while maintaining hermetic sealing capability through specialized ceramic-to-ceramic or ceramic-to-metal seals.
Solution Approach 2:
The patent employs composite construction by combining ceramic enclosure material with metallic sealing components. The ceramic provides electromagnetic transparency during charging, while the metallic seals provide hermetic protection, creating a multi-material solution that resolves the contradiction between sealing reliability and eddy current suppression.
2Volume of moving object
If smaller IMDs with smaller recharge coils are used, then device miniaturization is achieved, but charging requires higher frequencies and magnitudes increasing induced currents
Solution Approach 1:
The patent changes the enclosure material parameter to ceramic, which has fundamentally different electromagnetic properties compared to conventional metals. This material parameter change allows the system to operate at higher frequencies and magnitudes required for miniaturized device charging without generating harmful eddy currents, thus resolving the contradiction between device miniaturization and induced current control.
3Productivity
If faster charging sessions are implemented, then patient recharge burden is reduced, but induced currents and heat generation increase
Solution Approach 1:
The patent changes the fundamental material parameter of the enclosure from conductive metal to non-conductive ceramic. This enables faster charging by allowing higher frequency and magnitude charging signals to be applied without generating eddy currents and excessive heat, thus resolving the contradiction between charging productivity and harmful effect generation.
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 enables fast and efficient recharging of IMDs, even when deeply implanted, by minimizing induced currents and heat generation, thus ensuring patient safety and device functionality.
Implementation Method 1
prevent eddy current generation and device heating during recharge, e.g., during fast and/or high frequencies charging sessions
Implementation Method 2
the arrangement of metallization on the ceramic enclosure may be configured to advantageously cancel out induced currents generated therein by the time-varying magnetic fields present during recharging
Data Source
AI summary
In some examples a medical device includes circuitry configured to at least one of sense a physiological parameter of a patient or deliver a therapy to the patient. The medical device may also include a housing configured to house the circuitry, wherein the housing includes a plurality of structural members and an attachment mechanism that joins the plurality of structural members. The attachment mechanism may be configured to suppress induced currents in the housing when the medical device is exposed to a time-varying magnetic field.