Spacer-Based Thermal Management for Wireless Charging IMDs
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Solution Overview
Problem
Implantable medical devices (IMDs) experience unwanted heat generation during wireless charging due to eddy currents, which can cause discomfort or tissue damage without effective heat dissipation.
Innovation Solution
An external device with a transceiver and processing circuit that communicates with a wireless charger to obtain power parameters, estimates temperature ranges, and recommends the use of spacers to increase the charging path length, thereby reducing heat accumulation by positioning spacers between the charger and the patient's skin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wireless charging is used to charge the IMD, then the battery can be recharged without surgery, but heat is generated due to eddy currents in metal components
Solution Approach 1:
The patent introduces a non-metallic spacer as an intermediary component placed between the charger and the IMD. This spacer acts as a mediator that prevents direct thermal coupling while maintaining electromagnetic coupling for wireless charging, thus reducing heat transfer to the IMD and surrounding tissues.
Solution Approach 2:
The patent segments the charging interface by introducing a separate spacer component that is distinct from both the charger and the IMD. This segmentation allows the spacer to specifically address the heat transfer problem without interfering with the wireless charging function, enabling the charger and IMD to remain in their original configurations.
2Productivity
If the charging path is minimized for efficient charging, then charging speed is improved, but heat accumulation increases
Solution Approach 1:
The non-metallic spacer serves as a thermal intermediary that decouples the thermal pathways while preserving the electromagnetic charging pathway. This allows the charging path to remain minimized for efficient power transfer, while the spacer blocks the direct thermal conduction path that would otherwise cause heat accumulation in the IMD.
3Strength
If metal components are used in the IMD for structural integrity, then device strength is improved, but eddy currents are generated during wireless charging
Solution Approach 1:
The spacer acts as a thermal and electromagnetic intermediary that reduces the coupling between the external charger's magnetic field and the metal components of the IMD. By placing the spacer between the charger and the IMD, it attenuates the eddy current generation in metal components while preserving the necessary structural integrity of the IMD.
4Device complexity
If no heat dissipation path is provided, then device complexity is reduced, but heat accumulates locally causing tissue damage
Solution Approach 1:
The non-metallic spacer provides a passive heat management solution by acting as a thermal barrier between the charger and the IMD. This intermediary approach reduces heat accumulation without requiring active cooling systems or complex heat dissipation mechanisms, thus maintaining low device complexity while preventing tissue damage.
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 effectively reduces heat buildup in IMDs during charging, ensuring patient safety and comfort by maintaining temperatures within safe limits, even when charging paths are minimized.
Implementation Method 1
The external charger device includes an inductive coil that enables power to be wirelessly transferred, through the patient's skin, from the charger device to an inductive coil in the IMD to charge the rechargeable battery.
Implementation Method 2
The IMD may contain metal for its casing and when using wireless charging, it generates eddy currents on metal components in the charging path.
Data Source
AI summary
A wireless charger device is configured to charge an implantable medical device (IMD). A patient controller obtains one or more power parameters from the charger device during charging of the IMD. The patient controller estimates a temperature range of the IMD using the one or more power parameters from the charger device and compares to a heating threshold. The patient controller then determines whether one or more spacers are recommended in response to the comparison. The one or more spacers are removably attached to the wireless charger device and are configured to lay in a position between the wireless charger device and a patient's skin to increase a charging path.