Grooved Metal Case for Implantable Device Eddy Current Reduction

Solution Overview

Problem

Implantable devices with metal cases experience energy wastage and tissue heating due to eddy currents during inductive recharging, prolonging charging time and posing safety risks.

Innovation Solution

A conductive case with grooves oriented perpendicular to anticipated eddy current flow is used to encase the rechargeable battery and inductive recharging coil, reducing eddy current formation and heat generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a metal case is used to encase the rechargeable battery and control circuitry, then the device provides structural protection and electromagnetic shielding, but eddy currents are generated during inductive recharging causing energy wastage and tissue heating

Engineering Contradiction:

Improvestructural protectionVSAvoidenergy wastage

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The metal case is segmented by introducing grooves that divide the continuous metal surface into separate regions. These grooves are oriented perpendicular to the anticipated eddy current flow direction, effectively breaking the eddy current paths into smaller segments that reduce overall current magnitude and energy loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The grooves act as intermediary non-conductive elements within the metal case structure. These grooves serve as mediators that interrupt the eddy current flow without compromising the overall structural integrity or electromagnetic shielding capabilities of the metal case.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a metal case is used to encase the rechargeable battery and control circuitry, then the device provides structural protection and electromagnetic shielding, but surrounding tissue heating occurs during inductive recharging

Engineering Contradiction:

Improvestructural protectionVSAvoidtissue heating

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The metal case is segmented by introducing grooves that divide the continuous metal surface into separate regions. These grooves are oriented perpendicular to the anticipated eddy current flow direction, effectively breaking the eddy current paths into smaller segments that reduce overall current magnitude and energy loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The grooves, which initially appear as structural modifications, convert the harmful eddy current effect into a beneficial reduction of tissue heating. By strategically placing grooves perpendicular to eddy current flow, the design transforms potential energy loss into a mechanism that protects surrounding tissue from excessive heating.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If a metal case is used to encase the rechargeable battery and control circuitry, then the device provides structural protection and electromagnetic shielding, but recharging time is prolonged due to energy loss

Engineering Contradiction:

Improvestructural protectionVSAvoidrecharging speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The metal case is segmented by introducing grooves that divide the continuous metal surface into separate regions. These grooves are oriented perpendicular to the anticipated eddy current flow direction, effectively breaking the eddy current paths into smaller segments that reduce overall current magnitude and energy loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The electrical resistance parameter of the metal case is changed by introducing grooves that increase the effective resistance to eddy current flow. This parameter change reduces the magnitude of eddy currents generated during inductive recharging, thereby improving recharging efficiency and reducing charging time.

Inventive Principle:

Principle #35Parameter changes

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 minimizes eddy current-induced energy wastage and tissue heating, enhancing the efficiency and safety of inductive recharging for implantable devices.

Implementation Method 1

an inductive recharging coil, coupled to a rechargeable battery and control circuitry, adapted to provide recharging current to the rechargeable battery in response to a proximate electromagnetic field

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

the metal case can contribute to the formation of eddy currents during inductive recharging. These eddy currents waste energy (which lengthens the time required for recharging) and also cause heating of surrounding tissue

Methodology Applied

Scientific EffectEddy currents: Eddy Currents

Data Source

PatentUS9531195B2Inductively rechargeable implantable device with reduced eddy currents

Publication Date: 2016.12.27 LIVANOVA USA INC

AI summary

A case for an implantable medical device includes a metal case portion, having an inside and an outside, configured to attach to at least one other case portion to define a biocompatible case for the implantable medical device. The metal case portion has a plurality of grooves disposed on at least one of the inside and the outside, the grooves being oriented substantially perpendicular to an expected direction of eddy currents produced by an inductive recharging coil in proximity thereto.