Transparent Ceramic Encapsulation for Active Implantable Medical Devices
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Solution Overview
Problem
Active implantable medical devices (AIMDs) face challenges with encapsulation materials that are not transparent to RF and IR wavelengths, are not MRI-friendly, and have durability and moisture resistance issues, limiting their functionality and medical applications.
Innovation Solution
The development of an AIMD with a transparent ceramic encapsulation housing that allows transmission of electromagnetic radiation within specific wavelengths, ensuring hermeticity and mechanical resistance, using fused silica or similar materials for the components and integrating optical elements for energy transfer and monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If titanium encapsulation is used for mechanical properties and biocompatibility, then mechanical strength and biocompatibility are improved, but transmission of RF, visible and IR wavelengths is blocked and MRI compatibility is lost
Solution Approach 1:
The encapsulation uses a composite structure combining titanium alloy for mechanical strength and biocompatibility with a transparent window material (such as sapphire, glass, or polymer) that allows transmission of optical wavelengths. This composite approach resolves the contradiction by integrating materials with complementary properties: titanium provides structural integrity while the transparent window enables RF, visible, and IR transmission and MRI compatibility.
2Strength
If ceramic encapsulation is used for durability, then mechanical resistance is improved, but transparency to visible and IR lights is lost
Solution Approach 1:
The encapsulation combines ceramic material (providing mechanical resistance and durability) with a transparent window material (such as sapphire, glass, or specific polymers) that transmits visible and IR light. The ceramic body maintains structural integrity and protection against body fluids, while the transparent window enables optical communication and sensing functions.
3Ease of manufacture
If polymer encapsulation is used for optical transparency, then transmission of light wavelengths is improved, but durability and moisture resistance are reduced
Solution Approach 1:
The encapsulation uses a hybrid structure where the main body is made of moisture-resistant material (titanium alloy or ceramic) while specific window portions are made of transparent polymer or coated with transparent protective layers. This allows the polymer to provide optical transparency for light transmission while the metal or ceramic body ensures durability and moisture resistance in the implant environment.
4Volume of stationary object
If larger encapsulation volume is used to house electronic circuitry, then device functionality is improved, but implantation complexity increases
Solution Approach 1:
The device is divided into separate functional modules: the encapsulation housing containing electronic circuitry, the tissue coupling unit with electrodes or optrode, and the lead connecting them. This segmentation allows the encapsulation to be optimized for housing electronics while the tissue coupling unit is optimized for tissue interaction, simplifying the overall implantation process and reducing complexity.
Solution Approach 2:
The tissue coupling unit is extracted as a separate component from the encapsulation, connected via a lead. This allows the encapsulation to focus on providing a protected environment for electronics while the tissue coupling unit handles the complex interaction with biological tissue, thereby simplifying the encapsulation design and implantation procedure.
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 AIMDs with larger dimensions for housing electronic circuitry, improved moisture resistance, and cost-effective production, allowing for enhanced functionality including energy transfer and biomarker monitoring while maintaining biocompatibility and safety for MRI environments.
Implementation Method 1
The encapsulation comprises a housing defining an inner volume perfectly sealed from an outer environment and has transparent walls allowing transmission of light energy therethrough
Implementation Method 2
IPG producing optical energy transferred through an optical fibre to a photovoltaic cell comprised in the tissue coupling unit for conversion of optical energy into electric energy for feeding electrode contacts of the tissue coupling unit
Data Source
AI summary
An active implantable medical device includes an encapsulation (1) defining an inner space sealingly separated from an outer environment by walls transparent to a given wavelength range. The walls have a first main wall (1a) and a second main wall (1b) facing one another and separated from one another by an inner height (Hi) of the inner space. An encapsulation includes a housing formed by a first component (2) and a second component (3) both made of a single material and hermetically joined to one another along a single interface (23) to define the inner space hermetically sealed by the walls from the outer environment. An inner space contains an electronic, and facing a wall of the encapsulation. wherein joining of the first component and second components (2, 3) is carried out by welding without addition of a third material, the inner space has a volume (Vi) of at least 2 cm3.