Flexible Membrane Packaging for Implantable Pressure Sensors
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Solution Overview
Problem
Implantable medical devices face degradation due to corrosion from internal bodily fluids, leading to reduced effectiveness in monitoring and operational performance over time, especially for pressure sensors which experience sensitivity loss and offset drift.
Innovation Solution
A packaging method using a flexible, non-porous outer membrane made of biocompatible materials like silicone or parylene, combined with a hydrophobic liquid such as silicone oil, to create a hermetic and biocompatible package that reduces exposure to corrosive agents and maintains pressure sensitivity by minimizing pressure differential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid protective layer is deposited on the implantable medical device, then protection against corrosion is improved, but pressure sensing capability deteriorates due to pressure differential
Solution Approach 1:
The patent replaces solid protective layers with a flexible outer membrane that is thin and compliant, allowing it to deform with pressure changes while providing physical protection. This membrane maintains hermetic sealing without creating significant pressure differential, thus preserving pressure sensing capability while offering corrosion protection.
Solution Approach 2:
The patent introduces a hydrophobic liquid filling the interior space between the sensor and outer membrane. This liquid provides buoyancy support, distributes mechanical stresses, and maintains pressure equilibrium, preventing the formation of pressure differentials that would otherwise degrade pressure sensing accuracy while the device is implanted.
2Ease of operation
If the implantable medical device is exposed to internal bodily fluids, then operational functionality is maintained, but corrosion and biofouling occur leading to device failure
Solution Approach 1:
The flexible outer membrane creates a hermetic barrier that physically isolates the internal sensor components from corrosive bodily fluids and biofouling agents, while remaining flexible enough to allow the device to function normally in the implant environment.
Solution Approach 2:
The hydrophobic liquid acts as an intermediary substance between the sensor and the external environment. It provides a protective interface that prevents direct contact between corrosive fluids and sensitive components, while still allowing the sensor to detect pressure changes through the liquid medium.
3Reliability
If a rigid protective package is used, then protection against environmental conditions is improved, but pressure sensitivity is lost due to inability to expand and compression
Solution Approach 1:
The outer membrane is specifically designed to be flexible rather than rigid, allowing it to expand and compress in response to pressure changes. This flexibility enables the membrane to transmit pressure signals to the internal sensor while still providing environmental protection.
Solution Approach 2:
The packaging system is designed to be dynamic rather than static, with the flexible membrane and hydrophobic liquid working together to adapt to changing pressure conditions. This dynamic response allows the package to maintain pressure sensitivity while providing protection.
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 packaging significantly extends the operational life of implantable sensors, maintaining over 99% of original sensitivity for six weeks in harsh conditions, equivalent to twenty-one months in less extreme environments, while preventing biofouling and corrosion, thus ensuring accurate and prolonged monitoring.
Implementation Method 1
a hydrophobic liquid such as silicone oil
Implementation Method 2
The flexible outer membrane can include corrugations or a cuvature that facilitate expansion and compression
Data Source
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AI summary
An implantable medical device is described. In an example, the implantable medical device includes an electromechanical substrate and sensor, such as a pressure sensor, disposed on the substrate. At least a portion of the sensor is packaged via a liquid encapsulation. The packaging includes a shaped flexible outer membrane that surrounds at least the portion of the sensor. The packaging also includes a hydrophobic liquid disposed between at least the portion of the pressure sensor and the flexible outer membrane. The implantable medical device can be a part of a medical system used for monitoring medical conditions or performing medical operations based on the implantable medical device. Additionally, manufacturing methods are described for packaging the sensor in a liquid encapsulation.