Flexible Titanium Membrane Housing for Implantable Pressure Sensors
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Solution Overview
Problem
Miniaturized implantable pressure sensor devices face challenges in maintaining accuracy due to temperature-induced volume changes in the incompressible liquid, leading to high pressure levels and potential damage to the sensor, especially in biocompatible titanium membranes with high elastic modulus, which results in significant temperature coefficients and errors in pressure readings.
Innovation Solution
The use of a housing predominantly made of a pressure transmitting membrane with reversible deformation capabilities, allowing the membrane to compensate for volume changes caused by temperature variations without increasing pressure, thereby minimizing tensile stress and maintaining surface area, even in non-circular geometries like elliptical cross-sections, to achieve a low temperature coefficient of pressure change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid titanium housing is used to protect the MEMS chip, then mechanical strength and biocompatibility are improved, but temperature-induced pressure measurement errors increase due to high elastic modulus preventing membrane deformation
Solution Approach 1:
The patent replaces the rigid titanium housing with a flexible titanium membrane housing that can reversibly deform under thermal expansion pressure. This flexible membrane structure allows the housing to expand and contract with temperature changes, preventing pressure buildup that would otherwise damage the MEMS chip or cause measurement errors. The membrane maintains mechanical strength while providing the necessary flexibility to accommodate thermal effects.
Solution Approach 2:
The patent changes the physical parameters of the housing by reducing its thickness from conventional >100 μm to 5-50 μm, and by designing it with specific geometric features (elliptical cross-section, corrugations) that enable reversible deformation. This parameter change transforms the housing from a rigid structure to a flexible one that can dynamically adapt to temperature-induced volume changes in the incompressible liquid.
2Volume of moving object
If the housing thickness is reduced to miniaturize the device, then device size is improved, but structural stability and pressure transmission capability deteriorate
Solution Approach 1:
The thin-walled flexible membrane housing (5-50 μm thickness) replaces conventional thick rigid housings, enabling miniaturization while maintaining structural integrity through flexibility. The membrane structure can reversibly deform to accommodate internal pressure changes, preventing structural failure despite the reduced thickness.
Solution Approach 2:
The patent employs an elliptical cross-section geometry for the housing that can transform into a circular cross-section under pressure. This curved geometric design distributes stress more effectively throughout the thin membrane structure, enhancing structural stability despite the reduced wall thickness and miniaturized dimensions.
3Ease of manufacture
If a conventional rigid housing with a membrane window is used, then manufacturing simplicity is improved, but temperature coefficient of pressure change increases due to inability to compensate for liquid volume expansion
Solution Approach 1:
The flexible membrane housing serves multiple functions simultaneously: it provides mechanical protection for the MEMS chip, transmits pressure from the incompressible liquid to the sensor, and compensates for thermal expansion of the liquid through reversible deformation. This multi-functionality eliminates the need for a separate membrane window while improving temperature compensation performance.
Solution Approach 2:
The patent changes the geometric parameters of the housing by designing it with an elliptical cross-section that can transform into a circular cross-section under pressure, and by incorporating corrugations or other deformation features. These parameter changes enable the housing to reversibly deform and accommodate thermal volume expansion, significantly reducing the temperature coefficient of pressure change.
4Reliability
If titanium membrane is used for biocompatibility, then biocompatibility is improved, but membrane flexibility deteriorates due to high elastic modulus
Solution Approach 1:
The patent uses a thin-walled (5-50 μm) titanium membrane structure that leverages the material's high strength-to-weight ratio. The reduced thickness compensates for titanium's high elastic modulus, enabling the membrane to flex and deform reversibly under thermal pressure while maintaining biocompatibility. The thin film structure achieves flexibility that would be impossible with thicker titanium sections.
Solution Approach 2:
The elliptical cross-section geometry with curvature radii of 0.5-2 mm creates stress distribution patterns that enhance the membrane's ability to deform flexibly. The curved geometry allows the titanium membrane to bend and transform from elliptical to circular cross-section under pressure, improving flexibility while maintaining the biocompatible titanium material.
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
This approach significantly reduces temperature-induced pressure measurement errors, achieving a temperature coefficient of ΔP/ΔT of 10 mbar/K or less, ensuring accurate pressure readings and tolerance to high volume increases during thermal sterilization, while maintaining biocompatibility and stability.
Implementation Method 1
compensate for changes of the volume of the incompressible liquid in the housing caused by temperature variations during manufacture and operation
Implementation Method 2
one or more regions which are reversibly deformable while maintaining the size of the membrane's surface area when the housing's interior volume is changed
Data Source
AI summary
An implantable pressure sensor device (100) has a housing (10) which is at least partially made of a pressure transmitting membrane (20), and which includes one or more regions which can reversibly deform while maintaining the surface area of the membrane (20) when the internal volume of the housing (10) is changed. The housing (10) has a non-circular cross-section which can deform to a more circular shape when pressure in the internal volume increases. An inner housing is preferably situated within the housing, with its exterior spaced from the interior of the housing, and has its inner volume in fluid communication with the space between the housing and inner housing.