MEMS Pressure Sensor Packaging for Cardiac Implants
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Solution Overview
Problem
Current medical implant devices for pressure sensing in cardiac anatomy face challenges due to environmental conditions and accessibility issues, requiring specialized packaging that ensures biocompatibility and effective data communication while minimizing invasive methods.
Innovation Solution
The development of implantable pressure sensor devices featuring a microelectromechanical systems (MEMS) pressure sensor mounted on a substrate, covered with a transduction medium such as parylene, silicone, or epoxy, and a biocompatibility layer comprising metal and polymer films, which are applied over the sensor and electrical connections to enhance biocompatibility and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pressure sensor device is implanted in cardiac anatomy, then pressure measurements can be obtained, but biocompatibility issues and environmental challenges arise
Solution Approach 1:
The patent applies composite materials by creating a multi-layer packaging structure consisting of a biocompatibility layer (e.g., titanium nitride, diamond-like carbon), a transduction medium layer (e.g., parylene, silicone), and an optional hermetic seal layer. Each layer serves specific functions: the biocompatibility layer prevents tissue rejection and corrosion, the transduction medium provides electrical insulation and mechanical protection while allowing pressure transmission, and the hermetic seal prevents fluid ingress. This composite structure resolves the contradiction by combining materials with complementary properties to simultaneously achieve biocompatibility and environmental protection.
Solution Approach 2:
The patent employs flexible shells and thin films through the use of thin-film deposition techniques to create the biocompatibility layer and transduction medium. The biocompatibility layer is deposited as a thin film (e.g., 1-10 micrometers) that conforms to the sensor substrate while providing protective functions. The transduction medium is applied as a flexible coating that maintains pressure transmission while protecting underlying components. These thin flexible layers resolve the contradiction by providing protection without adding significant bulk or rigidity that would interfere with cardiac function.
2Reliability
If packaging layers are added to protect the sensor, then biocompatibility is enhanced, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the packaging system into distinct functional layers: a biocompatibility layer for tissue interface protection, a transduction medium layer for pressure transmission and electrical insulation, and optionally a hermetic seal layer for fluid protection. Each layer is optimized for its specific function and can be independently selected and applied. This segmented approach resolves the contradiction by organizing complexity into manageable, function-specific modules rather than a monolithic structure, making the overall system more understandable and manufacturable.
Solution Approach 2:
The patent achieves universality by designing the transduction medium layer to perform multiple functions simultaneously: it provides electrical insulation for bondwires and circuitry, mechanical protection for the sensor elements, pressure transmission to the sensing diaphragm, and a substrate for the biocompatibility layer. The biocompatibility layer itself serves multiple roles: preventing tissue rejection, providing corrosion resistance, and maintaining a stable interface for long-term implantation. This multi-functionality reduces the need for additional separate components, thereby managing complexity while enhancing reliability.
3Reliability
If bondwires are used for electrical coupling, then electrical connection is achieved, but exposure to bodily fluids causes degradation
Solution Approach 1:
The patent applies the intermediary principle by introducing the transduction medium as a mediating layer between the bondwires and the bodily fluid environment. This transduction medium (e.g., parylene, silicone, epoxy) serves as a barrier that prevents direct contact between conductive bondwires and conductive bodily fluids, eliminating galvanic corrosion and short-circuit risks. Simultaneously, the transduction medium is designed to be acoustically and mechanically coupled to allow pressure transmission. This intermediary layer resolves the contradiction by providing electrical isolation without compromising the electrical connection functionality or pressure sensing capability.
4Volume of moving object
If the sensor is made compact for implantation, then accessibility is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies mechanics substitution by replacing traditional mechanical packaging methods (such as encapsulation in rigid housings, sealing with adhesives, or mechanical assembly of multiple components) with thin-film deposition processes. The biocompatibility layer and transduction medium are applied using vapor deposition, chemical vapor deposition, or spin-coating techniques that conformally coat the sensor substrate and underlying structures. This substitution of mechanical assembly with deposition processes resolves the contradiction by enabling precise, uniform coating at micrometer and sub-micrometer thicknesses that is incompatible with conventional mechanical manufacturing, thereby achieving compact dimensions with appropriate manufacturing precision.
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 solution enables reliable, long-term implantation of pressure sensors in cardiac environments, providing accurate pressure measurements and facilitating wireless data communication, thus improving monitoring and treatment of cardiac conditions like congestive heart failure.
Implementation Method 1
a transduction medium applied over the pressure sensor device
Implementation Method 2
a biocompatibility layer applied over the transduction medium
Implementation Method 3
an oxide layer formed on a surface of the biocompatibility layer
Implementation Method 4
An organic film may be bonded to the oxide layer. For example, the organic film may be covalently bonded to the oxide layer
Implementation Method 5
microelectromechanical systems (MEMS) pressure sensor device
Data Source
AI summary
An implantable sensor device includes a sensor-support substrate, a microelectromechanical systems (MEMS) pressure sensor device mounted to the sensor-support substrate, a transduction medium applied over the pressure sensor device, and a biocompatibility layer applied over the transduction medium