Implant Pressure Sensor Housing for Low-Drift Differential Sensing
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Solution Overview
Problem
Existing implantable pressure sensors struggle to accurately measure differential pressures within the body due to environmental pressure changes, leading to incorrect readings and stress-induced drift, as they are either absolute sensors or have fixed connections between diaphragms, which are sensitive to stress and drift.
Innovation Solution
A housing with a chamber and membranes that hermetically seal the implant, allowing a sensor unit to measure differential pressure by separating the task of hermetic sealing from low-stress packaging, using foils to apply pressures to the sensor unit without direct contact, and optionally filled with incompressible liquids or casting compounds to ensure accurate pressure transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an absolute pressure sensor is used in an implant, then the sensor can measure the absolute pressure value, but the pressure changes caused by environmental conditions lead to incorrect readings and the pressure difference measurement becomes impossible
Solution Approach 1:
The implant is segmented into two separate pressure sensing chambers, each with its own membrane and pressure sensor. One chamber measures the absolute pressure (body pressure), while the other measures the environmental pressure. This segmentation allows the system to independently measure both pressures and calculate the pressure difference, resolving the contradiction between measuring absolute pressure and adapting to environmental pressure changes.
Solution Approach 2:
A hermetic seal acts as an intermediary between the external environment and the sensor chambers. The seal prevents direct contact between environmental contaminants and the internal pressure sensing mechanisms, while still allowing pressure transmission through the membranes. This intermediary protection enables accurate pressure measurement without direct environmental interference.
2Device complexity
If a fixed connection between the pressure sensor and diaphragms is used, then the sensor structure is simplified, but large stress and drift occur in the pressure sensor
Solution Approach 1:
The connection between the sensor and diaphragm is made locally adaptable through a stress-compensating interface design. Rather than a rigid fixed connection throughout, the interface allows for local stress relief and movement, accommodating thermal expansion and pressure-induced deformations without transmitting large stresses to the sensor element, thus maintaining reliability while keeping the overall structure simple.
3Measurement precision
If the sensor is directly connected to the body liquid, then the pressure measurement is direct, but the sensor is exposed to stress and drift from the body environment
Solution Approach 1:
A hermetic seal acts as an intermediary barrier between the body liquid environment and the sensor. The seal transmits pressure from the body liquid to the sensor while protecting the sensor from direct exposure to harmful body fluids, proteins, and cellular elements that could cause stress, drift, or failure. This allows direct pressure measurement without direct contact with harmful factors.
Solution Approach 2:
A thin, flexible membrane serves as both the pressure transmission interface and the protective barrier. The membrane is permeable to pressure waves and mechanical deformation but impermeable to body fluids and contaminants. This flexible shell allows the sensor to feel pressure changes in the body while remaining protected from the harsh biochemical environment.
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
Enables precise measurement of differential pressures within the body by isolating the sensor from environmental pressure fluctuations and stress, maintaining measurement accuracy and reducing drift, while allowing hermetic sealing without significant stress impact on the sensor.
Implementation Method 1
The sensor unit is configured to determine a pressure difference between a pressure at a first pressure side of the chamber and a pressure at a second pressure side chamber of the chamber
Implementation Method 2
optionally filled with incompressible liquids or casting compounds to ensure accurate pressure transfer
Data Source
Figure 1a
Figure 1b
Figure 1c
AI summary
An implant which comprises: a housing having a chamber; and a sensor unit; a first membrane covering the chamber at a first pressure side and a second membrane covering the chamber at a second pressure side; the chamber comprises pressure transfer means being in contact to the first and second membrane and to the sensor unit arranged within the chamber between the first and second membrane, wherein a sensor control unit arranged within the housing; wherein the sensor unit is configured to determine a pressure difference between a pressure at the first pressure side of the chamber and a pressure at the second pressure side chamber of the chamber.