Implant Pressure Sensor With Membranes for 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 inaccuracies in absolute pressure measurements, and are prone to stress-induced drift when hermetically sealed.
Innovation Solution
A differential pressure sensor design featuring a housing with a chamber separated by membranes and a sensor unit that measures relative pressure differences between two sides, using pressure transfer means and foils to isolate the sensor from environmental stress, allowing for hermetic sealing without significant stress impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an absolute pressure sensor is used in the implant, then the sensor can measure pressure, but environmental pressure changes cause measurement inaccuracies
Solution Approach 1:
The pressure measurement function is segmented into two independent absolute pressure sensors, each measuring pressure on one side of the membrane. The differential pressure is then calculated by subtracting the two measurements, isolating the local pressure difference from environmental pressure changes that affect both sensors equally.
Solution Approach 2:
A flexible membrane acts as an intermediary between the two pressure environments. It transmits pressure from both sides to the sensor chamber while maintaining hermetic sealing, allowing the sensors to measure pressures indirectly without being exposed to the body environment directly.
2Reliability
If the sensor is hermetically sealed in a fixed connection, then the sensor is protected, but stress and drift occur in the pressure sensor
Solution Approach 1:
The hermetic sealing is made dynamic through the flexible membrane instead of a fixed rigid connection. The membrane can deform elastically under pressure differences, absorbing stress without transmitting it to the sensor, thereby maintaining both protection and measurement accuracy over time.
Solution Approach 2:
A flexible membrane is used instead of rigid fixed connections for hermetic sealing. The membrane's elasticity allows it to accommodate pressure changes without creating stress concentrations that would cause sensor drift, while still providing effective hermetic sealing of the sensor chamber.
3Measurement precision
If a differential pressure sensor with two diaphragms is used, then differential pressure can be measured, but large stress is applied to the sensor
Solution Approach 1:
A flexible membrane serves as an intermediary that distributes the differential pressure load across its surface rather than concentrating it on the sensor. The membrane deforms to equalize pressures, reducing the stress transmitted to the sensor while still enabling accurate differential pressure measurement.
Solution Approach 2:
The flexible membrane acts as a stress-distributing element between the two pressure sources. Its ability to deform elastically allows it to bear the mechanical load of pressure differences, protecting the sensor from large stresses while maintaining measurement capability.
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 accurate measurement of differential pressures within the body by isolating the sensor from environmental changes and reducing stress-induced errors, ensuring precise pressure difference readings.
Implementation Method 1
a first pressure from a first pressure side and a second pressure from a second pressure side can be applied to the sensor
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.