Implantable Capacitive Pressure Sensor Parasitic Capacitance Reduction
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Solution Overview
Problem
Capacitive pressure sensors implanted in vivo face significant parasitic capacitance issues, leading to reduced sensitivity when in close contact with body tissues and fluids, which existing technologies have not effectively addressed.
Innovation Solution
The capacitive pressure sensor apparatus is designed with a diaphragm electrode grounded and isolated from the signal electrode using an insulating material, such as glass, to reduce parasitic capacitance effects, with the signal electrode being electrically isolated and shielded from electrical activity in the body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the capacitive pressure sensor is placed in close contact with body tissues and fluids for in-vivo measurement, then the sensor can detect physiological pressure, but parasitic capacitance increases causing sensitivity to drop drastically
Solution Approach 1:
An insulating material layer is introduced between the sensor electrode and the body tissue/fluid environment. This intermediary layer electrically isolates the sensor from the conductive body environment, reducing parasitic capacitance while still allowing the sensor to detect pressure changes through mechanical coupling of the diaphragm structure.
Solution Approach 2:
A flexible diaphragm structure is used as the sensing element, which can deform in response to pressure changes. The diaphragm is made of a thin, flexible material that transmits mechanical pressure while maintaining electrical isolation when combined with the insulating layer, enabling pressure sensing without direct electrical contact with body tissues.
2Device complexity
If the signal electrode is directly exposed to the body environment for signal detection, then the sensor structure remains simple, but electrical activity in the body causes increased parasitic capacitance effects
Solution Approach 1:
The insulating material serves as a mediator that blocks electrical interference from body activities while still allowing mechanical pressure transmission. This layer electrically isolates the signal electrode from the noisy body environment without requiring complex shielding or filtering structures.
Solution Approach 2:
The electrical interference problem is extracted and isolated from the sensing function. By separating the electrical signal path from the conductive body environment through the insulating layer, the harmful electrical noise is effectively removed from the signal detection path while preserving the pressure sensing 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
This configuration significantly reduces parasitic capacitance, enhancing the sensitivity and accuracy of the pressure sensor by isolating the signal electrode and shielding it from body electrical noise.
Implementation Method 1
Small capacitive pressure sensors may encounter parasitic capacitive problems, e.g., sensitivity of such pressure sensors drops drastically with the addition of parasitic capacitance
Implementation Method 2
the diaphragm electrode is grounded when the implantable pressure sensor apparatus is implanted in the body to shield the signal electrode from electrical activity in the body
Data Source
AI summary
An implantable capacitive pressure sensor apparatus and method for making such an apparatus includes a first pressure sensor portion and a second pressure sensor portion. The first pressure sensor portion includes a diaphragm electrode connectable to ground (e.g., the diaphragm electrode being positioned in close proximity to the body when implanted therein such that the diaphragm electrode is deformable in response to pressure applied thereto by the body). The second pressure sensor portion includes a signal electrode (e.g., wherein the first pressure sensor portion and the second pressure sensor portion are coupled such that a gap is provided between the diaphragm electrode and the signal electrode) and an insulator material. The signal electrode is provided on and in direct contact with the insulator material to electrically isolate the signal electrode such that parasitic capacitance effects on the signal electrode are reduced.