Porous Siloxane Pressure Sensing Layer for Low-Pressure Sensitivity
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Solution Overview
Problem
Existing pressure sensors, particularly piezocapacitive sensors, face challenges in achieving high sensitivity and reproducibility, especially in low pressure regions, often requiring complex and expensive fabrication processes.
Innovation Solution
A pressure sensing layer comprising a porous siloxane polymer matrix with a closed porosity volume fraction and conductive or semiconductive filler, where the filler is predominantly present in the closed porosity, enhancing capacitance changes under pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If micro- or nano-structures are suggested in piezocapacitive sensors to improve sensitivity in low pressure range, then sensitivity is improved, but fabrication process becomes complex and expensive
Solution Approach 1:
The patent employs a porous polymer matrix material as the dielectric layer, where the porous structure is formed by incorporating porous particles (such as porous silica, porous polymer beads, or hollow microcapsules) into the polymer matrix. This porous structure increases the effective surface area and enhances capacitance change under pressure, improving sensitivity in the low pressure range without requiring complex micro- or nano-structure fabrication processes. The porous particles are simply mixed into the polymer solution before curing, making the fabrication process straightforward and cost-effective.
2Reliability
If piezocapacitive sensors are used instead of piezoresistive devices, then power consumption is reduced and reproducibility is improved, but sensitivity in low pressure regions is insufficient
Solution Approach 1:
The patent creates a composite dielectric material by combining a polymer matrix (such as PDMS, polyurethane, or epoxy) with porous particles (such as porous silica, porous polymer beads, or hollow microcapsules). This composite structure leverages the electrical insulation and flexibility of the polymer while incorporating the high surface area and compressibility of the porous particles. The result is a material that maintains the low power consumption and good reproducibility of piezocapacitive sensors while significantly enhancing their sensitivity in the low pressure range through the porous structure's ability to undergo large volume changes under small pressures.
3Reliability
If conductive filler is distributed throughout the porous matrix, then conductivity is improved, but capacitance change under pressure is reduced
Solution Approach 1:
The patent applies local quality by concentrating the conductive filler specifically at the interfaces between the porous particles and the polymer matrix, rather than distributing it uniformly throughout the entire matrix. This localized placement ensures that the conductive filler is positioned where the electric field is most concentrated during compression, maximizing the capacitance change signal. The conductive filler at the interfaces enhances charge separation and accumulation effects, improving both conductivity and capacitance change simultaneously, whereas uniform distribution would shield the electric field and reduce the sensing signal.
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
The solution provides high sensitivity and good reproducibility in low pressure ranges, with improved capacitance changes due to the localized conductive filler, allowing for efficient pressure detection.
Implementation Method 1
piezocapacitive sensors on the other hand make use of the capacitance change occurring in reaction to the application of pressure
Implementation Method 2
The magnitude of the capacitance change is determined by the change in relative permittivity (dielectric constant) and/or in the change in the thickness of a dielectric layer and/or in the change in the surface area of an electrode
Data Source
AI summary
Pressure sensing layers, devices comprising same, pressure sensing monitors and composite materials comprising a) a porous matrix material comprising a siloxane polymer, comprising a closed porosity volume fraction, and, optionally, an open porosity volume fraction, and b) a conductive or semiconductive filler substantially present in the closed porosity volume fraction of the porous matrix material a), and films, coated substrates and multilayer structures comprising the composite material and the use thereof in pressure sensing devices.