Flexible Pressure Sensor With Foamed Polymer Isolation Layer
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Solution Overview
Problem
Existing flexible pressure sensors, particularly those using PVDF or ZnO, suffer from low sensitivity and instability, making them inadequate for high-sensitivity applications in wearable electronics due to complex fabrication processes and sensitivity issues related to surface smoothness and material characteristics.
Innovation Solution
A flexible pressure sensor comprising a sensor body with a first and second insulation layer of PET film, a conductive foamed polymer isolation layer, and silver nanowire conductivity layers, where the isolation layer is formed using a foamed polyurethane or polypropylene with specific additives and a foaming system, allowing for high sensitivity and stability through adjustable conductivity and uniform foam structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PVDF or ZnO materials are used for preparing piezoelectric thin films, then the sensor can realize pressure sensing function, but the sensitivity is not very high and cannot accurately identify very weak strain
Solution Approach 1:
The patent uses a foamed polymer isolation layer with controlled porosity (cell size 10-100 μm, porosity 30-70%) as the sensing element. The porous structure provides high surface area and mechanical compliance, enabling the layer to deform under pressure and modulate electrical conductivity between conductive electrodes, achieving high sensitivity for detecting very weak strain while maintaining stability.
Solution Approach 2:
The patent employs a composite structure combining conductive materials (silver nanowires, carbon nanotubes, or conductive polymers) with a foamed polymer isolation layer. This composite design leverages the electrical conductivity of the conductive material and the mechanical deformability of the porous foam, achieving both high sensitivity and stability in pressure sensing.
2Measurement precision
If two layers of conductive material with carbon nanotubes or graphene are assembled in staggered, then pressure sensing is achieved, but the process is complex and difficult to implement perfectly
Solution Approach 1:
The patent replaces the complex staggered assembly of two conductive layers with a single foamed polymer isolation layer containing dispersed conductive fillers. The porous structure inherently provides the necessary mechanical compliance and electrical modulation pathway, simplifying fabrication to a single coating and foaming process while achieving comparable or superior sensitivity.
Solution Approach 2:
The patent extracts the essential sensing function from the complex multi-layer staggered structure and implements it through a single foamed polymer layer with dispersed conductive fillers. This extraction simplifies the fabrication process by eliminating the need for precise alignment and assembly of multiple conductive layers, reducing manufacturing complexity while maintaining measurement sensitivity.
3Measurement precision
If the isolation layer is made with specific foam structure, then high sensitivity is achieved, but the fabrication process becomes more complex
Solution Approach 1:
The patent controls the foam structure parameters (cell size 10-100 μm, porosity 30-70%) during the foaming process to achieve optimal sensitivity. By adjusting foaming agents, crosslinking density, and curing conditions, the desired pore structure is obtained directly during manufacturing, maintaining fabrication simplicity while achieving high sensitivity through parameter optimization rather than post-processing.
Solution Approach 2:
The patent incorporates the foaming process into the initial isolation layer fabrication step, creating the porous structure beforehand before adding conductive fillers. This preliminary action integrates the complex foam structure creation into the base material preparation, avoiding subsequent complex assembly steps and maintaining ease of manufacture while achieving the required sensitivity.
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 sensor achieves high sensitivity and stability, enabling accurate detection of pressure with a flexible and scalable design suitable for wearable electronics, with adjustable sensitivity and testing range through the use of different foamed polymers and morphology adjustments.
Implementation Method 1
The isolation layer is a conductive foamed polymer with adjustable conductivity. When pressure is applied, the foam structure deforms, changing the electrical contact between the first and second conductive layers, enabling pressure detection through resistance change.
Implementation Method 2
The foamed polyurethane or polypropylene isolation layer with specific cell size and density deforms elastically under pressure, allowing reversible compression and expansion that modulates electrical conductivity for sensitive pressure detection.
Implementation Method 3
When pressure is applied to the sensor, the foamed isolation layer compresses, reducing its volume and increasing its density. This compression decreases the cell size and porosity, thereby modulating the electrical conductivity between conductive layers for pressure sensing.
Data Source
AI summary
The present invention relates to a sensor, particularly a flexible pressure sensor and a fabrication method thereof. The invention provides a flexible pressure sensor which comprises a sensor body and electrodes. The sensor body comprises a first insulation layer of PET film, a first conductivity layer, an isolation layer, a second conductive layer and a second insulation layer of PET film from top to bottom, respectively. The electrodes are made from the first conductive layer and the second conductive layer connected with external circuit through any electrical wire. The isolation layer is a semi-conductive foamed polymer with adjustable conductivity/resistance. Both of the first insulation layer of PET film and the second insulation layer of PET film have the thickness of 4.5-120 μm with the surface resistance value of 1013-14. In the process method of the invention, the isolation layer is a foamed polymer with adjustable conductivity. When pressed, the isolation layer deforms, which reduces the resistance between the two electrodes and increases the conductivity. High sensitivity of the isolation layer meets the requirement that a tiny deformation is enough to have a large change in resistance. Hence, the pressure can be detected by computer data processing upon the relationship between any external pressure and related resistance value.