Foam Sheet Dielectric Constant Increase for Capacitive Sensor Sensitivity
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Solution Overview
Problem
Existing foams used in electrostatic capacitance sensors lack sufficient flexibility and exhibit low electrostatic capacitance, limiting their sensitivity due to insufficient dielectric constant changes with thickness variations.
Innovation Solution
A foam sheet with a pressure-sensitive adhesive layer is developed, featuring a dielectric constant increase of 0.2 F/m or more at 10% compression and 0.3 F/m or more at 50% compression, with a foam layer thickness of 30 μm to 1,000 μm, average cell diameter of 10 μm to 200 μm, and porosity of 20% to 80%, enhancing sensitivity in electrostatic capacitance sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a related-art foam is used as dielectric, then the foam provides basic dielectric function, but the electrostatic capacitance is low and dielectric constant does not change significantly with thickness
Solution Approach 1:
The patent applies parameter changes by controlling the foam layer's physical parameters (density, cell structure, thickness) to achieve optimal dielectric properties. Specifically, the foam layer has a density of 0.2-0.5 g/cm³ and a controlled cell structure that enables significant dielectric constant changes (ΔK ≥ 0.2 F/m at 10% compression) when compressed, thereby improving sensitivity while maintaining reliable dielectric function.
Solution Approach 2:
The patent uses composite materials by combining the foam layer with pressure-sensitive adhesive layers on both sides. This composite structure integrates the dielectric properties of the foam with the adhesive properties of the PSA layers, creating a multi-functional material that provides both electrical performance and mechanical bonding capability for the sensor assembly.
2Measurement precision
If the foam layer is made thinner to improve sensitivity, then the dielectric constant change increases, but the impact absorbability decreases
Solution Approach 1:
The patent optimizes the foam layer thickness parameter to balance sensitivity and impact absorbability. The foam layer is designed with a thickness of 10-100 μm, which is thin enough to provide significant dielectric constant changes for high sensitivity (ΔK ≥ 0.2 F/m at 10% compression) while remaining thick enough to maintain adequate impact absorbability and structural integrity for the sensor application.
3Measurement precision
If the foam layer is made more flexible to improve sensitivity, then the dielectric constant changes more with compression, but the structural stability decreases
Solution Approach 1:
The patent controls the foam layer's physical parameters (density, cell structure, cross-linking) to achieve optimal flexibility-stability balance. The foam has a density of 0.2-0.5 g/cm³ and a controlled cell structure that provides sufficient flexibility for dielectric constant changes (ΔK ≥ 0.2 F/m) while maintaining structural stability through appropriate cross-linking and cellular architecture to prevent excessive deformation.
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 foam sheet significantly improves electrostatic capacitance and sensitivity in sensors by increasing dielectric constant upon compression, offering excellent impact absorbability and durability.
Implementation Method 1
the foam sheet has a dielectric constant increase amount Q-P at 10% compression of 0.2 (F/m) or more, where P (F/m) represents a dielectric constant of the foam sheet immediately after the foam sheet has been left at rest
Implementation Method 2
a pressure-sensitive adhesive layer arranged on at least one side of the foam layer
Data Source
AI summary
Provided is a foam sheet that can raise an electrostatic capacitance at the time of compression, and hence can improve sensitivity when used for an electrostatic capacitance sensor. The foam sheet includes: a foam layer; and a pressure-sensitive adhesive layer arranged on at least one side of the foam layer, wherein the foam sheet has a dielectric constant increase amount Q-P at 10% compression of 0.2 (F/m) or more, where P (F/m) represents a dielectric constant of the foam sheet immediately after the foam sheet has been left at rest under conditions of a temperature of 23° C. and a humidity of 50% for 2 hours, and Q (F/m) represents a dielectric constant of the foam sheet at a time when the foam sheet is compressed by 10% immediately after being left at rest under the conditions of a temperature of 23° C. and a humidity of 50% for 2 hours.