Piezoelectric Sensor Cutout Electrodes Impurity Release

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Solution Overview

Problem

Piezoelectric sensors face deterioration in piezoelectric properties due to the penetration of water vapor or solvent from pressure sensitive adhesives, which are trapped within the sensor, leading to irreversible damage.

Innovation Solution

The design includes cutout sections in electrodes and fixative layers that expose parts of the piezoelectric sheet, allowing impurities to escape, and the use of electrical insulation sheets to prevent short circuits and facilitate easy connection of conductive wires.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the piezoelectric sheet is sealed by a fixative during manufacturing, then the sensor structure is complete and electrodes are fixed, but water vapor or solvent from the pressure sensitive adhesive penetrates into the piezoelectric sheet and cannot be released, causing deterioration of piezoelectric properties

Engineering Contradiction:

Improvepiezoelectric property stabilityVSAvoidpenetration of water vapor or solvent

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The electrode structure is segmented by introducing cutout sections that create exposed portions of the piezoelectric sheet. This segmentation allows the piezoelectric sheet to be divided into covered portions (sealed by fixative) and exposed portions (accessible to atmosphere), enabling selective sealing while maintaining impurity release pathways.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The harmful trapped impurities (water vapor or solvent) are extracted from the piezoelectric sheet through the exposed portions. By creating regions where the piezoelectric sheet is not covered by electrodes or fixative, the patent enables the extraction of penetrants that would otherwise be trapped and cause deterioration.

Inventive Principle:

Principle #2Taking out (Extraction)

2Area of stationary object

If the entire piezoelectric sheet is covered by electrodes and fixative, then the sensor provides complete electrical coverage, but impurities penetrate into the piezoelectric sheet and cannot be released

Engineering Contradiction:

Improvecoverage area of electrodesVSAvoidpiezoelectric property maintenance

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The patent applies local quality by creating different coverage conditions in different regions of the piezoelectric sheet. Some regions are covered by electrodes and fixative for electrical functionality, while other regions are exposed to allow impurity release. This local differentiation resolves the contradiction between complete coverage and impurity release.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If pressure sensitive adhesive containing solvent is used to laminate electrodes, then the manufacturing process is simplified, but the solvent penetrates into the piezoelectric sheet and cannot be removed

Engineering Contradiction:

Improveelectrode lamination processVSAvoidsolvent penetration and residue

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful effect of solvent penetration into a beneficial outcome by designing exposed portions that allow the solvent to escape. Instead of preventing solvent penetration (which would require complex sealing), the patent allows penetration but provides escape routes, transforming the harmful trapped solvent into a released byproduct that does not damage the piezoelectric properties.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 maintains excellent piezoelectric properties over a long period by allowing impurities to be released, simplifies manufacturing, and reduces sensor thickness while ensuring reliable electrical connections.

Implementation Method 1

Vital signal sensors employing piezoelectric sheets as sensors have been known. When a pressure generated by a pulse wave, a respiration, or a body motion is applied on the piezoelectric sheet, an electrical signal having a size corresponding to the pressure is generated from the piezoelectric sheet.

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS10768066B2Piezoelectric sensor including overlapping cutout sections in a signal electrode, a first ground electrode, and a second electrode

Publication Date: 2020.09.08 SEKISUI CHEMICAL CO LTD

AI summary

A piezoelectric sensor including: a piezoelectric sheet; a first ground electrode integrally laminated on a first side of the piezoelectric sheet and having a first cutout section; a signal electrode integrally laminated on a second side of the piezoelectric sheet and having a third cutout section; and a second ground electrode integrally laminated on the signal electrode so as to be electrically insulated from the signal electrode and having a second cutout section. The cutout sections of the signal electrode, the first ground electrode, and the second ground electrode are at least partially overlapped with one another in a thickness direction of the piezoelectric sheet. A portion of the piezoelectric sheet exposed from a portion where the cutout sections of the signal electrode, the first ground electrode, and the second ground electrode are overlapped with one another serves as an exposed section.