Conductive Rubber Bioelectrode for Stable Reuse and Low Impedance

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Solution Overview

Problem

Conventional bioelectrodes face issues such as insufficient adhesion to the skin, discomfort due to rigidity or softness, and increased contact impedance with repeated use, necessitating complex structures or the use of gels.

Innovation Solution

A bioelectrode composed of silver particles treated with a silane coupling agent and room temperature-curable silicone rubber, featuring a pointed tip end and inclined face, integrated with a conductive support, to enhance adhesion and reduce contact impedance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a metal probe is used to adhere to the scalp, then electrical conductivity is improved, but the rigidity causes pain and discomfort to the subject

Engineering Contradiction:
Improveelectrical conductivityVSAvoidpain and discomfort
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies this principle by coating the metal probe with a flexible insulating layer that has controlled electrical conductivity. This flexible coating allows the probe to conform to the scalp surface without causing pain, while still maintaining sufficient electrical conductivity for biosignal detection. The coating acts as a buffer between the rigid metal core and the soft scalp tissue.

Inventive Principle:
Principle #30Flexible shells and thin films

Solution Approach 2:

The patent employs composite materials by combining metal particles or metal powder with polymer or rubber matrices. This creates a composite electrode structure that integrates the high electrical conductivity of metal with the flexibility and comfort of polymer/rubber materials. The composite structure allows the electrode to maintain shape while adapting to curved scalp surfaces.

Inventive Principle:
Principle #40Composite materials

2Ease of operation

If a water-absorbent member impregnated with electrolyte solution is used, then gel application is eliminated, but the electrode structure becomes excessively soft and lacks elasticity

Engineering Contradiction:
Improveno gel application requiredVSAvoidelasticity and structural integrity
Core Design Contradiction:
Ease of operationVSStrength

Solution Approach 1:

The patent uses composite materials by combining water-absorbent polymers with metal particles or metal powder embedded in a polymer/rubber matrix. This composite structure provides both the water-absorbent properties for electrolyte retention and the structural elasticity needed for repeated use. The metal reinforcement within the composite prevents excessive softness while maintaining the gel-free advantage.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by creating regions with different properties within the electrode structure. The water-absorbent regions provide electrolyte retention and comfort, while reinforced regions with metal particles or polymer-rubber composites provide structural elasticity and durability. This localized differentiation allows the electrode to be soft where needed for comfort but structurally sound where needed for repeated use.

Inventive Principle:
Principle #3Local quality

3Adaptability or versatility

If multiple metal probes are provided for scalp detection, then measurement coverage is improved, but adhesion of all probes to the curved scalp surface becomes difficult

Engineering Contradiction:
Improvemeasurement coverageVSAvoidadhesion to curved surface
Core Design Contradiction:
Adaptability or versatilityVSEase of operation

Solution Approach 1:

The patent applies this principle by using flexible metal probes coated with compliant materials that can conform to curved scalp surfaces. The flexible coating allows multiple probes to adapt to the three-dimensional geometry of the scalp, ensuring good contact and adhesion across multiple measurement points simultaneously.

Inventive Principle:
Principle #30Flexible shells and thin films

Solution Approach 2:

The patent uses composite materials with metal particles embedded in flexible polymer or rubber matrices, creating probes that are both conductive and adaptable to curved surfaces. This composite structure allows multiple probes to maintain consistent contact with the scalp's curvature, improving adhesion and measurement reliability across multiple detection points.

Inventive Principle:
Principle #40Composite materials

4Reliability

If silver particles are used in the electrode member, then electrical conductivity is improved, but contact impedance increases with repeated use due to particle detachment

Engineering Contradiction:
Improveelectrical conductivityVSAvoidstability with repeated use
Core Design Contradiction:
ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent employs composite materials by embedding silver particles within a polymer or rubber matrix that provides structural support and particle retention. This composite structure maintains the high electrical conductivity of silver particles while preventing their detachment during repeated use. The matrix acts as a binding medium that secures particles in place.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent applies parameter changes by modifying the physical and chemical properties of the electrode materials. Silver particles are treated with surface coatings or combined with specific polymers/rubbers that enhance particle adhesion and prevent detachment. The particle size, distribution, and surface treatment parameters are optimized to maintain stable contact impedance over repeated use while preserving electrical conductivity.

Inventive Principle:
Principle #35Parameter changes

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 bioelectrode provides satisfactory elasticity, prevents discomfort, and maintains stable contact impedance even with repeated use, eliminating the need for gels and ensuring reliable biosignal detection.

Implementation Method 1

metal particles having a crosslinkable functional group introduced onto a surface by surface treatment with a silane coupling agent

Methodology Applied
Scientific EffectSilane coupling agent treatment: Chemical Bonding

Implementation Method 2

containing a crosslinkable functional group introduced onto a surface by surface treatment with a silane coupling agent

Methodology Applied
Scientific EffectCrosslinking: Chemical Bonding

Implementation Method 3

detecting a biosignal of the subject

Methodology Applied
Scientific EffectBiosignal detection: Conduction (electrical)

Data Source

PatentEP3868289B1Bioelectrode and bioelectrode production method
Publication Date: 2026.03.18 NOK CORP
  • EP3868289B1 patent drawingFigure 1
  • EP3868289B1 patent drawingFigure 2
  • EP3868289B1 patent drawingFigure 3

AI summary

Provided are a bioelectrode having a structure not complicated, having a satisfactory elasticity, and capable of preventing increase of contact impedance due to increase of the number of times of usage, and a method for producing the bioelectrode. A bioelectrode (1) includes a support member (2), which is an electrically conductive member, and at least one electrode member (3), which is a member projecting from the support member (2). At least the electrode member (3) is molded from an electrically conductive rubber containing a silicone rubber and treated metal particles containing a crosslinkable functional group on a surface thereof.