Ionic Polymer Bio-electrode Composition for Stable Skin Conductivity

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Solution Overview

Problem

Existing bio-electrodes face challenges in maintaining electric conductivity over long periods, causing skin allergies, and being lightweight and cost-effective, while also requiring high biocompatibility and adhesiveness.

Innovation Solution

A bio-electrode composition comprising an ionic polymer material with specific repeating units, including salts of ammonium, sodium, potassium, and silver formed with fluorosulfonic acid, fluorosulfonimide, and N-carbonyl-fluorosulfonamide, and a repeating unit with a nitro group, which forms a living body contact layer that is electrically conductive, biocompatible, and has excellent stretchability and adhesiveness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If water-soluble gel containing water and electrolyte is used as bio-electrode material, then electric conductivity is improved, but water evaporation during drying process causes loss of electric conductivity

Engineering Contradiction:
Improveelectric conductivityVSAvoidwater content stability
Core Design Contradiction:
ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent replaces water as the solvent with an organic solvent that has different evaporation characteristics, fundamentally changing the physical parameters of the gel system to prevent water loss while maintaining electric conductivity

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite gel system combining organic solvent, electrolyte, and polymer matrix that achieves both water resistance and electric conductivity, overcoming the limitation of pure water-based gels

Inventive Principle:
Principle #40Composite materials

2Reliability

If higher-ionization-tendency metal such as copper is used to improve electric conductivity, then conductivity is improved, but skin allergy is caused

Engineering Contradiction:
Improveelectric conductivityVSAvoidskin allergy
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an organic solvent-based gel as an intermediary medium between the metal electrode and the skin, which maintains electric conductivity while preventing direct contact between copper ions and skin, thereby eliminating allergic reactions

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent uses copper powder with controlled particle size and morphology that provides sufficient conductivity for the application lifecycle without requiring high purity or expensive alternatives, balancing cost and performance while minimizing biocompatibility issues

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

3Reliability

If electro-conductive polymer such as PEDOT-PSS is used to improve electric conductivity, then conductivity is improved, but skin allergy is caused due to strong acidity and peeling occurs during washing

Engineering Contradiction:
Improveelectric conductivityVSAvoidskin allergy and peeling
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical environment by using organic solvents with different polarity and pH characteristics compared to water, which neutralizes the strong acidity of PEDOT-PSS and prevents skin irritation while maintaining the polymer's conductive properties

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent forms a composite structure where PEDOT-PSS is embedded in an organic solvent-based gel matrix, which provides mechanical stability and prevents peeling during washing while maintaining electric conductivity

Inventive Principle:
Principle #40Composite materials

4Reliability

If metal nanowire is used to improve electric conductivity with small quantities, then conductivity is improved, but skin allergies are caused due to sharp tips

Engineering Contradiction:
Improveelectric conductivityVSAvoidskin allergy
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent uses organic solvent-based gel as an intermediary layer between metal nanowires and skin, which maintains the nanowires' high conductivity while providing a biocompatible interface that prevents direct contact between sharp nanowire tips and skin

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a composite material system combining metal nanowires dispersed in organic solvent-based gel, which synergistically achieves high conductivity from nanowires and biocompatibility from the gel matrix

Inventive Principle:
Principle #40Composite materials

5Reliability

If noble metal film is used to improve electric conductivity, then conductivity is improved, but high impedance and high resistance to skin occur during ion conversion

Engineering Contradiction:
Improveelectric conductivityVSAvoidhigh impedance and resistance
Core Design Contradiction:
ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent creates a composite electrode structure combining noble metal film with organic solvent-based gel containing electrolyte, which leverages the high conductivity of noble metal while the gel component facilitates ion-to-current conversion, reducing impedance and skin resistance

Inventive Principle:
Principle #40Composite materials

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 bio-electrode composition achieves stable electric conductivity regardless of water exposure or drying, maintains biocompatibility, and ensures strong adhesion to the skin, making it suitable for long-term use in medical wearable devices.

Implementation Method 1

The water-soluble gel contains sodium, potassium, or calcium as the electrolyte in a water-soluble polymer for retaining water, and converts changes of ion concentration from skin into electricity

Methodology Applied
Scientific EffectIonization: Ionisation

Implementation Method 2

the ionic liquid is thermally and chemically stable, and the conductivity is excellent

Methodology Applied
Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 3

contains sodium, potassium, or calcium as the electrolyte in a water-soluble polymer

Methodology Applied
Scientific EffectElectrolyte conduction: Electrolyte

Data Source

PatentEP4309582B1Bio-electrode composition, bio-electrode, and method for manufacturing the same
Publication Date: 2025.04.09 SHIN ETSU CHEMICAL CO LTD
  • EP4309582B1 patent drawingFigure 1~2
  • EP4309582B1 patent drawingFigure 3~4
  • EP4309582B1 patent drawingFigure 5~6

AI summary

The present invention is a bio-electrode composition containing an ionic polymer material as a component (A), where the component (A) includes a polymer having: a repeating unit-a having a structure selected from the group consisting of salts of ammonium, sodium, potassium, and silver formed with any of fluorosulfonic acid, fluorosulfonimide, and N-carbonyl-fluorosulfonamide; and a repeating unit-b having a nitro group. This provides: a bio-electrode composition capable of forming a living body contact layer for a bio-electrode that is excellent in electric conductivity and biocompatibility, is light-weight, can be manufactured at low cost, can control significant reduction in conductivity either when the bio-electrode is soaked in water or dried, and is soft and has excellent stretchability and adhesiveness; a bio-electrode including a living body contact layer formed of the bio-electrode composition; and a method for manufacturing the bio-electrode.