Bio-Electrode Contact Layer Composition for Long-Wear Skin Compatibility
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Solution Overview
Problem
Current bio-electrodes for wearable devices face challenges in maintaining electric conductivity and biocompatibility over long periods, experiencing conductivity loss due to water evaporation and causing skin allergies, while also being prone to peeling off during use.
Innovation Solution
A bio-electrode composition featuring a resin with urethan bonds and salts of ammonium, sodium, or silver formed with sulfonamide, combined with carbon materials and metal powders, to create a durable, conductive, and biocompatible contact layer that maintains conductivity when wet or dry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water-soluble gel containing water and electrolyte is used for bio-electrode, then electric conductivity is achieved, but conductivity is lost due to water evaporation during long-time use
Solution Approach 1:
The patent changes the physical state of the electrolyte from liquid (water-based gel) to solid form by incorporating ionic liquid into the polymer matrix. This parameter change eliminates water evaporation while maintaining ionic conductivity, enabling long-term stable operation of the bio-electrode without conductivity loss.
Solution Approach 2:
The patent creates a composite material system combining polymer (for structural framework), ionic liquid (for ionic conductivity), and optionally metal nanowires or carbon materials (for enhanced conductivity). This composite structure maintains electrical performance over long periods by preventing water evaporation while preserving the conductive pathways.
2Reliability
If higher-ionization-tendency metal such as copper is used to improve conductivity, then electric conductivity is enhanced, but skin allergy occurs
Solution Approach 1:
The patent introduces an intermediary substance (polymer matrix with ionic liquid) between the metal components and the skin. This intermediary layer provides ionic conductivity through the ionic liquid while physically isolating potential allergenic metal ions from direct skin contact, thus preventing skin allergy reactions.
Solution Approach 2:
The patent employs biocompatible polymer and ionic liquid materials that are inherently safer for skin contact compared to traditional metals. These materials provide sufficient conductivity for wearable applications without the allergenic properties of copper or other high-ionization metals.
3Reliability
If electro-conductive polymer such as PEDOT-PSS is used, then conductivity is achieved, but skin allergy occurs due to strong acidity and the polymer peels off during washing
Solution Approach 1:
The patent changes the chemical composition from strongly acidic electro-conductive polymers to neutral or biocompatible ionic liquid-based conductive systems. This parameter change eliminates the acidity-induced skin allergy and improves adhesion stability, allowing the bio-electrode to withstand washing without peeling.
Solution Approach 2:
The patent creates a composite where ionic liquid is integrated within the polymer matrix, forming a stable conductive network that is mechanically bonded to the substrate. This composite structure prevents peeling during washing while maintaining conductivity, unlike surface-coated acidic polymers.
4Reliability
If metal nanowire is used to improve conductivity with small quantity, then electric conductivity is enhanced, but skin allergy occurs due to sharp tip shape
Solution Approach 1:
The patent uses polymer and ionic liquid as intermediary materials that provide conductivity without the sharp geometric features of metal nanowires. These intermediary materials have smooth surfaces at the micro-scale, eliminating skin irritancy while maintaining effective electrical conduction through ionic and electronic pathways.
Solution Approach 2:
The patent changes the morphology of conductive elements from sharp metal nanowires to smooth ionic liquid-filled polymer structures. This parameter change in shape and material composition eliminates the skin-piercing effect of sharp tips while preserving conductivity through the ionic liquid medium.
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 ensures stable electric conductivity and biocompatibility, preventing significant conductivity reduction and skin irritation, with enhanced adhesiveness and stretchability, suitable for long-term wear.
Implementation Method 1
a resin which has a urethan bond in a main chain and at least one salt selected from the group consisting of salts of ammonium, sodium, potassium, and silver formed with sulfonamide in a side chain
Data Source
Figure 1~3
Figure 4~6
AI summary
The present invention is a bio-electrode composition includes, as the component (A), a resin which has a urethan bond in a main chain and at least one salt selected from the group consisting of salts of ammonium, sodium, potassium, and silver formed with sulfonamide in a side chain. This can provide: a bio-electrode composition capable of forming a living body contact layer for a bio-electrode that is excellent in electric conductivity and biocompatibility, light-weight, manufacturable at low cost, capable of preventing significant reduction in the electric conductivity even when wetted with water or dried, soft, and excellent in stretchability and strength; a bio-electrode including a living body contact layer formed of the bio-electrode composition; and a method for manufacturing the bio-electrode.