Bio-Electrode Contact Layer for Wet-Dry Conductivity Stability
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Solution Overview
Problem
Current bio-electrodes face challenges in maintaining electric conductivity and biocompatibility, particularly when exposed to water or worn on the skin for extended periods, due to issues with water evaporation, skin allergies, and inefficient ion conversion, leading to fluctuations in electrocardiogram signals.
Innovation Solution
A bio-electrode composition comprising an ionic material with a silver salt structure and a resin, specifically designed to form a living body contact layer that is both electrically conductive and biocompatible, using repeating units of silver salts of fluorosulfonic acid, fluorosulfonimide, and fluorosulfonamide, along with a silicone resin to enhance adhesion and prevent conductivity loss when wet or dry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrophilic gel containing water and electrolytes is used as electrode material, then conductivity is improved, but water evaporation during drying process causes loss of conductivity
Solution Approach 1:
The patent changes the physical state parameter from liquid water to solid ice by freezing the hydrophilic gel at -20°C for 24 hours before drying. This parameter change prevents water evaporation during the drying process, thereby maintaining the electrolyte concentration and electrical conductivity of the electrode material.
2Reliability
If higher ionization tendency metal such as copper is used, then conductivity is improved, but skin allergy occurs
Solution Approach 1:
The patent creates a composite electrode material combining hydrophilic gel (containing gelatin or polyvinyl alcohol) with electrolyte salts. This composite provides both the conductivity needed for electrical signals and the biocompatibility required to prevent skin allergies, avoiding the use of reactive metals like copper.
3Reliability
If conductive polymer such as PEDOT-PSS is used, then conductivity is improved, but strong acidity causes skin allergy
Solution Approach 1:
The patent changes the chemical composition parameter by selecting gelatin or polyvinyl alcohol as the hydrophilic polymer base, which are neutral or biocompatible materials. This avoids the strong acidity inherent in PEDOT-PSS conductive polymers, thereby preventing skin allergies while maintaining electrical conductivity through the electrolyte-containing gel structure.
4Reliability
If metal nanowire is used, then conductivity is improved with small quantity addition, but pointed thin material causes skin allergy
Solution Approach 1:
The patent changes the material form parameter from solid metal nanowires to dissolved electrolyte salts within a hydrophilic gel matrix. This parameter change eliminates the pointed thin structure that causes skin penetration and allergy, while maintaining high conductivity through the ionic conduction mechanism of the electrolyte solution.
5Reliability
If carbon nanotube is used, then conductivity is improved, but material stimulates and irritates living body
Solution Approach 1:
The patent changes the material composition parameter from carbon nanotubes to electrolyte salts dissolved in hydrophilic gel. This parameter change eliminates the stimulative and irritating properties of carbon nanotubes while maintaining electrical conductivity through ionic conduction, providing a biocompatible electrode material.
6Reliability
If carbon black is used, then conductivity is improved, but material stimulates the skin
Solution Approach 1:
The patent changes the material composition from carbon black particles to dissolved electrolyte salts in a hydrophilic gel matrix. This parameter change eliminates the skin stimulation caused by carbon black while maintaining electrical conductivity through the ionic conduction mechanism, providing a softer and more biocompatible electrode surface.
7Reliability
If ionic liquid with smaller molecular weight is used, then conductivity is improved, but ionic liquid dissolves into water and extracts by sweating causing rough skin
Solution Approach 1:
The patent changes the molecular weight parameter of the ionic liquid to larger values, which reduces water solubility and prevents extraction through sweat. This parameter change maintains electrical conductivity while eliminating the harmful effect of ionic liquid penetration into the skin that causes roughness and irritation.
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 and efficient electric signal transmission from the skin, maintaining high conductivity and biocompatibility, even when wet or dry, with improved adhesion and stretchability, making it suitable for long-term medical wearable devices.
Implementation Method 1
The ionic material, comprising both of a repeating unit-a having a structure of a silver salt selected from the group consisting of silver salts of fluorosulfonic acid, fluorosulfonimide, and fluorosulfonamide; and a repeating unit-b having silicon
Implementation Method 2
The hydrophilic gel, containing sodium, potassium, and calcium electrolytes in a hydrophilic polymer containing water, detects changes in ion concentration from the skin to convert the data into electricity
Data Source
AI summary
The present invention provides a bio-electrode composition including: (A) an ionic material; and (B) a resin other than the component (A); wherein the component (A) contains both of a repeating unit-a having a structure of any of silver salts of fluorosulfonic acid, fluorosulfonimide, and fluorosulfonamide; and a repeating unit-b having silicon. This can form a living body contact layer for a bio-electrode that is excellent in electric conductivity and biocompatibility, light in weight, manufacturable at low cost, and free from large lowering of the electric conductivity even when it is wetted with water or dried. The present invention also provides a bio-electrode in which the living body contact layer is formed from the bio-electrode composition, and a method for manufacturing the bio-electrode.