Low-Water Bio-Electrode Composition for Stable Skin Signal Sensing
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Solution Overview
Problem
Current bio-electrodes for wearable devices face challenges in maintaining electric conductivity and biocompatibility over long periods, often causing skin allergies and leaving residues due to water evaporation, acidity, or high impedance from noble metals, while also requiring precise manufacturing and adhesion properties.
Innovation Solution
A bio-electrode composition comprising an ionic polymer, addition reaction-curable silicone with hydrosilyl groups, and a platinum-group catalyst, with a solvent that minimizes water content and avoids hydroxy, carboxyl, nitrogen, or thiol groups, forming a layer that is electrically conductive, biocompatible, and lightweight, and does not leave residues upon peeling.
Engineering Contradictions & Design Principles
Engineering 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
Solution Approach 1:
The patent changes the solvent system from water-based to organic solvent-based (alcohol, ether, ester, or ketone). This parameter change eliminates water evaporation issues while maintaining electric conductivity through the organic solvent medium, directly resolving the contradiction between conductivity reliability and compositional stability during drying.
Solution Approach 2:
The patent uses a composite material system combining ionic polymer (for conductivity), silicone adhesive (for bonding), and organic solvent (for processability). This composite approach allows the electrode to maintain conductivity without water content, solving the contradiction by integrating multiple functional materials that compensate for each other's limitations.
2Reliability
If higher-ionization-tendency metal such as copper is used to improve electric conductivity, then conductivity is improved, but skin allergy occurs
Solution Approach 1:
The patent uses disposable ionic polymer-based electrode materials that provide sufficient conductivity for single-use or limited-use applications without requiring highly reactive metals. This approach eliminates skin allergy risks while maintaining functional conductivity for the intended service life.
Solution Approach 2:
The patent creates a composite electrode material using ionic polymer combined with silicone adhesive and organic solvent. This composite provides adequate electrical conductivity through ionic conduction mechanisms without using reactive metals, thereby eliminating skin allergy issues while maintaining functional performance.
3Reliability
If electro-conductive polymer such as PEDOT-PSS is used to improve conductivity, then conductivity is improved, but skin allergy occurs due to strong acidity and peeling during washing
Solution Approach 1:
The patent changes the chemical composition parameters by replacing acidic electro-conductive polymers with ionic polymer in an organic solvent system. This eliminates the strong acidity issue that causes skin allergy and peeling, while maintaining conductivity through ionic conduction in the organic medium.
Solution Approach 2:
The patent employs disposable ionic polymer-based electrodes that achieve sufficient conductivity for their service life without requiring durable, washable constructions. This approach eliminates the need for acid-resistant coatings and complex adhesion systems, reducing skin allergy risks.
4Reliability
If metal nanowire, carbon black, or carbon nanotube is used to improve conductivity, then conductivity is improved, but skin stimulation or allergy occurs
Solution Approach 1:
The patent uses ionic polymer-based electrode material that provides sufficient conductivity for disposable or limited-use applications without requiring conductive fillers like metal nanowires or carbon materials. This eliminates skin stimulation issues associated with sharp or reactive filler particles.
Solution Approach 2:
The patent creates a composite system using ionic polymer as the conductive phase combined with silicone adhesive and organic solvent. This composite provides uniform conductivity throughout the material matrix without discrete conductive particles, eliminating skin stimulation from sharp edges or reactive surfaces.
5Reliability
If noble metal is used to improve electric conductivity, then conductivity is improved, but high impedance and high resistance to skin occurs due to difficulty in ionization
Solution Approach 1:
The patent replaces electronic conduction through noble metals with ionic conduction through ionic polymer. This substitution changes the conduction mechanism from electron-based to ion-based, enabling direct ion-to-current conversion at the skin interface and eliminating the high impedance problem associated with noble metals.
Solution Approach 2:
The ionic polymer acts as an intermediary material between the skin and the electrode substrate. It facilitates direct ion-to-current conversion by providing ionic conduction pathways that match the ionic output of the skin, eliminating the impedance mismatch problem caused by noble metal electron conduction.
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 sensitive detection of biological signals without skin irritation, maintains conductivity in wet or dry conditions, and allows for efficient, low-cost manufacturing with improved adhesion and film strength.
Implementation Method 1
converts changes of ion concentration from skin into electricity
Implementation Method 2
an addition reaction-curable silicone having at least a hydrosilyl group
Implementation Method 3
a platinum-group catalyst
Data Source
Figure 1~3
Figure 4~6
AI summary
A bio-electrode composition contains (A) an ionic polymer material, (B) an addition reaction-curable silicone having at least a hydrosilyl group, (C) a platinum-group catalyst, and a solvent. The bio-electrode composition has a water content of 0.2 mass% or less. The solvent includes one or more of an ether solvent, an ester solvent, and a ketone solvent each of which does not contain a hydroxy group, a carboxyl group, a nitrogen atom, or a thiol group. Thus, present invention provides: a bio-electrode composition capable of forming a living body contact layer for a bio-electrode which is excellent in electric conductivity and biocompatibility, light-weight, and manufacturable at low cost, and which does not leave residue on skin after attachment to and peeling from the skin; a bio-electrode including a living body contact layer formed of the bio-electrode composition; and a method for manufacturing the bio-electrode.