Bio-electrode Ionic Liquid Gel Conductivity
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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 experiencing reduced conductivity due to water exposure and causing skin allergies, while also requiring lightweight and cost-effective manufacturing.
Innovation Solution
A bio-electrode composition comprising an ionic material with a polymer compound having specific repeating units and a metal powder, such as silver, to form a living body contact layer that is both electrically conductive and biocompatible, with a method involving application and curing on an electro-conductive base material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrophilic gel containing water and electrolytes is used as 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 physical state parameter of the gel from a water-based liquid gel to a solid-like gel by replacing water with ionic liquid. This parameter change eliminates evaporation while maintaining ionic conductivity, as ionic liquids have negligible vapor pressure compared to water.
Solution Approach 2:
The patent creates a composite gel structure by combining polymer matrix with ionic liquid fillers. This composite approach allows the gel to maintain structural integrity and ionic conductivity simultaneously, with the polymer providing mechanical stability and the ionic liquid providing conductive pathways.
2Reliability
If higher ionization tendency metal such as copper is used to improve electric conductivity, then conductivity is improved, but skin allergy is caused
Solution Approach 1:
The patent uses disposable carbon-based electrode materials that are biocompatible and non-allergenic. These materials are designed for single-use or limited-use applications where the electrode is replaced rather than cleaned and reused, eliminating the accumulation of irritants that cause allergies.
Solution Approach 2:
The patent changes the material composition from reactive metals (copper, aluminum) to inert carbon-based materials. This parameter change in material chemistry eliminates galvanic reactions and metal ion release that trigger allergic responses, while maintaining adequate electrical conductivity for biomedical applications.
3Reliability
If electro-conductive polymer such as PEDOT-PSS is used, then electric conductivity is improved, but skin allergy and peeling occur due to strong acidity
Solution Approach 1:
The patent changes the pH parameter of the electrode material from highly acidic (pH < 1 for PEDOT-PSS) to neutral or slightly basic by using carbon-based materials and ionic liquid gels. This eliminates acid-induced skin irritation and allergies while maintaining ionic conductivity through alternative mechanisms.
Solution Approach 2:
The patent employs disposable carbon-based electrodes that do not require long-term adhesion to skin. These electrodes are designed for short-duration measurements where removal occurs before significant peeling or allergic reaction can develop, eliminating the need for highly adhesive acidic polymers.
4Reliability
If metal nanowire or carbon nanotube is used to improve conductivity, then contact probability is improved, but skin stimulation and allergy occur
Solution Approach 1:
The patent changes the morphology parameter from sharp, high-aspect-ratio structures (nanowires, nanotubes) to rounded, low-aspect-ratio carbon particles or flakes. This parameter change reduces mechanical penetration into skin and eliminates the sharp edges that cause physical irritation and allergic responses.
5Reliability
If precious metal is used to improve conductivity, then electric conductivity is improved, but impedance and resistance to skin increase
Solution Approach 1:
The patent changes the charge transfer mechanism from electron conduction (metallic) to ion conduction (electrolytic). By using ionic liquid gels with high ionic mobility, the electrode achieves low impedance through ionic charge transfer at the skin interface, matching the electrochemical nature of skin potentials and reducing contact impedance.
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, maintaining performance even when wetted or dried, while being lightweight and cost-effective, with improved adhesion and reduced risk of skin allergies.
Implementation Method 1
the ionic liquid is thermally and chemically stable, and the electric conductivity is excellent
Implementation Method 2
a polymer compound comprising a repeating unit-a having a structure selected from the group consisting of an ammonium salt, a sodium salt, a potassium salt, and a silver salt of any of fluorosulfonic acid, fluorosulfonimide, and fluorosulfonamide
Implementation Method 3
a metal powder; the component (A) being a polymer compound
Data Source
AI summary
A bio-electrode, excellent in electric conductivity and biocompatibility, light-weight, manufacturable at low cost, and free from large lowering of the electric conductivity even though it is wetted with water or dried, includes an electro-conductive base material and a living body contact layer formed on the electro-conductive base material. The living body contact layer is a cured material of a bio-electrode composition including (A) an ionic material and (C) a metal powder, wherein the component (A) is a polymer compound containing a repeating unit-a having a structure selected from an ammonium salt, a sodium salt, a potassium salt, and a silver salt of any of fluorosulfonic acid, fluorosulfonimide, and fluorosulfonamide.