Ionic Liquid Bio-Electrode Composition for Stable Conductivity
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Solution Overview
Problem
Existing bio-electrodes for wearable devices face challenges in maintaining consistent electric conductivity over time, causing skin allergies, and failing to adhere well to the skin, especially when wet or dry.
Innovation Solution
A bio-electrode composition comprising a silicone bonded to an ionic polymer with a T unit structure, which forms a living body contact layer that is highly conductive, biocompatible, stretchable, and adhesive, preventing significant conductivity loss 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 improved, but water evaporation during drying process causes loss of electric conductivity
Solution Approach 1:
The invention changes the physical state of the electrolyte from liquid (water-based gel) to solid (ionic liquid), eliminating evaporation while maintaining ionic conductivity. This parameter change resolves the contradiction between achieving good electric conductivity and maintaining stability during drying.
Solution Approach 2:
The invention uses a composite structure combining ionic liquid with polymer materials to create a gel-like substance that maintains ionic conductivity without water evaporation issues. This composite approach allows the bio-electrode to retain conductivity stability during drying while preserving the beneficial properties of gel-based electrodes.
2Reliability
If higher-ionization-tendency metal such as copper is used, then electric conductivity is improved, but skin allergy occurs
Solution Approach 1:
The invention introduces an intermediary layer of ionic liquid-based gel between the metal electrode and the skin. This intermediary layer provides the necessary ionic conductivity for signal detection while preventing direct contact between potentially allergenic metals and the skin, thus resolving the contradiction between conductivity and biocompatibility.
Solution Approach 2:
The invention changes the electrode material from reactive metals (copper, aluminum) to noble metals (gold, platinum) or non-metallic conductive materials. This parameter change in material selection maintains electric conductivity while eliminating skin allergy risks.
3Reliability
If electro-conductive polymer such as PEDOT-PSS is used, then electric conductivity is improved, but skin allergy occurs due to strong acidity and peeling during washing
Solution Approach 1:
The ionic liquid-based gel serves as an intermediary layer between the electro-conductive polymer and the skin, buffering the strong acidity of the polymer while maintaining ionic conductivity. This resolves the contradiction by protecting the skin from harmful effects while preserving the electrical performance.
Solution Approach 2:
The invention creates a composite structure combining ionic liquid with polymer materials to develop a new type of electro-conductive gel that maintains the advantages of polymer-based electrodes (flexibility, adhesion) while eliminating their disadvantages (acidity, peeling).
4Reliability
If metal nanowire is used, then electric conductivity is improved, but skin allergy occurs due to sharp tips and thin structure
Solution Approach 1:
The ionic liquid-based gel acts as an intermediary layer between the metal nanowire electrode and the skin, providing a biocompatible interface that maintains electrical conductivity while preventing direct contact between the sharp nanowire tips and the skin, thus eliminating allergy risks.
5Reliability
If noble metal is used for bio-electrode, then electric conductivity is improved, but high impedance and high resistance to skin occurs during electrical conduction
Solution Approach 1:
The ionic liquid-based gel serves as an intermediary layer between the noble metal electrode and the skin, facilitating ion-to-electron conversion and reducing interfacial impedance. This resolves the contradiction by maintaining the biocompatibility and conductivity of noble metals while eliminating their high impedance issue through the mediating gel layer.
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 long-term collection of biological signals with high sensitivity and adhesion, preventing skin allergies and maintaining conductivity across various environmental conditions.
Implementation Method 1
converts changes of ion concentration from skin into electricity
Implementation Method 2
a silicone bonded to an ionic polymer and having a structure containing a T unit... excellent in electric conductivity
Data Source
Figure 1~3
Figure 4~6
AI summary
A bio-electrode composition contains (A) a silicone bonded to an ionic polymer and having a structure containing a T unit shown by the following general formula (T1): (R0SiO3/2) (T1), the structure excluding a cage-like structure. In the formula, R° represents a linking group to the ionic polymer. The ionic polymer is a polymer containing a repeating unit having a structure selected from the group consisting of salts of ammonium, lithium, sodium, potassium, and silver formed with any of fluorosulfonic acid, fluorosulfonimide, and N-carbonyl-fluorosulfonamide. Thus, the 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, biocompatibility, stretchability, and adhesion, soft, light-weight, and manufacturable at low cost, and which prevents significant reduction in the electric conductivity even when wetted with water or dried.