Bio-electrode Composition Using Ionic Material and Lithium Titanate
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Solution Overview
Problem
Current bio-electrodes for medical wearable devices face challenges in maintaining electric conductivity and biocompatibility, particularly when exposed to water or worn for extended periods, due to issues with water evaporation, skin allergies, and high impedance from precious metals.
Innovation Solution
A bio-electrode composition comprising an ionic material with a polymer compound having specific repeating units and lithium titanate powder, combined with a silicone resin and carbon material, to form a living body contact layer that is both electrically conductive and biocompatible, while preventing significant 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 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 from liquid water to solid ice through freezing treatment. The hydrophilic gel is frozen at -40°C to -80°C, transforming the water from liquid to solid phase, which prevents evaporation while maintaining the gel's structure and ionic conductivity properties.
Solution Approach 2:
The patent utilizes the phase transition of water from liquid to solid state. By freezing the hydrophilic gel containing water and electrolytes, the water undergoes phase transition to ice, which eliminates evaporation losses during drying while preserving the gel's conductive properties through controlled freeze-drying.
2Reliability
If higher ionization tendency metal such as copper is used to improve electric conductivity, then electric conductivity is improved, but skin allergy occurs
Solution Approach 1:
The patent creates a composite electrode material consisting of hydrophilic gel (containing water and electrolytes) combined with biocompatible materials. This composite structure provides the necessary ionic conductivity through the gel while the biocompatible components prevent skin allergic reactions, resolving the contradiction between conductivity and skin safety.
3Reliability
If electro-conductive polymer such as PEDOT-PSS is used to improve electric conductivity, then electric conductivity is improved, but skin allergy and peeling occur due to strong acidity
Solution Approach 1:
The patent employs a hydrophilic gel-based electrode that can be disposed of after use, eliminating the need for durable, acid-resistant materials like PEDOT-PSS. This approach prioritizes skin safety and comfort over long-term durability, allowing the use of simpler, more biocompatible materials that can be replaced rather than reused.
4Reliability
If metal nanowire is used to improve electric conductivity with small quantities, then electric conductivity is improved, but skin allergy occurs due to pointed thin material
Solution Approach 1:
The patent uses a homogeneous hydrophilic gel matrix containing dissolved electrolytes, eliminating the need for discrete metal nanowire structures. This homogeneous gel structure provides uniform ionic conductivity throughout the material while avoiding the sharp, pointed surfaces of metal nanowires that cause skin irritation and allergic reactions.
5Reliability
If carbon nanotube is used to improve electric conductivity, then electric conductivity is improved, but skin stimulation occurs
Solution Approach 1:
The patent changes the conductivity mechanism from electronic conduction (carbon nanotubes) to ionic conduction (electrolytes in hydrophilic gel). This parameter change in the conduction mechanism eliminates the need for carbon nanotubes and their associated skin stimulation issues, while achieving the required electrical conductivity through ionic pathways in the gel.
6Reliability
If carbon black is used to improve electric conductivity, then electric conductivity is improved, but skin stimulation occurs
Solution Approach 1:
The patent transitions from using carbon-based electronic conductors (carbon black) to ionic conductors (electrolyte solutions in hydrophilic gel). This parameter change in the conduction type eliminates skin stimulation while maintaining electrical conductivity through ionic charge transport in the gel matrix.
7Reliability
If precious metal is used to improve electric conductivity, then electric conductivity is improved, but high impedance and high resistance to skin occur
Solution Approach 1:
The patent employs a hydrophilic gel that mimics the hydraulic/ionic properties of biological tissues. The gel's high water content and ionic composition create a hydraulic-like interface with the skin, enabling efficient ion transport and reducing impedance, unlike solid precious metals that create high resistance at the skin interface.
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 efficient electric signal transmission from the skin, avoids skin allergies, is lightweight, and remains effective in both wet and dry conditions, while being manufacturable at low cost.
Implementation Method 1
detects changes in ion concentration from the skin to convert the data into electricity
Implementation Method 2
convert changes in ion concentration into current
Implementation Method 3
hydrophilic gel containing water and electrolytes as ingredients of the above electro-conductive paste (Patent Document 1). The hydrophilic gel, containing sodium, potassium, and calcium electrolytes in a hydrophilic polymer for retaining water
Implementation Method 4
the use of electrode materials formed of metal nanowire, carbon black, carbon nanotube, or the like has been examined (Patent Documents 3, 4, and 5)
Data Source
Figure 1~3A
Figure 3B~4
AI summary
A bio-electrode composition includes (A) an ionic material and (B) a lithium titanate powder. 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 N-carbonyl-fluorosulfonamide. Thus, the present invention provides a bio-electrode composition capable of forming a living body contact layer for a bio-electrode that is excellent in electric conductivity and biocompatibility, is light-weight, can be manufactured at low cost, and can control significant reduction in the electric conductivity even when the bio-electrode is wetted with water or dried; a bio-electrode including a living body contact layer formed of the bio-electrode composition; and a method for manufacturing the bio-electrode.