Stretchable Conductor Sheet with Carbon Shielding for Wash-Durable Wearable Wiring
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Solution Overview
Problem
Existing wearable electronic devices face challenges in creating stretchable conductor wiring that maintains conductivity and durability, especially when exposed to human body fluids and environmental factors like washing and sunlight, as current methods lack effective protective surface layers and often result in disconnection or resistance increase.
Innovation Solution
A stretchable conductor sheet with multiple layers, including a first layer with carbon-based particles for protection and a second layer with metal-based particles for conductivity, bonded with a hot melt adhesive to a fabric, ensuring the first layer shields the second from contaminants and mechanical stress, while maintaining conductivity through specific carbon-based filler properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single layer of conductive paste is applied to fabric, then the fabrication process is simple, but the wiring lacks durability and resistance increases after washing
Solution Approach 1:
The conductive wiring is divided into two distinct layers: a first layer applied directly to the fabric and a second layer applied over the first layer. This segmentation allows each layer to serve specific functions - the first layer provides adhesion and flexibility while the second layer provides conductivity and durability, resolving the contradiction between simple fabrication and reliable performance
Solution Approach 2:
The invention uses composite conductive paste formulations in each layer, combining conductive particles (silver, carbon, or carbon nanotubes) with binder resins and solvents. The first layer uses a composition optimized for adhesion to fabric, while the second layer uses a composition optimized for conductivity and wash durability, creating a composite structure that achieves both ease of manufacture and reliability
2Ease of manufacture
If conductive polymer coating is applied to fabric, then the coating can be applied easily, but the conductor layer cannot follow fabric stretch and disconnection occurs
Solution Approach 1:
The invention changes the physical and chemical parameters of the conductive paste composition to include flexible binder resins and appropriate solvent content, allowing the cured conductive layers to elongate with the fabric. The first layer is formulated with parameters that enable it to stretch with the fabric substrate, while the second layer is formulated to maintain conductivity during stretching, preventing disconnection while maintaining ease of coating application
3Adaptability or versatility
If conductive particles and stretchable binder resin are combined, then the composition has stretchability, but the resistivity is higher than metal wires or metal foil
Solution Approach 1:
The invention uses composite materials consisting of conductive particles (silver, carbon, or carbon nanotubes) combined with stretchable binder resins in specific ratios. This composite approach allows the material to exhibit both stretchability from the binder resin and conductivity from the conductive particles, achieving a balance between adaptability and electrical performance that neither material alone could provide
Solution Approach 2:
The invention applies different conductive particle types and concentrations in different layers - the first layer may use carbon-based particles for flexibility and adhesion, while the second layer uses metal particles like silver for lower resistance and higher conductivity. This local quality differentiation allows each layer to optimize for its specific function while working together to achieve both stretchability and acceptable resistance
4Reliability
If metal foil is used for wiring, then the conductivity is high, but the metal foil undergoes permanent plastic deformation and loses durability after excessive deformation
Solution Approach 1:
The invention changes the mechanical parameters of the conductive material by using particle-based composites instead of continuous metal foil. The conductive particles are embedded in a flexible binder resin matrix that can undergo elastic deformation and recover, allowing the wiring to withstand repeated stretching and washing cycles without permanent plastic deformation, while maintaining adequate conductivity through the particle network
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 solution provides a durable and conductive electrical wiring that withstands repeated wear and washing without significant resistance increase, maintaining effective conductivity and protecting the underlying layer from environmental exposure.
Implementation Method 1
a stretchable conductor sheet having adhesiveness comprising a hot melt adhesive layer capable of adhering to a fabric by heating
Implementation Method 2
including a first layer with carbon-based particles for protection and a second layer with metal-based particles for conductivity, bonded with a hot melt adhesive to a fabric, ensuring the first layer shields the second from contaminants and mechanical stress
Data Source
AI summary
An objective is to provide a stretchable conductor sheet which is useful as a material for electrical wiring and electrodes for garment-type electronic devices, the material having excellent durability in terms of washing and durability in terms of perspiration. A fabric provided with an electrode and an electrical wiring, which are formed from a stretchable conductor sheet, is obtained by: providing a film having releasability with a first stretchable conductor layer which is formed from a paste material that uses carbon-based particles as a conductive filler, while using a flexible resin as a binder resin; subsequently forming a second stretchable conductor layer, while using metal-based particles as a conductive filler; laminating a hot melt adhesive layer thereon; superposing the resulting laminate on a fabric after removing unnecessary parts from the laminate by means of partial slits; and subjecting the resulting fabric to hot pressing. Since the carbon-based particles adsorb a contamination substance of the metal-based particles, oxidation degradation and sulfuration degradation of the metal-based particles is reduced, thereby improving the durability.