Stretchable Printed Circuits on Buckled Polymer Membranes
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Solution Overview
Problem
Conventional flexible circuits are too stiff for integration into textiles and suffer from durability and electrical connectivity issues when stretched, leading to breaks and open circuits due to the movement of textile fiber bundles.
Innovation Solution
A conductive article with a printed circuit bonded to a stretchable substrate, featuring a synthetic polymer membrane with a buckled orientation and an electrically conductive trace that includes a continuous network of conductive particles, which maintains conductivity even up to 50% strain without significant resistance change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional flexible circuits are built upon stiff materials such as Mylar or Kapton, then flexibility is improved compared to traditional copper and fiberglass circuit boards, but the circuits remain too stiff to be integrated into textiles and maintain durability during washing and flexing
Solution Approach 1:
The patent uses a thin film laminate structure comprising a flexible circuit layer bonded to a textile substrate. The flexible circuit layer is made sufficiently thin to allow the composite structure to flex and stretch with the textile, while the lamination provides durability during washing and flexing operations.
Solution Approach 2:
The patent creates a composite material system by bonding a flexible circuit layer to a textile substrate through lamination. This composite structure combines the electrical conductivity and circuit functionality with the flexibility and washability of textile, resolving the contradiction between circuit durability and textile flexibility.
2Ease of operation
If conductive inks are printed directly onto textiles, then flexibility and stretch are retained, but durability and electrical connectivity are compromised due to breaks and open circuits when the textile is stretched
Solution Approach 1:
The patent applies a flexible circuit layer in the form of a thin film laminate over the conductive ink on textile. This thin film protects the conductive ink from breaking during stretching while maintaining the flexibility and stretchability of the underlying textile structure.
Solution Approach 2:
The patent creates a multi-layer composite structure where a flexible circuit layer is bonded to the textile substrate. This composite provides both the electrical connectivity of the circuit layer and the flexibility/stretch of the textile, while the lamination prevents delamination and maintains durability during washing and stretching.
3Reliability
If conductive inks are printed onto urethane films and heat bonded to stretch textiles, then durability is improved, but the resulting laminate has significantly less stretch than the original textile
Solution Approach 1:
The patent uses a thin film laminate structure that is sufficiently thin and flexible to stretch with the textile substrate. By controlling the thickness and material properties of the flexible circuit layer, the laminate maintains the stretchability of the original textile while providing durability during washing and flexing.
4Reliability
If insulative inks are used to sandwich conductive inks and thermally laminated to textiles, then durability is improved, but increasing the thickness of insulative ink reduces the textile's stretchability
Solution Approach 1:
The patent employs a thin film laminate structure where the flexible circuit layer and any insulative layers are kept sufficiently thin to maintain the stretchability of the textile substrate. The thin film provides durability during washing and flexing without significantly restricting the textile's ability to stretch.
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 highly flexible and durable conductive article that maintains conductivity over a range of stretch, suitable for integration into garments and wearable technology without breaking or significant resistance change, even after multiple wash cycles.
Implementation Method 1
The synthetic polymer membrane has a buckled orientation in the z-direction (i.e., out of the plane of the membrane)
Implementation Method 2
The electrically conductive trace may be imbibed or otherwise introduced into the pores and through the thickness of the synthetic polymer membrane
Implementation Method 3
In some embodiments, the synthetic polymer membrane is a microporous membrane having a node and fibril structure
Data Source
AI summary
The present disclosure is flexible and stretchable conductive articles that include a printed circuit and a stretchable substrate. The printed circuit contains an electrically conductive trace. The electrically conductive trace may be positioned on the surface of or be imbibed into the pores through the thickness of a synthetic polymer membrane. The synthetic polymer membrane is compressed in the x-y direction such that buckling of the membrane occurs in the z-direction. Additionally, the synthetic polymer membrane may be porous or non-porous. In some embodiments, the synthetic polymer membrane is microporous. The printed circuit may be discontinuously bonded to the stretchable substrate. Advantageously, the flexible, conductive articles retain conductive performance over a range of stretch. In some embodiments, the conductive articles have negligible resistance change when stretched up to 50% strain. The printed circuits may be integrated into garments, such as smart apparel or other wearable technology.