Force sensor controlled conductive heating elements
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Solution Overview
Problem
Current conductive inks and methods for printing on flexible substrates, such as textiles, face challenges with conductivity and durability under normal stresses like bending and stretching, leading to poor performance in forming flexible electronic elements.
Innovation Solution
Development of particle-free conductive inks comprising metal complexes and conductive filler materials, which are printed using direct methods like inkjet printing and cured at low temperatures, resulting in conformal coatings that maintain conductivity and integrity through multiple strains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive inks are printed on flexible substrates using high-temperature sintering, then conductive paths are formed, but the substrate melts or deforms
Solution Approach 1:
The patent changes the curing temperature parameter from high-temperature sintering (which damages textiles) to low-temperature curing (below the melting point of textile fibers). This allows the conductive ink to form functional conductive paths without deforming or melting the flexible substrate, resolving the contradiction between achieving good conductivity and protecting the substrate from thermal damage.
2Reliability
If conventional conductive inks are used on flexible substrates, then conductive paths are formed, but conductivity decreases upon bending or stretching
Solution Approach 1:
The patent employs a flexible polymer encapsulant that forms a thin film coating over the conductive trace. This flexible shell protects the conductive path from mechanical stress during bending and stretching, maintaining conductivity stability while allowing the substrate to remain flexible and deformable.
Solution Approach 2:
The patent creates a composite structure combining the conductive ink trace with a flexible polymer encapsulant and textile substrate. This composite material system integrates the conductive functionality with the mechanical flexibility of the substrate, ensuring that conductivity is maintained under normal operational stresses like bending and stretching.
3Reliability
If force sensors are integrated into e-textiles, then gait and pressure data are captured, but the sensors become stiff and non-stretchable
Solution Approach 1:
The patent uses a flexible polymer encapsulant to coat the force sensor elements, allowing them to stretch and deform with the textile substrate while maintaining their sensing capability. This flexible thin film protects the sensor components and enables the sensors to adapt to the dynamic movements and deformations of the e-textile application.
Solution Approach 2:
The patent integrates force sensors into the e-textile using composite material structures that combine rigid sensing elements with flexible polymer and textile components. This composite approach allows the sensors to maintain their force-sensing functionality while becoming adaptable to the flexible and stretchable nature of the textile substrate.
4Reliability
If conductive strands are woven into textiles to form heating elements, then resistive heating is achieved, but the structure becomes complex and non-integral
Solution Approach 1:
The patent extracts the conductive heating element from the traditional woven strand structure and instead forms it by directly printing conductive ink onto the textile substrate. This simplifies the structure by eliminating the need for separate conductive strands and weaving processes, while maintaining the resistive heating function through the printed conductive trace.
Solution Approach 2:
The patent replaces the mechanical weaving process with a printing process. Instead of mechanically interlacing conductive strands to form heating elements, the conductive ink is deposited directly onto the textile using printing techniques, simplifying manufacturing and creating an integral heating element that is part of the substrate itself.
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 flexible electronic elements with improved conductivity and longevity, enabling the integration of force sensors and resistive heaters into textiles, offering fine-tuned control and energy efficiency.
Implementation Method 1
After deposition, the conductive inks conformally coat the substrate, and in particular, fibers of textile substrates. After curing, the conductive inks form continuous conductive coatings that comprise metal nanoparticles.
Implementation Method 2
After curing, the conductive inks form continuous conductive coatings that comprise metal nanoparticles
Implementation Method 3
U.S. Pat. No. 7,132,630 describes inclusion of conductive polyaniline fibers in the textile to provide resistive heating with an applied voltage
Implementation Method 4
U.S. Pat. Nos. 6,155,120 and 6,516,545, which describe piezoresistive pressure sensors for use on the insoles of shoes
Data Source
AI summary
Described herein are methods for forming resistive heaters and force sensing elements on a flexible substrate, and devices that include these elements to provide a force responsive conductive heater, such as a seat heater in a vehicle. The methods include printing a conductive ink on a flexible substrate that is heated to 30° C. to 90° C. before and/or during the printing process and curing the substrate to produce a conductive pattern thereon. The conductive inks generally include a particle-free metal-complex composition formulated from at least one metal complex and a solvent, and optionally, a conductive filler material.