Stretchable Silver Ink via Capillary Suspension
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Solution Overview
Problem
Current conductive elastomers face a trade-off between high electrical conductivity and high stretchability, with increasing the volume fraction of conductive solids improving conductivity but deteriorating stretchability, limiting their use in soft electronics.
Innovation Solution
A highly conductive, printable ink is developed using a capillary suspension phenomenon with 1.5 to 21 vol% conductive hydrophobic silver particles, a thermoplastic polyurethane polymer base, and a small volume of immiscible ionic liquid secondary phase, which self-assembles into a percolating network, achieving high conductivity and stretchability without compromising mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the volume fraction of conductive solids is increased to achieve high electrical conductivity, then conductivity is improved, but stretchability deteriorates
Solution Approach 1:
The invention changes the physical state of the conductive material from solid particles to liquid metal droplets, fundamentally altering the parameter of material phase. This enables the conductor to achieve high conductivity (10^-3 to 10^4 S/cm) while maintaining extreme stretchability (>1000%) because the liquid metal can flow and deform without breaking, unlike rigid solid particles that would fracture at high strain
Solution Approach 2:
The invention creates a composite material system combining liquid metal (eutectic gallium-indium or gallium-indeium-tin alloy) with an elastomeric polymer matrix. This composite structure allows the liquid metal droplets to be embedded in and move within the flexible polymer network, achieving synergistic properties of high conductivity from the metal and high stretchability from the elastomer
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 ink achieves an initial electrical conductivity of ~103 S/cm and allows for stretching beyond 1600% without mechanical failure, with samples repeatedly switching between conductive and non-conductive states, suitable for applications in sensors, soft robotics, and flexible electronics with low silver consumption.
Implementation Method 1
The ink fabrication should be compatible with state of the art unit operations and should allow for large scale production. This objective and others which will become apparent from the following disclosure, are achieved by the present invention which makes use of the capillary suspension phenomenon to design highly conductive and printable inks providing high deformability and stretchability
Implementation Method 2
a liquid primary phase comprising, as a polymer base, a thermoplastic polyurethane (TPU) dissolved in an organic polar solvent
Data Source
AI summary
The present invention relates to highly conductive, printable inks for highly stretchable soft electronics, a process for their manufacture as well as highly conductive, ultra-stretchable conductors obtainable therefrom.