Particle-Free Adhesive Gold Inks for Flexible Electronics
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Solution Overview
Problem
Existing conductive inks for printed electronics face challenges such as insufficient conductivity, poor adhesion to substrates, high sintering temperatures, and stability issues, limiting their use in flexible and cost-effective applications.
Innovation Solution
Development of particle-free adhesive gold inks comprising a gold complex with specific ligands and a mixed solvent system, allowing for the formation of conductive films with high conductivity and good adhesion at lower temperatures, suitable for various deposition methods and substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nanoparticle-based conductive inks are used to achieve electrical conductivity, then conductivity is improved, but sintering temperature increases and substrate selection is limited
Solution Approach 1:
The patent changes the physical state parameter of gold from particulate (nanoparticles) to molecular (complexes), enabling decomposition at lower temperatures while maintaining conductivity. The gold complexes decompose between 150-250°C, significantly lower than the sintering temperatures required for nanoparticle inks, thus resolving the contradiction between achieving conductivity and limiting sintering temperature.
Solution Approach 2:
The patent uses molecular gold complexes as a precursor that copies the desired conductive function without requiring high-temperature sintering. The complexes decompose to form conductive gold structures at lower temperatures, effectively copying the conductivity function of sintered nanoparticles while avoiding the high-temperature process.
2Stability of the object's composition
If polymeric stabilizers are added to prevent particle aggregation, then storage stability is improved, but viscosity increases and conductivity decreases
Solution Approach 1:
The patent extracts and eliminates polymeric stabilizers from the ink formulation by using molecular gold complexes instead of particulate gold. The complexes are inherently stable in solution without requiring additional polymeric additives, thus removing the source of high viscosity while maintaining storage stability.
Solution Approach 2:
The patent uses small molecular weight ligands (such as carboxylic acids, alcohols, or amines) that are volatile and can be removed by heating, leaving behind pure gold structures. These temporary stabilizing molecules serve their purpose during storage and processing then decompose, avoiding the permanent viscosity increase caused by polymeric stabilizers.
3Reliability
If conventional conductive inks are used, then conductivity is achieved, but adhesion to substrates is poor
Solution Approach 1:
The patent creates a composite molecular structure where gold is coordinated with specific ligands that provide both electrical conductivity and substrate adhesion. The ligand-gold complex formulation integrates multiple functions (conductivity and adhesion) into a single material system, eliminating the need for separate adhesive layers required by conventional nanoparticle inks.
Solution Approach 2:
The ligands in the gold complexes act as intermediaries that facilitate adhesion between the gold and the substrate. These molecular mediators provide bonding groups that interact with both the gold center and the substrate surface, enabling strong adhesion without requiring separate adhesive polymers.
4Reliability
If high metal content is used to achieve conductivity, then electrical performance is improved, but ink stability decreases and particle aggregation occurs
Solution Approach 1:
The patent changes the concentration parameter from high nanoparticle loading to moderate molecular complex concentration. The molecular complexes remain stable at higher concentrations without aggregating because they are solvated by ligands, allowing high gold content (20-40 wt%) while maintaining ink stability and preventing particle aggregation.
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 highly conductive, adhesive, and stable gold inks that can be easily printed on flexible substrates, overcoming the limitations of traditional inks by enabling scalable and automated production of flexible electronics with improved longevity and conductivity.
Implementation Method 1
wherein the first ligand volatilizes upon heating at a temperature of 200° C. or less
Implementation Method 2
the ink shows a single sharp decomposition transition beginning at a temperature of 200° C. or less
Data Source
AI summary
Described herein are adhesive gold inks, and methods for making and depositing these inks to form conductive traces. The adhesive gold inks generally contain a gold complex dissolved in a mixed solvent system including at least a diol and an amine. The mixed solvent system may further include a thioalkyldiol. The gold complex includes a first ligand and a second ligand. The first ligand may be a thioether, a phosphine, or an amine that volatilizes upon heating at a temperature of 200° C. or less. The second ligand may be a halide or a carboxylate. The adhesive gold inks are clear and particle-free and may be formulated for deposition by a wide range of printing methods on both flexible and non-flexible substrates.