Stabilized Silver Nanoparticle Inks for High-Aspect-Ratio Electrodes
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Solution Overview
Problem
Current printing techniques, such as inkjet printing, are limited in producing self-supporting electrodes with high aspect ratios and microscale features due to nozzle clogging and low solid loading of metallic inks, while direct ink writing requires high concentration and stiffness of silver particle inks that are challenging to stabilize and disperse effectively.
Innovation Solution
Development of stabilized silver particles with a combination of short-chain and long-chain anionic polyelectrolytes as capping agents, achieving a high solid loading of at least 50 wt % and shear-thinning properties, allowing for the creation of conductive silver particle inks that can be used for direct ink writing to form self-supporting, bendable, and stretchable electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional inkjet printing uses diluted liquid inks, then printing process is simple, but solid loading is low and self-supporting electrodes cannot be formed
Solution Approach 1:
The patent changes the physical state parameter of the ink from liquid to paste form, and increases solid loading from typical diluted concentrations to at least 50 wt%. This parameter transformation enables the ink to form self-supporting electrodes while maintaining printability through the shear-thinning rheological behavior.
Solution Approach 2:
The patent creates a composite ink system combining metallic particles (silver, copper, or their alloys) with a specific binder composition containing short-chain and long-chain anionic polyelectrolytes. This composite structure provides both high solid loading and the necessary rheological properties for direct ink writing.
2Strength
If high concentration silver particle inks are used for direct ink writing, then self-supporting electrodes can be formed, but particle agglomeration occurs and stability is reduced
Solution Approach 1:
The patent uses a composite binder system with dual polyelectrolyte components: short-chain anionic polyelectrolyte (e.g., polyacrylic acid, polyacrylamide) and long-chain anionic polyelectrolyte (e.g., polyvinyl alcohol, carboxymethyl cellulose). This composite approach provides both steric and electrostatic stabilization, preventing particle agglomeration while maintaining high solid loading for self-supporting electrode formation.
Solution Approach 2:
The binder composition acts as an intermediary between the metallic particles and the substrate, providing steric and electrostatic barriers that prevent particle-particle interactions that would lead to agglomeration. The dual polyelectrolyte system mediates particle stabilization through combined short-range and long-range repulsive forces.
3Reliability
If large particle commercial metallic pastes are used, then conductivity is achieved, but nozzle clogging occurs and microscale patterning is impossible
Solution Approach 1:
The patent changes the particle size parameter from commercial paste sizes (0.1-10 μm) to nanoscale dimensions (1-100 nm). This size reduction eliminates nozzle clogging and enables microscale patterning while maintaining electrical conductivity through the high surface area to volume ratio and efficient particle packing in the shear-thinning paste formulation.
4Shape
If low solid loading inks are used for inkjet printing, then fluidity is maintained, but aspect ratio is limited and self-supporting structures cannot be created
Solution Approach 1:
The patent transforms the ink from liquid to paste form, changing the flow behavior parameter from Newtonian to shear-thinning non-Newtonian fluid. This parameter change allows the material to maintain fluidity during extrusion (enabling high aspect ratio structures) while containing at least 50 wt% solids for self-supporting capability after deposition.
Solution Approach 2:
The patent introduces dynamic rheological behavior through shear-thinning properties, where the ink is fluid under shear stress during extrusion (allowing high aspect ratio feature formation) but becomes rigid upon deposition (enabling self-supporting structures). This dynamic transition is achieved through the specific binder composition with dual polyelectrolytes.
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 silver particle inks enable the reliable printing of self-supporting, high-aspect-ratio electrodes with low resistivity and excellent adhesion to various substrates, including flexible and stretchable materials, facilitating the production of complex electronic devices with low temperature processing.
Implementation Method 1
stabilized silver particles are provided which contain particles comprising silver, a short-chain capping agent adsorbed on the particles, and a long-chain capping agent adsorbed on the particles
Implementation Method 2
The silver particle ink is shear thinning
Data Source
AI summary
Stabilized silver particles comprise particles comprising silver, a short-chain capping agent adsorbed on the particles, and a long-chain capping agent adsorbed on the particles. The short-chain capping agent is a first anionic polyelectrolyte having a molecular weight (Mw) of at most 10,000, and the long-chain capping agent is a second anionic polyelectrolyte having a molecular weight (Mw) of at least 25,000. The stabilized silver particles have a solid loading of metallic silver of at least 50 wt %.