Cold-Sprayed Flexible Electrodes Without Annealing or Vacuum
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Solution Overview
Problem
Conventional manufacturing methods for flexible electronics face challenges in achieving ultra-fine patterning without dedicated masks and vacuum equipment, leading to low adhesion strength, poor conductivity, and high-temperature post-annealing processes that compromise the use of low-thermal budget substrates like PET and PEN.
Innovation Solution
A cold spray technique combined with femtosecond laser machining and ultrasonic welding is used to metallize flexible polymers, enabling high-resolution, mask-free, and vacuum-free production of flexible electronics with excellent conductivity and adhesion strength, without the need for high-temperature sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional printing methods (inkjet, screen printing, gravure printing) are used to deposit functional coating materials, then the manufacturing process is simple and equipment cost is low, but the adhesion strength is low and conductivity is poor
Solution Approach 1:
The patent changes the deposition parameters by using cold spray technology with high-velocity particle impact (supersonic or hypersonic speeds) to achieve strong adhesion and high conductivity without high temperature. The kinetic energy of particles is converted to bonding energy, creating metallurgical bonds at room temperature or low temperature, thus resolving the contradiction between simple manufacturing and high reliability.
Solution Approach 2:
The patent replaces the traditional thermal field (high-temperature sintering) with a mechanical field (high-velocity particle impact). The cold spray process uses kinetic energy of accelerated particles to achieve bonding, substituting the thermal-mechanical process with a purely mechanical impact process, enabling strong adhesion without high temperature exposure.
2Reliability
If high-temperature post-annealing (calcining or sintering) is applied to increase adhesion strength and conductivity, then the electrical conductivity and adhesion strength improve, but the manufacturing cost increases and oxidation of functional coatings occurs
Solution Approach 1:
The patent performs the bonding action during the deposition process itself rather than requiring a subsequent annealing step. The cold spray process achieves strong adhesion and good conductivity directly through high-velocity particle impact, eliminating the need for post-deposition thermal treatment. This preliminary action during deposition resolves the contradiction by achieving high reliability without additional high-temperature processing.
Solution Approach 2:
The patent converts the typically harmful effect of high-temperature oxidation into a benefit by operating at low or room temperature. The cold spray process uses the kinetic energy of particles to achieve bonding without thermal exposure, preventing oxidation of functional coatings while maintaining high adhesion strength and conductivity, thus eliminating the trade-off between performance and oxidation prevention.
3Reliability
If high-temperature post-annealing is used to enhance adhesion and conductivity, then the electrical performance improves, but the use of low-thermal budget substrates (PET, PEN) is limited
Solution Approach 1:
The patent changes the temperature parameter from high (post-annealing) to low or room temperature during deposition. This parameter change enables the use of low-thermal budget substrates like PET and PEN that cannot withstand high temperatures, while still achieving high adhesion strength and conductivity through the kinetic energy mechanism of cold spray, thus resolving the contradiction between performance enhancement and substrate compatibility.
Solution Approach 2:
The patent replaces the thermal field (high-temperature annealing) with a mechanical field (particle impact). This substitution removes the thermal constraint that limits substrate selection, allowing low-thermal budget flexible substrates to be used while achieving high reliability through mechanical bonding during cold spray deposition.
4Device complexity
If conventional printing methods are used without dedicated masks and vacuum equipment, then the device complexity and cost are reduced, but the patterning precision and spatial resolution are insufficient
Solution Approach 1:
The patent replaces the complex vacuum and mask system with a direct digital cold spray deposition system. The high-velocity particle jet can be precisely controlled and directed to create fine patterns without physical masks or vacuum chambers, achieving ultra-fine patterning through digital control of the spray system while maintaining low device complexity.
Solution Approach 2:
The patent transitions from planar contact printing to a three-dimensional particle jet deposition approach. The cold spray process deposits particles through a focused jet that can be precisely positioned in three-dimensional space, enabling ultra-fine patterning without the constraints of flat mask contact, thus achieving high precision without increased equipment complexity.
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 method achieves high electrical conductivity (1.08×10^6 S·m^-1) and adhesion strength, along with flexibility (60% elongation), suitable for low-thermal budget substrates, and allows for rapid, scalable, and cost-effective production of high-performance flexible electronics.
Implementation Method 1
cold spray metallization; (1) cold spray metallization; First, the flexible polymer (such as PET) surface is metallized by cold spray direct writing of tin (Sn) particles
Implementation Method 2
femtosecond laser machining; (2) femtosecond laser machining; The as-metallized polymer film is then precisely cut into custom designed high-resolution electrodes
Implementation Method 3
ultrasonic welding; (3) ultrasonic welding; Lastly, the laser-cut electrodes are joined onto a base polymer substrate via ultrasonic welding
Data Source
AI summary
A flexible electrode device, including a typically thin film polymer layer, a typically thin film metal layer bonded to the polymer layer to yield a composite strip, and a polymer substrate ultrasonically welded to the composite strip to yield a flexible electrode device. The flexible electrode device exhibits electrical conductivity of at least 1.08×106 S·m−1, at least 60% tensile elongation, and less than 5% change in the R/R0 after 50 peeling cycles. The flexible electrode is formed without annealing and is formed under ambient pressure and temperature conditions. The flexible electrode device can have any convenient shape.