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Paper Written By Wenfeng Shen, Xianpeng Zhang, Qijin Huang, Qingsong Xu, Weijie Song

Preparation of Solid Silver Nanoparticles for Inkjet Printed Flexible Electronics with High Conductivity. Paper Written By Wenfeng Shen, Xianpeng Zhang, Qijin Huang, Qingsong Xu, Weijie Song. Presented By Gabe Shindnes, Liza Ross, Bill Shi. Purpose. Utilize Ag nanoparticles to

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Paper Written By Wenfeng Shen, Xianpeng Zhang, Qijin Huang, Qingsong Xu, Weijie Song

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  1. Preparation of Solid Silver Nanoparticles for Inkjet Printed Flexible Electronics with High Conductivity Paper Written By Wenfeng Shen, Xianpeng Zhang, Qijin Huang, Qingsong Xu, Weijie Song Presented By Gabe Shindnes, Liza Ross, Bill Shi

  2. Purpose Utilize Ag nanoparticles to develop a method to print flexible electrical circuits. Flexible printed LED array

  3. Inkjet Printing Applications • Inkjet printing technology has been used for LED’s, photovoltaic cells, and sensors. • Smart Clothing

  4. Possible Conductors • Conductive Polymers, Graphene, Carbon • Organo-metallic compounds • Metal precursors • Metal nanoparticles Why they are not suitable for application: • Polymers, graphene and carbon have too low conductivity • Organo-metallic compounds and metal precursors require too high temperatures Remaining solution: Nanoparticles

  5. Silver Nanoparticles • Chosen for their good conductivity, low resistivity, reasonable cost and resistance to oxidation. TEM Image of Ag Nanoparticles

  6. Synthesis of Poly(acrylic acid) (PAA)-coated AgNP Silversource: silver nitrate (AgNO3) Reducingagent: Monoethanolamine (MEA) Cappingmolecule: Poly(acrylic acid) Medium: deionized water AgNO3 --->PAA coated, charged nanoparticles dispersed in aqueous solution 1. Undergo vigorous magnetic stirring for an hour 2. Heated up to 65 degrees Celsius 3. Colors vary in the sequence of yellowish, brown, orange, and dark red. 4. A black precipitate of PAA coated AgNP is collected after adding ethanol 5. Collected through funnel and washed with ethanol to remove residual MEA and PAA

  7. Inkjet Printing and Heat Treatment of Silver Patterns • Silver ink lines were printed using a common color printer • AgNP inks printed on Kodak photo paper, and polyethylene terephthalate (PET) • PET substrate was precoated with Poly(diallyldimethylammonium) chloride (PDAC) so the ink would sinter at room temperature • Kodak paper already had PDAC-like molecules • After printing, samples are heat-treated at temperatures ranging from 50-280 ℃. Then: The structural and electric properties of silver patterns are investigated

  8. Dependent Variables and Measurement Methods: • Structural characterizations (electron density, atom positions) - X ray diffraction • Particle size distribution and morphology- Transmission electron microscope • Viscosity of AgNP- Viscometer • Surface tension- Drop weight method • Electrical resistivity- 4 point probe system

  9. Results and Discussion Properties of Poly Acrylic Acid • The powder obtained from grinding solid silver NPs was observed with an X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM- results not shown with SEM), Thermogravimetric/Differential Thermal Analysis (TG/DTA) • XRD: results demonstrate that the powder was composed of well-crystallized silver NPs, and that the PAA-coated silver particles did not change after being held in the room for 3 months • Scherrer Formula ( ; formula that determines the size of particles in the form of powder) • Showed that all particles were approximately 30nm Poly Acrylic Acid

  10. Results and Discussion • TG/DTA: data showed a miniscule weight loss from room temperature to 300℃ of 0.7% • caused by the release of organic molecules from the surface of the silver NPs • 0.1% weight loss from 955℃ to 1000 ℃; caused by temperature disturbance • 99.2 % of weight was pure silver • Benefit of using silver NPs is that they can be stored at room temperature • can also be prepared as printing material by dispersing NPs with water • Silver NPs ranged from 20nm to 230nm, with mean being somewhere between 30 to 50 nm

  11. Results and Discussion TEM (Transmission Electron Microscope) Data • Data obtained from TEM on Silver NPs: • Particle size ranged from 10 - 100nm • The majority of the particles were less than 40nm • Data agrees with the data obtained from the X-Ray Diffraction (XRD) analysis Transmission Electron Microscope

  12. Results and Discussion Silver NP Ink Properties • Purpose: Produce small liquid silver droplets and to deposit them in a specific location on a substrate • Most important properties of droplets for this : Viscosity and Surface Tension • Increasing the density of Silver NPs in the liquid showed a positive correlation in both Viscosity and Surface Tension Other important properties to consider when working with non- Newtonian fluids: • Jet Velocity, Characteristic radius (radius of the orifice), and Density • Dimensionless numbers that describe these properties • Reynolds, Weber (measures spreading behavior)

  13. Results and Discussion Properties of Silver NPs • The Ohnesorge number describes the physical properties of the ink and the size of the scale • Oh ranges from 0.1 to 1.0 since Z ranges from 1 to 10 • A high Z (larger than 10) will create a large number of viscous satellite droplets • A low Z (smaller than 1) will prevent the separation of the droplets due to the viscous forces • The Z value of the silver droplets that were created (varying in weight from 10 to 25 percent) ranged from 9.94 to 7.00 which made these inks printable

  14. Results and Discussion • The printed line width was set at 1pt, equating to approximately 530μm. • If the silver nanoparticles were heated at higher temperatures, the more conductive the lines became • At higher temperature, there were less cracks, helping induce electrical conductivity • Lines were printed 14 times, with each print decreasing the resistance at an exponential rate a) Room Temperature b) 50oC c) 80oC d) 140oC

  15. Results and Discussion • Greatest resistivity difference between temperatures with only one print cycle, but decreases significantly with additional print cycles • 8μΩ cm when sintered at room temperature compared to 3.7μΩ cm at 180oC • Allows high conductivity at low temperatures • This is important because it allows for inkjet printing for paper and plastic products

  16. Conclusion: • Synthesis of PAA coated AgNPs kept at room temp. without degeneration • Low cost reaction and environmentally friendly • No centrifugation—Ideal for low cost and mass production • Lowest electrical resistivity measured was 8.0 µΩ cm → high conductivity

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