Semester

Fall

Date of Graduation

2011

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Konstantinos A. Sierros

Committee Co-Chair

Darran R. Cairns

Committee Member

Edward M. Sabolsky

Abstract

The ability to atmospherically deposit conductive patterns on flexible polymeric substrates has recently gained considerable interest as an alternative to vacuum processes. This is because it can potentially lead to highly efficient and reliable transparent electrode components that can be used in lightweight and flexible optoelectronic devices such as sensors, solar panels, touch screens, displays and solid state lighting. Common approaches to fabricate transparent conductors include the physical deposition of transparent conductive oxide (TCO) films on polymer substrates. This is leading to mechanically brittle components which are fabricated using costly vacuum coating equipment. It is therefore important to research an alternate route for depositing mechanically reliable conductive structures on unheated flexible substrates.;Metallo-organic decomposition (MOD) inks formulate a metal-organic precipitate beginning with the reduction of metal salt precursor which is then combined with an organic solvent. The ink can then be deposited using various processes such as syringe writing, spray masking, screen printing and ink-jet printing. Low-temperature curing can be achieved without compromising the functionality of the polymer substrate leading to a ductile conductive pattern.;In this work, a MOD ink was formulated by the reduction of silver nitrate (AgNO3) to yield silver octanoate (AgC8H15O 2) precipitate which is then combined with xylene (C8H 10) solvent. Deposition on polymer base substrates was performed using masking techniques and involving a small gauge needle tip luer-lock syringe or a spray gun. Relatively uniform Ag track surface geometries were obtained. Contact angle measurements (<17°) showed good adhesion of the Ag ink on the PEN substrate. Curing of the Ag patterns was performed via radiation-conduction-convection heating at temperatures as low as 150°C yielding electrical resistivities as low as 4.13x10-6O·m, with higher temperatures offering electrical resistivities as low as 3.01x10 -7O·m. Monotonic tensile testing of the cured samples was performed at a cross-head speed of 1 mm/min resulting in a marginal change in resistance up to 10% strain. Cyclic mandrel testing was conducted in order to assess the fatigue characteristics of the flexible components. Nanoindentation testing was performed to analyze mechanical properties of the cured ink in relation to curing temperature. Finally, nanoscratch testing showed good adhesion of the cured ink to the PEN substrate. Surface porosity was related to all mechanical and electromechanical testing.;Hybrid organic/inorganic flexible structures allow for the atmospheric deposition of ductile conductive components unlike current applications requiring vacuum deposition of films that need further patterning.

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