Date of Award

12-2018

Degree Name

Doctor of Philosophy

Department

Chemical and Paper Engineering

First Advisor

Dr. Alexandra Pekarovicova

Second Advisor

Dr. Paul D. Fleming

Third Advisor

Dr. Xiaoying Rong

Fourth Advisor

Dr. Veronika Husovska

Keywords

printed electronics, nickel, printing, surface free energy, surface tension, ink formulation

Abstract

Traditional printing technologies and conductive/functional inks have been integrated to print electronic devices and circuits on really think, lightweight and flexible materials in a time and cost-effective manner. Printing is an additive manufacturing technology, which selectively deposits materials only where needed to produce a wide range of devices including sensors, smart packaging, solar panels, batteries, light sources and wearable electronics. Therefore, it greatly reduces the number of required steps for manufacturing as well as the amount of waste generated relative to conventional electronic manufacturing. However, the process requirements and ink formulations to print electronics differ from graphic printing; therefore, the fundamentals and new functional ink formulations have to be rediscovered to optimize manufacturing techniques and to address cost reduction methods without compromising the functional performance. To achieve these purposes, a) a prototype thermoplastic-based nickel ink to print electrodes using a screen printing process was explored, b) optimum photonic sintering/drying conditions for nickel ink was investigated, c) an alternative conductive ink for flexography printing was developed and the effect of calendering on the electrical performance was investigated. Process fundamentals were explored, and cost reduction methods were addressed by studying the effect of substrate roughness, print direction and number of ink layers on the electrical performance of printed nickel ink. Multilayered electrodes were printed on paper and heat stabilized engineered film. A novel fundamental mechanism was found that explains the effect of substrate roughness on ink film roughness in screen printing, including the screen mesh wire roughness measurement, that is reported for the first time.

In addition, the interfaces between solid and liquids makes possible understanding of physical phenomenon of wettability, solubility, surface contamination, adsorption, absorptivity, or poor adhesion and bonding, which are linked to surface free energy of solid surfaces. There are numerous theoretical semi-empirical models for the surface free energy estimation; however, the widely-used Owens-Wendt theoretical model makes use of a series of test liquids and their contact angle on solids to estimate surface free energy of solids. Using different liquids and their known surface tension values, the model generates significantly different surface free energy values for the same substrate. A general thermodynamic inequality relating to three interfacial tensions in a three-phase equilibrium system exists in the literature. The Owens-Wendt method seldom conforms to this inequality. In this study, an interpretation of solid surfaces is presented based on physical considerations and the laws of thermodynamics, which is found to always satisfy the thermodynamic inequality with better than a 95% confidence limit.

Access Setting

Dissertation-Open Access

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