Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Mechanical and Materials Engineering

Supervisor

Yang, Jun

Abstract

The accelerating arrival of the Internet of Things (IoT) era creates a rapidly growing demand for printed electronic. As a low-cost and green substrate, cellulose paper has become the most attractive choice for the printing of sustainable and disposable electronics. However, manufacture of high quality circuits with high conductivity on cellulose paper remains a challenge due to the substrate’s high porosity and roughness. In this thesis, a method for facile fabrication of hybrid copper-fiber highly conductive features on low-cost cellulose paper with strong adhesion and enhanced bending durability is introduced. With three-dimensional electroless deposition (ELD) of copper, the as-fabricated circuits show ultra-low sheet resistance down to 0.00544 Ω/sq. Taking advantages of the porous structure of paper, together with the precise control of the inkjet droplets, highly conductive vertical interconnected accesses (VIAs) are fabricated for multilayered devices without physically drilling holes or depositing additional dielectric material. To further utilize the unique porous structure of cellulose paper, a scalable fabrication method for flexible, binder-free and all-solid-state supercapacitors is proposed based on the low-cost chemical engraving technique, to construct CuxO nanostructure in-situ on the three-dimensional metallized cellulose fiber structures. Benefitting from both the “2D Materials on 3D Structures” design and the binder-free nature of the fabricated electrodes, substantial improvements to electrical conductivity, aerial capacitance, and electrochemical performance of the resulting supercapacitors (SCs) are achieved, fulfilling the increasing demand of highly customized power systems in the IoT and wearable electronics industries. The above-mentioned work all use inkjet printing for materials deposition. However, as a solvent-based printing technique, inkjet printer has strict requirement of ink properties and suffer from inevitable nozzle clogging. To address these challenges, a fabrication method based on solvent-free laser printing technique is proposed, pushing the manufacture of printed electronics towards an environmentally benign and more cost-efficient manor. Lastly, a one-step react-on-demand (RoD) method for fabricating flexible circuits with ultra-low sheet resistance, enhanced safety and durability is proposed. With the special functionalized substrate, a real-time synthesize of the 3D metal-polymer (3DMP) conductive structure is triggered on demand. The as-fabricated silver traces show an ultralow sheet resistance down to 4 mΩ/sq.

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