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202602 https://hdl.handle.net/2286/R.2.N.202602 http://rightsstatements.org/vocab/InC/1.0/ All Rights Reserved 2025 152 pages Doctoral Dissertation Academic theses en Dou, Yan Nian, Qiong Q.N Milcarek, Ryan R.M Azeredo, Bruno B.A Zhuang, Houlong H.Z Arizona State University Partial requirement for: Ph.D., Arizona State University, 2025 Field of study: Materials Science and Engineering Additive manufacturing has emerged as a versatile and rapidly advancing platform for the fabrication of electrochemical sensors, offering unparalleled design flexibility, rapid prototyping, minimal waste, and cost efficiency. Despite these advantages, conventional 3D-printed electrodes often suffer from limited electrochemical activity, suboptimal material conductivity, and reproducibility challenges, which hinder their adoption in real-world applications. This dissertation presents an integrated framework that combines material innovation, advanced surface engineering, and modular device architecture to overcome these limitations and enable high-performance, portable sensing systems. Conductive electrodes were fabricated via fused deposition modeling (FDM) and subsequently enhanced through approaches such as reduced graphene oxide coating and copper-driven laser graphitization, which markedly improved surface conductivity, catalytic activity, and electrochemical capacitance. Comprehensive characterization using scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, contact angle analysis, and electrochemical measurements demonstrated that these modifications yielded up to sixtyfold increases in hydrogen peroxide sensitivity, enabled near-Nernstian responses for ion detection, reduced potential drift, and optimized response time and detection limits. A modular sensor platform with replaceable working electrodes was developed, allowing straightforward customization of solid-contact layers using graphene, reduced graphene oxide, and graphene oxide, thereby enabling precise tuning of capacitance, hydrophobicity, and sensing performance for diverse analytes. Integration with portable smartphone-based potentiostat further allowed real-time, on-site detection, and field trials confirmed reliable measurements of hydrogen peroxide and i potassium ions in complex matrices such as agricultural soils. Collectively, this work delivers a scalable, customizable, and reproducible strategy for manufacturing next generation 3D-printed electrochemical sensors. By bridging additive manufacturing with tailored materials engineering and modular design, it establishes a foundation for versatile analytical platforms with broad potential in environmental monitoring, precision agriculture, healthcare diagnostics, and other point-of-need applications, paving the way for wider deployment of high-performance 3D-printed sensing technologies. Materials Science Smart Electrochemical Sensors via Additive Manufacturing and Graphene Interfaces for Portable and Selective Detection