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Title:Assembly and integration of two-dimensional nanomaterials for advanced interfaces and sensors
Author(s):Choi, Jonghyun
Director of Research:Nam, SungWoo
Doctoral Committee Chair(s):Nam, SungWoo
Doctoral Committee Member(s):Aluru, Narayana R.; Li, Xiuling; Kim, Seok
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):2D materials
3D structures
Abstract:Nanomaterials have been extensively investigated by the research community owing to their extraordinary properties and functionalities that significantly surpass their bulk counterparts. Among a variety of nanomaterials, two dimensional (2D) nanomaterials, represented by graphene and transition metal dichalcogenides (TMDCs), have captivated academic and industrial attentions because of their promise in future electronics, surface coating, biosensing, as well as the compatibility with the scalable and low-cost, top-down fabrication process. In this dissertation, I further explore the potentiality of 2D materials as an advanced surface and field-effect transistor (FET)-based biochemical sensing platform, and investigate electrical double layer (EDL) formation on 2D materials. First, I present various three-dimensional (3D) integration techniques of 2D materials that exhibit promise as a biosensing platform, tunable wetting surface, and stretchable electronic device. I demonstrate that 2D materials could be integrated with 3D microstructure substrates with a novel and simple substrate engineering technique that utilizes solvent-induced swelling of substrates. In addition, I report on developing flower-like structures (i.e., nanoflowers) of molybdenum disulfide (MoS2) grown by metal-organic chemical vapor deposition (MOCVD), and further demonstrate dual-scale hierarchical structures by introducing additional buckle-delamination induced microscale crumples using a shape-memory polymer. Moreover, I achieve bio-inspired hierarchical structures of graphene by combined use of 3D microstructure substrates and mechanically-driven nanoscale crumples of graphene, which exhibit a potential for a highly sensitive biochemical sensor platform. Second, I investigate graphene FETs for an advanced electrophysiological study, as well as for the understanding of EDL formation on atomically-thin materials. I demonstrate simultaneous electrical recording of controlled and stimulated behaviors of optogenetically encoded skeletal muscle cells and neurons. The recorded electrical signals corresponded well with the stimulation patterns of optogenetically encoded cells, demonstrating the successful real-time and simultaneous sensing of extracellular action potentials from target cells based on graphene FETs. Furthermore, I study how the EDL, which is an essential component for top solution-gated FETs and biosensors, is affected by the surface properties of underlying substrates beneath graphene. Hydrophobic substrates are demonstrated to disrupt the EDL formation on graphene, which is evidenced by transconductance measurements by FETs, capacitance measurements by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), as well as molecular dynamics (MD) simulations. This thesis represents significant advancements in assembly and integration of 2D materials for diverse novel applications as well as fundamental scientific research. Our results offer unique strategies toward superlative surface coatings, stretchable electronics, and biosensors, and suggest the substantial promise toward scientific breakthroughs in electrophysiology and EDL based on 2D materials.
Issue Date:2018-04-19
Rights Information:Copyright 2018 Jonghyun Choi
Date Available in IDEALS:2018-09-04
Date Deposited:2018-05

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