Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Aeronautical and Aviation Engineering | en_US |
| dc.contributor.advisor | Zou, Fangxin (AAE) | en_US |
| dc.creator | Guo, Shuting | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/14615 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Three-dimensional graphene foams for stretchable electronics : from electrical transport analysis to multifunctional material systems | en_US |
| dcterms.abstract | Stretchable electronics are revolutionizing fields such as wearable health monitoring, soft robotics, and human-machine interfaces by enabling flexible and adaptable devices. Among various materials, three-dimensional (3D) graphene-based foams (GFs) have emerged as outstanding candidates due to their excellent electrical, thermal, and mechanical properties, along with superior multidirectional flexibility. Derived from two-dimensional (2D) graphene, GFs retain its intrinsic advantages while offering structural benefits crucial for stretchable applications. This thesis advances the understanding, modeling, and application of GFs in stretchable electronics through three complementary studies that collectively build a coherent framework from fundamental mechanisms to multifunctional devices and predictive modeling. | en_US |
| dcterms.abstract | First, we investigate the stretch-induced tunability of electrical transport properties of GFs. Pre-stretching modulates the temperature-dependent resistivity of GFs, potentially shifting the response from negative to positive temperature dependence. A conduction network model, representing GF as interconnected polycrystalline graphene islands and junctions, captures multiple transport mechanisms, including thermally activated conduction across grain boundaries, phonon-limited conduction within islands, and fluctuation-induced tunneling across junctions, explaining how pre-strain alters temperature-dependent resistivity through changes in island number, junction distribution, and transport gaps. | en_US |
| dcterms.abstract | Building on this mechanistic insight, we design a multifunctional GF/single-walled carbon nanotubes (SWNT)/polydimethylsiloxane (PDMS) composite to overcome temperature-induced artifacts and achieve multifunctionality. In this system, a spray-coated SWNT/PDMS layer bridges graphene skeletons, forming a hierarchical conductive network. The composite demonstrates controllable strain sensitivity, temperature-compensated resistance change, and additional temperature and pressure sensing capabilities. These properties are tunable via SWNT loading in PDMS and coating thickness of SWNT/PDMS layer, enabling the integration of GF-based devices with decoupled, multifunctional sensing modes. Compared to conventional GF/PDMS composites, the hybrid system achieves versatile functionality for wearable applications. | en_US |
| dcterms.abstract | Finally, to systematically optimize GF piezoresistive performance, we establish a microstructure-informed multiscale framework that bridges atomic-scale features with macroscopic device behavior. At the atomic scale, density functional theory (DFT) simulations reveal the transport properties of pristine graphene and grain boundaries under strain, clarifying the role of crystallographic asymmetry and defect configurations. At the network level, Monte Carlo simulations capture mesoscale grain size effects and junction distributions, linking microscopic transport characteristics to macroscopic piezoresistive response. Importantly, the framework identifies which microstructural factors persist across scales and which are naturally averaged out within the foam network. By combining simulations with experimental validation through controlled pre-stretching, we demonstrate how targeted microstructural engineering can enhance gauge factors and enable predictive design of high-performance GF-based strain sensors. | en_US |
| dcterms.abstract | Together, these studies establish a unified framework for advancing GFs in stretchable electronics: from uncovering the fundamental transport mechanisms in GFs, to engineering multifunctional composites, to building a predictive modeling framework for tailoring microstructure and enhancing piezoresistive performance. The findings provide both scientific insights and practical strategies for advancing 3D graphene-based materials toward next-generation stretchable and wearable electronics. | en_US |
| dcterms.extent | xxxviii, 219 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2026 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.accessRights | open access | en_US |
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