Tyndall National Institute - Doctoral Theses

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    Laser-induced graphene-like carbon for volatile organic compound sensing
    (University College Cork, 2023) Murray, Richard; Quinn, Aidan J.; Iacopino, Daniela; Science Foundation Ireland
    Laser-induced graphene-like carbon (LIG) is a potential resource-efficient fabrication route to support the abundance of sensors required by Industry 4.0 for IoT edge sensing applications, including wearables and worker safety LIG is formed \textit{in situ} by laser irradiation of suitable precursors, e.g. polyimide, to yield conductive, porous, 3D foams comprised of graphene sheetlets. This direct conversion allows for good spatial resolution (~ 50 um) and arbitrary pattern design, thus enabling the prototyping of diverse devices ranging from supercapacitors and interdigitated electrodes to electrochemical and Volatile Organic Compound (VOC) sensors. This thesis develops resource efficient, iterative system-agnostic optimisation procedures for LIG fabrication and novel back-contacting routes. Iterative use of design of experiments optimisation provides robust investigative route to determine ideal conditions with minimal investment of time and resources. An all-laser process of achieving back contacts from LIG to underlying metal was also demonstrated. Unlike current mechanical or silver paint contacts, back-contacts decouple the mechanical and electrical interface to external electronics, thus improving system reproducibility and, preventing surface contamination of the active material. Further, this scalable approach is a promising device integration route for both wafer-scale and printable electronics. Low-resource, low-power chemiresistive VOC sensors are also reported, comprised of low mass loadings of SnO nanoflowers (synthesised below 100oC and at ambient room pressure) on LIG electrodes. These offer a low-energy alternative to standard VOC sensors, which typically require high operational and fabrication temperatures (>300oC). These chemiresistive sensors can detect methanol vapor at laboratory temperature, with a limit of detection (170+/-40 ppm), below 8-hour exposure levels for worker safety (200 ppm). The sensors also demonstrated stable DC resistance responses \Delta R/R = 9+/-2% to 710 ppm of methanol for over 21 days in ambient conditions.
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    Performing women’s poetry: an evolving craft
    (University College Cork, 2023) Manning, Maria Hanora; Jenkins, Lee; Hanna, Adam; Irish Research Council
    This research project proposes to examine a current cohort of female poets employing performance techniques in their poetries, investigating how these poets continue to adapt and adopt the aesthetics of earlier poets. In recent years, the popularity of poetry in online communities has boomed, with an inevitable backlash to this poetic movement, criticising its contribution to poetry as a cultural form, such as Rebecca Watts’ PN Review article. Throughout this research, I aim to locate these poetries (often described as “digital” or “e- poetries”) along a continuum of performance, identifying the ways in which such a factor is evoked in both these new works and the work of earlier poets. Bearing in mind the theories John Miles Foley’s book Oral Literature and the Internet: Pathways of the Mind, which suggests the internet is a natural evolution of oral literature and spoken word poetries, I aim to connect the work of this cohort of poets with performance poets before them, examining the performative overlaps between oral and digital literatures. This project will interrogate the ways in which performance is enacted through a number of guises, from the sounds of orality and musicality, to the embodiment of performance by these poets. I aim to examine the creation of an aesthetic of performance among these women poets, paying particular attention to the ways the female body is performed in this work. Finally, I consider the social implications and contexts of such work, exploring the connections between poet and audience, the poetic persona and the performance of politics in these poetries. My research is primarily focused on work of poets disseminating their work chiefly through non-print methods, such as recording, performance, and social media, in the 21st Century. I will also examine the performance poetries of women poets in the 20th Century, examining the connections and creation ofa performance aesthetic, aiming to link the work of poets across these eras by examining a series of aspects of their poetics, such as the orality, the body, musicality, social engagement and public spheres of poetry.
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    Non-invasive assessment of knee condition using acoustic emission monitoring
    (University College Cork, 2023) Khokhlova, Liudmila; O'Flynn, Brendan; Tedesco, Salvatore; Dimitrios-Sokratis, Komaris; Science Foundation Ireland
    Joint disorders, in particular osteoarthritis (OA), are widespread in the older population worldwide, with the global prevalence of knee OA estimated at 27.37% for people aged 55 and older, according to Global Disease Burden Report 2019. Chronic pain and disability caused by OA pose a significant public health problem, and while late-stage disease-modifying options are mostly limited to joint replacements, OA develops over decades, allowing clinical care to potentially alter its course when timely diagnosis and early therapy are available and lifestyle changes are implemented. Multiple diagnostic methods are utilised for orthopaedic evaluation of OA, but they are frequently confined to clinical settings and need expensive equipment such as magnetic resonance imaging (MRI) and radiography, or especially qualified clinical specialists to analyse the imaging data (e.g., ultrasound). With the growing interest in tele- and personalised medicine, the methods that are suitable for such applications are actively gaining the attention of researchers. One such method is joint acoustic emission (AE) monitoring, a non-invasive method based on recording of the elastic waves within the materials during friction or deformation. While the method's feasibility and potential for use in orthopaedics have been established, the scarcity of studies investigating its reliability, the wide variation in methodologies, and the lack of a clear consensus on recording techniques and cartilage damage biomarkers are evident. The presented work is a publication-based thesis that highlights, in a series of interlinked peer-reviewed manuscripts (Appendix A), the development and evaluation of a novel, robust, and reliable non-invasive method for knee status assessment using AE monitoring. The main contribution of this thesis to this method is the establishment of new monitoring techniques that are less sensitive to motion artefacts (Section 2.2) and provide significantly improved reliability (Section 2.3) over methods investigated to date with inter-day ICCs up to 0.901, 95% CI [0.681, 0.978] for the tested number of hits per repetition. The proposed method was validated using progressive cartilage damage in a cadaver specimen (Chapter 3) that simulated OA development and allowed for the investigation related changes in knee AEs. The study led to the initial confirmation of the cause-and-effect relationship between articular cartilage damage and AE in controlled settings, where a potential impact of anatomical variations is minimal. Further validation was achieved by considering the correlations between knee AEs parameters in the general population and alternative measures of knee condition, such as self-reported knee status and functional assessments (Chapter 4), with moderate correlations (Spearman’s ρ up to 0.475, 95%CI [0.202, 0.679], p=0.001) being discovered between AEs parameters and functional test (five times sit-to-stand) results. The highest correlation scores observed for the metrics that reflect the functional state of the knee indicate a unique insight of the method into the interaction between articular surfaces during knee movement rather than static imaging. This thesis contributes to the development of joint AE monitoring from an engineering and clinical perspective. By achieving improved repeatability, this work allows for a further investigation of the method, specifically for assessment of treatment progress or disease progression, where maintaining measurements’ reliability over time is crucial. The presented evaluation of the feasibility of assessing progressive cartilage damage and correlation analysis with alternative metrics of knee condition assessment contribute to the ongoing progress of joint AE monitoring validation, confirming it’s clinical relevance and bringing it closer to clinical practice. Additionally, a link discovered between knee AEs and joint functionality points to the potential for AE monitoring to complement existing imaging techniques with unique insights into the interaction between articular surfaces during joint function. Such an understanding could prove particularly valuable in evaluating the effectiveness of disease-modifying drugs, therapies, and rehabilitation progress in future.
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    Design, modeling, analysis, and characterization of 3-D inductors for PwrSoC/PwrSiP DC-DC converters
    (University College Cork, 2023) Shetty, Chandra; O Mathuna, Cian; Ye, Liang; Duffy, Maeve; Science Foundation Ireland
    Inductors are essential components in power supplies. Increasingly, point-of-load (POL) power delivery is now the primary issue across all market sections, such as battery-powered portable electronic systems, including laptops, smartphones, tablets, etc. With increasing performance and decreasing footprint, there is a rising demand for on-chip three-dimensional (3-D) inductors. Micro inductors are used in on-chip voltage regulators, radio-frequency (RF) circuits, microsensors, microactuators, power MEMS devices, etc. The benefits of 3-D inductors such as high inductance density can be extended to such applications. This work deals with the design, modeling, and characterization of 3-D inductors for power supply applications: Power Supply in Package (PwrSiP) and Power Supply on Chip (PwrSoC) applications. Even though much work has been carried out to fabricate high inductance density 3D inductors on silicon for power applications, little or no attention has been given to (1) develop a closed-form expression for the inductance, (2) introduce novel structures for the improved figures-of-merit, and (3) dc ratio of inductance to resistance Ldc/Rdc (also known as dc quality factor Qdc). The contributions of this thesis are as follows: (1) analytical models for the inductances of 3-D inductors (toroid, solenoid, and spiral) with air-core are developed and validated by fabricating 3-D inductors on PCB, (2) a detailed study of the impact of design parameters on dc ratio of inductance to resistance (Ldc/Rdc) of 3-D micro air-core inductors is carried out and demonstrated by fabricating inductors on PCB, and (3) design, modeling, and analysis for two novel inductor topologies with magnetic thin films are presented. Followed by the introductory and literature review chapters, in the third chapter, analytical expressions for the DC inductance of four types of 3-D inductors with circular cross-section pillars (CCSP) and rectangular cross-section pillars (RCSP) are derived: (1) a toroid with CCSP; (2) a toroid with RCSP; (3) a solenoid with CCSP; and (4) a solenoid with RCSP. The inductance models are validated against numerical solutions (ANSYS Maxwell and ANSYS Q3D) and measurement results of this work as well as previously published works. The fourth chapter of the thesis focuses on the impact of design parameters such as the number of turns, pitch, height, conductor dimensions, etc. on the Qdc of different 3-D micro air-core inductor configurations. Two well-known traditional inductors are considered for the illustration: the toroid and the solenoid. Solenoid and toroid inductors are fabricated on PCB in 5 mm X 5 mm area to validate the results from Finite Element Analysis (FEA) solutions. Subsequent two chapters explore the design, inductance modeling, and analysis of two novel magnetic core inductor topologies: the fifth chapter presents a novel 3-D spiral inductor structure with magnetic thin films and the sixth chapter introduces a novel inductor structure with a coaxial cross-section of copper conductor and a single layer magnetic thin film core surrounding it. Small-signal performance of the proposed inductors compared with the previously published works to demonstrate their potential for power supply applications; the proposed inductors have the potential to achieve higher figures-of-merit (FOM). A closed-form analytical expression for the inductance, including both air-core (winding) and magnetic core (thin-films) contributions, of the novel inductor structures is derived. Finally, the seventh chapter summarises the research findings. The experimental work in this thesis focused on PCB and silicon inductors. In general, the design, analysis, and characterization methods adapted in the thesis are valid for PCB, in-silicon, and on-silicon inductors.
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    Laser-induced graphene for electrochemical sensing applications
    (University College Cork, 2023) Vaughan, Eoghan; Iacopino, Daniela; Quinn, Aidan J.; Horizon 2020
    The fabrication of laser-induced graphene (LIG) allows rapid, inexpensive patterning of electrode designs onto various substrates. LIG is a material whose properties can be tuned by altering the fabrication process, to suit the desired application. In this thesis, LIG materials were developed using a low-power hobbyist visible laser system, for electrochemical sensing applications. Polyimide (PI) was studied initially as a precursor, with the resultant LIG electrodes showing excellent electrochemical properties. Then LIG electrodes were bio-modified for the sensitive detection of Interleukin 6. Bioplastic precursors, as an alternative to PI, were explored as a potential route to green-LIG devices. Chitosan-based sheets were graphitised, and the properties of this LIG were investigated. The electron transfer rates at such electrodes are promising for future device applications. Finally, cork is used as a LIG precursor. Electrochemical cork-LIG sensors showed remarkable properties, with rapid electron transfer rates and a low detection limit for Tyrosine and dopamine. The results contained in this thesis present fast, inexpensive and eco-friendly options for LIG electrochemical sensor development.