Engineering Science - Doctoral Theses

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Now showing 1 - 5 of 8
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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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    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.
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    High-efficiency ultrasound-powered micro-LEDs for optogenetic applications
    (University College Cork, 2023) Mondal, Tanmay; Corbett, Brian; Parbrook, Peter James; Science Foundation Ireland; Horizon 2020
    Gallium nitride (GaN) light-emitting diodes (LEDs) play the most important role in visible light applications, and more than 87% LEDs are used in indoor/outdoor lighting, automotive lighting, etc. Recent advancements in neuroscience and technology opened a new opportunity for LEDs to be used for optogenetic applications. Optogenetics is an emerging field that combines genetic engineering and light for precise control or monitoring of biological functions of cells, neurons, or organs, and µLEDs (size ≤ 100 µm) are considered the best candidate as a light source for in-vivo optogenetic applications. This work focuses on realizing a wireless ultrasound (US) powered implant-compatible device (also called neural DUSTs) enabling in-vivo electrophysiology, optogenetics, and ultra-localized drug delivery in freely moving animals. The device requires a minimum of three components: a PZT (Lead Zirconate Titanate piezoelectric material) cube to harvest the US energy, a rectifier chip for AC-DC conversion, and a µLED to deliver the optical power. The µLED should be capable of delivering a minimum of 5 mW/mm2 optical power at ~ 1 mA for activating light-sensitive proteins (Channelrhodopsin-2) while the temperature rise is < 1 oC, have an operating voltage below 3.3 V (limit of rectifier chip) and custom-made to match physical layout with rectifier. This requires the need for a highly efficient µLED. It is fortuitous that the optimum wavelength of the cation-selective membrane channel Channelrhodopsin-2 is around 470 nm where GaN material has the highest efficiency. Indium Gallium Nitride (InGaN) quantum well-based efficient blue (λpeak= 483 nm) and UV (λpeak= 371 nm) µLEDs grown on a patterned sapphire substrate (PSS) were specifically designed and fabricated with a low turn-on voltage of 2.3 V (blue) and 3.1 V (UV) which was lower than the corresponding band-gap voltage. A high wall-plug efficiency of 40.7% and 25.4% was measured from the 100 µm mesa blue and UV µLEDs, respectively. Investigation with Ag-based p-contact showed a further 20% improvement in extraction efficiency. A localized drug delivery system (DDS) based on photochromic spiropyran (SP) was characterized and developed, which activates upon exposure with 370 nm UV. The activation of DDS by ultrasound-powered and the drug release by electrically powered UV µLED were successfully demonstrated. A new dual-colour µLEDs (combinations of red, blue, and UV) on a single chip was designed and fabricated targeting dual-colour optogenetic applications. The characterization results presented here highlight challenges, issues resolved, and further improvement scope. Finally, two US-powered implant-compatible DUSTs were developed by integrating a PZT, rectifier chip, and µLED with a total volume of 2.85 mm3 (basic-DUST) and 0.33 mm3 (compact-DUST) respectively and demonstrated. To the best of our knowledge, the compact-DUST demo is the smallest implant-compatible US-powered DUST with integrated µLED. Future work should be done to achieve more efficient µLEDs, integrate DUSTs with dual colour µLEDs and develop a wafer-scale integration process.