UWSpace

UWSpace is the University of Waterloo’s institutional repository for the free, secure, and long-term home of research produced by faculty, students, and staff.

Depositing Theses/Dissertations or Research to UWSpace

Are you a Graduate Student depositing your thesis to UWSpace? See our Thesis Deposit Help and UWSpace Thesis FAQ pages to learn more.

Are you a Faculty or Staff member depositing research to UWSpace? See our Waterloo Research Deposit Help and Self-Archiving pages to learn more.

Photo by Waterloo staff

Communities in UWSpace

Select a community to browse its collections.

Recent Submissions

  • Thumbnail Image
    Item type: Item ,
    Use of atmospheric pressure spatial chemical vapor deposition to create spatially variant metal oxide semiconductor films for use in gas sensing arrays
    (University of Waterloo, 2026-01-21) Saini, Agosh Singh
    Manufacturing gas sensor arrays is a key roadblock in commercially viable electronic nose systems as sensor arrays require large numbers of unique sensors. Atmospheric-pressure spatial chemical vapor deposition (APSCVD) is a fabrication method that can be utilized to lower manufacturing costs. In this thesis, APSCVD is used to create gradients of sensing materials which are then used to create an array of sensors with unique physical properties. Materials explored using APSCVD are SnO2 thickness gradients, SnO2 and Cu2O heterojunction gradients, and zinc-tin-oxide composition gradients. These materials are created using a combination of a stainless steel atmospheric-pressure spatial atomic layer deposition reactor head and a custom APSCVD reactor head designed to create metal-oxide-semiconductor thin films with physical property gradients. The custom APSCVD reactor head implements a substrate-reactor spacing gradient to achieve physical property gradients, building upon a previous work showcasing that tilting a stainless steel reactor head leads to a thickness gradient [1], [2]. The heterojunction gradient consists of a uniform Cu₂O layer with a thickness of ~103 nm and a SnO₂ layer with a thickness gradient from ~22 nm to ~12 nm, measured using ellipsometry. The ellipsometry thickness measurements show an R² value of 0.95. The energy-dispersive x-ray spectroscopy measurements of the composition gradient film show the tin to zinc ratio ranging from 0.86 to 0.21 with a R² value of 0.96. The fabricated gradient films are converted to sensors using photolithography. Interdigitated electrodes are fabricated on the top surface, and chips with 8 sensors are placed on chip carriers. A custom gas sensor testing system is created to continuously run experiments and generate response data. The test system consists of control software for heating, an Arduino-based relay for recording up to 8 sensors at a time, and mass flow controllers which auto adjust to cycle through different experiments and analytes. Ethanol, isopropyl alcohol, acetone, and water are used as analytes in this thesis. The data recorded showcases that APSCVD can be used to create functional gas sensors with thickness, heterojunction, and composition gradients. The composition gradient exhibits a response-direction inversion, resulting in an increase in resistance at room temperature and a decrease at 200 °C. Additionally, heterojunction gradient showcases a parabolically varying response across the film. Principal component analysis of heterojunction gradient sensor data shows that combining multiple sensors improves selectivity relative to individual sensors, as reflected by an increase in silhouette score from -0.02 to 0.38, corresponding to a transition from overlapping to distinct response clustering.
  • Thumbnail Image
    Item type: Item ,
    Recovery and Reuse of Nanomaterials from Radically Polymerizable Thermoset Nanocomposites; Towards A Circular Economy
    (University of Waterloo, 2026-01-21) Rezaei, Zahra
    The widespread adoption of thermoset nanocomposites has created significant end-of-life management challenges due to their permanent crosslinked networks, which resist conventional recycling methods and trap valuable nanomaterials within non-degradable matrices. This work presents a proof-of-concept study to assess a new approach for achieving a circular economy for thermoset nanocomposites; recovering and reusing nanomaterials from thermoset nanocomposites through the incorporation of cleavable comonomers into the polymer matrix, enabling controlled matrix degradation and nanofiller recovery at end-of-life. Carbon nanotubes (CNTs) were selected as the nanofiller for this study due to their widespread use in nanocomposites and growing industrial significance, and a styrene/divinylbenzene (DVB) thermoset matrix was chosen as a model matrix for its chemical compatibility with CNTs. To enable controlled degradation at end-of-life and nanofiller recovery, comonomer additives that can install cleavable bonds into the matrix’s polymer network were systematically evaluated. Several candidates were investigated, including cyclic ketene acetal (CKA) (specifically 2-methylene-1,3-dioxepane, MDO), which underwent hydrolysis too rapidly and an unwanted ring-retaining side reaction for practical application, and thionolactones (specifically dibenzo[c,e]-oxepine-5(7H)-thione, DOT and 2-(isopropylthio)dibenzo[c,e]oxepine-5(7H)-thione, 2SiPrDOT), which was limited by the monomers’ solubility in the styrene/DVB system. Through this careful screening process, 2SiPrDOT was selected as the most suitable option, offering both chemical stability during processing and sufficient solubility in the system. Comprehensive characterization of the primary nanocomposites using thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), electrical resistivity measurements, and hardness testing confirmed that 2SiPrDOT incorporation did not significantly alter the thermal, electrical, or mechanical properties of the material, preserving the high-performance characteristics essential for practical applications. The thermoset matrix was then deconstructed through nucleophilic degradation, allowing recovery of finely distributed CNTs from the crosslinked network. Analysis of recovered CNTs using energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and Raman spectroscopy revealed no significant changes in the nanofiller’s structure or surface chemistry, demonstrating the gentle nature of the recovery process. The recovered CNTs (68.7% yield) were subsequently re-embedded into a fresh styrene/divinylbenzene matrix and polymerized. Characterization of these secondary nanocomposites using the same characterization techniques showed properties comparable to the primary nanocomposites, confirming successful retention of nanofiller functionality through the recovery and reuse cycle. This research demonstrates that strategic incorporation of cleavable comonomers into thermoset matrices offers a viable pathway toward circularity for high-performance nanocomposites. By enabling controlled matrix deconstruction while preserving nanomaterial quality, this approach addresses both environmental concerns associated with nanocomposite waste and the economic imperative to reclaim valuable nanomaterials. The demonstrated success with the styrene/DVB system suggests broader applicability of this methodology. As a general radical ring-opening polymerization strategy, this approach has the potential to be extended to other vinyl-based thermosets and diverse nanofillers, offering a promising foundation for developing next-generation recyclable composites across multiple industrial sectors.
  • Thumbnail Image
    Item type: Item ,
    Categories as a Foundation for both Learning and Reasoning
    (University of Waterloo, 2026-01-21) Shaw, Nolan
    This thesis explores two distinct research topics, both applying category theory to machine learning. The first topic discusses Vector Symbolic Architectures (VSAs). I present the first attempt at formalising VSAs with category theory. VSAs are built to perform symbolic reasoning in high-dimensional vector spaces. I present a brief literature survey demonstrating that the topic is currently completely unexplored. I discuss some desiderata for VSA models, then describe an initial formalisation that covers two of the three desiderata. My formalisation focuses on two of the three primary components of a VSA: binding and bundling, and presents a proof of why element-wise operations constitute the ideal means of performing binding and bundling. The work extends beyond vectors, to any co-presheaves with the desired properties. For example, GHRR representations are captured by this generalisation. The second line of work discusses, and expands upon, recent work by Milewski in the construction of "pre-lenses." This work is motivated by pre-established formalisations of supervised machine learning. From the perspective of category theory, pre-lenses are interesting because they unify the category Para, or Learn, with its dual co-Para, or co-Learn. From a computer science perspective, pre-lenses are interesting because they enable programmers to build neural networks with vanilla function composition, and they unify various network features by leveraging the fact that they are profunctors. I replicate Milewski's code, extend it to the non-synthetic data, MNIST, implement re-parameterisations, and describe generative models as dual to discriminative models by way of pre-lenses. This work involved creating a simple dataloader to read in external files, randomising the order that inputs are presented during learning, and fixing some bugs that didn't manifest when training occurred on the very small dataset used by Milewski.
  • Thumbnail Image
    Item type: Item ,
    Duped by Dream Sellers: A Case Study of Student Immobility, Precarity, and Profit in Northern Cyprus
    (University of Waterloo, 2026-01-21) Lariani, Aicha
    Young migrants arrive in Northern Cyprus seeking opportunity and safety through international higher education. Instead, they find themselves in a state of continuous precarity as financial benefactors sustaining complex legal liminalities of a de facto state. What happens when systemic marketing of an affordable, internationally recognized education and work opportunities targets individuals from countries in active war, extreme poverty, and political unrest? With safety concerns in their home countries, low-ranking passports, and limited international options, student migrants continue to arrive in Northern Cyprus despite its difficult living conditions. Drawing on 29 qualitative interviews, this thesis examines how student migration both responds to and sustains the political and economic structures of Northern Cyprus. It shows how education, labour, and legality intertwine to produce a system that depends on students’ presence and their restricted mobility. By situating student migration within the political economy of an unrecognized state, this thesis contributes to empirical research on the governance of mobility and the production of precarity for non-elite, de facto refugee students, facilitated through higher education and its institutions.
  • Thumbnail Image
    Item type: Item ,
    A Game of Urban Resilience: Playing the Social-Ecological System of a Rapidly Developing Caledon, Ontario, Canada
    (University of Waterloo, 2026-01-21) Zheng, Catherine
    Considerable land in the Town of Caledon, located in Ontario, Canada, is protected by the Greenbelt including sections of the Niagara Escarpment and the Oak Ridges Moraine. Caledon is also subject to an expected rapid population increase, which is at the expense of cultural landscapes and ecosystem functions. As a rural town with agricultural industries and conservation authorities, provincial urban development pressures present Caledon as a case study for engaging with complex and interconnected social, ecological, and planning problems. Through the design of a serious game as a tool for community education and engagement in urban planning, this thesis investigates the relationship between sprawling urban form, ecological illiteracy, and the growing acceptance of environmental degradation. A board game modelled on Caledon’s social-ecological systems, titled Paving Paradise, has been developed to generate dialogue and address the central conflict of urban sprawl, and positions social-ecological urbanism (SEU) frameworks as a solution. SEU is a method of urbanization that applies concepts of systems resilience against urban design, where social-ecological systems are maintained and supported through social institutions and built environments to enhance a city’s resiliency. Paving Paradise functions as a speculative planning model, where urban form is influenced by top-down policy, but transformed by community resilience, adaptation, and ecological stewardship. Designed for community members, the game assigns players distinct roles and asks them to balance individual objectives with collective success to build a socially and ecologically resilient Caledon. Through play, participants engage in dialogue that fosters empathy and encourages new perspectives on the many dimensions of resilient urban growth. Games can serve as a medium to communicate and link complex ideas in accessible ways, giving agency to individuals not specifically trained in various aspects that impact their community. The designed game leverages the educational and engaging properties of game mechanics, acting as a method to communicate social-ecological systems while simultaneously fostering discussion, negotiation, and collaboration. Within this research, mapping is used to synthesize and extract Caledon’s existing social-ecological conditions, and SEU design proposals are illustrated and applied to a neighbourhood in Caledon to show improved human-nature connections, ultimately forming the narrative and logistical foundation of the game. The game’s core mechanics are adapted from an existing tile-laying board game centered on territorial expansion, but they are further informed by game theory and refined through multiple rounds of playtesting and participant interviews. Paving Paradise creates conditions for players to imagine and collaborate on a shared landscape, becoming an effective tool for collective learning and social mobilization. Paving Paradise does not aim to provide solutions or design guidelines. Rather, it simplifies complex and interlinked ideas of policy, urban form, and social-ecological systems to offer a platform for engaging willing participants, in and out of Caledon, on creating and nurturing a resilient urban environment.