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Recent Submissions

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    Tangible World-in-Miniature Interaction in Virtual Reality
    (University of Waterloo, 2026-11-04) Kim, Junhyeok
    Virtual reality (VR) provides a spatial platform for working with miniature representations and tangible proxies across multiple scales and perspectives. However, current world-in-miniature (WiM)-based VR systems face persistent challenges in scale perception, interaction continuity, and the tradeoff between interaction precision and speed. These limitations collectively hinder intuitive multi-scale spatial interaction in VR. This dissertation investigates how tangible user interfaces (TUIs) with WiM-based VR can support interaction across multiple scales and views using tangible proxies. The research examines how users perceive and manipulate miniature representations, how visual–proprioceptive scale discrepancies affect interaction, and how such discrepancies can be managed through interaction design. To investigate this problem, I conducted a progressive, multi-stage research. First, I conducted an exploratory mixed-methods study examining three miniature design tools: online planner, paper-and-pencil sketching, and LEGO assembly. The study used observation, the Desirability Toolkit, the Flow Scale, and semi-structured interviews. Second, I conducted a controlled in-lab VR experiment examining visual–proprioceptive perceptual tolerance using tangible proxies paired with differently scaled virtual objects. Measures included interaction accuracy, task completion time, perceived scale estimation, and subjective discrepancy. Finally, I synthesized these empirical insights and prior literature into a multidimensional design framework, then instantiated one configuration of the framework as Laminar, a prototype interaction technique. This dissertation presents empirical results on how people use and experience three miniature-based interior design tools. It provides quantified evidence of users’ perceptual responses to visual-proprioceptive mismatch when manipulating tangible proxies against differently scaled virtual objects in VR. Finally, I present a design framework and instantiated interaction technique, Laminar, that integrates TUI and WiM within VR to support multi-scalar interaction. Together, this dissertation delivers evidence-informed interaction techniques and design frameworks for tangible WiM in VR, addressing collective challenges in scale perception, multi-scale manipulation, and multi-view workflow fragmentation. This work establishes theoretical and practical foundations for seamless, intuitive, and scalable multi-scalar spatial interaction in VR.
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    Biomechanics of Planar Collagenous Soft Tissues: Heterogeneities and Averaged Material Descriptions
    (University of Waterloo, 2026-11-03) Amiri, Arya
    The overarching goal of this thesis is to advance the understanding of biomechanical heterogeneities and averaged material description of planar collagenous soft biological tissues through experimental, constitutive, and computational approaches, while also refining and adapting existing methods to better suit the specific characteristics and complexities of soft tissues. Despite decades of research documenting the mechanical heterogeneity of soft tissues, existing frameworks have yet to be fully reconciled with the experimental evidence. As the first objective, reindeer back skin and velvet (antler skin) are mechanically tested using a biaxial tensile testing machine, providing a basis for demonstrating the significance of regional mechanical heterogeneity. Motivated to accurately represent each tissue region, the second objective evaluates the concept of averaged material descriptions, specifically ``response averaging" and ``parameter averaging", across various hyperelastic constitutive models, ranges of deformations, and test types, to accurately represent groups of specimens. These findings are further used in the third objective to study whether it is possible to accurately describe local spatial biomechanical heterogeneity with sufficient precision from only a few samples. Specifically, it is done by applying the averaging methods to both experimental stress-strain data and constitutive model outputs to accurately predict mechanically untested intermediate regions between adjacent mechanically characterized tissue regions. Having validated the predictive power of the averaged-material-description approach, the fourth objective of this thesis develops a framework for incorporating local spatial mechanical heterogeneity into finite element (FE) simulations of soft biological tissues. Specifically, motivated by functionally graded materials and using an averaging approach to describe local heterogeneity it proposes to model heterogeneous material constants expressed as continuous Fourier functions of spatial positions. Through case studies of aortic aneurysms and skin tissue, it is demonstrated that a continuous heterogeneous material definition leads to a different stress distribution compared with a homogeneous model and avoids stress concentrations associated with a segmental heterogeneous model. Hence, the integration of regional mechanical characterization and the proposed averaging techniques, combined with the developed method for implementing the mechanical heterogeneity into FEM simulations, explored across all objectives of this thesis, sets a new standard for studying soft tissue biomechanics.
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    Confinement effects on the miscibility of block copolymer blends
    (Springer Nature, 2016) Spencer, R. K. W.; Matsen, and M. W.
    Thin films of long and short symmetric AB diblock copolymers are examined using self-consistent field theory (SCFT). We focus on hard confining walls with a preference for the A component, such that the lamellar domains orient parallel to the film with an even number nu of monolayers. For neat melts, confinement causes the lamellar period, D, to deviate from its bulk value, D_b, in order to be commensurate with the film thickness, i.e., L=nu D/2. For blends, however, the melt also has the option of macrophase separating into nu^(l) large and nu^(s) small monolayers so as to provide a better fit, where L = nu^(l) D^(l)/2 + nu^(s) D^(s)/2. In addition to performing full SCFT calculations of the entire film, we develop a semi-analytical calculation for the coexistence of thick and thin monolayers that helps explain the complicated interplay between miscibility and commensurability.
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    Domain bridging in thermoplastic elastomers of star block copolymer
    (American Chemical Society, 2017) Spencer, Russell K. W.; Matsen, Mark W.
    The performance of thermoplastic elastomers composed of block copolymers is dependent upon the molecular bridges linking together the discrete minority domains. Here we devise a strategy for calculating the bridging statistics for complex block copolymer architectures, using self-consistent field theory. The method is demonstrated on (AB)_M stars with M identical diblock arms. The fraction of molecules forming bridges, nu_b, is found to increase rapidly with M to values well beyond that of conventional ABA triblock copolymers. Once M is of order 10, virtually all molecules form bridges and furthermore their arms tend to be distributed equally among neighboring minority domains. These high bridging fractions combined with the tendency of single molecules to bridge multiple domains makes diblock-arm stars an excellent candidate for improved thermoplastic elastomers.
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    Detection of surface enrichment driven by molecular weight disparity in virtually monodisperse polymers
    (American Chemical Society, 2018) Hill, Jacob A.; Endres, Kevin J.; Mahmoudi, Pendar; Matsen, Mark W.; Wesdemiotis, Chrys; Foster, Mark D.
    The preference for a shorter chain component at a polymer blend surface impacts surface properties key to application specific performance. While such segregation is known for blends containing low molecular weight additives or systems with large polydispersity, it has not been reported for anionically polymerized polymers that are viewed, in practice, as monodisperse. Observations with surface layer matrix-assisted laser desorption ionization time-of-flight mass spectrometry (SL-MALDI-ToF-MS), which distinguishes surface species without labelling, and provides the entire molecular weight distribution, demonstrate that entropically driven surface enrichment of shorter chains occurs even in low polydispersity materials. For 6 kDa polystyrene the number average molecular weight (Mn) at the surface is ca. 300 Da (5%) lower than that in the bulk and for 7 kDa poly(methyl methacryalate) the shift is ca. 500 Da. These observations are in qualitative agreement with results from a mean-field theory that considers a homopolymer melt with a molecular-weight distribution matched to the experiments.