M.S. - Mechanical Engineering

Permanent URI for this collectionhttps://hdl.handle.net/10125/2096

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Design, modification, and evaluation of the jubilee open-source motion platform for automated dip coating
(University of Hawai'i at Manoa, 2025) Vierra, Duke; Brown, Joseph J.; Mechanical Engineering
Laboratory automation increasingly relies on flexible, low-cost systems capable of supporting diverse experimental workflows, yet commercial platforms remain expensive, proprietary, and difficult to adapt. This work evaluates the Jubilee open-source motion platform as a modular foundation for laboratory automation, with a focus on its redesign for thin film fabrication through automated dip coating. Mechanical modifications, including resin printed components, aluminum top and bottom plates, and structural simplifications, were introduced to chemical durability, and overall suitability for laboratory environments, while also reducing the total component count by roughly 20 percent. Vibration testing used to evaluate the effects of the design modifications on the system’s mechanical performance showed that the redesigned frame exhibited substantially larger vibration amplitudes and a broader range of dominant frequencies across all axes, indicating increased structural compliance and changes in mass stiffness distribution. Chemical degradation tests comparing poly-lactic acid (PLA) and Grey Resin V4 showed that PLA experienced substantial loss of mechanical performance when exposed to isopropyl alcohol, while Grey Resin V4 maintained its structural integrity and exhibited only moderate changes in strength and stiffness, confirming its suitability for laboratory environments. To validate tool handling, a color mixing demonstration using an OT-2 pipette and camera tool confirmed that the modified system could execute automated liquid handling, imaging, and data logging. The primary application, automated dip coating, was implemented using a custom vacuum pickup tool and modular deck to process twenty microscope slides at four withdrawal speeds between 2.5 and 10 mm/s. Film thickness measurements obtained through confocal microscopy generally followed the expected Landau-Levich trend, demonstrating that the platform can reproduce the fundamental motion conditions required for dip coated thin film deposition. Variability in coating thickness highlighted limitations related to solution instability, mechanical disturbances, and asynchronous motion control. Overall, the results show that an open-source motion platform can serve as a credible, adaptable, and low-cost basis for laboratory automation and thin film fabrication while identifying engineering refinements necessary for improved reproducibility.
Inverse design of colloidal nanocrystal assemblies with targeted structural and optical features
(University of Hawai'i at Manoa, 2025) Matsunaga, Kaitlyn; Du, Chrisy Xiyu; Mechanical Engineering
The ability to design and control the structure of nanoscale building blocks, such as colloidal nanocrystal assemblies, is central to advancing the next generation of optoelectronic and energy materials with tunable properties. Traditional bottom-up synthesis approaches provide limited control over interparticle interactions, making it difficult to reliably achieve ordered, multilayered structures with targeted geometries. In this work, a computational inverse design framework is presented that combines molecular dynamics (MD) simulations with optimization techniques to direct the assembly of layered colloidal systems. These simulations are performed using JAX-MD, a differentiable MD software framework, where particle interactions are modeled in this thesis using a combination of Morse, screened Coulomb and spring bond potentials. By embedding JAX’s automatic differentiation and gradient-based optimization into the simulation loop, interaction parameters are adaptively tuned until the resulting particle configurations match the predefined design targets. Two demonstrations illustrate the capabilities of the methodology. First, a two layered system that establishes a baseline, composed of identical particles in each layer is optimized by tuning the electrostatic screening parameter (κ) to achieve the target interlayer spacings. The second extends the system to three layers, where particles are uniform within a layer but differ across layers in size and charge. This optimization focuses on tuning κ and the particle charges in the different layers to also achieve target spacings between the various layers. This study establishes a proof of concept for using optimization-driven simulations to engineer ordered, multilayered colloidal structures with controllable geometries, offering a systematic approach to navigating complex nanoscale design problems.
Development of a pouch format thermal dummy cell to aid lithium-ion battery thermal management system development
(University of Hawai'i at Manoa, 2025) Babcock, Christopher John; Dubarry, Matthieu; Mechanical Engineering
Lithium-ion Batteries (LiBs) have become the dominant energy storage technology in the modern world, powering everything from smartphones to electric vehicles (EVs) and large-scale renewable energy systems. Maintaining LiBs within the appropriate temperature range is critical for achieving optimal performance, longevity, and safety. As battery packs continue to push higher currents, faster charging, and tighter packaging, battery thermal management systems (BTMSs) are required to have higher efficiency, better uniformity, lighter weight, and lower volume penalty. LiB cell testing poses safety concerns associated with chemical reactions, high voltage exposure, and thermal runaway. LiB thermal testing can also require high-cost equipment such as battery cyclers, glove boxes, and the large battery modules themselves. Therefore, an opportunity to expand access to LiB thermal testing and BTMS research is through improved safety and reduced test equipment burden. This can be achieved with development of a Thermal Dummy Cell (TDC) which is a device that matches the form and thermal behavior of a real battery cell but has no active material. TDCs in the current literature have aimed to match temperatures instead of heat generation rates (HGRs) of real cells and have employed spatially uniform HGRs [27, 28]. Real cells demonstrate non-uniform heat generation which can lead to unique BTMS requirements [20]. There has also been insufficient focus on analyzing, designing, and verifying TDC thermophysical properties alignment. Therefore, development of a TDC with spatially controlled heat generation and emphasis on thermophysical properties is identified as a research opportunity. The first generation TDC developed in this work employed a segmented heat generation system capable of dynamic spatial control and feedback regulation. It employed a layered structure utilizing materials representative of a real cell, though less emphasis was placed on its thermophysical properties. Successful testing included uniform heating of the entire device to reach a target temperature, simulating thermal gradients observed in real cells, and meeting temperature ramp rates and hold temperatures according to a pre-defined dynamic profile. First-pass thermophysical property testing of the first generation TDC demonstrated promising alignment in comparison testing with a real cell. The second generation TDC developed in this work maintained the heat generation system from the previous design but emphasized integration of that system into the structure and matching of real cell thermophysical properties. A greater level of analysis went into the structural design to predict effective thermophysical properties of the device and to enable uniform heating power density across each heated segment. A proof-of-concept prototype was built and tested which demonstrated viability and confirmed numerical model predictions. This work provides a strong foundation for continued development of TDC designs that match the detailed heat generation characteristics and key thermophysical properties of LiBs. Future work will include finalization of the second generation design, comparison testing with real cells, and TDC pack/module development. TDCs of this sophistication can play a critical role in the safe and effective research and development of BTMSs which are seeing ever increasing requirements.
Developing a model-based system engineering methodology for cubesat missions
(University of Hawai'i at Manoa, 2025) Kline, Piper Leigh; Nunes, Miguel A.; Mechanical Engineering
Cube Satellites (CubeSats) have become increasingly popular, particularly in academicsettings, due to their affordability, rapid development timelines, and usefulness as platforms for student training and experimental payloads. Despite these advantages, CubeSat development presents several challenges, including limited resources such as personnel, funding, and time, as well as difficulties in maintaining comprehensive documentation and managing requirement changes. Student-led projects face additional obstacles, including inexperienced team members and high turnover rates, which can hinder effective knowledge transfer. Model-Based Systems Engineering (MBSE) has emerged as a promising approach to address these challenges and improve the efficiency of CubeSat design and development. Rather than relying on documents to capture system designs, MBSE uses models to represent, analyze, and validate the design. It also emphasizes a strong systems engineering mindset, ensuring a holistic approach and that the optimal system of interest is being developed to meet the project needs. Although MBSE has been applied to satellite missions and domain-agnostic methodologies exist, significant challenges still remain in adapting it, particularly in small groups, due to the steep learning curve and resource requirements for training personnel and model development. Additionally, there is a lack of satellite-specific MBSE methodologies that define thorough steps and methods to design a satellite using MBSE. This research develops an approach that integrates the Arcadia MBSE methodology with NASA’s Life-Cycle and Space Mission Architecture Framework (SMAF) to create a satellite-specific methodology. The objective is to provide a structure for implementing MBSE while making the design process more effective for small, academic satellite projects. After developing an initial methodology, it was applied to the Neutron-2 (N2) CubeSat Mission to gain a better understanding and refine the approach. While the MBSE methodology offers significant advantages over document-centric engineering, challenges such as steep learning curves and complex tools must be addressed through additional tutorials and a robust library of reusable models. Additionally, dynamic simulations should be derived from the MBSE models to fully leverage digital engineering and validate the design. Future work will involve producing these comprehensive tutorials and developing the supporting simulations to validate the design, as well as implementing the methodology in a classroom setting to refine it.
Experimental study on the Oscillating Water Column integrated with slotted barrier for shore protection and wave energy conversion
(University of Hawai'i at Manoa, 2025) Walker, Mayah; Huang, Zhenhua; Mechanical Engineering
This research explores a wave energy conversion (WEC) system combining an Oscillating Water Column (OWC) with a slotted barrier breakwater. The OWC consists of a hollow chamber where incoming waves cause air trapped inside to oscillate, driving a pneumatic power take-off (PTO) device. The slotted barrier serves multiple functions: it protects the shoreline, maintains local water quality, and directs wave energy into the OWC chamber to be converted into electricity. Integrating the OWC with the slotted barrier reduces initial investment costs by combining wave energy extraction with essential coastal protection infrastructure. Unlike traditional WEC devices, which often have moving parts exposed to harsh marine environments and require specialized vessels for installation and maintenance, this design features modular, precast elements with all electronic components housed above water, improving durability and ease of deployment. Experimental testing was conducted in a small-scale wave flume using various slotted barrier porosities, wave heights, periods, and water depths. The tests evaluated the device’s performance by measuring the wave energy extracted by the OWC, the energy transmitted past the structure, the energy reflected back toward the wave generator, and the forces acting on the breakwater. Results demonstrate that adding the OWC chamber reduces wave energy transmission beyond the barrier and that lower porosity barriers increase pneumatic energy extraction. For larger waves, the system maintains a consistent level of reflected wave energy, increases pneumatic energy capture, and decreases energy transmission, thereby offering enhanced shoreline protection. Across different wave periods and depths, the transmission coefficient remained between 0.5 and 0.75. Optimization tests showed that smaller porosity barriers increase drag forces, viscous dissipation, and wave reflection, highlighting a trade-off between maximizing energy extraction and managing structural loading. These insights provide a foundation for optimizing the slotted barrier and OWC design to balance energy conversion efficiency, shoreline protection, and structural integrity.
Microscale impacts of lubricant-derived ash on the functionality and design of a zone-coated combined diesel oxidation catalyst and particulate filter system for heavy duty applications
(University of Hawai'i at Manoa, 2025) Fujimoto, Ryan; Brown, Joseph J.; Mechanical Engineering
Diesel aftertreatment systems have evolved into complex, multifunctional devices that consolidate functions while reducing cost, package size, and precious metal usage. This has driven the combination of the diesel oxidation catalyst and diesel particulate filter into a single zone coated diesel oxidation catalyst filter (DOCF) that must manage oxidation of soot, CO, and NO, wall-flow filtration, and ash accumulation within a single porous ceramic substrate. This work presents a novel multiscale, multi-instrument approach combining scanning electron microscopy (SEM), confocal laser profilometry, micro X-ray computed tomography (µCT), and X-ray diffraction (XRD) to characterize the impacts of zone coating and ash deposits on pore structure, surface morphology, and flow interactions through multiple length scales from nano to millimeters. SEM and profilometry show the thicker Zone 1 inlet washcoat preferentially closes mesopores, shifting pore diameter and area distributions toward larger values, increasing nearest-neighbor spacing, and changing circularity relative to the thinner Zone 2 coating. In ash-loaded samples, SEM, profilometry, and µCT together reveal ash accumulation as wall layers, end plugs, and mid-channel plugs with variable packing densities, along with hydrated ash species and high-temperature sintered deposits that penetrate the wall. This research establishes a novel multi-instrument approach that links washcoat thickness, pore size distributions, surface roughness, and ash morphology to the resulting changes in flow restriction, soot filtration mode, and catalytic performance, providing guidance for future characterization, design, and optimization of zone-coated DOCF and more broadly microporous substrates.
Encapsulating transparent catalytic electrode for solar fuel devices
(University of Hawai'i at Manoa, 2025) Paranhos Lopes, Jade; Gaillard, Nicolas; Mechanical Engineering
Buried-junction photoelectrochemical (BJ-PEC) systems offer a promising route for efficient and low-cost solar-to-hydrogen conversion. These systems use fully integrated photovoltaic (PV) devices with highly efficient photoabsorbers and allow for multijunction (MJ) architectures which absorb photons and can generate sufficient photovoltage and photocurrent to split water. Thin film technologies like perovskite solar cells (PSC), and Cu(In,Ga)Se2 (CIGSe) are particularly attractive for MJ devices, due to their high, National Renewable Energy Lab (NREL) certified, single-junction (SJ) efficiencies (27% and 23.6%, respectively), tunable bandgap, high absorption coefficient, and compatibility with low-cost solution processing. A major challenge for BJ-PEC implementation is the instability of the PV absorbers (PSC/CIGSe) in aqueous electrolytes, as well as the need for monolithic catalyst integration strategies that minimizes optical and electrical losses to the device. To address these limitations, this thesis introduces the transparent conductive composite (TCC) as a multifunctional encapsulating transparent catalytic electrode for BJ-PEC devices. The TCC is a thin film consisting of 50 μm Ag-PMMA conductive microspheres embedded in an epoxy resin polymer matrix. This work builds upon previous studies done at the Hawaii Natural Energy Institute (HNEI), where the TCC was used as a bonding transparent electrode layer for MJ devices, and encapsulant for PSCs operation in air (traditional PV configuration) and expands its functionality to aqueous operation as BJ-PEC device for hydrogen production. To standardize and optimize TCC fabrication, a mechanical model based on analytical hertzian contact mechanics was developed to describe the Ag-PMMA microsphere deformation under an applied load (which is required during TCC assembly). Single sphere load-displacement measurements were performed across temperatures to extract the Ag-PMMA material properties. These values informed the analytical model which was first used to predict elastic deformation for single spheres and subsequently extended to model multisphere behavior. This enabled the prediction of the TCC bond-line thickness (i.e., the thickness of the cured epoxy layer), and percent exposure as a function of applied pressure, microsphere concentration, and temperature. Model predictions deviated by less than 5% from the experimentally defined thickness-pressure and microsphere exposure-pressure relationships, validating the model as a predictive framework for TCC fabrication. The optimized TCC was then integrated into a mechanically stacked CIGSe/PSC MJ PV device and subsequently into a BJ-PEC device. As a bonding interlayer between the two CIGSe and PSC sub-cells, the TCC provided mechanical adhesion, high optical transmission (≥ 85% across visible spectrum), and electrical connectivity. The resultant PV device demonstrated an efficiency of 14.62%, a short circuit current density of 9.3 mA/cm2 an open circuit voltage of 1.85 V, sufficient to drive water splitting. As a transparent catalytic electrode placed on top of the tandem PV, selective electrodeposition was achieved on the TCC microsphere surface, confirmed through electron dispersive spectroscopy. The resulting BJ-PEC device with a catalyst coated TCC achieved a solar to hydrogen efficiency of 4.8% and demonstrated stable photocurrent for a test done over 40 minutes. These results validated the TCCs capability as an encapsulating transparent conductive catalytic encapsulant, and its potential to serve in PEC based systems for renewable hydrogen production.
On the geometry of load paths
(University of Hawai'i at Manoa, 2025) Freitas, Christopher John; Kobayashi, Marcelo H.; Mechanical Engineering
This thesis develops a novel framework for defining and analyzing structural load paths using variational principles. Load paths describe the internal transmission of forces within a structure and are fundamental to understanding structural behavior, optimization, and design. Traditional optimization methods like SIMP and level set techniques typically rely on stress approximations, often yielding impractical or non-intuitive results. However, approximations based on internal loads have proven to be more accurate and may illustrate more meaningful approaches. This work formulates load paths as geodesics governed by the stress field, drawing analogies from differential geometry. Two types of formulation are discussed, the Lagrangian and the Hamiltonian. The Lagrangian formulation interprets load paths as curves that minimize a Lagrangian functional, analogous to minimizing the action in mechanics, while the Hamiltonian formulation introduces complementary insights via energy conservation and contravariant stress tensors. First, examples are given for each system separately, while application to an ESAVE wing structure is used to demonstrate how these load path formulations can guide structural design. Numerical solutions are obtained using finite element analysis and differential equation solvers, followed by design optimization using MSC.Nastran. The study also draws analogies with the Schwarzschild metric to further interpret geodesic behavior in structural systems. Ultimately, this approach offers a physically intuitive and computationally tractable means to identify meaningful load paths, potentially enhancing structural optimization methods and practical design workflows.
A semi-automated handheld active needle device for percutaneous image-guided interventions
(University of Hawai'i at Manoa, 2025) Kinder, Josh; Konh, Bardia; Mechanical Engineering
This thesis presents the design and preliminary evaluation of novel brachytherapy (BT)systems intended to improve anatomical conformity, placement precision, and procedural safety in high-dose-rate (HDR) treatments for prostate and cervical cancer. Traditional applicators often rely on rigid, manually inserted components, which limit adaptability and reduce dose accuracy in patients with complex anatomical and disease variations. To address these limitations, a semi- automated active needle system was developed for prostate HDR BT, integrating a custom 3D- printed template and preplanned curvilinear trajectories based on patient-specific magnetic resonance imaging (MRI) data. Phantom and air testing demonstrated sub-millimeter tip displacement accuracy, validating the system’s precision. Building on this foundation, a handheld tendon-driven steerable needle device was created for real-time use under transrectal ultrasound (TRUS) guidance. This system features a joystick-controlled actuation mechanism and a modular TRUS attachment to support intraoperative visualization and navigation. For cervical cancer treatment, a modular applicator was designed incorporating adjustable vaginal spreaders, a controllable tandem channel, and support for 2 mm steerable needles. The design accommodates ovoid separation from 25 mm to 45 mm. The performance and range of motion were validated for TRUS imaging compatibility. Future development will focus on interfacing the cervical applicator with externally controlled telescopic pre-curved tandems and incorporating mechanisms for active adjustment of ovoid geometry. Collectively, these systems demonstrate the feasibility of integrating flexible, image-guided instrumentation into HDR BT workflows, offering a pathway toward more personalized, precise, and patient-specific cancer treatment solutions.
Development and validation of a digital twin system model for a piezoelectric sensor
(University of Hawai'i at Manoa, 2025) Okura, Kailer; Brown, Joseph J.; Mechanical Engineering
This study presents a multiphysics modeling framework for a piezoelectric force sensor embedded within an automotive tire system, combining finite element and circuit simulation with empirical validation. The project had three primary objectives: (1) to modify an exist- ing two-dimensional axisymmetric tire model in COMSOL® to accommodate localized point loading, (2) to develop a virtual representation of a multilayer piezoelectric sensor capable of predicting voltage output under mechanical stress, and (3) to validate this model utilizing experimental techniques. To address the tire modeling challenge, the axisymmetric geometry was extruded into a complete three-dimensional model to enable the simulation of discrete contact forces. A simplified pseudo-tire model, constructed with linear elastic materials, was able to converge under internal pressure and contact loading, producing a peak von Mises stress of 2 × 10^{2} N/m^{2} and a maximum displacement of 3 × 10^{-2} m at 5 kPa of interior air pressure. For the sensor, a two-dimensional COMSOL model was coupled with an LTspice® circuit to capture electromechanical coupling and time-dependent electrical behavior. The COMSOL simulation produced a peak voltage of 33.55 V and an integrated charge of 1.25 × 10^{−8} C under a ±500 N force sweep. Experimental validation using three- point bending and a voltage follower circuit yielded a capped sensor output of approximately 5 V at 250 N. Comparison between the COMSOL and experimental force–displacement data showed partial agreement, with a standard deviation of 2.71 N and a 24.23 % error. While the simulation accurately captured the sensor’s early behavior, it lacked the nonlinear plateau observed in the experimental results. This discrepancy suggests that future work should in- corporate parasitic loss mechanisms. This integrated modeling approach lays the foundation for digital twin frameworks in next-generation intelligent tire systems.
Efficacy of curvilinear catheter implantation for prostate cancer interventions
(University of Hawai'i at Manoa, 2025) Imanaka, Rex R.; Konh, Bardia; Mechanical Engineering
High-dose-rate (HDR) brachytherapy (BT) is a widely utilized treatment for patients with intermediate- and high-risk prostate cancer. Despite its proven efficacy, it is often associated with side effects such as edema, urinary incontinence, and sexual dysfunction. A key limitation of HDR BT, however, lies in the risk of delivering excessive radiation to nearby organs-at-risk (OARs), including the urethra, bladder, and rectum. To minimize radiation exposure to OARs and improve patient outcomes, curvilinear catheter implantation has been investigated as an alternative to conventional rectilinear techniques. Unlike rectilinear catheter placement, curvilinear implantation enables the catheters to better conform to the natural contours of the prostate. This enhanced conformity allows for more precise dose delivery, reducing radiation exposure to surrounding OARs, while also potentially decreasing the number of needles required for the procedure. Despite its clear advantages, curvilinear catheter implantation has not been widely adopted in clinical practice due to challenges related to needle control, precise placement, and insertion accuracy. This work represents the culmination of a series of studies that: (i) evaluate the effectiveness of curvilinear catheter application, (ii) explore methods to control the initial needle insertion angle, (iii) develop robotic systems for precise needle insertion, and (iv) support the training of new physicians in curvilinear catheter implantation techniques.
Experimental evaluation of process-property relationships in bound powder extrusion based metal additive manufacturing
(University of Hawai'i at Manoa, 2025) Lorenzo, Kendall; Ray, Tyler; Mechanical Engineering
Additive manufacturing (AM) techniques permit the fabrication of intricate geometries that are challenging or impossible to produce using traditional subtractive methods (e.g., machining). Bound powder extrusion (BPE), an AM variant, extends this capability to functional metal components in a process akin to the production of polymer parts via consumer-grade printers. AM-fabricated parts differ fundamentally from wrought materials: each exhibits unique characteristics due to inherent defects like porosity, residual stresses, and orientation-dependent mechanical properties stemming from the layer-by layer build process. In BPE, this anisotropy manifests as significant variations in strength and ductility with printing direction, introducing variability and uncertainty that demand thorough characterization for reliable part qualification and engineering deployment. Despite BPE's potential, detailed studies on the mechanical properties of its metal outputs are sparse, with existing data showing inconsistencies from differing processing and testing conditions; even scarcer are systematic explorations of orientation effects essential for design optimization. To address these deficiencies, I undertook a comprehensive evaluation of 17-4PH stainless steel components produced via the Markforged MetalX system, printing specimens in 0°, 45°, and 90° orientations relative to the build direction. These were subjected to tensile testing, hardness measurements, surface roughness profiling, and corrosion assessments, with all metrics benchmarked against wrought 17-4PH. Through these efforts, it was observed that essential, orientation-resolved property insights absent in the literature that will aid in enabling evidence-based design of BPE components, expanded characterizations across Markforged alloys to foster comprehensive material databases, and enable broader utilization in industrial applications.
Exploring planetary surfaces: Active learning for resource mapping with autonomous rovers
(University of Hawai'i at Manoa, 2025) Akins, Sapphira; Zhu, Frances; Mechanical Engineering
The exploration of planetary surfaces presents unique challenges that necessitate autonomous decision-making to optimize scientific data collection. Such data collection is necessary to facilitate technological advancements and increase our knowledge of planetary bodies. This thesis investigates the use of active learning algorithms to enhance the efficiency of planetary surface exploration, with a particular focus on Gaussian Processes (GPs) and cost-aware query policies that ensure efficiency and minimization of annotation costs. By employing active learning techniques, autonomous robotic agents can select informative sampling locations, reducing the number of samples and distance required while maximizing scientific findings. Through a combination of simulation studies and real-world experiments, this research evaluates the performance differences of GPs and Bayesian Neural Networks (BNNs) in constrained trajectory exploration. The findings indicate that GPs consistently achieve faster convergence, require fewer samples, and result in shorter travel distances compared to BNNs. Despite the flexibility of BNNs in modeling complex spatial distributions, they exhibit higher computational demands and reduced reliability in sparse-data environments. A field demonstration conducted on Mauna Kea, a recognized lunar analog site on the island of Hawai'i, further validates the applicability of active learning algorithms in real-world planetary exploration settings. The results highlight the potential of GP-based active learning in reducing mission duration and optimizing energy efficiency for autonomous robotic explorers. Along with this, in-situ testing was completed in a sand court at the University of Hawai'i at Manoa where various query policies were tested on their efficiency at minimizing costs associated with data collection. This work contributes to the development of intelligent exploration strategies for planetary surface missions. A future research direction includes additional real-time deployment of active learning algorithms, particularly with fully autonomous rovers in lunar regolith testbeds with scientific instrumentation planned for use on a space mission.
Design and optimization of compliant mechanisms for mechanical attachment systems
(University of Hawai'i at Manoa, 2025) Laudone, Russell; Brown, Joseph; Mechanical Engineering
Bistable compliant mechanisms offer a promising alternative to traditional fasteners and adhesives for mechanical attachment, enabling lightweight, reusable locking systems across diverse applications. This work presents two compliant locking mechanisms: one tool-less and in-plane for aerospace thermal protection systems, and another tool-actuated and out-of- plane for modular panel assemblies. The aerospace mechanism was prototyped in polylactic acid (PLA) and optimized using a hyperelastic solid model with a yield constraint, applying sequential sweeps of geometric parameters. The resulting design achieved a retention force of 53.41 N with a mass of 47.3 g and a 789 mm2 footprint, offering rapid tile exchange without adhesives. The modular panel system created a physical model inspired by industry needs and, separately, introduced an updated computational framework using particle swarm op- timization (PSO) coupled with FEniCSx simulations to enable multi-dimensional geometry tuning for material-dependent design. PSO-FEniCSx algorithm explored a three-parameter solution space, including band thickness, band angle, and side shuttle length, using a swarm of 16-particle’s evolving over 12 iterations. The best configuration, with band thickness “t” = 1.3 mm, band angle ”θ” = 78.85◦, and side shuttle length “ssl” = 29.66 mm, achieved a peak retention force of 66.33 N while remaining below the 95% yield stress threshold. Experimental validation confirmed that PSO accurately characterizes structures based on maximum force. However, it was found that the FEniCSx boundary conditions did not cor- rectly accurately represent deformation at the side walls during geometry transformation. To resolve this discrepancy, replacement of fixed conditions with a pin support is recommended. These results demonstrate that bistable compliant structures can be computationally opti- mized and physically tuned to meet application-specific requirements in both aerospace and architectural contexts.
Design and fabrication of a modular, low-cost aerosol jet printer
(University of Hawai'i at Manoa, 2025) Viernes, Kian; Ray, Tyler; Mechanical Engineering
Flexible electronics that conform to non-planar surfaces represent an important frontier in device engineering, with applications spanning wearable systems, biomedical interfaces, and structural monitoring. Fabrication of these systems requires manufacturing approaches that can precisely pattern functional materials onto diverse substrates. Aerosol jet printing (AJP) offers distinctive capabilities in this domain, using aerodynamic focusing to direct aerosolized functional inks with high spatial precision onto both planar and non-planar surfaces. We report the development of a modular, low-cost aerosol jet printer (LC-AJP) constructed from commercial off-the-shelf components, open-source software, and custom 3D-printed elements. Despite its modest cost (<$1,200), the system achieves sub-50 µm resolution in printed features. We demonstrate material versatility by successfully printing with silver nanoparticle inks, PEDOT conducting polymer, and carbon black composites, enabling fabrication of functional temperature sensors. The modular architecture facilitates rapid innovation, exemplified by our implementation of a 4-in-1 multi-nozzle configuration that quadruples production throughput by simultaneously printing four identical structures. This accessible platform establishes a foundation for broader adoption of advanced manufacturing techniques for flexible electronics, with opportunities for further refinement in resolution, materials compatibility, and integration with complementary fabrication methods.
Development and Design of a Compact Laparoendoscopic Single-Site Robotic Surgical System Integrating ROS2 Middleware
(University of Hawai'i at Manoa, 2024) Trafford, Sean; Berkelman, Peter J.; Mechanical Engineering
Minimally invasive surgery aims to further this by performing procedures with the least number of incisions necessary. Single-port laparoscopy takes this a step further by having every instrument used in the procedure operate from inside just a single small incision. While minimally invasive surgery has been shown to have beneficial outcomes in regards to the speed, quality, and cosmetics of the healing process, it is heavily restricted by the prerequisite skill required by the surgeon. To this end, Robotic surgical systems can be used to lower the skill floor. The surgical system presented in this thesis was built upon a previous University of Hawai‘i at Manoa system [1], designed to have a similar level of performance to other systems on the market, such as the Intuitive Surgical Inc. da Vinci RAS, while reducing the cost and total volume taken up by the system. While the goals of cost and volume were solved by the previous iteration of the surgical system, it introduced a brand new problem of longevity. To remedy this, new components possessing similar dimensions to the components of the original system were used, but with 6061 aluminum as the primary material used, rather than ABS P-430 plastic. A new control system was also created which utilizes a damped-least squares algorithm to calculate the inverse kinematics based on the motions of a Geomagic/Sensable Phantom Omni controller, and using velocity control to further adjust the positioning. Finally, rather than operating from multiple computers simultaneously, Robotic Operating System 2 (ROS2) middleware was implemented to allow for the simultaneous operation of two arms through multi-core processing, the transference of positional data between the two control algorithms, and any additional programs. Through the use of a Northern Digital Polaris Vicra optical tracker, spatial data for the system was taken for movement along a preset path, and free hand taken from the controller, both over a time of 70 seconds. The results in both cases displayed a visual reduction in positional drifting when compared to the results of previous systems, with the preset path never visually achieving more than a drift of 0.5 mm off the path before self-correcting, with an average deviation from the path of 0.434 mm. The free hand data, also displayed a visual improvement by maintaining the same path for the duration of the experiment, rather than permanently drifting in a single direction, with an average deviation from the path of 1.953 mm. While the motion tracking data does show a promising improvement compared to the previous UH Mānoa system, additional practical testing and structural refinements will be required to determine if the surgical system is ready to enter pre-clinical development.
MARINE VEHICLE CHARACTERIZATION AND IMPLEMENTING VARIOUS LEVELS OF AUTONOMY
(University of Hawai'i at Manoa, 2024) Ng, Patrick Julian; Krieg, Michael; Mechanical Engineering
Remotely operated vehicles (ROVs) are marine submersible robots that serve a variety of purposes in industry and research. These unmanned vessels harness human judgment and precision to perform tasks within extreme environments like the deep sea, polar, and volcanic regions of the ocean. Some examples of their usages are to survey the ocean floor, maintain pipelines and collect scientific data in the form of sediment and hydrothermal vent plume samples and optical observations of marine wildlife. Training of ROV pilots is typically very expensive and time-consuming because of the highly specialized skill requirements. A novel system was proposed by collaborators from the University of Florida (UF) and the University of Hawai‘i at M ̄anoa (UHM) for piloting ROVs with an intuitive augmented/virtual reality (AR/VR) interface that uses a hybrid autopilot. To demonstrate the feasibility of this system the group at UHM altered the ArduSub firmware of the commercially available BlueROV2 (BROV2) Heavy to enable model-based quantitative control. Error feedback control for the hybrid autopilot was implemented using Robot Operating System (ROS) in a modular manner that enabled various levels of autonomy to assist ROV pilots. Alongside the development of the custom firmware and hybrid autopilot, the software-in-the-loop (SITL) simulation environment was also updated with an experimentally determined hydrodynamic model using onboard sensor- based system identification techniques As much as sixty percent improvement of relative error when predicting vehicle behavior compared to the original SITL model. The calibration process of the hybrid autopilot involved iteratively cycling between SITL and water tank testing. It was demonstrated that this procedure was an effective method for achieving precision control of the BROV2.
Development of a Thermal Dummy Cell (TDC) for Pouch Cells in Lithium-Ion Battery Thermal Management Systems
(University of Hawai'i at Manoa, 2024) Bahrami, Armida; Dubarry, Matthieu; Mechanical Engineering
Lithium-ion (Li-ion) batteries have become indispensable in various sectors, including consumer electronics, automotive, and renewable energy storage, due to their high energy density, long service life, and efficiency. Effective thermal management is crucial to ensure the safety, performance, and longevity of these batteries. This thesis focuses on developing a segmented Thermal Dummy Cell (TDC) specifically for pouch cells—a novel and pioneering design that has never been constructed before. Unlike cylindrical and prismatic cells, which have been extensively studied, pouch cells have lacked sufficient research in thermal management, leaving a critical gap in the literature. Previous studies have developed TDCs for cylindrical and prismatic cells, providing valuable insights into the thermal behavior of these battery types. However, this research introduces the first-ever segmented TDC tailored for pouch cells, featuring independent control over each heating segment. This allows for precise temperature management that closely simulates real-world battery conditions. The system incorporates Pulse Width Modulation (PWM) control and advanced data monitoring, capturing essential parameters such as temperature, current, voltage, and power in real time. The thesis begins with a comprehensive review of existing literature on TDCs for cylindrical and prismatic cells, identifying the methodologies and findings that can be applied to pouch cells. It then details the iterative design process of the pouch cell TDC, including the challenges encountered and the solutions implemented. The final prototype consists of 11 heating pads arranged in a 3x3 grid for the body and 2 additional pads for the tabs, controlled via Arduino and PWM to achieve precise temperature control. Extensive calibration and testing were conducted to ensure the TDC accurately mimics the thermal behavior of real pouch cells. The results demonstrate that the TDC provides a reliable and safe means of studying thermal management strategies for pouch cells. By enabling individual control of heating segments, the system offers in-depth insights into localized thermal effects, making it ideal for research aimed at improving battery safety and efficiency. This development enables safer and more accurate studies of thermal behavior without the risks associated with live cells. This research represents a significant advancement in the field of battery thermal management by offering a novel tool for researchers and engineers. It serves as a key step forward in understanding and controlling the complex thermal dynamics of lithium-ion batteries, ultimately contributing to the evolution of energy storage technologies.
Stress Corrosion Cracking and Hydrogen Embrittlement Atmospheric Corrosion Testing of Control and Prototype Steels
(University of Hawai'i at Manoa, 2024) Maruno, Tyler; Hihara, Lloyd; Mechanical Engineering
The United States Department of Defense has begun the formulation of a new generation of high strength steels for naval applications, emphasizing superior hardness, toughness, and ballistic resistance. Whilst these metals have been designed with a focus on strength, their corrosion behavior is largely unknown and must be characterized prior to widespread application. This research involved the design of an experiment to test the stress corrosion cracking and hydrogen embrittlement susceptibility of HY-100, HSLA-150, 10Ni QQT, and 10 Ni QQLT steels. A modified version of the standardized four-point bend test in which samples are stressed to 90% of their yield strength was designed to be implemented in numerous microclimates across the State of Hawai’i. In addition, microstructural analysis was performed via metallurgical techniques, while the corrosion behavior was quantified via electrochemical polarization. Inclusions were characterized in each steel, with directional, structural, and elemental analyses performed. Aluminum and iron containing oxides were identified in each metal, with 10Ni steels showing the highest frequency of inclusion clusters. Potentiodynamic polarization testing provided information pertaining to the corrosion rates of each steel along with zinc and magnesium in three solutions simulating freshwater, acidic, and saline environments. While all four steels produced similar galvanic potential and current density results, magnesium was shown to induce the highest levels of hydrogen liberation on the steels with rates consistently two orders of magnitude greater than that due to zinc. Combined, the information obtained as related to stress corrosion cracking, hydrogen embrittlement, and material characterization serve as integral pieces necessary to validate and further refine the next generation of high strength steels for defense applications.
Solar-Thermal Desalination with Reduced Graphene Nanocomposites and Hydrophobic Polymers for Enhanced Evaporation and Dropwise Condensation
(University of Hawai'i at Manoa, 2024) Blanks, Sean Allen; Lee, Woochul; Mechanical Engineering
Interfacial solar-thermal desalination is an off-grid passively operated method of producing pure drinking water. It shows especially high promise in providing an inexpensive sustainable desalination solution for currently underserved dispersed communities who are unable to adequately secure drinking water and lack the infrastructure to justify traditional large scale energy intensive desalination plants. The aim of this thesis is the fabrication of an inexpensive high efficiency interfacial solar-thermal desalination prototype capable of producing pure drinking water. To meet this aim, the independent development of both a high efficiency evaporator and condensing surface were approached utilizing benign fabrication methods. Improving upon previous solar-to-vapor efficiencies through improved substrate wettability and coating photothermal absorption efficiency, a carbon based solar-thermal evaporator derived from an Aquazone dip coat of reduced graphene oxide (rGO) and polydimethylsiloxane (PDMS) nanocomposite achieved an average solar-to-vapor conversion efficiency of 69.7%. To capitalize on the high vaporization efficiency, a polyvinyl chloride cover treated with a hydrophobic polymer coating for enhanced drop wise condensation was employed for water collection with a measured condensation efficiency of 86.0%. The resulting prototype demonstrated high efficiency through improvement of both condensation and evaporation. Further, the prototype successfully produced pure water from local seawater, meeting water quality standards provided by both the Environmental Protection Agency National Primary Drinking Water Regulations and the Standards and Guidelines for Contaminants in Massachusetts Drinking Waters. Based off this investigation it was also found there exists great potential with bridging the gap from in-situ prototypes productivity to the potential efficiencies of promised from lab values.

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