Materials Science and Engineering Commons^™

Rapid-Prototyping Nanofabrication: Lcd-Based Projection Lithography And Physical Vapor Deposition, Sabeel Saleem Mohammmed

University Honors Theses

The semiconductor industry's continued growth, driven in large part by demand for artificial intelligence hardware, has highlighted the need for greater workforce development in regions adjacent to major fabrication centers like Oregon's Silicon Forest. This capstone project lays the groundwork for a small scale and student led semiconductor fabrication lab at Portland State University by demonstrating two of the core steps in chip manufacturing: photolithography and thin film deposition. Rather than relying on conventional fixed reticles, this work explores a unique, low cost approach to patterning that uses an ultraviolet-compatible liquid crystal display (LCD) as a programmable reticle, allowing arbitrary …

Characterizing Indoor Surface Voc Contamination After The 2025 Los Angeles Fires, Brett W. Stinson, Emily Lei, Elliott T. Gall

Mechanical and Materials Engineering Faculty Publications and Presentations

We quantify volatile organic compound (VOC) emissions from indoor surface swabs and portable air cleaner (PAC) filters collected in a home 30 days after the 2025 Los Angeles wildland-urban interface (WUI) fires. We calculate emissions for 17 fire-relevant compounds. Surface emissions exceeded those of clean controls, and emissions from a windowsill in a room without a PAC were ∼15× and ∼2× higher for benzene and toluene, respectively, than rates reported in the literature for comparable materials unaffected by smoke/soot. Particle filters installed in PACs at the start of the fire emitted aromatics at rates comparable to those reported in a …

Concerted Rattling-Induced Strong Anharmonicity And Phonon Coherence Lead To Ultralow Glasslike Thermal Conductivity In Tlagte, Shantanu Semwal, Yi Xia, Chris Wolverton, Koushik Pal

Mechanical and Materials Engineering Faculty Publications and Presentations

Ordered crystalline compounds exhibiting ultralow and glass-like thermal conductivity are both fundamentally and technologically important, where phonon quasi-particles dominate their heat transport. Understanding the microscopic mechanisms that govern such unusual transport behavior is necessary to unravel the complex interplay of crystal structure, phonons, and collective excitations of these quasi-particles. Here, we use state-of-the-art first-principles calculations based on quantum density functional theory to investigate the origin of experimentally measured unusually low and glassy thermal conductivity in semiconducting TlAgTe that possesses disconnected chains of Tl atoms within its three-dimensional crystalline framework made up of distorted AgTe4 tetrahedra. Utilizing a unifying framework of …

Effects Of Wetting Events On Mass Timber Surface Microbial Communities And Voc Emissions: Implications For Building Operation And Occupant Well-Being, Gwynne Á. Mhuireach, Susan Collins, Leslie Dietz, Patrick Finn Horve, Aurélie Laguerre, Dale Northcutt, Jason Stenson, Kevin Van Den Wymelenberg, Elliott Gall, Mark Fretz

Mechanical and Materials Engineering Faculty Publications and Presentations

IntroductionHumans have used wood as a construction material throughout history. Currently, mass timber products, such as cross-laminated timber (CLT), are becoming more popular as a structural material, since they are renewable and have a lower carbon footprint than concrete or steel. Nonetheless, some building types, such as healthcare, veterinary, and food manufacturing, avoid using structural mass timber due to concerns about microbial growth in the event of wetting. One solution is to use protective coatings on mass timber products to increase moisture resistance, although the coatings themselves may generate concerns about volatile organic compound (VOC) emissions. Natural uncoated wood also …

Exploring The Effect Of The Architecture Morphology On Urban Ventilation At Block Scale Using Cfd-Gis And Random Forest Combined Method, Bin Guo, Miaoyi Chen, Xiaowei Zhu, Zheng Wang, Lu Li, Lin Pei, Hailong Chen, Puhao Chen, Tengyue Guo

Mechanical and Materials Engineering Faculty Publications and Presentations

Urban ventilation plays a crucial role in dispersing air pollutants and mitigating the urban heat island effect. As a key factor, urban architectural morphology can significantly impact the wind field and ventilation efficiency. This study combines Computational Fluid Dynamics (CFD), Geographic Information System (GIS), and Random Forest (RF) methods to investigate the influence of architectural morphology on urban ventilation at the block scale. First, Remote Sensing (RS) and GIS were used to extract architectural morphology parameters. Second, CFD simulations, guided by in-situ observations, were conducted to model the wind field, with the Standard k-ɛ model validated as the optimal choice. …

Identifying The Effect Of Architecture Morphology On Wind Fields And Pm2.5 Dispersion At The Urban Block Scale Via A Combined Scheme, Bin Guo, Lu Li, Xiaowei Zhu, Zheng Wang, Miaoyi Chen, Lin Pei, Tengyue Guo

Mechanical and Materials Engineering Faculty Publications and Presentations

This study explores the potential of architecture morphology to mitigate PM2.5 pollution through enhanced urban ventilation. Despite the recognized influence of building designs on wind and air pollution distribution at the urban block scale, specific mechanisms remain poorly understood. To address this gap, we have developed an integrative approach combining in-situ observations, Geographic Information System (GIS), Remote Sensing (RS), Computational Fluid Dynamics (CFD), and statistical modeling. Here, CFD simulates the flow field and PM2.5 dispersion, using in-situ observations for turbulence model selection. GIS quantify architecture morphology parameters to establish accurate CFD boundary conditions, ensuring simulations reflect real-world conditions and precise …

A Mechanistic Study Of Silicon Nanocrystal Formation Via Solid State Synthesis, Katherine Mccarthy Weinfurter

Dissertations and Theses

Silicon nanocrystals (SiNCs) show promising physiochemical properties that could be used in industrial applications. The production of SiNCs through solid-state synthesis is ideal due to relatively low cost of equipment and chemical reagents, as well as the ability to scale-up production. A widely known and commonly used precursor previously used in solid-state synthesis for SiNCs, hydrogen silsesquioxane (HSiO_1.5), was discontinued in chemical manufacturing, which has led to researching alternative precursors (or starting materials). We have identified that there is a gap of knowledge related to producing these precursors, as well as the mechanistic understanding of the chemical reactions …

Bipolar Ionization Did Not Reduce Airborne Bacteria In A Lecture Hall, David A. Kormos, Nishit J. Shetty, Elliott T. Gall, Aaron J. Prussin, Amy Pruden, Linsey C. Marr

Mechanical and Materials Engineering Faculty Publications and Presentations

Ionization treatment of indoor air has attracted attention for its potential to inactivate airborne pathogens and reduce disease transmission, yet its real-world effectiveness remains unverified. We evaluated the impact of an in-duct, bipolar ionization system on airborne particles, including culturable bacteria, in a lecture hall. The ionizer was off with variable fan speed for 1 week, on with variable fan speed for a second week, and on with high and constant fan speed for a third week. We measured ion concentrations and aerosol particle concentrations, and we collected bioaerosol samples for analysis of 16S rRNA gene copies representing total bacteria …

Developing And Testing Low-Cost Air Cleaners For Safer Spaces During Wildfires, Brett W. Stinson, Elliott T. Gall

Mechanical and Materials Engineering Faculty Publications and Presentations

Air cleaning reduces indoor exposure to fine particulate matter (PM2.5) during wildfire smoke events. However, resource and cost constraints may limit access to air cleaning during such an event, as both commercial devices and the higher-rated MERV filters that do-it-yourself (DIY) assemblies typically rely upon tend to be expensive and in short supply. With these constraints in mind, we developed and evaluated several configurations of a novel, DIY air cleaner that uses common household fabrics as filtration media. Clean air delivery rates (CADRs) of the devices were experimentally evaluated in two ways: first, with independent measurements of flowrates and single …

Artificial Neural Network-Based Modelling For Yield Strength Prediction Of Austenitic Stainless-Steel Welds, Sukil Park, Cheolhee Kim, Namhyun Kang

Mechanical and Materials Engineering Faculty Publications and Presentations

This study aimed to develop an artificial neural network (ANN) model for predicting the yield strength of a weld metal composed of austenitic stainless steel and compare its performance with that of conventional multiple regression and machine learning models. The input parameters included the chemical composition of the nine effective elements (C, Si, Mn, P, S, Ni, Cr, Mo, and Cu) and the heat input per unit length. The ANN model (comprising five nodes in one hidden layer), which was constructed and trained using 60 data points, yielded an R² value of 0.94 and a mean average percent error …

Rheological Properties And 3d Printing Behavior Of Pcl And Dmso2 Composites For Bio-Scaffold, Jae-Won Jang, Kyung-Eun Min, Cheolhee Kim, Chien Wern, Sung Yi

Mechanical and Materials Engineering Faculty Publications and Presentations

The significance of rheology in the context of bio three-dimensional (3D) printing lies in its impact on the printing behavior, which shapes material flow and the layer-by-layer stacking process. The objective of this study is to evaluate the rheological and printing behaviors of polycaprolactone (PCL) and dimethyl sulfone (DMSO₂) composites. The rheological properties were examined using a rotational rheometer, employing a frequency sweep test. Simultaneously, the printing behavior was investigated using a material extrusion 3D printer, encompassing varying printing temperatures and pressures. Across the temperature range of 120–140 °C, both PCL and PCL/DMSO₂ composites demonstrated liquid-like behavior, …

Reducing Switching Noise And Losses In Two-Stage Electric Power Converters, Abhijeet Prem

Student Research Symposium

Advancements in semiconductor devices are enabling the design of better electrical power converter systems. Wide Bandgap (WBG) switching devices from Silicon Carbide and Gallium Nitride can operate at high temperatures, voltages, and frequencies with faster turn-on/off periods, improving converter performance over silicon devices. However, WBG technology is still new, and the rapid switching transitions of these devices lead to issues such as voltage overshoots, ringing, and electromagnetic interference, which need to be addressed for widespread adoption. This work introduces a new control method for reshaping the switching voltages, which overcomes the disadvantages of fast transition time without increasing the system's …

Characterization Of Chopped Carbon Fiber Reinforced Composites Produced Using Fused Deposition Modeling, Jonathon Tran, Rachel Shubella

Student Research Symposium

Fused deposition modeling (FDM) is an additive manufacturing (AM) process which can create parts with complex geometries in their final shape without need for additional specialized tools or devices. The FDM process builds parts by adding material layer by layer only where it is needed, saving energy, costs, production time for complex parts, and minimizing waste. Fiber reinforcement can significantly enhance the mechanical properties of a polymer material and depends significantly on the fiber length distribution and fiber orientation distribution of the final part. In this research, we investigated the various infill patterns of FDM printed Markforged onyx which is …

Floating Wind Farm Experiments Through Scaling For Wake Characterization, Power Extraction, And Turbine Dynamics, Juliaan Bossuyt, OndˇRej FercˇÁk, Zein Sadek, Charles Meneveau, Dennice Gayme, Raúl Bayoán Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

In this study, wind and water tunnel experiments of turbulent wakes in a scaled floating wind farm are performed. Scaling of a floating wind farm with a scaling ratio of 1:400 is made possible by relaxing geometric scaling of the turbine platform system, such that the dynamic response can be correctly matched, and to allow for relaxing Froude scaling such that the Reynolds number can be kept large enough. Four dimensionless parameters, describing the relative importance of wind and wave loads compared to turbine inertia, are used to guide the scaled floater design. Free decay tests of the pitch and …

Uncovering Transient Dynamics And Equilibrium States Of Particle Aggregates With RaúL BayoáN Cal, RaúL BayoáN Cal

PDXPLORES Podcast

In this episode of PDXPLORES, Raúl Bayoán Cal, Professor of Mechanical & Materials Engineering at the Maseeh College of Engineering and Computer Science, discusses his latest National Science Foundation award-winning research, Uncovering Transient Dynamics and Equilibrium States of Particle Aggregates in Fluids, investigating transient dynamics of fluid mechanics in the absence of gravity. These experiments, which utilize the Dryden Drop Tower and research facilities aboard the International Space Station, will benefit the study of granular media in aggregation models such as pollen deposition, algae growth, and plastic pollution.

Click on the "Download" button to access the audio transcript.

An Experimental Study Of Norton And Thule Cooking Pot Performance, Caelie Marshall Butler

Dissertations and Theses

Ceramic technology was adopted by hunter-gatherers of the Paleo-Inuit Norton tradition in the Western Arctic between 2800 and 2500 years B.P., corresponding with an increase in the use of aquatic resources. Pottery production and use continued until approximately 1,500 BP, and resumed during the Neo-Inuit Birnirk and Thule periods, approximately 1,350 years BP. The technical characteristics of Norton and Thule ceramics suggest they performed differently when used for cooking, with Norton ceramics best suited for cooking using direct or suspended heat, and Thule ceramics best suited for indirect heat. Prior experimental archaeological research has focused on Thule ceramics, with limited …

Flow In Additively Manufactured Super-Rough Channels, Samuel Altland, Xiaowei Zhu, Stephen Mcclain, Robert Kunz, Xiang Yang

Mechanical and Materials Engineering Faculty Publications and Presentations

Metal additive manufacturing has enabled geometrically complex internal cooling channels for turbine and heat exchanger applications, but the process gives rise to large-scale roughness whose size is comparable to the channel height (which is 500 μm). These super-rough channels pose previously unseen challenges for experimental measurements, data interpretation and roughness modelling. First, it is not clear if measurements at a particular streamwise and spanwise location still provide accurate representation of the mean (time- and plane-averaged) flow. Second, we do not know if the logarithmic layer survives. Third, it is unknown how well previously developed rough-wall models work for these large-scale …

Materials And Methodologies For Spectroscopic And Optical Analytical Applications In Cultural Heritage Conservation Science, Lyndsay Nichole Kissell

Dissertations and Theses

The field of conservation science falls in the intersection of science and art. The work of conservation scientists may include any single subdiscipline of chemistry, though it is most commonly a highly interdisciplinary field taking skills from analytical, organic, and inorganic chemistry, as well as surface and materials science. The aims of conservation scientists are to answer questions about the production and aging of material cultural heritage. Knowing the materials used by an artist can lead to insight about the intentions of the object and knowing how those materials degrade will enable the use of preventative measures to ensure the …

Random Lasing In Nano-Crystalline Zinc-Oxide Films, Benito Reynaldo Resendiz

Dissertations and Theses

In this thesis, we explore the preparation of random lasers (RLs) using solution-deposited, randomly packed nano-particle films of zinc oxide (ZnO) impregnated with silicon dioxide (SiO₂) nanospheres. RLs have their scatterers randomly oriented, while their lasing comes from light propagating along closed paths through the scattering environment. It is shown here that random lasing is readily observed in films made of submicron sized ZnO particles. Adding transparent SiO₂ nanospheres to the films, we show there is an effective improvement of the lasing that is observable in all of the samples spectra. Specifically, we found that the lasing …

Improved Predictive Modeling Techniques For Non-Linear Solder Material Behavior, Arman Millian Ahari

Dissertations and Theses

Accurate prediction of fatigue life of solder joints in electronic packaging applications becomes of critical importance as semiconductor device technology and manufacturing constraints grow in complexity. To gain visibility on IC device performance and reliability, thermo-mechanical simulation is performed based on a unified, viscoplastic material model, which is dependent on nine parameters.

In this study, an improved method of Anand parameter extraction, which involves curve-fitting non-linear experimental stress data, is proposed to improve the accuracy of numerical predictions for solder reliability. Theoretical equations for uni-axial stress-strain response and creep response are derived, then details on their relevance to experimental and …

Optimization Of 3d Printed Mold Performance For Injection Molding Via Hollow Infill Patterns, Alan Fong

University Honors Theses

The applicability of hollow infill patterns has been explored for its applications in making 3D printed polymer-based injection molds in the additive manufacturing industry. Hollow infill patterns offer a significant reduction in material costs as well as the opportunity for reducing the cooling times via pumping a coolant fluid through the hollow cavity in a similar fashion to traditional conformal cooling channels. A 3D Jacks Support Hollow mold model was determined to be the best performing design. FEA analysis was conducted to determine the maximum reduction in internal volume (percentage of material saved) that could be achieved without exceeding the …

Impact Of Green And White Roofs On Air Handler Filters And Indoor Ventilation Air, Pradeep Ramasubramanian, Irvan Luhung, Serene B. Y. Lim, Stephan C. Schuster, Olyssa Starry, Elliott T. Gall

Mechanical and Materials Engineering Faculty Publications and Presentations

Rooftop surfaces near building outdoor air intakes may contribute to the mass loading on filters and compounds emitted to ventilation air downstream of the filter. In laboratory analyses, we characterized microbial composition, primary volatile organic compound (VOC) emissions, ozone removal rates, and VOC emissions in the presence of ozone on filters collected from air handlers located on the green and white roof sections of a big-box retail store. Total DNA masses per area of filter were 26.3 ± 11.9 ng cm−2 and 6.3 ± 6.5 ng cm−2 for green and white roof filters respectively, with higher mass observed in winter …

A Three-Dimensional Musculoskeletal Model Of The Dog, Heiko Stark, Martin S. Fischer, Alexander Hunt, Fletcher Young, Roger Quinn, Emanuel Andrada

Mechanical and Materials Engineering Faculty Publications and Presentations

Abstract The domestic dog is interesting to investigate because of the wide range of body size, body mass, and physique in the many breeds. In the last several years, the number of clinical and biomechanical studies on dog locomotion has increased. However, the relationship between body structure and joint load during locomotion, as well as between joint load and degenerative diseases of the locomotor system (e.g. dysplasia), are not sufficiently understood. Collecting this data through in vivo measurements/records of joint forces and loads on deep/small muscles is complex, invasive, and sometimes unethical. The use of detailed musculoskeletal models may help …

Lagrangian Diffusion Properties Of A Free Shear Turbulent Jet, Bianca F. Viggiano, Thomas Basset, Stephen Solovitz, Thomas Barois, Mathieu Gibert, Nicolas Mordant, Laurent Chevillard, Romain Volk, Mickael Bourgoin, Raul Bayoan Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

A Lagrangian experimental study of an axisymmetric turbulent water jet is performed to investigate the highly anisotropic and inhomogeneous flow field. Measurements are conducted within a Lagrangian exploration module, an icosahedron apparatus, to facilitate optical access of three cameras. Stereoscopic particle tracking velocimetry results in three-component tracks of position, velocity and acceleration of the tracer particles within the vertically oriented jet with a Taylor-based Reynolds number Reλ≃230. Analysis is performed at seven locations from 15 diameters up to 45 diameters downstream. Eulerian analysis is first carried out to obtain critical parameters of the jet and relevant scales, namely the Kolmogorov …

The Corrosion Of Stainless Steel Made By Additive Manufacturing: A Review, Gyeongbin Ko, Wooseok Kim, Kyungjung Kwon, Tae-Kyu Lee

Mechanical and Materials Engineering Faculty Publications and Presentations

The advantages of additive manufacturing (AM) of metals over traditional manufacturing methods have triggered many relevant studies comparing the mechanical properties, corrosion behavior, and microstructure of metals produced by AM or traditional manufacturing methods. This review focuses exclusively on the corrosion property of AM-fabricated stainless steel by comprehensively analyzing the relevant literature. The principles of various AM processes, which have been adopted in the corrosion study of stainless steel, and the corrosion behaviors of stainless steel depending on the AM process, the stainless steel type, and the corrosion environment are summarized. In this comprehensive analysis of relevant literature, we extract …

The Hot Cracking Susceptibility Subjected The Laser Beam Oscillation Welding On 6xxx Aluminum Alloy With A Partial Penetration Joint, Minjung Kang, Jason Cheon, Dong Hyuck Kam, Cheolhee Kim

Mechanical and Materials Engineering Faculty Publications and Presentations

A laser beam oscillation method using Galvano mirrors, which allows wide weld beads and controls thermal stress distribution, was suggested to suppress the formation of solidification cracks in laser welds. In order to understand the solidification cracking behavior in relation to the bead shape, laser beam oscillation welding was performed under various oscillation widths and frequency conditions. To evaluate the effect of the oscillation parameter on solidification cracking susceptibility, a regression analysis based on the shape of the bead was performed. Stress distribution generated during the laser beam oscillation welding process was also analyzed using finite element modeling simulation. From …

Development Of Graphene Synthesis And Characterization Techniques Toward Cmos Applications And Beyond, Otto Kno Zietz

Dissertations and Theses

Graphene exhibits mechanical and electrical properties which, coupled with its two dimensional (2D) morphology, make it an attractive material component for inclusion in a wide range of industries. Since the discovery of graphene in 2004, industry adoption has been limited due to the demanding synthesis requirements for high quality and connected graphene as well as the difficulties associated with direct incorporation. Chemical vapor deposition (CVD) has emerged as the most cost efficient method for producing high quality graphene at scales suitable for mass production. However, the 1000°C temperatures and micrometer thick catalysts required for this process preclude direct inclusion in …

Enhanced Carrier Transport By Transition Metal Doping In Ws2 Field Effect Transistors, Maomao Liu, Sichen Wei, Simran Shahi, Hemendra Nath Jaiswal, Paolo Paletti, Sara Fathipour, Maja Remskar, Jun Jiao, Wansik Hwang, Fei Yao, Huamin Li

Physics Faculty Publications and Presentations

High contact resistance is one of the primary concerns for electronic device applications of two-dimensional (2D) layered semiconductors. Here, we explore the enhanced carrier transport through metal–semiconductor interfaces in WS₂ field effect transistors (FETs) by introducing a typical transition metal, Cu, with two different doping strategies: (i) a “generalized” Cu doping by using randomly distributed Cu atoms along the channel and (ii) a “localized” Cu doping by adapting an ultrathin Cu layer at the metal–semiconductor interface. Compared to the pristine WS₂ FETs, both the generalized Cu atomic dopant and localized Cu contact decoration can provide a Schottky-to-Ohmic contact …

Parametric Investigation Of Effect Of Abnormal Process Conditions On Self-Piercing Riveting, Taek-Eon Jeong, Dong-Hyuck Kam, Cheolhee Kim

Mechanical and Materials Engineering Faculty Publications and Presentations

Self-piercing riveting (SPR) is one of the mechanical joining processes, and its application to Al/Fe dissimilar materials combination, which is hard to weld, is expanding in the automotive industry. The main process parameters in SPR are types of rivet and die, setting force, and rivet setting speed. Previously, the relationship between the main process parameters and output parameters such as cross-sectional characteristics and joint strength has been studied to optimize the SPR process. In practical applications, there are unexpected and abnormal process conditions such as poor fit-up, angular misalignment, edge offset distance, and inaccurate setting and pre-clamping forces, and their …

Ten Questions Concerning The Implications Of Carpet On Indoor Chemistry And Microbiology, Sarah R, Haines, Rachel I. Adams, Brandon E. Boor, Thomas A. Bruton, John Downey, Andrea R. Ferro, Elliott T. Gall, Multiple Additional Authors

Mechanical and Materials Engineering Faculty Publications and Presentations

Carpet and rugs currently represent about half of the United States flooring market and offer many benefits as a flooring type. How carpets influence our exposure to both microorganisms and chemicals in indoor environments has important health implications but is not well understood. The goal of this manuscript is to consolidate what is known about how carpet impacts indoor chemistry and microbiology, as well as to identify the important research gaps that remain. After describing the current use of carpet indoors, questions focus on five specific areas: 1) indoor chemistry, 2) indoor microbiology, 3) resuspension and exposure, 4) current practices …