Mechanics of Materials Commons^™

Efficiency Enhancement In Polymer Solar Cells With A Polar Small Molecule Both At Interface And In The Bulk Heterojunction Layer, Zhengguo Xiao, Qingfeng Dong, Qi Wang, Wenjing Tian, Hui Huang, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

The polar molecules, including ferroelectric materials with large dipole moments, have been applied as interfacial layers to increase the efficiency of organic solar cells by increasing the bounded charge separation, tuning the energy levels, etc. Here, we report a small polar molecule 2-cyano-3- (4-(diphenylamino) phenyl)acrylic acid (TPACA) that can be either blended in the active layer or at the polymer/electrode interface to increase the efficiency of organic solar cell devices after poling. It is found that the built-in potential of the device is increased by 0.2 V after poling under negative bias. Blending TPACA into the active layer has shown …

Electron-Hole Diffusion Lengths >175 Μm In Solution-Grown Ch3Nh3Pbi3 Single Crystals, Qingfeng Dong, Yanjun Fang, Yuchuan Shao, Padhraic Mulligan, Jie Qiu, Lei Cao, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Long, balanced electron and hole diffusion lengths greater than 100 nanometers in polycrystalline CH₃NH₃PbI₃ are critical for highly efficient perovskite solar cells. We report that the diffusion lengths in CH₃NH₃PbI₃ single crystals grown by a solution-growth method can exceed 175 μm under 1 sun illumination and exceed 3 mm under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3 mm-thick single crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, lifetime and dramatically smaller trap densities in …

Towards Tuning The Mechanical Properties Of Three-Dimensional Collagen Scaffolds Using A Coupled Fiber-Matrix Model, Shengmao Lin, Lauren A. Hapach, Cynthia Reinhart-King, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Scaffold mechanical properties are essential in regulating the microenvironment of three-dimensional cell culture. A coupled fiber-matrix numerical model was developed in this work for predicting the mechanical response of collagen scaffolds subjected to various levels of non-enzymatic glycation and collagen concentrations. The scaffold was simulated by a Voronoi network embedded in a matrix. The computational model was validated using published experimental data. Results indicate that both non-enzymatic glycation-induced matrix stiffening and fiber network density, as regulated by collagen concentration, influence scaffold behavior. The heterogeneous stress patterns of the scaffold were induced by the interfacial mechanics between the collagen fiber network …

Development And Preliminary Evaluation Of A Spray Deposition Sensing System For Improving Pesticide Application, Melissa A. Kesterson, Joe D. Luck, Michael P. Sama

Department of Mechanical and Materials Engineering: Faculty Publications

An electronic, resistance-based sensor array and data acquisition system was developed to measure spray deposition from hydraulic nozzles. The sensor surface consisted of several parallel tin plated copper traces of varying widths with varying gap widths. The system contained an embedded microprocessor to monitor output voltage corresponding to spray deposition every second. In addition, a wireless module was used to transmit the voltage values to a remote laptop. Tests were conducted in two stages to evaluate the performance of the sensor array in an attempt to quantify the spray deposition. Initial tests utilized manual droplet placement on the sensor surface …

Multiscale Modeling Of Skeletal Muscle Active Contraction In Relation To Mechanochemical Coupling Of Molecular Motors, Jiangcheng Chen, Xiaodong Zhang, Shengmao Lin, He Wang, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

In this work, a mathematical model was developed to relate the mechanochemical characterizations of molecular motors with the macroscopic manifestation of muscle contraction. Non-equilibrium statistical mechanics were used to study the collective behavior of myosin molecular motors in terms of the complex conformation change and multiple chemical states in one working cycle. The stochastic evolution of molecular motor probability density distribution during the contraction of sarcomere was characterized by the Fokker-Planck Equation. Quick muscle contraction was demonstrated by the collective dynamic behavior of myosin motors, the muscle contraction force, and the muscle contraction velocity-force relation. Our results are validated against …

Inducing Persistent Flow Disturbances Accelerates Atherogenesis And Promotes Thin Cap Fibroatheroma Development In D374y-Pcsk9 Hypercholesterolemic Minipigs, Ryan M. Pedrigi, Christian Bo Poulsen, Vikram V. Mehta, Niels Ramsing Holm, Nilesh Pareek, Anouk L. Post, Ismail Dogu Kilic, Winston A.S. Banya, Gianni Dall'ara, Alessio Mattesini, Martin M. Bjorklund, Niels P. Andersen, Anna K. Grondal, Enrico Petretto, Nicolas Foin, Justin E. Davies, Carlo Di Mario, Jacob Fog Bentzon, Hans Erik Botker, Erling Falk, Rob Krams, Ranil De Silva

Department of Mechanical and Materials Engineering: Faculty Publications

Background—Although disturbed flow is thought to play a central role in the development of advanced coronary atherosclerotic plaques, no causal relationship has been established. We evaluated whether inducing disturbed flow would cause the development of advanced coronary plaques, including thin cap fibroatheroma (TCFA).

Methods and Results—D374Y-PCSK9 hypercholesterolemic minipigs (N=5) were instrumented with an intracoronary shear-modifying stent (SMS). Frequency-domain optical coherence tomography was obtained at baseline, immediately post-stent, 19, and 34 weeks and used to compute shear stress metrics of disturbed flow. At 34 weeks, plaque type was assessed within serially-collected histological sections and co-registered to …

Self‑Propelled Droplets On Heated Surfaces With Angled Self‑Assembled Micro/Nanostructures, Cory Kruse, Isra Somanas, Troy Anderson, Chris Wilson, Craig Zuhlke, Dennis Alexander, George Gogos, Sidy Ndao

Department of Mechanical and Materials Engineering: Faculty Publications

Directional and ratchet-like functionalized surfaces can induce liquid transport without the use of an external force. In this paper, we investigate the motion of liquid droplets near the Leidenfrost temperature on functionalized self-assembled asymmetric microstructured surfaces. The surfaces, which have angled microstructures, display unidirectional properties. The surfaces are fabricated on stainless steel through the use of a femtosecond laser-assisted process. Through this process, mound-like microstructures are formed through a combination of material ablation, fluid flow, and material redeposition. In order to achieve the asymmetry of the microstructures, the femtosecond laser is directed at an angle with respect to the sample …

Quantification Of Ultraprecision Surface Morphology Using An Algebraic Graph Theoretic Approach, Prahalad Rao, Satish T. S. Bukkapatnam, Zhenyu (James) Kong, Omer F. Beyca, Kenneth Case, Ranga Komanduri

Department of Mechanical and Materials Engineering: Faculty Publications

Assessment of progressive, nano-scale variation of surface morphology during ultraprecision manufacturing processes, such as fine-abrasive polishing of semiconductor wafers, is a challenging proposition owing to limitations with traditional surface quantifiers. We present an algebraic graph theoretic approach that uses graph topological invariants for quantification of ultraprecision surface morphology. The graph theoretic approach captures heterogeneous multi-scaled aspects of surface morphology from optical micrographs, and is therefore valuable for in situ real-time assessment of surface quality. Extensive experimental investigations with specular finished (Sa ~ 5 nm) blanket copper wafers from a chemical mechanical planarization (CMP) process suggest that the proposed method was …

Evaluation Of Peritoneal Microbubble Oxygenation Therapy In A Rabbit Model Of Hypoxemia, Nathan D. Legband, Jameel A. Feshitan, Mark A. Borden, Benjamin S. Terry

Department of Mechanical and Materials Engineering: Faculty Publications

Alternative extrapulmonary oxygenation technologies are needed to treat patients suffering from severe hypoxemia refractory to mechanical ventilation. We previously demonstrated that peritoneal microbubble oxygenation (PMO), in which phospholipid-coated oxygen microbubbles (OMBs) are delivered into the peritoneal cavity, can successfully oxygenate rats suffering from a right pneumothorax. This study addressed the need to scale up the procedure to a larger animal with a splanchnic cardiac output similar to humans. Our results show that PMO therapy can double the survival time of rabbits experiencing complete tracheal occlusion from6.6 ± 0.6 min for the saline controls to 12.2 ± 3.0 min for the …

Enhanced Pool-Boiling Heat Transfer And Critical Heat Flux On Femtosecond Laser Processed Stainless Steel Surfaces, Cory M. Kruse, Troy Anderson, Chris Wilson, Craig Zuhlke, Dennis Alexander, George Gogos, Sidy Ndao

Department of Mechanical and Materials Engineering: Faculty Publications

In this paper, we present an experimental investigation of pool boiling heat transfer on multiscale (micro/nano) functionalized metallic surfaces. Heat transfer enhancement in metallic surfaces is very important for large scale high heat flux applications like in the nuclear power industry. The multiscale structures were fabricated via a femtosecond laser surface process (FLSP) technique, which forms self-organized mound-like microstructures covered by layers of nanoparticles. Using a pool boiling experimental setup with deionized water as the working fluid, both the heat transfer coefficients and critical heat flux were investigated. A polished reference sample was found to have a critical heat flux …

Microindentation Of Bi57in26sn17 Lead-Free Alloy, Ruiting Zhao

Theses and Dissertations--Chemical and Materials Engineering

There is great need to understand the mechanical properties of lead-free alloys—an alternative of lead-based alloys—to address the environmental problems associated with the use of lead-based materials in microelectronics. In this work, the microstructures of Bi57In26Sn17 lead-free alloy were examined using Optical Microscopy and Energy Dispersive X-ray Spectroscopy analysis. The micro-indentation technique was used to study the mechanical properties of Bi57In26Sn17 lead-free alloy. The experimental results of the hardness and contact modulus were presented and discussed. Local creep during the indentation was observed from the load-displacement curves. The Vickers hardness (HV) increases with the decrease of the indentation depth, suggesting …

Laparoscopic Devices And Methods Of Using, M. Susan Hallbeck, Jakeb Riggle, Adam De Laveaga, Jake Kaufman

Department of Mechanical and Materials Engineering: Faculty Publications

A number of improvements to laparoscopic devices are described herein, primarily to improve the ergonomic functionality of the devices. For example, an articulating rod system is described, a gripping mechanism is described, and an end effector is described

High Strength Steel Fiber Reinforced Flow-Able Or Scc Concrete With Variable Fiber By Volume Fractions For Thin Plate And Shell Structures, Abebe Berhe

UNLV Theses, Dissertations, Professional Papers, and Capstones

The purpose of this study is to incorporate discrete, short, mechanically deformed, small diameter steel fibers into high strength concrete with f'c > 70 MPa (10 ksi) in an attempt to reduce and partially eliminate the need for steel rebar in concrete construction. By introducing steel fibers to high strength concrete mixture, the overall tensile, compressive and shear strength of the mixture can be improved immensely thus, replacing portions or major parts of the longitudinal, temperature and shrinkage reinforcements. The reduction or elimination of longitudinal and transverse reinforcements in the construction of structural or non-structural members can result in savings in …

Two-Dimensional Scalar Differential Equations For Transversely Varying Thickness Modes In Piezoelectric Plates And Applications In Acoustic Wave Resonator Sensors, Huijing He

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Generalizations are made for three types of well-known and widely used twodimensional scalar differential equations in the literature describing transversely varying thickness modes in piezoelectric plate resonators. They are for singly-rotated quartz plates, doubly-rotated quartz plates, and plates of crystals of class 6mm with the c-axis along the plate thickness, respectively. The purpose of the generalizations is to include the effects of surface mechanical loads such as mass layers or fluids for resonator -based acoustic wave sensor applications. Surface acoustic impedance is introduced to take into account various surface loads in a general manner for time-harmonic motions. Both unelectroded and …

Modular And Cooperative Medical Devices And Related Systems And Methods, Shane M. Farritor, Mark Rentschler, Amy Lehman

Department of Mechanical and Materials Engineering: Faculty Publications

The various embodiments disclosed herein relate to modular medical devices, including various devices with detachable modular components and various devices with pivotally attached modular components. Additional embodiments relate to procedures in which various of the devices are used cooperatively. Certain embodiments of the medical devices are robotic in vivo devices.

Biphilic Nanoporous Surfaces Enabled Exceptional Drag Reduction And Capillary Evaporation Enhancement, Xianming Dai, Fanghao Yang, Ronggui Yang, Xinyu Huang, William A. Rigdon, Xiaodong Li, Chen Li

Faculty Publications

Simultaneously achieving drag reduction and capillary evaporation enhancement is highly desired but challenging because of the trade-off between two distinct hydrophobic and hydrophilic wettabilities. Here, we report a strategy to synthesize nanoscale biphilic surfaces to endow exceptional drag reduction through creating a unique slip boundary condition and fast capillary wetting by inducing nanoscopic hydrophilic areas. The biphilic nanoporous surfaces are synthesized by decorating hydrophilic functional groups on hydrophobic pristine multiwalled carbon nanotubes. We demonstrate that the carbon nanotube-enabled biphilic nanoporous surfaces lead to a 63.1% reduction of the friction coefficient, a 61.7% wetting speed improvement, and up to 158.6% enhancement …

Synthesis And Evaluation Of Sensitizer Drug Photorelease Chemistry: Micro-Optic Method Applied To Singlet Oxygen Generation And Drug Delivery, Goutam Ghosh

Dissertations, Theses, and Capstone Projects

This thesis summarizes a new micro-optic method for singlet oxygen generation and sensitizer drug delivery, which include i) synthesis and evaluation of a first generation device for drug delivery from native and fluorinated silica probe tips, ii) synthesis of PEG conjugated sensitizers to study phototoxicity in ovarian cancer cells, and iii) synthesis and evaluation of tris-PEGylated chlorin conjugated fluorinated silica for its future integration into the device to use as a 2nd generation device. A first generation micro-optic device was developed that works by sparging O2 gas and light generating cytotoxic singlet oxygen that cleaves the covalently attached drug (sensitizer) …

Characterization Of Wide Band Gap Semiconductors And Multiferroic Materials, Bo Cai

Dissertations, Theses, and Capstone Projects

Structural, optical and electrical properties of zinc oxide (ZnO), aluminum nitride (AlN), and lutetium ferrite (LuFe₂O4) have been investigated. Temperature dependent Hall Effect measurements were performed between 80 and 800 K for phosphorus (P) and arsenic (As) doped ZnO thin films grown on c-plane sapphire substrate by RF magnetron sputtering. These samples exhibited n-type conductivity throughout the temperature range with carrier concentration of 3.85 × 10 ¹⁶ cm^-3 and 3.65 × 10 ¹⁷ cm^-3 at room temperature for P-doped and As-doped ZnO films, respectively. The Arrhenius plots of free electron concentration of those doped samples showed …

Synthesis, Fabrication And Characterization Of Magnetic And Dielectric Nanoparticles And Nanocomposite Films, Xiaohua Liu

Dissertations, Theses, and Capstone Projects

Materials science is an interdisciplinary field investigating the structure-property relationship in solid-state materials scientifically and technologically. Nanoscience is concerned with the distinctive properties that matter exhibits when confined to physical dimensions on the order of 10^-9 meters. At these length scales, behaviors of particles or elaborate structures are often governed by the rules of quantum mechanics in addition to the physical properties associated with the bulk material.

The work reported here seeks to employ nanocystals, binary nanocomposites and thin films of materials, to build versatile, functional systems and devices. With a focus on dielectric, ferroelectric, and magnetoelectric performance, a …

Design Of Well-Defined Mesoporous Silicas Via Surfactant Templating Method Enhanced By The Use Of Swelling Agents, Tiffany Man

Dissertations, Theses, and Capstone Projects

Surfactant-templated ordered mesoporous materials continue to attract tremendous attention as these materials are characterized by reproducibility and predictability of their synthesis as well as their wide range of potential applications, which serve as future opportunities for additional advancement. The main purpose of this dissertation is to advance the understanding how to control the structural features and properties in the synthesis of well-defined porous materials via surfactant templating method, while keeping in mind that the uniformity of pore size and structural ordering are essential characteristics for these well-defined materials. The work was primarily focused on the issue of the unit-cell size …