Nanoscience and Nanotechnology Commons^™

Enhancing Stability And Efficiency Of Perovskite Solar Cells With Crosslinkable Silane-Functionalized And Doped Fullerene, Yang Bai, Qingfeng Dong, Yuchuan Shao, Yehao Deng, Qi Wang, Liang Shen, Dong Wang, Wei Wei, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

The instability of hybrid perovskite materials due to water and moisture arises as one major challenge to be addressed before any practical application of the demonstrated high efficiency perovskite solar cells. Here we report a facile strategy that can simultaneously enhance the stability and efficiency of p–i–n planar heterojunction-structure perovskite devices. Crosslinkable silane molecules with hydrophobic functional groups are bonded onto fullerene to make the fullerene layer highly water-resistant. Methylammonium iodide is introduced in the fullerene layer for n-doping via anion-induced electron transfer, resulting in dramatically increased conductivity over 100-fold. With crosslinkable silane-functionalized and doped fullerene electron transport layer, the …

Stabilized Wide Bandgap MapbbrXI3– X Perovskite By Enhanced Grain Size And Improved Crystallinity, Miao Hu, Cheng Bi, Yongbo Yuan, Yang Bai, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Methylammonium lead trihalide perovskite (MAPbX₃, where MA is methylammonium, and X is a halide)-based solar cells have been intensively investigated recently, with the demonstrated certified solar power conversion efficiency (PCE) exceeding 20%. To further boost the PCE to beyond the Schockley–Queisser limit, tandem structured solar cells have been investigated based on integrating MAPbX₃ and low bandgap solar cells. However, the efficiency of the two-terminal integrated perovskite-silicon tandem cells is still low. The best reported efficiency of 13.7% for this type of tandem cells is far smaller than the individual cells yet, partially due to the limited performance …

Ultrahigh Sensitivity Of Methylammonium Lead Tribromide Perovskite Single Crystals To Environmental Gases, Hong-Hua Fang, Sampson Adjokatse, Haotong Wei, Jie Yang, Graeme R. Blake, Jinsong Huang, Jacky Even, Maria Antonietta Loi

Department of Mechanical and Materials Engineering: Faculty Publications

One of the limiting factors to high device performance in photovoltaics is the presence of surface traps. Hence, the understanding and control of carrier recombination at the surface of organic-inorganic hybrid perovskite is critical for the design and optimization of devices with this material as the active layer. We demonstrate that the surface recombination rate (or surface trap state density) inmethylammonium lead tribromide (MAPbBr3) single crystals can be fully and reversibly controlled by the physisorption of oxygen and water molecules, leading to a modulation of the photoluminescence intensity by over two orders of magnitude.We report an unusually low surface recombination …

Pulsed Laser Cutting Of Magnesium-Calcium For Biodegradable Stents, M. P. Sealy, Y. B. Guo, J. F. Liu, C. Li

Department of Mechanical and Materials Engineering: Faculty Publications

There is growing interests in the use of biodegradable magnesium implants for cardiovascular and pulmonary applications such as stents. Magnesium is a metal that has the ability to gradually dissolve and absorb into the human body after implantation. There is very little work discussing the relationship between process parameters and cut quality of magnesium stents by laser cutting. The objective of this research is to determine the effect of laser cutting conditions including peak laser power and cutting speed of a millisecond range pulsed laser on kerf geometry, surface topography, surface roughness, and microstructure. An assessment on the experimental work …

Impact Of Patient Factors On Operative Duration During Laparoscopic Cholecystectomy: Evaluation From The National Surgical Quality Improvement Program Database, Bethany Rose Lowndes, Cornelius A. Thiels, Elizabeth B. Habermann, Juliane Bingener, M. Susan Hallbeck, Denny Yu

Department of Mechanical and Materials Engineering: Faculty Publications

BACKGROUND: Patient factors impact laparoscopic cholecystectomy (LC) difficulty, specifically operative duration. This study quantifies the impact of patient factors on LC duration.

METHODS: The national surgery database (American College of Surgeons National Surgical Quality Improvement Program) was reviewed for all elective LC for biliary colic from 2005 to 2013. Multivariate general linear model and logistic regression were used to evaluate patient factors as predictors of operative duration greater than 60 minutes, adjusted for resident involvement and cholangiography.

RESULTS: A total of 24,099 LC met inclusion criteria. Regression analysis found procedure duration greater than 60 minutes was less likely for patients …

A Comparative Study On Machining Capabilities Of Wet And Dry Nanoscale Electro-Machining, Muhammad P. Jahan, Kamlakar P. Rajurkar, Ajay P. Malshe

Department of Mechanical and Materials Engineering: Faculty Publications

Presently, the nano scale electro-machining (nano-EM) process has been demonstrated in both the liquid and air dielectric mediums, which are known as wet and dry nano-EM respectively. In the current study, two important aspects of the nano-EM have been investigated: the minimum possible feature dimension and mass fabrication capability of nano-EM. Firstly, the investigation has been done on the capability of machining graphene at atomic scale with focus on obtaining smallest possible nano-feature using the wet nano-EM. Secondly, the ability of the nano-EM process for the fabrication of arrays of nano-holes has been investigated using dry nano-EM. It was found …

Bioink Properties Before, During And After 3d Bioprinting, Katja Holzl, Shengmao Lin, Liesbeth Tytgat, Sandra Van Vlierberghe, Linxia Gu, Aleksandr Ovsianikov

Department of Mechanical and Materials Engineering: Faculty Publications

Bioprinting is a process based on additive manufacturing from materials containing living cells. These materials, often referred to as bioink, are based on cytocompatible hydrogel precursor formulations, which gel in a manner compatible with different bioprinting approaches. The bioink properties before, during and after gelation are essential for its printability, comprising such features as achievable structural resolution, shape fidelity and cell survival. However, it is the final properties of the matured bioprinted tissue construct that are crucial for the end application. During tissue formation these properties are influenced by the amount of cells present in the construct, their proliferation, migration …

Development Of A Synthetic Gene Network To Modulate Gene Expression By Mechanical Forces, Zoltan Kis, Tania Rodin, Asma Zafar, Zhangxing Lai, Grace Freke, Oliver Fleck, Armando Del Rio Hernandez, Leila Towhidi, Ryan M. Pedrigi, Takayuki Homma, Rob Krams

Department of Mechanical and Materials Engineering: Faculty Publications

The majority of (mammalian) cells in our body are sensitive to mechanical forces, but little work has been done to develop assays to monitor mechanosensor activity. Furthermore, it is currently impossible to use mechanosensor activity to drive gene expression. To address these needs, we developed the first mammalian mechanosensitive synthetic gene network to monitor endothelial cell shear stress levels and directly modulate expression of an atheroprotective transcription factor by shear stress. The technique is highly modular, easily scalable and allows graded control of gene expression by mechanical stimuli in hard-to-transfect mammalian cells. We call this new approach mechanosyngenetics. To insert …

Portable Camera Aided Simulator (Portcas) For Minimally Invasive Surgical Training, Ka-Chun Sui, Carl Nelson, Mohsen Zahiri, Dmitry Oleynikov

Department of Mechanical and Materials Engineering: Faculty Publications

The present disclosure is directed to a system and method for surgical training with low cost, reusable materials and a highly customizable virtual environment for skill-building. According to various embodiments, a surgical training tool is usable in conjunction with a support structure configured to at least partially constrain the tool movement. Meanwhile, the tool is tracked in real-time with off-tool detectors to generate a tool path driving a virtual rendering of the surgical training tool in an operative environment. The virtual rendering may be visually observable via a display device and may include a customizable and/or selectable operative environment with …

Secondary Pool Boiling Effects, C. Kruse, A. Tsubaki, C. A. Zuhlke, T. P. Anderson, Dennis R. Alexander, George Gogos, Sidy Ndao

Department of Mechanical and Materials Engineering: Faculty Publications

A pool boiling phenomenon referred to as secondary boiling effects is discussed. Based on the experimental trends, a mechanism is proposed that identifies the parameters that lead to this phenomenon. Secondary boiling effects refer to a distinct decrease in the wall superheat temperature near the critical heat flux due to a significant increase in the heat transfer coefficient. Recent pool boiling heat transfer experiments using femtosecond laser processed Inconel, stainless steel, and copper multiscale surfaces consistently displayed secondary boiling effects, which were found to be a result of both temperature drop along the microstructures and nucleation characteristic length scales. The …

Experimental Explanation Of The Formation Mechanism Of Surface Mound-Structures By Femtosecond Laser On Polycrystalline Ni60Nb40, Edwin Peng, A. Tsubaki, Craig A. Zuhlke, Meiyu Wang, Ryan Bell, Michael J. Lucis, Troy P. Anderson, Dennis R. Alexander, George Gogos, Jeffrey E. Shield

Department of Mechanical and Materials Engineering: Faculty Publications

Femtosecond laser surface processing (FLSP) is an emerging technique for creating functionalized surfaces with specialized properties, such as broadband optical absorption or superhydrophobicity/ superhydrophilicity. It has been demonstrated in the past that FLSP can be used to form two distinct classes of mound-like, self-organized micro/nanostructures on the surfaces of various metals. Here, the formation mechanisms of below surface growth (BSG) and above surface growth (ASG) mounds on polycrystalline Ni₆₀Nb₄₀ are studied. Cross-sectional imaging of these mounds by focused ion beam milling and subsequent scanning electron microscopy revealed evidence of the unique formation processes for each class of …

An Assessment Of The Validity Of The Kinetic Model For Liquid-Vapor Phase Change By Examining Cryogenic Propellants, Kishan Bellur

Dissertations, Master's Theses and Master's Reports

Evaporation is ubiquitous in nature and occurs even in a microgravity space envi- ronment. Long term space missions require storage of cryogenic propellents and an accurate prediction of phase change rates. Kinetic theory has been used to model and predict evaporation rates for over a century but the reported values of accommodation coefficients are highly inconsistent and no accurate data is available for cryogens. The proposed study involves a combined experimental and computational approach to ex- tract the accommodation coefficients. Neutron imaging is used as the visualization technique due to the difference in attenuation between the cryogen and the metallic …

Turning An Organic Semiconductor Into A Low-Resistance Material By Ion Implantation, Beatrice Fraboni, Alessandra Scidà, Piero Cosseddu, Yongqiang Wang, Michael Nastasi, Silvia Milita, Annalisa Bonfiglio

Nebraska Center for Energy Sciences Research: Publications

We report on the effects of low energy ion implantation on thin films of pentacene, carried out to investigate the efficacy of this process in the fabrication of organic electronic devices. Two different ions, Ne and N, have been implanted and compared, to assess the effects of different reactivity within the hydrocarbon matrix. Strong modification of the electrical conductivity, stable in time, is observed following ion implantation. This effect is significantly larger for N implants (up to six orders of magnitude), which are shown to introduce stable charged species within the hydrocarbon matrix, not only damage as is the case …

Imaging Thermal Conductivity With Nanoscale Resolution Using A Scanning Spin Probe, Abdelghani Laraoui, Halley Aycock-Rizzo, Yang Gao, Xi Lu, Elisa Riedo, Carlos A. Meriles

Department of Mechanical and Materials Engineering: Faculty Publications

The ability to probe nanoscale heat flow in a material is often limited by lack of spatial resolution. Here, we use a diamond-nanocrystal-hosted nitrogen-vacancy centre attached to the apex of a silicon thermal tip as a local temperature sensor. We apply an electrical current to heat up the tip and rely on the nitrogen vacancy to monitor the thermal changes the tip experiences as it is brought into contact with surfaces of varying thermal conductivity. By combining atomic force and confocal microscopy, we image phantom microstructures with nanoscale resolution, and attain excellent agreement between the thermal conductivity and topographic maps. …

Nanomechanical And Nanotribological Characterization Of Sub-Micron Polymeric Spheres, Himanshu Kumar Verma

USF Tampa Graduate Theses and Dissertations

Friction between nanoscale objects has been a subject of great interest and intense research effort for the last two decades. However, the vast majority of the work done in this area has focused upon the sliding friction between two rigid, atomically smooth surfaces. Thus the parameter most explored has been the corrugation in the atomic potentials and how this affects the force required to slide one object across another. In truth, many nanoscale objects whose translation force is of practical interest are more spherical in nature. We hypothesize that the factors that determine the translation force will be related, not …

System And Method For Estimating States Of Spacecraft In Planet-Moon Environment, Piyush Grover

Department of Mechanical and Materials Engineering: Faculty Publications

A method estimates a state of a spacecraft in a planet-moon environment by executing iteratively a particle filter. The particle filter comprising integrates individually states of each particle of the particle filter according to a probability-evolution equation using a model of the state of the spacecraft represented as a planar circular restricted three-body problem and determines a prior probability of each particle as a previous posterior probability of a corresponding particle during a previous iteration. A joint probability distribution of the state of the spacecraft is determines using the states of each particle and the prior probabilities of each particle …

Entry Flow And Heat Transfer Of Laminar And Turbulent Forced Convection Of Nanofluids In A Pipe And A Channel, Yihe Huang

McKelvey School of Engineering Graduate Student Theses & Dissertations

This thesis presents a numerical investigation of laminar and turbulent fluid flow and convective heat transfer of nanofluids in the entrance and fully developed regions of flow in a channel and a pipe. In recent years, nanofluids have attracted attention as promising heat transfer fluids in many industrial processes due to their high thermal conductivity. Nanofluids consist of a suspension of nanometer-sized particles of higher thermal conductivity in a liquid such as water. The thermal conductivity of nanoparticles is typically an order-of-magnitude higher than the base liquid, which results in a significant increase in the thermal performance of the nanofluid …

Fabrication Of Cellulose Fine Fiber Based Membranes Embedded With Silver Nanoparticles Via Forcespinning, Fenghua Xu, Baicheng Weng, Luis A. Materon, Anxiu Kuang, Jorge A. Trujillo, Karen Lozano

Mechanical Engineering Faculty Publications

This study presents the successful development of cellulose fiber based membranes embedded with silver nanoparticles. These fine fiber membranes were developed utilizing the Forcespinning (FS) technique followed by alkaline hydrolysis treatment. The fiber morphology, homogeneity and yield were optimized by varying spinning parameters such as polymer concentration and angular velocity of the spinnerets. The structure, thermal and mechanical properties, and water absorption capability of the developed membranes were investigated. The cellulose acetate (CA) present in the membrane was converted to cellulose in the presence of embedded silver nanoparticles by alkaline hydrolysis. The silver nanoparticles embedded cellulose membrane exhibits outstanding water …

3d Printing Nanostructured Thermoelectric Device, Qianru Jia, Collier Miers, Amy Marconnet

The Summer Undergraduate Research Fellowship (SURF) Symposium

Thermoelectric materials convert thermal energy to electrical energy and vice versa. Thermoelectrics have attracted much attention and research efforts due to the possibility solving electronic cooling problems and reducing energy consumption through waste heat recovery. The efficiency of a thermoelectric material is determined by the dimensionless figure of merit ZT, which depends on both thermal and electrical properties. Researchers have worked for several decades to improve the ZT, but there had been little progress until nanomaterials and nanofabrication became widely available. Nanotechnology makes the ZT enhancement attainable by disconnecting the linkage between thermal and electrical transport. Printing customized, flexible thermoelectric …

Fracture Mechanics-Based Simulation Of Pv Module Delamination, Dominic I. Jarecki, Johanna B. Palsdottir, Peter Bermel, Marisol Koslowski

The Summer Undergraduate Research Fellowship (SURF) Symposium

Photovoltaic (PV) cells are rapidly growing as a renewable alternative to fossil fuels like coal, oil, and natural gas. However, greater adoption has also reduced government subsidies, placing the onus of making solar panels economically competitive on innovative research. While multiple methods have been considered for reducing costs, with each reduction in cost comes the associated peril of reduction in quality and useful lifetime. Several problems considered solved have now resurfaced as potential failure mechanisms with the introduction of cheaper PV cell technologies. However, to remain economically viable, PV modules will not only have to become cheaper, they will have …

Development Of A Shape Memory Polymer Soft Microgripper, Marshall Tatro, David J. Cappelleri, Wuming Jing

The Summer Undergraduate Research Fellowship (SURF) Symposium

The ability to control microrobots by means of magnetic fields has become of increasing interest to researchers. These robots’ ability to reach places tethered microrobots otherwise could not leads to many possible applications in the body, such as delivering drugs to targeted locations and performing biopsies. This study shows the use of shape memory polymer (SMP) to wirelessly actuate a microgripper to be used by a controllable microrobot to achieve these functions. Many smart materials were analyzed in order to find the material that most effectively would accomplish wirelessly gripping, manipulating, and releasing a microobject. Multiple microgripper designs were designed, …

An Estimate Of The Second-Order In-Plane Acceleration Sensitivity Of A Y-Cut Quartz Thickness-Shear Resonator, Huijing He, Jiashi Yang, John A. Kosinski

Department of Mechanical and Materials Engineering: Faculty Publications

We perform a theoretical analysis of the second-order in-plane acceleration sensitivity of a Y-cut quartz thick-ness-shear mode resonator. The second-order nonlinear theory of elasticity for anisotropic crystals is used to determine the biasing fields in the resonator under in-plane acceleration. The acceleration-induced frequency shift is determined from a per-turbation analysis based on the plate equations for small-amplitude vibrations superposed on a finite bias. We show that, whereas the first-order acceleration-induced frequency shift is zero for a structurally symmetric resonator under in-plane ac-celeration, the second-order frequency shift is nonzero and is quadratic in the acceleration. As the fourth-order nonlinear elastic constants …

Three-Dimensional Scaffolds Of Graphene, Carbon Nanotubes And Transition-Metal Oxides For Applications In Electronics, Sensors And Energy Storage, Gilbert N. Mbah

Department of Chemistry: Dissertations, Theses, and Student Research

Electronics, sensors and energy storage devices are the new waves behind economic development, security and communication¹. Engineering small sizes of electronic, sensors and energy storage devices is the hurdle limiting efficient, portable and vast applications of Nano-devices for economic, security and communication advancement². Silicon the major material used in transistors has approached its limit to fabricated Nano-devices³. The discovery of free standing, one atomic layer thick and two-dimensional graphene sheets with high conductivity, inert, high specific surface area, stable and high tensile strength material in 2004 has shown capabilities to replaced silicon in electronics, …

Biodegradable Medical Device Having An Adjustable Degradation Rate And Methods Of Making The Same, Yuebin Guo, Michael Sealy, Meisam Salahshoor Pirsoltan

Department of Mechanical and Materials Engineering: Faculty Publications

Disclosed herein are biodegradable medical devices comprising biodegradable material (e.g., magnesium-calcium alloys) having an adjustable rate of degradation that can be used in various applications, including, but not limited to, drug delivery applications, cardiovascular applications, and orthopedic applications to make biodegradable and biocompatible devices. Also disclosed herein are methods of making biodegradable medical devices comprising biodegradable materials by using, for instance, hybrid dry cutting/hydrostatic burnishing.

Traction-Separation Relationships For Hydrogen-Induced Grain Boundary Embrittlement In Nickel Via Molecular Dynamics Simulations, Wesley Allen Barrows

Graduate Theses and Dissertations

The deleterious effects of atomic and molecular hydrogen on the mechanical properties of metals have long been observed. Although several theories exist describing the mechanisms by which hydrogen negatively influences the failure of materials, a consensus has yet to be reached regarding the exact mechanism or combination of mechanisms. Two mechanisms have gained support in explaining hydrogen’s degradative role in non-hydride forming metals: hydrogen-enhanced localized plasticity and hydrogen-enhanced decohesion. Yet, the interplay between these mechanisms and microstructure in metallic materials has not been explained. Accordingly, for this thesis, the three main objectives are: (i) to develop a numerical methodology to …

Nano Scale Mechanical Analysis Of Biomaterials Using Atomic Force Microscopy, Diganta Dutta

Mechanical & Aerospace Engineering Theses & Dissertations

The atomic force microscope (AFM) is a probe-based microscope that uses nanoscale and structural imaging where high resolution is desired. AFM has also been used in mechanical, electrical, and thermal engineering applications. This unique technique provides vital local material properties like the modulus of elasticity, hardness, surface potential, Hamaker constant, and the surface charge density from force versus displacement curve. Therefore, AFM was used to measure both the diameter and mechanical properties of the collagen nanostraws in human costal cartilage. Human costal cartilage forms a bridge between the sternum and bony ribs. The chest wall of some humans is deformed …

Non-Wetting Surface-Driven High-Aspect-Ratio Crystalline Grain Growth For Efficient Hybrid Perovskite Solar Cells, Cheng Bi, Qi Wang, Yongbo Yuan, Zhengguo Xiao, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Large-aspect-ratio grains are needed in polycrystalline thin-film solar cells for reduced charge recombination at grain boundaries; however, the grain size in organolead trihalide perovskite (OTP) films is generally limited by the film thickness. Here we report the growth of OTP grains with high average aspect ratio of 2.3–7.9 on a wide range of non-wetting hole transport layers (HTLs), which increase nucleus spacing by suppressing heterogeneous nucleation and facilitate grain boundary migration in grain growth by imposing less drag force. The reduced grain boundary area and improved crystallinity dramatically reduce the charge recombination in OTP thin films to the level in …

Local Control Robotic Surgical Devices And Related Methods, Eric Markvicka, Tom Frederick, Jack Mondry, Joe Bartels, Shane Farritor

Department of Mechanical and Materials Engineering: Faculty Publications

The various robotic medical devices include robotic devices that are disposed within a body cavity and positioned using a support component disposed through an orifice or opening in the body cavity. Additional embodiments relate to devices having arms coupled to a device body wherein the device has a minimal profile such that the device can be easily inserted through smaller incisions in comparison to other devices without such a small profile. Further embodiments relate to methods of operating the above devices.

Modeling And Analysis Of A Resonant Nanosystem, Scott L. Calvert

Open Access Theses

The majority of investigations into nanoelectromechanical resonators focus on a single area of the resonator's function. This focus varies from the development of a model for a beam's vibration, to the modeling of electrostatic forces, to a qualitative explanation of experimentally-obtained currents. Despite these efforts, there remains a gap between these works, and the level of sophistication needed to truly design nanoresonant systems for efficient commercial use. Towards this end, a comprehensive system model for both a nanobeam resonator and its related experimental setup is proposed. Furthermore, a simulation arrangement is suggested as a method for facilitating the study of …

Freezing-Induced Deformation Of Biomaterials In Cryomedicine, Altug Ozcelikkale

Open Access Dissertations

Cryomedicine utilizes low temperature treatments of biological proteins, cells and tissues for cryopreservation, materials processing and cryotherapy. Lack of proper understanding of cryodamage that occurs during these applications remains to be the primary bottleneck for development of successful tissue cryopreservation and cryosurgery procedures. An engineering approach based on a view of biological systems as functional biomaterials can help identify, predict and control the primary cryodamage mechanisms by developing an understanding of underlying freezing-induced biophysical processes. In particular, freezing constitutes the main structural/mechanical origin of cryodamage and results in significant deformation of biomaterials at multiple length scales. Understanding of these freezing-induced …