Nanoscience and Nanotechnology Commons^™

Method For Single Crystal Growth Of Photovoltaic Perovskite Material And Devices, Jinsong Huang, Qingfeng Dong

Department of Mechanical and Materials Engineering: Faculty Publications

Systems and methods for perovskite single crystal growth include using a low temperature solution process that employs a temperature gradient in a perovskite solution in a container , also including at least one small perovskite single crystal , and a substrate in the solution upon which substrate a perovskite crystal nucleates and grows , in part due to the temperature gradient in the solution and in part due to a temperature gradient in the substrate . For example , a top portion of the substrate external to the solution may be cooled .

Oct-Based Three Dimensional Modeling Of Stent Deployment, Pengfei Dong, David Prabhu, David L. Wilson, Hiram G. Bezerra, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Stent deployment has been widely used to treat narrowed coronary artery. Its acute outcome in terms of stent under expansion and malapposition depends on the extent and shape of calcifications. However, no clear understanding as to how to quantify or categorize the impact of calcification. We have conducted ex vivo stenting characterized by the optical coherence tomography (OCT). The goal of this work is to capture the ex vivo stent deployment and quantify the effect of calcium morphology on the stenting. A three dimensional model of calcified plaque was reconstructed from ex vivo OCT images. The crimping, balloon expansion and …

Floating-Gate Transistor Photodetector, Jinsong Huang, Yongbo Yuan

Department of Mechanical and Materials Engineering: Faculty Publications

A field effect transistor photodetector that can operate in room temperature includes a source electrode , a drain electrode , a channel to allow an electric current to flow between the drain and source electrodes , and a gate electrode to receive a bias voltage for controlling the current in the channel . The photodetector includes a light - absorbing mate rial that absorbs light and traps electric charges . The light absorbing material is configured to generate one or more charges upon absorbing light having a wavelength within a specified range and to hold the one or more charges …

Software For Extracting Deformation Gradient And Stress From Md Simulations: Simulations Using The Charmm Force Field, Mehrdad Negahban, Lili Zhang, Zesheng Zhang, John Jasa, Antoine Jérusalem

Department of Mechanical and Materials Engineering: Faculty Publications

Software was developed, and is provided under a general use license, to calculate continuum level deformation gradient and stress for any group of atoms in an MD simulation that uses the Charmm force fields. This software can also calculate the interaction stress applied by one group of atoms on any other group. To obtain deformation gradient and stress, the user needs to provide the selected group(s) of atoms in an atom group identification file, and provide the associated LAMMPS format files and force field parameter file. An example is included to demonstrate the use of the software.

Energy Absorbing Guardrail System, John R. Rohde, John D. Reid, King K. Mak, Dean L. Sicking

Department of Mechanical and Materials Engineering: Faculty Publications

A highway crash attenuation system having W - beam rail elements attached to a plurality of vertical posts . An impact terminal with a feeder chute guides one or more of the W - beam rail elements through the impact terminal . The feeder chute has an impact shield extending along a traffic facing side of the chute from an upstream - most end to a downstream - most end of the chute closing the traffic - facing side of the chute . The system also has an anchor cable release mechanism for releasing the cable downstream of the first …

Shape-Adaptive Mechanism For Robotic Grasping, Carl A. Nelson

Department of Mechanical and Materials Engineering: Faculty Publications

A grapser can include a first pantograph cell and a second pantograph cell coupled with the first pantogrpah cell. The first and second pantograph cells can be coupled together at a first pivot and a second pivot. The grasper can also include a finger extendable in a direction extending between the first pivot and the second pivot. The grasper can include a support base, where one or more links of the first pantograph cell can be slidably coupled with the support base for extending the grasper. In some embodiment, the grasper can be configured to extend along a curved path. …

Meniscus-Assisted Solution Printing Of Largegrained Perovskite Films For High-Efficiency Solar Cells, Ming He, Bo Li, Xun Cui, Beibei Jiang, Yanjie He, Yihuang Chen, Daniel O'Neil, Paul Szymanski, Mostafa A. El-Sayed, Jinsong Huang, Zhiqun Lin

Department of Mechanical and Materials Engineering: Faculty Publications

Control over morphology and crystallinity of metal halide perovskite films is of key importance to enable high-performance optoelectronics. However, this remains particularly challenging for solution-printed devices due to the complex crystallization kinetics of semiconductor materials within dynamic flow of inks. Here we report a simple yet effective meniscus-assisted solution printing (MASP) strategy to yield large-grained dense perovskite film with good crystallization and preferred orientation. Intriguingly, the outward convective flow triggered by fast solvent evaporation at the edge of the meniscus ink imparts the transport of perovskite solutes, thus facilitating the growth of micrometre-scale perovskite grains. The growth kinetics of perovskite …

Dissipative Elastic Metamaterial With A Lowfrequency Passband, Yongquan Liu, Jianlin Yi, Zheng Li, Xianyue Su, Wenlong Li, Mehrdad Negahban

Department of Mechanical and Materials Engineering: Faculty Publications

We design and experimentally demonstrate a dissipative elastic metamaterial structure that functions as a bandpass filter with a low-frequency passband. The mechanism of dissipation in this structure is well described by a mass-spring-damper model that reveals that the imaginary part of the wavenumber is non-zero, even in the passband of dissipative metamaterials. This indicates that transmittance in this range can be low. A prototype for this viscoelastic metamaterial model is fabricated by 3D printing techniques using soft and hard acrylics as constituent materials. The transmittance of the printed metamaterial is measured and shows good agreement with theoretical predictions, demonstrating its …

Multiple Scattering Theory For Heterogeneous Elastic Continua With Strong Property Fluctuation: Theoretical Fundamentals And Applications, Huijing He

Department of Mechanical and Materials Engineering: Faculty Publications

Scattering of elastic waves in heterogeneous media has become one of the most important problems in the field of wave propagation due to its broad applications in seismology, natural resource exploration, ultrasonic nondestructive evaluation and biomedical ultrasound. Nevertheless, it is one of the most challenging problems because of the complicated medium inhomogeneity and the complexity of the elastodynamic equations. A widely accepted model for the propagation and scattering of elastic waves, which properly incorporates the multiple scattering phenomenon and the statistical information of the inhomogeneities is still missing. In this work, the author developed a multiple scattering model for heterogeneous …

A Strategy To Optimize Recovery In Orthopedic Sports Injuries, Michael P. Sealy, Ziye Liu, Chao Li, Yuebin Guo, Ben White, Mark Barkey, Brian Jordon J, Luke N. Brewer, Dale Feldman

Department of Mechanical and Materials Engineering: Faculty Publications

An important goal for treatment of sports injuries is to have as short a recovery time as possible. The critical problem with current orthopedic implants is that they are designed to be permanent and have a high complication rate (15%) that often requires removal and replacement with a second surgery; and subsequently a second rehabilitation cycle. This study was designed to test the feasibility of having a device that could provide the needed mechanical properties, while promoting healing, for a specified amount of time and then degrade away, to shorten the recovery time. The specific strategy was to create a …

Fabrication And Study Of The Structure And Magnetism Of Rare-Earth Free Nanoclusters, Bhaskar Das

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

No abstract provided.

Primary Blast Waves Induced Brain Dynamics Influenced By Head Orientations, Yi Hua, Yugang Wang, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

There is controversy regarding the directional dependence of head responses subjected to blast loading. The goal of this work is to characterize the role of head orientation in the mechanics of blast wave-head interactions as well as the load transmitting to the brain. A three-dimensional human head model with anatomical details was reconstructed from computed tomography images. Three different head orientations with respect to the oncoming blast wave, i.e., front-on with head facing blast, back-on with head facing away from blast, and side-on with right side exposed to blast, were considered. The reflected pressure at the blast wave-head interface positively …

Formation Of Mound-Like Multiscale Surface Structures On Titanium By Femtosecond Laser Processing, Edwin Peng, Alfred Tsubaki, Craig A. Zuhlke, Ryan Bell, Meiyu Wang, Dennis R. Alexander, George Gogos, Jeffrey E. Shield

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

Surface Functionalization Technique • Femtosecond Laser Surface Processing (FLSP) • Utilize high power, femtosecond (10-15 s) laser pulses • Produce self-organized, multiscale surface micro/nanostructures • Diverse range of applicable substrates: semiconductors, metals, polymers, & composites

Why? • What are the different types of FLSP structures on Ti? • Physical evidence needed for FLSP formation models • Optimize FLSP of Ti for biomedical & other applications

How? • Obtain evidence of mound growth processes by examining underlying microstructure • Utilize dual beam Scanning Electron Microscope-Focused Ion Beam instrument to cross section surface structures & fabricate transmission electron microscopy samples

Dirichlet Process Gaussian Mixture Models For Real-Time Monitoring And Their Application To Chemical Mechanical Planarization, Jia (Peter) Liu, Omer F. Beyca, Prahalad K. Rao, Zhenyu (James) Kong, Satish T. S. Bukkapatnam

Department of Mechanical and Materials Engineering: Faculty Publications

The goal of this work is to use sensor data for online detection and identification of process anomalies (faults). In pursuit of this goal, we propose Dirichlet process Gaussian mixture (DPGM) models. The proposed DPGM models have two novel outcomes: 1) DP-based statistical process control (SPC) chart for anomaly detection and 2) unsupervised recurrent hierarchical DP clustering model for identification of specific process anomalies. The presented DPGM models are validated using numerical simulation studies as well as wireless vibration signals acquired from an experimental semiconductor chemical mechanical planarization (CMP) test bed. Through these numerically simulated and experimental sensor data, we …

Vorticella: A Protozoan For Bio-Inspired Engineering, Sangjin Ryu, Rachel E. Pepper, Moeto Nagai, Danielle C. France

Department of Mechanical and Materials Engineering: Faculty Publications

In this review, we introduce Vorticella as a model biological micromachine for microscale engineering systems. Vorticella has two motile organelles: the oral cilia of the zooid and the contractile spasmoneme in the stalk. The oral cilia beat periodically, generating a water flow that translates food particles toward the animal at speeds in the order of 0.1–1 mm/s. The ciliary flow of Vorticella has been characterized by experimental measurement and theoretical modeling, and tested for flow control and mixing in microfluidic systems. The spasmoneme contracts in a few milliseconds, coiling the stalk and moving the zooid at 15–90 mm/s. Because the …

Benchmark Burnishing With Almen Strip For Surface Integrity, Z. Y. Liu, C. H. Fu, M. P. Sealy, Y. Zhao, Y. B. Guo

Department of Mechanical and Materials Engineering: Faculty Publications

Burnishing is a surface treatment process widely used in aerospace, navy and other industries to improve fatigue and corrosion resistance by introducing a compressive residual stress layer. The measurement of residual stress by XRD is expensive, time consuming, and tedious. This work presented a quick method to determine the residual stress by using Almen strips. Inspired by the application of Almen strips in shot peening, deflections of burnished Almen strips under different burnishing conditions were measured. It was found that the deflection of Almen strip reflects the magnitude and penetration depth into subsurface of induced stress. Higher burnishing force, smaller …

Methods , Systems , And Devices Relating To Surgical End Effectors, Shane M. Farritor, Tom Fredrick, Joe Bartels

Department of Mechanical and Materials Engineering: Faculty Publications

The embodiments disclosed herein relate to various medical device components, including components that can be incorporated into robotic and/or in vivo medical devices, and more specifically including end effectors that can be incorporated into such devices. Certain end effector embodiments include various vessel cautery devices that have rotational movement as well as cautery and cutting functions while maintaining a relatively compact structure. Other end effector embodiments include various end effector devices that have more than one end effector.

Strained Hybrid Perovskite Thin Films And Their Impact On The Intrinsic Stability Of Perovskite Solar Cells, Jingjing Zhao, Yehao Deng, Haotong Wei, Xiaopeng Zheng, Zhenhua Yu, Yuchuan Shao, Jeffrey E. Shield, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Organic-inorganic hybrid perovskite (OIHP) solar cells have achieved comparable efficiencies to those of commercial solar cells, although their instability hinders their commercialization. Although encapsulation techniques have been developed to protect OIHP solar cells from external stimuli such as moisture, oxygen, and ultraviolet light, understanding of the origin of the intrinsic instability of perovskite films is needed to improve their stability. We show that the OIHP films fabricated by existing methods are strained and that strain is caused by mismatched thermal expansion of perovskite films and substrates during the thermal annealing process. The polycrystalline films have compressive strain in the out-of-plane …

Nondestructive Testing System Design For Biological Product Based On Vibration Signal Analysis Of Acceleration Sensor, Xiaohao Li, Tao Shen

Department of Mechanical and Materials Engineering: Faculty Publications

In order to reduce the disadvantages of current biological product quality testing methods, taking the quality testing in cocoon trade markets as an example, this paper has proposed a quality nondestructive testing method for biological products based on the analysis of vibration signal from acceleration sensors. According to the wavelet transformation analysis on the random vibration signal acquired from the acceleration sensor, the random vibration signal related to the silkworm chrysalis quality has been analyzed and reconstructed; then the characteristic values such as: mean value, variance, mean square root, waveform index, pulse factor, and so on of the quality signal …

Dissipative Elastic Metamaterial With A Lowfrequency Passband, Yongquan Liu, Jianlin Yi, Zheng Li, Xianyue Su, Wenlong Li, Mehrdad Negahban

Department of Mechanical and Materials Engineering: Faculty Publications

We design and experimentally demonstrate a dissipative elastic metamaterial structure that functions as a bandpass filter with a low-frequency passband. The mechanism of dissipation in this structure is well described by a mass-spring-damper model that reveals that the imaginary part of the wavenumber is non-zero, even in the passband of dissipative metamaterials. This indicates that transmittance in this range can be low. A prototype for this viscoelastic metamaterial model is fabricated by 3D printing techniques using soft and hard acrylics as constituent materials. The transmittance of the printed metamaterial is measured and shows good agreement with theoretical predictions, demonstrating its …

Solution Nuclear Magnetic Resonance Spectroscopy On A Nanostructured Diamond Chip, P. Kehayias, A. Jarmola, N. Mosavian, I. Fescenko, F.M. Benito, A. Laraoui, J. Smits, L. Bougas, D. Budker, A. Neumann, S.R.J. Brueck, V.M. Acosta

Department of Mechanical and Materials Engineering: Faculty Publications

Sensors using nitrogen-vacancy centers in diamond are a promising tool for small-volume nuclear magnetic resonance (NMR) spectroscopy, but the limited sensitivity remains a challenge. Here we show nearly two orders of magnitude improvement in concentration sensitivity over previous nitrogen-vacancy and picoliter NMR studies. We demonstrate NMR spectroscopy of picoliter-volume solutions using a nanostructured diamond chip with dense, high-aspect-ratio nanogratings, enhancing the surface area by 15 times. The nanograting sidewalls are doped with nitrogen-vacancies located a few nanometers from the diamond surface to detect the NMR spectrum of roughly 1 pl of fluid lying within adjacent nanograting grooves. We perform 1H …

Narrowband Nanocomposite Photodetector, Jinsong Huang, Fawen Guo, Liang Shen

Department of Mechanical and Materials Engineering: Faculty Publications

A photodetector includes an anode that is transparent or partially transparent to light, a cathode and an active layer disposed between the anode and the cathode. The active layer includes a nanocomposite material that has a polymer blended with nanoparticles or organic electron trapping particles. The photodetector has a low dark current when not illuminated by light and has a high conductivity when illuminated by light, in which the light passes the anode and is absorbed by the active layer. The active layer has a thickness selected such that the photodetector has a narrowband spectral response.

Role Of Copper Oxide Layer On Pool Boiling Performance With Femtosecond Laser Processed Surfaces, Corey Kruse, Edwin Peng, Craig Zuhlke, Jeff Shield, Dennis Alexander, Sidy Ndao, George Gogos

Department of Mechanical and Materials Engineering: Faculty Publications

Copper pool boiling surfaces are tested for pool boiling enhancement due to femtosecond laser surface processing (FLSP). FLSP creates self-organized micro/nanostructures on metallic surfaces and creates highly wetting and wicking surfaces with permanent surface features. In this study two series of samples were created. The first series consists of three flat FLSP copper surfaces with varying microstructures and the second series is an open microchannel configuration with laser processing over the horizontal surfaces of the microchannels. These microchannels range in height from 125 microns to 380 microns. Each of these surfaces were tested for pool boiling performance. It was found …

Quantification Of Re-Absorption And Re-Emission Processes To Determine Photon Recycling Efficiency In Perovskite Single Crystals, Yanjun Fang, Haotong Wei, Qingfeng Dong, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Photon recycling, that is, iterative self-absorption and re-emission by the photoactive layer itself, has been speculated to contribute to the high open-circuit voltage in several types of high efficiency solar cells. For organic–inorganic halide perovskites that have yielded highly efficient photovoltaic devices, however, it remains unclear whether the photon recycling effect is significant enough to improve solar cell efficiency. Here we quantitatively evaluate the re-absorption and re-emission processes to determine photon recycling efficiency in hybrid perovskite with its single crystals by measuring the ratio of the re-emitted photons to the initially excited photons, which is realized by modulating their polarization …

Low-Drag Events In Transitional Wall-Bounded Turbulence, Richard D. Whalley, Jae Sung Park, Anubhav Kushwaha, David J.C. Dennis, Michael D. Graham, Robert J. Poole

Department of Mechanical and Materials Engineering: Faculty Publications

Intermittency of low-drag pointwise wall shear stress measurements within Newtonian turbulent channel flow at transitional Reynolds numbers (friction Reynolds numbers 70 – 130) is characterized using experiments and simulations. Conditional mean velocity profiles during low-drag events closely approach that of a recently discovered nonlinear traveling wave solution; both profiles are near the so-called maximum drag reduction profile, a general feature of turbulent flow of liquids containing polymer additives (despite the fact that all results presented are for Newtonian fluids only). Similarities between temporal intermittency in small domains and spatiotemporal intermittency in large domains is thereby found.

Atomically Informed Nonlocal Semidiscrete Variational Peierls-Nabarro Model For Planar Core Dislocations, Guisen Liu, Xi Cheng, Jian Wang, Kaiguo Chen, Yao Shen

Department of Mechanical and Materials Engineering: Faculty Publications

Prediction of Peierls stress associated with dislocation glide is of fundamental concern in understanding and designing the plasticity and mechanical properties of crystalline materials. Here, we develop a nonlocal semi-discrete variational Peierls-Nabarro (SVPN) model by incorporating the nonlocal atomic interactions into the semi-discrete variational Peierls framework. The nonlocal kernel is simplified by limiting the nonlocal atomic interaction in the nearest neighbor region, and the nonlocal coefficient is directly computed from the dislocation core structure. Our model is capable of accurately predicting the displacement profile, and the Peierls stress, of planar-extended core dislocations in face-centered cubic structures. Our model could be …

Fluid-Structure Interaction In Abdominal Aortic Aneurysm: Effect Of Modeling Techniques, Shengmao Lin, Xinwei Han, Yonghua Bi, Siyeong Ju, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

In this work, the impact of modeling techniques on predicting the mechanical behaviors of abdominal aortic aneurysm (AAA) is systematically investigated. The fluid-structure interaction (FSI) model for simultaneously capturing the transient interaction between blood flow dynamics and wall mechanics was compared with its simplified techniques, that is, computational fluid dynamics (CFD) or computational solid stress (CSS) model. Results demonstrated that CFD exhibited relatively smaller vortexes and tends to overestimate the fluid wall shear stress, compared to FSI. On the contrary, the minimal differences in wall stresses and deformation were observed between FSI and CSS models. Furthermore, it was found that …

High Temperature Near-Field Nanothermomechanical Rectification, Mahmoud Elzouka, Sidy Ndao

Department of Mechanical and Materials Engineering: Faculty Publications

Limited performance and reliability of electronic devices at extreme temperatures, intensive electromagnetic fields, and radiation found in space exploration missions (i.e., Venus & Jupiter planetary exploration, and heliophysics missions) and earth-based applications requires the development of alternative computing technologies. In the pursuit of alternative technologies, research efforts have looked into developing thermal memory and logic devices that use heat instead of electricity to perform computations. However, most of the proposed technologies operate at room or cryogenic temperatures, due to their dependence on material’s temperature-dependent properties. Here in this research, we show experimentally—for the first time—the use of near-field thermal radiation …

Surface Charge Switchable And Ph-Responsive Chitosan/Polymer Core-Shell Composite Nanoparticles For Drug Delivery Application, W. F. Huang, C. P. Tsui, M. Yang, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

The mutually conflicting surface charge requirements for nanoparticles to have long circulation and good cell affinity have made the development of polymer nanoparticles for controlled drug delivery fall into a dilemma. In order to solve this problem, the first attempt has been made in this work to develop vancomycin loaded composite nanoparticles with a novel chitosan core and poly (lactide-co-glycolide) (PLGA) shell structure and with both pH-responsive and surface charge switchable properties. Spherical composite nanoparticles have been successfully fabricated through a modified emulsion-gelation method with a controllable size (316–573 nm), surface charge (–27.6–31.75 mV) and encapsulation efficiency up to 70.8%. …

Helium Irradiation And Implantation Effects On The Structure Of Amorphous Silicon Oxycarbide, Qing Su, Shinsuke Inoue, Manabu Ishimaru, Jennifer A. Gigax, Tianyao Wang, Hepeng Ding, Michael J. Demkowicz, Lin Shao, Michael Nastasi

Department of Mechanical and Materials Engineering: Faculty Publications

Despite recent interest in amorphous ceramics for a variety of nuclear applications, many details of their structure before and after irradiation/implantation remain unknown. Here we investigated the short-range order of amorphous silicon oxycarbide (SiOC) alloys by using the atomic pair-distribution function (PDF) obtained from electron diffraction. The PDF results show that the structure of SiOC alloys are nearly unchanged after both irradiation up to 30 dpa and He implantation up to 113 at%. TEM characterization shows no sign of crystallization, He bubble or void formation, or segregation in all irradiated samples. Irradiation results in a decreased number of Si-O bonds …