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Title: Physical properties and transformations of low-dimensional systems
Creator: Liu, Dan (Graduate of Michigan State University)
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Evolving from the macroscopic scale to the nanometer scale, inparticular by reducing the dimensionality, fundamental properties(such as electronic and mechanical properties) of certain systemsexhibit dramatic changes, which not only give rise to a wide rangeof emergent phenomena, but also boost technology developmentincluding nanoelectronics, optoelectronics and catalysis. In thisthesis, I utilized combined techniques including densityfunctional theory (DFT), molecular dynamic simulations (MD...
Show moreEvolving from the macroscopic scale to the nanometer scale, inparticular by reducing the dimensionality, fundamental properties(such as electronic and mechanical properties) of certain systemsexhibit dramatic changes, which not only give rise to a wide rangeof emergent phenomena, but also boost technology developmentincluding nanoelectronics, optoelectronics and catalysis. In thisthesis, I utilized combined techniques including densityfunctional theory (DFT), molecular dynamic simulations (MD),continuum elasticity approach, and the tight-binding model toconduct a systematic study on low-dimensional nanostructuresregarding their electronic and mechanical properties as well asunderlying microscopic transformation mechanisms between differentstructural allotropes.First, I briefly introduce the motivation and background of thisthesis. Then, in Chapter 2, I describe the computationaltechniques, mainly the DFT approach, on which most of my thesis isbased.In Chapters 3 and 4, I apply the continuum elasticity method tostudy the phonon spectrum of two-dimensional (2D) andone-dimensional (1D) systems. My results highlight advantages ofthe continuum elasticity approach especially for the flexuralacoustic phonon modes close to the $\Gamma$ point, which areotherwise extremely hard to converge in atomistic calculationsthat use very large supercell sizes.From Chapter 5 to Chapter 7, I focus on allotropes of groupIII, V and VI elements and study boththeir stability and microscopic transformation mechanisms from oneallotrope to another. First, I predicted a stable phosphorus coilstructure, which may form by reconstruction of red phosphorous,and which was synthesized by filling a carbon nanotube withsublimed red phosphorus. Second, I proposed two stable 2Dallotropes of Se and Te. I also suggested and evaluated apromising fabrication approach starting from natural 1D structuresof these elements. After considering low-dimensional chargeneutral systems, I changed my focus to study the effect of netcharge on the equilibrium structure. Considering a heterostructureof alternating electron donor layers an monolayers of boron, Ihave identified previously unknown stable 2D boron allotropes thatmay change their structure under different levels of chargetransfer.From Chapter 8 to Chapter 10, I focus mainly on carbon-basednanomaterials and their properties. In Chapter 8, I proposed a wayto enhance the density of states at the Fermi level in dopedC60 crystals in order to increase their superconductingcritical temperature to room temperature. In Chapter 9, I haveinvestigated a shear instability twisted bilayer graphene usingthe tight binding model. This system is susceptible to very smallstructural changes, since it becomes superconducting in a verynarrow range of twist angles near the 'magic angle'. In Chapter10, I introduced the cause of an unusual negative Poisson ratioand a shape-memory behavior in porous graphene with anartificially designed pattern.In Chapter 11, I finally present general conclusions of my PhDThesis.
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Title: Gas-phase synthesis of semiconductor nanocrystals and its applications
Creator: Rajib, Md, 1983-
Date: 2016
Collection: Electronic Theses & Dissertations
Description: Luminescent nanomaterials is a newly emerging field that provides challenges not only to fundamental research but also to innovative technology in several areas such as electronics, photonics, nanotechnology, display, lighting, biomedical engineering and environmental control. These nanomaterials come in various forms, shapes and comprises of semiconductors, metals, oxides, and inorganic and organic polymers. Most importantly, these luminescent nanomaterials can have different properties...
Show moreLuminescent nanomaterials is a newly emerging field that provides challenges not only to fundamental research but also to innovative technology in several areas such as electronics, photonics, nanotechnology, display, lighting, biomedical engineering and environmental control. These nanomaterials come in various forms, shapes and comprises of semiconductors, metals, oxides, and inorganic and organic polymers. Most importantly, these luminescent nanomaterials can have different properties owing to their size as compared to their bulk counterparts. Here we describe the use of plasmas in synthesis, modification, and deposition of semiconductor nanomaterials for luminescence applications.Nanocrystalline silicon is widely known as an efficient and tunable optical emitter and is attracting great interest for applications in several areas. To date, however, luminescent silicon nanocrystals (NCs) have been used exclusively in traditional rigid devices. For the field to advance towards new and versatile applications for nanocrystal-based devices, there is a need to investigate whether these NCs can be used in flexible and stretchable devices. We show how the optical and structural/morphological properties of plasma-synthesized silicon nanocrystals (Si NCs) change when they are deposited on stretchable substrates made of polydimethylsiloxane (PDMS). Synthesis of these NCs was performed in a nonthermal, low-pressure gas phase plasma reactor. To our knowledge, this is the first demonstration of direct deposition of NCs onto stretchable substrates.Additionally, in order to prevent oxidation and enhance the luminescence properties, a silicon nitride shell was grown around Si NCs. We have demonstrated surface nitridation of Si NCs in a single step process using non‒thermal plasma in several schemes including a novel dual-plasma synthesis/shell growth process. These coated NCs exhibit SiNx shells with composition depending on process parameters. While measurements including photoluminescence (PL), surface analysis, and defect identification indicate the shell is protective against oxidation compared to Si NCs without any shell growth.Gallium Nitride (GaN) is one of the most well-known semiconductor material and the industry standard for fabricating LEDs. The problem is that epitaxial growth of high-quality GaN requires costly substrates (e.g. sapphire), high temperatures, and long processing times. Synthesizing freestanding NCs of GaN, on the other hand, could enable these novel device morphologies, as the NCs could be incorporated into devices without the requirements imposed by epitaxial GaN growth. Synthesis of GaN NCs was performed using a fully gas-phase process. Different sizes of crystalline GaN nanoparticles were produced indicating versatility of this gas-phase process. Elemental analysis using X-ray photoelectron spectroscopy (XPS) indicated a possible nitrogen deficiency in the NCs; addition of secondary plasma for surface treatment indicates improving stoichiometric ratio and points towards a unique method for creating high-quality GaN NCs with ultimate alloying and doping for full-spectrum luminescence.
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Title: Nanorobotic end-effectors : design, fabrication, and in situ characterization
Creator: Fan, Zheng (Of Michigan State University)
Date: 2015
Collection: Electronic Theses & Dissertations
Description: Nano-robotic end-effectors have promising applications for nano-fabrication, nano-manufacturing, nano-optics, nano-medical, and nano-sensing; however, low performances of the conventional end-effectors have prevented the widespread utilization of them in various fields. There are two major difficulties in developing the end-effectors: their nano-fabrication and their advanced characterization in the nanoscale. Here we introduce six types of end-effectors: the nanotube fountain pen (NFP), the...
Show moreNano-robotic end-effectors have promising applications for nano-fabrication, nano-manufacturing, nano-optics, nano-medical, and nano-sensing; however, low performances of the conventional end-effectors have prevented the widespread utilization of them in various fields. There are two major difficulties in developing the end-effectors: their nano-fabrication and their advanced characterization in the nanoscale. Here we introduce six types of end-effectors: the nanotube fountain pen (NFP), the super-fine nanoprobe, the metal-filled carbon nanotube (m@CNT)-based sphere-on-pillar (SOP) nanoantennas, the tunneling nanosensor, and the nanowire-based memristor. The investigations on the NFP are focused on nano-fluidics and nano-fabrications. The NFP could direct write metallic "inks" and fabricating complex metal nanostructures from 0D to 3D with a position servo control, which is critically important to future large-scale, high-throughput nanodevice production. With the help of NFP, we could fabricate the end-effectors such as super-fine nanoprobe and m@CNT-based SOP nanoantennas. Those end-effectors are able to detect local flaws or characterize the electrical/mechanical properties of the nanostructure. Moreover, using electron-energy-loss-spectroscopy (EELS) technique during the operation of the SOP optical antenna opens a new basis for the application of nano-robotic end-effectors. The technique allows advanced characterization of the physical changes, such as carrier diffusion, that are directly responsible for the device's properties. As the device was coupled with characterization techniques of scanning-trasmission-electron-microscopy (STEM), the development of tunneling nanosensor advances this field of science into quantum world. Furthermore, the combined STEM-EELS technique plays an important role in our understanding of the memristive switching performance in the nanowire-based memristor. The developments of those nano-robotic end-effectors expend the study abilities in investigating the in situ nanotechnology, providing efficient ways in in situ nanostructure fabrication and the advanced characterization of the nanomaterials.
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Title: Immunosensors using metallic nanoparticle-based signal enhancement for bacterial detection and tuberculosis diagnosis
Creator: Wang, Yun
Date: 2014
Collection: Electronic Theses & Dissertations
Description: Escherichia coli O157:H7 is one of the main foodborne/waterborne bacterial pathogens that can cause human illnesses with threat to public health. To control the spread of the contaminated food/water and minimize the harm to public health, rapid and sensitive detection methods need to be implemented. However, standard culture method requires two to four days to obtain results. The application of nanomaterials has drawn interest in the biosensor research to develop timely and...
Show moreEscherichia coli O157:H7 is one of the main foodborne/waterborne bacterial pathogens that can cause human illnesses with threat to public health. To control the spread of the contaminated food/water and minimize the harm to public health, rapid and sensitive detection methods need to be implemented. However, standard culture method requires two to four days to obtain results. The application of nanomaterials has drawn interest in the biosensor research to develop timely and low cost detection systems. Because of their unique characteristics, nanoparticles have been used to enhance biosensor sensitivity by increasing the target molecule capture efficiency or by amplifying detection signals. In this dissertation research, nanoparticle-based biosensors were designed for the rapid detection of E. coli O157:H7 in broth. Magnetic nanoparticles (MNPs) were conjugated with monoclonal antibodies to separate target E. coli O157:H7 cells from samples. Gold nanoparticles (AuNPs) conjugated with polyclonal antibodies were then introduced to the MNP-target complexes to form MNP-target-AuNP. By measuring the amount of gold nanoparticles through an electrochemical method, the presence and the amount of the target bacteria were determined. Based on this biosensor using AuNPs as labels for signal amplification, a tri-nano electrochemical immunosensor was developed by using three nanoparticles for the rapid detection. The gold nanoparticles (AuNPs) were conjugated with lead sulfide (PbS) nanoparticles as electrochemical reporters via oligonucleotide linkage. AuNPs were also functionalized with polyclonal anti-E. coli O157:H7 antibodies in order to bind the target bacterial cells which were captured and separated from the sample by antibody-functionalized MNPs. Because each AuNP was linked to multiple PbS nanoparticles, each binding event to the target resulted in substantial amplification. The signal of PbS was measured on screen-printed carbon electrode (SPCE) by square wave anodic stripping voltammetry (SWASV). Results showed that the biosensor could detect E. coli O157:H7 in the range of 101 to 106 colony forming units per milliliter (cfu/ml) with a signal-to-noise ratio ranging from 2.77 to 4.31. With sample preparation being minimized, results were obtained within 1 h from sample processing to final readout. Tuberculosis (TB) is considered as one of the most widely spread infectious diseases, with estimated 8.8 million new cases and 2 million deaths annually. The biosensor developed in this dissertation research was also applied for TB diagnosis. Gold nanoparticles with anti-IFN-gamma antibody were conjugated to oligonucleotides terminated with cadmium sulfide (CdS) nanoparticles. At the same time, AuNPs were conjugated with anti-IP-10 antibody and oligonucleotides terminated with PbS nanoparticles. Therefore, the electrochemical signals of cadmium and lead indicated IFN-gamma and IP-10, respectively. By introducing MNPs with antibodies to IFN-gamma or IP-10 and AuNP conjugates, IFN-gamma and IP-10 were detected separately in buffer and simultaneously in both buffer and plasma. The results showed that IFN-gamma in the range of 0.01 IU/ml to 10 IU/ml and IP-10 in the range of 0.01 ng/ml to 100 ng/ml were detected in 1 h. Due to its rapidity, high sensitivity and multiplex detection capability, this tri-nanobiosensor has potential applications in public health, biodefense, and food/water safety monitoring.
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Title: Multiscale modeling and computation of nano-electronic transistors and transmembrane proton channels
Creator: Chen, Duan
Date: 2010
Collection: Electronic Theses & Dissertations
Description: The miniaturization of nano-scale electronic transistors, such as metal oxide semiconductor field effect transistors (MOSFETs), has given rise to a pressing demand in the new theoretical understanding and practical tactic for dealing with quantum mechanical effects in integrated circuits. In biology, proton dynamics and transport across membrane proteins are of paramount importance to the normal function of living cells. Similar physical characteristics are behind the two subjects, and model...
Show moreThe miniaturization of nano-scale electronic transistors, such as metal oxide semiconductor field effect transistors (MOSFETs), has given rise to a pressing demand in the new theoretical understanding and practical tactic for dealing with quantum mechanical effects in integrated circuits. In biology, proton dynamics and transport across membrane proteins are of paramount importance to the normal function of living cells. Similar physical characteristics are behind the two subjects, and model simulations share common mathematical interests/challenges. In this thesis work, multiscale and multiphysical models are proposed to study the mechanisms of nanotransistors and proton transport in transmembrane at the atomic level.For nano-electronic transistors, we introduce a unified two-scale energy functional to describe the electrons and the continuum electrostatic potential. This framework enables us to put microscopic and macroscopic descriptions on an equal footing at nano-scale. Additionally, this model includes layered structures and random doping effect of nano-transistors.For transmembrane proton channels, we describe proton dynamics quantum mechanically via a density functional approach while implicitly treat numerous solvent molecules as a dielectric continuum. The densities of all other ions in the solvent are assumed to obey the Boltzmann distribution. The impact of protein molecular structure and its charge polarization on the proton transport is considered in atomic details. We formulate a total free energy functional to include kinetic and potential energies of protons, as well as electrostatic energy of all other ions on an equal footing.For both nano-transistors and proton channels systems, the variational principle is employed to derive nonlinear governing equations. The Poisson-Kohn-Sham equations are derived for nano-transistors while the generalized Poisson-Boltzmann equation and Kohn-Sham equation are obtained for proton channels. Related numerical challenges in simulations are addressed: the matched interface and boundary (MIB) method, the Dirichlet-to-Neumann mapping (DNM) technique, and the Krylov subspace and preconditioner theory are introduced to improve the computational efficiency of the Poisson-type equation. The quantum transport theory is employed to solve the Kohn-Sham equation. The Gummel iteration and relaxation technique are utilized for overall self-consistent iterations.Finally, applications are considered and model validations are verified by realistic nano-transistors and transmembrane proteins. Two distinct device congurations, a double-gate MOSFET and a four-gate MOSFET, are considered in our three dimensionalnumerical simulations. For these devices, the current uctuation and voltage threshold lowering effect induced by discrete dopants are explored. For proton transport, a realistic channel protein, the Gramicidin A (GA) is used to demonstrate the performance of the proposed proton channel model and validate the efficiency of the proposed mathematical algorithms. The electrostatic characteristics of the GA channel is analyzed with a wide range of model parameters. Proton channel conductances are studied over a number of applied voltages and reference concentrations. Comparisons with experimental data are utilized to verify our model predictions.
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Title: Segmented nano-force sensor
Creator: Dharuman, Gautham
Date: 2013
Collection: Electronic Theses & Dissertations
Description: Nanoscale force sensors are finding widespread applications in atomic and biological force sensing where forces involved range from zeptonewtons to several nanonewtons. Different methods of nanoscale force sensing based on optical, electrical or purely mechanical schemes have been reported. However, each technique is limited by factors such as large size, low resolution, slow response, force range and alignment issues. In this research, a new device structure which could overcome the above...
Show moreNanoscale force sensors are finding widespread applications in atomic and biological force sensing where forces involved range from zeptonewtons to several nanonewtons. Different methods of nanoscale force sensing based on optical, electrical or purely mechanical schemes have been reported. However, each technique is limited by factors such as large size, low resolution, slow response, force range and alignment issues. In this research, a new device structure which could overcome the above mentioned constraints is studied theoretically and experimentally for the possibility of its application in nano-scale force sensing.
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Title: Structural transitions in nanoscale systems
Creator: Yoon, Mina
Date: 2004
Collection: Electronic Theses & Dissertations

Title: Equilibrium geometry and electronic properties of nanostructures
Creator: Kwon, Young-Kyun
Date: 1999
Collection: Electronic Theses & Dissertations

Title: Sensing and manipulation in a nano-bio environment using atomic force microscopy based robotic system
Creator: Li, Guangyong
Date: 2006
Collection: Electronic Theses & Dissertations

Title: In situ sensing and modeling of molecular events at the cellular level
Creator: Yang, Ruiguo
Date: 2014
Collection: Electronic Theses & Dissertations
Description: We developed the Atomic Force Microscopy (AFM) based nanorobot in combination with other nanomechanical sensors for the investigation of cell signaling pathways. The AFM nanorobotics hinge on the superior spatial resolution of AFM in imaging and extends it into the measurement of biological processes and manipulation of biological matters. A multiple input single output control system was designed and implemented to solve the issues of nanomanipulation of biological materials, feedback,...
Show moreWe developed the Atomic Force Microscopy (AFM) based nanorobot in combination with other nanomechanical sensors for the investigation of cell signaling pathways. The AFM nanorobotics hinge on the superior spatial resolution of AFM in imaging and extends it into the measurement of biological processes and manipulation of biological matters. A multiple input single output control system was designed and implemented to solve the issues of nanomanipulation of biological materials, feedback, response frequency and nonlinearity. The AFM nanorobotic system therefore provide the human-directed position, velocity and force control with high frequency feedback, and more importantly it can feed the operator with the real-time imaging of manipulation result from the fast-imaging based local scanning. The use of the system has taken the study of cellular process at the molecular scale into a new level.The cellular response to the physiological conditions can be significantly manifested in cellular mechanics. Dynamic mechanical property has been regarded as biomarkers, sometimes even regulators of the signaling and physiological processes, thus the name mechanobiology. We sought to characterize the relationship between the structural dynamics and the molecular dynamics and the role of them in the regulation of cell behavior. We used the AFM nanorobotics to investigate the mechanical properties in real-time of cells that are stimulated by different chemical species. These reagents could result in similar ion channel responses but distinctive mechanical behaviors. We applied these measurement results to establish a model that describes the cellular stimulation and the mechanical property change, a ``two-hit" model that comprises the loss of cell adhesion and the initiation of cell apoptosis. The first hit was verified by functional experiments: depletion of Calcium and nanosurgery to disrupt the cellular adhesion. The second hit was tested by a labeling of apoptotic markers that were revealed by flow cytometry. The model would then be able to decipher qualitatively the molecular dynamics infolded in the regulation of cell behavior.To decipher the signaling pathway quantitatively, we employed a nanomechanical sensor at the bottom of the cell, quartz crystal microbalance with energy dissipation monitoring (QCM-D) to monitor the change at the basal area of the cell. This would provide the real time focal adhesion information and would be used in accordance with the AFM measurement data on the top of the cell to build a more complete mechanical profile during the antibody induced signaling process. We developed a model from a systematic control perspective that considers the signaling cascade at certain stimulation as the controller and the mechanical and structural interaction of the cell as the plant. We firstly derived the plant model based on QCM-D and AFM measurement processes. A signaling pathway model was built on a grey box approach where part of the pathway map was delineated in detail while others were condensed into a single reaction. The model parameters were obtained by extracting the mechanical response from the experiment. The model refinements were conducted by testing a series of inhibition mechanisms and comparing the simulation data with the experimental data. The model was then used to predict the existences of certain reactions that are qualitatively reported in the literature.
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Title: Development of a nanoparticle-based electrochemical bio-barcode DNA biosensor for multiplexed pathogen detection on screen-printed carbon electrodes
Creator: Zhang, Deng
Date: 2011
Collection: Electronic Theses & Dissertations
Description: A highly amplified, nanoparticle-based, bio-barcoded electrochemical biosensor for the simultaneous multiplexed detection of the protective antigen A (pagA) gene (accession number = M22589) from Bacillus anthracis and the insertion element (Iel) gene (accession number = Z83734) from Salmonella Enteritidis was developed. The biosensor system is mainly composed of three nanoparticles: gold nanoparticles (AuNPs), magnetic...
Show moreA highly amplified, nanoparticle-based, bio-barcoded electrochemical biosensor for the simultaneous multiplexed detection of the protective antigen A (pagA) gene (accession number = M22589) from Bacillus anthracis and the insertion element (Iel) gene (accession number = Z83734) from Salmonella Enteritidis was developed. The biosensor system is mainly composed of three nanoparticles: gold nanoparticles (AuNPs), magnetic nanoparticles (MNPs), and nanoparticle tracers (NTs), such as lead sulfide (PbS) and cadmium sulfide (CdS). The AuNPs are coated with the first target-specific DNA probe (1pDNA), which can recognize one end of the target DNA sequence (tDNA), and many NT-terminated bio-barcode ssDNA (bDNA-NT), which act as signal reporter and amplifier. The MNPs are coated with the second target-specific DNA probe (2pDNA) that can recognize the other end of the target gene. After binding the nanoparticles with the target DNA, the following sandwich structure is formed: MNP-2pDNA/tDNA/1pDNA-AuNP-bDNA-NTs. A magnetic field is applied to separate the sandwich structure from the unreacted materials. Because the AuNPs have a large number of nanoparticle tracers per DNA probe binding event, there is substantial amplification. After the nanoparticle tracer is dissolved in 1 mol/L nitric acid, the NT ions, such as Pb2+ and Cd2+, show distinct non-overlapping stripping curves by square wave anodic stripping voltammetry (SWASV) on screen-printed carbon electrode (SPCE) chips. The oxidation potential of NT ions is unique for each nanoparticle tracer and the peak current is related to the target DNA concentration. The results show that the biosensor has good specificity, and the sensitivity of single detection of pagA gene from Bacillus anthracis using PbS NTs is as low as 0.2 pg/mL. The detection limit of this multiplex bio-barcoded DNA sensor is 50 pg/mL using PbS or CdS NTs. The nanoparticle-based bio-barcoded DNA sensor has potential applications for multiple detections of bioterrorism threat agents, co-infection, and contaminants in the same sample.
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Title: Thermoset polymer-layered silicic acid nanocomposites
Creator: Wang, Zhen
Date: 1997
Collection: Electronic Theses & Dissertations

Title: Fundamental electronic and structural properties of carbon onions in extreme environments
Creator: Al-Duhileb, Raied A.
Date: 2010
Collection: Electronic Theses & Dissertations

Title: Effects of nanoscale inclusions on the dynamics and properties of polymer melts
Creator: Tuteja, Anish
Date: 2006
Collection: Electronic Theses & Dissertations

Title: Characterization of the thermodynamics and deformation behavior of styrene-butadiene-styrene grafted with polyhedral oligomeric silsesquioxanes
Creator: Drazkowski, Daniel B.
Date: 2007
Collection: Electronic Theses & Dissertations

Title: Robust control of systems with piecewise linear hysteresis
Creator: Edardar, Mohamed Mohamed
Date: 2013
Collection: Electronic Theses & Dissertations
Description: Hysteresis nonlinearity is found in many control system applications such as piezo-actuated nanopositioners. The positioner is represented as a linear system preceded by hysteresis. This hysteresis nonlinearity is usually modeled by operators in order to simulate their effects in the closed-loop system or to use their inverse to compensate for their effects. In order to reduce the hysteresis effect, an approximate inverse operator is used as a feedforward compensator. The first part of our...
Show moreHysteresis nonlinearity is found in many control system applications such as piezo-actuated nanopositioners. The positioner is represented as a linear system preceded by hysteresis. This hysteresis nonlinearity is usually modeled by operators in order to simulate their effects in the closed-loop system or to use their inverse to compensate for their effects. In order to reduce the hysteresis effect, an approximate inverse operator is used as a feedforward compensator. The first part of our work considers driving an upper bound on the inversion error using the hysteresis model. This bound is a function of the input references, which is much less conservative than constant bounds. It is used in designing the closed-loop control systems. The second part is to design feedback controller to achieve the desired performance. Three different methods are used throughout this work and a comparison between them is also provided. First, we use the conventional proportional Integral (PI) control method, which is extensively used in commercial applications. However, in our method we add a feedforward component which improves the performance appreciably. Second, a sliding-mode-control (SMC) scheme is used because it is one of the very powerful nonlinear robust control methods. Other schemes like high gain feedback and Lyapunov redesign have close results to SMC and hence it is not included in this work. The third control is H∞ control. It is a robust linear control method, which deals with uncertainty in the system in an optimal control structure. Unlike the PI controller, the H∞ controller uses the features of the linear plant in the design which allows to accomplish more than the simple PI controller. Mainly, it can shape the closed-loop transfer function of the system to achieve the design objectives. Including the operators in the closed-loop system, makes it hard to obtain explicit solutions of the dynamics using conventional methods. We exploit two features of piezoelectric actuators to provide a complete solution of the tracking error. First, the hysteresis is approximated by a piece-wise linear operator. Second, the linear plant has a large bandwidth which allows using singular perturbation techniques to put the system in a time-scale structure. We show that the slope of a hysteresis loop segment plays an important role in determining the error size. Our analysis also shows how error is affected by increasing the frequency of the reference input. We verify that the accumulation of the error, which is propagating from segment to another is bounded and derive its limit. We provide a comparison between simulation and the analytic expressions of the tracking error at different frequencies. Experimental results are also presented to show the effectiveness of our controllers compared with other techniques.
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Title: A compact fully on-chip impedance spectroscopy system
Creator: Rairigh, Daniel J.
Date: 2007
Collection: Electronic Theses & Dissertations

Title: Mathematical modeling and simulation of mechanoelectrical transducers and nanofluidic channels
Creator: Park, Jin Kyoung
Date: 2014
Collection: Electronic Theses & Dissertations
Description: Remarkable advances in nanotechnology and computational approaches enable researchers to investigate physical and biological phenomena in an atomic or molecular scale. Smaller-scale approaches are important to study the transport of ions and/or molecules through ion channels in living organisms as well as exquisitely fabricated nanofluidic channels. Both subjects have similar physical properties and hence they have common mathematical interests and challenges in modeling and simulating the...
Show moreRemarkable advances in nanotechnology and computational approaches enable researchers to investigate physical and biological phenomena in an atomic or molecular scale. Smaller-scale approaches are important to study the transport of ions and/or molecules through ion channels in living organisms as well as exquisitely fabricated nanofluidic channels. Both subjects have similar physical properties and hence they have common mathematical interests and challenges in modeling and simulating the transport phenomena. In this work, we first propose and validate a molecular level prototype for mechanoelectrical transducer (MET) channel in mammalian hair cells.Next, we design three ionic diffusive nanofluidic channels with different types of atomic surface charge distribution, and explore the current properties of each channel. We construct the molecular level prototype which consists of a charged blocker, a realistic ion channel and its surrounding membrane. The Gramicidin A channel is employed to demonstrate the realistic channel structure, and the blocker is a positively charged atom of radius $1.5$\AA\, which is placed at the mouth region of the channel. Relocating this blocker along one direction just outside the channel mouth imitates the opening and closing behavior of the MET channel. In our atomic scale design for an ionic diffusive nanofluidic channel, the atomic surface charge distribution is easy to modify by varying quantities and signs of atomic charges which are equally placed slightly above the channel surface. Our proposed nanofluidic systems constitutes a geometrically well-defined cylindrical channel and two reservoirs of KCl solution. For both the mammalian MET channel and the ion diffusive nanofluidic channel, we employ a well-established ion channel continuum theory, Poisson-Nernst-Planck theory, for three dimensional numerical simulations. In particular, for the nano-scaled channel descriptions, the generalized PNP equations are derived by using a variational formulation and by incorporating non-electrostatic interactions. We utilize several useful mathematical algorithms, such as Dirichlet to Neumann mapping and the matched interface and boundary method, in order to validate the proposed models with charge singularities and complex geometry. Moreover, the second-order accuracy of the proposed numerical methods are confirmed with our nanofluidic system affected by a single atomic charge and eight atomic charges, and further study the channels with a unipolar charge distribution of negative ions and a bipolar charge distribution. Finally, we analyze electrostatic potential and ion conductance through each channel model under the influence of diverse physical conditions, including external applied voltage, bulk ion concentration and atomic charge. Our MET channel prototype shows an outstanding agreement with experimental observation of rat cochlear outer hair cells in terms of open probability. This result also suggests that the tip link, a connector between adjacent stereocilia, gates the MET channel. Similarly, numerical findings, such as ion selectivity, ion depletion and accumulation, and potential wells, of our proposed ion diffusive realistic nanochannels are in remarkable accordance with those from experimental measurements and numerical simulations in the literature. In addition, simulation results support the controllability of the current within a nanofluidic channel.
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Title: Advanced sensing technologies : from vanadium dioxide MEMS resonators to polypropylene ferroelectret nanogenerators
Creator: Cao, Yunqi
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "This thesis presents fundamental and applied research studies designed to enable smart material-based advanced sensing technologies including the use of vanadium dioxide (VO2) thin films in resonant frequency tuning methods, and the self-powering/energy harvesting capabilities of polypropylene ferroelectret (PPFE) polymers. The large compressive stress generated from VO2 thin films during its insulator-to-metal transition (IMT) has been investigated in recent years for thermally actuated...
Show more"This thesis presents fundamental and applied research studies designed to enable smart material-based advanced sensing technologies including the use of vanadium dioxide (VO2) thin films in resonant frequency tuning methods, and the self-powering/energy harvesting capabilities of polypropylene ferroelectret (PPFE) polymers. The large compressive stress generated from VO2 thin films during its insulator-to-metal transition (IMT) has been investigated in recent years for thermally actuated MEMS actuators. This same mechanism can be used to generate axial stress that produces large shifts in resonant frequencies. Nevertheless, taking full advantage of all benefits of this technique for tunable devices requires a fundamental understanding of the mechanisms involved and the influences of different parameters; such as structural aspect ratios, boundary conditions, buckling status, and actuation methods. In this work, VO2-based MEMS bridge and cantilever resonators were developed, and their resonant frequency shifts were characterized with respect to these parameters. It is found that residual thermal stress during the fabrication process is responsible for different buckling states in bridge structures. Bi-directional tuning for a monotonic input is observed in pre-buckled structures, which is related to bending moments and actuation methods. A ferroelectret nanogenerator is also introduced in this work as a new tuning technique to provide a programming current that allows fast switching between different resonant frequency states. This demonstrates the potential use of self-powered tuning actuation of MEMS resonators. Studies of VO2-based resonators on the power consumption and the device time constant also pave the way for integrating MEMS devices with piezoelectric energy harvesters as impact sensors.With the goal of enabling self-powered sensing technologies, a series of studies designed to understand the parameters that determine the electromechanical coupling in ferroelectret nanogenerators are presented. The electromechanical response of the active material is analyzed based on fundamental working principles of dipole moments. A lumped model is proposed, which is developed from constitutive equations and validated with experiments. The robustness of the device is verified through a series of tests including mechanical repeatability, thermal stability, and humidity resistance. The energy conversion efficiency and maximum power transfer condition are determined under periodic mechanical input, and a complete energy harvesting system with a fully integrated power management circuit is proposed for providing DC power output to effectively charge lithium-ion batteries or power small electronics."--Pages ii-iii.
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Title: Balanced improvement of high performance concrete material properties with modified graphite nanomaterials
Creator: Peyvandi, Amirpasha
Date: 2014
Collection: Electronic Theses & Dissertations
Description: Graphite nanomaterials offer distinct features for effective reinforcement of cementitious matrices in the pre-crack and post-crack ranges of behavior. Thoroughly dispersed and well-bonded nanomaterials provide for effective control of the size and propagation of defects (microcracks) in matrix, and also act as closely spaced barriers against diffusion of moisture and aggressive solutions into concrete. Modified graphite nanomaterials can play multi-faceted roles towards enhancing the...
Show moreGraphite nanomaterials offer distinct features for effective reinforcement of cementitious matrices in the pre-crack and post-crack ranges of behavior. Thoroughly dispersed and well-bonded nanomaterials provide for effective control of the size and propagation of defects (microcracks) in matrix, and also act as closely spaced barriers against diffusion of moisture and aggressive solutions into concrete. Modified graphite nanomaterials can play multi-faceted roles towards enhancing the mechanical, physical and functional attributes of concrete materials. Graphite nanoplatelets (GP) and carbon nanofibers (CNF) were chosen for use in cementitious materials. Experimental results highlighted the balanced gains in diverse engineering properties of high-performance concrete realized by introduction of graphite nanomaterials. Nuclear Magnetic Resonance (NMR) spectroscopy was used in order to gain further insight into the effects of nanomaterials on the hydration process and structure of cement hydrates. NMR exploits the magnetic properties of certain atomic nuclei, and the sensitivity of these properties to local environments to generate data which enables determination of the internal structure, reaction state, and chemical environment of molecules and bulk materials. 27Al and 29Si NMR spectroscopy techniques were employed in order to evaluate the effects of graphite nanoplatelets on the structure of cement hydrates, and their resistance to alkali-silica reaction (ASR), chloride ion diffusion, and sulfate attack. Results of 29Si NMR spectroscopy indicated that the percent condensation of C-S-H in cementitious paste was lowered in the presence of nanoplatelets at the same age. The extent of chloride diffusion was assessed indirectly by detecting Friedel's salt as a reaction product of chloride ions with aluminum-bearing cement hydrates. Graphite nanoplatelets were found to significantly reduce the concentration of Friedel's salt at different depths after various periods of exposure to chloride solutions, pointing at the benefits of nanoplatelets towards enhancement of concrete resistance to chloride ion diffusion. It was also found that the intensity of Thaumasite, a key species marking sulfate attack on cement hydrates, was lowered with the addition of graphite nanoplatelets in concrete exposed to sulfate solutions. Experimental evaluations were conducted on scaled-up production of concrete nanocomposite in precast concrete plants. Full-scale reinforced concrete pipes and beams were produced using concrete nanocomposites. Durability and structural tests indicated that the use of graphite nanoplatelets, alone or in combination with synthetic (PVA) fibers, produced significant gains in the durability characteristics, and also benefited the structural performance of precast reinforced concrete products. The material and scaled-up structural investigations conducted in the project concluded that lower-cost graphite nanomaterials (e.g., graphite nanoplatelets) offer significant potentials as multi-functional additives capable of enhancing the barrier, durability and mechanical performance of concrete materials. The benefits of graphite nanomaterials tend to be more pronounced in higher-performance concrete materials.
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