Engineering Commons^™

Integration Of Micro Nano And Bio Technologies With Layer -By -Layer Self -Assembly, Dinesh Shankar Kommireddy

Doctoral Dissertations

In the past decade, layer-by-layer (LbL) nanoassembly has been used as a tool for immobilization and surface modification of materials with applications in biology and physical sciences. Often, in such applications, LbL assembly is integrated with various techniques to form functional surface coatings and immobilized matrices. In this work, integration of LbL with microfabrication and microfluidics, and tissue engineering are explored. In an effort to integrate microfabrication with LbL nanoassembly, microchannels were fabricated using soft-lithography and the surface of these channels was used for the immobilization of materials using LbL and laminar flow patterning. Synthesis of poly(dimethyldiallyl ammonium chloride)/poly(styrene sulfonate) …

A Fe-Fd Hybrid Scheme For Solving Parabolic Two-Step Micro Heat Transport Equations In Irregularly Shaped Three Dimensional Double -Layered Thin Films Exposed To Ultrashort -Pulse Lasers, Brian R. Barron

Doctoral Dissertations

Multi-layer thin films are important components in many micro-electronic devices. These films are often used when a single film layer is insufficient to meet devices specifications. The continued reduction in component size has the side effect of increasing the thermal stress on these films and consequently the devices they comprise. Understanding the transfer of heat-energy at the micro-scale is important for thermal processing using a pulse-laser. Often, micro-voids may be found in processed devices. This is due to thermal expansion. Such defects may cause an amplification of neighboring defects resulting in severe damage and consequently the failure of the device. …

Application Of Polyelectrolyte Layer-By-Layer Nano-Assembly For Surface Modification, Encapsulation And Controlled Release, Nikhil Anil Pargaonkar

Doctoral Dissertations

In this study, we applied the traditional Electrostatic layer-by-layer (ELBL) assembly procedure to fabricate nanothin films over flat surfaces, and modify particle surfaces to influence the drug particle size, and drug release. The ELBL assembly has previously been applied to fabricate multilayer nano-scale thin films, but its ability to instantaneously influencing particle size is unique. Other unique observations such as influence on drug release as a result of polymer complexation, and thermal changes occurring during layer fabrication are recorded.

The ELBL self-assembly process was applied to produce dexamethasone particles layered with various polyelectrolyte layer combinations. These combinations were further applied …

Design And Development Of Poly -(3 -Hexylthiophene) Field Effect Transistors, Fengliang Xue

Doctoral Dissertations

Organic field effect transistors (OFETs) with poly(3-hexylthiophene) (P3HT) as the active layer are developed and studied. The device characteristics are significantly affected by source/drain contact resistance, and P3HT-SiO 2 interface and the traps. These results are verified by the numerical device simulations. The temperature dependence of device mobility is studied, which indicates that the carrier transport is either heat-assisted or heat-limited at different temperature ranges. The on/off ratio and threshold voltage are found to be dependent on the temperature. Hysteresis effect due to gate electric stress is investigated. The silanol groups present at the SiO2 surface are thought to be …

Development Of Palladium Nanowires, Chuanding Cheng

Doctoral Dissertations

Inherent limitations of traditional lithography have prompted the search for means of achieving self-assembly of nano-scale structures and networks for the next generation of electronic and photonic devices. The nanowire, the basic building block of a nanocircuit, has recently become the focus of intense research. Reports on nanowire synthesis and assembly have appeared in the scientific literature, which include Vapor-Liquid-Solid mechanism, template-based electrochemical fabrication, solvothermal or wet chemistry, and assembly by fluid alignment or microchannel networks. An ideal approach for practical application of nanowires would circumvent technical and economic constraints of templating. Here we report on the self-assembly of highly-ordered …

Study On Poly[2-Methoxy-5-(2'-Ethylhexyloxy)-1,4-Phenylenevinylene] Polymer Based Photodetectors, Difei Qi

Doctoral Dissertations

This thesis is dedicated to the development of novel and efficient polymer photodetectors based on MEH-PPV conjugated polymers. The polymer-based photodetectors have the advantages of easy processing, low weight, and low cost, and thus are promising candidates for future generations of photodetectors. At present, the quantum efficiency of polymer photodetectors is still low and not comparable to inorganic photodetectors. Therefore, in this thesis we explore ways to enhance the quantum efficiency of polymer photodetectors by using different electron donors, configurations, and implementation of the diffraction optical grating into photodetector structure. We designed, fabricated, and characterized several original types of devices: …

Modeling, Design, And Validation Of Fluorescent Spherical Enzymatic Glucose Microsensors Using Nanoengineered Polyelectrolyte Coatings, Jonathan Quincy Brown

Doctoral Dissertations

In this dissertation, the modeling, design, and function of fluorescent spherical enzymatic microsensors for minimally-invasive diabetic monitoring are described. The devices reported herein are novel and their experimental construction and theoretical analysis have not been previously reported, thus laying the foundation for an intensive set of studies. These sensors are based on the encapsulation of an enzymatic fluorescent assay for glucose within hydrogel alginate microspheres with diameters on the order of tens of microns, which are of the appropriate size for intradermal implantation. A novel feature of these sensors is the use of multifunctional nanoengineered ultrathin multilayer polyelectrolyte coatings on …

Dna-Templated Assembly Of Metallic Nanowires, Qun Gu

Doctoral Dissertations

Nanowires are widely recognized as key elements in the development of futuristic nanoscale devices of nanoelectronics, optoelectronics and nano-electro-mechanic systems. Lithographic fabrication, however, faces increasing difficulties in the realization of continuously miniaturized features. The “Bottom-up” approach is a promising successor to lithography for fabrication of nanostructures. DNA is a natural template for nanowire assembly. The linear polynucleotide chain has a width of 2 nm and a length of 0.34 run per nucleoside subunit.

One-dimensional magnetic Co and Ni nanoparticles have been assembled in-situ for the first time by use of single DNA molecules as templates. Target metallic nanowires that are …

Organization And Signal Processing Of The Descending Tracts In The Cervical Spinal Cord, Yanmei Tie

Doctoral Dissertations

This dissertation addresses the research for the development of spinal cord-computer interface (SCCI). The main objective of SCCI is to generate voluntary motor control signals for individuals with spinal cord injury (SCI).

In the neuroscience aspect, organization of the fibers in the descending tracts of the dorsolateral funiculus of the cervical spinal cord was investigated in cats. The spinal cord was penetrated with silicon substrate microelectrodes at 400 μm intervals in the medio-lateral direction at the C5/C6 and C6/C7 segmental borders. The stimulus consisted of a 20 ms train of charge-balanced biphasic pulses at 330 Hz. The evoked activities from …

Application Of Self -Assembled Ultrathin Film Coatings To Stabilize Enzyme Encapsulation And Activity In Alginate Microspheres, Rohit Srivastava

Doctoral Dissertations

Alginate-based hydrogels have been used for the encapsulation of a variety of materials, including enzymes, proteins, and cells for a wide range of applications from drug delivery to biosensors and bioreactors. However, due to the high porosity of the matrix, it has been increasingly difficult to retain macromolecules inside the alginate matrix, leading to loss in functionality over time. In an effort to improve the stability for long-term biosensor use, this work investigated layer-by-layer self-assembly as a potential technique to provide a diffusion barrier to an encapsulated macromolecule. Alginate microspheres (∼2–50μm radius) were fabricated using an emulsification technique, and were …

Biosensing With Microcantilever-Based Sensors, Xiaodong Yan

Doctoral Dissertations

Microcantilevers provide an ideal platform for biosensors. The micron-sized transducer brings several advantages, such as high sensitivity, small sample quantity for analysis, portability, implantable sensor devices, and the ability to be mass produced and integrated into standard microelectronic processing technologies like complementary metal oxide seminconductors (CMOS).

The objective of this research is to investigate and develop modification methods of microcanitlevers for biosensing applications.

Two microcantilever modification methods were investigated. They are self-assembly monolayer method and layer-by-layer method. A fundamental procedure for modification of microcantilevers using the layer-by-layer approach was developed for the first time in this research. These modification methods …

A Numerical Method For Obtaining An Optimal Temperature Distribution In A 3d Triple-Layered Cylindrical Skin Structure, Le Zhang

Doctoral Dissertations

In recent years, it has been interesting to research hyperthermia combined with radiation and cytotoxic drugs to enhance the killing of tumors. The crucial problem is that when heating the tumor tissues, one needs to keep the surrounding normal tissue below a temperature that will produce harm. Thus, it is important to obtain the temperature field of the entire treatment region. The objective of this dissertation is to develop a numerical model for obtaining an optimal temperature distribution in a 3D triple-layered cylindrical skin structure. To this end, we pre-specify the temperatures to be obtained at the center and perimeter …

Numerical Simulation Of Nanopulse Penetration Of Biological Matter Using The Z -Transform, Shengjun Su

Doctoral Dissertations

Short duration, fast rise time ultra-wide-band (UWB) electromagnetic pulses (“nanopulses”) are generated by numerous electronic devices in use today. Moreover, many novel technologies involving nanopulses are under development and expected to become widely used soon. Study of nanopulse bioeffects is needed to probe their useful range in possible biomedical and biotechnological applications, and to ensure human safety.

Based on the well-known dispersive properties of biological matter and their expression as a summation of terms corresponding to the main polarization mechanisms, the Cole-Cole expression is commonly employed to describe the frequency dependence of the dielectric properties of a tissue. Solving the …

Development Of A Novel Microreactor For Improved Chemical Reaction Conversion, Yu Liang

Doctoral Dissertations

Microreactors have been widely studied over the past two decades for different chemical reactions, to develop new analytical capabilities, and to obtain high mixing performance in the reactors. The main objectives of this work are to investigate the effect of different microchannel structures on the fluid properties and mixing behavior in microreactors, and to design, fabricate, and test a novel microreactor for higher conversion in a chemical reaction. The development of this novel microreactor is intended to provide a valuable guideline in achieving enhanced chemical mixing and to make available a solid research base for optimization of the yield of …

Microencapsulation Techniques Towards Building A Sensor: A Study Of Factors Affecting Enzyme Encapsulation And Stability, Suman R. Nayak

Doctoral Dissertations

Minimally and non-invasive glucose sensing techniques are instrumental in improving the quality of life of diabetics, point-of-care testing, critical care monitoring, development of new anti-diabetic drugs or therapeutic compounds, and the study of basic physiology. The overall goal of this project was to build a fluorescent glucose sensor by incorporating relevant sensing chemistry within microcapsules. The specific aims for this research were to study various processes used for the fabrication of micro-containers, the use of these for encapsulation purposes, and the application of the encapsulated system towards glucose sensing. The following is a brief description highlighting the key areas of …

Intelligent Control Of Nonlinear Systems With Actuator Saturation Using Neural Networks, Wenzhi Gao

Doctoral Dissertations

Common actuator nonlinearities such as saturation, deadzone, backlash, and hysteresis are unavoidable in practical industrial control systems, such as computer numerical control (CNC) machines, xy-positioning tables, robot manipulators, overhead crane mechanisms, and more. When the actuator nonlinearities exist in control systems, they may exhibit relatively large steady-state tracking error or even oscillations, cause the closed-loop system instability, and degrade the overall system performance. Proportional-derivative (PD) controller has observed limit cycles if the actuator nonlinearity is not compensated well. The problems are particularly exacerbated when the required accuracy is high, as in micropositioning devices. Due to the non-analytic nature of the …

Dilation Of The Oropharynx Via Selective Stimulation Of The Hypoglossal Nerve, Jingtao Huang

Doctoral Dissertations

Obstructive sleep apnea (OSA) is caused by the retraction of the tongue to occlude the upper airway (UAW). Electrical stimulation of the tongue protrudor and retractor muscle has been demonstrated as an effective technique to alleviate UAW obstructions and is considered to be a potential treatment for OSA. Recent studies have shown that selective stimulation of the hypoglossal nerve (HG) to activate tongue muscles using a single implantable device presents an attractive approach for treating OSA. In this study, the functional outcome of selective hypoglossal nerve stimulation with a multi-contact peripheral nerve electrode was studied by imaging the airway in …