A. James Clark School of Engineering

Permanent URI for this communityhttp://hdl.handle.net/1903/1654

The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

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Subject: search.filters.subject.nanowires

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Now showing 1 - 5 of 5
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    Image-Guided Precision Manipulation of Cells and Nanoparticles in Microfluidics
    (2016) Cummins, Zachary; Shapiro, Benjamin; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Manipulation of single cells and particles is important to biology and nanotechnology. Our electrokinetic (EK) tweezers manipulate objects in simple microfluidic devices using gentle fluid and electric forces under vision-based feedback control. In this dissertation, I detail a user-friendly implementation of EK tweezers that allows users to select, position, and assemble cells and nanoparticles. This EK system was used to measure attachment forces between living breast cancer cells, trap single quantum dots with 45 nm accuracy, build nanophotonic circuits, and scan optical properties of nanowires. With a novel multi-layer microfluidic device, EK was also used to guide single microspheres along complex 3D trajectories. The schemes, software, and methods developed here can be used in many settings to precisely manipulate most visible objects, assemble objects into useful structures, and improve the function of lab-on-a-chip microfluidic systems.
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    Synthesis and Characterization of Functional One Dimensional Nanostructures
    (2011) Lee, Kwan; Ouyang, Min; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    One- dimensional (1D) nanostructures have received growing interest due to their unique physical and chemical properties and promising nanodevice applications, as compared with their bulk counterparts. Complex 1D nanostructures with tunable properties and functionalities have been successfully fabricated and characterized in this thesis. I will show our recent efforts on precise controlled 1D nanostructures by template- assisted electrochemical synthesis as well as fundamental understanding of their physical behavior and growth mechanism of as-synthesized nanostructures. Particularly, three topics are presented: Firstly, a constant current (CC) based anodization technique is newly demonstrated to fabricate and control the structure of an anodic aluminum oxide (AAO) template. This technique has enabled the formation of long- range self- ordered hexagonal nanopore patterns with broad range of tunability of interpore distance (Dint). In addition, the combination of CC based anodization and conventional CV anodization can offer a fast, simple, and flexible methodology to achieve new degrees of freedom for engineering planar nanopore structures. This work also facilitates our understanding of the self- ordering mechanism of alumina membranes and complex nanoporous structure. Secondly, functional 1D nanostructures including pure metallic, magnetic and semiconducting nanowires and their heterostructure are demonstrated by versatile template- based electrochemical deposition under feasible control. This study has enabled the creation of high quality and well- controlled 1D nanostructures that can be applied as a model system for understanding unique 1D physics. Some preliminary investigations including exciton confinement, anisotropic magnetism and surface plasmon resonance are also presented. Lastly, a novel and universal non-epitaxial growth of metal-semiconductor core-shell lattice-mismatched hybrid heterostructures is presented. Importantly, a new mechanical stress driven crystalline growth mechanism is developed to account for non-epitaxial shape and monocrystalline evolution kinetics.
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    Magnetoresistive effects in planar NiFe nanoconstrictions
    (American Institute of Physics, 2004-06-01) Florez, S. H.; Dreyer, M.; Schwab, K.; Sanchez, C.; Gomez, R.D.
    This study focuses on domain wall resistance in Ni80Fe20 nanowires containing narrow constrictions down to 15 nm in width. Distinct differences in the magnetoresistance curves were found to depend on the constriction size. Wider constrictions are dominated by the overall anisotropic magnetoresistance of the structure, while constrictions narrower than ;40 nm exhibit an additional distinct contribution from a domain wall. The effect is negative and typically varies from 1% to 5%.
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    Design and packaging of an iron-gallium (Galfenol) nanowire acoustic sensor for underwater applications
    (2007-09-28) Jain, Rupal; McCluskey, F. Patrick; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A novel acoustic sensor incorporating cilia-like nanowires made of magnetostrictive iron-gallium (Galfenol) alloy has been designed and fabricated using micromachining techniques. The sensor and its package design are analogous to the structural design and the transduction process of a human-ear cochlea. The nanowires are sandwiched between a flexible membrane and a fixed membrane similar to the cilia between basilar and tectorial membranes in the cochlea. The stress induced in the nanowires due to the motion of the flexible membrane in response to acoustic waves results in a change in the magnetic flux in the nanowires. These changes in the magnetic flux are converted into electrical voltage changes by a GMR (giant magnetoresistive) sensor. As the acoustic sensor is designed for underwater applications, packaging is a key issue for the effective working of this sensor. A good package should provide a suitably protective environment to the sensor, while allowing sound waves to reach the sensing element with a minimal attenuation. In this thesis, design efforts aimed at producing this MEMS bio-inspired acoustic transducer have been detailed along with the process sequence for its fabrication. Package materials including encapsulants and filler fluids have been identified based on their acoustic performance in water by conducting several experiments to compare their impedance and attenuation characteristics and moisture absorption properties. Preliminary test results of the sensor without nanowires demonstrate the process is practical for constructing a nanowire based acoustic sensor, yielding potential benefits for SONAR applications and hearing implants.
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    Synthesis and integration of one-dimensional nanostructures for chemical gas sensing applications
    (2007-04-30) Parthangal, Prahalad Madhavan; Zachariah, Michael R; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The need for improved measurement technology for the detection and monitoring of gases has increased tremendously for maintenance of domestic and industrial health and safety, environmental surveys, national security, food-processing, medical diagnostics and various other industrial applications. Among the several varieties of gas sensors available in the market, solid-state sensors are the most popular owing to their excellent sensitivity, ruggedness, versatility and low cost. Semiconducting metal oxides such as tin oxide (SnO2), zinc oxide (ZnO), and tungsten oxide (WO3) are routinely employed as active materials in these sensors. Since their performance is directly linked to the exposed surface area of the sensing material, one-dimensional nanostructures possessing very high surface to volume ratios are attractive candidates for designing the next generation of sensors. Such nano-sensors also enable miniaturization thereby reducing power consumption. The key to achieve success in one-dimensional nanotechnologies lies in assembly. While synthesis techniques and capabilities continue to expand rapidly, progress in controlled assembly has been sluggish due to numerous technical challenges. In this doctoral thesis work, synthesis and characterization of various one-dimensional nanostructures including nanotubes of SnO2, and nanowires of WO3 and ZnO, as well as their direct integration into miniature sensor platforms called microhotplates have been demonstrated. The key highlights of this research include devising elegant strategies for growing metal oxide nanotubes using carbon nanotubes as templates, substantially reducing process temperatures to enable growth of WO3 nanowires on microhotplates, and successfully fabricating a ZnO nanowire array based sensor using a hybrid nanowire-nanoparticle assembly approach. In every process, the gas-sensing properties of one-dimensional nanostructures were observed to be far superior in comparison with thin films of the same material. Essentially, we have formulated simple processes for improving current thin film sensors as well as a means of incorporating nanostructures directly into miniature sensing devices. Apart from gas sensing applications, the approaches described in this work are suitable for designing future nanoelectronic devices such as gas-ionization, capacitive and calorimetric sensors, miniature sensor arrays for electronic nose applications, field emitters, as well as photonic devices such as nanoscale LEDs and lasers.