Matching Items (3)
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- All Subjects: Frequency Selective Surfaces
- All Subjects: High permittivity dielectric pads
- All Subjects: Protein Nanotechnology
- Creators: Jones, Anne
- Creators: Chakraborty, Partha
- Creators: Sisk, Ryan Derek
Description
The honors thesis presented in this document describes an extension to an electrical engineering capstone project whose scope is to develop the receiver electronics for an RF interrogator. The RF interrogator functions by detecting the change in resonant frequency of (i.e, frequency of maximum backscatter from) a target resulting from an environmental input. The general idea of this honors project was to design three frequency selective surfaces that would act as surrogate backscattering or reflecting targets that each contains a distinct frequency response. Using 3-D electromagnetic simulation software, three surrogate targets exhibiting bandpass frequency responses at distinct frequencies were designed and presented in this thesis.
ContributorsSisk, Ryan Derek (Author) / Aberle, James (Thesis director) / Chakraborty, Partha (Committee member) / Electrical Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
The ability of magnetic resonance imaging (MRI) to image any part of the human body without the effects of harmful radiation such as in CAT and PET scans established MRI as a clinical mainstay for a variety of different ailments and maladies. Short wavelengths accompany the high frequencies present in high-field MRI, and are on the same scale as the human body at a static magnetic field strength of 3 T (128 MHz). As a result of these shorter wavelengths, standing wave effects are produced in the MR bore where the patient is located. These standing waves generate bright and dark spots in the resulting MR image, which correspond to irregular regions of high and low clarity. Coil loading is also an inevitable byproduct of subject positioning inside the bore, which decreases the signal that the region of interest (ROI) receives for the same input power. Several remedies have been proposed in the literature to remedy the standing wave effect, including the placement of high permittivity dielectric pads (HPDPs) near the ROI. Despite the success of HPDPs at smoothing out image brightness, these pads are traditionally bulky and take up a large spatial volume inside the already small MR bore. In recent years, artificial periodic structures known as metamaterials have been designed to exhibit specific electromagnetic effects when placed inside the bore. Although typically thinner than HPDPs, many metamaterials in the literature are rigid and cannot conform to the shape of the patient, and some are still too bulky for practical use in clinical settings. The well-known antenna engineering concept of fractalization, or the introduction of self-similar patterns, may be introduced to the metamaterial to display a specific resonance curve as well as increase the metamaterial’s intrinsic capacitance. Proposed in this paper is a flexible fractal-inspired metamaterial for application in 3 T MR head imaging. To demonstrate the advantages of this flexibility, two different metamaterial configurations are compared to determine which produces a higher localized signal-to-noise ratio (SNR) and average signal measured in the image: in the first configuration, the metamaterial is kept rigid underneath a human head phantom to represent metamaterials in the literature (single-sided placement); and in the second, the metamaterial is wrapped around the phantom to utilize its flexibility (double-sided placement). The double-sided metamaterial setup was found to produce an increase in normalized SNR of over 5% increase in five of six chosen ROIs when compared to no metamaterial use and showed a 10.14% increase in the total average signal compared to the single-sided configuration.
ContributorsSokol, Samantha (Author) / Sohn, Sung-Min (Thesis director) / Allee, David (Committee member) / Jones, Anne (Committee member) / Barrett, The Honors College (Contributor) / Electrical Engineering Program (Contributor)
Created2022-05
Description
In recent years, researchers have employed DNA and protein nanotechnology to develop nanomaterials for applications in the fields of regenerative medicine, gene therapeutic, and materials science. In the current state of research, developing a biomimetic approach to fabricate an extracellular matrix (ECM)-like material has faced key challenges. The difficulty arises due to achieving spatiotemporal complexity that rivals the native ECM. Attempts to replicate the ECM using hydrogels have been limited in their ability to recapitulate its structural and functional properties. Moreover, the biological activities of the ECM, such as cell adhesion, proliferation, and differentiation, are mediated by ECM proteins and their interactions with cells, making it difficult to reproduce these activities in vitro.Thus, the work presented in my dissertation represents efforts to develop DNA and protein-based materials that mimic the biological properties of the ECM. The research involves the design, synthesis, and characterization of nanomaterials that exhibit unique physical, chemical, and mechanical properties. Two specific aspects of the biomimetic system have been to include (1) a modular protein building block to change the bioactivity of the system and (2) to temporally control the self-assembly of the protein nanofiber using different coiled coil mechanisms. The protein nanofibers were characterized using atomic force microscopy, transmission electron microscopy, and super-resolution DNA Point Accumulation for Imaging in Nanoscale Topology. The domains chosen are the fibronectin domains, Fn-III10, Fn-III9-10, and Fn-III12-14, with bioactivity such as cell adhesion and growth factor binding.
To extend this approach, these cys-nanofibers have been embedded in a hyaluronic acid scaffold to enable bioactivity and fibrous morphologies. Nanofiber integration within the HA gel has been shown to promote tunable mechanical properties and architectures, in addition to promoting a temporal display of the protein nanofibers. The hydrogels were characterized using scanning electron microscopy, mechanical compression testing, and fluorescence microscopy. The findings in this dissertation highlight the promise of biomimetic DNA and protein nanomaterials as a versatile approach for developing next-generation materials with unprecedented properties and functions. These findings continue to push the boundaries of what is possible in nanotechnology, leading to new discoveries that will have a significant impact on society.
ContributorsBernal-Chanchavac, Julio (Author) / Stephanopoulos, Nicholas (Thesis advisor) / Jones, Anne (Committee member) / Mills, Jeremy (Committee member) / Arizona State University (Publisher)
Created2023