Electrical & Computer Engineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2765
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Item Development of Carbon Nanotube Field-Effect Transistor Arrays for Detection of HER2 Overexpression in Breast Cancer(2011) Aschenbach, Konrad Hsu; Gomez, Romel D; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)We developed a carbon nanotube biosensor platform that was deployed at the National Cancer Institute and successfully detected the HER2 oncogene in real cancer cells at clinically relevant levels. HER2 is a receptor protein that resides on the surface of certain cancer cells and is associated with higher aggressiveness in breast cancers. Overabundance of HER2 at the chromosomal, cell surface, and intermediate gene expression levels can all indicate a dangerous HER2 status. At the present, testing for HER2 status requires labor-intensive laboratory procedures using expensive reagents. Cost remains the major barrier to widespread screening. We propose an integrated electronic testing platform based on direct label-free gene detection. The system would integrate the various labor-intensive processes that are usually performed by skilled laboratory technicians. The heart of the system is an array of carbon nanotube field-effect transistors that can detect unlabelled nucleic acids via their intrinsic electric charges. We developed a scalable fabrication technique for carbon nanotube biosensor arrays, hardware and software for data acquisition and analysis, theoretical models for detection mechanism, and protocols for immobilization of peptide nucleic acid probes and hybridization of nucleic acids extracted from cells. We demonstrated detection of HER2 from real cell lines which express cancer genes, thereby lowering the technological barrier towards commercialization of a low-cost gene expression biosensor. The system is suitable for lab-on-a-chip integration, which could bring rapid, low-cost cancer diagnoses into the clinical setting.Item Thermal and performance modeling of nanoscale mosfets, carbon nanotube devices and integrated circuits(2006-05-31) Akturk, Akin; Goldsman, Neil; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)We offer new paradigms for electronic devices and digital integrated circuits (ICs) in an effort to overcome important performance threatening problems such as self heating. To investigate chip heating, we report novel methods for predicting the thermal profiles of complex ICs at the resolution of a single device. We resolve device and IC temperatures self-consistently, with individual device performances, while accounting for IC layout and software application details. At the device level, we calculate performance and generated heat details. We then extend these performance figures to the overall chip using a stochastic or Monte Carlo type methodology. Next, at the IC level, we solve for the device temperatures using the chip's layout and application software details. Here, we apply our mixed-mode algorithm to two-dimensional (planar) and three-dimensional ICs. To relieve thermal stresses and performance degradation in specific areas of extreme heating or hot spots, we offer design strategies using thermal contacts or different IC layouts. Moreover, we also show chips that we had designed and fabricated through IC fabrication clearing house MOSIS for experimental investigations. We also investigate carbon nanotubes (CNTs) and CNT embedded MOSFETs as new device paradigms for future electronic circuits. To examine the effects of CNTs on device performance, we develop a CNT Monte Carlo simulator, and determine scattering rates and CNT electron transport. Here, we report position-dependent velocity oscillations and length effects in semiconducting single-walled zig-zag carbon nanotubes. Our calculated results indicate velocity oscillations in the Terahertz range, which approaches phonon frequencies. This may facilitate new high frequency RF device and circuit designs, opening new paradigms in communication networks. Furthermore, to obtain device performance figures for MOSFETs that embed CNTs in their channels, our device solver determines interactions between the CNT and silicon (Si) by obtaining quantization and transport effects on the tube and the Si, and at the CNT-Si barrier. We predict that the CNT-MOSFET yields a better performance than the traditional MOSFET. Especially, CNT-MOSFETs employing lower diameter tubes exhibit improved performance capabilities. We also perform similar analyses for CNT embedded SOI-MOSFETs.