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Design and Fabrication of Novel Charge Biosensors Based on Electron Tunneling


Point of care diagnostics (POC) is one of the modern attempts to develop low-cost, fast, and user-friendly devices for future disease detection and early medical diagnostics. By providing quick disease diagnostics, specifically for infectious diseases, POC methods allow care givers to start early treatment leading to improved health outcomes. In this dissertation, a novel POC technology capable of detecting nucleic acid sequences using a very thin layer of oxide in a Metal-Insulator-Electrolyte junction is introduced. Micro and nanometer size devices were fabricated and tested, and high sensitivity to variations in the charge distribution at the insulator-electrolyte interface was observed. The charge variation occurs when complimentary DNA sequences in the sample solution hybridize with the single stranded DNA primers immobilized on the insulator surface. Finally, this work was coupled with voltage cycling-Polymerase Chain Reaction (vc-PCR) method. This technology allows a rapid, direct, and label-free detection of as little as a few tens of DNA molecular binding events without any need for optical measuring instruments. This work shows almost 100% change in the tunneling current when the complimentary target molecules hybridize to the immobilized primers on the surface. This technology can enable the creation of devices for cost-effective, portable and scalable real-time disease detection.

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