Design and fabrication of a multi-electrode surface for use in a DNA based biosensor

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Dawson, Guy (2020). Design and fabrication of a multi-electrode surface for use in a DNA based biosensor. University of Birmingham. Ph.D.

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Abstract

Being able to determine if a sample contains a specific protein, chemical or biological molecule has led to the development of the field of biosensors, devices that use biological components to detect their target. There are many designs of biosensors using various mechanisms and biological components, but all successful designs both detect a target in a sample, and to give a signal to the user as to the result of the test. A challenge with many biosensors is that degradation of the bio recognition component through use, age or contamination of non-target molecules can lead to reduced signals or false positives — a signal that a target is present at a concentration which is not accurate.

The ultimate purpose of this work is to aid in the design and fabrication of biosensor devices that detect specific biomarkers in sample using DNA modified with electrochemically active redox tags as a bio-recognition molecule. The work examines different methods of preparing a raised electrodes surface, that can help increase accuracy of biosensors by having simultaneous multiple methods of detection of a transducing event, and how to prepare them for deposition of these self-assembled monolayers, a precursor in depositing DNA recognition molecules. The focus of the project is in two parts, the lithography and fabrication techniques required to create the novel surfaces, and the further development of spin on hardmasks that were used elsewhere in the project. These surfaces have been designed to aid with both signal detection and reduce false positives from the breakdown of immoblised bio-recognition molecules by using a novel three-dimensional design with both surface and raised electrodes, separated by a thin dielectric. Chapters 3 focuses on the design and fabrication of the surfaces through different lithographic and fabrication techniques, challenges and solutions of both the top-down approach, including electron beam lithography and photolithography, and bottom-up approach of self-assembled monolayer deposition, which are used to pattern features in the sub 100 nanometre scale. Different surfaces were successfully fabricated and techniques proven to work for the selective cleaning and deposition of molecule onto electrodes, required for the addition of DNA to the surfaces. Sandwich electrodes were created using a spin on carbon as an electrical insulator Chapter 4 focus on the development procedure for new spin on carbons, used throughout the project, with features designed for further applications in the fabrication industry. Advancement on a new formulation of spin on carbon were achieved, including the additions of thermal acid generators to lower the required bake temperature and time, increases in film thicknesses, drain test compatibility and etching profiles.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):