Preparation Of Microelectrodes Using Microfabrication Technique And Their Applications

Due to the high space resolution and stability of microelectrode, it has became as a powerful tool for micro scale measurements and been applied in the field of life science, environmental science, and high-technology. The conventional fabrication method of microelectrode is based on the pulling of capillary, which has poor reproducibility and difficult in making multi-sensor. The microfabrication technology, having excellent reproducibility, good stability and good accuracy, can be used as a tool for microelectrode fabrication. The reported pH microelectrodes usually contained glass capillary and metal nano-wire pH microelectrdes. In their practical applications, their measurement usually has some errors, and their miniaturization and portability are limited. In this thesis, a new needle-type integrated microelectrode (IME) with an integration of pH microelectrode, count microelectrode, and Ag/AgCl reference microelectrode was fabricated using negative photoresist SU8, UV photolithography technology, ion beam deposition technology, ion beam etching technology, and electrochemical deposition. A simple, efficient and reliable method for fabricating IME was proposed. The electrochemical properties and anti-interference ability of IME were characterized. The results show that IME has a high electrochemical activity and a good stability. IME is applicable as an electrochemical analytic tool.Nanoelectrode have unique electrochemical properties such as fast response rate, high current density, high signal-to-noise ration, small capacitive-charging currents, reduced i·R drop, and steady-state diffusion currents. These properties enable their use in the in-vivo measurement of dopamine (DA). A variety of methodologies for manufacturing nano-electrodes have been developed in the past two decades, but it is hard to precisely and repeatly fabricate nanoelectrodes, and the active area of nanoelectrode is unable to be renewed. In this thesis, we have developed a novel approach to precisely manufacture nano-Au-electrode (NAuE) using lithographic fabrication technology, and characterize the NAuE for DA detection. The cross surface morphology and thickness of the Au layer were imaged by scanning electron microscopy and an interference microscopy. This NAuE could be precisely and repeatedly fabricated, and conveniently renewed for several times. The electrochemical sensitivity and selectivity of the NAuE towards DA detection were significantly higher than those of a standard Au thin-film electrode. The results demonstrate that the NAuE could be used as an attractive means for electrochemically sensing and recording DA.Nano array electrode (NAE) offers the properties of high detection sensitivity, good stability, rapid response rate, and good detection selectivity. These characterizations make it be a powerful biosensor. Currently, there are many different methodologies for manufacturing nano-wire structures, but their efficiencies are lower. In this thesis, a new method with an integration of vacuum sputtering-deposition technology, holography lithography technology, and argon ion-beam etching technology, has been proposed to fabricate NAE for glucose detection. This approach is established based on the control of the miniature thickness of photoresist, optimization selection of the exposure time and exposure dose in the holography lithography process and developing time. The NAE could be precisely prepared with a miniature size of 78 nm and a large active sensor area of 60 mm X60 mm. NAEs were used to detect glucose and showed a high electrochemical activity and anti-interference ability.Because of limited space, the number of integrated single nanoelectrodes is usually limited, and a lot of time and cost are needed for the detection. In this thesis, a new type of addressable nano-array electrode has been fabricated using microfabrication technologies. In such a device, the colomn and row electrodes were arranged orthogonally to fabricate a 10×10 array of measurement points with only 20 bonding pads for external connetction. The crossing points of the colomn and row electrodes were used as detection elements, which could easily be resolved by connecting and setting the potential at the colomn and row electrodes.In the preparation process of nanomaterials, the production of undesirable byproducts and caused many other problems such as coalescence and agglomeration of nanomaterials in post-synthesis annealing are unavoidable. In addition, the composition, morphology, and properties of the obtained nanomaterials depend largely on the precursor manipulation and the reaction conditions. In this thesis, an easily controlled method, through integrating the holographic lithography technology, argon ion-beam lithography technology and electrochemical codeposition technology, was proposed to prepare the catalytically efficient gold nanowire substrate for the electrochemical deposition of Pt in conjunction with Fe2O3 nanomaterials, in order to reduce the use of noble Pt. Cyclic voltammetry was exploited to deposit the Pt-Fe2O3 nanomaterials on the nano-wire substrate. The prepared Pt-Fe2O3 modified nano-electrode array was then used for methyl orange degradation, and its excellent electrochemical catalytic activity for methyl orange degradation was demonstrated under neutral conditions.