Fabricate Gold And Enzymatic Micropatterns

In chapter one, a new method for gold deposition by SECM was developed. Gold was chemically deposited on a silicon substrate by this means. A silicon substrate was mounted in a cell, then put the electrolyte consisted of KAu(CN)₂ KF and NaNO₂ into the cell. And the carbon fiber microelectrode tip was moved down toward the substrate. The principle of fabricating microstructures was based on the local generation of protons at the tip to induce the surface reaction of gold deposition on the substrate in the vicinity of the tip. The protons induced the redox reaction between Au(CN)₂^- and silicon which were generated at the tip by oxidizing nitrite ions from the solution. Si was oxidized to SiF₆^2-, meanwhile, the Au(CN)₂^- in the solution was metallized by taking the electrons released from Si. The different parameters that controlled the gold deposition, such as the pH, the concentrations of the KAu(CN)₂,KF and NaNO₂. Using the method, gold arrays and line were fabricated and characterized by SECM generator-collector mode.In chapter two, SECM "microreagent" mode was used to fabricate horseradish peroxidase (HRP) micropatterns. The HRP substrate was modified by using the SECM tip that electrogenerated OH^- ions to react with the substrate surface. The reaction of BQ, O₂ and H₂O at a microelectrode tip generated OH^- ions which deactivated the localized enzyme molecules at the substrate. In the mode, the biotinylated HRP was immobilized on a polystyrene plate via a streptavidin bridge. Then the enzyme-immobilized substrate was immersed into a BQ, KC1 solution (pH 8.0). A three-electrode configuration consisting of a carbon fiber microelectrode of 7 μm diameter, a Pt wire auxiliary electrode and an Ag/AgCl reference electrode was used for microfabrication. We placed the microelectrode tip over the HRP-immobilized substrate with a distance of ² μm and applied a potential of -1.7 V vs. Ag/AgCl to the tip to deactive the localized enzyme molecules nearby. After the deactivation, the catalytic activity of the HRP substrate fabricated was determined using the SECM feedback mode. For this purpose, 2.00×10^-3mol/L H₂O₂ was added to the solution, and the tip potential was changed to -0.2 V vs. Ag/AgCl to monitor the reduction current of BQ. Recycling of tip-generated H₂Q to BQ occurred between the SECM tip and the active HRP surface, causing an increase in tip current because of positive feedback redox cycling. However, above the deactivated HRP, tip-generated H₂Q could not be oxidized to BQ, diffusion of BQ to the tip was hindered and the tip current decreased because of negative feedback. As the tip was moved on the substrate at a constant height, the current depended on the HRP activity. Therefore, the resulting patterns of HRP, including deactivated lines, arrays, and the active linear HRP pattern were fabricated and characterized. We also used "Surface Patterned Conditioning" technique to design a deactivated "H" letter.In chapter three, a new method for fabricate horseradish peroxidase (HRP) patterns was developed. First, the biotinylated HRP was immobilized on a polystyrene plate via a streptavidin bridge. In the solution of BQ, KC1 (pH 8.0), we placed the "stamper" electrode onto the HRP-immobilized substrate. A Pt wire auxiliary electrode and an Ag/AgCl reference electrode was immersed into the solution. And applied a potential of -1.7 V vs. Ag/AgCl to the "stamper" electrode. The reaction of BQ, O₂ and H₂O at the "stamper" electrode generated OH" ions which deactivated the localized enzyme molecules at the substrate. Using the method, deactivated lines, arrays, and the deactivated "十" letter were fabricated. The patterns were characterized by SECM. The width of the deactivated lines is about 40 μm, and three times the diameter of the "stamper" electrode. The reaction is slower was proved by this means, the character of control product diffusion was determined with the form of the electrode. It is suit for industrialized production because of the simple apparatus and convenient operation.In chapter four, a new method for gold deposition by microchannel was developed. Gold was chemically deposited on a silicon substrate. We obtained the gold patterns which figure the same to the microchannel. We put the PDMS model onto a silicon substrate, then made the mixed solution (pH 6.0) of KAu(CN)₂ and KF flow in the microchannel. The protons induced the redox reaction between Au(CN)₂^-and silicon. Si was oxidized to SiF₆^2- meanwhile, the Au(CN)₂^- in the solution was metallized by taking the electrons released from Si. Using the method, a lot of patterns may be fabricated. The patterns were characterized by microscope and camera. The coalescent between the deposited gold and silicon substrate is very hard. Simple apparatus and convenient operation are strongpoint of the experiment. It is a good method for fabricate micropattems. Finally, we got the active biologic patterns through putting the GO_X onto gold.