Fabrication Of Tunable Wettability Gold Surfaces And Their Application In Microlfuidic Analytical System

Electroless plating is a fine surface treatment technology, by means of the chemical reaction in solution. It can yield uniform deposits on the surface of both conductor and non-conductive material, and the operation is easy. In this thesis, electroless plating was employed to fabricate gold films on poly (dimethylsiloxane)(PDMS) and heat conduction glue sheets. These gold films were employed to fabricate a tunable wettability surface、 hot electrode and sampling system of microfluidic chip.The dissertation is divided into four chapters:In chapter1, recent progress in electroless plating and electroless gold plating are reviewed with respect to their fabrication methods and applications. The research progress of surfaces with special wettability is reviewed with respect to their theories and fabrication methods. The progresses of amperometric detection and sampling system in microfluidic chip are also reviewed.In chapter2, we report an approach for fabricating a tunable wettability surface by electroless gold plating on poly (dimethylsiloxane)(PDMS). A two-layer structured gold film with a tight layer and a loose layer can be obtained on the surface of PDMS chip when a PDMS chip is immersed in a gold plating solution at30℃for4h. Its wettability can be rapidly switched between superhydrophilicity and superhydrophobicity by plasma and heat temperature treatments without any self-assembled monolayer and the superhydrophobicity can be even changed from the gecko-foot-hair-like character to the lotus-leaf-like character. Benefiting from the various wettabilities of the prepared gold/PDMS composite, protein patterning is successfully achieved on a patterned superhydrophobic/superhydrophilic gold/PDMS composite; a superhydrophobic needle for transferring super-small water droplets (1μL) to a superhydrophobic surface is successfully fabricated.In chapter3, on the basis of the work in chapter2, the gold film was further deposited by electroless gold plating on the surface of L-Ⅱ heat conduction glue. A PID intelligent temperature control nano-hot-electrode array were prepared by the gold film. The hot electrode could be heated with a self-made AC heating instrument and the temperature of it could be controlled by the PID intelligent temperature control instrument. The electrode had some excellent characters:The first point is that the electrode could be placed in the end of the separation channel without the three-dimensional adjustor.The second one is that the hot electrode in the heating process can steadily reach to the required temperature without overshoot, which improves system stability and reproducibility.The third point is that the electrode preparation and application need not special equipment, and the surface of it could be renewed by polishing easily. So it is low-cost.The last one is that the integrated electrode could ensure a fixed relative position of the three-electrode system in the detection process. So the reproducibility of the detection could be improved.The electrode has been applied to PDMS microfluidic chip and showed a good analytical performance. The LODs (Limitation of Detection) of dopamine and catechol at60℃decreased an order of magnitude in comparison with the LODs at25℃. The system was applied to the detection of paeonol in traditional Chinese medicine cortex moutan with improved reproducibility and sensitivity. The test result is consistent with that obtained by the pharmacopoeia method.The last chapter combines the works of the second and third chapters. The superhydrophilic-superhydrophobic sample introduction system was prepared by electroless gold plating on PDMS and the heat-plasma treatment. The superhydrophilic regions can be used as a liquid storage tank in the capillary electrophoresis microchip. These hydrophilic regions were separated by the superhydrophobic area, so they will not be mixed with each other during the experiment. The gold film used as the anode of a capillary electrophoresis directly, which simplifies the setup. Moreover, the superhydrophilic-superhydrophobic sample introduction system can be clean and reconstructed by the full plasma surface treatment, heat treatment, the plasma treatment through mask. The sampling system and a PID intelligent temperature control hot copper electrode were integrated together in a capillary microchip. They were successfully applied to the separtion and determination histidine, tyrosine, valine, arginine mixture separation and analysis.