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A study on micro-patterning of polypyrrole using micro-electro-discharge machining Anwar, Mohammed Muntakim


This thesis reports micro-patterning of polypyrrole based on micro-electro-discharge machining (μEDM). The patterning feasibility is investigated using air and EDM oil as the dielectric media for the process. The discharge generation and controlled removal of the material are observed in both dielectric media; however, processing in oil is shown to be superior in achieving higher machining quality. The use of a discharge voltage of 60 V without an external capacitor as part of the relaxation-type discharge circuit is found to enable stable and precision machining with 51 nm average surface roughness and 18 mA peak discharge current. Fine micro-patterning of polypyrrole film for a depth of 7.5 μm is demonstrated using a 20-μm-diameter electrode. Machining tests with varying voltages and capacitances indicates that the use of larger capacitances at 60 V does not enhance EDM removal much unlike typical μEDM of metals, whereas the use of larger voltages with stray capacitance shows significant enhancement; a hypothesis to explain these observations is proposed. Scaling effects in machining precision and surface quality are revealed to show that the use of smaller electrodes for smaller structure patterning provides higher structural integrity and smoother and/or cleaner surfaces, an advantageous feature as a micro-machining technique for this material. The generated discharge pulses were measured to exhibit a peak current of 37 mA and a pulse frequency of 0.83 MHz on average. The dependence of electrical contact to polypyrrole samples on the discharge current is evaluated from experiments and simulations. The effects of single spark discharges on polypyrrole and stainless steel were also analyzed. Energy dispersive X-ray was used to analyze the composition of polypyrrole before and after submerging to EDM oil. The results suggested that EDM (and its oil) does not alter composition to a great extent. This study also demonstrates application of μEDM to pattern polypyrrole deposited on catheter to create electrodes. The actuation of patterned catheter was also verified. The results suggest that μEDM is a promising micro-patterning technique for polypyrrole that will promote micro-device applications for the material and encourage extensions of the study to patterning of other conducting polymers.

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Attribution-NonCommercial-NoDerivatives 4.0 International