Fabrication and characterization of Nafion based microactuators

Micromanipulation of microbes is one of the most important research areas in Bio-MEMS. Ionic Conductive Polymer Film (ICPF) as artificial muscles is capable of working in non-electrolyte aqueous environment and act as both an actuator and a sensor, making it more promising than other kinds of electroactive polymer (EAP) and traditional MEMS materials for underwater actuation. Hence, ICPF microactuators are very promising in the application for flexible, precise, and non-intrusive manipulation of biological entities.; This dissertation is focused on the microfabrication and characterization of Nafion based ICPF microactuators on silicon substrates.; Nafion thin film was prepared by recasting Nafion SE-5012 solution. The microstructure of the spin-coated Nafion film was similar to that of the commercial Nafion membrane in our AFM experimental result. Using MEMS-compatible process of micromachining Nafion thin film, single and multi finger Nafion actuators made of Au/Nafion/Au cantilever were successfully fabricated. The smallest cantilever fabricated was 30μm wide, 300μm long and 0.4μm thick (Nafion film was 0.2μm thick).; The actuation behaviors of the Nafion microstructures under DC and AC driven voltages were characterized. The effects of cation form, water uptake and water electrolysis that may come from the fabrication process or actuation procedure were discussed. The fundamental comparison between the actuation behavior of H+ form Nafion microactuators and K+ form microactuators was conducted by exchange H+ with K +. The electrolysis in the K+ case was lighter than the H+ case, i.e., less bubbles were generated at voltage of 2V or higher in DI water. The deflection in the K+ case was relatively smaller. This infers that the cation plays an important role in the actuation behavior. For the 100μm x 1.2mm x 0.4μm 2-finger H + Nafion gripper, full actuation could be achieved at 5∼7V DC. The K+ Nafion gripper with dimensions of 100μm x 1.5mm x 0.5μm could vibrate at 2.5V, 11Hz sine input with peak-peak deflection about 20μm. Besides, the Nafion microactuators could sense pH level change from our experimental observations.; By extending the existing linearized model to our geometric design of microactuators, the scaling effect of the ICPF actuators with respect to their actuation voltage was studied. The experimental actuation voltage was consistently one order larger than the theoretically calculated value. We suggest that the nonlinear item in the model cannot be neglected for the micro Nafion actuator with thickness in nanoscale. Finally, a proposal of fuzzy neural-network control system was proposed to control the actuation of Nafion actuators.; Novel Nafion-based microactuators on silicon substrates were developed and therefore they are potentially IC-integrable. The successful development of micro Nafion grippers will enable effective and fast control of underwater micro objects.