UBC Theses and Dissertations
Feasibility of miniature polypyrrole actuated valves Cole, Matthew
Polypyrrole is a conducting polymer that can change in volume as its oxidation state is altered. This change in volume, operable at low voltages, can be used to create small actuating devices. The goal of this thesis is to evaluate the use of polypyrrole for the creation of a low voltage polymer valve and to demonstrate the mechanisms that could be used to create these valves. There are a number of challenges in using polypyrrole in a commercially viable valve; it must be able to withstand large temperature variations, have a high strain (to minimize mechanical amplification), have high work density (to minimize the amount of polypyrrole required), have a long lifetime and be assemblable into a compact valve. To evaluate and meet these requirements: 1) The effect of modifying synthesis and actuation conditions on the electrochemical actuation of polypyrrole is investigated to find the conditions that give the highest electrochemical strain and strongest polypyrrole films. Stable and fast strains of 6% at up to 2 MPa for films grown in propylene carbonate and actuated in NaPF6(aq) are achieved. These films were stored for up to 3 months before use with no losses in strain but showed a loss of 0.06% of their maximum strain per electrochemical cycle. 2) Polypyrrole is exposed to temperature variations, showing that high temperature (up to 80°C) exposure has a deleterious effect on polypyrrole actuation. To try and minimize losses, the effect of temperature in both aqueous and organic electrolytes and the mechanism for degradation is investigated. -PF6 grown films in aqueous electrolytes show the least degradation. 3) A linear valve mechanism is built and demonstrates that it should be possible to achieve the force and displacement required to open and close a sliding plate valve. Empirical models suggest that it should be possible to use polypyrrole sliding oil sealed valves. 4) An encapsulatable trilayer is built that seals holes in a perforated plate and could also be used to make a valve.
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