Application of the Electroosmotic Effect for Thrust Generation

The present work focuses on demonstrating the capabilities of electro-osmotic pumps, EOPs, to generate thrust. EOPs have high power to volume ratio and operate on ionic aqueous solutions making them a good candidate for use as thrusters in miniature watercraft such as micro underwater gliders. Millimeter-size nano-porous membrane will be used to achieve milli-Newton thrust. Electro-osmotic pumps are operated under high electric fields to achieve highest thrust possible. A byproduct of high electric fields in EOPs is the generation of gas which is addressed by using bipolar rectangular wave pumping. This resulted in over 55% increase in flow rate when compared to DC pumping for the same average voltage while reducing gas generation. When properly sized and optimized for thrust, the feasibility of EOPs is demonstrated. This is the first experimental application of a membrane-based electro-osmotic pump for propulsion. Several membranes of different materials were tested including polymer and ceramic membranes. It was found that glass micro-capillary arrays are the most suitable membranes for electro-osmotic thrusters, or EOTs. Among their advantages include their rigid construction and ability to produce high flow rates.