On the energy conversion in electrokinetic transports.

Energy conversion in micro/nano-systems is a subject of current research, among which the electrokinetic energy conversion has attracted extensive attention. However, there exist two different definitions on the electrokinetic energy conversion efficiency in literature. A few researchers defined the efficiency using the pure pressure-driven flow rate, while other groups defined the efficiency based on the flow rate with the inclusion of the effect of the streaming potential field. In this work, both definitions are investigated for different fluid types under the periodic electrokinetic flow condition. For Newtonian fluids, the two definitions give similar results. However, for viscoelastic fluids, these two definitions lead to significant difference. The efficiency defined by the pure pressure-driven flow rate even exceeds 100% in a certain range of the parameters. The result shows that in the case of viscoelastic flow, it is incorrect to define the energy conversion efficiency by pure pressure-driven flow rate. At the same time, the reason for this problem is clarified through comprehensive analysis. [ABSTRACT FROM AUTHOR]