Nastic Actuators, Elisabeth Smela, Professor, Mechanical Engineering, University of Maryland

Nastic Acuators

Propylene Carbonate as a Pumping Fluid

On this page:
Motivation | PC | Electrochemical Stability | Electrokinetic Pumping with PC | Current Work

Motivation

Under a few Volts, water splits to form hydrogen or oxygen gas.

This results in:

blocked microfluidic channels,
depleted fluid,
changes in pH (and thus zeta potential),
and low-pressure pumping (since gas is compressible).

EOF requires tens of volts, or greater.

The molecular structure of propylene carbonate (PC) is shown here, and its key properties for EOF are compared to those of water in the table. Note the high dielectric constant.

Electrochemical Stability

Deepa Sritharan, with the assistance of undergraduates Simpson Chen, Prabhath Aluthgama, and Bilal Naved, showed that without added salt, PC is stable to thousands of volts. The figure below compares electroactive steel electrodes in water and PC under 3000 V. (This is not the case for PC with salts.)

Electrokinetic Pumping with PC

Flow rates are comparable to those of water, while response speeds are a bit faster and pressures are higher.

For further information, see:

1. D. Sritharan, A. S. Chen, P. Aluthgama, B. Naved, and E. Smela, "Bubble-free electrokinetic flow with propylene carbonate," Electrophoresis (in press) (2015).

Current Work

Deepa Sritharan is now working on paper-based EOF devices, including afabrication method based on lamination.