Electrochemical Stability |
Electrokinetic Pumping with PC |
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.
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.)
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).
Deepa Sritharan is now working on paper-based EOF devices, including afabrication method based on lamination.