More low voltage EO
Continuation of the work with the Borkholder group (see this post).
We put together a couple of videos of EO flow in the streaming potential cell today. Runs were performed using Ag/AgCl painted wires at ~2.5 V. Lower voltages weren’t producing very convincing flow rates.
Here’s the best video of pumping we obtained:
The polarity of the electrodes is changed every 10s. Each mark is 0.5 mm. I’ve plotted the volumetric flow rate and applied voltage as a function of time. The flow rate calculation is performed by from the change in position times the cross sectional area for each time point, and there’s some error in the position measurement. At any rate, you can see that the direction of the EO flow changes with the changing voltage.
We noticed that the flow rate usually started out quickly and then slowed down over time. This is a little visible in the above graph for the second time the voltage is positive. It is even more noticeable in the following movie, in which the voltage polarity switched every 25s.
I’m not sure why this is happening. I don’t expect the back pressure to be building over the time of pumping or that viscous effects are increasing. Perhaps this is due to using up the ions in the chambers, although I’m surprised that this would happen in the relatively large device.