This is an Idea I had but has never been built.
There are 2 inner tubes and 2 outer tube separated by Delrin insulators/spacers.
DC or pulsed DC is applied to lower tube set and makes gas bubbles which flow up to the upper tube set. The upper tube set is then pulsed with whatever signal you want or can be another level of DC.
The output flows out of the center of the center upper tube.
