Here we share interesting learning experiences.
Importance of High Breakdown Voltage of Dielectric Barrier :
We realized that the perceived danger behind our project was magnified by the consistent thermal discharge that occurred during our physical experimentations.
Upon time and experience, as well as further reading and understanding, we came to recognize that thermal discharge occurred because the voltage which was reached upon producing plasma was around or beyond the breakdown voltage which our dielectric barrier possessed. It was all our dielectric barrier could withstand.
First we used PVA plastic – parts printed from the 3D printer in the M&T lab. When by reasoning out we figured that the problem was most likely the weakness of the material, we attempted to use rubber.
For the first time, following this change in material, a new light rose on our project; we were able to see cold plasma form. We knew it by its distinctive diffused and comparatively steady glow, and the lack of unpredictable bolts resembling lightning (essentially the same kind of discharge). We knew it by placing a piece of newspaper into the place where the plasma formed; upon removal, there was only a cool surface felt. (We repeated this many times just to make sure because, after so many melted and charred prototypes, we could barely believe it!) So this proved that the previous issues we’d had with safety were due to not using the right material with sufficiently high breakdown voltage. Hence, the ions were boring holes through the material, and the ferocity of the net force at which they were collectively pulled generated a lot of heat that damaged the material.
In attempting to refine our prototype design from a dielectric barrier (two parallel plates) into a needle electrode configuration, we used a rubber/silicone tube.
Then, when we found our rubber/silicone tube broke down at a notch or two above the voltage setting when plasma would form, we decided to change materials again to something even more durable than before.
So, glass was the next best candidate. Its breakdown voltage is very high, which means it would not break down at such a high voltage as is required for plasma formation. We’ve found it to be extremely reliable even at high voltages since.
Improving the Safety of Utilising the Plasma Pen:
So, we talked about this before: After we successfully made our first decent product, a cold physics expert taught us how to more safely hold a plasma pen since it contains a high voltage wire. In case the wire casing is insufficient to insulate us from high voltage, we learned that we could put our hand in our pocket and ensure no other parts of our body touches any kind of electrical ground (like a metal table, etc).
The logic behind this is that by keeping ourselves safely separated from physical contact with any electrical ground nearby, currents induced by the high voltage would not flow through the body.
Distance from ground electrode to high voltage wire:
We also found out that the distance from the ground electrode to the high voltage wire plays a part in how effective the pen is at forming plasma at a given voltage. The most efficient configuration is for the ground electrode to be covering the tip of the high voltage wire. If this is not the case, or the tip of the high voltage wire is nearer to the nozzle than the ground, then thermal discharge will likely occur.