Re: [DIYbio] Re: Designing a DIY Gene Electroporator

On 10/18/2013 04:01 AM, Nathan McCorkle wrote:
> What about the issue of finding uF sized caps for 1.8-2.5kV? Is there
> a way to simulate a cap's discharge? Use inductors or something?

If you mean stretch out a pulse, yes, inductance will do that, and/or
oscillate, so you have to get specific.

And yes, computer simulations are good for fine tuning power designs --
if you know what you want as a goal. MLP said she was rebooting work
on an electroporator/melaminometer the other day...

Probably, with observations from your piezo
spark generator experiments, and some more simple tests, we could skip
reverse engineering brands like Gene Pulser and such and avoid patent attacks.
There's probably no patent on basic function though, just features like
arc suppression. The high resistive DI water method seems easiest and
lowest cost parts, since it requires the least power flow. I find a newish
product uses an optional module the size of a book adding big capacitors for
long "square wave" pulses to solutions with < 1k Ohm
cuvette resistance. Square wave is a separate system to make -- put off for now.

If common practice in convenient/costly lab gear is to provide an exponential decay
from capacitor discharge of 5, 10, 25 uF, and yet, multiple pulses are just fine and OK,
why not keep costs low by using a 2 or 5 uF cap only and repeating while necessary?

One reason might be that HV makes radio interference, and it's best to make one big zap
then be quiet and say, "Who, me?" The design of this kind of thing needs
a shielding metal box to keep interference low, and when sold as a product, it needs FCC
compliance testing as an interference source. When an arc gets started, it can
generate heat and you can get a steam explosion, or just a blast of gases when in air,
so that's another reason for a solid container around the cuvette.

Leaving some of the hard parts for later, wouldn't a small capacitor fired as many times as it takes
be as good as a bigger one for the energy for a HV pulse? Does polarity matter in electroporation?
Obviously, it can't matter from the start, since orientation of bugs in a solution is random, but
after a discharge drops, what if it reverses some, giving your bugs a few wiggles of AC before dying out?
That will come naturally for a capacitor discharging into and inductive transformer to up the voltage
to 2kV.

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