[DIYbio] low cost electroporator (was: DIY Gene Electroporator)

On 11/03/2013 05:43 AM, Nathan McCorkle wrote:
> Are these big clunky caps really the 2013 best-fit part?

Oh, I don't know for sure. What of your guess that a few milliseconds of DC Volts are needed
to get DNA to move out of a pore? Is that anything? Do the pores close up -- how fast -- maybe
DC is unimportant?

Where is a write up of electroporation discharge where they instrumented and know the
voltage at the cuvette? The brand name I researched mentioned discharge decay curves in volts,
so I assume they did instrument theirs, but they did not mention much variety in volts, cuvette R's
energy delivered. I bet the energy delivered to a cuvette does not need to be very large.

And then there's cuvette geometry. Make a cuvette with a shorter path from side to side,
but still a usable volume and your necessary voltage just went down.
What electrode spacing do the usual suspects use? (from metal side of cuvette to other metal side.)

Before making a low cost machine, you want to know "what works", so
you can leave off features to save expense. You also figure out "what the customer wants".

From what I've read, a cap discharge is fine for high resistance solutions where the cuvette
equivalent resistance is > 1k Ohm. A special purpose machine that is no good for "square wave"
cooking of solutions with lots of salt in them with cuvette R's in the tens of Ohms can be lower cost
because it won't need as large a capacitor. The usual suspect's machine puts a selected load resistor
in parallel with the cuvette to make sure it doesn't decay too slowly and give it way more energy,
and that means about half the energy goes into the parallel load resistor, so the
caps driving ti all have to be 2X bigger. That's a feature that can be left off.

A machine with a user interface that goes through some sequences before firing off could be
programmed to measure cuvette resistance first, then balk and tell the operator "no -- I won't zap it
until you raise/lower the R of the sample."
if the cuvette R was too low or too high. Then the controller chooses a good initial voltage ,
or switches which capacitors are in the discharge circuit and asks the operator, "Zap it?".

I'm not at all interested in the DIY HV being discussed with no safety testing done,
or without thought put into safety.

I know this is about diybio, but please let's get past some of the
"quick/dirty" attitudes when discussing high voltage... and admit that when the volts go above 30 or so,
many folks just want to buy rather than make. So I'm not interested in coming up with an
instructable on how to turn a dead microwave into an electroporator. Too big a bench footprint anyway :-)

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