[Open_electroporator] electroporator testing (again)

[John Griessen]

On 03/13/2018 01:21 AM, Justin Atkin wrote:
> Hi Nathan,
> 
> So just to confirm, the device doesn't deliver an exponential decay pulse and uses something closer to a square wave?  Is there a 
> way to control the voltage? Or just the pulse width/period?


Both can be controlled, but not accurately without a little testing.  This machine creates short pulses usually 20 microseconds 
and less, so the delivered pulse is a composite of many short ones and the load resistance matters also.  Seeing the results is 
needed to adjust overall pulse shape.  Salty, (mammalian cells in buffer), suspensions will probably be more conductive than the
machine design has power to drive unless the volume of suspension is less than 100 microliters.
So, the best way is to write a script for an exponential decay pulse tested on a resistor first.  Observe, then adjust the
shape to desired, then call it ready to use.

To clarify -- all the circuit elements and topology used to create the pulses have linear superposition
properties, so the pulse shape can be scaled without seeing or testing first, and get good results.  If
we come up with a parameterized exponential decay pulse script, any peak voltage can be generated with it
without calibrating the shape of every one.

In other words the script can have a scale factor, and changing that one number will make an
exactly proportional smaller or larger pulse of the same shape if used on the same load resistance.
The peak voltage to avoid the machine breaking is around 3000V, so when above 2500V is observed, start scaling things
down or your recipe will kill the machine.  The main way to observe is using the machine's built in ADC converter,
which might not be very accurate in v 0.5, so 2500V is a good maximum to use.

If the cuvette/sample/probe load is non-linear in some way -- such as being in a container at the end of along wet of wires
with substantial inductance, linear results would no longer hold.

Using this machine for in vivo electroporation could kill the subject or operator, or both, depending on the setup details --
you know -- arm to arm shocks and all...