Perhaps it would be worth a discussion as to the electrical settings involved as they pertain to tissue integrity in the chamber.
My assumption up until this point has been that while the electrical field strength (read, voltage drop over volume) is responsible for the electrophoretic tissue clearing, excessive current will be primarily responsible for any melting or other electrically derived destruction of tissue. Having melted several brains already, I made an attempt today to characterize the amperages involved.
It should be first stated that my chamber is of a different design than Dr. Deisseroth's team. The distance between my electrodes is 7cm, and cross sectional area is 1.425cm^2. This may (read: will) influence the ratios of electric potential drop to amperage. I should, however, experience an increase in resistance in correlation to the increased length between electrodes, and so voltage and amperage will remain directly related by the specific resistivity of solution.
In an attempt to cross check my process with that of the original, I found it necessary to calculate the specific resistivity of solution of the clearing solution. I measured (at 37C), 30V to produce 22 mAmps of current through my chamber.
Using the equation Resistance=length/area*specific resistance of solution, (R=L/A*P), I was able to calculate a specific resistance of the clearing solution to be 277.59 Ohms/cm at 37C.
In an attempt to calculate a "safe" amperage, I moved on to interpolate the amperages achieved by the original paper, using their stated materials and methods. Based on the statement that they were able to run a maximum of 4 setups at 37C and 30V on a 300mAmp-capped power supply (the same that I am using), I was assuming a current in the range of 75Amp per chamber as "safe".
Using the link posted at Clarityresourcecenter detailing ETC chamber construction, I was able to infer that the cross sectional area between Stanford's electrodes is 3.24cm^2, and distance between the electrodes is 1.3cm (the width of the 50ml blue BD bottle cap).
Using these measurements, and my previously calculated specific resistivity value at 37C, and again the formula R=L/A*P, I obtained a resistance of 111.38 Ohms for their chamber. That is to say, with an electrode width of 1.3 cm and area of 3.24cm^2, the resistance of the solution between those electrodes should be 111.38 Ohms.
At 30 volts, the amperage involved in running just one of those chambers is 270mA, already approaching the 300mA cap on the entire power supply. How is it possible to run 4 of these on a 300mA capped PSU?
One thing of interest to me; it strikes me that with constant specific resistivity of solution, and barring any changes in temperature, amperage through the chamber is an accurate measure of voltage drop across a given volume, and so should correlate with the electrophoretic driving force. (and thus clearing speed)
My question to you all is, what sort of amperages are you seeing? What sort of amperages have you been successful with? What damages the tissue? How do you achieve considerable potential drop across multiple chambers without exceeding the amperage caps of your power supplys?
It is possible that my calculation of specific resistivity of solution is off, but it seems unlikely to be wrong by more than 10% or so.