Monday, August 22, 2016

No bubble?



Experimental procedures often have lots of superstitions.
Even in electrophysiological techniques there are plenty of those.
Superstitions often make one comfortable while doing stressful experiments; however, it looks silly when you see someone following a superstition that you don't believe in.

Here's an example: the bubbles in a glass capillary microelectrode.
I know some people seriously worry about those bubbles. They let the electrode sit in a tube filled with 3M KCl solution for a few minutes. It looks as if some sort of Buddhist ceremony with an insence standing up in front of an altar.

I don't believe that religion and here's why.
Here is a microelectrodes with ugly bubbles.


I let the silver wire not to penetrate through these bubbles.
And the resistance was...


The voltage drop was -38mV with no bridge when -1nA was passed. 
So the electrode resistance was 38 MΩ.


Then, I let the bubble go out. 
Yes it took me a few minutes to get rid of all tiny bubbles.


And the resistance was...


It was reduced by 1 MΩ. 
So, those ugly stupid bubbles costed me 1 MΩ!

MΩ, Oh well...
Tell you what, when you play with 6 electrodes simultaneously poking around neurons looking for Si2 or Si3 or whatever cells, 1 MΩ drift is nothing.  The electrode resistance will change anyway by tens of MΩ when you poke around the brain looking for cells. It is no worth spending a good few minutes just to get rid of those stupid 1 MΩ bubbles. Just go for a poke with it and replace it when clogged. Think about the efficiency of your labor. Don't worry about the bubbles. 

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