testing MEAs

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testing MEAs

Post  mat on Fri Oct 09, 2009 10:44 am

I have been given several MEAs (three 500/30iR-Ti and two 200/30-Ti) for electrophysiology studies. I tested them with the amplifier and after 30-40 seconds individual electrodes would begin to saturate with noise. (when making the scale to 500uV, the signal would be the same over the various electrodes) I would add diH2o bath and that would level them out for 3 to 5 minutes max before electrodes would begin to saturate. I ruled out any issues with the amplifier using the model test probe and wanted to do an impedance test on MEAs with simple digital multimeter.


I used a silicone ring filled with about 400ul of diH2O on
each of the electrode arrays (amplifier not involved with this) .I
used a craftsmen digital multimeter to assist with testing. On each
array, I would test three to five contact pads with both leads
touching the individual contact pad and registering zero impedance.
When I then switched one of the probes to the diH2O bath, the results
were 1 all the time for any contact pad and the bath. (on this
multimeter, a 1 usually indicates infinite impedance). I suspect my "hand me down" MEAs have been used too many
times and the TiN electrodes may have been worn out. Do my results confirm that I have bad MEAs? Do I need a special type of multimeter for TiN electrodes?

Appreciate any thoughts anyone may have.

Regards,

Mat

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Re: testing MEAs

Post  Frank MCS on Sun Oct 11, 2009 7:47 pm

Dear Mat,
any kind of measurement /recording in ddH2O is useless. To do an electrical recording, you need a condcting solution like PBS.

Regards Frank MCS
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Re: testing MEAs

Post  mat on Wed Oct 14, 2009 9:53 am

Thanks Frank for the prompt reply. I went through my trials with PBS solution with the same results. As you probably noticed, I am new to working with MEA equipment. Is there an average usage associated with an array life span? I read over a several of the posts, which indicated to keep a count on cleaning cycles. Any metrics on longevity of the arrays and cleaning I should take into account moving forward?

Mat

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MEA handling

Post  ThomasMCS on Wed Oct 14, 2009 7:19 pm

Dear Mat,

MEAs can be used upto 40 times approximatey. However it depends on many factors ike cuture time, accuracy of handing and storage etc.

You might want to have a ook in the MEA & MEA ceaning manuas to get an idea of proper MEA handing.

http://www.multichannelsystems.com/fileadmin/user_upload/Manuals/MEA-CleaningQuickGuide.pdf
http://www.multichannelsystems.com/fileadmin/user_upload/Manuals/MEA_Manual.pdf

However, a noise eve of about 500uV on al electrodes is extremey high even for an od MEA.

Please check foowing typical probems:
- Grounding: are you using internal reference or Ag/AgCl pellet? Are those properly connected?
- clean contact pads and gold spring contacts with a cotton bud with EtOh and check that springs are moving easily.
- if you are in doubt about your system, test the amplifier with the test model probe.

Greetings

Thomas

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