Hi,
I want to acquire surface EMG signals from the bicep. For the electrode design, instead of using the button electrode patch(See attached link) I want to design electrodes made of Copper.The reason for using Copper is to fabricate microelectrodes. But I am not sure if the copper electrodes are the right fit.
Any suggestions or previous experiences are helpful. Thank you.
http://www.amazon.com/3M-Multi-Purpose-Monitoring-Electrode-Foam/dp/B002C2M90I/ref=sr_1_fkmr1_1?ie=UTF8&qid=1435269039&sr=8-1-fkmr1&keywords=3m+electrodes+for+emg&pebp=1435269042161&perid=1V3RCCNNWS3HH0SN630T
Instead of the described electrode foam
you can use shampoo or shower gel, maybe
with a grain of salt. Also, you can put the
electrode into a cotton bag to be soaked
with liquid.
A problem with copper is that at the
soldering point corrosion can occur, but you
can forestall that by painting it over
(only the soldering point, of course).
Regards,
Joachim
The problem is, I cannot use any other material apart from Copper. That poses a huge challenge. I cannot even apply conductive gel to the surface.
That's why I am struggling to get a reading. But I will keep your suggestion in mind for future experiments. Thank you.
Hello Bhaskar
Of course you can use copper, as every conducting material, to record surface EMG. To my experience copper has many disadvantages for that purpose. It will fast be covered by a patina (not only at the soldering points as mentioned by Joachim). This oxide (hydroxide) is caused by contact with salt water, sweat, soldering flux, conducting gel, or other agents which react with copper. The patina alters the electrode-skin impedance in an erratic fashion and this might influence the signals intended to record. That is why most electrodes are built (or at least covered) of precious metals or stainless steel. Using the latter for special purpose electrodes was always without problems in our applications. As Joachim already mentioned a kind of conducting gel or would be needed too. Please keep in mind, that pairing copper with other conducting materials might result in a bias voltage (cause by the electro-chemical voltage) which might drive your amplifier in saturation if you use a DC amplifier.
Try to use standard material first (e.g. your mentioned electrode, or a stainless steel plate of one dime in diameter) with your recording apparatus to be sure it is the copper material problem which let your records fail. What kind of recording system, which type of recording amplifier (differential, single ended, AC) are you using? In your description the purpose or practical reason why you persist to use copper is unclear. Maybe some explanations are possible without uncovering the secret application ;-).
Microelectrodes (I guess you are talking about electrodes of sizes < 1mm) will cause additional problems, of which the dramatically reduced recording area - i.e. the distance in space within any active muscle fibers must be situated to substantially contribute to the recorded EMG Amplitude – is the most influential. In short: small electrodes monitor only few muscle fibers, and those might eventually not be representative for the activity of the whole muscle.
Regards Thomas
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