I am confused between choosing suitable eeg electrode for my project.The active dry electrodes like g.SAHARA are costly and not easily available.How about making some DIY active electrodes?Is it appropriate to design active electrodes for a system that itself needs to be tested?
I have the usual answer: It depends!
It depends what do you want to achieve: Improvement in signal processing methods? Improvement in usability? Improvement for a particular patient? The need for hundreds of volunteers to be measured? ?? It depends!
When you only want to repeat existing experiments, you better keep, what earlier researchers stated in their papers.
When you are really in research, you are free to do what you want: In case you are developing some new "active dry electrodes", use them in comparison to standard gelled AgAgCl cups first - and then improve yours or replace theirs. I have seen some quite fancy DIY dry electrodes based on gold rod arrays - which are no worse than the commercial dry electrodes (which seem to be sensitive to noise...). We built ourselves capacitive electrodes and did get some nifty results. We now do the same with a new NIRS sensor....
No matter what the building blocks, you have to prove they are working with an existing BCI paradigm - which may lead with novel electrodes to novel signal processing algorithms to novel use case to.... I hope you get the point: Start your own path and you will see where that leads!
Conference Paper Wireless Brain Signal Recordings based on Capacitive Electrodes
Dear Rohit,
I think that for good BCI experiments you MUST use scalp cup & high density structureof recording electrodes (128 up to 256) and take a lot of care to the training procedures. Regarding reusable Ag-AgCl electrodes for EEG recordings, in my oinion is better use disposable electrodes that you can buy easily at a cheap prices in some web-shops
I have the usual answer: It depends!
It depends what do you want to achieve: Improvement in signal processing methods? Improvement in usability? Improvement for a particular patient? The need for hundreds of volunteers to be measured? ?? It depends!
When you only want to repeat existing experiments, you better keep, what earlier researchers stated in their papers.
When you are really in research, you are free to do what you want: In case you are developing some new "active dry electrodes", use them in comparison to standard gelled AgAgCl cups first - and then improve yours or replace theirs. I have seen some quite fancy DIY dry electrodes based on gold rod arrays - which are no worse than the commercial dry electrodes (which seem to be sensitive to noise...). We built ourselves capacitive electrodes and did get some nifty results. We now do the same with a new NIRS sensor....
No matter what the building blocks, you have to prove they are working with an existing BCI paradigm - which may lead with novel electrodes to novel signal processing algorithms to novel use case to.... I hope you get the point: Start your own path and you will see where that leads!
Conference Paper Wireless Brain Signal Recordings based on Capacitive Electrodes
Rohit,
It is always a question of data quality vs. ease of use. I built active electrodes for EEG and ECG earlier during my pre-doctoral research.
- If it is an effort to increase quality of the signal acquisition with dry/gelled electrodes, it would be a good investment of time in building active electrodes. Powering multiple active electrodes will increase design complexity in terms of wiring. Side-by-side comparison of active and passive electrodes can be a good option for the verification of your design.
- But, if your work is more towards conducting experiments, collecting EEG data, and use this data for BCI purposes, we want to settle on buying commercial electrodes.
All the best,
-Kunal
IMHO dry electrodes are a bit of a farce.
The are either really dry, and then these are true capacitive electrodes with all the pro's (really dry) and cons (susceptible to electric fields, i.e. noise, movement artifacts and 50/60Hz). Or they are so called dry electrodes and only start to give a reasonable signal after some time, when a layer of sweat (electrolyte) has formed between skin and electrode. And then they are not so dry anymore.
We produce plain tap water based Ag/AgCl electrodes that are popular in BCI; you can start collecting data within minutes, do not have to scratch the skin, the signals are good and the subjects do not have to wash gel out of their hair after a session (just dry). Sometimes we add a few grains of NaCl salt to improve conductivity, but usually the ions that are in the skin/hair/sweat/tap water are sufficient.
For validating self made electrodes you can use take gelled Ag/AgCl cup electrodes. They are readily available, not so expensive and give a good signal.
Lots of success,
Loek Gijben
I have used LCD screen for a application in BCIs to recognition two targets based on half-field alternate stimulation (checkerboard). In this case, two different acquisition systems were used: On the one hand, using conductive Ag/AgCl gel-based electrodes, which are popular in wired BCI systems and the other hand a wireless acquisition device (consumer device, Emotiv EPOC) with saline-based wet-contact resistive electrodes achieving good results in SSVEP.
Conference Paper Comparison between wire and wireless EEG acquisition systems...
Hello. I went to a talk recently that partially covered this topic. There is a new system for personal EEG data collection. I think it uses dry electrodes. You might be able to use this type of technology for your project. P.S. I do not work for this company, it just seemed like they had put a lot of thought into the dry electrode design.
https://emotiv.com/
brother, the biggest problem with DIY electrodes is that they suffer from polarisation.
Also, when we solder them with other materials like a copper wire, that solder contact provides some capacitance and polarisation, so its advisable to use industry made electrodes for better results.
Wearable Sensing offers several research-grade, wireless dry electrode EEG systems, motion sensor (IMU) systems, and software for neuroscience research, BCIs, consumer neuroscience, and many more applications. We would love to discuss your project with you.
www.WearableSensing.com
You can also try the Free-Cap - it´s saline based and uses a simple comfortable net of rubber strings to form a 19 Channel EEG-Cap.
https://www.neurofeedback-partner.de/product_info.php?info=p196_free-cap-4-channel-set-with-sintered-silver-silver-chloride--ag-agcl-electrodes-.html
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