Is DIY As Good As Clinical/Commercial When It Comes To tDCS Electrodes?
An important component of tDCS and one that might be overlooked by DIYers is the electrode. Folks looking to explore brain stimulation using a few electrical components and a nine volt battery, might forego the $25 — $40 cost of a couple 2 inch Amrex electrodes in favor of something they could piece together from stuff lying around. Is that crazy?
This is a good time to pause and make it clear that we are not necessarily endorsing the non-clinical use of brain stimulation. We ARE trying to further the discourse and apply clinical and scientific rigor as best we can. To that end, understand that tDCS and other brain stimulation done outside of clinical supervision is at your own risk.
Please explore our blog and the interwebs at large for more information about tDCS.
Can you make an electrode that works as well as one used clinically?
The bottom line is: YES.
To test this question, we assembled three cellulose-sponge based electrodes and measured them against a 2 x 2" Amrex electrode. In the future we may test additional DIY configurations.
tDCS generally applies low amperage/low voltage direct current to carefully mapped locations on the head. While some stimulation and measurement techniques require smaller more focused contact with the subjects skin (think EEG), the electrodes for tDCS provide a localized charge over a larger area.
We use the same concepts used to make our DIY electrodes as is used for the Amrex electrode. . .
The electrode consists of an 8mm thick sponge backed by a steel mesh, all of which is held together inside a rubber sleeve. The tDCS device is connected to the mesh which disperses the current across the sponge.
Our version employs a similar sponge purchased at the grocery store and cut to size and various types of metal mesh. They are held together with either safety pins or sewn on with embroidery yarn.
Let’s get to the testing. . .
An electrode should deliver the expected amperage evenly across the surface. It should make good uniform contact with the subject without gaps and lumps. This can result in a bad session or even burns to the skin.
The key value in this test is amperage or current. We used a DIY tDCS device that operates from a 9 volt battery, delivering 7.5 volts in set to an amperage of 2.0mA. We created a rig to test the same areas within the field of the electrodes. We tested these 5 points then rotated the electrode 180 degrees and tested again to get a total of 9 points within the field. We also tested the field of the electrode in its entirety using a metal plate.
The Amrex electrode is the standard we hope to meet. The specs say these are 2 inch square however the effective size is closer to 1 3/8 inch square due to the rubber sleeve.
Our DIY electrodes were 3 versions of the same thing. Sponges with 3 different types of mesh: stainless steel, heavier gauge aluminum, and finer aluminum.
We also tested a 1 5/8 inch sticky silicone electrode used for TENs units for fun.
Quick note on electrodes and saline. There doesn’t seem to be clear agreement on the ideal salinity for soaking these sponges. Look for a future blog on the topic. The important thing for this test is that all the sponges used the exact same water.
We used a headband (NBA) to hold the electrodes to the rig to simulate how you might use. This headband did not cover the entire electrode which had some effect on the results.
“D” was located on the outside corner of a 2 inch square field. The Amrex and some of the homemade electrodes where not large enough to reach that spot. Additionally, the sponges that did reach that spot didn’t have the headband pressing down on them. This is the reason for the odd or missing readings for that spot. “C” was in between two relatively close testing spots. This combined with inconsistent pressure from the headband resulted in the strange readings for “C”. When we manually added a bit more pressure to the site, the measurements were 2mA.
- The DIY sponge electrodes measure similarly to the Amrex electrodes.
- The DIY versions allow for custom sizes and shapes (imagine a 1.5 inch circle)
- The DIY electrodes may be a bit more challenging for people with longer hair. The edges of the mesh can snag hair.
- 😊If you are bald and don’t mind the stickiness, you might consider the TENs electrodes