Electrodes are made of silver/silver-chloride which has unique electrical properties. It's called a non-polarizing material that means we can instantly transfer a charge from your head to the electrode pad. Read more here on it's wiki page. To achieve this effect, a tiny chemical reaction is required, which means that these electrodes need to be replaced every couple of weeks.
We picked this electrode material because it is the best. You can use gold and other materials but Ag/AgCl is generally considered the best. Our main focus is getting the best signal from your brain into Notion's operating system. We will continuously work on improving Notion's electrodes, that is part of the reason they were made replaceable; so we can keep making them better.