Dry Electrodes for Capturing Brain Electrical Signals

Almost a hundred years ago, in 1924, the first electroencephalogram - EEG, recording of brain electrical activity, was conducted by placing a metal electrode over the scalp with a conductive electrolytic gel. The electrode was connected to a signal amplifier and a signal recorder. Over the years, there has been great improvements in EEG equipments, including integrated circuits that can offer amplification, filtering and even the measurement of electrode contact impedance. However, only after the 1990s, new types of electrodes were considered to replace the traditional electrodes that requires gel, such as the dry electrodes. There are several models of dry electrodes, but they have not yet found a model that is fully accepted among clinicians. In this article we provide an overview of the current dry electrode technologies.