High-density dry EEG

High-density dry EEG pursues implant-free scalp recording with many electrodes that make electrical contact without conductive gel, using metal or coated fingers, pins, or bristles that push through hair, or soft conductive polymers. Removing gel eliminates the slow, skilled preparation and the bridging and drying that limit conventional wet caps, which is what makes wearable, self-applied, long-duration EEG plausible.

The physics exacts a price at the electrode-skin interface. Without electrolyte the contact impedance rises (often into the hundreds of kiloohms or more) and becomes unstable, so dry systems rely on high-input-impedance active electrodes buffered at the sensor and are far more sensitive to motion, triboelectric, and half-cell drift artifacts. Increasing channel count improves spatial sampling but does not overcome volume conduction: scalp EEG remains a smeared, low-spatial-frequency view of the cortex regardless of electrode number.