Micropatterned non-invasive dry electrodes for brain-computer interface

Partially or completely paralyzed patients can benefit from advanced neuro-prostheses in which a continuous recording of electroencephalogram (EEG) is required, operating some processing and classification to control a computer (BCI, brain-computer interfaces). Patients are so allowed to control external devices or to communicate simple messages through the computer, just concentrating their attention on codified movements or on a letter or icon on a digital keyboard. Conventional electrodes usually require skin preparation and application of electrolytic gel for high quality low amplitude biopotentials recordings and are not suitable for being easily used by patient or caregivers at home in BCI or equivalent systems. In this report we describe the fabrication and characterization of dry (gel not required), non-invasive, user-friendly biopotential electrodes. The electrodes consist of a bidimensional array of micro-needles designed to pierce the first dielectric skin layer (stratum corneum) and establishing a direct contact with the living and electrical conducting cells in the epidermis (no blood vessels and nerve terminations). The easy and immediate application of the spiked electrodes makes them also attractive for every surface long-term biosignal measurements, even at patient's home (EEG, electrocardiogram, etc).