Dry electrodes for bio-potential measurement in wearable systems

Recent advanced technology in the field of Low power VLSI design, wireless communication and mobile based systems has shown significant scope towards the development of an alternate method of measuring biopotential signals using dry electrodes as the sensors. These electrodes can be used for long duration monitoirng of physiological signals. The conventional gel based wet Ag/AgCl electrodes are being used universally in all clinical applications for the measurement of biopotential signals like ECG, EEG, and EMG etc. The wet electrodes give excellent signal output, but they have the drawback that, they cannot be used for long duration monitoring as the gel dry out over a period of time, also the gels cause rashes and irritation to the skin when used for longer durations. The recording of ECG signals on subjects with lots of hair in the regions where electrodes are to be placed is difficult due to loss of contact between electrode and skin surface. The paper proposes a wearable physiological monitoring system that uses a novel dry electrode suitable for long duration monitoring of ECG signals. Three types of dry electrodes viz. textile electrodes, needle array electrode and a Silver coated surface electrodes were fabricated and tested for acquisition of ECG signals. The dry electrodes are fabricated as Active Electrodes thereby enabling better signal quality. The recording from the dry electrodes are compared to that of the wet electrodes and the recordings are compared and discussed.