Analyzing Dry Electrodes for Wearable Bioelectrical Impedance Analyzers

Dry electrodes are gaining popularity in the area of electronic health for biosignal measurements due to their reusability and comfort as compared to traditional gel-based wet Ag/AgCl electrodes. This paper presents a performance comparison of dry and wet electrodes for medical devices, in particular, for bioelectrical impedance analysis (BIA). BIA is an emerging technology widely used for body composition analysis by computing the impedance of the human body. The designed system for BIA consists of a wearable silicone ring with four copper electrodes. The experiment is conducted on 40 healthy human subjects using both the ring and the Ag/AgCl electrodes. The linear regression demonstrates a high correlation between both electrodes (r = 0.96 for resistance and r = 0.93 for reactance). The measurement of root mean square noise is determined for both electrodes. The dry electrodes demonstrate a higher noise level (1.96 mV) as compared to the wet electrodes (0.282 mV), mainly due to the absence of conductive gel. Moreover, fast Fourier transform is performed to determine and filter out unwanted signals and to reduce the noise level in the dry electrodes. The results demonstrate that the designed ring electrodes have a comparable performance with commercial Ag/AgCl electrodes and can be used in mobile wearable medical devices.