Active flexible concentric ring electrode for non invasive surface

12 Bioelectrical surface recordings are usually performed by unipolar or bipolar disc electrodes even 13 though they entail the serious disadvantage of having poor spatial resolution. Concentric ring electrodes 14 give improved spatial resolution, although this type of electrode has so far only been implemented in 15 rigid substrates and as they are not adapted to the curvature of the recording surface may provide 16 discomfort to the patient. Moreover, the signals recorded by these electrodes are usually lower in 17 amplitude than conventional disc electrodes. The aim of this work was thus to develop and test a new 18 modular active sensor made up of concentric ring electrodes printed on a flexible substrate by thick-film 19 technology together with a reusable battery-powered signal-conditioning circuit. Simultaneous ECG 20 recording with both flexible and rigid concentric ring electrodes were carried out on 10 healthy 21 volunteers at rest and in motion. The results show that flexible concentric ring electrodes not only 22 present lower skin-electrode contact impedance and lower baseline wander than rigid electrodes but are 23 also less sensitive to interference and motion artefacts. We believe these electrodes, which allow 24 bioelectric signals to be acquired non-invasively with better spatial resolution than conventional disk 25 electrodes, to be a step forward in the development of new monitoring systems based on Laplacian 26 potential recordings. 27