Inkjet printed flexible electrodes for surface electromyography

Recording of surface ElctroMyoGraphic (sEMG) signal represents a challenge, due to the nature both stochastic and deterministic of the biopotential. The sEMG signal results from the superimposed activity of a high number of motor units, artifacts, and background noise. Among the different non-invasive techniques to measure the muscle electrical activity, recent studies showed how High-Density surface EMG (HD-sEMG) constitutes a very effective tool. HD-sEMG uses multiple closely spaced electrodes overlying a restricted area of the skin and provides high definition temporal and spatial information on muscle activity. To optimize the features of the current devices for HD-sEMG signal detection, this paper reports on the realization of the first inkjet printed HD electrode matrix. The matrix was built by inkjet printing of a commercial silver-based ink on a flexible Kapton® substrate. While bringing about all advantages of drop-on-demand inkjet technology, such as rapid prototyping and simple CAD re-desing of customizable devices, the printed matrix produces interesting electrical results in terms of resolution, resistance and electrode–skin contact impedance. Electrode–skin impedance obtained with our measurement setup was indeed always in line, while not better than the one obtained with commercial electrodes.