The electrode–skin interface and optimal detection of bioelectric signals

Despite many years of research and a few review articles (McAdams et al 1996, Franks et al 2005), the problem of detecting bioelectric signals (ECG, EMG, EEG, etc) from the skin of human subjects has still not been solved in a fully satisfactory way, especially for the case of EMG where signals may be acquired during motion and with large arrays of small and close contacts, making the requirements more challenging. The classical approach involves a small metal surface (10–200 mm2) applied to the skin using conductive gel or glue as an interface (McAdams et al 1996). Capacitive electrodes, dry electrodes, and electrodes with rough surfaces, porous or covered by biolayers or tiny pins (0.2–0.4 mm long) penetrating the 'stratum corneum' are being investigated in many research laboratories (Oehler et al 2008).