Multi Electrophysiological Signal Collecting E-Textile System by Sponge Electrode

Wearable electrophysiological signal sensors are essential for long-term health monitoring applications, and these electrodes lead us to pre-diagnose lots of diseases such as a cardiac disorder and muscle or nerve disorders before the diseases move to more dangerous step. However, most of the reported wearable sensors have collected signals individually or integrated into patch for multi-signal collection. As a result, the practical implementation is hampered by challenges such as process complexity, durability, and user experience.<br/>Here, we introduce an interesting approach for long-term and multi-electrophysiologic signal collecting electrode by E-textile system. This system is composed of simply screen printed textile electrodes with Poly(3,4-ethylenedioxythiophene)polystyrenesulfonate (PEDOT:PSS) and carbon black mixed conductive PDMS sponge electrode. The porous structure of soft and conductive sponge electrode provides pressure sensitivity by changing the void (air gap) structure inside of the sponge. So, it shows sensitive resistance and capacitance change under small pressure changes (Under 300 Pa).<br/>For the electrophysiological signals, the sponge electrode can drastically increase the contact area between skin and electrode in water and gel condition. In addition, it also keeps the water or gel longer time compared to the planner electrode. So, to overcome the hydrophilicity of PDMS and carbon black, and maximize the absorption of water or gel into the sponge electrode, layer-by-layer (LbL) coating is utilized with poly-L-lysine.<br/>Eventually, we achieve 1.2×10⁴ Ω*cm² skin contact impedance and 30 dB signal-to-noise ratio (SNR) for the electrocardiogram (ECG) and electromyography (EMG). Furthermore, the carbon black sponge electrode demonstrates better wet condition stability compared to other coated sponge electrodes. Finally, we utilized this E-textile system for the patient study to collect uterine contraction signals and predict childbirth (Washington University Institutional Review Board, IRB 201612140). We strongly believe that this E-textile system will lead to a new opportunity for stable long-term electrophysiologic signal collecting applications.