Stretchable and Biocompatible Transparent Electrodes for Multimodal Biosignal Sensing from Exposed Skin

Abstract

Real-time health monitoring technology in daily life requires mechanically robust and transparent electrodes for multimodal biosignal sensing from exposed human epidermis. Here, highly stretchable transparent electrodes comprising a water-dispersed conductive polymer, poly(3,4-ethylenedioxyth iophene):poly(styrenesulfonate) (PEDOT:PSS), and a protic ionic liquid (IL), 3-methylimidazolium:bis(trifluoromethylsulfonyl)amide (p-MIM:TFSI) are reported. Owing to the high water miscibility of p-MIM:TFSI and its favorable ion exchange capability with PEDOT:PSS, PEDOT:PSS/p-MIM:TFSI transparent electrodes show enhanced electrical conductivity (σ = 450 S cm −1 ) and thin-film stretchability represented by crack onset strain (ε c ) exceeding 50%. These electrodes outperform other PEDOT:PSS electrodes processed with an aprotic counterpart, 1-ethyl-3-methylimidazolium(EMIM):TFSI, or a traditional ionic salt, Li:TFSI. The PEDOT:PSS/p-MIM:TFSI thin-film electrodes are also biocompatible and conformally adhere to human skin; therefore, multimodal biosignals including electrocardiogram, electrooculogram, and electromyogram with high signal-to-noise ratios from exposed epidermis on human faces and arms under various measurement conditions mimicking daily activities are collected. Considering the importance of light penetration through human skin for stable biological activity during biosignal monitoring, the results can broaden the applicability of daily-use wearable biosignal sensors by applying them to exposed human skin.

Recent advances in the construction and application of stretchable PEDOT smart electronic membranes

“…This electrode can be used to obtain ECG, EMG and electroencephalogram (EEG) signals on dry and moist skin surfaces, and due to its good adhesion, PWS can be used to collect electrocardiography signals from different parts of the body. Kim et al 271 described a highly stretchable transparent electrode composed of PEDOT:PSS and proton ionic liquid, 3-methylimidazole:bis(trifluoromethylsulfonyl)amide ( p -MIM:TFSI). Due to the high water solubility of p -MIM:TFSI and good ion exchangeability, the transparent electrode showed enhanced conductivity (450 S cm −1 ) and stretchability, and the crack initiation strain exceeded 50%.…”