Weak Molecular Interactions in Organic Composite Dry Film Lead to Degradable, Robust Wireless Electrophysiological Signal Sensing

Abstract

Long‐term and highly sensitive electrophysiological signal detection is the primary issue for wearable health monitoring. The critical issues of pre‐gelled wet electrodes as conventional approaches are limited conductivity and low adhesivity owing to the dependence of moisture concentration. Along this line, this paper presents a biocompatible, mechanically robust, water degradable, and intrinsically conductive organic composite dry film electrode based on poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), hydroxyethyl cellulose, and dopamine. The effects on PEDOT:PSS structure transition are studied systematically according to the combination of each component with various analytical methods including morphological, chemical, electrical, and mechanical characterization. The proposed film exhibits high conductivity (292 S m–1) and robust mechano‐electrical stability (only 8% of resistance change under 110 of fully flat‐bended cycles) owing to the weak but synergetic interactions between the components. Furthermore, low noise, clear signal, and long‐term stability for a wireless electrocardiogram and electromyogram signal sensing is achieved using the proposed dry electrode.

A moldable PEDOT:PSS dry electrode with excellent epidermal compliance for wearable electrocardiogram monitoring

“…These tunable interfacial mechanical properties have not been reported in previous work on PEDOT:PSS based dry electrodes. Compared with previous work on PEDOT:PSS based dry electrodes, such as e-tattoo, 1,2 textiles 3–5 and elastomeric polymer blended PEDOT:PSS6-8, this PSG aerogel dry electrode shows lower contact impedance to obtain high quality ECG signals because of the excellent interfacial compliance (Fig. S8 and Table S3, ESI†).…”

“…3 Silver/silver chloride (Ag/AgCl) gel electrodes are dominant in clinical practice, but they are prone to signal attenuation during prolonged monitoring induced by the evaporation of liquid in the gel electrolyte, as well as skin irritation. 4 Therefore, extensive efforts have been devoted to the development of skin-friendly dry electrodes for long-term wearable ECG measurements. Dry electrodes in the literature can be mainly divided into contact dry electrodes and non-contact dry capacitive electrodes.…”

Bioelectronic Applications of Intrinsically Conductive Polymers

“…Although the wet electrodes can have good compliance with the skin, they are not suitable for long-term biopotential monitoring because of the skin irritation they cause and dehydration over time. [49] Instead, dry electrodes with compliant contact to skin can be used for long-term monitoring. [50][51][52] There are mainly three types of dry electrodes, that is, flexible patch electrodes, [53] textile electrodes, [54] and thin film e-tattoo electrodes.…”

“…reported self-adhesive dry electrodes consisting of PEDOT:PSS, polydopamine, and hydroxyethyl cellulose (Figure 3d). [49] In addition, good permeability is also required for long-term use. Zhang et al deposited PPy on permeable soft leather via in situ polymerization.…”

“…d) Dry electrodes using a composite of PEDOT:PSS, polydopamine, and hydroxyethyl cellulose. Reproduced with permission [49]. Copyright 2022, john wiley and sons.…”