Flexible, Air Dryable, and Fiber Modified Aerogel-Based Wet Electrode for Electrophysiological Monitoring

This study presents a novel type of wet electrode material for electrophysiological monitoring based on a conductive aerogel film. The electrode material incorporates cellulose nanocrystal and fiber as a biocompatible polymer and multi-walled carbon nanotube as a conductive filler. The fabricated electrode is fully characterized to explore the chemical, mechanical, electrical, and water absorption properties. The wet aerogel film presents suitable mechanical flexibility owing to the use of fiber enabling it to be conformal to curved surfaces like human body. The water absorption percentage of the fabricated aerogel film is extremely high (~500%) due to the porosity of the film and hydrophilicity of the base polymer allowing it for effective wet electrode applications. The film is air dryable with a fast (~10 min) and facile wetting process granting the electrode application for long-term, multiple use, and remote monitoring of patients. The electrical impedance range of the fabricated aerogel electrodes is relatively low (20 Ω/cm²-370 Ω/cm²) which is within the range of use for various electrophysiological monitoring purposes such as electrocardiography (ECG) and electroencephalography (EEG). Overall, the presented study introduces a novel wet electrode based on porous and electrically conductive aerogel film to be used for various biomedical applications.

I. Introduction

The recent advancement of electrophysiological monitoring and stimulation for next generation diagnosis and treatment procedures is highly dependent to the development of smart and adaptive materials with enhanced mechanical, electrical, and biomedical properties. The interface between monitoring and stimulation systems and human body plays a critical role in the diagnosis and treatment processes, which is carried out by means of high performance electrodes [1], [2]. In the past decades a variety of electrodes have been proposed based on advanced materials [1], [3]. The proposed electrodes have been utilized for different purposes such as biomechanical sensors [4], electrocardiography (ECG) [5], electroencephalography (EEG) [5], electromyography (EMG) [6], [7], and function electrical stimulation (FES) [8]. The use of recording and stimulating electrodes for long-term remote monitoring and treatment of patients has a potential to enable larger number of patients to have access to diagnostics and treatments with almost no barrier to using these technologies. A perfect example of such revolutionary technology are functionalized garments [8], [9]. One can essentially integrate ECG, EEG, EMG and FES functions into everyday garments such as bras, leggings, shits and socks. Since we wear these garments 24/7, the functionalized garments will result in better compliance among patient and considerable reduction in treatment and hospitalization costs while improving the patients’ comfort [10], [11]. However, there exist several challenges with respect to present day functionalized garments, where current electrode platforms may encounter issues such as (i) mechanical, electrical, and tissue compatibility with human body, (ii) stability under long-term use and operation, and (iii) reusability for long-term applications [10], [11].