Ionogels and eutectogels for stable and long-term EEG and EMG signal acquisition

Abstract Neurological injuries and disorders have a significant impact on individuals’ quality of life, often resulting in motor and sensory loss. To assess motor performance and monitor neurological disorders, non-invasive techniques such as electroencephalography (EEG) and electromyography (EMG) are commonly used. Traditionally employed wet electrodes with conductive gels are limited by lengthy skin preparation time and allergic reactions. Although dry electrodes and hydrogel-based electrodes can mitigate these issues, their applicability for long-term monitoring is limited. Dry electrodes are susceptible to motion artifacts, whereas hydrogel-based electrodes face challenges related to water-induced instability. Recently, ionogels and eutectogels derived from ionic liquids and deep eutectic solvents have gained immense popularity due to their non-volatility, ionic conductivity, thermal stability, and tunability. Eutectogels, in particular, exhibit superior biocompatibility. These characteristics make them suitable alternatives for the development of safer, robust, and reliable EEG and EMG electrodes. However, research specifically focused on their application for EEG and EMG signal acquisition remains limited. This article explores the electrode requirements and material advancements in EEG and EMG sensing, with a focus on highlighting the benefits that ionogels and eutectogels offer over conventional materials. It sheds light on the current limitations of these materials and proposes areas for further improvement in this field. The potential of these gel-based materials to achieve a seamless interface for high-quality and long-term electrophysiological signal acquisition is emphasized. Leveraging the unique properties of ionogels and eutectogels holds promise for future advancements in EEG and EMG electrode materials, leading to improved monitoring systems and enhanced patient outcomes.