Stretchable Multi‐Channel Ionotronic Electrodes for In Situ Dual‐Modal Monitoring of Muscle–Vascular Activity

Abstract

In situ dual‐modal detection of electrophysiology (EP) and blood oxygen (BO) during muscle–vascular activity is crucial for healthcare and human–machine interaction. It requires an integrated monitoring system: a transparent electrode for EP detection directly adhered to skin and a near‐infrared spectroscopy (NIRs) layer for BO detection. In particular, the multi‐channel, highly transparent, stretchable electrodes should be well developed. In this study, 16‐channel transparent ionotronic electrodes are fabricated based on a stretchable and printable ionogel, demonstrating excellent properties such as high transparency, large stretchability, wet adhesion, biocompatibility, softness, and long‐term stability. The electrode exhibits stable contact impedance for 24 h and a 2‐week periodic EP monitoring. The 16‐channel transparent ionotronic electrode outperforms stretchable gold electrodes by providing stable EP monitoring with minimal interference in NIRs for blood oxygen detection. An in situ negative correlation is found between EP intensity and blood oxygen level over time. This study paves the way for designing transparent ionotronics for synchronous optical‐related monitoring and highlights the potential use of an in situ dual‐modal monitoring system for the study of muscle–vascular coupling in neurocience and rehabilitation.

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

“…In addition, the functionalization of ionogel electrodes with N-hydroxy succinimide demonstrated improved wet adhesion, leading to higher SNR in EMG signal acquisition after sweating. A similar observation was also observed when EEG monitoring was performed during sweating [11]. Ionogel-based electrodes offer a notable advantage over commercial hydrogel electrodes by not only reducing contact impedance but also improving compliance and stability for long-term electrophysiological signal acquisition.…”

“…However, the non-volatile nature of these gels makes them ideal for achieving long-term stability and continuous operation. Their inherent flexibility and conformability can enable the development of thin, lightweight, and skin-friendly sensor systems [11]. When used as electrodes for EMG or EEG sensors, these gel-based materials have the potential to provide a comfortable and unobtrusive experience for users improving patient outcomes [12].…”