Electrophysiological Sensing with Graphene Electronic Tattoos for Saline and Underwater Environments

Hazardous and unprotected underwater operations are the leading causes of diver fatalities; biosensors can offer early warning and partial protection, thereby mitigating this risk to some extent. However, the complexity and high cost of current biosensors limit their widespread adoption, emphasizing the need for effective, cost-efficient, and multifunctional physiological monitoring solutions. In this study we developed a noninvasive water-resistant graphene electrophysiological sensor capable of detecting multiple physiological signals in a saline environment, addressing the limitations of existing underwater monitoring technologies. By employing an atomically thin graphene interface and a simple coating method for waterproofing, we achieved the collection of electrocardiogram (ECG), electromyogram (EMG), and electrodermal activity (EDA) signals on the skin surface. Additionally, we demonstrate the accurate assessment of startle events via EDA signals, which could be critical for assessing diver stress and preventing accidents. The water-resistant graphene biosensor exhibited outstanding electrical properties, with impedance as low as ∼2.4 kΩ·cm 2 at 10 kHz, an EMG signal-to-noise ratio of above 21 dB, and an EDA signal response speed of up to 0.125 μS/(s·cm 2 ), all tested in saline conditions. This study provides compelling evidence for the significant potential of water-resistant graphene electrophysiological sensors in saline environments, offering a solution to enhance diver safety and reduce accident risks.