Skin‐Like Transparent Sensor Sheet for Remote Healthcare Using Electroencephalography and Photoplethysmography

Abstract The growing demand for efficient home healthcare applications for brain disorder diagnostics and treatment has inspired the development of wearable devices for monitoring brain activity. However, flexible probes that have improved biocompatibility for wearable devices are markedly affected by noise due to contact interface issues. In this study, a stretchable (≤1500% strain) and transparent (over 85% transmittance) biocompatible electrode that steadily adheres to skin is developed to fabricate an imperceptible sheet‐type device that wirelessly records electroencephalograms (EEGs). The multifunctional characteristic of the electrode results from the double‐network structure in an elastomer/conductive additive blend on a metal‐nanowire‐based track, which contributed to EEG monitoring with ultralow noise (≈0.14 µV noise floor) and sleep‐stage classification. Furthermore, the optical transparency enabled camera‐based photoplethysmography to detect pulse waves and blood oxygen saturation without interfering with the light path, which is a crucial factor in realizing a remote healthcare system.