Wireless noncontact ECG and EEG biopotential sensors

Abstract

Wearable, unobtrusive and patient friendly physiological sensors will be a key driving force in the wireless health revolution. Cardiac (ECG) and brain (EEG) signals are two important signal modalities indicative of healthy and diseased states of body and mind that directly benefit from long-term monitoring. Despite advancements in wireless and embedded electronics technology, however, ECG/EEG monitoring devices still face problems with patient compliance and comfort from the use wet/gel electrodes. We have developed two wireless biopotential instrumentation systems using noncontact electrodes that can operate without direct skin contact and through thin layers of fabric. The first system is a general purpose replacement for traditional ECG/EEG telemetry systems and the second is a compact, fully self-contained wireless ECG tag. All of the issues relating to the design of low noise, high performance noncontact sensors are discussed along with full technical details, circuit schematics and construction techniques. The noncontact electrode has been integrated into both a wearable ECG chest harness as well an EEG headband and characterized in a battery of experiments that represent potential health applications including resting ECG, exercise ECG and EEG directly against standard clinical adhesive Ag/AgCl electrodes. With careful design and secure mechanical harnesses the noncontact sensor is capable of approaching the quality of conventional electrodes.