Novel Hybrid Sensors for Unobtrusive Recording of Human Biopotentials

Practical sensing of biopotentials such as EEG or ECG in operational settings has been severely limited by the need for skin preparation and conductive electrolytes at the skin-sensor interface. Another seldom-noted problem has been the need for a conductive connection from the body to ground for cancellation of common-mode noise voltages. At QUASAR, we have developed a novel hybrid (capacitive/conductive) sensor that requires no skin preparation or electrolytes. In addition we have developed a special common-mode follower that allows a dry electrode to be used for the ground. The electronics for the sensors and common-mode follower have low power requirements and are miniaturized to fit within a compact sensor case. We are extending our tests of the hybrid sensor in three human-machine interaction contexts: 1) a real-time system of multimodal physiological gauges for improved human-automation reliability, 2) EEG-based cognitive-overload detection in an urban combat simulation, and 3) a brain-computer interface for EEG-based communication in the severely disabled. In all three contexts we compared the QUASAR hybrid sensors with traditional conductive electrodes for EEG or ECG recordings. We discuss the recording fidelity, noise characteristics, ease of use, and reliability of the hybrid sensors versus the conventional conductive electrodes in all contexts.