High-Sensitivity Electric Potential Sensors for Non-Contact Monitoring of Physiological Signals

TL;DR

This paper introduces highly-sensitive passive electric potential sensors capable of non-contactly detecting ECG, respiration, and EEG signals at significant distances, even through obstacles, with real-time wireless data streaming.

Contribution

The work presents an optimized EPS design with a high transimpedance amplifier and adaptive cancellation, enabling non-contact physiological monitoring in noisy environments.

Findings

ECG detectable up to 50 cm distance

EEG measurable at approximately 5 cm distance

Successful wireless real-time data streaming

Abstract

The paper describes highly-sensitive passive electric potential sensors (EPS) for non-contact detection of multiple biophysical signals, including electrocardiogram (ECG), respiration cycle (RC), and electroencephalogram (EEG). The proposed EPS uses an optimized transimpedance amplifier (TIA), a single guarded sensing electrode, and an adaptive cancellation loop (ACL) to maximize sensitivity (DC transimpedance $=150$~G$\Omega$) in the presence of power line interference (PLI) and motion artifacts. Tests were performed on healthy adult volunteers in noisy and unshielded indoor environments. Useful sensing ranges for ECG, RC, and EEG measurements, as validated against reference contact sensors, were observed to be approximately 50~cm, 100~cm, and 5~cm, respectively. ECG and RC signals were also successfully measured through wooden tables for subjects in sleep-like postures. The EPS were integrated with a wireless microcontroller to realize wireless sensor nodes capable of streaming acquired data to a remote base station in real-time.