Integrated Circuits and Electrode Interfaces for Noninvasive Physiological Monitoring

Abstract

This paper presents an overview of the fundamentals and state of the-art in noninvasive physiological monitoring instrumentation with a focus on electrode and optrode interfaces to the body, and micropower-integrated circuit design for unobtrusive wearable applications. Since the electrode/optrode-body interface is a performance limiting factor in noninvasive monitoring systems, practical interface configurations are offered for biopotential acquisition, electrode-tissue impedance measurement, and optical biosignal sensing. A systematic approach to instrumentation amplifier (IA) design using CMOS transistors operating in weak inversion is shown to offer high energy and noise efficiency. Practical methodologies to obviate 1/f noise, counteract electrode offset drift, improve common-mode rejection ratio, and obtain subhertz high-pass cutoff are illustrated with a survey of the state-of-the-art IAs. Furthermore, fundamental principles and state-of-the-art technologies for electrode-tissue impedance measurement, photoplethysmography, functional near-infrared spectroscopy, and signal coding and quantization are reviewed, with additional guidelines for overall power management including wireless transmission. Examples are presented of practical dry-contact and noncontact cardiac, respiratory, muscle and brain monitoring systems, and their clinical applications.

Real-time neuroimaging and cognitive monitoring using wearable dry EEG

“…In recent years, advances in dry-electrode electroencephalography (EEG) and wireless integrated acquisition systems [1, 2] have spurred increasing development of a new generation of wearable, mobile applications of EEG for real-world cognitive state monitoring, clinical diagnostics and therapeutics, and brain-computer interfaces (BCI), among others [3–7]. Concomitant with this is an increasing scientific appreciation for the importance of measuring complex dynamic interactions (e.g.…”

“…In [1], a first version of a 64-channel dry EEG system was introduced, focusing on the physical properties of the dry electrode, and briefly highlighting the wearable headset and compact electronics. Here we present an extended version with a detailed description of the complete headset system, including operational mechanics to minimize motion artifacts; system specifications and electronics, including analog frontend and shielding for obtaining high quality signals from dry electrodes; and a wireless communications system, necessary for transmitting accurate time-marked data in a wireless environment.…”

Signal modes for design-oriented analysis of active sEMG spatial filter electrodes

“…Moreover, dry electrodes are preferred in many applications because they enable comfortable and faster installation, according to the "wearable" paradigm [8].…”

Cell-culture measurements using voltage oscillations

“…Nowadays, many Lab-on-a-Chips (LoCs) and implanted devices for biomedical applications are based on sensing the impedance of a biological sample as one of the main biomarkers [3,7,8,9,11,15]. Among Impedance Spectroscopy (IS) techniques, Electrical Cell-substrate Impedance Spectroscopy (ECIS) was described [4,5] as an useful alternative for Cell Culture (CC) assays, allowing real-time monitoring, and greatly reducing the cost and human effort in assays.…”