Bernard Grundlehner

• M. Sc. EE
• System Architect Wearable EEG at Imec the Netherlands

This paper describes accurate monitoring of hydration using impedance variation in a human being, which accompanies extracellular fluid loss or gain. A prototype of a precision multifrequency bioimpedance meter built around advanced biomedical SoC (System on Chip) MUSEIC v.2 was used in this study. Calibration of the bioimpedance board was conducte...

The bioimpedance sensor recently developed at Imec was calibrated on the equivalent RC model of human body and tested on the volunteer undergoing repeated mild dehydration and rehydration. Some sources of variability in hydration assessment are observed that were not spotted and reported before. The specific protocols developed in this study enable...

Nightingale V2, a new wearable multi-sensor platform, is introduced in this paper. It can measure various bio-signals including ECG, BioZ, PPG, motion and heart sounds simultaneously at very low power consumption. Patient safety with optical and electrical sensors were carefully investigated. Preliminary data collection results as well as the senso...

Ambulatory electroencephalography (EEG) monitoring is an active field, targeting a wide range of applications such as critical monitoring in the neuro intensive care unit, first-aid assistance, early diagnosis of neurodegenerative diseases, rehabilitation after stroke, neurofeedback, and augmented and virtual reality. Capturing the delicate EEG wav...

By bringing the ability to track physiological signals over long periods of time, wearable sensing has the potential to enable new paradigms in disease prevention, treatment and management, in and beyond healthcare. Such paradigms could range from chronic monitoring to observe and detect gradual shifts in relevant parameters to the discovery of rar...

Monitoring cognitive engagement during daily activities can offer new insights in understanding our brain at work. It requires the usage of a convenient electroencephalograph (EEG) system and an adequate model that can characterize cognitive states and state changes reflected in the electrical activity of the brain. This paper studies EEG during co...

Conventional gel electrodes are widely used for biopotential measurements, despite important drawbacks such as skin irritation, long set-up time and uncomfortable removal. Recently introduced dry electrodes with rigid metal pins overcome most of these problems; however, their rigidity causes discomfort and pain. This paper presents dry electrodes o...

Designing and developing a comfortable and convenient EEG system for daily usage that can provide reliable and robust EEG signal, encompasses a number of challenges. Among them, the most ambitious is the reduction of artifacts due to body movements. This paper studies the effect of head movement artifacts on the EEG signal and on the dry electrode-...

Monitoring human brain activity has great potential in helping us understand the functioning of our brain, as well as in preventing mental disorders and cognitive decline and improve our quality of life. Non-invasive surface EEG is the dominant modality for studying brain dynamics and performance in real-life interaction of humans with their enviro...

Conventional gel electrodes are widely used for biopotential measurements, despite important drawbacks such as skin irritation, long set-up time and uncomfortable removal. Recently introduced dry electrodes with rigid metal pins overcome most of these problems; however, their rigidity causes discomfort and pain. This paper presents dry electrodes o...

Dry electrodes provide the possibility of moving EEG usage from the research and clinical environment to real life applications. Having a framework for evaluating the performance of dry electrodes would facilitate this process and help EEG system developers to test their designs. This paper describes an evaluation method for dry electrode EEG recor...

Dry-contact electrodes have paved the way for easy-to-use electroencephalography (EEG) systems with minimal setup time, which are of particular interest in ambulatory as well as real-life environments. However, the presence of motion artifacts forms a major obstacle for such systems. In previous studies, it has been shown that continuous electrode-...

Timely mental stress detection can help to prevent stress-related health problems. The aim of this study was to identify those physiological signals and features suitable for detecting mental stress in office-like situations. Electrocardiogram (ECG), respiration, skin conductance and surface electromyogram (sEMG) of the upper trapezius muscle were...

Soft, comfortable polymer-based dry electrodes are fabricated. Impedance and biopotential measurements are carried out to compare the performance of conventional gel electrodes with our dry electrodes. The impedance of our dry electrodes is reduced by adding more conductive additives to the polymer material. To further lower the impedance, two skin...

Electroencephalography (EEG) testing in clinical labs makes use of large amplifiers and complex software for data acquisition. While there are new ambulatory electroencephalogram (EEG) systems, few have been directly compared to a gold standard system. Here, an ultra-low power wireless EEG system designed by Imec is tested against the gold standard...

The success of applying dry sensor technology in measuring electroencephalogram (EEG) signals will have a significant impact on a wider adoption of brain activity monitoring in ambulatory as well as real life solutions. The presence of motion artifacts is the major obstacle in applying dry sensors for long-term EEG monitoring. In this paper we asse...

Development of Wireless EEG system is described. Realtime impedance monitoring and active electrodes are introduced in order to reduce noise from impedance changes caused due to body motion, and to prevent noise from power line interference, respectively. EEG ASICs are developed for the system. The complete system has a low noise (60nV/√Hz) and is...

In this paper, we present a miniaturized (<6cm(3)) and low noise (60nV/root Hz) wireless EEG sensor node with active electrodes and simultaneous electrode tissue impedance (ETI) monitoring. The added benefit of the active electrodes and continuous ETI monitoring is quantified in terms of susceptibility against power line interference and cable moti...

This paper studies the influence of electrode coating material and contact force on the electrical contact impedance between such electrodes and skin. The electrical interface that exists between the electrode and the skin was modeled, and the modeling parameters as a function of force and material were derived. Increasing force from 80g to 350g de...

It is well known that chronic mental stress can cause health problems. Early stress detection can help prevent these problems. We propose and compare two approaches to estimate stress level from physiology. We have measured physiological signals in three different artificial stressful conditions involving problem solving under time pressure and mem...

This paper presents an active electrode system for gel-free biopotential EEG signal acquisition. The system consists of front-end chopper amplifiers and a back-end common-mode feedback (CMFB) circuit. The front-end AC-coupled chopper amplifier employs input impedance boosting and digitally-assisted offset trimming. The former increases the input im...

Early mental stress detection can prevent many stress related health problems. This study aimed at using a wearable sensor system to measure physiological signals and detect mental stress. Three different stress conditions were presented to a healthy subject group. During the procedure, ECG, respiration, skin conductance, and EMG of the trapezius m...

Intelligent affective computers can have many medical and non-medical applications. However today's affective computers are limited in scope by their transferability to other application environments or that they monitor only one aspect of physiological emotion expression. Here, the use of a wireless EEG system, which can be implemented in a body a...

Miniaturized, low power and low noise circuits and systems are instrumental in bringing EEG monitoring to the home environment. In this paper, we present a miniaturized, low noise and low-power EEG wireless platform integrated into a wearable headset. The wireless EEG headset achieves remote and wearable monitoring of up to 8 EEG channels. The head...

Ambulatory monitoring of body sounds is still hindered today by a lack of systematic optimization of sensor, sensor packaging and mounting conditions. This paper presents generic, objective and application-independent evaluation methods that can be used for quantitative on-body sensor optimization. The methods are applied on the evaluation of a thi...

Stress is a growing problem in society and can, amongst others, induce musculoskeletal complaints, related to sustained muscle tension. The ability to measure stress with a wireless system would be useful in the prevention of stress-related health problems. The aim of this experiment was to derive stress levels of subjects from electromyography (EM...

With new advances in ambulatory monitoring new challenges appear due to degradation in signal quality and limitations in hardware requirements. Existing signal analysis methods should be re-evaluated in order to adapt to the restrictive requirements of these new applications. With this motivation, we chose a robust beat detection algorithm and opti...

This paper illustrates how body area network technology may enable new personal health concepts. A BAN technology platform is presented, which integrates technology building blocks from the Human++ research program on autonomous wireless sensors. Technology evaluation for the case of wireless sleep staging and real-time arousal monitoring is report...

Robust beat detection under noisy conditions is required in order to obtain a correct clinical interpretation of the ECG in ambulatory settings. This paper describes the evaluation and optimization of a beat detection algorithm that is robust against high levels of noise. An evaluation protocol is defined in order to study four different characteri...

The Human++ program aims at achieving highly miniaturized, wireless, intelligent and autonomous body sensor nodes to assist our health, comfort and lifestyle. In this paper the concept of body area network is applied to wireless monitoring of emotions, thus opening a new, affective, dimension in human computer interaction. A prototype body area net...

The recent development of miniaturized, low-power components for body sensor networks pave the way towards intelligent and ambulatory monitoring devices with a plurality of applications. Here, the design and development of a real-time arousal monitor, based on Human++ Body Area Network components is described. A new set of biomarkers is proposed ba...

A body area network (BAN) for monitoring the autonomic nervous system responses is reported. The BAN is based on the Human++ UniNode, a small, low power generic wireless sensor node. Physiological signals are monitored using specifically designed ultra low power sensor front ends connected to the UniNodes. Two UniNodes compose the body area network...

A new method to assess noise reduction algorithms with respect to their ability to enhance the perceived quality of speech is pre-sented. Such algorithms consist of both single-microphone sys-tems and multiple microphone systems. Tests of the presented method show a higher correlation with subjective assessments than any other objective system know...

This paper deals with the synchronization properties of a family of spreading codes, called concatenated codes. New synchronization algorithms are introduced, and the performance of these algorithms is discussed both analytically and by simulation. It turns out that with a minimum of extra hardware, the mean phase acquisition time can be considerab...

This paper deals with the synchronization properties of a family of spreading codes, called concatenated codes. New synchronization algorithms are introduced, and the performance of these algorithms is discussed both analytically and by simulation. It turns out that with a minimum of extra hardware, the mean phase acquisition time can be considerab...