The status of textile-based dry EEG electrodes

Electroencephalogram (EEG) is the biopotential recording of electrical signals generated by brain activity. It is useful for monitoring sleep quality and alertness, clinical applications, diagnosis, and treatment of patients with epilepsy, disease of Parkinson and other neurological disorders, as well as continuous monitoring of tiredness/ alertness in the field. We provide a review of textile-based EEG. Most of the developed textile-based EEGs remain on shelves only as published research results due to a limitation of flexibility, stickability, and washability, although the respective authors of the works reported that signals were obtained comparable to standard EEG. In addition, nearly all published works were not quantitatively compared and contrasted with conventional wet electrodes to prove feasibility for the actual application. This scenario would probably continue to give a publication credit, but does not add to the growth of the specific field, unless otherwise new integration approaches and new conductive polymer composites are evolved to make the application of textile-based EEG happen for bio-potential monitoring

Southwest Research Institute assistance to NASA in biomedical areas of the technology utilization program Final report, 1 Feb. 1969 - 24 Aug. 1970

Research progress in technology transfer by NASA Biomedical Application Tea

Development and Characterization of Ear-EEG for Real-Life Brain-Monitoring

Functional brain monitoring methods for neuroscience and medical diagnostics have until recently been limited to laboratory settings. However, there is a great potential for studying the human brain in the everyday life, with measurements performed in more realistic real-life settings. Electroencephalography (EEG) can be measured in real-life using wearable EEG equipment. Current wearable EEG devices are typically based on scalp electrodes, causing the devices to be visible and often uncomfortable to wear for long-term recordings. Ear-EEG is a method where EEG is recorded from electrodes placed in the ear. The Ear-EEG supports non-invasive long-term recordings of EEG in real-life in a discreet way. This Ph.D. project concerns the characterization and development of ear-EEG for real-life brain-monitoring. This was addressed through characterization of physiological artifacts in real-life settings, development and characterization of dry-contact electrodes for real-life ear-EEG acquisition, measurements of ear-EEG in real-life, and development of a method for mapping cortical sources to the ear. Characterization of physiological artifacts showed a similar artifact level for recordings from ear electrodes and temporal lobe scalp electrodes. Dry-contact electrodes and flexible earpieces were developed to increase the comfort and user-friendliness of the ear-EEG. In addition, electronic instrumentation was developed to allow implementation in a hearing-aid-sized ear-EEG device. Ear-EEG measurements performed in real-life settings with the dry-contact electrodes, were comparable to temporal lobe scalp EEG, when referenced to a Cz scalp electrode. However, the recordings showed that further development of the earpieces and electrodes are needed to obtain a satisfying recording quality, when the reference is located close to or in the ear. Mapping of the electric fields from well-defined cortical sources to the ear, showed good agreement with previous ear-EEG studies and has the potential to provide valuable information for future development of the ear-EEG method. The Ph.D. project showed that ear-EEG measurements can be performed in real-life, with dry-contact electrodes. The brain processes studied, were established with comparable clarity on recordings from temporal lobe scalp and ear electrodes. With further development of the earpieces, electrodes, and electronic instrumentation, it appears to be realistic to implement ear-EEG into unobtrusive and user-friendly devices for monitoring of human brain processes in real-life

Skin-Like Electronics for a Persistent Brain-Computer Interface

There exists a high demand for a continuous, persistent recording of non-invasive electroencephalograms in both clinical and research fields. Head-cap electrodes with metal conductors and conductive gels are widely used and considered as the gold standard for such measurement. This physical interface, however, is poorly suited to uninterrupted, long-term use due to the uncomfortable rigid electrodes, skin irritation due to the gel, and electrical degradation as the gel dries. These issues can be addressed by using a newly developed, dry form of electronics. Here, we briefly review a class of soft electronic technology in the aspects of mechanics, materials, and its capabilities for a long-term recording of electroencephalograms and a brain-computer interface (BCI). We summarize the progress in the development of a skin-like electronic system with a focus on key mechanical factors to achieve conformal skin contact. The design of hard electronics, integrated with soft membranes, uses deterministic fractal motifs to offer bending and stretching mechanics. We also introduce a most recent example of such electronics, an ‘auricle-integrated system’, which includes a strategy of conformal integration on the complex surface topology, a quantitative study of biocompatibility, and an application as a persistent BCI

Soft, curved electrode systems capable of integration on the auricle as a persistent brain–computer interface

Recent advances in electrodes for noninvasive recording of electroencephalograms expand opportunities collecting such data for diagnosis of neurological disorders and brain–computer interfaces. Existing technologies, however, cannot be used effectively in continuous, uninterrupted modes for more than a few days due to irritation and irreversible degradation in the electrical and mechanical properties of the skin interface. Here we introduce a soft, foldable collection of electrodes in open, fractal mesh geometries that can mount directly and chronically on the complex surface topology of the auricle and the mastoid, to provide high-fidelity and long-term capture of electroencephalograms in ways that avoid any significant thermal, electrical, or mechanical loading of the skin. Experimental and computational studies establish the fundamental aspects of the bending and stretching mechanics that enable this type of intimate integration on the highly irregular and textured surfaces of the auricle. Cell level tests and thermal imaging studies establish the biocompatibility and wearability of such systems, with examples of high-quality measurements over periods of 2 wk with devices that remain mounted throughout daily activities including vigorous exercise, swimming, sleeping, and bathing. Demonstrations include a text speller with a steady-state visually evoked potential-based brain–computer interface and elicitation of an event-related potential (P300 wave)

Technology applications

A summary of NASA Technology Utilization programs for the period of 1 December 1971 through 31 May 1972 is presented. An abbreviated description of the overall Technology Utilization Applications Program is provided as a background for the specific applications examples. Subjects discussed are in the broad headings of: (1) cancer, (2) cardiovascular disease, (2) medical instrumentation, (4) urinary system disorders, (5) rehabilitation medicine, (6) air and water pollution, (7) housing and urban construction, (8) fire safety, (9) law enforcement and criminalistics, (10) transportation, and (11) mine safety

Development and Characterization of highly flexible and conformable electronic devices for wearable applications

As shown in the story, humanity has tried to develop objects, tools, and devices that could first help to survive in a difficult environment and then improve everyday life. The idea of creating objects that can be worn to restore or improve human abilities or to help during daily routine has fueled technological development and research since the beginning of technological advancement. Wearable technology goes back hundreds of years, and one of the first examples was the invention of glasses to restore the sight, or the wristwatch when big watches were reduced to something that people could take with them anywhere. However, it could be considered that, only when the computer age was established, wearable electronic devices were developed and started to spread out and get into the market. Wearable electronics are a category of technological devices that can be transferred into clothes or directly in touch with the body, typically as accessories or clothing, and these devices can be designed to provide different functionalities, such as notification sending, communication abilities, health and fitness monitoring, and even augmented or virtual reality experiences. In recent years, organic electronics have been deeply investigated as a technology platform to develop devices using biocompatible materials that can be deposited and processed on flexible and even ultra-flexible substrates. The high mechanical flexibility of such materials leads to a new category of devices going beyond wearable devices to more-than-wearable applications. In this context, epidermal electronics is a closely related field that focuses on developing electronic devices that can be directly attached to the skin with a minimally invasive, comfortable, and possibly enabling long-term application. The main object of this Ph.D. research activity is the development and optimization of a technology for the realization of wearable and more-than-wearable devices, able to meet all the new needs in this field, such as the low-cost production process and the mechanical flexibility of the devices and deposition over large areas on unconventional substrates, exploiting all the features and advantages of the organic electronic field, but also finding some solution to overcome the disadvantages of this technology. In this work, different application fields were studied, such as health monitoring through biopotential acquisitions, the development, and optimization of multimodal physical sensors able to detect simultaneously pressure and temperature for tactile and artificial skin applications, and the development of flexible high-performing transistors as a building block for the future of wearable and electronic-skin applications

Wireless ear EEG to monitor drowsiness.

Neural wearables can enable life-saving drowsiness and health monitoring for pilots and drivers. While existing in-cabin sensors may provide alerts, wearables can enable monitoring across more environments. Current neural wearables are promising but most require wet-electrodes and bulky electronics. This work showcases in-ear, dry-electrode earpieces used to monitor drowsiness with compact hardware. The employed system integrates additive-manufacturing for dry, user-generic earpieces, existing wireless electronics, and offline classification algorithms. Thirty-five hours of electrophysiological data were recorded across nine subjects performing drowsiness-inducing tasks. Three classifier models were trained with user-specific, leave-one-trial-out, and leave-one-user-out splits. The support-vector-machine classifier achieved an accuracy of 93.2% while evaluating users it has seen before and 93.3% when evaluating a never-before-seen user. These results demonstrate wireless, dry, user-generic earpieces used to classify drowsiness with comparable accuracies to existing state-of-the-art, wet electrode in-ear and scalp systems. Further, this work illustrates the feasibility of population-trained classification in future electrophysiological applications

Hybrid head cap for mouse brain studies

Abstract. In this thesis, I present a hybrid head cap in combination with non-invasive multi-channel Electroencephalogram (EEG) and Near-Infrared Spectroscopy (NIRS) to measure brainwaves on mice’s scalps. Laboratory animal research provides insights into multiple potential applications involving humans and other animals. An experimental framework that targets laboratory animals can lead to useful transnational research if it strongly reflects the actual application environment. The non-invasive head cap with three electrodes for EEG and two optodes for NIRS is suggested to measure brainwaves throughout the laboratory mice’s entire brain region without surgical procedures. The suggested hybrid head cap aims to ensure stability in vivo monitoring for mouse brain in a non-invasive way, similarly as the monitoring is performed for the human brain. The experimental part of the work to study the quality of the gathered EEG and fNIRS signals, and usability validation of the head cap, however, was not completed in the planned time frame of the thesis work