Toward the use of temporary tattoo electrodes for impedancemetric respiration monitoring and other electrophysiological recordings on skin

The development of dry, ultra-conformable and unperceivable temporary tattoo electrodes (TTEs), based on the ink-jet printing of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) on top of commercially available temporary tattoo paper, has gained increasing attention as a new and promising technology for electrophysiological recordings on skin. In this work, we present a TTEs epidermal sensor for real time monitoring of respiration through transthoracic impedance measurements, exploiting a new design, based on the application of soft screen printed Ag ink and magnetic interlink, that guarantees a repositionable, long-term stable and robust interconnection of TTEs with external “docking” devices. The efficiency of the TTE and the proposed interconnection strategy under stretching (up to 10%) and over time (up to 96 h) has been verified on a dedicated experimental setup and on humans, fulfilling the proposed specific application of transthoracic impedance measurements. The proposed approach makes this technology suitable for large-scale production and suitable not only for the specific use case presented, but also for real time monitoring of different bio-electric signals, as demonstrated through specific proof of concept demonstrators

Conception, development and evaluation of polymer-based screen-printed textile electrodes for biopotential monitoring

Wearable technologies represent the new frontier of vital signs monitoring in different applications, from fitness to health. With the progressive miniaturization of the electronic components, enabling the implementation of portable and hand-held acquisition and recording devices, the research focus has shifted toward the development of effective and unobtrusive textile electrodes. This work deals with the study, development and characterization of organic-polymer-based electrodes for biopotentials. After an overview of the main materials and fabrication technologies presented so far in the scientific literature, the possibility to use these electrodes as an alternative to the Ag/AgCl disposable gelled electrodes usually adopted in clinical practice was tested. For this purpose, several textile electrode realization techniques were studied and optimized, in order to create electrodes with adequate features to detect two fundamental physiological signals: the electrocardiogram (ECG) and the electromyogram (EMG). The electrodes were obtained by depositing on the fabric the organic bio-compatible polymer poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) with three deposition procedures: dipcoating, ink-jet printing and screen printing. The physical\u2013chemical properties of the polymer solution were varied for each procedure to obtain an optimal and reproducible result. For what concerns the ECG signal, the research activity focused on screen-printed textile electrodes and their performance was first assessed by benchtop measurements and then by human trials. The first tests demonstrated that, by adding solid or liquid electrolytes the electrodes, the largest part of the characteristics required by the ANSI/AAMI EC12:2000 standard for gelled ECG electrodes can be achieved. Tests performed in different conditions showed that the skin contact impedance and the ECG morphological features are highly similar to those obtainable with disposable gelled Ag/AgCl electrodes (\u3c1 > 0.99). A trial with ten subjects revealed also the capability of the proposed electrodes to accurately capture with clinical instruments an ECG morphology with performance comparable to off-the-shelf disposable electrodes. Furthermore, the proposed textile electrodes preserve their electrical properties and functionality even after several mild washing cycles, while they suffered physical stretching. Similar tests were performed on screen-printed textile electrodes fabricated in two different sizes to test them as EMG sensors, with and without electrolytes. After a series of controlled acquisitions performed by electro-stimulating the muscles in order to analyze the waveform morphologu of the M-wave, the statistical analysis showed a high similarity in terms of rms of the noise and electrode-skin impedance between conventional and textile electrodes with the addition of solid hydrogel and saline solution. Furthermore, the M-wave recorded on the tibialis anterior muscle during the stimulation of the peroneal nerve was comparatively analyzed between conventional and textile electrodes. The comparison provided an R2 value higher than 97% in all measurement conditions. These results opened their use in smart garments for real application scenarios and for this purpose were developed a couple of smart shirts able to detect the EGC and the EMG signal. The results indicated that this approach could be adopted in the future for the development of smart garments able to comfortably detect physiological signals

Wearables in medicine

Wearables as medical technologies are becoming an integral part of personal analytics, measuring physical status, recording physiological parameters, or informing schedule for medication. These continuously evolving technology platforms do not only promise to help people pursue a healthier life style, but also provide continuous medical data for actively tracking metabolic status, diagnosis, and treatment. Advances in the miniaturization of flexible electronics, electrochemical biosensors, microfluidics, and artificial intelligence algorithms have led to wearable devices that can generate real-time medical data within the Internet of things. These flexible devices can be configured to make conformal contact with epidermal, ocular, intracochlear, and dental interfaces to collect biochemical or electrophysiological signals. This article discusses consumer trends in wearable electronics, commercial and emerging devices, and fabrication methods. It also reviews real-time monitoring of vital signs using biosensors, stimuli-responsive materials for drug delivery, and closed-loop theranostic systems. It covers future challenges in augmented, virtual, and mixed reality, communication modes, energy management, displays, conformity, and data safety. The development of patient-oriented wearable technologies and their incorporation in randomized clinical trials will facilitate the design of safe and effective approaches

From wearable towards epidermal computing : soft wearable devices for rich interaction on the skin

Human skin provides a large, always available, and easy to access real-estate for interaction. Recent advances in new materials, electronics, and human-computer interaction have led to the emergence of electronic devices that reside directly on the user's skin. These conformal devices, referred to as Epidermal Devices, have mechanical properties compatible with human skin: they are very thin, often thinner than human hair; they elastically deform when the body is moving, and stretch with the user's skin. Firstly, this thesis provides a conceptual understanding of Epidermal Devices in the HCI literature. We compare and contrast them with other technical approaches that enable novel on-skin interactions. Then, through a multi-disciplinary analysis of Epidermal Devices, we identify the design goals and challenges that need to be addressed for advancing this emerging research area in HCI. Following this, our fundamental empirical research investigated how epidermal devices of different rigidity levels affect passive and active tactile perception. Generally, a correlation was found between the device rigidity and tactile sensitivity thresholds as well as roughness discrimination ability. Based on these findings, we derive design recommendations for realizing epidermal devices. Secondly, this thesis contributes novel Epidermal Devices that enable rich on-body interaction. SkinMarks contributes to the fabrication and design of novel Epidermal Devices that are highly skin-conformal and enable touch, squeeze, and bend sensing with co-located visual output. These devices can be deployed on highly challenging body locations, enabling novel interaction techniques and expanding the design space of on-body interaction. Multi-Touch Skin enables high-resolution multi-touch input on the body. We present the first non-rectangular and high-resolution multi-touch sensor overlays for use on skin and introduce a design tool that generates such sensors in custom shapes and sizes. Empirical results from two technical evaluations confirm that the sensor achieves a high signal-to-noise ratio on the body under various grounding conditions and has a high spatial accuracy even when subjected to strong deformations. Thirdly, Epidermal Devices are in contact with the skin, they offer opportunities for sensing rich physiological signals from the body. To leverage this unique property, this thesis presents rapid fabrication and computational design techniques for realizing Multi-Modal Epidermal Devices that can measure multiple physiological signals from the human body. Devices fabricated through these techniques can measure ECG (Electrocardiogram), EMG (Electromyogram), and EDA (Electro-Dermal Activity). We also contribute a computational design and optimization method based on underlying human anatomical models to create optimized device designs that provide an optimal trade-off between physiological signal acquisition capability and device size. The graphical tool allows for easily specifying design preferences and to visually analyze the generated designs in real-time, enabling designer-in-the-loop optimization. Experimental results show high quantitative agreement between the prediction of the optimizer and experimentally collected physiological data. Finally, taking a multi-disciplinary perspective, we outline the roadmap for future research in this area by highlighting the next important steps, opportunities, and challenges. Taken together, this thesis contributes towards a holistic understanding of Epidermal Devices}: it provides an empirical and conceptual understanding as well as technical insights through contributions in DIY (Do-It-Yourself), rapid fabrication, and computational design techniques.Die menschliche Haut bietet eine große, stets verfügbare und leicht zugängliche Fläche für Interaktion. Jüngste Fortschritte in den Bereichen Materialwissenschaft, Elektronik und Mensch-Computer-Interaktion (Human-Computer-Interaction, HCI) [so that you can later use the Englisch abbreviation] haben zur Entwicklung elektronischer Geräte geführt, die sich direkt auf der Haut des Benutzers befinden. Diese sogenannten Epidermisgeräte haben mechanische Eigenschaften, die mit der menschlichen Haut kompatibel sind: Sie sind sehr dünn, oft dünner als ein menschliches Haar; sie verformen sich elastisch, wenn sich der Körper bewegt, und dehnen sich mit der Haut des Benutzers. Diese Thesis bietet, erstens, ein konzeptionelles Verständnis von Epidermisgeräten in der HCI-Literatur. Wir vergleichen sie mit anderen technischen Ansätzen, die neuartige Interaktionen auf der Haut ermöglichen. Dann identifizieren wir durch eine multidisziplinäre Analyse von Epidermisgeräten die Designziele und Herausforderungen, die angegangen werden müssen, um diesen aufstrebenden Forschungsbereich voranzubringen. Im Anschluss daran untersuchten wir in unserer empirischen Grundlagenforschung, wie epidermale Geräte unterschiedlicher Steifigkeit die passive und aktive taktile Wahrnehmung beeinflussen. Im Allgemeinen wurde eine Korrelation zwischen der Steifigkeit des Geräts und den taktilen Empfindlichkeitsschwellen sowie der Fähigkeit zur Rauheitsunterscheidung festgestellt. Basierend auf diesen Ergebnissen leiten wir Designempfehlungen für die Realisierung epidermaler Geräte ab. Zweitens trägt diese Thesis zu neuartigen Epidermisgeräten bei, die eine reichhaltige Interaktion am Körper ermöglichen. SkinMarks trägt zur Herstellung und zum Design neuartiger Epidermisgeräte bei, die hochgradig an die Haut angepasst sind und Berührungs-, Quetsch- und Biegesensoren mit gleichzeitiger visueller Ausgabe ermöglichen. Diese Geräte können an sehr schwierigen Körperstellen eingesetzt werden, ermöglichen neuartige Interaktionstechniken und erweitern den Designraum für die Interaktion am Körper. Multi-Touch Skin ermöglicht hochauflösende Multi-Touch-Eingaben am Körper. Wir präsentieren die ersten nicht-rechteckigen und hochauflösenden Multi-Touch-Sensor-Overlays zur Verwendung auf der Haut und stellen ein Design-Tool vor, das solche Sensoren in benutzerdefinierten Formen und Größen erzeugt. Empirische Ergebnisse aus zwei technischen Evaluierungen bestätigen, dass der Sensor auf dem Körper unter verschiedenen Bedingungen ein hohes Signal-Rausch-Verhältnis erreicht und eine hohe räumliche Auflösung aufweist, selbst wenn er starken Verformungen ausgesetzt ist. Drittens, da Epidermisgeräte in Kontakt mit der Haut stehen, bieten sie die Möglichkeit, reichhaltige physiologische Signale des Körpers zu erfassen. Um diese einzigartige Eigenschaft zu nutzen, werden in dieser Arbeit Techniken zur schnellen Herstellung und zum computergestützten Design von multimodalen Epidermisgeräten vorgestellt, die mehrere physiologische Signale des menschlichen Körpers messen können. Die mit diesen Techniken hergestellten Geräte können EKG (Elektrokardiogramm), EMG (Elektromyogramm) und EDA (elektrodermale Aktivität) messen. Darüber hinaus stellen wir eine computergestützte Design- und Optimierungsmethode vor, die auf den zugrunde liegenden anatomischen Modellen des Menschen basiert, um optimierte Gerätedesigns zu erstellen. Diese Designs bieten einen optimalen Kompromiss zwischen der Fähigkeit zur Erfassung physiologischer Signale und der Größe des Geräts. Das grafische Tool ermöglicht die einfache Festlegung von Designpräferenzen und die visuelle Analyse der generierten Designs in Echtzeit, was eine Optimierung durch den Designer im laufenden Betrieb ermöglicht. Experimentelle Ergebnisse zeigen eine hohe quantitative Übereinstimmung zwischen den Vorhersagen des Optimierers und den experimentell erfassten physiologischen Daten. Schließlich skizzieren wir aus einer multidisziplinären Perspektive einen Fahrplan für zukünftige Forschung in diesem Bereich, indem wir die nächsten wichtigen Schritte, Möglichkeiten und Herausforderungen hervorheben. Insgesamt trägt diese Arbeit zu einem ganzheitlichen Verständnis von Epidermisgeräten bei: Sie liefert ein empirisches und konzeptionelles Verständnis sowie technische Einblicke durch Beiträge zu DIY (Do-It-Yourself), schneller Fertigung und computergestützten Entwurfstechniken

Feature Papers in Electronic Materials Section

This book entitled "Feature Papers in Electronic Materials Section" is a collection of selected papers recently published on the journal Materials, focusing on the latest advances in electronic materials and devices in different fields (e.g., power- and high-frequency electronics, optoelectronic devices, detectors, etc.). In the first part of the book, many articles are dedicated to wide band gap semiconductors (e.g., SiC, GaN, Ga2O3, diamond), focusing on the current relevant materials and devices technology issues. The second part of the book is a miscellaneous of other electronics materials for various applications, including two-dimensional materials for optoelectronic and high-frequency devices. Finally, some recent advances in materials and flexible sensors for bioelectronics and medical applications are presented at the end of the book