Study on conductive hydrogels in flexible and wearable triboelectric devices towards energy-harvesting and sensing applications (エネルギーハーベスティングおよびセンシングに向けたフレキシブルでウェアラブルな摩擦発電デバイスにおける導電性ハイドロゲルに関する研究)

信州大学(Shinshu university)博士（工学）この博士論文は、次の学術雑誌論文を一部に使用しています。 / ACS Applied Materials Interfaces 14(7) :9126-9137(2022); doi:10.1021/acsami.1c23176 / Advanced Fiber Materials 4(6) :1486-1499(2022); doi:10.1007/s42765-022-00181-4 / Chemical Engineering Journal 457 :141276(2023); doi:10.1016/j.cej.2023.141276ThesisDONG, LI. Study on conductive hydrogels in flexible and wearable triboelectric devices towards energy-harvesting and sensing applications (エネルギーハーベスティングおよびセンシングに向けたフレキシブルでウェアラブルな摩擦発電デバイスにおける導電性ハイドロゲルに関する研究). 信州大学, 2023, 博士論文. 博士（工学）, 甲第802号, 令和05年03月20日授与.doctoral thesi

Fully Integrated Biochip Platforms for Advanced Healthcare

Recent advances in microelectronics and biosensors are enabling developments of innovative biochips for advanced healthcare by providing fully integrated platforms for continuous monitoring of a large set of human disease biomarkers. Continuous monitoring of several human metabolites can be addressed by using fully integrated and minimally invasive devices located in the sub-cutis, typically in the peritoneal region. This extends the techniques of continuous monitoring of glucose currently being pursued with diabetic patients. However, several issues have to be considered in order to succeed in developing fully integrated and minimally invasive implantable devices. These innovative devices require a high-degree of integration, minimal invasive surgery, long-term biocompatibility, security and privacy in data transmission, high reliability, high reproducibility, high specificity, low detection limit and high sensitivity. Recent advances in the field have already proposed possible solutions for several of these issues. The aim of the present paper is to present a broad spectrum of recent results and to propose future directions of development in order to obtain fully implantable systems for the continuous monitoring of the human metabolism in advanced healthcare applications

Bioinspired Designs and Biomimetic Applications of Triboelectric Nanogenerators

The emerging novel power generation technology of triboelectric nanogenerators (TENGs) is attracting increasing attention due to its unlimited prospects in energy harvesting and self-powered sensing applications. The most important factors that determine TENGs’ electrical and mechanical performance include the device structure, surface morphology and the type of triboelectric material employed, all of which have been investigated in the past to optimize and enhance the performance of TENG devices. Amongst them, bioinspired designs, which mimic structures, surface morphologies, material properties and sensing/power generation mechanisms from nature, have largely benefited in terms of enhanced performance of TENGs. In addition, a variety of biomimetic applications based on TENGs have been explored due to the simple structure, self-powered property and tunable output of TENGs. In this review article, we present a comprehensive review of various researches within the specific focus of bioinspired TENGs and TENG enabled biomimetic applications. The review begins with a summary of the various bioinspired TENGs developed in the past with a comparative analysis of the various device structures, surface morphologies and materials inspired from nature and the resultant improvement in the TENG performance. Various ubiquitous sensing principles and power generation mechanisms in use in nature and their analogous artificial TENG designs are corroborated. TENG-enabled biomimetic applications in artificial electronic skins and neuromorphic devices are discussed. The paper concludes by providing a perspective towards promising directions for future research in this burgeoning field of study

A versatile wearable based on reconfigurable hardware for biomedical measurements

In this work a versatile hardware platform based on reconfigurable devices is presented. This platform it intended for the acquisition of multiple biosignals, only requiring a reconfiguration to switch applications. This prototype has been combined with graphene-based, flexible electrodes to cover the application to different biosignals presented in this paper, which are electrocardiogram, electrooculogram and electromyogram. The features of this system provide to the user and to medical personnel a complete set of diagnosis tools, available both at home and hospitals, to be used as a triage tool and for remote patient monitoring. Additionally, an Android application has been developed for signal processing and data presentation to the user. The results obtained demonstrate the wide range of possibilities in portable/wearable applications of the combination of reconfigurable devices and flexible electronics, especially for the remote monitoring of patients using multiple biosignals of interest. The versatility of this device makes it a complete set of monitoring tools integrated in a reduced size device

Polymeric Microsensors for Intraoperative Contact Pressure Measurement

Biocompatible sensors have been demonstrated using traditional microfabrication techniques modified for polymer substrates and utilize only materials suitable for implantation or bodily contact. Sensor arrays for the measurement of the load condition of polyethylene spacers in the total knee arthroplasty (TKA) prosthesis have been developed. Arrays of capacitive sensors are used to determine the three-dimensional strain within the polyethylene prosthesis component. Data from these sensors can be used to give researchers a better understanding of component motion, loading, and wear phenomena for a large range of activities. This dissertation demonstrates both analytically and experimentally the fabrication of these sensor arrays using biocompatible polymer substrates and dielectrics while preserving industry-standard microfabrication processing for micron-level resolution. An array of sensors for real-time measurement of pressure profiles is the long-term goal of this research. A custom design using capacitive-based sensors is an excellent selection for such measurement, giving high spatial resolution across the sensing surface and high load resolution for pressures applied normal to that surface while operating at low power

Wearable bio and chemical sensors

Chemical and biochemical sensors have experienced tremendous growth in the past decade due to advances in material chemistry combined with the emergence of digital communication technologies and wireless sensor networks (WSNs) [1]. The emergence of wearable chemical and biochemical sensors is a relatively new concept that poses unique challenges to the field of wearable sensing. This is because chemical sensors have a more complex mode of operation, compared to physical transducers, in that they must interact in some manner with specific molecular targets in the sample medium. To understand the challenges in developing wearable chemical and biochemical sensors the traits of these devices will be discussed in this introductory section. Following this the potential parameters of interest are presented and examples of wearable systems are discussed. A range of sampling techniques and methods of chemical sensing are presented along with integration issues and design challenges. Finally, some of the main application areas of this novel technology are discussed

Smartphone-Based pH Sensor for Home Monitoring of Pulmonary Exacerbations in Cystic Fibrosis.

Currently, Cystic Fibrosis (CF) patients lack the ability to track their lung health at home, relying instead on doctor checkups leading to delayed treatment and lung damage. By leveraging the ubiquity of the smartphone to lower costs and increase portability, a smartphone-based peripheral pH measurement device was designed to attach directly to the headphone port to harvest power and communicate with a smartphone application. This platform was tested using prepared pH buffers and sputum samples from CF patients. The system matches within ~0.03 pH of a benchtop pH meter while fully powering itself and communicating with a Samsung Galaxy S3 smartphone paired with either a glass or Iridium Oxide (IrOx) electrode. The IrOx electrodes were found to have 25% higher sensitivity than the glass probes at the expense of larger drift and matrix sensitivity that can be addressed with proper calibration. The smartphone-based platform has been demonstrated as a portable replacement for laboratory pH meters, and supports both highly robust glass probes and the sensitive and miniature IrOx electrodes with calibration. This tool can enable more frequent pH sputum tracking for CF patients to help detect the onset of pulmonary exacerbation to provide timely and appropriate treatment before serious damage occurs

User-interactive wirelessly-communicating “smart” textiles made from multimaterial fibers

En raison de la nature intime des interactions homme-textiles (essentiellement, nous sommes entourés par les textiles 24/7 - soit sous la forme de vêtements que nous portons ou comme rembourrage dans nos voitures, maisons, bureaux, etc.), les textiles intelligents sont devenus des plates-formes de plus en plus attrayantes pour les réseaux de capteurs innovants biomédicaux, transducteurs, et des microprocesseurs dédiés à la surveillance continue de la santé. En même temps, l'approche commune dans le domaine des textiles intelligents consiste en l'adaptation de la microélectronique planaire classique à une sorte de substrat souple. Cela se traduit souvent par de mauvaises propriétés mécaniques et donc des compromis au niveau du confort et de l'acceptation des usagers, qui à leur tour peuvent probablement expliquer pourquoi ces solutions émergent rarement du laboratoire et, à l'exception de certains cas très spécifiques, ne soit pas utilisés dans la vie de tous les jours. Par ailleurs, nous assistons présentement à un changement de paradigme au niveau de l'informatique autonome classique vers le concept de calculs distribués (ou informatique en nuage). Dans ce cas, la puissance de calcul du nœud individuel ou d'un dispositif de textile intelligent est moins importante que la capacité de transmettre des données à l'Internet. Dans ce travail, je propose une nouvelle approche basée sur l'intégration de polymère, verre et métal dans des structures de fibres miniaturisées afin de réaliser des dispositifs de textiles intelligents de prochaine génération avec des fonctionnalités de niveau supérieur (comme la communication sans fil, la reconnaissance tactile, les interconnexions électriques) tout en ayant une forme minimalement envahissante. Tout d'abord, j'étudie différents modèles d'antennes compatibles avec la géométrie des fibres et des techniques de fabrication. Ensuite, je démontre expérimentalement que ces antennes en fibres multi-matériaux peuvent être intégrées dans les textiles lors d’un processus standard de fabrication de textiles. Les tests effectués sur ces textiles ont montré que, pour les scénarios «sur-corps et hors-corps», les propriétés émissives en termes de perte de retour (S11), le patron (diagramme) de radiation, l'efficacité (gain), et le taux d'erreur binaire (TEB) sont directement comparables à des solutions classiques rigides. Ces antennes sont adéquates pour les communications à courte portée des applications de communications sans fil ayant un débit de données de Mo/s (méga-octets par seconde) (via protocoles Bluetooth et IEEE 802.15.4 à la fréquence de 2,4 GHz). Des simulations numériques de taux d'absorption spécifique démontrent également le plein respect des règles de sécurité imposées par Industrie Canada pour les réseaux sans fil à proximité du corps humain. Puisque les matériaux composites de fibres métal-verre-polymère sont fabriqués en utilisant des fibres de silice creuses de diamètre submillimétrique et la technique de dépôt d'argent à l'état liquide, les éléments conducteurs sont protégés de l'environnement et ceci préserve aussi les propriétés mécaniques et esthétiques des vêtements. Cet aspect est confirmé par des essais correspondant aux normes de l'industrie du textile, l'étirement standard et des essais de flexion. De plus, appliquer des revêtements superhydrophobes (WCA = 152º, SA = 6º) permet une communication sans fil sans interruption de ces textiles sous l'application directe de l'eau, même après plusieurs cycles de lavage. Enfin, le prototype de textile intelligent fabriqué interagit avec l'utilisateur à travers un détecteur tactile et transmet les données tactiles à travers le protocole Bluetooth à un smartphone. Cette démonstration valide l’approche des fibres multi-matériaux pour une variété d'applications.As we are surrounded by textiles 24/7, either in the form of garments that we wear or as upholstery in our cars, homes, offices, etc., textiles are especially attractive platforms for arrays of innovative biomedical sensors, transducers, and microprocessors dedicated, among other applications, to continuous health monitoring. In the same time, the common approach in the field of smart textiles consists in adaptation of conventional planar microelectronics to some kind of flexible substrate, which often results in poor mechanical properties and thus compromises wearing comfort and complicates garment care, which results in low user acceptance. This explains why such solutions rarely emerge from the lab and, with the exception of some very specific cases, cannot be seen in the everyday life. Furthermore, we are currently witnessing a global shift from classical standalone computing to the concept of distributed computation (e.g. so-called thin clients and cloud storage). In this context, the computation power of the individual node or smart textile device in this case, becomes progressively less important than the ability to relay data to the Internet. In this work, I propose a novel approach based on the idea of integration of polymer, glass and metal into miniaturized fiber structures in order to achieve next-generation smart textile devices with higher-level functionalities, such as wireless communication, touch recognition, electrical interconnects, with minimally-invasive attributes. First, I investigate different possible fiber-shaped antenna designs and fabrication techniques. Next, I experimentally demonstrate that such multi-material fiber antennas can be integrated into textiles during standard textile manufacturing process. Tests conducted on these textiles have shown that, for on-body and off-body scenarios, the emissive properties in terms of return loss (S11), radiation pattern, efficiency (gain), and bit-error rate (BER) are directly comparable to classic ‘rigid’ solutions and adequately address short-range wireless communications applications at Mbps data-rates (via Bluetooth and IEEE 802.15.4 protocols at 2.4 GHz frequency). Numerical simulations of the specific absorption rate (SAR) also demonstrate full compliance with safety regulations imposed by Industry Canada for wireless body area network devices. Since metal-glass-polymer fiber composites were fabricated using sub-millimetre hollow-core silica fibers and liquid state silver deposition technique, the conductor elements are shielded against the environment and preserve the mechanical and cosmetic properties of the garments. This is confirmed by the textile industry standard stretching and bending tests. Additionally, applied superhydrophobic coatings (WCA=152º, SA=6º) allow uninterrupted wireless communication of the textiles under direct water application even after multiple washing cycles. Finally, I fabricated a user-interactive and wireless-communicating smart textile prototype, that interacts with the user through capacitive touch-sensing and relays the touch data through Bluetooth protocol to a smartphone. This demonstration validates that the proposed approach based on multi-material fibers is suitable for applications to sensor fabrics and bio-sensing textiles connected in real time to mobile communications infrastructures, suitable for a variety of health and life science applications

Piezoelectric Energy Harvester Technologies: Synthesis, Mechanisms, and Multifunctional Applications.

Piezoelectric energy harvesters have gained significant attention in recent years due to their ability to convert ambient mechanical vibrations into electrical energy, which opens up new possibilities for environmental monitoring, asset tracking, portable technologies and powering remote "Internet of Things (IoT)" nodes and sensors. This review explores various aspects of piezoelectric energy harvesters, discussing the structural designs and fabrication techniques including inorganic-based energy harvesters (i.e., piezoelectric ceramics and ZnO nanostructures) and organic-based energy harvesters (i.e., polyvinylidene difluoride (PVDF) and its copolymers). The factors affecting the performance and several strategies to improve the efficiency of devices have been also explored. In addition, this review also demonstrated the progress in flexible energy harvesters with integration of flexibility and stretchability for next-generation wearable technologies used for body motion and health monitoring devices. The applications of the above devices to harvest various forms of mechanical energy are explored, as well as the discussion on perspectives and challenges in this field