Recent Advances in Energy Harvesting from the Human Body for Biomedical Applications

Energy harvesters serve as continuous and long-lasting sources of energy that can be integrated into wearable and implantable sensors and biomedical devices. This review paper presents the current progress, the challenges, the advantages, the disadvantages and the future trends of energy harvesters which can harvest energy from various sources from the human body. The most used types of energy are chemical; thermal and biomechanical and each group is represented by several nano-generators. Chemical energy can be harvested with a help of microbial and enzymatic biofuel cells, thermal energy is collected via thermal and pyroelectric nano-generators, biomechanical energy can be scavenged with piezoelectric and triboelectric materials, electromagnetic and electrostatic generators and photovoltaic effect allows scavenging of light energy. Their operating principles, power ratings, features, materials, and designs are presented. There are different ways of extracting the maximum energy and current trends and approaches in nanogenerator designs are discussed. The ever-growing interest in this field is linked to a larger role of wearable electronics in the future. Possible directions of future development are outlined; and practical biomedical applications of energy harvesters for glucose sensors, oximeters and pacemakers are presented. Based on the increasingly accumulated literature, there are continuous promising improvements which are anticipated to lead to portable and implantable devices without the requirement for batteries

Recent developments in 2D materials for energy harvesting applications

The ever-increasing demand for energy as a result of the growing interest in applications, such as the Internet of Things and wearable systems, etc, calls for the development of self-sustained energy harvesting solutions. In this regard, 2D materials have sparked enormous interest recently, due to their outstanding properties, such as ultra-thin geometry, high electromechanical coupling, large surface area to volume ratio, tunable band gap, transparency and flexibility. This has given rise to noteworthy advancements in energy harvesters such as triboelectric nanogenerators (TENGs), piezoelectric nanogenerators (PENGs) and photovoltaics based on 2D materials. This review introduces the properties of different 2D materials including graphene, transition metal dichalcogenides, MXenes, black phosphorus, hexagonal boron nitride, metal-organic frameworks and covalent-organic frameworks. A detailed discussion of recent developments in 2D materials-based PENG, TENG and photovoltaic devices is included. The review also considers the performance enhancement mechanism and importance of 2D materials in energy harvesting. Finally, the challenges and future perspectives are laid out to present future research directions for the further development and extension of 2D materials-based energy harvesters

Self-contained microfluidic platform for general purpose lab-on-chip using pcb-mems technology.

El presente trabajo está centrado en la investigación de una nueva plataforma microfluídica autónoma para propósito general fabricada en PCBMEMS. En la vista de la proliferación en los últimos años de los sistemas microfluídicos Lab on Chip (LoC) y la multitud de aplicaciones en las que tienen cabida, surge la necesidad de creación de un sistema portable, autónomo y con una fabricación orientada hacia la producción masiva. En este contexto, se presenta el trabajo de esta tesis dentro de los proyectos de investigación de financiación nacional ISILAB (TEC2011-29045-C04-02) y BIOLOP (TEC2014-54449-C3-2- R). La tesis se encuentra organizada para cubrir los aspectos previamente propuestos. Primeramente, se presenta una introducción donde se explican los motivos para el desarrollo de este trabajo y cuáles son los objetivos específicos que se quieren cumplir. Seguidamente, se hace un breve estudio del arte. En este estudio se presenta la tecnología MEMS, los principios básicos de la microfluídica, que son los fundamentos de los sistemas LOCs y por último, se detalla un estudio de los principales elementos activos en la literatura que componen una plataforma microfluídica. Después de la introducción y revisión literaria del marco de esta tesis, se explican los resultados obtenidos. Esta tesis está desarrollada en dos fases principales: el desarrollo de todos los componentes que hacen un lab on chip autónomo de propósito general y el desarrollo de una tecnología basada en estándares para una producción masiva. En la primera fase se detallan los principales componentes que forman parte de una plataforma autónoma multifunción: microválvula, sistema de impulsión, circuito microfluídico y plataforma de sensado. Todos estos componentes son diseñados como un prototipo y están fabricados en SU-8 y PCBMEMS. El PCB permanece como sustrato y los canales y cámaras microfluídicas están fabricados en SU-8. La microválvula diseñada presenta una activación termoeléctrica, es de un solo uso y tiene una rápida activación y un consumo bajo de energía. Además, el diseño está pensado para ser altamente integrable en una plataforma microfluídica. El siguiente componente descrito es una sistema de impulsión basado en cámaras presurizadas, este sistema está integrado con la microválvula y su principal característica es la activación en el momento de uso, asegurando la ausencia de pérdidas. Para probar la validez de los componentes anteriores, se desarrolla un circuito microfluídico de propósito general. El circuito está diseñado para mezclar dos muestras y transportarlas a una cámara de detección. Finalmente, se desarrolla una plataforma para la detección de glucosa, integrable en el circuito microfluídico. Una vez desarrollado el prototipo, el siguiente objetivo de la tesis es el paso de la tecnología de prototipado hacía una de producción masiva. Para ello los materiales utilizados son el PMMA y el PCB. La tecnología PCBMEMS es conocida por su versatilidad para la integración de la electrónica, por lo que lo hace idóneo para la conexión con el exterior. El PMMA es un material también muy extendido en las aplicaciones microfluídicas, debido a su transparencia, bio compatibilidad y su fácil modelado. La unión de los dos componentes representa un desafío en el desarrollo de la tesis, debido a sus diferentes propiedades químicas. El proceso de fabricación se desarrolla integrando la microválvula y el sistema de impulsión, como partes de una plataforma microfluídica. Para terminar, se ha diseñado un pequeño circuito microfluídico para probar la viabilidad del sistema propuesto hacia una tecnología de gran escala. Finalmente, se exponen las conclusiones de la investigación, las posibles líneas futuras de este trabajo y los apéndices que complementan el trabajo de la tesis.The work presented is focused on the investigation of a new autonomous microfluidic platform manufactured using PCBMEMS technology for general purpose. With the proliferation of the microfluidic platforms, Lab on Chip (LoC), and the multitude of applications which have placed in the market, there is a need to create a self-contained microfluidic platform for general purpose with mass production-oriented manufacturing. Within this framework, the work of this thesis is presented. This is part of two national research project ISILAB (TEC2011-29045-C04-02) and BIOLOP (TEC2014-54449-C3-2- R). The thesis is organized to cover the aspects previously explained. Firstly, an introduction is presented with the motivation and objectives of this work. Subsequently, a study of the art is done. This study presents theMEMS technology, the basics principles of microfluidics, which are the pillars of the lab on chips and finally, a study of the main active elements presented in the literature. After the introduction and the literary revision of the framework of this thesis, the results obtained are presented. This thesis is developed in two main phases: the development of all components that make an autonomous general purpose lab on chip and the development of a standards-based technology for mass production. The first phase details the main components of an autonomous multifunction platform: microvalve, impulsion system, microfluidic circuit and sensing platform. All of these components are designed as a prototype and are manufactured in SU- 8 and PCBMEMS. The PCB remains as a substrate, and the microfluidic channels and chambers are manufactured in SU-8. The microvalve developed is a single use thermoelectrical microvalve with fast activation and low power consumption. In addition, the design is thought to be highly integrable in a microfluidic plat-form. The next component is a impulsion system based on pressurized chambers. The system is integrated with the microvalve and its main characteristic is the activation at the moment of use, ensuring the absence of losses. To test the validity of the above components, a general purpose microfluidic circuit is developed. The circuit is designed to mix two samples and transport those to a detection chamber. Finally, a platform for the detection of glucose, integrable in the microfluidic circuit, is developed. Once the prototype is achieved, the next objective of the thesis is the migration from prototyping technology to mass production. To this end, the materials used are PMMA and PCB. PCBMEMS technology is known for its versatility for the integration of electronics, making it suitable for electrical connection. PMMA is also widely used in microfluidic applications due to its transparency, bio compatibility and easy modeling. The union of the two components represents a challenge in the development of the thesis due to its different chemical properties. The manufacturing process is developed by integrating the microvalve and the drive system, as parts of a microfluidic platform. In conclusion, a small microfluidic circuit is designed by testing the feasibility of the proposed system towards large-scale technology. Finally, the conclusions of the research, the possible future lines of this work and the appendices that complement the work of the thesis are presented

La réfrigération magnétique : conceptualisation, caractérisation et simulation

Magnetic refrigeration is a relevant alternative in consideration of environmental restrictions of refrigerants gases. These restrictions require to improve the current technology or to pave the way for a new one, hence the opportunity for magnetic refrigeration to demonstrate its potential. Indeed, it could be energetically efficient and with higher power densities. This work aims to estimate the potential of magnetic refrigeration. Magnetism and thermodynamic, essential tools for our study, are developed in a case of magnetocaloric effect. With some care, we show that material characterizations are able to give consistence and relevant model. Magnetocaloric effect suffers of small temperature variations; therefore structures that increase the temperature span and give competitive system are studied. Finally numerical models are developed to optimize active magnetic regenerators, which are currently the most used. These models are used to calculate and design systems close to their optimum.La réfrigération magnétique est une alternative pertinente dans un contexte où les gaz réfrigérants sont soumis à des restrictions environnementales. Ces restrictions nécessitent l'évolution de la technologie actuelle ou bien l'émergence d'une nouvelle, d'où l'opportunité pour la réfrigération magnétique de prouver son potentiel. En effet, elle pourrait s'avérer énergiquement plus efficace et avec des densités de puissance supérieure. Ces travaux de thèse apportent des réponses sur le potentiel de la réfrigération magnétique. Dans cette logique, la thermodynamique et le magnétisme, outils indispensables à notre étude, sont développés dans le cas des matériaux à effet magnétocalorique. Puis, nous verrons que les caractérisations de ces derniers sont en mesure de fournir des modèles matériaux cohérents et réalistes, si des précautions sont prises. L'effet magnétocalorique étant limité en termes de variation de température, nous allons étudier différentes structures de réfrigération. Enfin, des modèles numériques sont développés pour permettre d'optimiser les structures à régénérations actives, qui sont les plus utilisées. Ces modèles doivent permettre de dimensionner des systèmes proches de leurs optimums