Power Approaches for Implantable Medical Devices.

Implantable medical devices have been implemented to provide treatment and to assess in vivo physiological information in humans as well as animal models for medical diagnosis and prognosis, therapeutic applications and biological science studies. The advances of micro/nanotechnology dovetailed with novel biomaterials have further enhanced biocompatibility, sensitivity, longevity and reliability in newly-emerged low-cost and compact devices. Close-loop systems with both sensing and treatment functions have also been developed to provide point-of-care and personalized medicine. Nevertheless, one of the remaining challenges is whether power can be supplied sufficiently and continuously for the operation of the entire system. This issue is becoming more and more critical to the increasing need of power for wireless communication in implanted devices towards the future healthcare infrastructure, namely mobile health (m-Health). In this review paper, methodologies to transfer and harvest energy in implantable medical devices are introduced and discussed to highlight the uses and significances of various potential power sources

AlGaN/GaN heterostructures based MEMS resonators

En raison de leurs propriétés physiques et leur stabilité chimique, les semi-conducteurs à large bande interdite comme les nitrures d’éléments III doivent permettre de réaliser des dispositifs ayant une meilleure performance dans des environnements sévères. De plus, leur piézoélectricité et la possibilité de les utiliser en technologie monolithique sur silicium rendent cette filière particulièrement intéressante pour intégrer des microsystèmes électro-mécaniques MEMS avec des composants actifs HEMT dans la perspective de réalisation d’une nouvelle génération de capteurs. Le développement des MEMS en matériau nitrures nécessite une bonne connaissance et une bonne maîtrise des propriétés mécaniques des matériaux. La première partie de la thèse consiste donc en la caractérisation des modules d’Young et des contraintes résiduelles dans les couches minces de nitrures épitaxiées par épitaxie par jets moléculaires sur substrat silicium. Pour extraire ces paramètres mécaniques, nous avons mesuré et modélisé des micro-dispositifs de test constitués par des poutres bi-encastrées ou encastrées-libres de longueurs variées et des indicateurs mécaniques. La deuxième partie consiste en l’étude de la transduction électro-mécanique d’actionnement des résonateurs formés par une poutre intégrant une hétérostructure AlGaN/GaN. Les résonateurs sont actionnés par une diode Schottky intégrée sur la poutre. Les actionneurs ont été caractérisés en amplitude et en fréquence de vibration sous différentes conditions de polarisation par vibrométrie laser par effet Doppler. Une modélisation à été effectuée de façon analytique et de façon numérique par éléments finis en utilisant COMSOL multiphysique afin de comprendre le mécanisme d’actionnement et de mettre en évidence le rôle de l’hétérostructure AlGaN/GaN sur le fonctionnement de l’actionneur.Due to their physical properties and chemical stability, wide band gap semiconductors such as group III nitrides should enable devices with a better performance in harsh environments. In addition, their piezoelectricity and the possibility of monolithic integration on silicon, make this technology particularly attractive for integrating microelectromechanical systems (MEMS) with active devices such as HEMTs for the purpose of developing a new generation of sensors. The development of MEMS using nitride materials requires a good knowledge and understanding of the mechanical properties of materials. The first part of this thesis concerns the determination of the Young modulus and the residual stress in the thin films of nitrides grown by molecular beam epitaxy on silicon substrate. In order to extract these mechanical parameters, we measured and modelled test devices such as clamped-clamped beams, free-clamped beams with different lengths and mechanical indicators. The second part of the thesis consists in studying the piezoelectric actuation of MEMS resonators based on an AlGaN/GaN heterostructure. The resonators are actuated by a Schottky diode integrated onto the beam. The amplitude of the actuated resonator and the resonant frequency were measured under various bias conditions using Doppler laser vibrometry. We performed analytical modelling and finite element modelling using COMSOL Multiphysics® in order to unerstand the actuation mechanism and to evidence the role of the AlGaN/GaN heterostructure on the actuator operation

Power Approaches for Implantable Medical Devices.

Implantable medical devices have been implemented to provide treatment and to assess in vivo physiological information in humans as well as animal models for medical diagnosis and prognosis, therapeutic applications and biological science studies. The advances of micro/nanotechnology dovetailed with novel biomaterials have further enhanced biocompatibility, sensitivity, longevity and reliability in newly-emerged low-cost and compact devices. Close-loop systems with both sensing and treatment functions have also been developed to provide point-of-care and personalized medicine. Nevertheless, one of the remaining challenges is whether power can be supplied sufficiently and continuously for the operation of the entire system. This issue is becoming more and more critical to the increasing need of power for wireless communication in implanted devices towards the future healthcare infrastructure, namely mobile health (m-Health). In this review paper, methodologies to transfer and harvest energy in implantable medical devices are introduced and discussed to highlight the uses and significances of various potential power sources