The medical community has expressed a need for flexible medical instruments. Hence, this work investigates the possibility to use "flexible fluidic actuators" to develop such flexible instruments. These actuators are driven by fluid, i.e. gas or liquid, and present a flexible structure, i.e. an elastically deformable and/or inflatable structure. Different aspects of the study of these actuators have been tackled in the present work: • A literature review of these actuators has been established. It has allowed to identify the different types of motion that these actuators can develop as well as the design principles underlying. This review can help to develop flexible instruments based on flexible fluidic actuators. • A test bench has been developed to characterize the flexible fluidic actuators. • A interesting measuring concept has been implemented and experimentally validated on a specific flexible fluidic actuator (the "Pneumatic Balloon Actuator", PBA). Ac- cording to this principle, the measurements of the pressure and of the volume of fluid supplied to the actuator allow to determine the displacement of the actuator and the force it develops. This means being able to determine the displacement of a flexible fluidic actuator and the force it develops without using a displacement sensor or a force sensor. This principle is interesting for medical applications inside the human body, for which measuring the force applied by the organs to the surgical tools remains a problem. The study of this principle paves the way for a lot of future works such as the implemen- tation and the testing of this principle on more complex structures or in a control loop in order to control the displacement of the actuator (or the force it develops) without using a displacement or a force sensor. • A 2D-model of the PBA has been established and has helped to better understand the physics underlying the behaviour of this actuator. • A miniaturization work has been performed on a particular kind of flexible fluidic actu- ator: the Pleated Pneumatic Artificial Muscle (PPAM). This miniaturization study has been made on this type of actuator because, according to theoretical models, minia- turized PPAMs, whose dimensions are small enough to be inserted into MIS medical instruments, could be able to develop the forces required to allow the instruments to perform most surgical actions. The achieved miniaturized muscles have a design similar to that of the third generation PPAMs developed at the VUB and present a total length of about 90 mm and an outer diameter at rest of about 15 mm. One of the developed miniaturized PPAMs has been pressurized at p = 1 bar and it was able to develop a pulling force F = 100 N while producing a contraction of 4 %. Propositions have been made regarding a further miniaturization of the muscles.

Thesis (Ph. D.)--University of Tennessee, Knoxville, 2003. / Title from title page screen (viewed Sept. 26, 2003). Thesis advisor: Eric C. Drumm. Document formatted into pages (xx, 249 p. : ill. (some col.)). Vita. Includes bibliographical references.

Thesis (M.S.)--Mississippi State University. Department of Mechanical Engineering. / Title from title screen. Includes bibliographical references.

Inorganic material based electronics and photonics on unconventional substrates have shown tremendous unprecedented applications, especially in areas that traditional wafer based electronics and photonics are unable to cover. These areas range from flexible and conformal consumer products to biocompatible medical devices. This thesis presents the research on single crystal silicon nanomembrane photonics on different substrates, especially flexible substrates. A transfer method has been developed to transfer silicon nanomembrane defect-freely onto glass and flexible polyimide substrates. Using this method, intricate single crystal silicon nanomembrane device, such as photonic crystal microcavity, has been transferred onto flexible substrates. To test the device, subwavelength grating couplers are designed and implemented to couple light in and out of the transferred waveguides with high coupling efficiency. The cavity shows a quality factor ~ 9000 with water cladding and ~30000 with glycerol cladding, which is comparable to the same cavity demonstrated on silicon-on-insulator platform, indicating the high quality of the transferred silicon nanomembrane. The device could be bended to a radius less than 15 mm. The experiments show that the resonant wavelength shifts to longer wavelength under tensile stress, while it shifts to shorter wavelength under compressive stress. The sensitivity of the cavity is ~70 nm/RIU, which is independent of bending radius. This demonstration opens vast possibilities for a whole new range of high performance, light-weight and conformal silicon photonic devices. The techniques and devices (e.g. wafer bonding, stamp printing, subwavelength grating couplers, and modulator) generated in the research can also be beneficial for other research fields. / text

No description available.

Thesis (Master)--İzmir Institute of Technology, İzmir,2003 / Includes bibliographical references (leaves.195-202).

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 173-179). Also available in electronic version. Access restricted to campus users.

Zugl.: Aachen, Techn. Hochsch., Diss., 2008.

Un des freins majeurs au développement de la manipulation d'objet avec une main robotisée est sans aucun doute leur fragilité. C'est l'une des raisons pour laquelle un système bras-main anthropomorphe, extrêmement robuste, est développé au centre de robotique et de mécatronique de DLR. Le système est unique à la fois par sa complexité, utilisant 52 moteurs et plus de200 capteurs, ainsi que par ses capacités dynamiques. En effet, ce nouveau système a la particularité d'être mécaniquement flexible ce qui offre la possibilité de stocker de l'énergie à court terme et remplit ainsi deux fonctions essentielles pour un robot humanoïde: les impacts sont filtrés et les performances dynamiques sont augmentées.Dans cette thèse, on se concentre plus particulièrement sur la main. Elle dispose de 19 degrés de liberté dont chacun est actionné par deux tendons flexibles antagonistes. La rigidité des tendons étant non linéaire il est possible, tout comme peut le faire l'être humain, de co-contracter les <<muscles>> et donc d'ajuster la rigidité des doigts afin de s'adapter au mieux aux tâches à effectuer. Cependant, cette flexibilité entraine de nouveau défis de modélisation et de contrôle. L'état de l'art se concentre majoritairement sur le problème de la répartition des forces internes ou du contrôle d'articulation flexible mais peu de travaux considèrent les deux problèmes simultanément.Le travail présenté dans la première partie de la thèse se concentre sur la modélisation de la main et du poignet. Les problématiques spécifiques aux systèmes actionnés par des tendons, tels que les matrices de couplage et l'estimation du déplacement des articulations à partir du déplacement des tendons, sont étudiées.La seconde partie se concentre sur le contrôle d'articulations actionnées par des tendons flexibles antagonistes. Les problèmes de distribution des forces internes et de correction de la rigidité perçue par l'utilisateur sont présentés.Des approches de contrôle linéaire et non linéaire sont utilisées et des expériences sont réalisées pour comparer ces approches. En particulier, il est montré que le <<backstepping>>, une méthode de contrôle non linéaire peut être utilisée et permet d'obtenir le comportement d'impédance souhaité tout en garantissant la stabilité en boucle fermée. / One of the major limitations of object manipulation with a robotic hand is the fragility of the hardware.This is one of the motivations for developing the new anthropomorphic and extremely robust Hand Arm System at the robotics and mecatronics center of DLR.The system is unique in terms of complexity, with 52 motors and more than 200 sensors, and also in terms of dynamics.Indeed, the system is mechanically compliant, thus offers the possibility to store and release energy, thereby providing two essential functions: The impacts are filtered and the dynamics are enhanced.This thesis focuses on the hand. It has 19 degrees of freedom, each being actuated by two flexible antagonistic tendons. Because the stiffnes of the tendons is not linear, it is possible to adjust the mechanical stiffness of the joints, similar to the co-contraction of human muscles, in order to adapt to a task. However, the stiffness adjustability rises new challenges in modeling and control. The state of the art usually focuses on the problems of tendon-driven systems or flexible joint robots but seldomly both simultaneously.In the first part, the modeling of the hand and the wrist is conducted. Several problems specific to tendon-driven systems are presented, such as the coupling matrices and the joint position estimation based on the tendon displacement. The second part focuses on the control of a single joint actuated by two flexible tendons. The distribution of the tendon forces and the correction of the effective stiffness are reported. Linear and nonlinear approaches are used and multiple experiments are realised to compare them. The major result is that the backstepping, a nonlinear control method, can be used and provides the desired impedance behavior while guaranting closed-loop stability.

Les nanofils nitrures présentent des propriétés optoélectroniques extraordinaires et sont considérés comme des matériaux prometteurs pour des diodes électroluminescentes (LEDs), grâce à leur haute qualité cristalline, leurs surfaces non-polaires, leur bonne flexibilité mécanique, leur rapport d’aspect élevé, etc.Cette thèse adresse la croissance, la fabrication, les caractérisations optiques et électriques et la simulation optique des dispositifs à base de nanofils nitrures, avec un accent particulier sur les LEDs à nanofils.Premièrement, cette thèse présente la croissance par épitaxie en phase vapeur aux organométalliques de nanofils nitrures cœur-coquille auto-assemblés contenant des puits quantiques InGaN/GaN sur les facettes plan m avec différentes concentrations d’In. Puis est décrite la fabrication de LEDs utilisant ces nanofils suivant deux différentes stratégies d’intégration (intégrations planaires et verticales).L’intégration planaire est basée sur des nanofils uniques dispersés horizontalement. J’ai proposé une plateforme photonique intégrée composée d’une LED à nanofil, d’un guide d’onde optimisé et d’un photodétecteur à nanofil. J’ai également développé un système d’alignement des nanofils.L’intégration verticale a pour objectif la réalisation de LEDs flexibles reposant sur une assemblée de nanofils verticaux encapsulées dans des polymères. Je montre que ceci permet la fabrication de LEDs flexibles monochromatiques, bi-couleurs ou blanches.Les nanofils épitaxiés sur des matériaux 2D par épitaxie de van de Waals sont faciles à décoller de leur substrat natif. Avec cette motivation, dans la dernière partie de cette thèse, j’ai étudié la croissance organisée des nanofils GaN sur du graphène micro et nano-structuré utilisant l’épitaxie par jets moléculaires. / Nitride nanowires exhibit outstanding opto-electronic and mechanical properties and are considered as promising materials for light-emitting diodes (LEDs), thanks to their high crystalline quality, non-polar facets, good mechanical flexibility, high aspect ratio, etc.This Ph.D. thesis addresses the growth, the device fabrication, the optical and electrical characterizations and the optical simulations of III-nitride NW devices, with a special emphasis on the LED applications.First, this thesis presents the growth of m-plane InGaN/GaN quantum wells with different In concentrations in self-assembled core-shell nanowires by metal-organic chemical vapor deposition. Then, by using these nanowires, LED devices based on two different integration strategies (namely, in-plane and vertical integration) are demonstrated.The in-plane integration is based on the horizontally dispersed single nanowires. I have proposed a basic integrated photonic platform consisting of a nanowire LED, an optimized waveguide and a nanowire photodetector. I have also developed a nanowire alignment system using dielectrophoresis.The vertical integration targets the fabrication of flexible LEDs based on vertical nanowire arrays embedded in polymer membranes. Flexible monochromatic, bi-color, white LEDs have been demonstrated. Their thermal properties have been analyzed.The nanowires grown on 2D materials by van der Waals epitaxy are easy to be lifted-off from their native substrate, which should facilitate the fabrication of flexible nanowire devices. With this motivation, in the last part of this thesis, I have investigated the selective area growth of GaN NWs on micro- and nano- scale graphene by molecular beam epitaxy.