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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:<p>• 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.<p>• A test bench has been developed to characterize the flexible fluidic actuators.<p>• 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.<p>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.<p>• A 2D-model of the PBA has been established and has helped to better understand the physics underlying the behaviour of this actuator.<p>• 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 %.<p>Propositions have been made regarding a further miniaturization of the muscles. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

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Parameters governing separation control with sweeping jet actuators over a deflected flap are investigated experimentally on a generic "Multiple Flap Airfoil" (MFA). The model enables an extensive variation of geometric and aerodynamic parameters to aid the scaling of this novel flow control method to full-size applications.Sweeping jets exit from discrete, millimeter-scale nozzles distributed along the span and oscillate from side-to-side. The sweeping frequency is almost linearly dependent on the supplied flowrate per actuator. The measured thrust exerted by a row of actuators agrees well with vectored momentum calculations. Frequency and thrust measurements suggest that the jet velocity is limited to subsonic speeds and that any additional increase in flowrate causes internal choking of the flow.Neither the flowrate nor the momentum input is found to be a sole parameter governing the lift for varying distance between adjacent actuators. However, the product of the mass flow coefficient and the square root of the momentum coefficient collapses the lift onto a single curve regardless of the actuator spacing. Contrary to other actuation methods, separation control with sweeping jets does not exhibit any hysteresis with either momentum input or flap deflection. A comparison between sweeping and non-sweeping jets illustrates the superior control authority provided by sweeping jets. Surface flow visualization on the flap suggests the formation of counter-rotating pairs of streamwise vortices caused by the interaction of neighboring jets.The actuation intensity required to attach the flow increases with increasing downstream distance from the main element's trailing edge and increasing flap deflection. No obvious dependence of the ideal actuation location on actuator spacing, flap deflection, angle of attack, or actuation intensity is found within the tested range. Comparisons between experimental and numerical results reveal that the inviscid flow solution appears to be a suitable predictor for the effectively and efficiently obtainable lift of a given airfoil configuration. The flap size affects the achievable lift, the accompanying drag, and the required flap deflection and actuation intensity. By controlling separation, the range of achievable lift coefficients is doubled without significant penalty in drag even when considering a safety margin for the maximum applicable incidence.

De par leur importante compressibilité et leur fréquence de résonance extrêmement basse, les bulles sont des objets physiques singuliers du point de vue de l'acoustique et de la mécanique des fluides. En utilisant la technique de la microfluidique afin de créer des assemblées de bulles bi-dimensionnelles, que nous excitons acoustiquement, nous étudions à la fois leur influence sur une onde sonore et sur le fluide présent à leur voisinage.Les bulles étant des résonateurs sub-longueur d'onde, nous montrons qu'une assemblée de micro-bulles va interagir avec une onde sonore de longueur d'onde bien plus importante que la taille des bulles individuelles. En proposant une méthode pour extraire la contribution des bulles au signal acoustique, nous montrons que leur résonance suit une loi légèrement modifiée par rapport à celle proposée par Minnaert pour des bulles sphériques.Nous avons également exploré le potentiel de ce système expérimental comme méta-matériau pour l'acoustique. Nous observons en effet une baisse de la transmission d'une onde sonore à travers ce matériau et ce, dans une gamme de fréquence située au-delà de la fréquence de résonance.Cette baisse de la transmission peut être ajustée à la fois en fréquence et en amplitude ce qui fait de ce système un méta-matériau adaptable dont les caractéristiques peuvent être facilement ajustées. / Because of the important compressibility of gas bubbles in water, inducing a very low resonance frequency, one can find interest in studying bubbles from an acoustic and a fluid mechanics point of view. Using microfluidics techniques in order to produce assemblies of acoustically driven bi-dimensional bubbles, we are studying their influence on both acoustic waves and the surrounding fluid.Bubbles being sub-wavelength resonators, we show that a micro-bubbles assembly interacts with acoustical waves which wavelengths that are substantially bigger than the bubbles size. Developing a way to extract bubbles contribution to the acoustic signal, we show that their resonance frequency follows a law slightly different from the one Minnaert had found for spherical bubbles. The impact of this medium on the acoustical wave has been studied and we show that a decrease in the acoustical transmission happens in a range of frequencies above the resonance. This decrease can be adjusted in amplitude and in frequency making our system an easily tunable metameterial.Because of the strong response of bubbles induced by acoustical waves, the bubbles surface oscillates with a great amplitude in the surrounding fluid. This oscillation, working together with a coupling present between the bubbles, can drive a strong steady streaming in the fluid. Systems of several bubbles are studied, and a theory is proposed in order to predict the flow they induce. The interaction between the streaming phenomenon and an external flow is also presented, showing that exclusion zones can be present under certain circumstances in these systems. These exclusion zones can be useful in micro-fluidics in order to trap particles or chemicals.

Cette thèse s’inscrit dans le cadre applicatif général de l'analyse de cellules uniques. Afin d’améliorer la sélectivité du tri de cellules uniques, les équipes de FEMTO-ST proposent de contrôler en boucle fermée les trajectoires des cellules entemps réel pendant leur trajet dans les puces dédiées au tri. Dans ce cadre, mes travaux de thèse portent sur une méthode novatrice de détection en temps-réel de la position des cellules, directement intégrée aux puces et basée sur le principephysique de la mesure d'impédance.Lors du passage d’une cellule dans un microcanal, celle-ci vient modifier l’impédance mesurable entre des électrodes placées sur les bords du canal.Une méthode générique permettant de formuler les variations d'impédance en fonction de la position de la particule été proposée (modèledirect).Une méthode d'estimation de la position d’une particule reposant sur les mesures d’impédance a également été proposée (modèle inverse). Celle-ci exploite un filtre de Kalman étendu, permettant la fusion de données en provenance de plusieurspaires d'électrodes, et exploitant les informations disponibles telles que la distribution du bruit de mesure et le modèle dynamique de la particule.La validation de la méthode a été effectuée sur un banc expérimental qui a été développé lors de cette thèse et sur des simulations numériques.Ces travaux montrent la pertinence d’exploiter l’impédancemétrie pour construire un capteur de position de particules immergées dans un microcanal. Cette méthode est une alternative à l’utilisation de microscopes optiques et présente l’avantage d’une grande compacité. / This thesis is part of the general application framework of single cell analysis. In order to improve the selectivity of single cell sorting, FEMTO-ST teams propose to control in closed loop the trajectories of the cells in real time during their journey in the chips dedicated to sorting. In this context, my thesis work focuses on an innovative method for real-time detection of cell position, directly integrated into chips and based on the physical principle of impedance measurement.When a cell passes through a microchannel, it changes the measurable impedance between electrodes placed on the edges of the channel.A generic method for formulating impedance variations as a function of particle position has been proposed (direct model). A method for estimating the position of a particle based on impedance measurements has also been proposed (inverse model). It uses an extended Kalman filter, allowing data from several pairs ofelectrodes to be merged, and exploiting available information such as measurement noise distribution and particle dynamic model. The validation of the method was carried out on an experimental bench that was developed during this thesis and on numerical simulations.This work shows the relevance of using impedance measurement to build a position sensor for particles immersed in a microchannel. This method is an alternative to the use of optical microscopes and has the advantage of being very compact.

The biochip industry is characterized by high entry barrier in technology. For those firms in this industry, owning law-protected patents to lower the entry of the potential competitors is a key strategy in competition and competitive advantage. The firm¡¦s patent analysis not only discloses the firm¡¦s knowledge-base in biochip industry, it also impact other firms¡¦ innovation activity and technology development strategy in this industry. Previous patent analysis literatures usually focus on the performance implications of firm¡¦s patent number or the patent citation on the focal firm. However, the possible performance implications of patent contents between the focal firm and other firms in the biochip industry are relatively under-examined. From the network theory and resource-based theory viewpoint, this study tries to examine the performance implications by developing two patent indexes in patent content analysis, i.e., the patent status and the patent similarity. The results indicate that when the firm¡¦s patent status difference with each other is smaller, or the firm¡¦s patent similarity with each other is larger, the performance difference between the dyad firms will be smaller. In other words, the patent status and the patent similarity are solid indexes to predict the firm¡¦s performance difference in highly competitive and highly innovative industry, such as the biochip industry in this sample. The results provide referable value in addressing the performance issues of patent content analysis from network theory viewpoint. Moreover, it also provides complementary values in discussing market commonality and resource similarity in competitive issues.

Active flow control has been extensively explored in wind tunnel studies but successful in-flight implementation of an active flow control technology still remains a challenge. This thesis presents implementation of active flow control technology onboard a 33% scale Extra 330S ARF aircraft, wind tunnel studies and flight testing of fluidic actuators. The design and construction of the pulsed blowing system for stall suppression (LE actuator) and continuous blowing system for roll control (TE actuator) and pitch control have been presented. Full scale wind tunnel testing in 7̕ X 10 Oran W. Nicks low speed wind tunnel shows that the TE actuators are about 50% effective as the conventional ailerons. The LE actuator is found to be capable of suppressing stall from 12° to about 22°. Comparison of characteristics of Active elevator and conventional elevator in 3' X 4' low speed wind tunnel show that, the active elevator is as effective as of conventional elevator deflected at 5°. Flight tests show that TE actuators are able to control the aircraft in flight in banked turns. The measured roll rates in-flight support the wind tunnel test findings.

Enhanced heat transfer in electronic hardware by direct, small-scale actuation is investigated experimentally in two test bed configurations. The first configuration exploits the unsteady motions induced by a vibrating reed embedded within a heated duct (in contact with hardware that needs cooling) to enhance forced convection transport heat from the duct surfaces. The flow within the duct is either exclusively driven by the reed or, for higher heat flux, is augmented by an induced core flow. The time harmonic motion of the reed results in the regular shedding of vortical structures that interact with the inner surfaces in the absence and presence of a core flow. The second configuration focuses on the effects of small scale motions induced by a synthetic jet on heat transfer within an advanced heat sink. The synthetic jets emanate directly through the base of the heat sink and induce a recirculating flow between the fins, resulting in a lower thermal resistance than what is typically achieved with traditional fans. The unsteady flow characteristics in both configurations are investigated using particle image velocimetry (PIV). Of particular interest are the effects of small-scale motions and enhanced mixing on heat transfer compared to conventional time-invariant flows at similar or higher Reynolds numbers.

Earlier investigations of Combustion Powered Actuation (COMPACT) have demonstrated its utility for high-speed aerodynamic flow control. In this actuation approach, momentary (pulsed) actuation jets are produced by the ignition of a mixture of gaseous fuel and oxidizer within a cubic-centimeter scale chamber. The combustion process yields a high pressure burst and the ejection of a high-speed exhaust jet. The present thesis focuses on characterization of the effects of the internal flow (which is altered through the fuel and oxidizer inlet streams) on mixing and flame propagation within the actuator's combustion chamber, and thereby on actuator operation and performance. A test chamber with a grid of interchangeable air and fuel inlets was used for parametric investigations of the effects of inlet size and location. Actuator performance is characterized using dynamic pressure measurements and phase-locked Particle Image Velocimetry (PIV) of the combustor's internal flow field in the presence and absence of the active combustion process. Over the range tested, increased momentum of the air inlet jet for a given flow rate improves the actuator performance by increasing bulk velocities and small-scale motions within the chamber, thus yielding net higher flame propagation speed and subsequently faster pressure rise and higher pressure peak. Variation in inlet location that results in swirling flow within the chamber yields higher internal pressures while air flow over the spark ignition site yields lower internal pressures and erratic combustion. Improved refill and combustion processes will lead to enhanced performance combustor designs.