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This thesis is about the action of acoustic waves on micrometer-sized bubbles excited at their resonance frequency. Indeed, bubbles can be considered as mechanical oscillators and the acoustic forces at the resonance, called Bjerknes forces, have non ordinary properties. Moreover, the bubbles interact between them by the emission of a secondary acoustic field, leading to their self-organization on a periodic mesh. Here, the bubbles are confined in microchannels, they are not spherical and rub against the walls. The experimental study of the acoustic forces (primary and secondary force) is thus preceded by the modeling of the bubble flow, linking the wall friction to the applied external forces. Several applications dedicated to the lab-on-a-chip are developped, with the size sorting, the controlled asymetric break-up, the automatic switching at a bifurcation and the manipulation of drops., Cette thèse traite de l'action des ondes acoustiques sur des bulles micrométriques excitées à leur fréquence de résonance. En effet, les bulles peuvent être considérées comme des oscillateurs mécaniques et les forces acoustiques à leur résonance, appelées forces de Bjerknes, ont des propriétés non triviales. De plus, les bulles interagissent entre elles par l'émission d'un champ secondaire, menant à leur auto-organisation sur un motif périodique. Ici, les bulles sont confinées dans des microcanaux, elles ne sont pas sphériques et frottent fortement sur les parois. L'étude expérimentale des forces acoustiques (primaire et secondaire) est alors précédée par la modélisation de l'écoulement des bulles, liant la friction sur les parois aux forces externes appliquées. Plusieurs applications aux laboratoires sur puce sont développées, dont le tri en taille, la division asymétrique contrôlée, l'aiguillage automatique à une bifurcation, et la manipulation de goutte.

National audience; We report on the primary and secondary acoustic forces exerted by ultrasonic standing waves on the motion of air bubbles in microfluidic devices. Bubbles are generated in a flow-focusing device and various sizes are obtained by adjusting the air to water plus surfactant flow rates. Ultrasounds are brought in channel through the resonance modes of a glass rod moulded near the channel. A CCD camera is used for optical measurements and to record bubble trajectories. Primary Bjerknes forces cause the very compressible bubbles entering the standing wave region to be deflected and attracted either towards the nodes or the anti-nodes, depending on the relative value of the standing wave frequency and the bubbles resonance. This acoustic force of a few hundreds of nanoNewtons in amplitude can be used to drive bubbles in a lab-on-a chip device, by a proper choice of the applied frequency, using moderate sound amplitudes of order of 10kPa. Secondary Bjerknes forces between two or more bubbles oscillating in the main pressure field are seen for large pressure amplitudes and/or when the bubbles come close enough. In this case, we observe superimposed to the primary force an additional effect due to the pressure field radiated from one pulsating bubble acting on the second, that makes them either to agglomerate, or to repulse. Size sorting experiments using this principle will be presented. Last, a new phenomenon has been evidenced for moderate incident field amplitudes that manifests by a self-organisation of the bubbles into a periodic lattice. In order to explain the existence of this “bubble crystal” that moves independently of the acoustic standing wave, existence parameters (size of the bubbles, acoustic amplitude, frequency) have been systematically investigated, leading to a new phenomenological and theoretical description based on bubble-bubble interactions mediated by acoustic waves.