Institut des
NanoSciences de Paris

Thesis Defense - Antoine Riaud - Wednesday, october 5, 2016 - 10 am

Amphithéâtre de l’IEMN - Avenue Poincaré - 59652 Villeneuve d’Ascq Cedex.

Antoine Riaud, team « Acoustics for nanosciences »

Study of the potentialities offered by the synthesis of complex surface acoustic wave fields : focus on fluid actuation and contactless manipulation.

(A) Principle of acoustical vortex contactless manipulation. The transducer (concentric circular electrodes) generates an acoustical vortex that traps the cells. (B) observation of the contactless manipulation of a buccal epithelium cell by an acoustical vortex. The vortex is generated by a flat microchip that fits easily under a microscope glass slide.

When surface acoustic waves radiate in nearby fluids, they trigger two nonlinear effects : acoustic radiation pressure and acoustic streaming. These two effects find numerous applications for digital microfluidics, contactless manipulation and biological cell sorting. Nonetheless, these systems face two limitations. On the one hand, each application requires a specific acoustic wave : there is no multifunction device so far. On the other hand, search for functionalities offered by simple surface acoustic waves (plane and focused waves) has failed to provide a selective tweezers able to manipulate individual particles or cells independently of their neighbors.

In the first part of this thesis, we develop two methods to synthesize complex surface acoustic wave fields. The first one employs an array of 32 interdigitated transducers controlled by the inverse filter to generate arbitrary fields on demand. The second method solves an inverse problem to design a holographic transducer to generate a predefined field. In the second part of the thesis, we use the inverse filter to (i) implement a multifunction lab on a chip and (ii) investigate the potentialities of a special type of surface acoustic waves called swirling surface waves. These waves enable a selective and contactless manipulation of microscopic objects. We conclude the thesis by integrating a holographic acoustical vortex transducer on a microscope in order to selectively manipulate biological cells without contact.


Olivier Bou Matar (Pr. Ecole Centrale Lille, IEMN - Lille), Thesis director
Jean-Louis Thomas (DR CNRS, INSP - Paris), Thesis co-director
Michaël Baudoin (Pr. Univ. Lille 1, IEMN - Lille), Superviser
Vincent Laude (DR CNRS, Femto ST - Besançon), Protractor
Henrik Bruus (Pr. DTU, Theoretical Microfluidics Lab - Danemark), Protractor
Charles Baroud (Pr. Ecole Polytechnique, Ladyx - Paris), Examinator
Pierre Thibault (Pr. UJF, LiPhy - Grenoble), Examinator .