Elucidating the oscillation instability of sessile drops triggered by surface acoustic waves

Nicolas Chastrette (1, 2) , Michael Baudoin (3, 4) , Philippe Brunet (2) , Laurent Royon (5) , Régis Wunenburger (1)

1 DALEMBERT - Institut Jean Le Rond d'Alembert
2 MSC - Matière et Systèmes Complexes
3 AIMAN-FILMS - IEMN - Acoustique Impulsionnelle & Magnéto-Acoustique Non linéaire - Fluides, Interfaces Liquides & Micro-Systèmes - IEMN
4 IUF - Institut universitaire de France
5 LIED (UMR_8236) - Laboratoire Interdisciplinaire des Energies de Demain

The oscillation instability of sessile drops is ubiquitous in surface acoustic wave (SAW) -powered digital microfluidics. Yet the physics underlying these phenomena has not been elucidated owing to the complex interplay between hydrodynamics, acoustics, and capillarity. We decipher the instability by combining high-speed imaging of the droplet surface vibration with inner acoustic pressure measurements. We rationalize the observed behavior with a model inspired from optomechanics, which couples an intracavity acoustic mode excited by the SAW to a surface deformation eigenmode through amplitude modulation and delayed radiation pressure feedback

Domaines: Mécanique des fluides [physics.class-ph]; Acoustique [physics.class-ph]; Micro et nanotechnologies/Microélectronique

Nicolas Chastrette, Michael Baudoin, Philippe Brunet, Laurent Royon, Régis Wunenburger. Elucidating the oscillation instability of sessile drops triggered by surface acoustic waves. Physical Review Fluids, 2022, 7 (12), pp.124201. ⟨10.1103/PhysRevFluids.7.124201⟩. ⟨hal-03885908v2⟩