In a first part I will focus on the destabilisation of dilute
oil-in-water emulsion-based liquid sheets expanding in air. A sheet
results from the collision of a single tear on a small solid target ; it
disintegrates through the nucleation and growth of holes that perforate
the sheet. We have developed an optical technique that allows the
determination of the time and space-resolved thickness of the sheet to
gain a, understanding of the physical mechanisms f the perforation
events This bursting based-liquid sheet destabilization is at the origin
of emulsion-based anti-drift formulations are developed for agricultural
spray. In a second part, I will investigate freely expanding sheets
formed by ultra soft spherical gel beads of elastic but also liquid
droplets with various surface tensions, and simple viscoelastic fluids
(Maxwell fluids), produced by impacting them on a silicon wafer covered
with a thin layer of liquid nitrogen that suppresses viscous dissipation
by an inverse Leidenfrost effect. The experiments reveal a universal
behaviour of the impact dynamics with impact velocity, for both solids
and liquids, and even viscoelastic fluids, that we have rationalized