Spreading of liquid drops on Agar gels
Laboratoire Matière et Systèmes Complexes (MSC), UMR 7057, CNRS & Université Paris Diderot, Bât. Condorcet CC7056, 75205 Paris Cedex 13, France
Corresponding author: email@example.com
We study the spreading of pure water drops or water drops with surfactine (surfactant produced by bacteria Bacillus Subtilis) on gels (Agar/Water gel). We find that, surprisingly, the drops do not spread indefinitely, but remain in a state of partial wetting. Eventually the liquid diffuses into the gel on a time scale short with respect to evaporation times. The drops containing surfactant show a complex dynamics: at first the spreading velocity decreases, until the front stops and starts receding at about constant velocity. Concurrently, a second front detaches from the rim of the drop if the agar concentration is sufficiently low, and continues to move outwards.
© EDP Sciences, Springer-Verlag, 2009