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Non-wetting drops special dynamic
Keyvan Piroird, doctorant Crédits : Keyvan Piroird
This work, based on various experiments, tackles the dynamics of non-wetting drops in situations where gravity does not play a role, but other special forces are involved.
In the first part, we look at drops of liquid oxygen, which undergo Leidenfrost effect on a substrate at room temperature. These drops are also susceptible to the presence of a magnetic field. We study the force exerted by a magnet on those ultra-mobile drops and we show that they can be deflected, slowed down, deformed, captured and even accelerated by the presence of a magnetic field.
In the second part, we study a reverse situation, where the goal is to propel a non-wetting oil drop that is initially at rest. The drop is in a capillary tube and we show that a gradient in surfactant concentration leads to a spontaneous movement and allows the drop to escape from the tube. This experiment can be considered as a model situation of detergency. Non-trivial dynamics has been identified in this system : the movement is either continuous or intermittent, depending on the experimental parameters.