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SERIES OF EFFECTS INDUCED BY LIGHT ON LIQUID INTERFACES From photo-surfactant to photo-foam.
Eloïse Chevallier, doctorante - PhD student Crédits : ESPCI ParisTechA new system is described here, a photo-foam. A UV stimulus triggers a fast and localized destabilization of such a foam, still quite stable in ambient white light.
This photo foam is made of a solution of a photo-surfactant synthesized in the lab. The hydrophobic tail containing an azobenzene group is able to change its conformation reversibly depending on the light stimulus (UV or blue). First the two isomers of the surfactant (cis and trans) are shown to have a very different affinity to the air-water interface. Second, this work establishes that the light stimulus generates a flux of desorption of the surfactant from the interface. This molecular flux triggers a series of effects at different scales of the foam – air-water interface, soap film or network of soap films – in very different effects.