Figure 2.

Principles of interfacial characterizations. (a) Scheme of a Langmuir–Blodgett trough. The surfactant layer is deposited on the subphase (blue molecules). The moving barriers compress the interfacial layer, and a force sensor measures the surface pressure. (b) Setup of the drop tensiometer: a gas (air) bubble is generated inside an aqueous solution, and its shape is observed via a camera. The interface lateral profile derives from the balance between surface tension and buoyancy, from which the surface tension value can be obtained.²⁰