Measurement of the thickness of thin foam films by laser interferometry: a review

Foams are involved in many industrial processes, including foods and beverages, fire fighting, subsoil environmental remediation and enhanced oil recovery. In these applications, foam stability and dynamics depend on the permeability of the thin liquid films to gases. An important parameter in the description of the foam permeability is the thickness of the thin liquid films. The foam film permeability is can be measured using (laser) light interferometry. In this paper, we survey the principles of this technique and compute the expressions for the thickness for a free standing foam film. The foam film is consists of five layers: a core aqueous layer with two surfactant monolayers, each consisting of consisting of hydrocarbon tails and polar head-groups sub-layers. from its reflection intensity coefficient Ir for perpendicularly incident light.

Keywords:

foam film , thickness , interferometry , intensity