(ADSA-CSD): A Film Balance Technique for High Collapse Pressures

Langmuir 2008, 24, 10843-10850

10843

Axisymmetric Drop Shape Analysis-Constrained Sessile Drop (ADSA-CSD): A Film Balance Technique for High Collapse Pressures Sameh M. I. Saad,† Zdenka Policova,† Edgar J. Acosta,†,‡ and A. Wilhelm Neumann*,† Department of Mechanical and Industrial Engineering, UniVersity of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8, and Department of Chemical Engineering and Applied Chemistry, UniVersity of Toronto, 200 College Street, Toronto, Ontario, Canada M5S 3E5 ReceiVed May 30, 2008. ReVised Manuscript ReceiVed July 18, 2008 Collapse pressure of insoluble monolayers is a property determined from surface pressure/area isotherms. Such isotherms are commonly measured by a Langmuir film balance or a drop shape technique using a pendant drop constellation (ADSA-PD). Here, a different embodiment of a drop shape analysis, called axisymmetric drop shape analysis-constrained sessile drop (ADSA-CSD) is used as a film balance. It is shown that ADSA-CSD has certain advantages over conventional methods. The ability to measure very low surface tension values (e.g.,