Centro-symmetric technique for measuring shear modulus, viscosity, and surface tension of spread monolayers

B. M. Abraham*, K. Miyano, S. Q. Xu, J. B. Ketterson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

We have constructed an apparatus which enables one to measure, simultaneously, the shear modulus, the viscosity, and the surface pressure of a monomolecular film on water under a hydrostatic compression. It is particularly suitable for measurements of the static shear modulus of insoluble monolayers. A capillary wave generator/detector system was also incorporated to determine the surface pressure. The trough is a Teflon cup 12.7 cm (5.4 in.) in inner diameter with sloping interior sides. As the cup is raised, while maintaining the water elevation fixed, the film is uniformly compressed. A rotor suspended at the center from a fine torsion fiber is used to measure the mechanical properties (surface viscosity and/or surface shear modulus). To measure the quasistatic shear properties, the cup is rotated through a small angle and the residual deflection of the rotor determined. Dynamic shear response is probed by studying transient torsional oscillations following a sudden angular displacement of the torsion fiber. There are no barrier seals and circular symmetry is maintained at all times. The apparatus has a resolution of 5×10-4 surface poise of shear viscosity and 1×10-4 dyn/cm of static shear modulus.

Original languageEnglish (US)
Pages (from-to)213-219
Number of pages7
JournalReview of Scientific Instruments
Volume54
Issue number2
DOIs
StatePublished - Dec 1 1983

ASJC Scopus subject areas

  • Instrumentation

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