KSV NIMA ISR FLIP interfacial shear rheometer

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Studying the stability of thin films that are formed at air–liquid or liquid–liquid interfaces is important for a range of applications such as pulmonary surfactants, and in industrial applications such as food, pharmaceutical, cosmetics and oil. Surface tension is usually sufficient to describe simple interfaces; however, when surfactants, particles or proteins are present, complex fluid–fluid systems can form which can have an interfacial viscoelastic response. Investigating these interfacial properties is necessary to determine how the system is behaving when the interface is deformed.

Interfacial rheology is a challenging field of research because the magnitude of forces in the interface is exceedingly small. Still, there are several different interfacial shear methods proposed, which include the rotating ring, bicone and magnetic needle methods. Primarily, the bicone method suffers from low sensitivity and thus limits the studies for macromolecular layers.

The KSV NIMA interfacial shear rheometer, ISR Flip, is a sensitive interfacial shear rheometer for measuring the interfacial shear elasticity and viscosity of a Langmuir film both at the air–liquid and liquid–liquid interface. It utilises a small magnetic probe that is moved with an oscillating magnetic field. The method reduces the inertia and should enhance the sensitivity of the probe compared to the rotating ring and bicone methods to enable the measurement of low molecular weight surface-active compounds.

Three automated measurement modes expand analysis: frequency sweep measurement provides information about the dominance of viscosity or elasticity; amplitude sweep measurement allows shear thinning or thickening to be detected; and single frequency measurement can be used to define the time dependency of viscoelastic properties. When combined with the ISR Flip high compression trough, the viscoelastic changes can be defined as a function of surface pressure. From the Langmuir isotherm different phases of the film can be seen, and viscoelastic properties are determined as a function of layer packing density.

ISR Flip is a sensitive, versatile tool for the analysis of surfactants and their influence on foam and emulsion stability, which helps to expand our understanding of interfacial layers.

For more information: https://www.biolinscientific.com/ksvnima/characterization-of-thin-films/isr-flip.