Instrument and methods for surface dilatational rheology measurements

Area of Science:

• Interfacial Science
• Rheology
• Surface Chemistry

Background:

• Interfacial tension and rheology are critical parameters in many scientific and industrial applications.
• Existing methods for measuring these properties have limitations, particularly for complex systems.

Purpose of the Study:

• To develop and describe a versatile instrument for comprehensive interfacial characterization.
• To measure interfacial tension and rheological parameters, including complex interfacial elasticity and surface elasticity/viscosity.

Main Methods:

• Combines axisymmetric drop shape analysis (for well-deformed drops) and capillary pressure tensiometry (for spherical drops).
• Utilizes a piezodriven system and a specialized interface unit for precise control of surface deformation (sine, square, triangle, sawtooth waveforms, constant rate).
• Ensures accurate synchronization between pressure measurement and surface control for real-time data processing and feedback control.

Main Results:

• The instrument is capable of measuring interfacial tension and rheological parameters (complex interfacial elasticity, surface elasticity and viscosity of Kelvin-Voigt and Maxwell models).
• Applicable to various surfactants (nonionic, ionic, proteins, polymers) and interfaces (air/water, oil/water, equal mass density liquids).
• Demonstrates precise control over surface deformation and real-time data processing.

Conclusions:

• The developed instrument offers a powerful tool for investigating interfacial rheological properties.
• It provides a unified platform for studying diverse surfactant effects on different types of interfaces.
• The precise control and real-time processing capabilities enhance the accuracy and scope of interfacial measurements.