FM-AFM with a Hanging Fiber Probe for the Study of Liquid-Liquid Interfaces

Area of Science:

• Physics
• Materials Science
• Surface Science

Background:

• Atomic Force Microscopy (AFM) is a powerful tool for nanoscale imaging and force measurements.
• Studying liquid-liquid interfaces is crucial for understanding phenomena in various fields, including chemistry, biology, and materials science.
• Existing methods for probing liquid-liquid interfaces often face limitations in precision, stability, or applicability.

Purpose of the Study:

• To develop and validate a novel frequency modulation atomic force microscope (AFM) system for quantitative measurements at liquid-liquid interfaces.
• To demonstrate the capability of the developed AFM system for long-term monitoring and dynamic interfacial processes.
• To explore the potential of this AFM technique for studying complex fluid-fluid interfaces and enabling interface manipulation.

Main Methods:

• Manufacture and calibration of a specialized hanging fiber force probe using a quartz tuning fork.
• Utilizing frequency modulation AFM to perform local measurements at the interface between two immiscible liquids.
• Monitoring a poly-dimethylsiloxane-water interface over extended periods to assess measurement repeatability.

Main Results:

• The developed AFM system provides reliable and quantitative measurements at liquid-liquid interfaces.
• The system successfully monitored a poly-dimethylsiloxane-water moving interface for several hours with high repeatability.
• The evaporation of a water droplet in poly-dimethylsiloxane was observed, and its interfacial tension evolution and interface deformation were measured over time.

Conclusions:

• The frequency modulation AFM with a hanging fiber probe is a suitable tool for quantitative analysis of liquid-liquid interfaces.
• This technique offers a new pathway for studying dynamic processes, such as droplet evaporation, at fluid interfaces.
• The demonstrated capabilities open avenues for advanced interface manipulation and the investigation of complex fluid-fluid systems.